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Stephens CJ, Kobayashi R, Berry DC, Butcher JT. The Role of Matrix Stiffness And Viscosity on Lipid Phenotype And Fat Lineage Potential. Tissue Eng Part A 2024. [PMID: 39165245 DOI: 10.1089/ten.tea.2024.0149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/22/2024] Open
Abstract
Autologous fat transfer is a common procedure that patients undergo to rejuvenate large soft tissue defects. However, these surgeries are complicated by limited tissue sources, donor-site morbidity, and necrosis. While the biofabrication of fat tissue can serve as a clinical option for reconstructive surgery, the influence of matrix mechanics, specifically stiffness and viscosity, on adipogenesis requires further elucidation. Additionally, the effects of these mechanical parameters on metabolic and thermogenic fat potential have yet to be investigated. In this study, gelatin methacryloyl (GelMA) polymers with varying degrees of methacrylation (DoM) were fabricated to create matrices with different stiffnesses and viscosities. Human adipose-derived mesenchymal stem cells were then encapsulated in mechanically tunable GelMA and underwent adipogenesis to investigate the effects of matrix mechanics on lipid phenotype and fat potential. Mechanical testing confirmed that GelMA stiffness was regulated by DoM and weight composition, whereas viscosity was determined by the latter. Further work revealed that while lipid phenotype became more enriched as matrix stiffness and viscosity declined, the potential toward metabolic and thermogenic fat appeared to be more viscous dependent rather than stiffness dependent. In addition, fatty acid binding protein 4 and uncoupling protein 1 gene expression exhibited viscous-dependent behavior despite comparable levels of peroxisome proliferator-activated receptor gamma. However, despite the superior role of viscosity, lipid quantity and mitochondrial abundance demonstrated stiffness-dependent behavior. Overall, this work revealed that matrix viscosity played a more superior role than stiffness in driving adipogenesis and distinguishing between metabolic and thermogenic fat potential. Ultimately, this differentiation in fat production is important for engineering ideal adipose tissue for large soft tissue defects.
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Affiliation(s)
- Chelsea J Stephens
- Cornell University, Nancy E. and Peter C. Meinig School of Biomedical Engineering, Ithaca, New York, USA
| | - Reina Kobayashi
- Cornell University, Nancy E. and Peter C. Meinig School of Biomedical Engineering, Ithaca, New York, USA
| | - Daniel C Berry
- College of Human Ecology, Division of Nutrition Science, Cornell University, Ithaca, New York, USA
| | - Jonathan T Butcher
- Cornell University, Nancy E. and Peter C. Meinig School of Biomedical Engineering, Ithaca, New York, USA
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2
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de Lucio M, Leng Y, Wang H, Vlachos PP, Gomez H. Modeling drug transport and absorption in subcutaneous injection of monoclonal antibodies: Impact of tissue deformation, devices, and physiology. Int J Pharm 2024; 661:124446. [PMID: 38996825 DOI: 10.1016/j.ijpharm.2024.124446] [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: 04/24/2024] [Revised: 06/21/2024] [Accepted: 07/06/2024] [Indexed: 07/14/2024]
Abstract
The pharmaceutical industry has experienced a remarkable increase in the use of subcutaneous injection of monoclonal antibodies (mAbs), attributed mainly to its advantages in reducing healthcare-related costs and enhancing patient compliance. Despite this growth, there is a limited understanding of how tissue mechanics, physiological parameters, and different injection devices and techniques influence the transport and absorption of the drug. In this work, we propose a high-fidelity computational model to study drug transport and absorption during and after subcutaneous injection of mAbs. Our numerical model includes large-deformation mechanics, fluid flow, drug transport, and blood and lymphatic uptake. Through this computational framework, we analyze the tissue material responses, plume dynamics, and drug absorption. We analyze different devices, injection techniques, and physiological parameters such as BMI, flow rate, and injection depth. Finally, we compare our numerical results against the experimental data from the literature.
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Affiliation(s)
- Mario de Lucio
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907, USA.
| | - Yu Leng
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907, USA; Los Alamos National Laboratory, Los Alamos, NM 87544, USA
| | - Hao Wang
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907, USA
| | - Pavlos P Vlachos
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907, USA
| | - Hector Gomez
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907, USA
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3
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Segain A, Sciume G, Pillet H, Rohan PY. In vivo mechanical response of thigh soft tissues under compression: A two-layer model allows an improved representation of the local tissue kinematics. J Mech Behav Biomed Mater 2024; 156:106584. [PMID: 38810544 DOI: 10.1016/j.jmbbm.2024.106584] [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: 12/22/2023] [Revised: 05/14/2024] [Accepted: 05/18/2024] [Indexed: 05/31/2024]
Abstract
Biomechanical parameters have the potential to be used as physical markers for prevention and diagnosis. Finite Element Analysis (FEA) is a widely used tool to evaluate these parameters in vivo. However, the development of clinically relevant FEA requires personalisation of the geometry, boundary conditions, and constitutive parameters. This contribution focuses on the characterisation of mechanical properties in vivo which remains a significant challenge for the community. The aim of this retrospective study is to evaluate the sensitivity of the computed elastic parameters (shear modulus of fat and muscle tissues) derived by inverse analysis as a function of the geometrical modelling assumption (homogenised monolayer vs bilayer) and the formulation of the cost function. The methodology presented here proposes to extract the experimental force-displacement response for each tissue layer (muscle and fat) and construct the associated Finite Element Model for each volunteer, based on data previously collected in our group (N = 7 volunteers) as reported in (Fougeron et al., 2020). The sensitivity analysis indicates that the choice of the cost function has minimal impact on the topology of the response surface in the parametric space. Each surface displays a valley of parameters that minimises the cost function. The constitutive properties of the thigh (reported as median ± interquartile range) were determined to be (μ=198±322Pa,α=37) for the monolayer and (μmuscle=1675±1127Pa,αmuscle=22±14,μfat=537±1131Pa,αfat=32±7) for the bilayer. A comparison of the homogenised monolayer and bilayer models showed that adding a layer reduces the error on the local force displacement curves, increasing the accuracy of the local kinematics of soft tissues during indentation. This allows for an increased understanding of load transmission in soft tissue. The comparison of the two models in terms of strains indicates that the modelling choice significantly influences the localization of maximal compressive strains. These results support the idea that the biomechanical community should conduct further work to develop reliable methodologies for estimating in vivo strain in soft tissue.
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Affiliation(s)
- Alexandre Segain
- Arts et Métiers Institute of Technology, Université Sorbonne Paris Nord, IBHGC - Institut de Biomécanique Humaine Georges Charpak, HESAM Université, F-75013, Paris, France.
| | - Giuseppe Sciume
- Arts et Metiers Institute of Technology, Univ. of Bordeaux, CNRS, Bordeaux INP, INRAE, I2M Bordeaux, Av d'Aquitaine, 33607, Pessac, France
| | - Hélène Pillet
- Arts et Métiers Institute of Technology, Université Sorbonne Paris Nord, IBHGC - Institut de Biomécanique Humaine Georges Charpak, HESAM Université, F-75013, Paris, France
| | - Pierre-Yves Rohan
- Arts et Métiers Institute of Technology, Université Sorbonne Paris Nord, IBHGC - Institut de Biomécanique Humaine Georges Charpak, HESAM Université, F-75013, Paris, France
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Alloisio M, Wolffs JJM, Gasser TC. Specimen width affects vascular tissue integrity for in-vitro characterisation. J Mech Behav Biomed Mater 2024; 154:106520. [PMID: 38569421 DOI: 10.1016/j.jmbbm.2024.106520] [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: 12/01/2023] [Revised: 03/08/2024] [Accepted: 03/21/2024] [Indexed: 04/05/2024]
Abstract
The preparation of slender specimens for in-vitro tissue characterisation could potentially alter mechanical tissue properties. To investigate this factor, rectangular specimens were prepared from the wall of the porcine aorta for uniaxial tensile loading. Varying strip widths of 16 mm, 8 mm, and 4 mm were achieved by excising zero, one, and three cuts within the specimen along the loading direction, respectively. While specimens loaded along the vessel's circumferential direction acquired consistent tissue properties, the width of test specimens influenced the results of axially loaded tissue; vascular wall stiffness was reduced by approximately 40% in specimens with strips 4 mm wide. In addition, the cross-loading stretch was strongly influenced by specimen strip width, and fiber sliding contributed to the softening of slender tensile specimens, an outcome from finite element analysis of test specimens. We may, therefore, conclude that cutting orthogonal to the main direction of collagen fibers introduces mechanical trauma that weakens slender tensile specimens, compromising the determination of representative mechanical vessel wall properties.
