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Khang A, Meyer K, Sacks MS. An Inverse Modeling Approach to Estimate Three-Dimensional Aortic Valve Interstitial Cell Stress Fiber Force Levels. J Biomech Eng 2023; 145:121005. [PMID: 37715307 PMCID: PMC10680985 DOI: 10.1115/1.4063436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 08/18/2023] [Accepted: 08/21/2023] [Indexed: 09/17/2023]
Abstract
Within the aortic valve (AV) leaflet exists a population of interstitial cells (AVICs) that maintain the constituent tissues by extracellular matrix (ECM) secretion, degradation, and remodeling. AVICs can transition from a quiescent, fibroblast-like phenotype to an activated, myofibroblast phenotype in response to growth or disease. AVIC dysfunction has been implicated in AV disease processes, yet our understanding of AVIC function remains quite limited. A major characteristic of the AVIC phenotype is its contractile state, driven by contractile forces generated by the underlying stress fibers (SF). However, direct assessment of the AVIC SF contractile state and structure within physiologically mimicking three-dimensional environments remains technically challenging, as the size of single SFs are below the resolution of light microscopy. Therefore, in the present study, we developed a three-dimensional (3D) computational approach of AVICs embedded in 3D hydrogels to estimate their SF local orientations and contractile forces. One challenge with this approach is that AVICs will remodel the hydrogel, so that the gel moduli will vary spatially. We thus utilized our previous approach (Khang et al. 2023, "Estimation of Aortic Valve Interstitial Cell-Induced 3D Remodeling of Poly (Ethylene Glycol) Hydrogel Environments Using an Inverse Finite Element Approach," Acta Biomater., 160, pp. 123-133) to define local hydrogel mechanical properties. The AVIC SF model incorporated known cytosol and nucleus mechanical behaviors, with the cell membrane assumed to be perfectly bonded to the surrounding hydrogel. The AVIC SFs were first modeled as locally unidirectional hyperelastic fibers with a contractile force component. An adjoint-based inverse modeling approach was developed to estimate local SF orientation and contractile force. Substantial heterogeneity in SF force and orientations were observed, with the greatest levels of SF alignment and contractile forces occurring in AVIC protrusions. The addition of a dispersed SF orientation to the modeling approach did not substantially alter these findings. To the best of our knowledge, we report the first fully 3D computational contractile cell models which can predict locally varying stress fiber orientation and contractile force levels.
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Affiliation(s)
- Alex Khang
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences, Austin, TX 78712; Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229
| | - Kenneth Meyer
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences, Austin, TX 78712; Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229
| | - Michael S Sacks
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences, Austin, TX 78712; Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229
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Boehm CA, Donay C, Lubig A, Ruetten S, Sesa M, Fernández-Colino A, Reese S, Jockenhoevel S. Bio-Inspired Fiber Reinforcement for Aortic Valves: Scaffold Production Process and Characterization. Bioengineering (Basel) 2023; 10:1064. [PMID: 37760166 PMCID: PMC10525898 DOI: 10.3390/bioengineering10091064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 09/04/2023] [Accepted: 09/07/2023] [Indexed: 09/29/2023] Open
Abstract
The application of tissue-engineered heart valves in the high-pressure circulatory system is still challenging. One possible solution is the development of biohybrid scaffolds with textile reinforcement to achieve improved mechanical properties. In this article, we present a manufacturing process of bio-inspired fiber reinforcement for an aortic valve scaffold. The reinforcement structure consists of polyvinylidene difluoride monofilament fibers that are biomimetically arranged by a novel winding process. The fibers were embedded and fixated into electrospun polycarbonate urethane on a cylindrical collector. The scaffold was characterized by biaxial tensile strength, bending stiffness, burst pressure and hemodynamically in a mock circulation system. The produced fiber-reinforced scaffold showed adequate acute mechanical and hemodynamic properties. The transvalvular pressure gradient was 3.02 ± 0.26 mmHg with an effective orifice area of 2.12 ± 0.22 cm2. The valves sustained aortic conditions, fulfilling the ISO-5840 standards. The fiber-reinforced scaffold failed in a circumferential direction at a stress of 461.64 ± 58.87 N/m and a strain of 49.43 ± 7.53%. These values were above the levels of tested native heart valve tissue. Overall, we demonstrated a novel manufacturing approach to develop a fiber-reinforced biomimetic scaffold for aortic heart valve tissue engineering. The characterization showed that this approach is promising for an in situ valve replacement.
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Affiliation(s)
- Christian A. Boehm
- Department of Biohybrid & Medical Textiles (BioTex), AME Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Forckenbeckstr. 55, 52074 Aachen, Germany; (C.A.B.); (C.D.); (A.L.); (A.F.-C.)
| | - Christine Donay
- Department of Biohybrid & Medical Textiles (BioTex), AME Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Forckenbeckstr. 55, 52074 Aachen, Germany; (C.A.B.); (C.D.); (A.L.); (A.F.-C.)
| | - Andreas Lubig
- Department of Biohybrid & Medical Textiles (BioTex), AME Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Forckenbeckstr. 55, 52074 Aachen, Germany; (C.A.B.); (C.D.); (A.L.); (A.F.-C.)
| | - Stephan Ruetten
- Electron Microscopy Facility, University Hospital Aachen, Pauwelstr. 30, 52074 Aachen, Germany;
| | - Mahmoud Sesa
- Institute of Applied Mechanics, RWTH Aachen University, Mies-van-der-Rohe-Str. 1, 52074 Aachen, Germany; (M.S.); (S.R.)
| | - Alicia Fernández-Colino
- Department of Biohybrid & Medical Textiles (BioTex), AME Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Forckenbeckstr. 55, 52074 Aachen, Germany; (C.A.B.); (C.D.); (A.L.); (A.F.-C.)
| | - Stefanie Reese
- Institute of Applied Mechanics, RWTH Aachen University, Mies-van-der-Rohe-Str. 1, 52074 Aachen, Germany; (M.S.); (S.R.)
| | - Stefan Jockenhoevel
- Department of Biohybrid & Medical Textiles (BioTex), AME Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Forckenbeckstr. 55, 52074 Aachen, Germany; (C.A.B.); (C.D.); (A.L.); (A.F.-C.)
- Aachen-Maastricht Institute for Biobased Materials, Maastricht University at Chemelot Campus, Urmonderbaan 22, 6167 Geleen, The Netherlands
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3
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Khang A, Nguyen Q, Feng X, Howsmon DP, Sacks MS. Three-dimensional analysis of hydrogel-imbedded aortic valve interstitial cell shape and its relation to contractile behavior. Acta Biomater 2023; 163:194-209. [PMID: 35085795 PMCID: PMC9309197 DOI: 10.1016/j.actbio.2022.01.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 01/11/2022] [Accepted: 01/18/2022] [Indexed: 12/31/2022]
Abstract
Cell-shape is a conglomerate of mechanical, chemical, and biological mechanisms that reflects the cell biophysical state. In a specific application, we consider aortic valve interstitial cells (AVICs), which maintain the structure and function of aortic heart valve leaflets. Actomyosin stress fibers help determine AVIC shape and facilitate processes such as adhesion, contraction, and mechanosensing. However, detailed 3D assessment of stress fiber architecture and function is currently impractical. Herein, we assessed AVIC shape and contractile behaviors using hydrogel-based 3D traction force microscopy to intuit the orientation and behavior of AVIC stress fibers. We utilized spherical harmonics (SPHARM) to quantify AVIC geometries through three days of incubation, which demonstrated a shift from a spherical shape to forming substantial protrusions. Furthermore, we assessed changes in post-three day AVIC shape and contractile function within two testing regimes: (1) normal contractile level to relaxation (cytochalasin D), and (2) normal contractile level to hyper-contraction (endothelin-1). In both scenarios, AVICs underwent isovolumic shape changes and produced complex displacement fields within the hydrogel. AVICs were more elongated when relaxed and more spherical in hyper-contraction. Locally, AVIC protrusions contracted along their long axis and expanded in their circumferential direction, indicating predominately axially aligned stress fibers. Furthermore, the magnitude of protrusion displacements was correlated with protrusion length and approached a consistent displacement plateau at a similar critical length across all AVICs. This implied that stress fiber behavior is conserved, despite great variations in AVIC shapes. We anticipate our findings will bolster future investigations into AVIC stress fiber architecture and function. STATEMENT OF SIGNIFICANCE: Within the aortic valve there exists a population of aortic valve interstitial cells, which orchestrate the turnover, secretion, and remodeling of its extracellular matrix, maintaining tissue integrity and ultimately sustaining the proper mechanical function. Alterations in these processes are thought to underlie diseases of the aortic valve, which affect hundreds of thousands domestically and world-wide. Yet, to date, there are no non-surgical treatments for aortic heart valve disease, in part due to our limited understanding of the underlying disease processes. In the present study, we built upon our previous study to include a full 3D analysis of aortic valve interstitial cell shapes at differing contractile levels. The resulting detailed shape and deformation analysis provided insight into the underlying stress-fiber structures and mechanical behaviors.
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Affiliation(s)
- Alex Khang
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229, USA
| | - Quan Nguyen
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229, USA
| | - Xinzeng Feng
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229, USA
| | - Daniel P Howsmon
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229, USA
| | - Michael S Sacks
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229, USA.
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West TM, Howsmon DP, Massidda MW, Vo HN, Janobas AA, Baker AB, Sacks MS. The effects of strain history on aortic valve interstitial cell activation in a 3D hydrogel environment. APL Bioeng 2023; 7:026101. [PMID: 37035541 PMCID: PMC10076067 DOI: 10.1063/5.0138030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 03/13/2023] [Indexed: 04/05/2023] Open
Abstract
Aortic valves (AVs) undergo unique stretch histories that include high rates and magnitudes. While major differences in deformation patterns have been observed between normal and congenitally defective bicuspid aortic valves (BAVs), the relation to underlying mechanisms of rapid disease onset in BAV patients remains unknown. To evaluate how the variations in stretch history affect AV interstitial cell (AVIC) activation, high-throughput methods were developed to impart varied cyclical biaxial stretch histories into 3D poly(ethylene) glycol hydrogels seeded with AVICs for 48 h. Specifically, a physiologically mimicking stretch history was compared to two stretch histories with varied peak stretch and stretch rate. Post-conditioned AVICs were imaged for nuclear shape, alpha smooth muscle actin (αSMA) and vimentin (VMN) polymerization, and small mothers against decapentaplegic homologs 2 and 3 (SMAD 2/3) nuclear activity. The results indicated that bulk gel deformations were accurately transduced to the AVICs. Lower peak stretches lead to increased αSMA polymerization. In contrast, VMN polymerization was a function of stretch rate, with SMAD 2/3 nuclear localization and nuclear shape also trending toward stretch rate dependency. Lower than physiological levels of stretch rate led to higher SMAD 2/3 activity, higher VMN polymerization around the nucleus, and lower nuclear elongation. αSMA polymerization did not correlate with VMN polymerization, SMAD 2/3 activity, nor nuclear shape. These results suggest that a negative feedback loop may form between SMAD 2/3, VMN, and nuclear shape to maintain AVIC homeostatic nuclear deformations, which is dependent on stretch rate. These novel results suggest that AVIC mechanobiological responses are sensitive to stretch history and provide insight into the mechanisms of AV disease.
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Affiliation(s)
- Toni M. West
- James T. Willerson Center for Cardiovascular Modelling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, Austin, Texas 78711, USA
| | - Daniel P. Howsmon
- James T. Willerson Center for Cardiovascular Modelling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, Austin, Texas 78711, USA
| | - Miles W. Massidda
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78711, USA
| | | | | | - Aaron B. Baker
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78711, USA
| | - Michael S. Sacks
- James T. Willerson Center for Cardiovascular Modelling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, Austin, Texas 78711, USA
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Khang A, Steinman J, Tuscher R, Feng X, Sacks MS. Estimation of aortic valve interstitial cell-induced 3D remodeling of poly(ethylene glycol) hydrogel environments using an inverse finite element approach. Acta Biomater 2023; 160:123-133. [PMID: 36812955 DOI: 10.1016/j.actbio.2023.01.043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 01/16/2023] [Accepted: 01/19/2023] [Indexed: 02/24/2023]
Abstract
Aortic valve interstitial cells (AVICs) reside within the leaflet tissues of the aortic valve and maintain and remodel its extracellular matrix components. Part of this process is a result of AVIC contractility brought about by underlying stress fibers whose behaviors can change in various disease states. Currently, it is challenging to directly investigate AVIC contractile behaviors within dense leaflet tissues. As a result, optically clear poly (ethylene glycol) hydrogel matrices have been used to study AVIC contractility via 3D traction force microscopy (3DTFM). However, the local stiffness of the hydrogel is difficult to measure directly and is further confounded by the remodeling activity of the AVIC. Ambiguity in hydrogel mechanics can lead to large errors in computed cellular tractions. Herein, we developed an inverse computational approach to estimate AVIC-induced remodeling of the hydrogel material. The model was validated with test problems comprised of an experimentally measured AVIC geometry and prescribed modulus fields containing unmodified, stiffened, and degraded regions. The inverse model estimated the ground truth data sets with high accuracy. When applied to AVICs assessed via 3DTFM, the model estimated regions of significant stiffening and degradation in the vicinity of the AVIC. We observed that stiffening was largely localized at AVIC protrusions, likely a result of collagen deposition as confirmed by immunostaining. Degradation was more spatially uniform and present in regions further away from the AVIC, likely a result of enzymatic activity. Looking forward, this approach will allow for more accurate computation of AVIC contractile force levels. STATEMENT OF SIGNIFICANCE: The aortic valve (AV), positioned between the left ventricle and the aorta, prevents retrograde flow into the left ventricle. Within the AV tissues reside a resident population of aortic valve interstitial cells (AVICs) that replenish, restore, and remodel extracellular matrix components. Currently, it is technically challenging to directly investigate AVIC contractile behaviors within the dense leaflet tissues. As a result, optically clear hydrogels have been used to study AVIC contractility through means of 3D traction force microscopy. Herein, we developed a method to estimate AVIC-induced remodeling of PEG hydrogels. This method was able to accurately estimate regions of significant stiffening and degradation induced by the AVIC and allows a deeper understanding of AVIC remodeling activity, which can differ in normal and disease conditions.