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Affiliation(s)
- Marta Alloisio
- Material and Structural Mechanics, Department of Engineering Mechanics, KTH Royal Institute of Technology, Sweden
| | - Joey J M Wolffs
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - T Christian Gasser
- Material and Structural Mechanics, Department of Engineering Mechanics, KTH Royal Institute of Technology, Sweden.
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Barsimantov J, Payne J, de Lucio M, Hakim M, Gomez H, Solorio L, Tepole AB. Poroelastic Characterization and Modeling of Subcutaneous Tissue Under Confined Compression. Ann Biomed Eng 2024; 52:1638-1652. [PMID: 38472602 DOI: 10.1007/s10439-024-03477-1] [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: 11/21/2023] [Accepted: 02/17/2024] [Indexed: 03/14/2024]
Abstract
Subcutaneous tissue mechanics are important for drug delivery. Yet, even though this material is poroelastic, its mechanical characterization has focused on its hyperelastic response. Moreover, advancement in subcutaneous drug delivery requires effective tissue mimics such as hydrogels for which similar gaps of poroelastic data exist. Porcine subcutaneous samples and gelatin hydrogels were tested under confined compression at physiological conditions and strain rates of 0.01%/s in 5% strain steps with 2600 s of stress relaxation between loading steps. Force-time data were used in an inverse finite element approach to obtain material parameters. Tissues and gels were modeled as porous neo-Hookean materials with properties specified via shear modulus, effective solid volume fraction, initial hydraulic permeability, permeability exponent, and normalized viscous relaxation moduli. The constitutive model was implemented into an isogeometric analysis (IGA) framework to study subcutaneous injection. Subcutaneous tissue exhibited an initial spike in stress due to compression of the solid and fluid pressure buildup, with rapid relaxation explained by fluid drainage, and longer time-scale relaxation explained by viscous dissipation. The inferred parameters aligned with the ranges reported in the literature. Hydraulic permeability, the most important parameter for drug delivery, was in the rangek 0 ∈ [ 0.142 , 0.203 ] mm4 /(N s). With these parameters, IGA simulations showed peak stresses due to a 1-mL injection to reach 48.8 kPa at the site of injection, decaying after drug volume disperses into the tissue. The poro-hyper-viscoelastic neo-Hookean model captures the confined compression response of subcutaneous tissue and gelatin hydrogels. IGA implementation enables predictive simulations of drug delivery.
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Affiliation(s)
- Jacques Barsimantov
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA
| | - Jordanna Payne
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
- Indiana University School of Medicine, Indianapolis, IN, USA
| | - Mario de Lucio
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA
| | - Mazin Hakim
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Hector Gomez
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA
| | - Luis Solorio
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Adrian B Tepole
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA.
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
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6
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Barsimantov Mandel J, Solorio L, Tepole AB. Geometry of adipocyte packing in subcutaneous tissue contributes to nonlinear tissue properties captured through a Gaussian process surrogate model. SOFT MATTER 2024; 20:4197-4207. [PMID: 38477130 DOI: 10.1039/d3sm01661g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/14/2024]
Abstract
Subcutaneous tissue mechanical response is governed by the geometry and mechanical properties at the microscale and drives physiological and clinical processes such as drug delivery. Even though adipocyte packing is known to change with age, disease, and from one individual to another, the link between the geometry of the packing and the overall mechanical response of adipose tissue remains poorly understood. Here we create 1200 periodic representative volume elements (RVEs) that sample the possible space of Laguerre packings describing adipose tissue. RVE mechanics are modeled under tri-axial loading. Equilibrium configuration of RVEs is solved by minimizing an energetic potential that includes volume change contributions from adipocyte expansion, and area change contributions from collagen foam stretching. The resulting mechanical response across all RVE samples is interpolated with the aid of a Gaussian process (GP), revealing how the microscale geometry dictates the overall RVE mechanics. For example, increase in adipocyte size and increase in sphericity lead to adipose tissue softening. We showcase the use of the homogenized model in finite element simulations of drug injection by implementing a Blatz-Ko model, informed by the GP, as a custom material in the popular open-source package FEBio. These simulations show how microscale geometry can lead to vastly different injection dynamics even if the constituent parameters are held constant, highlighting the importance of characterizing individual's adipose tissue structure in the development of personalized therapies.
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Affiliation(s)
| | - Luis Solorio
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, USA
| | - Adrian Buganza Tepole
- School of Mechanical Engineering, Purdue University, 205 Gates Rd, West Lafayette, USA.
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, USA
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7
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Holzer CS, Pukaluk A, Viertler C, Regitnig P, Caulk AW, Eschbach M, Contini EM, Holzapfel GA. Biomechanical characterization of the passive porcine stomach. Acta Biomater 2024; 173:167-183. [PMID: 37984627 DOI: 10.1016/j.actbio.2023.11.008] [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: 07/13/2023] [Revised: 11/02/2023] [Accepted: 11/07/2023] [Indexed: 11/22/2023]
Abstract
The complex mechanics of the gastric wall facilitates the main digestive tasks of the stomach. However, the interplay between the mechanical properties of the stomach, its microstructure, and its vital functions is not yet fully understood. Importantly, the pig animal model is widely used in biomedical research for preliminary or ethically prohibited studies of the human digestion system. Therefore, this study aims to thoroughly characterize the mechanical behavior and microstructure of the porcine stomach. For this purpose, multiple quasi-static mechanical tests were carried out with three different loading modes, i.e., planar biaxial extension, radial compression, and simple shear. Stress-relaxation tests complemented the quasi-static experiments to evaluate the deformation and strain-dependent viscoelastic properties. Each experiment was conducted on specimens of the complete stomach wall and two separate layers, mucosa and muscularis, from each of the three gastric regions, i.e., fundus, body, and antrum. The significant preconditioning effects and the considerable regional and layer-specific differences in the tissue response were analyzed. Furthermore, the mechanical experiments were complemented with histology to examine the influence of the microstructural composition on the macrostructural mechanical response and vice versa. Importantly, the shear tests showed lower stresses in the complete wall compared to the single layers which the loose network of submucosal collagen might explain. Also, the stratum arrangement of the muscularis might explain mechanical anisotropy during tensile tests. This study shows that gastric tissue is characterized by a highly heterogeneous microstructure with regional variations in layer composition reflecting not only functional differences but also diverse mechanical behavior. STATEMENT OF SIGNIFICANCE: Unfortunately, only few experimental data on gastric tissue are available for an adequate material parameter and model estimation. The present study therefore combines layer- and region-specific stomach wall mechanics obtained under multiple loading conditions with histological insights into the heterogeneous microstructure. On the one hand, the extensive data sets of this study expand our understanding of the interplay between gastric mechanics, motility and functionality, which could help to identify and treat associated pathologies. On the other hand, such data sets are of high relevance for the constitutive modeling of stomach tissue, and its application in the field of medical engineering, e.g., in the development of surgical staplers and the improvement of bariatric surgical interventions.