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Affiliation(s)
- Alex Khang
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229, USA
| | - John Steinman
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229, USA
| | - Robin Tuscher
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229, USA
| | - Xinzeng Feng
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229, USA
| | - Michael S Sacks
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, TX 78712-1229, USA.
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Natural Polymers in Heart Valve Tissue Engineering: Strategies, Advances and Challenges. Biomedicines 2022; 10:biomedicines10051095. [PMID: 35625830 PMCID: PMC9139175 DOI: 10.3390/biomedicines10051095] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 05/03/2022] [Accepted: 05/04/2022] [Indexed: 12/04/2022] Open
Abstract
In the history of biomedicine and biomedical devices, heart valve manufacturing techniques have undergone a spectacular evolution. However, important limitations in the development and use of these devices are known and heart valve tissue engineering has proven to be the solution to the problems faced by mechanical and prosthetic valves. The new generation of heart valves developed by tissue engineering has the ability to repair, reshape and regenerate cardiac tissue. Achieving a sustainable and functional tissue-engineered heart valve (TEHV) requires deep understanding of the complex interactions that occur among valve cells, the extracellular matrix (ECM) and the mechanical environment. Starting from this idea, the review presents a comprehensive overview related not only to the structural components of the heart valve, such as cells sources, potential materials and scaffolds fabrication, but also to the advances in the development of heart valve replacements. The focus of the review is on the recent achievements concerning the utilization of natural polymers (polysaccharides and proteins) in TEHV; thus, their extensive presentation is provided. In addition, the technological progresses in heart valve tissue engineering (HVTE) are shown, with several inherent challenges and limitations. The available strategies to design, validate and remodel heart valves are discussed in depth by a comparative analysis of in vitro, in vivo (pre-clinical models) and in situ (clinical translation) tissue engineering studies.
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Development of a bi-layered cryogenic electrospun polylactic acid scaffold to study calcific aortic valve disease in a 3D co-culture model. Acta Biomater 2022; 140:364-378. [PMID: 34839029 DOI: 10.1016/j.actbio.2021.11.030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 10/27/2021] [Accepted: 11/22/2021] [Indexed: 11/23/2022]
Abstract
Calcified aortic valve disease (CAVD) is the most prevalent valve disease in the elderly. Targeted pharmacological therapies are limited since the underlying mechanisms of CAVD are not well understood. Appropriate 3D in vitro models could potentially improve our knowledge of the disease. Here, we developed a 3D in vitro aortic heart valve model that resembles the morphology of the valvular extracellular matrix and mimics the mechanical and physiological behavior of the native aortic valve fibrosa and spongiosa. We employed cryogenic electrospinning to engineer a bi-layered cryogenic electrospun scaffold (BCES) with defined morphologies that allowed valvular endothelial cell (VEC) adherence and valvular interstitial cell (VIC) ingrowth into the scaffold. Using a self-designed cell culture insert allowed us to establish the valvular co-culture simultaneously by seeding VICs on one side and VECs on the other side of the electrospun scaffold. Proof-of-principle calcification studies were successfully performed using an established osteogenic culture protocol and the here designed 3D in vitro aortic heart valve model. STATEMENT OF SIGNIFICANCE: Three-dimensional (3D) electrospun scaffolds are widely used for soft tissue engineering since they mimic the morphology of the native extracellular matrix. Several studies have shown that cells behave more naturally on 3D materials than on the commonly used stiff two-dimensional (2D) cell culture substrates, which have no biological properties. As appropriate 3D models for the study of aortic valve diseases are limited, we developed a novel bi-layered 3D in vitro test system by using the versatile technique of cryogenic electrospinning in combination with the influence of different solvents to mimic the morphology, mechanical, and cellular distribution of a native aortic heart valve leaflet. This 3D in vitro model can be used to study valve biology and heart valve-impacting diseases such as calcification to elucidate therapeutic targets.
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Khang A, Lejeune E, Abbaspour A, Howsmon DP, Sacks MS. On the Three-Dimensional Correlation Between Myofibroblast Shape and Contraction. J Biomech Eng 2021; 143:094503. [PMID: 33876206 PMCID: PMC8299802 DOI: 10.1115/1.4050915] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 04/02/2021] [Indexed: 01/05/2023]
Abstract
Myofibroblasts are responsible for wound healing and tissue repair across all organ systems. In periods of growth and disease, myofibroblasts can undergo a phenotypic transition characterized by an increase in extracellular matrix (ECM) deposition rate, changes in various protein expression (e.g., alpha-smooth muscle actin (αSMA)), and elevated contractility. Cell shape is known to correlate closely with stress-fiber geometry and function and is thus a critical feature of cell biophysical state. However, the relationship between myofibroblast shape and contraction is complex, even as well in regards to steady-state contractile level (basal tonus). At present, the relationship between myofibroblast shape and basal tonus in three-dimensional (3D) environments is poorly understood. Herein, we utilize the aortic valve interstitial cell (AVIC) as a representative myofibroblast to investigate the relationship between basal tonus and overall cell shape. AVICs were embedded within 3D poly(ethylene glycol) (PEG) hydrogels containing degradable peptide crosslinkers, adhesive peptide sequences, and submicron fluorescent microspheres to track the local displacement field. We then developed a methodology to evaluate the correlation between overall AVIC shape and basal tonus induced contraction. We computed a volume averaged stretch tensor ⟨U⟩ for the volume occupied by the AVIC, which had three distinct eigenvalues (λ1,2,3=1.08,0.99, and 0.89), suggesting that AVIC shape is a result of anisotropic contraction. Furthermore, the direction of maximum contraction correlated closely with the longest axis of a bounding ellipsoid enclosing the AVIC. As gel-imbedded AVICs are known to be in a stable state by 3 days of incubation used herein, this finding suggests that the overall quiescent AVIC shape is driven by the underlying stress-fiber directional structure and potentially contraction level.
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Affiliation(s)
- Alex Khang
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX 78712; Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Emma Lejeune
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX 78712; Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712; Department of Mechanical Engineering, Boston University, Boston, MA 02215
| | - Ali Abbaspour
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX 78712; Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Daniel P. Howsmon
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX 78712; Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Michael S. Sacks
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX 78712; Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
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9
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Büttner P, Feistner L, Lurz P, Thiele H, Hutcheson JD, Schlotter F. Dissecting Calcific Aortic Valve Disease-The Role, Etiology, and Drivers of Valvular Fibrosis. Front Cardiovasc Med 2021; 8:660797. [PMID: 34041283 PMCID: PMC8143377 DOI: 10.3389/fcvm.2021.660797] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 03/08/2021] [Indexed: 12/15/2022] Open
Abstract
Calcific aortic valve disease (CAVD) is a highly prevalent and progressive disorder that ultimately causes gradual narrowing of the left ventricular outflow orifice with ensuing devastating hemodynamic effects on the heart. Calcific mineral accumulation is the hallmark pathology defining this process; however, fibrotic extracellular matrix (ECM) remodeling that leads to extensive deposition of fibrous connective tissue and distortion of the valvular microarchitecture similarly has major biomechanical and functional consequences for heart valve function. Significant advances have been made to unravel the complex mechanisms that govern these active, cell-mediated processes, yet the interplay between fibrosis and calcification and the individual contribution to progressive extracellular matrix stiffening require further clarification. Specifically, we discuss (1) the valvular biomechanics and layered ECM composition, (2) patterns in the cellular contribution, temporal onset, and risk factors for valvular fibrosis, (3) imaging valvular fibrosis, (4) biomechanical implications of valvular fibrosis, and (5) molecular mechanisms promoting fibrotic tissue remodeling and the possibility of reverse remodeling. This review explores our current understanding of the cellular and molecular drivers of fibrogenesis and the pathophysiological role of fibrosis in CAVD.
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Affiliation(s)
- Petra Büttner
- Department of Internal Medicine/Cardiology, Heart Center Leipzig at University of Leipzig, Leipzig, Germany
| | - Lukas Feistner
- Department of Internal Medicine/Cardiology, Heart Center Leipzig at University of Leipzig, Leipzig, Germany
| | - Philipp Lurz
- Department of Internal Medicine/Cardiology, Heart Center Leipzig at University of Leipzig, Leipzig, Germany
| | - Holger Thiele
- Department of Internal Medicine/Cardiology, Heart Center Leipzig at University of Leipzig, Leipzig, Germany
| | - Joshua D. Hutcheson
- Department of Biomedical Engineering, Florida International University, Miami, FL, United States
- Biomolecular Sciences Institute, Florida International University, Miami, FL, United States
| | - Florian Schlotter
- Department of Internal Medicine/Cardiology, Heart Center Leipzig at University of Leipzig, Leipzig, Germany
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Niazy N, Barth M, Selig JI, Feichtner S, Shakiba B, Candan A, Albert A, Preuß K, Lichtenberg A, Akhyari P. Degeneration of Aortic Valves in a Bioreactor System with Pulsatile Flow. Biomedicines 2021; 9:biomedicines9050462. [PMID: 33922670 PMCID: PMC8145810 DOI: 10.3390/biomedicines9050462] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 04/18/2021] [Accepted: 04/21/2021] [Indexed: 02/07/2023] Open
Abstract
Calcific aortic valve disease is the most common valvular heart disease in industrialized countries. Pulsatile pressure, sheer and bending stress promote initiation and progression of aortic valve degeneration. The aim of this work is to establish an ex vivo model to study the therein involved processes. Ovine aortic roots bearing aortic valve leaflets were cultivated in an elaborated bioreactor system with pulsatile flow, physiological temperature, and controlled pressure and pH values. Standard and pro-degenerative treatment were studied regarding the impact on morphology, calcification, and gene expression. In particular, differentiation, matrix remodeling, and degeneration were also compared to a static cultivation model. Bioreactor cultivation led to shrinking and thickening of the valve leaflets compared to native leaflets while gross morphology and the presence of valvular interstitial cells were preserved. Degenerative conditions induced considerable leaflet calcification. In comparison to static cultivation, collagen gene expression was stable under bioreactor cultivation, whereas expression of hypoxia-related markers was increased. Osteopontin gene expression was differentially altered compared to protein expression, indicating an enhanced protein turnover. The present ex vivo model is an adequate and effective system to analyze aortic valve degeneration under controlled physiological conditions without the need of additional growth factors.
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Affiliation(s)
- Naima Niazy
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Mareike Barth
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Jessica I. Selig
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Sabine Feichtner
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Babak Shakiba
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Asya Candan
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Alexander Albert
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
- Department of Cardiovascular Surgery, Klinikum Dortmund gGmbH, Beurhausstraße 40, 44137 Dortmund, Germany
| | - Karlheinz Preuß
- Faculty of Biotechnology, Bioprocessing, Modulation and Simulation, University of Applied Sciences Mannheim, Paul-Wittsack-Straße 10, 68163 Mannheim, Germany;
| | - Artur Lichtenberg
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
- Correspondence:
| | - Payam Akhyari
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
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11
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Nazir R, Bruyneel A, Carr C, Czernuszka J. Mechanical and Degradation Properties of Hybrid Scaffolds for Tissue Engineered Heart Valve (TEHV). J Funct Biomater 2021; 12:20. [PMID: 33803209 PMCID: PMC8006234 DOI: 10.3390/jfb12010020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 02/26/2021] [Accepted: 03/03/2021] [Indexed: 01/06/2023] Open
Abstract
In addition to biocompatibility, an ideal scaffold for the regeneration of valvular tissue should also replicate the natural heart valve extracellular matrix (ECM) in terms of biomechanical properties and structural stability. In our previous paper, we demonstrated the development of collagen type I and hyaluronic acid (HA)-based scaffolds with interlaced microstructure. Such hybrid scaffolds were found to be compatible with cardiosphere-derived cells (CDCs) to potentially regenerate the diseased aortic heart valve. This paper focused on the quantification of the effect of crosslinking density on the mechanical properties under dry and wet conditions as well as degradation resistance. Elastic moduli increased with increasing crosslinking densities, in the dry and wet state, for parent networks, whereas those of interlaced scaffolds were higher than either network alone. Compressive and storage moduli ranged from 35 ± 5 to 95 ± 5 kPa and 16 ± 2 kPa to 113 ± 6 kPa, respectively, in the dry state. Storage moduli, in the dry state, matched and exceeded those of human aortic valve leaflets (HAVL). Similarly, degradation resistance increased with increasing the crosslinking densities for collagen-only and HA-only scaffolds. Interlaced scaffolds showed partial degradation in the presence of either collagenase or hyaluronidase as compared to when exposed to both enzymes together. These results agree with our previous findings that interlaced scaffolds were composed of independent collagen and HA networks without crosslinking between them. Thus, collagen/HA interlaced scaffolds have the potential to fill in the niche for designing an ideal tissue engineered heart valve (TEHV).
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Affiliation(s)
- Rabia Nazir
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK;
- Interdisciplinary Research Centre in Biomedical Materials (IRCBM), COMSATS University Islamabad (CUI), Lahore Campus, Lahore 54000, Pakistan
| | - Arne Bruyneel
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK; (A.B.); (C.C.)
| | - Carolyn Carr
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK; (A.B.); (C.C.)
| | - Jan Czernuszka
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK;
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12
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Biology and Biomechanics of the Heart Valve Extracellular Matrix. J Cardiovasc Dev Dis 2020; 7:jcdd7040057. [PMID: 33339213 PMCID: PMC7765611 DOI: 10.3390/jcdd7040057] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 12/02/2020] [Accepted: 12/13/2020] [Indexed: 02/06/2023] Open
Abstract
Heart valves are dynamic structures that, in the average human, open and close over 100,000 times per day, and 3 × 109 times per lifetime to maintain unidirectional blood flow. Efficient, coordinated movement of the valve structures during the cardiac cycle is mediated by the intricate and sophisticated network of extracellular matrix (ECM) components that provide the necessary biomechanical properties to meet these mechanical demands. Organized in layers that accommodate passive functional movements of the valve leaflets, heart valve ECM is synthesized during embryonic development, and remodeled and maintained by resident cells throughout life. The failure of ECM organization compromises biomechanical function, and may lead to obstruction or leaking, which if left untreated can lead to heart failure. At present, effective treatment for heart valve dysfunction is limited and frequently ends with surgical repair or replacement, which comes with insuperable complications for many high-risk patients including aged and pediatric populations. Therefore, there is a critical need to fully appreciate the pathobiology of biomechanical valve failure in order to develop better, alternative therapies. To date, the majority of studies have focused on delineating valve disease mechanisms at the cellular level, namely the interstitial and endothelial lineages. However, less focus has been on the ECM, shown previously in other systems, to be a promising mechanism-inspired therapeutic target. Here, we highlight and review the biology and biomechanical contributions of key components of the heart valve ECM. Furthermore, we discuss how human diseases, including connective tissue disorders lead to aberrations in the abundance, organization and quality of these matrix proteins, resulting in instability of the valve infrastructure and gross functional impairment.
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13
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Chaparro D, Dargam V, Alvarez P, Yeung J, Saytashev I, Bustillo J, Loganathan A, Ramella-Roman J, Agarwal A, Hutcheson JD. A Method to Quantify Tensile Biaxial Properties of Mouse Aortic Valve Leaflets. J Biomech Eng 2020; 142:100801. [PMID: 32291440 DOI: 10.1115/1.4046921] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Indexed: 11/08/2022]
Abstract
Understanding aortic valve (AV) mechanics is crucial in elucidating both the mechanisms that drive the manifestation of valvular diseases as well as the development of treatment modalities that target these processes. Genetically modified mouse models have become the gold standard in assessing biological mechanistic influences of AV development and disease. However, very little is known about mouse aortic valve leaflet (MAVL) tensile properties due to their microscopic size (∼500 μm long and 45 μm thick) and the lack of proper mechanical testing modalities to assess uniaxial and biaxial tensile properties of the tissue. We developed a method in which the biaxial tensile properties of MAVL tissues can be assessed by adhering the tissues to a silicone rubber membrane utilizing dopamine as an adhesive. Applying equiaxial tensile loads on the tissue-membrane composite and tracking the engineering strains on the surface of the tissue resulted in the characteristic orthotropic response of AV tissues seen in human and porcine tissues. Our data suggest that the circumferential direction is stiffer than the radial direction (n = 6, P = 0.0006) in MAVL tissues. This method can be implemented in future studies involving longitudinal mechanical stimulation of genetically modified MAVL tissues bridging the gap between cellular biological mechanisms and valve mechanics in popular mouse models of valve disease.
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Affiliation(s)
- Daniel Chaparro
- Department of Biomedical Engineering, Florida International University, Miami, FL 33174
| | - Valentina Dargam
- Department of Biomedical Engineering, Florida International University, Miami, FL 33174
| | - Paulina Alvarez
- Department of Biomedical Engineering, Florida International University, Miami, FL 33174
| | - Jay Yeung
- Department of Biomedical Engineering, Florida International University, Miami, FL 33174
| | - Ilyas Saytashev
- Department of Biomedical Engineering, Florida International University, Miami, FL 33174
| | - Jenniffer Bustillo
- Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174
| | - Archana Loganathan
- Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174
| | - Jessica Ramella-Roman
- Department of Biomedical Engineering, Florida International University, Miami, FL 33174
| | - Arvind Agarwal
- Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174
| | - Joshua D Hutcheson
- Department of Biomedical Engineering, Florida International University, Miami, FL 33174; Biomolecular Sciences Institute, Florida International University, Miami, FL 33199
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14
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Li RL, Russ J, Paschalides C, Ferrari G, Waisman H, Kysar JW, Kalfa D. Mechanical considerations for polymeric heart valve development: Biomechanics, materials, design and manufacturing. Biomaterials 2019; 225:119493. [PMID: 31569017 PMCID: PMC6948849 DOI: 10.1016/j.biomaterials.2019.119493] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 08/21/2019] [Accepted: 09/11/2019] [Indexed: 01/12/2023]
Abstract
The native human heart valve leaflet contains a layered microstructure comprising a hierarchical arrangement of collagen, elastin, proteoglycans and various cell types. Here, we review the various experimental methods that have been employed to probe this intricate microstructure and which attempt to elucidate the mechanisms that govern the leaflet's mechanical properties. These methods include uniaxial, biaxial, and flexural tests, coupled with microstructural characterization techniques such as small angle X-ray scattering (SAXS), small angle light scattering (SALS), and polarized light microscopy. These experiments have revealed complex elastic and viscoelastic mechanisms that are highly directional and dependent upon loading conditions and biochemistry. Of all engineering materials, polymers and polymer-based composites are best able to mimic the tissue-level mechanical behavior of the native leaflet. This similarity to native tissue permits the fabrication of polymeric valves with physiological flow patterns, reducing the risk of thrombosis compared to mechanical valves and in some cases surpassing the in vivo durability of bioprosthetic valves. Earlier work on polymeric valves simply assumed the mechanical properties of the polymer material to be linear elastic, while more recent studies have considered the full hyperelastic stress-strain response. These material models have been incorporated into computational models for the optimization of valve geometry, with the goal of minimizing internal stresses and improving durability. The latter portion of this review recounts these developments in polymeric heart valves, with a focus on mechanical testing of polymers, valve geometry, and manufacturing methods.
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Affiliation(s)
- Richard L Li
- Department of Mechanical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, New York, NY, USA; Division of Cardiac, Thoracic and Vascular Surgery, Section of Pediatric and Congenital Cardiac Surgery, New-York Presbyterian - Morgan Stanley Children's Hospital, Columbia University Medical Center, New York, NY, USA
| | - Jonathan Russ
- Department of Civil Engineering and Engineering Mechanics, Fu Foundation School of Engineering and Applied Science, Columbia University, New York, NY, USA
| | - Costas Paschalides
- Department of Mechanical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, New York, NY, USA
| | - Giovanni Ferrari
- Department of Surgery and Biomedical Engineering, Columbia University Medical Center, New York, NY, USA
| | - Haim Waisman
- Department of Civil Engineering and Engineering Mechanics, Fu Foundation School of Engineering and Applied Science, Columbia University, New York, NY, USA
| | - Jeffrey W Kysar
- Department of Mechanical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, New York, NY, USA; Department of Otolaryngology - Head and Neck Surgery, Columbia University Medical Center, New York, NY, USA.
| | - David Kalfa
- Division of Cardiac, Thoracic and Vascular Surgery, Section of Pediatric and Congenital Cardiac Surgery, New-York Presbyterian - Morgan Stanley Children's Hospital, Columbia University Medical Center, New York, NY, USA.
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15
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Khang A, Gonzalez Rodriguez A, Schroeder ME, Sansom J, Lejeune E, Anseth KS, Sacks MS. Quantifying heart valve interstitial cell contractile state using highly tunable poly(ethylene glycol) hydrogels. Acta Biomater 2019; 96:354-367. [PMID: 31323351 PMCID: PMC6717677 DOI: 10.1016/j.actbio.2019.07.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 07/04/2019] [Accepted: 07/06/2019] [Indexed: 01/19/2023]
Abstract
Valve interstitial cells (VIC) are the primary cell type residing within heart valve tissues. In many valve pathologies, VICs become activated and will subsequently profoundly remodel the valve tissue extracellular matrix (ECM). A primary indicator of VIC activation is the upregulation of α-smooth muscle actin (αSMA) stress fibers, which in turn increase VIC contractility. Thus, contractile state reflects VIC activation and ECM biosynthesis levels. In general, cell contraction studies have largely utilized two-dimensional substrates, which are a vastly different micro mechanical environment than 3D native leaflet tissue. To address this limitation, hydrogels have been a popular choice for studying cells in a three-dimensional environment due to their tunable properties and optical transparency, which allows for direct cell visualization. In the present study, we extended the use of hydrogels to study the active contractile behavior of VICs. Aortic VICs (AVIC) were encapsulated within poly(ethylene glycol) (PEG) hydrogels and were subjected to flexural-deformation tests to assess the state of AVIC contraction. Using a finite element model of the experimental setup, we determined the effective shear modulus μ of the constructs. An increase in μ resulting from AVIC active contraction was observed. Results further indicated that AVIC contraction had a more pronounced effect on μ in softer gels (72 ± 21% increase in μ within 2.5 kPa gels) and was dependent upon the availability of adhesion sites (0.5-1 mM CRGDS). The transparency of the gel allowed us to image AVICs directly within the hydrogel, where we observed a time-dependent decrease in volume (time constant τ=3.04 min) when the AVICs were induced into a hypertensive state. Our results indicated that AVIC contraction was regulated by both the intrinsic (unseeded) gel stiffness and the CRGDS peptide concentrations. This finding suggests that AVIC contractile state can be profoundly modulated through their local micro environment using modifiable PEG gels in a 3D micromechanical-emulating environment. Moving forward, this approach has the potential to be used towards delineating normal and diseased VIC biomechanical properties using highly tunable PEG biomaterials. STATEMENT OF SIGNIFICANCE.
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Affiliation(s)
- Alex Khang
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 240 East 24th Street, Austin, TX 78712, United States
| | - Andrea Gonzalez Rodriguez
- Department of Chemical and Biological Engineering, University of Colorado at Boulder, 3415 Colorado Avenue, Boulder, CO 80309, United States
| | - Megan E Schroeder
- Department of Materials Science and Engineering, University of Colorado at Boulder, 3415 Colorado Avenue, Boulder, CO 80309, United States
| | - Jacob Sansom
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 240 East 24th Street, Austin, TX 78712, United States
| | - Emma Lejeune
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 240 East 24th Street, Austin, TX 78712, United States
| | - Kristi S Anseth
- Department of Chemical and Biological Engineering, University of Colorado at Boulder, 3415 Colorado Avenue, Boulder, CO 80309, United States; Department of Materials Science and Engineering, University of Colorado at Boulder, 3415 Colorado Avenue, Boulder, CO 80309, United States; Biofrontiers Institute, University of Colorado at Boulder, 3415 Colorado Avenue, Boulder, CO80309, United States
| | - Michael S Sacks
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 240 East 24th Street, Austin, TX 78712, United States.
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16
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Chen Q, Bruyneel A, Carr C, Czernuszka J. Trilayer scaffold with cardiosphere-derived cells for heart valve tissue engineering. J Biomed Mater Res B Appl Biomater 2019; 108:729-737. [PMID: 31184806 DOI: 10.1002/jbm.b.34427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 05/01/2019] [Accepted: 05/17/2019] [Indexed: 11/08/2022]
Abstract
Natural polymers collagen, glycosaminoglycans, and elastin are promising candidate materials for heart valve tissue engineering scaffolds. This work produced trilayer scaffolds that resembled the layered structures of the extracellular matrices of native heart valves. The scaffolds showed anisotropic bending moduli (in both dry and hydrated statuses) depending on the loading directions (lower in the With Curvature direction than in the Against Curvature direction), which mimicked the characteristic behavior of the native heart valves. The interactions between cardiosphere-derived cells and the scaffolds were characterized by multiphoton microscopy, and relatively similar cell distributions were observed on different layers (a cell density of 3,000-4,000 mm-3 and a migration depth of 0.3-0.4 mm). The trilayer scaffold has represented a forwarding step from the previous studies, in attempting to better replicate a native heart valve structurally, mechanically, and biologically.