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Affiliation(s)
| | - Anna Pukaluk
- Institute of Biomechanics, Graz University of Technology, Austria
| | - Christian Viertler
- Diagnostic and Research Institute of Pathology, Medical University of Graz, Austria
| | - Peter Regitnig
- Diagnostic and Research Institute of Pathology, Medical University of Graz, Austria
| | | | | | | | - Gerhard A Holzapfel
- Institute of Biomechanics, Graz University of Technology, Austria; Department of Structural Engineering, NTNU, Trondheim, Norway.
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de Lucio M, Leng Y, Wang H, Ardekani AM, Vlachos PP, Shi G, Gomez H. Computational modeling of the effect of skin pinch and stretch on subcutaneous injection of monoclonal antibodies using autoinjector devices. Biomech Model Mechanobiol 2023; 22:1965-1982. [PMID: 37526775 DOI: 10.1007/s10237-023-01746-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 07/06/2023] [Indexed: 08/02/2023]
Abstract
Subcutaneous injection of monoclonal antibodies (mAbs) has experienced unprecedented growth in the pharmaceutical industry due to its benefits in patient compliance and cost-effectiveness. However, the impact of different injection techniques and autoinjector devices on the drug's transport and uptake is poorly understood. Here, we develop a biphasic large-deformation chemomechanical model that accounts for the components of the extracellular matrix that govern solid deformation and fluid flow within the subcutaneous tissue: interstitial fluid, collagen fibers and negatively charged proteoglycan aggregates. We use this model to build a high-fidelity representation of a virtual patient performing a subcutaneous injection of mAbs. We analyze the impact of the pinch and stretch methods on the injection dynamics and the use of different handheld autoinjector devices. The results suggest that autoinjector base plates with a larger device-skin contact area cause significantly lower tissue mechanical stress, fluid pressure and fluid velocity during the injection process. Our simulations indicate that the stretch technique presents a higher risk of intramuscular injection for autoinjectors with a relatively long needle insertion depth.
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Affiliation(s)
- Mario de Lucio
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN, 47907, USA
| | - Yu Leng
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN, 47907, USA
| | - Hao Wang
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN, 47907, USA
| | - Arezoo M Ardekani
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN, 47907, USA
| | - Pavlos P Vlachos
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN, 47907, USA
| | - Galen Shi
- Eli Lilly and Company, Indianapolis, IN, USA
| | - Hector Gomez
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN, 47907, USA.
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Terzano M, Wollner MP, Kainz MP, Rolf-Pissarczyk M, Götzen N, Holzapfel GA. Modelling the anisotropic inelastic response of polymeric scaffolds for in situ tissue engineering applications. J R Soc Interface 2023; 20:20230318. [PMID: 37700713 PMCID: PMC10498354 DOI: 10.1098/rsif.2023.0318] [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: 06/01/2023] [Accepted: 08/18/2023] [Indexed: 09/14/2023] Open
Abstract
In situ tissue engineering offers an innovative solution for replacement valves and grafts in cardiovascular medicine. In this approach, a scaffold, which can be obtained by polymer electrospinning, is implanted into the human body and then infiltrated by cells, eventually replacing the scaffold with native tissue. In silico simulations of the whole process in patient-specific models, including implantation, growth and degradation, are very attractive to study the factors that might influence the end result. In our research, we focused on the mechanical behaviour of the polymeric scaffold and its short-term response. Following a recently proposed constitutive model for the anisotropic inelastic behaviour of fibrous polymeric materials, we present here its numerical implementation in a finite element framework. The numerical model is developed as user material for commercial finite element software. The verification of the implementation is performed for elementary deformations. Furthermore, a parallel-plate test is proposed as a large-scale representative example, and the model is validated by comparison with experiments.
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Affiliation(s)
- Michele Terzano
- Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | | | - Manuel P. Kainz
- Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | | | - Nils Götzen
- 4RealSim Services BV, IJsselstein, The Netherlands
| | - Gerhard A. Holzapfel
- Institute of Biomechanics, Graz University of Technology, Graz, Austria
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
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10
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Sree VD, Toaquiza-Tubon JD, Payne J, Solorio L, Tepole AB. Damage and Fracture Mechanics of Porcine Subcutaneous Tissue Under Tensile Loading. Ann Biomed Eng 2023; 51:2056-2069. [PMID: 37233856 DOI: 10.1007/s10439-023-03233-x] [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: 11/25/2022] [Accepted: 05/04/2023] [Indexed: 05/27/2023]
Abstract
Subcutaneous injection, which is a preferred delivery method for many drugs, causes deformation, damage, and fracture of the subcutaneous tissue. Yet, experimental data and constitutive modeling of these dissipation mechanisms in subcutaneous tissue remain limited. Here we show that subcutaneous tissue from the belly and breast anatomical regions in the swine show nonlinear stress-strain response with the characteristic J-shaped behavior of collagenous tissue. Additionally, subcutaneous tissue experiences damage, defined as a decrease in the strain energy capacity, as a function of the previously experienced maximum deformation. The elastic and damage response of the tissue are accurately described by a microstructure-driven constitutive model that relies on the convolution of a neo-Hookean material of individual fibers with a fiber orientation distribution and a fiber recruitment distribution. The model fit revealed that subcutaneous tissue can be treated as initially isotropic, and that changes in the fiber recruitment distribution with loading are enough to explain the dissipation of energy due to damage. When tested until failure, subcutaneous tissue that has undergone damage fails at the same peak stress as virgin samples, but at a much larger stretch, overall increasing the tissue toughness. Together with a finite element implementation, these data and constitutive model may enable improved drug delivery strategies and other applications for which subcutaneous tissue biomechanics are relevant.
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Affiliation(s)
- Vivek D Sree
- School of Mechanical Engineering, Purdue University, West Lafayette, USA
| | | | - Jordanna Payne
- School of Mechanical Engineering, Purdue University, West Lafayette, USA
| | - Luis Solorio
- School of Mechanical Engineering, Purdue University, West Lafayette, USA
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11
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Hatt A, Lloyd R, Bolsterlee B, Bilston LE. Strain-dependent shear properties of human adipose tissue in vivo. J Mech Behav Biomed Mater 2023; 143:105924. [PMID: 37276651 DOI: 10.1016/j.jmbbm.2023.105924] [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: 04/04/2023] [Revised: 05/14/2023] [Accepted: 05/20/2023] [Indexed: 06/07/2023]
Abstract
INTRODUCTION Human adipose tissue (fat) deforms substantially under normal physiological loading and during impact. Thus, accurate data on strain-dependent stiffness of fat is essential for the creation of accurate biomechanical models. Previous studies on ex vivo samples reported human fat to be nonlinear and viscoelastic. When static compression is combined with magnetic resonance (MR) elastography (an imaging technique used to measure viscoelasticity in vivo), the large deformation properties of tissues can be determined. Here, we use magnetic resonance elastography to quantify fat shear modulus in vivo under increasing compressive strain and compare it to the underlying passive gluteal muscle. METHODS The right buttocks of ten female participants were incrementally compressed at four levels while MR elastography (50 Hz) and mDixon images were acquired. Maps of tissue shear modulus (G*) were reconstructed from the MR elastography phase images. Tissue strain was estimated from registration of deformed and undeformed mDixon images. Linear mixed models were fit to the natural logarithm of the compressive strain and shear modulus data for each tissue. RESULTS Shear modulus increased in an exponential relationship with compressive strain in fat: Gfat*=748.5*Cyy-1.18Pa, and to a lesser extent in muscle: Gmuscle*=956.4*Cyy-0.36Pa. The baseline (undeformed) stiffness of fat was significantly lower than that of muscle (mean G*fat = 752 Pa, mean G*muscle = 1000 Pa, paired samples t-test, t = -4.24, p = 0.001). However, fat exhibited a significantly higher degree of strain dependence (characterised by the exponent of the curve, t = -6.47, p = 0.0001). CONCLUSION Static compression of human adipose tissue results in an increase in apparent viscoelastic shear modulus (stiffness), in an exponentially increasing relationship. The relationships defined here can be used in the development of physiologically realistic computational models for impact, injury and biomechanical modelling.