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Affiliation(s)
- Qi Chen
- R&D.cn, Guangzhou International Bio-Island, Guangzhou, China.,Department of Materials, University of Oxford, Oxford, UK
| | - Arne Bruyneel
- Cardiovascular Institute, Stanford University, Stanford, California
| | - Carolyn Carr
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Jan Czernuszka
- Department of Materials, University of Oxford, Oxford, UK
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17
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Saidy NT, Wolf F, Bas O, Keijdener H, Hutmacher DW, Mela P, De-Juan-Pardo EM. Biologically Inspired Scaffolds for Heart Valve Tissue Engineering via Melt Electrowriting. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1900873. [PMID: 31058444 DOI: 10.1002/smll.201900873] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 04/14/2019] [Indexed: 06/09/2023]
Abstract
Heart valves are characterized to be highly flexible yet tough, and exhibit complex deformation characteristics such as nonlinearity, anisotropy, and viscoelasticity, which are, at best, only partially recapitulated in scaffolds for heart valve tissue engineering (HVTE). These biomechanical features are dictated by the structural properties and microarchitecture of the major tissue constituents, in particular collagen fibers. In this study, the unique capabilities of melt electrowriting (MEW) are exploited to create functional scaffolds with highly controlled fibrous microarchitectures mimicking the wavy nature of the collagen fibers and their load-dependent recruitment. Scaffolds with precisely-defined serpentine architectures reproduce the J-shaped strain stiffening, anisotropic and viscoelastic behavior of native heart valve leaflets, as demonstrated by quasistatic and dynamic mechanical characterization. They also support the growth of human vascular smooth muscle cells seeded both directly or encapsulated in fibrin, and promote the deposition of valvular extracellular matrix components. Finally, proof-of-principle MEW trileaflet valves display excellent acute hydrodynamic performance under aortic physiological conditions in a custom-made flow loop. The convergence of MEW and a biomimetic design approach enables a new paradigm for the manufacturing of scaffolds with highly controlled microarchitectures, biocompatibility, and stringent nonlinear and anisotropic mechanical properties required for HVTE.
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Affiliation(s)
- Navid T Saidy
- Centre in Regenerative Medicine, Institute of Health and Biomedical Innovation (IHBI), Queensland University of Technology (QUT), 60 Musk Avenue, Kelvin Grove, Brisbane, Queensland, 4059, Australia
- Department of Biohybrid & Medical Textiles (BioTex), AME-Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Forckenbeckstr. 55, 52074, Aachen, Germany
| | - Frederic Wolf
- Department of Biohybrid & Medical Textiles (BioTex), AME-Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Forckenbeckstr. 55, 52074, Aachen, Germany
| | - Onur Bas
- Centre in Regenerative Medicine, Institute of Health and Biomedical Innovation (IHBI), Queensland University of Technology (QUT), 60 Musk Avenue, Kelvin Grove, Brisbane, Queensland, 4059, Australia
- ARC ITTC in Additive Biomanufacturing, Queensland University of Technology, 60 Musk Avenue, Kelvin Grove, Brisbane, Queensland, 4059, Australia
| | - Hans Keijdener
- Department of Biohybrid & Medical Textiles (BioTex), AME-Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Forckenbeckstr. 55, 52074, Aachen, Germany
| | - Dietmar W Hutmacher
- Centre in Regenerative Medicine, Institute of Health and Biomedical Innovation (IHBI), Queensland University of Technology (QUT), 60 Musk Avenue, Kelvin Grove, Brisbane, Queensland, 4059, Australia
- ARC ITTC in Additive Biomanufacturing, Queensland University of Technology, 60 Musk Avenue, Kelvin Grove, Brisbane, Queensland, 4059, Australia
- Institute for Advanced Study, Technische Universität München, D-85748, Garching, Germany
| | - Petra Mela
- Department of Biohybrid & Medical Textiles (BioTex), AME-Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Forckenbeckstr. 55, 52074, Aachen, Germany
- Medical Materials and Medical Implant Design, Department of Mechanical Engineering, Technical University of Munich, Boltzmannstr. 15, 85748, Garching,
| | - Elena M De-Juan-Pardo
- Centre in Regenerative Medicine, Institute of Health and Biomedical Innovation (IHBI), Queensland University of Technology (QUT), 60 Musk Avenue, Kelvin Grove, Brisbane, Queensland, 4059, Australia
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18
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Evaluation of transcatheter heart valve biomaterials: Computational modeling using bovine and porcine pericardium. J Mech Behav Biomed Mater 2019; 97:159-170. [PMID: 31125889 DOI: 10.1016/j.jmbbm.2019.05.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 04/20/2019] [Accepted: 05/13/2019] [Indexed: 12/16/2022]
Abstract
OBJECTIVE The durability of bioprosthetic heart valve (BHV) devices, commonly made of bovine (BP) and porcine (PP) pericardium tissue, is partly limited by device calcification and tissue degeneration, which has been associated with pathological levels of mechanical stress. This study investigated the impacts of BP and PP tissues with different thicknesses and tissue mechanical properties in BHV applications. METHODS Second Harmonic Generation (SHG) imaging was employed to visualize the collagen fibers on each side of the pericardium. Structural constitutive modeling that incorporates collagen fiber distribution obtained from multiphoton microscopy for each tissue type were derived to characterize the corresponding biaxial mechanical testing data collected in a previous study. The models were verified through finite element (FE) simulations of the biaxial test and implemented in valve closing simulations. RESULTS Smooth side collagen fibers were found to correlate with the mechanical response. BHVs with adult (ABP) and calf (CBP) BP tissues had lower maximum principal stresses than those with PP and fetal (FBP) BP tissues. Collagen fiber orientation along the circumferential axis resulted in lower maximum principal stresses and more uniform and symmetric stress distributions throughout the valve. CONCLUSIONS The use of PP and FBP tissue resulted in higher peak stresses than ABP and CBP tissues in the given valve design. Additionally, ensuring collagen fiber orientation along the circumferential axis led to lower maximum stresses felt by the valve leaflets, which could also improve BHV durability.
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19
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Gonzalez Rodriguez A, Schroeder ME, Walker CJ, Anseth KS. FGF-2 inhibits contractile properties of valvular interstitial cell myofibroblasts encapsulated in 3D MMP-degradable hydrogels. APL Bioeng 2018; 2:046104. [PMID: 31069326 PMCID: PMC6481727 DOI: 10.1063/1.5042430] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 11/08/2018] [Indexed: 02/06/2023] Open
Abstract
Valvular interstitial cells (VICs) are responsible for the maintenance of the extracellular matrix in heart valve leaflets and, in response to injury, activate from a quiescent fibroblast to a wound healing myofibroblast phenotype. Under normal conditions, myofibroblast activation is transient, but the chronic presence of activated VICs can lead to valve diseases, such as fibrotic aortic valve stenosis, for which non-surgical treatments remain elusive. We monitored the porcine VIC response to exogenously delivered fibroblast growth factor 2 (FGF-2; 100 ng/ml), transforming growth factor beta 1 (TGF-β1; 5 ng/ml), or a combination of the two while cultured within 3D matrix metalloproteinase (MMP)-degradable 8-arm 40 kDa poly(ethylene glycol) hydrogels that mimic aspects of the aortic valve. Here, we aimed to investigate VIC myofibroblast activation and subsequent contraction or the reparative wound healing response. To this end, VIC morphology, proliferation, gene expression related to the myofibroblast phenotype [alpha smooth muscle actin (α-SMA) and connective tissue growth factor (CTGF)] and matrix remodeling [collagens (COL1A1 and COL3) and MMP1], and contraction assays were used to quantify the cell response. Treatment with FGF-2 resulted in increased cellular proliferation while reducing the myofibroblast phenotype, as seen by decreased expression of CTGF and α-SMA, and reduced contraction relative to untreated control, suggesting that FGF-2 encourages a reparative phenotype, even in the presence of TGF-β1. TGF-β1 treatment predictably led to an increased proportion of VICs exhibiting the myofibroblast phenotype, indicated by the presence of α-SMA, increased gene expression indicative of matrix remodeling, and bulk contraction of the hydrogels. Functional contraction assays and biomechanical analyses were performed on VIC encapsulated hydrogels and porcine aortic valve tissue explants to validate these findings.
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20
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D'Amore A, Luketich SK, Raffa GM, Olia S, Menallo G, Mazzola A, D'Accardi F, Grunberg T, Gu X, Pilato M, Kameneva MV, Badhwar V, Wagner WR. Heart valve scaffold fabrication: Bioinspired control of macro-scale morphology, mechanics and micro-structure. Biomaterials 2018; 150:25-37. [PMID: 29031049 PMCID: PMC5988585 DOI: 10.1016/j.biomaterials.2017.10.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 09/19/2017] [Accepted: 10/03/2017] [Indexed: 10/18/2022]
Abstract
Valvular heart disease is currently treated with mechanical valves, which benefit from longevity, but are burdened by chronic anticoagulation therapy, or with bioprosthetic valves, which have reduced thromboembolic risk, but limited durability. Tissue engineered heart valves have been proposed to resolve these issues by implanting a scaffold that is replaced by endogenous growth, leaving autologous, functional leaflets that would putatively eliminate the need for anticoagulation and avoid calcification. Despite the diversity in fabrication strategies and encouraging results in large animal models, control over engineered valve structure-function remains at best partial. This study aimed to overcome these limitations by introducing double component deposition (DCD), an electrodeposition technique that employs multi-phase electrodes to dictate valve macro and microstructure and resultant function. Results in this report demonstrate the capacity of the DCD method to simultaneously control scaffold macro-scale morphology, mechanics and microstructure while producing fully assembled stent-less multi-leaflet valves composed of microscopic fibers. DCD engineered valve characterization included: leaflet thickness, biaxial properties, bending properties, and quantitative structural analysis of multi-photon and scanning electron micrographs. Quasi-static ex-vivo valve coaptation testing and dynamic organ level functional assessment in a pressure pulse duplicating device demonstrated appropriate acute valve functionality.
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Affiliation(s)
- Antonio D'Amore
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Fondazione RiMED, Italy; Dipartimento innovazione industriale e digitale (DIIT), Università di Palermo, Italy
| | - Samuel K Luketich
- McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Giuseppe M Raffa
- Istituto mediterraneo trapianti e terapie ad alta specializzazione (ISMETT), UPMC, Italy
| | - Salim Olia
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Artificial Heart Program, University of Pittsburgh Medical Center, Pittsburgh, PA, USA
| | - Giorgio Menallo
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Antonino Mazzola
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Dipartimento innovazione industriale e digitale (DIIT), Università di Palermo, Italy
| | - Flavio D'Accardi
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Dipartimento innovazione industriale e digitale (DIIT), Università di Palermo, Italy
| | - Tamir Grunberg
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; ORT Braude College of Engineering, Israel
| | - Xinzhu Gu
- Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Michele Pilato
- Istituto mediterraneo trapianti e terapie ad alta specializzazione (ISMETT), UPMC, Italy
| | - Marina V Kameneva
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Vinay Badhwar
- McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Dep. of Cardiovascular and Thoracic Surgery, West Virginia University, Morgantown, WV, USA
| | - William R Wagner
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, PA, USA.
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Nachlas ALY, Li S, Davis ME. Developing a Clinically Relevant Tissue Engineered Heart Valve-A Review of Current Approaches. Adv Healthc Mater 2017; 6. [PMID: 29171921 DOI: 10.1002/adhm.201700918] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/25/2017] [Indexed: 11/08/2022]
Abstract
Tissue engineered heart valves (TEHVs) have the potential to address the shortcomings of current implants through the combination of cells and bioactive biomaterials that promote growth and proper mechanical function in physiological conditions. The ideal TEHV should be anti-thrombogenic, biocompatible, durable, and resistant to calcification, and should exhibit a physiological hemodynamic profile. In addition, TEHVs may possess the capability to integrate and grow with somatic growth, eliminating the need for multiple surgeries children must undergo. Thus, this review assesses clinically available heart valve prostheses, outlines the design criteria for developing a heart valve, and evaluates three types of biomaterials (decellularized, natural, and synthetic) for tissue engineering heart valves. While significant progress has been made in biomaterials and fabrication techniques, a viable tissue engineered heart valve has yet to be translated into a clinical product. Thus, current strategies and future perspectives are also discussed to facilitate the development of new approaches and considerations for heart valve tissue engineering.
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Affiliation(s)
- Aline L. Y. Nachlas
- Wallace H Coulter Department of Biomedical Engineering Georgia Institute of Technology and Emory University Atlanta GA 30332 USA
| | - Siyi Li
- Wallace H Coulter Department of Biomedical Engineering Georgia Institute of Technology and Emory University Atlanta GA 30332 USA
| | - Michael E. Davis
- Wallace H Coulter Department of Biomedical Engineering Georgia Institute of Technology and Emory University Atlanta GA 30332 USA
- Children's Heart Research & Outcomes (HeRO) Center Children's Healthcare of Atlanta & Emory University Atlanta GA 30322 USA
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Caballero A, Sulejmani F, Martin C, Pham T, Sun W. Evaluation of transcatheter heart valve biomaterials: Biomechanical characterization of bovine and porcine pericardium. J Mech Behav Biomed Mater 2017; 75:486-494. [PMID: 28826102 PMCID: PMC5614867 DOI: 10.1016/j.jmbbm.2017.08.013] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/03/2017] [Accepted: 08/08/2017] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Bovine pericardium (BP) has been identified as a choice biomaterial for the development of surgical bioprosthetic heart valves (BHV) and transcatheter aortic valves (TAV). Porcine pericardium (PP) and younger BP have been suggested as candidates TAV leaflet biomaterials for smaller-profile devices due to their reduced thickness; however, their mechanical and structural properties remain to be fully characterized. This study characterized the material properties of chemically treated thick (PPK) and thin (PPN) PP, as well as fetal (FBP), calf (CBP) and adult (ABP) BP tissues in order to better understand their mechanical behavior. METHODS Planar biaxial testing and uniaxial failure testing methods were employed to quantify tissue mechanical responses and failure properties. Fiber characteristics were examined using histological analysis. RESULTS ABP and CBP tissues were significantly stiffer and stronger than the younger FBP tissues. Histological analysis revealed a significantly larger concentration of thin immature collagen fibers in the FBP tissues than in the ABP and CBP tissues. While PP tissues were thinnest, they were stiffer and less extensible than the BP tissues. CONCLUSIONS Due to comparable mechanical properties but significantly reduced thickness, CBP tissue may be a more suitable material for TAV manufacturing than ABP tissue. FBP tissue, despite its reduced thickness and higher flexibility, was weaker and should be studied in more detail. Although PP tissues are the thinnest, they were least extensible and failed at earlier strain than BP tissues. The differences between PP and BP tissues should be further investigated and suggest that they should not be used interchangeably in the manufacturing of TAV.
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Affiliation(s)
- Andrés Caballero
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Fatiesa Sulejmani
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Caitlin Martin
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Thuy Pham
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Wei Sun
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States.
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23
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Ayoub S, Lee CH, Driesbaugh KH, Anselmo W, Hughes CT, Ferrari G, Gorman RC, Gorman JH, Sacks MS. Regulation of valve interstitial cell homeostasis by mechanical deformation: implications for heart valve disease and surgical repair. J R Soc Interface 2017; 14:20170580. [PMID: 29046338 PMCID: PMC5665836 DOI: 10.1098/rsif.2017.0580] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 09/21/2017] [Indexed: 11/12/2022] Open
Abstract
Mechanical stress is one of the major aetiological factors underlying soft-tissue remodelling, especially for the mitral valve (MV). It has been hypothesized that altered MV tissue stress states lead to deviations from cellular homeostasis, resulting in subsequent cellular activation and extracellular matrix (ECM) remodelling. However, a quantitative link between alterations in the organ-level in vivo state and in vitro-based mechanobiology studies has yet to be made. We thus developed an integrated experimental-computational approach to elucidate MV tissue and interstitial cell responses to varying tissue strain levels. Comprehensive results at different length scales revealed that normal responses are observed only within a defined range of tissue deformations, whereas deformations outside of this range lead to hypo- and hyper-synthetic responses, evidenced by changes in α-smooth muscle actin, type I collagen, and other ECM and cell adhesion molecule regulation. We identified MV interstitial cell deformation as a key player in leaflet tissue homeostatic regulation and, as such, used it as the metric that makes the critical link between in vitro responses to simulated equivalent in vivo behaviour. Results indicated that cell responses have a delimited range of in vivo deformations that maintain a homeostatic response, suggesting that deviations from this range may lead to deleterious tissue remodelling and failure.
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Affiliation(s)
- Salma Ayoub
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences (ICES), Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
| | - Chung-Hao Lee
- School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA
| | - Kathryn H Driesbaugh
- Gorman Cardiovascular Research Group, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Wanda Anselmo
- Gorman Cardiovascular Research Group, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Connor T Hughes
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences (ICES), Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
| | - Giovanni Ferrari
- Gorman Cardiovascular Research Group, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Robert C Gorman
- Gorman Cardiovascular Research Group, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Joseph H Gorman
- Gorman Cardiovascular Research Group, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Michael S Sacks
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences (ICES), Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
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Sapp MC, Krishnamurthy VK, Puperi DS, Bhatnagar S, Fatora G, Mutyala N, Grande-Allen KJ. Differential cell-matrix responses in hypoxia-stimulated aortic versus mitral valves. J R Soc Interface 2016; 13:20160449. [PMID: 28003526 PMCID: PMC5221519 DOI: 10.1098/rsif.2016.0449] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 11/25/2016] [Indexed: 01/17/2023] Open
Abstract
Tissue oxygenation often plays a significant role in disease and is an essential design consideration for tissue engineering. Here, oxygen diffusion profiles of porcine aortic and mitral valve leaflets were determined using an oxygen diffusion chamber in conjunction with computational models. Results from these studies revealed the differences between aortic and mitral valve leaflet diffusion profiles and suggested that diffusion alone was insufficient for normal oxygen delivery in mitral valves. During fibrotic valve disease, leaflet thickening due to abnormal extracellular matrix is likely to reduce regional oxygen availability. To assess the impact of low oxygen levels on valve behaviour, whole leaflet organ cultures were created to induce leaflet hypoxia. These studies revealed a loss of layer stratification and elevated levels of hypoxia inducible factor 1-alpha in both aortic and mitral valve hypoxic groups. Mitral valves also exhibited altered expression of angiogenic factors in response to low oxygen environments when compared with normoxic groups. Hypoxia affected aortic and mitral valves differently, and mitral valves appeared to show a stenotic, rheumatic phenotype accompanied by significant cell death. These results indicate that hypoxia could be a factor in mid to late valve disease progression, especially with the reduction in chondromodulin-1 expression shown by hypoxic mitral valves.
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Affiliation(s)
- Matthew C Sapp
- Department of Bioengineering, Rice University, Houston, TX 77005, USA
| | | | - Daniel S Puperi
- Department of Bioengineering, Rice University, Houston, TX 77005, USA
| | - Saheba Bhatnagar
- Department of Bioengineering, Rice University, Houston, TX 77005, USA
| | - Gabrielle Fatora
- Department of Bioengineering, Rice University, Houston, TX 77005, USA
| | - Neelesh Mutyala
- Department of Bioengineering, Rice University, Houston, TX 77005, USA
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Deborde C, Simionescu DT, Wright C, Liao J, Sierad LN, Simionescu A. Stabilized Collagen and Elastin-Based Scaffolds for Mitral Valve Tissue Engineering. Tissue Eng Part A 2016; 22:1241-1251. [PMID: 27608885 DOI: 10.1089/ten.tea.2016.0032] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
There is a significant clinical need for new approaches to treatment of mitral valve disease. The aim of this study was to develop a tissue-engineered mitral valve scaffold possessing appropriate composition and structure to ensure ideal characteristics of mitral valves, such as large orifice, rapid opening and closure, maintenance of mitral annulus-papillary muscle continuity, in vivo biocompatibility and extended durability. An extracellular matrix-based scaffold was generated, based on the native porcine mitral valve as starting material and a technique for porcine cell removal without causing damage to the matrix components. To stabilize these structures and slow down their degradation, acellular scaffolds were treated with penta-galloyl glucose (PGG), a well-characterized polyphenol with high affinity for collagen and elastin. Biaxial mechanical testing presented similar characteristics for the PGG-treated scaffolds compared to fresh tissues. The extracellular matrix components, crucial for maintaining the valve shape and function, were well preserved in leaflets, and in chordae, as shown by their resistance to collagenase and elastin. When extracted with strong detergents, the PGG-treated scaffolds released a reduced amount of soluble matrix peptides, compared to untreated scaffolds; this correlated with diminished activation of fibroblasts seeded on scaffolds treated with PGG. Cell-seeded scaffolds conditioned for 5 weeks in a valve bioreactor showed good cell viability. Finally, rat subdermal implantation studies showed that PGG-treated mitral valve scaffolds were biocompatible, nonimmunogenic, noninflammatory, and noncalcifying. In conclusion, a biocompatible mitral valve scaffold was developed, which preserved the biochemical composition and structural integrity of the valve, essential for its highly dynamic mechanical demands, and its biologic durability.
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Affiliation(s)
- Christopher Deborde
- 1 Department of Bioengineering, Clemson University , Clemson, South Carolina
| | | | - Cristopher Wright
- 2 Department of Cardiothoracic Surgery, Greenville Memorial Hospital , Greenville, South Carolina
| | - Jun Liao
- 3 Department of Agricultural and Biological Engineeering, Mississippi state university , Starkville, Mississippi
| | - Leslie Neil Sierad
- 1 Department of Bioengineering, Clemson University , Clemson, South Carolina
| | - Agneta Simionescu
- 1 Department of Bioengineering, Clemson University , Clemson, South Carolina
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Tandon I, Razavi A, Ravishankar P, Walker A, Sturdivant NM, Lam NT, Wolchok JC, Balachandran K. Valve interstitial cell shape modulates cell contractility independent of cell phenotype. J Biomech 2016; 49:3289-3297. [DOI: 10.1016/j.jbiomech.2016.08.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 08/09/2016] [Accepted: 08/11/2016] [Indexed: 01/08/2023]
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Ayoub S, Ferrari G, Gorman RC, Gorman JH, Schoen FJ, Sacks MS. Heart Valve Biomechanics and Underlying Mechanobiology. Compr Physiol 2016; 6:1743-1780. [PMID: 27783858 PMCID: PMC5537387 DOI: 10.1002/cphy.c150048] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Heart valves control unidirectional blood flow within the heart during the cardiac cycle. They have a remarkable ability to withstand the demanding mechanical environment of the heart, achieving lifetime durability by processes involving the ongoing remodeling of the extracellular matrix. The focus of this review is on heart valve functional physiology, with insights into the link between disease-induced alterations in valve geometry, tissue stress, and the subsequent cell mechanobiological responses and tissue remodeling. We begin with an overview of the fundamentals of heart valve physiology and the characteristics and functions of valve interstitial cells (VICs). We then provide an overview of current experimental and computational approaches that connect VIC mechanobiological response to organ- and tissue-level deformations and improve our understanding of the underlying functional physiology of heart valves. We conclude with a summary of future trends and offer an outlook for the future of heart valve mechanobiology, specifically, multiscale modeling approaches, and the potential directions and possible challenges of research development. © 2016 American Physiological Society. Compr Physiol 6:1743-1780, 2016.
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Affiliation(s)
- Salma Ayoub
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, USA
| | - Giovanni Ferrari
- Gorman Cardiovascular Research Group, University of Pennsylvania, Philadelphia, USA
| | - Robert C. Gorman
- Gorman Cardiovascular Research Group, University of Pennsylvania, Philadelphia, USA
| | - Joseph H. Gorman
- Gorman Cardiovascular Research Group, University of Pennsylvania, Philadelphia, USA
| | - Frederick J. Schoen
- Department of Pathology, Brigham and Women’s Hospital, Boston, Massachusetts, USA
| | - Michael S. Sacks
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, USA
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Soares JS, Feaver KR, Zhang W, Kamensky D, Aggarwal A, Sacks MS. Biomechanical Behavior of Bioprosthetic Heart Valve Heterograft Tissues: Characterization, Simulation, and Performance. Cardiovasc Eng Technol 2016; 7:309-351. [PMID: 27507280 DOI: 10.1007/s13239-016-0276-8] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 07/13/2016] [Indexed: 12/11/2022]
Abstract
The use of replacement heart valves continues to grow due to the increased prevalence of valvular heart disease resulting from an ageing population. Since bioprosthetic heart valves (BHVs) continue to be the preferred replacement valve, there continues to be a strong need to develop better and more reliable BHVs through and improved the general understanding of BHV failure mechanisms. The major technological hurdle for the lifespan of the BHV implant continues to be the durability of the constituent leaflet biomaterials, which if improved can lead to substantial clinical impact. In order to develop improved solutions for BHV biomaterials, it is critical to have a better understanding of the inherent biomechanical behaviors of the leaflet biomaterials, including chemical treatment technologies, the impact of repetitive mechanical loading, and the inherent failure modes. This review seeks to provide a comprehensive overview of these issues, with a focus on developing insight on the mechanisms of BHV function and failure. Additionally, this review provides a detailed summary of the computational biomechanical simulations that have been used to inform and develop a higher level of understanding of BHV tissues and their failure modes. Collectively, this information should serve as a tool not only to infer reliable and dependable prosthesis function, but also to instigate and facilitate the design of future bioprosthetic valves and clinically impact cardiology.
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Affiliation(s)
- Joao S Soares
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA
| | - Kristen R Feaver
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA
| | - Will Zhang
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA
| | - David Kamensky
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA
| | - Ankush Aggarwal
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA
- College of Engineering, Swansea University, Bay Campus, Fabian Way, Swansea, SA1 8EN, UK
| | - Michael S Sacks
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX, 78712-1129, USA.