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Affiliation(s)
- Alice Hatt
- Neuroscience Research Australia, PO Box 1165, Randwick, NSW, 2031, Australia
| | - Robert Lloyd
- Neuroscience Research Australia, PO Box 1165, Randwick, NSW, 2031, Australia; University of New South Wales, Faculty of Medicine & Health, 18 High St, Kensington, NSW, 2052, Australia
| | - Bart Bolsterlee
- Neuroscience Research Australia, PO Box 1165, Randwick, NSW, 2031, Australia; University of New South Wales, Graduate School of Biomedical Engineering, Library Rd, Kensington, NSW, 2033, Australia
| | - Lynne E Bilston
- Neuroscience Research Australia, PO Box 1165, Randwick, NSW, 2031, Australia; University of New South Wales, Faculty of Medicine & Health, 18 High St, Kensington, NSW, 2052, Australia.
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12
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Kainz MP, Greiner A, Hinrichsen J, Kolb D, Comellas E, Steinmann P, Budday S, Terzano M, Holzapfel GA. Poro-viscoelastic material parameter identification of brain tissue-mimicking hydrogels. Front Bioeng Biotechnol 2023; 11:1143304. [PMID: 37101751 PMCID: PMC10123293 DOI: 10.3389/fbioe.2023.1143304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 03/27/2023] [Indexed: 04/28/2023] Open
Abstract
Understanding and characterizing the mechanical and structural properties of brain tissue is essential for developing and calibrating reliable material models. Based on the Theory of Porous Media, a novel nonlinear poro-viscoelastic computational model was recently proposed to describe the mechanical response of the tissue under different loading conditions. The model contains parameters related to the time-dependent behavior arising from both the viscoelastic relaxation of the solid matrix and its interaction with the fluid phase. This study focuses on the characterization of these parameters through indentation experiments on a tailor-made polyvinyl alcohol-based hydrogel mimicking brain tissue. The material behavior is adjusted to ex vivo porcine brain tissue. An inverse parameter identification scheme using a trust region reflective algorithm is introduced and applied to match experimental data obtained from the indentation with the proposed computational model. By minimizing the error between experimental values and finite element simulation results, the optimal constitutive model parameters of the brain tissue-mimicking hydrogel are extracted. Finally, the model is validated using the derived material parameters in a finite element simulation.
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Affiliation(s)
- Manuel P. Kainz
- Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | - Alexander Greiner
- Department Mechanical Engineering, Institute of Applied Mechanics, Friedrich Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Jan Hinrichsen
- Department Mechanical Engineering, Institute of Applied Mechanics, Friedrich Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Dagmar Kolb
- Center for Medical Research, Gottfried Schatz Research Center, Core Facility Ultrastructure Analysis, Medical University of Graz, Graz, Austria
- Division of Cell Biology, Histology and Embryology, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
| | - Ester Comellas
- Department of Physics, Serra Húnter Fellow, Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
| | - Paul Steinmann
- Department Mechanical Engineering, Institute of Applied Mechanics, Friedrich Alexander-University Erlangen-Nürnberg, Erlangen, Germany
- Glasgow Computational Engineering Centre, University of Glasgow, Glasgow, United Kingdom
| | - Silvia Budday
- Department Mechanical Engineering, Institute of Applied Mechanics, Friedrich Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Michele Terzano
- Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | - Gerhard A. Holzapfel
- Institute of Biomechanics, Graz University of Technology, Graz, Austria
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
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13
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Pensalfini M, Tepole AB. Mechano-biological and bio-mechanical pathways in cutaneous wound healing. PLoS Comput Biol 2023; 19:e1010902. [PMID: 36893170 PMCID: PMC10030043 DOI: 10.1371/journal.pcbi.1010902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 03/21/2023] [Accepted: 01/27/2023] [Indexed: 03/10/2023] Open
Abstract
Injuries to the skin heal through coordinated action of fibroblast-mediated extracellular matrix (ECM) deposition, ECM remodeling, and wound contraction. Defects involving the dermis result in fibrotic scars featuring increased stiffness and altered collagen content and organization. Although computational models are crucial to unravel the underlying biochemical and biophysical mechanisms, simulations of the evolving wound biomechanics are seldom benchmarked against measurements. Here, we leverage recent quantifications of local tissue stiffness in murine wounds to refine a previously-proposed systems-mechanobiological finite-element model. Fibroblasts are considered as the main cell type involved in ECM remodeling and wound contraction. Tissue rebuilding is coordinated by the release and diffusion of a cytokine wave, e.g. TGF-β, itself developed in response to an earlier inflammatory signal triggered by platelet aggregation. We calibrate a model of the evolving wound biomechanics through a custom-developed hierarchical Bayesian inverse analysis procedure. Further calibration is based on published biochemical and morphological murine wound healing data over a 21-day healing period. The calibrated model recapitulates the temporal evolution of: inflammatory signal, fibroblast infiltration, collagen buildup, and wound contraction. Moreover, it enables in silico hypothesis testing, which we explore by: (i) quantifying the alteration of wound contraction profiles corresponding to the measured variability in local wound stiffness; (ii) proposing alternative constitutive links connecting the dynamics of the biochemical fields to the evolving mechanical properties; (iii) discussing the plausibility of a stretch- vs. stiffness-mediated mechanobiological coupling. Ultimately, our model challenges the current understanding of wound biomechanics and mechanobiology, beside offering a versatile tool to explore and eventually control scar fibrosis after injury.
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Affiliation(s)
- Marco Pensalfini
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, United States of America
- Institute for Mechanical Systems (IMES), Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland
- Laboratori de Càlcul Numèric (LaCàN), Universitat Politècnica de Catalunya-BarcelonaTech, Barcelona, Spain
| | - Adrian Buganza Tepole
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, United States of America
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, United States of America
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14
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Arnold N, Scott J, Bush TR. A review of the characterizations of soft tissues used in human body modeling: Scope, limitations, and the path forward. J Tissue Viability 2023; 32:286-304. [PMID: 36878737 DOI: 10.1016/j.jtv.2023.02.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 02/06/2023] [Accepted: 02/10/2023] [Indexed: 02/27/2023]
Abstract
Soft tissue material properties are vital to human body models that evaluate interactions between the human body and its environment. Such models evaluate internal stress/strain responses in soft tissues to investigate issues like pressure injuries. Numerous constitutive models and parameters have been used to represent mechanical behavior of soft tissues in biomechanical models under quasi-static loading. However, researchers reported that generic material properties cannot accurately represent specific target populations due to large inter-individual variability. Two challenges that exist are experimental mechanical characterization and constitutive modeling of biological soft tissues and personalization of constitutive parameters using non-invasive, non-destructive bedside testing methods. It is imperative to understand the scope and appropriate applications for reported material properties. Thus, the goal of this paper was to compile studies from which soft tissue material properties were obtained and categorize them by source of tissue samples, methods used to quantify deformation, and material models used to describe tissues. The collected studies displayed wide ranges of material properties, and factors that affected the properties included whether tissue samples were in vivo or ex vivo, from humans or animals, the body region tested, body position during in vivo studies, deformation measurements, and material models used to describe tissues. Because of the factors that affected reported material properties, it is clear that much progress has been made in understanding soft tissue responses to loading, yet there is a need to broaden the scope of reported soft tissue material properties and better match reported properties to appropriate human body models.
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Affiliation(s)
- Nicole Arnold
- Department of Mechanical Engineering, Michigan State University, 428 S Shaw Lane, Rm. 2555 Engineering Building, East Lansing, MI, 48824-1226, USA
| | - Justin Scott
- Department of Mechanical Engineering, Michigan State University, 428 S Shaw Lane, Rm. 2555 Engineering Building, East Lansing, MI, 48824-1226, USA
| | - Tamara Reid Bush
- Department of Mechanical Engineering, Michigan State University, 428 S Shaw Lane, Rm. 2555 Engineering Building, East Lansing, MI, 48824-1226, USA.