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Farrar EJ, Pramil V, Richards JM, Mosher CZ, Butcher JT. Valve interstitial cell tensional homeostasis directs calcification and extracellular matrix remodeling processes via RhoA signaling. Biomaterials 2016; 105:25-37. [PMID: 27497058 DOI: 10.1016/j.biomaterials.2016.07.034] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 07/26/2016] [Accepted: 07/27/2016] [Indexed: 01/04/2023]
Abstract
AIMS Valve interstitial cells are active and aggressive players in aortic valve calcification, but their dynamic mediation of mechanically-induced calcific remodeling is not well understood. The goal of this study was to elucidate the feedback loop between valve interstitial cell and calcification mechanics using a novel three-dimensional culture system that allows investigation of the active interplay between cells, disease, and the mechanical valve environment. METHODS & RESULTS We designed and characterized a novel bioreactor system for quantifying aortic valve interstitial cell contractility in 3-D hydrogels in control and osteogenic conditions over 14 days. Interstitial cells demonstrated a marked ability to exert contractile force on their environment and to align collagen fibers with the direction of tension. Osteogenic environment disrupted interstitial cell contractility and led to disorganization of the collagen matrix, concurrent with increased αSMA, TGF-β, Runx2 and calcific nodule formation. Interestingly, RhoA was also increased in osteogenic condition, pointing to an aberrant hyperactivation of valve interstitial cells mechanical activity in disease. This was confirmed by inhibition of RhoA experiments. Inhibition of RhoA concurrent with osteogenic treatment reduced pro-osteogenic signaling and calcific nodule formation. Time-course correlation analysis indicated a significant correlation between interstitial cell remodeling of collagen fibers and calcification events. CONCLUSIONS Interstitial cell contractility mediates internal stress state and organization of the aortic valve extracellular matrix. Osteogenesis disrupts interstitial cell mechanical phenotype and drives disorganization, nodule formation, and pro-calcific signaling via a RhoA-dependent mechanism.
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Affiliation(s)
- Emily J Farrar
- Department of Engineering, Messiah College, Mechanicsburg, PA, USA; School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Varsha Pramil
- Department of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA
| | | | - Christopher Z Mosher
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
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Vukicevic M, Puperi DS, Jane Grande-Allen K, Little SH. 3D Printed Modeling of the Mitral Valve for Catheter-Based Structural Interventions. Ann Biomed Eng 2016; 45:508-519. [DOI: 10.1007/s10439-016-1676-5] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 06/07/2016] [Indexed: 11/30/2022]
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31
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Brougham CM, Levingstone TJ, Jockenhoevel S, Flanagan TC, O'Brien FJ. Incorporation of fibrin into a collagen-glycosaminoglycan matrix results in a scaffold with improved mechanical properties and enhanced capacity to resist cell-mediated contraction. Acta Biomater 2015; 26:205-14. [PMID: 26297884 DOI: 10.1016/j.actbio.2015.08.022] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 08/11/2015] [Accepted: 08/18/2015] [Indexed: 12/21/2022]
Abstract
Fibrin has many uses as a tissue engineering scaffold, however many in vivo studies have shown a reduction in function resulting from the susceptibility of fibrin to cell-mediated contraction. The overall aim of the present study was to develop and characterise a reinforced natural scaffold using fibrin, collagen and glycosaminoglycan (FCG), and to examine the cell-mediated contraction of this scaffold in comparison to fibrin gels. Through the use of an injection loading technique, a homogenous FCG scaffold was developed. Mechanical testing showed a sixfold increase in compressive modulus and a thirtyfold increase in tensile modulus of fibrin when reinforced with a collagen-glycosaminoglycan backbone structure. Human vascular smooth muscle cells (vSMCs) were successfully incorporated into the FCG scaffold and demonstrated excellent viability over 7 days, while proliferation of these cells also increased significantly. VSMCs were seeded into both FCG and fibrin-only gels at the same seeding density for 7 days and while FCG scaffolds did not demonstrate a reduction in size, fibrin-only gels contracted to 10% of their original diameter. The FCG scaffold, which is composed of natural biomaterials, shows potential for use in applications where dimensional stability is crucial to the functionality of the tissue. STATEMENT OF SIGNIFICANCE Fibrin is a versatile scaffold for tissue engineering applications, but its weak mechanical properties leave it susceptible to cell-mediated contraction, meaning the dimensions of the fibrin construct will change over time. We have reinforced fibrin with a collagen glycosaminoglycan matrix and characterised the mechanical properties and bioactivity of the reinforced fibrin (FCG). This is the first scaffold manufactured from all naturally derived materials that resists cell-mediated contraction. In fact, over 7 days, the FCG scaffold fully resisted cell-mediated contraction of vascular smooth muscle cells. This FCG scaffold has many potential applications where natural scaffold materials can encourage regeneration.
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Affiliation(s)
- Claire M Brougham
- Tissue Engineering Research Group, Dept. of Anatomy, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland; School of Mechanical and Design Engineering, Dublin Institute of Technology, Bolton St, Dublin 1, Ireland; Advanced Materials and Bioengineering Research (AMBER) Centre, RCSI & TCD, Ireland
| | - Tanya J Levingstone
- Tissue Engineering Research Group, Dept. of Anatomy, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland; Advanced Materials and Bioengineering Research (AMBER) Centre, RCSI & TCD, Ireland; Trinity Centre for Bioengineering, Trinity College Dublin, Dublin 2, Ireland
| | - Stefan Jockenhoevel
- AME-Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany
| | - Thomas C Flanagan
- School of Medicine & Medical Science, University College Dublin, Dublin 4, Ireland
| | - Fergal J O'Brien
- Tissue Engineering Research Group, Dept. of Anatomy, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland; Advanced Materials and Bioengineering Research (AMBER) Centre, RCSI & TCD, Ireland; Trinity Centre for Bioengineering, Trinity College Dublin, Dublin 2, Ireland.
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Stephens EH, Connell PS, Fahrenholtz MM, Timek TA, Daughters GT, Kuo JJ, Patton AM, Ingels NB, Miller DC, Grande-Allen KJ. Heterogeneity of Mitral Leaflet Matrix Composition and Turnover Correlates with Regional Leaflet Strain. Cardiovasc Eng Technol 2015. [PMID: 26213589 DOI: 10.1007/s13239-015-0214-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
To determine how extracellular matrix and contractile valvular cells contribute to the heterogeneous motion and strain across the mitral valve (MV) during the cardiac cycle, regional MV material properties, matrix composition, matrix turnover, and cell phenotype were related to regional leaflet strain. Radiopaque markers were implanted into 14 sheep to delineate the septal (SEPT), lateral (LAT), and anterior and posterior commissural leaflets (ANT-C, POST-C). Videofluoroscopy imaging was used to calculate radial and circumferential strains. Mechanical properties were assessed using uniaxial tensile testing and micropipette aspiration. Matrix composition and cell phenotypes were immunohistochemically evaluated within each leaflet region [basal leaflet (BL), mid-leaflet (ML), and free edge]. SEPT-BL segments were stiffer and stronger than other valve tissues, while LAT segments demonstrated more extensibility and strain. Collagens I and III in SEPT were greater than in LAT, although LAT showed greater collagen turnover [matrix metalloprotease (MMP)-13, lysyl oxidase] and cell activation [smooth muscle alpha-actin (SMaA), and non-muscle myosin (NMM)]. MMP13, NMM, and SMaA were strongly correlated with each other, as well as with radial and circumferential strains in both SEPT and LAT. SMaA and MMP13 in POST-C ML was greater than ANT-C, corresponding to greater radial strains in POST-C. This work directly relates leaflet strain, material properties, and matrix turnover, and suggests a role for myofibroblasts in the heterogeneity of leaflet composition and strain. New approaches to MV repair techniques and ring design should preserve this normal coupling between leaflet composition and motion.
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Coupled Simulation of Heart Valves: Applications to Clinical Practice. Ann Biomed Eng 2015; 43:1626-39. [PMID: 26101029 DOI: 10.1007/s10439-015-1348-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 05/26/2015] [Indexed: 12/16/2022]
Abstract
The last few decades have seen great advances in the understanding of heart valves, and consequently, in the development of novel treatment modalities and surgical procedures for valves afflicted by disease. This is due in part to the profound advancements in computing technology and noninvasive medical imaging techniques that have made it possible to numerically model the complex heart valve systems characterized by distinct features at different length scales and various interacting processes. In this article, we highlight the importance of explicitly coupling these multiple scales and diverse processes to accurately simulate the true behavior of the heart valves, in health and disease. We examine some of the computational modeling studies that have a direct consequence on clinical practice.
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Lee CH, Carruthers CA, Ayoub S, Gorman RC, Gorman JH, Sacks MS. Quantification and simulation of layer-specific mitral valve interstitial cells deformation under physiological loading. J Theor Biol 2015; 373:26-39. [PMID: 25791285 PMCID: PMC4404233 DOI: 10.1016/j.jtbi.2015.03.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 02/12/2015] [Accepted: 03/03/2015] [Indexed: 01/15/2023]
Abstract
Within each of the four layers of mitral valve (MV) leaflet tissues there resides a heterogeneous population of interstitial cells that maintain the structural integrity of the MV tissue via protein biosynthesis and enzymatic degradation. There is increasing evidence that tissue stress-induced MV interstitial cell (MVIC) deformations can have deleterious effects on their biosynthetic states that are potentially related to the reduction of tissue-level maintenance and to subsequent organ-level failure. To better understand the interrelationships between tissue-level loading and cellular responses, we developed the following integrated experimental-computational approach. Since in vivo cellular deformations are not directly measurable, we quantified the in-situ layer-specific MVIC deformations for each of the four layers under a controlled biaxial tension loading device coupled to multi-photon microscopy. Next, we explored the interrelationship between the MVIC stiffness and deformation to layer-specific tissue mechanical and structural properties using a macro-micro finite element computational model. Experimental results indicated that the MVICs in the fibrosa and ventricularis layers deformed significantly more than those in the atrialis and spongiosa layers, reaching a nucleus aspect ratio of 3.3 under an estimated maximum physiological tension of 150N/m. The simulated MVIC moduli for the four layers were found to be all within a narrow range of 4.71-5.35kPa, suggesting that MVIC deformation is primarily controlled by each tissue layer's respective structure and mechanical behavior rather than the intrinsic MVIC stiffness. This novel result further suggests that while the MVICs may be phenotypically and biomechanically similar throughout the leaflet, they experience layer-specific mechanical stimulatory inputs due to distinct extracellular matrix architecture and mechanical behaviors of the four MV leaflet tissue layers. This also suggests that MVICs may behave in a layer-specific manner in response to mechanical stimuli in both normal and surgically modified MVs.
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Affiliation(s)
- Chung-Hao Lee
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences (ICES), Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, POB 5.236, 1 University Station C0200, Austin, TX 78712, USA
| | - Christopher A Carruthers
- Cardiac Rhythm Disease Management (CRDM) Clinical Specialist, Medtronic, Minneapolis, MN 55432, USA
| | - Salma Ayoub
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences (ICES), Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, POB 5.236, 1 University Station C0200, Austin, TX 78712, USA
| | - Robert C Gorman
- Gorman Cardiovascular Research Group, University of Pennsylvania, 3400 Civic Center Blvd, Philadelphia, PA 19104, USA
| | - Joseph H Gorman
- Gorman Cardiovascular Research Group, University of Pennsylvania, 3400 Civic Center Blvd, Philadelphia, PA 19104, USA
| | - Michael S Sacks
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences (ICES), Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, POB 5.236, 1 University Station C0200, Austin, TX 78712, USA.
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Bowler MA, Merryman WD. In vitro models of aortic valve calcification: solidifying a system. Cardiovasc Pathol 2015; 24:1-10. [PMID: 25249188 PMCID: PMC4268061 DOI: 10.1016/j.carpath.2014.08.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 07/21/2014] [Accepted: 08/07/2014] [Indexed: 12/21/2022] Open
Abstract
Calcific aortic valve disease (CAVD) affects 25% of people over 65, and the late-stage stenotic state can only be treated with total valve replacement, requiring 85,000 surgeries annually in the US alone (University of Maryland Medical Center, 2013, http://umm.edu/programs/services/heart-center-programs/cardiothoracic-surgery/valve-surgery/facts). As CAVD is an age-related disease, many of the affected patients are unable to undergo the open-chest surgery that is its only current cure. This challenge motivates the elucidation of the mechanisms involved in calcification, with the eventual goal of alternative preventative and therapeutic strategies. There is no sufficient animal model of CAVD, so we turn to potential in vitro models. In general, in vitro models have the advantages of shortened experiment time and better control over multiple variables compared to in vivo models. As with all models, the hypothesis being tested dictates the most important characteristics of the in vivo physiology to recapitulate. Here, we collate the relevant pieces of designing and evaluating aortic valve calcification so that investigators can more effectively draw significant conclusions from their results.
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Affiliation(s)
- Meghan A Bowler
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37212
| | - W David Merryman
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37212.
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Brazile B, Wang B, Wang G, Bertucci R, Prabhu R, Patnaik SS, Butler JR, Claude A, Brinkman-Ferguson E, Williams LN, Liao J. On the bending properties of porcine mitral, tricuspid, aortic, and pulmonary valve leaflets. J Long Term Eff Med Implants 2015; 25:41-53. [PMID: 25955006 PMCID: PMC6721960 DOI: 10.1615/jlongtermeffmedimplants.2015011741] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The atrioventricular valve leaflets (mitral and tricuspid) are different from the semilunar valve leaflets (aortic and pulmonary) in layered structure, ultrastructural constitution and organization, and leaflet thickness. These differences warrant a comparative look at the bending properties of the four types of leaflets. We found that the moment-curvature relationships in atrioventricular valves were stiffer than in semilunar valves, and the moment-curvature relationships of the left-side valve leaflets were stiffer than their morphological analog of the right side. These trends were supported by the moment-curvature curves and the flexural rigidity analysis (EI value decreased from mitral, tricuspid, aortic, to pulmonary leaflets). However, after taking away the geometric effect (moment of inertia I), the instantaneous effective bending modulus E showed a reversed trend. The overall trend of flexural rigidity (EI: mitral > tricuspid > aortic > pulmonary) might be correlated with the thickness variations among the four types of leaflets (thickness: mitral > tricuspid > aortic > pulmonary). The overall trend of the instantaneous effective bending modulus (E: mitral < tricuspid < aortic < pulmonary) might be correlated to the layered fibrous ultrastructures of the four types of leaflets, of which the fibers in mitral and tricuspid leaflets were less aligned, and the fibers in aortic and pulmonary leaflets were highly aligned. We also found that, for all types of leaflets, moment-curvature relationships are stiffer in against-curvature (AC) bending than in with-curvature bending (WC), which implies that leaflets tend to flex toward their natural curvature and comply with blood flow. Lastly, we observed that the leaflets were stiffer in circumferential bending compared with radial bending, likely reflecting the physiological motion of the leaflets, i.e., more bending moment and movement were experienced in radial direction than circumferential direction.
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Affiliation(s)
- Bryn Brazile
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Bo Wang
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Guangjun Wang
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Robbin Bertucci
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Raj Prabhu
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Sourav S. Patnaik
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - J. Ryan Butler
- Department of Clinical Sciences, College of Veterinary
Medicine, Mississippi State University, MS, 39762
| | - Andrew Claude
- Department of Clinical Sciences, College of Veterinary
Medicine, Mississippi State University, MS, 39762
| | - Erin Brinkman-Ferguson
- Department of Clinical Sciences, College of Veterinary
Medicine, Mississippi State University, MS, 39762
| | - Lakiesha N. Williams
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Jun Liao
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
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37
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Biomechanical properties of native and tissue engineered heart valve constructs. J Biomech 2014; 47:1949-63. [DOI: 10.1016/j.jbiomech.2013.09.023] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 09/09/2013] [Accepted: 09/10/2013] [Indexed: 11/18/2022]
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Masoumi N, Larson BL, Annabi N, Kharaziha M, Zamanian B, Shapero KS, Cubberley AT, Camci-Unal G, Manning KB, Mayer JE, Khademhosseini A. Electrospun PGS:PCL microfibers align human valvular interstitial cells and provide tunable scaffold anisotropy. Adv Healthc Mater 2014; 3:929-39. [PMID: 24453182 PMCID: PMC4053480 DOI: 10.1002/adhm.201300505] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 10/09/2013] [Indexed: 12/23/2022]
Abstract
Tissue engineered heart valves (TEHV) can be useful in the repair of congenital or acquired valvular diseases due to their potential for growth and remodeling. The development of biomimetic scaffolds is a major challenge in heart valve tissue engineering. One of the most important structural characteristics of mature heart valve leaflets is their intrinsic anisotropy, which is derived from the microstructure of aligned collagen fibers in the extracellular matrix (ECM). In the present study, a directional electrospinning technique is used to fabricate fibrous poly(glycerol sebacate):poly(caprolactone) (PGS:PCL) scaffolds containing aligned fibers, which resemble native heart valve leaflet ECM networks. In addition, the anisotropic mechanical characteristics of fabricated scaffolds are tuned by changing the ratio of PGS:PCL to mimic the native heart valve's mechanical properties. Primary human valvular interstitial cells (VICs) attach and align along the anisotropic axes of all PGS:PCL scaffolds with various mechanical properties. The cells are also biochemically active in producing heart-valve-associated collagen, vimentin, and smooth muscle actin as determined by gene expression. The fibrous PGS:PCL scaffolds seeded with human VICs mimick the structure and mechanical properties of native valve leaflet tissues and would potentially be suitable for the replacement of heart valves in diverse patient populations.
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Affiliation(s)
- Nafiseh Masoumi
- Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, Sate College, PA, USA. Center for Biomedical Engineering, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Harvard-MIT Division of Health Sciences and Technology Massachusetts Institute of Technology, 65 Landsdowne St., Cambridge, 02139 MA, USA. Department of Cardiac Surgery, Boston Children Hospital and Harvard Medical School 300 Longwood Ave, Boston, MA 02115, USA
| | - Benjamin L. Larson
- Harvard-MIT Division of Health Sciences and Technology and the David Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge, MA 02139, USA
| | - Nasim Annabi
- Center for Biomedical Engineering, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Harvard-MIT Division of Health Sciences and Technology Massachusetts Institute of Technology, 65 Landsdowne St., Cambridge, 02139 MA, USA. Wyss Institute for Biologically Inspired Engineering, Harvard University, 3 Blackfan Cir, Boston, MA 02115, USA
| | - Mahshid Kharaziha
- Center for Biomedical Engineering, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Harvard-MIT Division of Health Sciences and Technology Massachusetts Institute of Technology, 65 Landsdowne St., Cambridge, 02139 MA, USA
| | - Behnam Zamanian
- Center for Biomedical Engineering, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Harvard-MIT Division of Health Sciences and Technology Massachusetts Institute of Technology, 65 Landsdowne St., Cambridge, 02139 MA, USA
| | - Kayle S. Shapero
- Department of Cardiac Surgery, Boston Children Hospital and Harvard Medical School, 300 Longwood Ave, Boston, MA 02115, USA
| | - Alexander T. Cubberley
- Department of Cardiac Surgery, Boston Children Hospital and Harvard Medical School, 300 Longwood Ave, Boston, MA 02115, USA
| | - Gulden Camci-Unal
- Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, Sate College, PA, USA
| | - Keefe. B. Manning
- Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, Sate College, PA, USA
| | - John E. Mayer
- Department of Cardiac Surgery, Boston Children Hospital and Harvard Medical School, 300 Longwood Ave, Boston, MA 02115, USA
| | - Ali Khademhosseini
- Center for Biomedical Engineering, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Harvard-MIT Division of Health Sciences and Technology Massachusetts Institute of Technology, 65 Landsdowne St., Cambridge, 02139 MA, USA. Wyss Institute for Biologically Inspired Engineering, Harvard University, 3 Blackfan Cir, Boston, MA 02115, USA
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39
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Magin CM, Alge DL, Gould ST, Anseth KS. Clickable, photodegradable hydrogels to dynamically modulate valvular interstitial cell phenotype. Adv Healthc Mater 2014; 3:649-57. [PMID: 24459068 DOI: 10.1002/adhm.201300288] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 09/26/2013] [Indexed: 11/06/2022]
Abstract
Biophysical cues are widely recognized to influence cell phenotype. While this evidence was established using static substrates, there is growing interest in creating stimulus-responsive biomaterials that better recapitulate the dynamic extracellular matrix. Here, a clickable, photodegradable hydrogel substrate that allows the user to precisely control substrate elasticity and topography in situ is presented. The hydrogels are synthesized by reacting an 8-arm poly(ethylene glycol) alkyne with an azide-functionalized photodegradable crosslinker. The utility of this platform by exploiting its photoresponsive properties to modulate the phenotype of porcine aortic valvular interstitial cells (VICs) is demonstrated. First, VIC phenotype is monitored, in response to initial substratum modulus and static topographic cues. Higher modulus (E ≈ 15 kPa) substrates induce higher levels of activation (≈70% myofibroblasts) versus soft (E ≈ 3 kPa) substrates (≈20% myofibroblasts). Microtopographies that induce VIC alignment and elongation on low modulus substrates also stimulate activation. Finally, VIC phenotype is monitored in response to sequential in situ manipulations. The results illustrate that VIC activation on stiff surfaces (≈70% myofibroblasts) can be partially reversed by reducing surface modulus (≈30% myofibroblats) and subsequently re-activated by anisotropic topographies (≈60% myofibroblasts). Such dynamic substrates afford unique opportunities to decipher the complex role of matrix cues on the plasticity of VIC activation.
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Affiliation(s)
- Chelsea M. Magin
- Department of Chemical and Biological Engineering and the BioFrontiers Institute University of Colorado 596 UCB Boulder CO 80303舑0596 USA
| | - Daniel L. Alge
- Department of Chemical and Biological Engineering and the BioFrontiers Institute University of Colorado 596 UCB Boulder CO 80303舑0596 USA
- The Howard Hughes Medical Institute University of Colorado 596 UCB Boulder CO 80303舑1904 USA
| | - Sarah T. Gould
- Department of Chemical and Biological Engineering and the BioFrontiers Institute University of Colorado 596 UCB Boulder CO 80303舑0596 USA
| | - Kristi S. Anseth
- Department of Chemical and Biological Engineering and the BioFrontiers Institute University of Colorado 596 UCB Boulder CO 80303舑0596 USA
- The Howard Hughes Medical Institute University of Colorado 596 UCB Boulder CO 80303舑1904 USA
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40
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Biomechanical comparison between mono-, bi-, and tricuspid valve architectures. J Vasc Surg Venous Lymphat Disord 2014; 2:188-193.e1. [DOI: 10.1016/j.jvsv.2013.08.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 07/10/2013] [Accepted: 08/07/2013] [Indexed: 11/21/2022]
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41
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Buchanan RM, Sacks MS. Interlayer micromechanics of the aortic heart valve leaflet. Biomech Model Mechanobiol 2013; 13:813-26. [PMID: 24292631 DOI: 10.1007/s10237-013-0536-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 10/09/2013] [Indexed: 10/26/2022]
Abstract
While the mechanical behaviors of the fibrosa and ventricularis layers of the aortic valve (AV) leaflet are understood, little information exists on their mechanical interactions mediated by the GAG-rich central spongiosa layer. Parametric simulations of the interlayer interactions of the AV leaflets in flexure utilized a tri-layered finite element (FE) model of circumferentially oriented tissue sections to investigate inter-layer sliding hypothesized to occur. Simulation results indicated that the leaflet tissue functions as a tightly bonded structure when the spongiosa effective modulus was at least 25 % that of the fibrosa and ventricularis layers. Novel studies that directly measured transmural strain in flexure of AV leaflet tissue specimens validated these findings. Interestingly, a smooth transmural strain distribution indicated that the layers of the leaflet indeed act as a bonded unit, consistent with our previous observations (Stella and Sacks in J Biomech Eng 129:757-766, 2007) of a large number of transverse collagen fibers interconnecting the fibrosa and ventricularis layers. Additionally, when the tri-layered FE model was refined to match the transmural deformations, a layer-specific bimodular material model (resulting in four total moduli) accurately matched the transmural strain and moment-curvature relations simultaneously. Collectively, these results provide evidence, contrary to previous assumptions, that the valve layers function as a bonded structure in the low-strain flexure deformation mode. Most likely, this results directly from the transverse collagen fibers that bind the layers together to disable physical sliding and maintain layer residual stresses. Further, the spongiosa may function as a general dampening layer while the AV leaflets deforms as a homogenous structure despite its heterogeneous architecture.
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Affiliation(s)
- Rachel M Buchanan
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, USA
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42
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Mechanoregulation of valvular interstitial cell phenotype in the third dimension. Biomaterials 2013; 35:1128-37. [PMID: 24210873 DOI: 10.1016/j.biomaterials.2013.10.047] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 10/15/2013] [Indexed: 01/14/2023]
Abstract
A quantitative understanding of the complex interactions between cells, soluble factors, and the biological and mechanical properties of biomaterials is required to guide cell remodeling toward regeneration of healthy tissue rather than fibrocontractive tissue. In the present study, we characterized the combined effects of boundary stiffness and transforming growth factor-β1 (TGF-β1) on cell-generated forces and collagen accumulation. We first generated a quantitative map of cell-generated tension in response to these factors by culturing valvular interstitial cells (VICs) within micro-scale fibrin gels between compliant posts (0.15-1.05 nN/nm) in chemically-defined media with TGF-β1 (0-5 ng/mL). The VICs generated 100-3000 nN/cell after one week of culture, and multiple regression modeling demonstrated, for the first time, quantitative interaction (synergy) between these factors in a three-dimensional culture system. We then isolated passive and active components of tension within the micro-tissues and found that cells cultured with high levels of stiffness and TGF-β1 expressed myofibroblast markers and generated substantial residual tension in the matrix yet, surprisingly, were not able to generate additional tension in response to membrane depolarization signifying a state of continual maximal contraction. In contrast, negligible residual tension was stored in the low stiffness and TGF-β1 groups indicating a lower potential for shrinkage upon release. We then studied if ECM could be generated under the low tension environment and found that TGF-β1, but not EGF, increased de novo collagen accumulation in both low and high tension environments roughly equally. Combined, these findings suggest that isometric cell force, passive retraction, and collagen production can be tuned by independently altering boundary stiffness and TGF-β1 concentration. The ability to stimulate matrix production without inducing high active tension will aid in the development of robust tissue engineered heart valves and other connective tissue replacements where minimizing tissue shrinkage upon implantation is critical.