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15
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de Lucio M, Leng Y, Hans A, Bilionis I, Brindise M, Ardekani AM, Vlachos PP, Gomez H. Modeling large-volume subcutaneous injection of monoclonal antibodies with anisotropic porohyperelastic models and data-driven tissue layer geometries. J Mech Behav Biomed Mater 2023; 138:105602. [PMID: 36529050 DOI: 10.1016/j.jmbbm.2022.105602] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 11/22/2022] [Accepted: 11/29/2022] [Indexed: 12/13/2022]
Abstract
Subcutaneous injection of therapeutic monoclonal antibodies (mAbs) has become one of the fastest-growing fields in the pharmaceutical industry. The transport and mechanical processes behind large volume injections are poorly understood. Here, we leverage a large-deformation poroelastic model to study high-dose, high-speed subcutaneous injection. We account for the anisotropy of subcutaneous tissue using of a fibril-reinforced porohyperelastic model. We also incorporate the multi-layer structure of the skin tissue, generating data-driven geometrical models of the tissue layers using histological data. We analyze the impact of handheld autoinjectors on the injection dynamics for different patient forces. Our simulations show the importance of considering the large deformation approach to model large injection volumes. This work opens opportunities to better understand the mechanics and transport processes that occur in large-volume subcutaneous injections of mAbs.
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Affiliation(s)
- Mario de Lucio
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette IN 47907, USA
| | - Yu Leng
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette IN 47907, USA
| | - Atharva Hans
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette IN 47907, USA
| | - Ilias Bilionis
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette IN 47907, USA
| | - Melissa Brindise
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette IN 47907, USA
| | - Arezoo M Ardekani
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette IN 47907, USA
| | - Pavlos P Vlachos
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette IN 47907, USA
| | - Hector Gomez
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette IN 47907, USA.
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16
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Larsson KJ, Iraeus J, Holcombe S, Pipkorn B. Influences of human thorax variability on population rib fracture risk prediction using human body models. Front Bioeng Biotechnol 2023; 11:1154272. [PMID: 37034266 PMCID: PMC10078960 DOI: 10.3389/fbioe.2023.1154272] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 03/10/2023] [Indexed: 04/11/2023] Open
Abstract
Rib fractures remain a common injury for vehicle occupants in crashes. The risk of a human sustaining rib fractures from thorax loading is highly variable, potentially due to a variability in individual factors such as material properties and geometry of the ribs and ribcage. Human body models (HBMs) with a detailed ribcage can be used as occupant substitutes to aid in the prediction of rib injury risk at the tissue level in crash analysis. To improve this capability, model parametrization can be used to represent human variability in simulation studies. The aim of this study was to identify the variations in the physical properties of the human thorax that have the most influence on rib fracture risk for the population of vehicle occupants. A total of 15 different geometrical and material factors, sourced from published literature, were varied in a parametrized SAFER HBM. Parametric sensitivity analyses were conducted for two crash configurations, frontal and near-side impacts. The results show that variability in rib cortical bone thickness, rib cortical bone material properties, and rib cross-sectional width had the greatest influence on the risk for an occupant to sustain two or more fractured ribs in both impacts. Therefore, it is recommended that these three parameters be included in rib fracture risk analysis with HBMs for the population of vehicle occupants.
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Affiliation(s)
- Karl-Johan Larsson
- Autoliv Research, Vårgårda, Sweden
- Division of Vehicle Safety, Department of Mechanics and Maritime Sciences, Chalmers University of Technology, Gothenburg, Sweden
- *Correspondence: Karl-Johan Larsson,
| | - Johan Iraeus
- Division of Vehicle Safety, Department of Mechanics and Maritime Sciences, Chalmers University of Technology, Gothenburg, Sweden
| | - Sven Holcombe
- International Center for Automotive Medicine, University of Michigan, Ann Arbor, MI, United States
| | - Bengt Pipkorn
- Autoliv Research, Vårgårda, Sweden
- Division of Vehicle Safety, Department of Mechanics and Maritime Sciences, Chalmers University of Technology, Gothenburg, Sweden
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17
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Leng Y, Wang H, de Lucio M, Gomez H. Mixed-dimensional multi-scale poroelastic modeling of adipose tissue for subcutaneous injection. Biomech Model Mechanobiol 2022; 21:1825-1840. [PMID: 36057050 PMCID: PMC9440471 DOI: 10.1007/s10237-022-01622-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 08/02/2022] [Indexed: 11/28/2022]
Abstract
Subcutaneous injection of therapeutic monoclonal antibodies (mAbs) has gained increasing interest in the pharmaceutical industry. The transport, distribution and absorption of mAbs in the skin after injection are not yet well-understood. Experiments have shown that fibrous septa form preferential channels for fluid flow in the tissue. The majority of mAbs can only be absorbed through lymphatics which follow closely the septa network. Therefore, studying drug transport in the septa network is vital to the understanding of drug absorption. In this work, we present a mixed-dimensional multi-scale (MDMS) poroelastic model of adipose tissue for subcutaneous injection. More specifically, we model the fibrous septa as reduced-dimensional microscale interfaces embedded in the macroscale tissue matrix. The model is first verified by comparing numerical results against the full-dimensional model where fibrous septa are resolved using fine meshes. Then, we apply the MDMS model to study subcutaneous injection. It is found that the permeability ratio between the septa and matrix, volume capacity of the septa network, and concentration-dependent drug viscosity are important factors affecting the amount of drug entering the septa network which are paths to lymphatics. Our results show that septa play a critical role in the transport of mAbs in the subcutaneous tissue, and this role was previously overlooked.
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Affiliation(s)
- Yu Leng
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, 47907, USA.
| | - Hao Wang
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Mario de Lucio
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Hector Gomez
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, 47907, USA
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18
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Albrecht FB, Schmidt FF, Volz AC, Kluger PJ. Bioprinting of 3D Adipose Tissue Models Using a GelMA-Bioink with Human Mature Adipocytes or Human Adipose-Derived Stem Cells. Gels 2022; 8:gels8100611. [PMID: 36286112 PMCID: PMC9601941 DOI: 10.3390/gels8100611] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 09/21/2022] [Accepted: 09/21/2022] [Indexed: 12/31/2022] Open
Abstract
Adipose tissue is related to the development and manifestation of multiple diseases, demonstrating the importance of suitable in vitro models for research purposes. In this study, adipose tissue lobuli were explanted, cultured, and used as an adipose tissue control to evaluate in vitro generated adipose tissue models. During culture, lobule exhibited a stable weight, lactate dehydrogenase, and glycerol release over 15 days. For building up in vitro adipose tissue models, we adapted the biomaterial gelatin methacryloyl (GelMA) composition and handling to homogeneously mix and bioprint human primary mature adipocytes (MA) and adipose-derived stem cells (ASCs), respectively. Accelerated cooling of the bioink turned out to be essential for the homogeneous distribution of lipid-filled MAs in the hydrogel. Last, we compared manual and bioprinted GelMA hydrogels with MA or ASCs and the explanted lobules to evaluate the impact of the printing process and rate the models concerning the physiological reference. The viability analyses demonstrated no significant difference between the groups due to additive manufacturing. The staining of intracellular lipids and perilipin A suggest that GelMA is well suited for ASCs and MA. Therefore, we successfully constructed physiological in vitro models by bioprinting MA-containing GelMA bioinks.
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Affiliation(s)
- Franziska B. Albrecht
- Reutlingen Research Institute, Reutlingen University, 72762 Reutlingen, Germany
- Faculty of Natural Science, University of Hohenheim, 70599 Stuttgart, Germany
| | - Freia F. Schmidt
- Reutlingen Research Institute, Reutlingen University, 72762 Reutlingen, Germany
| | - Ann-Cathrin Volz
- Reutlingen Research Institute, Reutlingen University, 72762 Reutlingen, Germany
| | - Petra J. Kluger
- Faculty of Applied Chemistry, Reutlingen University, 72762 Reutlingen, Germany
- Correspondence: ; Tel.: +49-7121-271-2061
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19
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Mechanical Behavior of Subcutaneous and Visceral Abdominal Adipose Tissue in Patients with Obesity. Processes (Basel) 2022. [DOI: 10.3390/pr10091798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The mechanical characterization of adipose tissues is important for various medical purposes, including plastic surgery and biomechanical applications, such as computational human body models for the simulation of surgical procedures or injury prediction, for example, in the evaluation of vehicle crashworthiness. In this context, the measurement of human subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) mechanical properties in relation to subject characteristics may be really relevant. The aim of this work was to properly characterize the mechanical response of adipose tissues in patients with obesity. Then, the data were exploited to develop a reliable finite element model of the adipose tissues characterized by a constitutive material model that accounted for nonlinear elasticity and time dependence. Mechanical tests have been performed on both SAT and VAT specimens, which have been harvested from patients with severe obesity during standard laparoscopic sleeve gastrectomy intervention. The experimental campaign included indentation tests, which permitted us to obtain the initial/final indentation stiffnesses for each specimen. Statistical results revealed a higher statistical stiffness in SAT than in VAT, with an initial/final indentation stiffness of 1.65 (SD ± 0.29) N/30.30 (SD ± 20) N compared to 1.29 (SD ± 0.30) N/21.00 (SD ± 16) N. Moreover, the results showed that gender, BMI, and age did not significantly affect the stiffness. The experimental results were used in the identification of the constitutive parameters to be inserted in the constitutive material model. Such constitutive characterization of VAT and SAT mechanics can be the starting point for the future development of more accurate computational models of the human adipose tissue and, in general, of the human body for the optimization of numerous medical and biomechanical procedures and applications.
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20
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Fougeron N, Connesson N, Chagnon G, Alonso T, Pasquinet L, Bahuon M, Guillin E, Perrier A, Payan Y. New pressure ulcers dressings to alleviate human soft tissues: A finite element study. J Tissue Viability 2022; 31:506-513. [DOI: 10.1016/j.jtv.2022.05.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 05/11/2022] [Accepted: 05/20/2022] [Indexed: 10/18/2022]
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21
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The effects of gravity and compression on interstitial fluid transport in the lower limb. Sci Rep 2022; 12:4890. [PMID: 35318426 PMCID: PMC8941011 DOI: 10.1038/s41598-022-09028-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 03/14/2022] [Indexed: 11/13/2022] Open
Abstract
Edema in the limbs can arise from pathologies such as elevated capillary pressures due to failure of venous valves, elevated capillary permeability from local inflammation, and insufficient fluid clearance by the lymphatic system. The most common treatments include elevation of the limb, compression wraps and manual lymphatic drainage therapy. To better understand these clinical situations, we have developed a comprehensive model of the solid and fluid mechanics of a lower limb that includes the effects of gravity. The local fluid balance in the interstitial space includes a source from the capillaries, a sink due to lymphatic clearance, and movement through the interstitial space due to both gravity and gradients in interstitial fluid pressure (IFP). From dimensional analysis and numerical solutions of the governing equations we have identified several parameter groups that determine the essential length and time scales involved. We find that gravity can have dramatic effects on the fluid balance in the limb with the possibility that a positive feedback loop can develop that facilitates chronic edema. This process involves localized tissue swelling which increases the hydraulic conductivity, thus allowing the movement of interstitial fluid vertically throughout the limb due to gravity and causing further swelling. The presence of a compression wrap can interrupt this feedback loop. We find that only by modeling the complex interplay between the solid and fluid mechanics can we adequately investigate edema development and treatment in a gravity dependent limb.
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22
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Unamuno X, Gómez-Ambrosi J, Becerril S, Álvarez-Cienfuegos FJ, Ramírez B, Rodríguez A, Ezquerro S, Valentí V, Moncada R, Mentxaka A, Llorente M, Silva C, Elizalde MDLR, Catalán V, Frühbeck G. Changes in mechanical properties of adipose tissue after bariatric surgery driven by extracellular matrix remodelling and neovascularization are associated with metabolic improvements. Acta Biomater 2022; 141:264-279. [PMID: 35007786 DOI: 10.1016/j.actbio.2022.01.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 01/03/2022] [Accepted: 01/04/2022] [Indexed: 02/08/2023]
Abstract
Biomechanical properties of adipose tissue (AT) are closely involved in the development of obesity-associated comorbidities. Bariatric surgery (BS) constitutes the most effective option for a sustained weight loss in addition to improving obesity-associated metabolic diseases including type 2 diabetes (T2D). We aimed to determine the impact of weight loss achieved by BS and caloric restriction (CR) on the biomechanical properties of AT. BS but not CR changed the biomechanical properties of epididymal white AT (EWAT) from a diet-induced obesity rat model, which were associated with metabolic improvements. We found decreased gene expression levels of collagens and Lox together with increased elastin and Mmps mRNA levels in EWAT after BS, which were also associated with the biomechanical properties. Moreover, an increased blood vessel density was observed in EWAT after surgery, confirmed by an upregulation of Acta2 and Antxr1 gene expression levels, which was also correlated with the biomechanical properties. Visceral AT from patients with obesity showed increased stiffness after tensile tests compared to the EWAT from the animal model. This study uncovers new insights into EWAT adaptation after BS with decreased collagen crosslink and synthesis as well as an increased degradation together with enhanced blood vessel density providing, simultaneously, higher stiffness and more ductility. STATEMENT OF SIGNIFICANCE: Biomechanical properties of the adipose tissue (AT) are closely involved in the development of obesity-associated comorbidities. In this study, we show for the first time that biomechanical properties of AT determined by E, UTS and strain at UTS are decreased in obesity, being increased after bariatric surgery by the promotion of ECM remodelling and neovascularization. Moreover, these changes in biomechanical properties are associated with improvements in metabolic homeostasis. Consistently, a better characterization of the plasticity and biomechanical properties of the AT after bariatric surgery opens up a new field for the development of innovative strategies for the reduction of fibrosis and inflammation in AT as well as to better understand obesity and its associated comorbidities.
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23
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Fontanella CG, Belluzzi E, Pozzuoli A, Favero M, Ruggieri P, Macchi V, Carniel EL. Mechanical behavior of infrapatellar fat pad of patients affected by osteoarthritis. J Biomech 2021; 131:110931. [PMID: 34972018 DOI: 10.1016/j.jbiomech.2021.110931] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 11/19/2021] [Accepted: 12/19/2021] [Indexed: 01/14/2023]
Abstract
The infrapatellar fat pad (IFP) is an adipose tissue present in the knee that lies between the patella, femur, meniscus and tibia, filling the space between these structures. IFP facilitates the distribution of the synovial fluid and may act to absorb impulsive actions generated through the joint. IFP in osteoarthritis (OA) pathology undergoes structural changes characterized by inflammation, hypertrophy and fibrosis. The aim of the present study is to analyze the mechanical behavior of the IFP in patients affected by end-stage OA. A specific test fixture was designed and indentation tests were performed on IFP specimens harvested from OA patients who underwent total knee arthroplasty. Experiments allowed to assess the typical features of mechanical response, such as non-linear stress-strain behavior and time-dependent effects. Results from mechanical experimentations were implemented within the framework of a visco-hyperelastic constitutive theory, with the aim to provide data for computational modelling of OA IFP role in knee mechanics. Initial and final indentation stiffness were calculated for all subjects and statistical results reveled that OA IFP mechanics was not significantly influenced by gender, BMI and sample preparation. OA IFP mechanical behavior was also compared to that of other adipose tissues. OA IFP appeared to be a stiffer adipose tissue compared to subcutaneous, visceral adipose tissues and heel fat pads. It is reasonable that fibrosis induces a modification of the tissue destabilizing the normal distribution of forces in the joint during movement, causing a worsening of the disease.