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43
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Gould ST, Srigunapalan S, Simmons CA, Anseth KS. Hemodynamic and cellular response feedback in calcific aortic valve disease. Circ Res 2013; 113:186-97. [PMID: 23833293 DOI: 10.1161/circresaha.112.300154] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
This review highlights aspects of calcific aortic valve disease that encompass the entire range of aortic valve disease progression from initial cellular changes to aortic valve sclerosis and stenosis, which can be initiated by changes in blood flow (hemodynamics) and pressure across the aortic valve. Appropriate hemodynamics is important for normal valve function and maintenance, but pathological blood velocities and pressure can have profound consequences at the macroscopic to microscopic scales. At the macroscopic scale, hemodynamic forces impart shear stresses on the surface of the valve leaflets and cause deformation of the leaflet tissue. As discussed in this review, these macroscale forces are transduced to the microscale, where they influence the functions of the valvular endothelial cells that line the leaflet surface and the valvular interstitial cells that populate the valve extracellular matrix. For example, pathological changes in blood flow-induced shear stress can cause dysfunction, impairing their homeostatic functions, and pathological stretching of valve tissue caused by elevated transvalvular pressure can activate valvular interstitial cells and latent paracrine signaling cytokines (eg, transforming growth factor-β1) to promote maladaptive tissue remodeling. Collectively, these coordinated and complex interactions adversely impact bulk valve tissue properties, feeding back to further deteriorate valve function and propagate valve cell pathological responses. Here, we review the role of hemodynamic forces in calcific aortic valve disease initiation and progression, with focus on cellular responses and how they feed back to exacerbate aortic valve dysfunction.
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Affiliation(s)
- Sarah T Gould
- Department of Chemical and Biological Engineering, The Biofrontiers Institute, University of Colorado, Boulder, CO 80303, USA
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44
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Masoumi N, Johnson KL, Howell MC, Engelmayr GC. Valvular interstitial cell seeded poly(glycerol sebacate) scaffolds: toward a biomimetic in vitro model for heart valve tissue engineering. Acta Biomater 2013; 9:5974-88. [PMID: 23295404 DOI: 10.1016/j.actbio.2013.01.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Revised: 11/24/2012] [Accepted: 01/01/2013] [Indexed: 01/01/2023]
Abstract
Tissue engineered replacement heart valves may be capable of overcoming the lack of growth potential intrinsic to current non-viable prosthetics, and thus could potentially serve as permanent replacements in the surgical repair of pediatric valvular lesions. However, the evaluation of candidate combinations of cells and scaffolds lacks a biomimetic in vitro model with broadly tunable, anisotropic and elastomeric structural-mechanical properties. Toward establishing such an in vitro model, in the current study, porcine aortic and pulmonary valvular interstitial cells (i.e. biomimetic cells) were cultivated on anisotropic, micromolded poly(glycerol sebacate) scaffolds (i.e. biomimetic scaffolds). Following 14 and 28 days of static culture, cell-seeded scaffolds and unseeded controls were assessed for their mechanical properties, and cell-seeded scaffolds were further characterized by confocal fluorescence and scanning electron microscopy, and by collagen and DNA assays. Poly(glycerol sebacate) micromolding yielded scaffolds with anisotropic stiffnesses resembling those of native valvular tissues in the low stress-strain ranges characteristic of physiologic valvular function. Scaffold anisotropy was largely retained upon cultivation with valvular interstitial cells; while the mechanical properties of unseeded scaffolds progressively diminished, cell-seeded scaffolds either retained or exceeded initial mechanical properties. Retention of mechanical properties in cell-seeded scaffolds paralleled the accretion of collagen, which increased significantly from 14 to 28 days. This study demonstrates that valvular interstitial cells can be cultivated on anisotropic poly(glycerol sebacate) scaffolds to yield biomimetic in vitro models with which clinically relevant cells and future scaffold designs can be evaluated.
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45
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Chen Q, Bruyneel A, Carr C, Czernuszka J. Bio-mechanical Properties of Novel Bi-layer Collagen-Elastin Scaffolds for Heart Valve Tissue Engineering. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/j.proeng.2013.05.118] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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46
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Amoroso NJ, D'Amore A, Hong Y, Rivera CP, Sacks MS, Wagner WR. Microstructural manipulation of electrospun scaffolds for specific bending stiffness for heart valve tissue engineering. Acta Biomater 2012; 8:4268-77. [PMID: 22890285 DOI: 10.1016/j.actbio.2012.08.002] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 07/03/2012] [Accepted: 08/03/2012] [Indexed: 11/17/2022]
Abstract
Biodegradable thermoplastic elastomers are attractive for application in cardiovascular tissue construct development due to their amenability to a wide range of physical property tuning. For heart valve leaflets, while low flexural stiffness is a key design feature, control of this parameter has been largely neglected in the scaffold literature where electrospinning is being utilized. This study evaluated the effect of processing variables and secondary fiber populations on the microstructure, tensile and bending mechanics of electrospun biodegradable polyurethane scaffolds for heart valve tissue engineering. Scaffolds were fabricated from poly(ester urethane) urea (PEUU) and the deposition mandrel was translated at varying rates in order to modify fiber intersection density. Scaffolds were also fabricated in conjunction with secondary fiber populations designed either for mechanical reinforcement or to be selectively removed following fabrication. It was determined that increasing fiber intersection densities within PEUU scaffolds was associated with lower bending moduli. Further, constructs fabricated with stiff secondary fiber populations had higher bending moduli whereas constructs with secondary fiber populations which were selectively removed had noticeably lower bending moduli. Insights gained from this work will be directly applicable to the fabrication of soft tissue constructs, specifically in the development of cardiac valve tissue constructs.
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Affiliation(s)
- Nicholas J Amoroso
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15219, USA
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Wells SM, Pierlot CM, Moeller AD. Physiological remodeling of the mitral valve during pregnancy. Am J Physiol Heart Circ Physiol 2012; 303:H878-92. [DOI: 10.1152/ajpheart.00845.2011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is growing evidence that heart valves are not passive structures but can remodel with left ventricular dysfunction. To determine if these tissues remodel under nonpathological conditions, we examined the mirtal valve anterior leaflet during the volume loading and cardiac expansion of pregnancy using a bovine model. We measured leaflet dimensions, chordal attachments, and biaxial mechanical properties of leaflets collected from never-pregnant heifers and pregnant cows (pregnancy duration estimated from fetal length). Hydrothermal isometric tension (HIT) tests were performed to assess the denaturation temperature (Td) associated with collagen molecular stability and the load decay half-time ( t1//2) associated with intermolecular cross-linking. Histological changes were examined using Verhoeff-van Gieson and picrosirius red staining with polarized light. We observed striking changes to the structure and material properties of the mitral anterior leaflet during pregnancy. Leaflet area was increased 33%, with a surprising increase (nearly 25%) in chordae tendinae attachments. There was a biphasic change in leaflet extensibility: it rapidly decreased by 30% and then reversed to prepregnant values by late pregnancy. The 2°C decrease in Td in pregnancy was indicative of collagen remodeling, whereas the 70% increase in HIT t1/2 indicated an increase in collagen cross-linking. Finally, histological results suggested transient increases in leaflet thickness and transient decreases in collagen crimp. This remodeling may compensate for the increased loading conditions associated with pregnancy by normalizing leaflet stress and maintaining coaptation. Understanding the mechanisms of mitral valve physiological remodeling in pregnancy could contribute to alternative treatments of pathological remodeling associated with left ventricular dysfunction.
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Affiliation(s)
- Sarah M. Wells
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; and
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Caitlin M. Pierlot
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; and
| | - Andrew D. Moeller
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; and
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Hammer PE, Chen PC, del Nido PJ, Howe RD. Computational model of aortic valve surgical repair using grafted pericardium. J Biomech 2012; 45:1199-204. [PMID: 22341628 DOI: 10.1016/j.jbiomech.2012.01.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 12/16/2011] [Accepted: 01/30/2012] [Indexed: 10/28/2022]
Abstract
Aortic valve reconstruction using leaflet grafts made from autologous pericardium is an effective surgical treatment for some forms of aortic regurgitation. Despite favorable outcomes in the hands of skilled surgeons, the procedure is underutilized because of the difficulty of sizing grafts to effectively seal with the native leaflets. Difficulty is largely due to the complex geometry and function of the valve and the lower distensibility of the graft material relative to native leaflet tissue. We used a structural finite element model to explore how a pericardial leaflet graft of various sizes interacts with two native leaflets when the valve is closed and loaded. Native leaflets and pericardium are described by anisotropic, hyperelastic constitutive laws, and we model all three leaflets explicitly and resolve leaflet contact in order to simulate repair strategies that are asymmetrical with respect to valve geometry and leaflet properties. We ran simulations with pericardial leaflet grafts of various widths (increase of 0%, 7%, 14%, 21% and 27%) and heights (increase of 0%, 13%, 27% and 40%) relative to the native leaflets. Effectiveness of valve closure was quantified based on the overlap between coapting leaflets. Results showed that graft width and height must both be increased to achieve proper valve closure, and that a graft 21% wider and 27% higher than the native leaflet creates a seal similar to a valve with three normal leaflets. Experimental validation in excised porcine aortas (n=9) corroborates the results of simulations.
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Affiliation(s)
- Peter E Hammer
- Department of Cardiac Surgery, Children's Hospital, Boston, MA, USA.
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Fisher CI, Chen J, Merryman WD. Calcific nodule morphogenesis by heart valve interstitial cells is strain dependent. Biomech Model Mechanobiol 2012; 12:5-17. [PMID: 22307683 DOI: 10.1007/s10237-012-0377-8] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 01/18/2012] [Indexed: 01/26/2023]
Abstract
Calcific aortic valve disease (CAVD) results in impaired function through the inability of valves to fully open and close, but the causes of this pathology are unknown. Stiffening of the aorta is associated with CAVD and results in exposing the aortic valves to greater mechanical strain. Transforming growth factor β1 (TGF-β1) is enriched in diseased valves and has been shown to combine with strain to synergistically alter aortic valve interstitial cell (AVIC) phenotypes. Therefore, we investigated the role of strain and TGF-β1 on the calcification of AVICs. Following TGF-β1 pretreatment, strain induced intact monolayers to aggregate and calcify. Using a wound assay, we confirmed that TGF-β1 increases tension in the monolayer in parallel with α-smooth muscle actin (αSMA) expression. Continual exposure to strain accelerates aggregates to calcify into mature nodules that contain a necrotic core surrounded by an apoptotic ring. This phenotype appears to be mediated by strain inhibition of AVIC migration after the initial formation of aggregates. To better interpret the extent to which externally applied strain physically impacts this process, we modified the classical Lamé solution, derived using principles from linear elasticity, to reveal strain magnification as a novel feature occurring in a mechanical environment that supports nodule formation. These results indicate that strain can impact multiple points of nodule formation: by modifying tension in the monolayer, remodeling cell contacts, migration, apoptosis, and mineralization. Therefore, strain-induced nodule formation provides new directions for developing strategies to address CAVD.
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Affiliation(s)
- Charles I Fisher
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37232-0493, USA
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Krishnamurthy VK, Opoka AM, Kern CB, Guilak F, Narmoneva DA, Hinton RB. Maladaptive matrix remodeling and regional biomechanical dysfunction in a mouse model of aortic valve disease. Matrix Biol 2012; 31:197-205. [PMID: 22265892 DOI: 10.1016/j.matbio.2012.01.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 12/21/2011] [Accepted: 01/03/2012] [Indexed: 12/12/2022]
Abstract
Aortic valve disease (AVD) occurs in 2.5% of the general population and often requires surgical intervention. Aortic valve malformation (AVM) underlies the majority of cases, suggesting a developmental etiology. Elastin haploinsufficiency results in complex cardiovascular problems, and 20-45% of patients have AVM and/or AVD. Elastin insufficient (Eln+/-) mice demonstrate AVM and latent AVD due to abnormalities in the valve annulus region. The objective of this study was to examine extracellular matrix (ECM) remodeling and biomechanical properties in regional aortic valve tissue and determine the impact of early AVM on late AVD in the Eln+/- mouse model. Aortic valve ECM composition and remodeling from juvenile, adult, and aged stages were evaluated in Eln+/- mice using histology, ELISA, immunohistochemistry and gelatin zymography. Aortic valve tissue biomechanical properties were determined using micropipette aspiration. Cartilage-like nodules were demonstrated within the valve annulus region at all stages identifying a developmental abnormality preceding AVD. Interestingly, maladaptive ECM remodeling was observed in early AVM without AVD and worsened with late AVD, as evidenced by increased MMP-2 and MMP-9 expression and activity, as well as abnormalities in ADAMTS-mediated versican processing. Cleaved versican was increased in the valve annulus region of aged Eln+/- mice, and this abnormality correlated temporally with adverse alterations in valve tissue biomechanical properties and the manifestation of AVD. These findings identify maladaptive ECM remodeling in functional AVM as an early disease process with a progressive natural history, similar to that seen in human AVD, emphasizing the importance of the annulus region in pathogenesis. Combining molecular and engineering approaches provides complementary mechanistic insights that may be informative in the search for new therapeutic targets and durable valve bioprostheses.
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Affiliation(s)
- Varun K Krishnamurthy
- Division of Cardiology, the Heart Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
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