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Affiliation(s)
- Chiara Giulia Fontanella
- Department of Industrial Engineering, University of Padova, 35131 Padova, Italy; Centre for Mechanics of Biological Materials, University of Padova, 35131 Padova, Italy
| | - Elisa Belluzzi
- Musculoskeletal Pathology and Oncology Laboratory, Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padova, 35128 Padova, Italy; Orthopedics and Orthopedic Oncology, Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padova, 35128 Padova, Italy.
| | - Assunta Pozzuoli
- Musculoskeletal Pathology and Oncology Laboratory, Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padova, 35128 Padova, Italy; Orthopedics and Orthopedic Oncology, Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padova, 35128 Padova, Italy
| | - Marta Favero
- Rheumatology Unit, Department of Medicine-DIMED, University-Hospital of Padova, 35128 Padova, Italy; Internal Medicine I, Cà Foncello Hospital, 31100 Treviso, Italy
| | - Pietro Ruggieri
- Orthopedics and Orthopedic Oncology, Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padova, 35128 Padova, Italy
| | - Veronica Macchi
- Centre for Mechanics of Biological Materials, University of Padova, 35131 Padova, Italy; Department of Neurosciences, Institute of Human Anatomy, University of Padova, 35121 Padova, Italy
| | - Emanuele Luigi Carniel
- Department of Industrial Engineering, University of Padova, 35131 Padova, Italy; Centre for Mechanics of Biological Materials, University of Padova, 35131 Padova, Italy
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24
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Experimental characterisation of porcine subcutaneous adipose tissue under blunt impact up to irreversible deformation. Int J Legal Med 2021; 136:897-910. [PMID: 34862924 PMCID: PMC9005403 DOI: 10.1007/s00414-021-02755-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 11/26/2021] [Indexed: 12/04/2022]
Abstract
A deeper understanding of the mechanical characteristics of adipose tissue under large deformation is important for the analysis of blunt force trauma, as adipose tissue alters the stresses and strains that are transferred to subjacent tissues. Hence, results from drop tower tests of subcutaneous adipose tissue are presented (i) to characterise adipose tissue behaviour up to irreversible deformation, (ii) to relate this to the microstructural configuration, (iii) to quantify this deformation and (iv) to provide an analytical basis for computational modelling of adipose tissue under blunt impact. The drop tower experiments are performed exemplarily on porcine subcutaneous adipose tissue specimens for three different impact velocities and two impactor geometries. An approach based on photogrammetry is used to derive 3D representations of the deformation patterns directly after the impact. Median values for maximum impactor acceleration for tests with a flat cylindrical impactor geometry at impact velocities of 886 mm/s, 1253 mm/s and 2426 mm/s amount to 61.1 g, 121.6 g and 264.2 g, respectively, whereas thickness reduction of the specimens after impact amount to 16.7%, 30.5% and 39.3%, respectively. The according values for tests with a spherically shaped impactor at an impact velocity of 1253 mm/s are 184.2 g and 78.7%. Based on these results, it is hypothesised that, in the initial phase of a blunt impact, adipose tissue behaviour is mainly governed by the behaviour of the lipid inside the adipocytes, whereas for further loading, contribution of the extracellular collagen fibre network becomes more dominant.
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25
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Zhong H, Li Z, Zhao T, Chen Y. Surface Modification of Nanofibers by Physical Adsorption of Fiber-Homologous Amphiphilic Copolymers and Nanofiber-Reinforced Hydrogels with Excellent Tissue Adhesion. ACS Biomater Sci Eng 2021; 7:4828-4837. [PMID: 34478620 DOI: 10.1021/acsbiomaterials.1c00982] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Herein, we report a simple approach to modify hydrophobic PCL nanofibers by adsorption of a fiber-homologous amphiphilic triblock copolymer (PCL-b-PEG-b-PCL, PCEC). The modified PCL nanofibers were then utilized to reinforce a physical hydrogel, which was formed by micellar crosslinking of the same PCEC triblock copolymer. Therefore, the copolymer played a dual role in not only dispersing and stabilizing nanofibers but also additionally providing a framework for the hydrogel matrix. The mechanical strength of the hydrogel was significantly enhanced by addition of the modified PCL nanofibers, and the gel modulus can be tuned by varying the concentration of the copolymer and nanofibers. The effect of nanofiber size and content on the mechanical properties of the hydrogel matrices was studied. Different from hydrogel composites that were reinforced by 2D fiber meshes or 3D woven fiber networks, this free fiber-reinforced hydrogel can be readily injected to adapt to the environmental shape and self-heal. The hydrogel composites showed superior tissue adhesion properties compared to the commercially available fibrin glue, especially in muscle adhesion. Due to its injectable and self-healing properties, this nanofiber-reinforced hydrogel may have great potential as a new type of tissue sealant.
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Affiliation(s)
- Hai Zhong
- School of Materials Science and Engineering, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, Sun Yat-sen University, Guangzhou 510275, China
| | - Zhiyong Li
- Nepgel Chemical Co., Ltd., No. 127, China South-City Industrial Zone, Longgang District, Shenzhen 518111, China
| | - Tianyu Zhao
- School of Materials Science and Engineering, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, Sun Yat-sen University, Guangzhou 510275, China
| | - Yongming Chen
- School of Materials Science and Engineering, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, Sun Yat-sen University, Guangzhou 510275, China
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26
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Reye G, Huang X, Haupt LM, Murphy RJ, Northey JJ, Thompson EW, Momot KI, Hugo HJ. Mechanical Pressure Driving Proteoglycan Expression in Mammographic Density: a Self-perpetuating Cycle? J Mammary Gland Biol Neoplasia 2021; 26:277-296. [PMID: 34449016 PMCID: PMC8566410 DOI: 10.1007/s10911-021-09494-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 07/05/2021] [Indexed: 12/23/2022] Open
Abstract
Regions of high mammographic density (MD) in the breast are characterised by a proteoglycan (PG)-rich fibrous stroma, where PGs mediate aligned collagen fibrils to control tissue stiffness and hence the response to mechanical forces. Literature is accumulating to support the notion that mechanical stiffness may drive PG synthesis in the breast contributing to MD. We review emerging patterns in MD and other biological settings, of a positive feedback cycle of force promoting PG synthesis, such as in articular cartilage, due to increased pressure on weight bearing joints. Furthermore, we present evidence to suggest a pro-tumorigenic effect of increased mechanical force on epithelial cells in contexts where PG-mediated, aligned collagen fibrous tissue abounds, with implications for breast cancer development attributable to high MD. Finally, we summarise means through which this positive feedback mechanism of PG synthesis may be intercepted to reduce mechanical force within tissues and thus reduce disease burden.
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Affiliation(s)
- Gina Reye
- School of Biomedical Sciences, Gardens Point, Queensland University of Technology (QUT), Kelvin Grove, QLD, 4059, Australia
- Translational Research Institute, Woolloongabba, QLD, Australia
| | - Xuan Huang
- School of Biomedical Sciences, Gardens Point, Queensland University of Technology (QUT), Kelvin Grove, QLD, 4059, Australia
- Translational Research Institute, Woolloongabba, QLD, Australia
| | - Larisa M Haupt
- Centre for Genomics and Personalised Health, Genomics Research Centre, School of Biomedical Sciences, Faculty of Health, Institute of Health and Biomedical Innovation, Queensland University of Technology (QUT), 60 Musk Ave, Kelvin Grove, QLD, 4059, Australia
| | - Ryan J Murphy
- School of Mathematical Sciences, Gardens Point, Queensland University of Technology (QUT), Kelvin Grove, QLD, Australia
| | - Jason J Northey
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Erik W Thompson
- School of Biomedical Sciences, Gardens Point, Queensland University of Technology (QUT), Kelvin Grove, QLD, 4059, Australia
- Translational Research Institute, Woolloongabba, QLD, Australia
| | - Konstantin I Momot
- School of Chemistry and Physics, Queensland University of Technology (QUT), Brisbane, QLD, Australia
| | - Honor J Hugo
- School of Biomedical Sciences, Gardens Point, Queensland University of Technology (QUT), Kelvin Grove, QLD, 4059, Australia.
- Translational Research Institute, Woolloongabba, QLD, Australia.
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27
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Liu H, Jain S, Ahlinder A, Fuoco T, Gasser TC, Finne-Wistrand A. Pliable, Scalable, and Degradable Scaffolds with Varying Spatial Stiffness and Tunable Compressive Modulus Produced by Adopting a Modular Design Strategy at the Macrolevel. ACS POLYMERS AU 2021; 1:107-122. [PMID: 36855428 PMCID: PMC9954393 DOI: 10.1021/acspolymersau.1c00013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Clinical results obtained when degradable polymer-based medical devices are used in breast reconstruction following mastectomy are promising. However, it remains challenging to develop a large scaffold structure capable of providing both sufficient external mechanical support and an internal cell-like environment to support breast tissue regeneration. We propose an internal-bra-like prototype to solve both challenges. The design combines a 3D-printed scaffold with knitted meshes and electrospun nanofibers and has properties suitable for both breast tissue regeneration and support of a silicone implant. Finite element analysis (FEA) was used to predict the macroscopic and microscopic stiffnesses of the proposed structure. The simulations show that introduction of the mesh leads to a macroscopic scaffold stiffness similar to the stiffness of breast tissue, and mechanical testing confirms that the introduction of more layers of mesh in the modular design results in a lower elastic modulus. The compressive modulus of the scaffold can be tailored within a range from hundreds of kPa to tens of kPa. Biaxial tensile testing reveals stiffening with increasing strain and indicates that rapid strain-induced softening occurs only within the first loading cycle. In addition, the microscopic local stiffness obtained from FEA simulations indicates that cells experience significant heterogeneous mechanical stimuli at different places in the scaffold and that the local mechanical stimulus generated by the strand surface is controlled by the elastic modulus of the polymer, rather than by the scaffold architecture. From in vitro experiments, it was observed that the addition of knitted mesh and an electrospun nanofiber layer to the scaffold significantly increased cell seeding efficiency, cell attachment, and proliferation compared to the 3D-printed scaffold alone. In summary, our results suggest that the proposed design strategy is promising for soft tissue engineering of scaffolds to assist breast reconstruction and regeneration.
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Affiliation(s)
- Hailong Liu
- Department
of Fibre and Polymer Technology, KTH Royal
Institute of Technology, 100 44, Stockholm, Sweden,Department
of Engineering Mechanics, KTH Royal Institute
of Technology, 100 44, Stockholm, Sweden
| | - Shubham Jain
- Department
of Fibre and Polymer Technology, KTH Royal
Institute of Technology, 100 44, Stockholm, Sweden
| | - Astrid Ahlinder
- Department
of Fibre and Polymer Technology, KTH Royal
Institute of Technology, 100 44, Stockholm, Sweden
| | - Tiziana Fuoco
- Department
of Fibre and Polymer Technology, KTH Royal
Institute of Technology, 100 44, Stockholm, Sweden
| | - T. Christian Gasser
- Solid
Mechanics, Department of Engineering Mechanics, KTH Royal Institute of Technology, 100 44, Stockholm, Sweden,Faculty
of Health Sciences, University of Southern
Denmark, 5230, Odense, Denmark,
| | - Anna Finne-Wistrand
- Department
of Fibre and Polymer Technology, KTH Royal
Institute of Technology, 100 44, Stockholm, Sweden,
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28
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Bodner J, Baxter W, Leung C, Falkner P. A New Medical Device Modeling Framework for Predicting the Performance of Indwelling Continence Care Devices and Improving Patient Care. J Med Device 2021. [DOI: 10.1115/1.4051441] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Abstract
A computational model of the human torso has been developed to study the stability of implanted leads that are part of a sacral nerve stimulation system. The model was built using presegmented anatomies that were themselves built from imaging of human patients. The sacral leads are represented using beam elements, and their interaction with the tissue is defined using a function that relates frictional force to the amount of slip between the lead and tissue. Displacements to the skin in the sacral region are applied to simulate activities of daily living, and the resulting displacement of the tip of the lead is indicative of its tendency to dislodge in real patients. Validation of the model was performed using experimental results collected in human cadavers. In these experiments, analogous displacements of the skin were applied after implantation of the leads per normal implant procedures. The displacement of the distal tip of the lead was measured using computed tomography (CT) imaging, allowing direct comparison to the predictions of the model. Recognizing that many model inputs were informed by sparse literature values, a novel application of uncertainty quantification methodology was developed wherein all model inputs were treated as uncertain intervals. This allowed an optimization approach to be used for estimating the uncertain interval for the model outputs. The computational model and cadaver results were used to study the performance of a new sacral lead design, relative to a predicate product. The results showed that the reduction in lead axial stiffness in the new design leads to less lead tip displacement, such that the lead is more likely to remain near the therapeutic target in patients.
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Affiliation(s)
- Jeff Bodner
- Neuromodulation Operating Unit, Medtronic, plc, Minneapolis, MN 55432
| | - Walt Baxter
- Neuromodulation Operating Unit, Medtronic, plc, Santa Ana, CA 92705
| | - Christina Leung
- Neuromodulation Operating Unit, Medtronic, plc, Santa Ana, CA 92705
| | - Phillip Falkner
- Neuromodulation Operating Unit, Medtronic, plc, Minneapolis, MN 55432
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29
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Sun Z, Gepner BD, Lee SH, Rigby J, Cottler PS, Hallman JJ, Kerrigan JR. Multidirectional mechanical properties and constitutive modeling of human adipose tissue under dynamic loading. Acta Biomater 2021; 129:188-198. [PMID: 34048975 DOI: 10.1016/j.actbio.2021.05.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 05/02/2021] [Accepted: 05/17/2021] [Indexed: 02/07/2023]
Abstract
The mechanical behavior of subcutaneous adipose tissue (SAT) affects the interaction between vehicle occupants and restraint systems in motor vehicle crashes (MVCs). To enhance future restraints, injury countermeasures, and other vehicle safety systems, computational simulations are often used to augment experiments because of their relative efficiency for parametric analysis. How well finite element human body models (FE-HBMs), which are often used in such simulations, predict human response has been limited by the absence of material models for human SAT that are applicable to the MVC environment. In this study, for the first time, dynamic multidirectional unconfined compression and simple shear loading tests were performed on human abdominal SAT specimens under conditions similar to MVCs. We also performed multiple ramp-hold tests to evaluate the quasilinear viscoelasticity (QLV) assumption and capture the stress relaxation behavior under both compression and shear. Our mechanical characterization was supplemented with scanning electron microscopy (SEM) performed in different orientations to investigate whether the macrostructural response can be related to the underlying microstructure. While the overall structure was shown to be visually different in different anatomical planes, a preferred orientation of any fibrous structures could not be identified. We showed that the nonlinear, viscoelastic, and direction-dependent responses under compression and shear tests could be captured by incorporating QLV in an Ogden-type hyperelastic model. Our comprehensive approach will lead to more accurate computational simulations and support the collective effort on the research of future occupant protection systems. STATEMENT OF SIGNIFICANCE: There is an urgent need to characterize the mechanical behavior of human adipose tissue under multiple dynamic loading conditions, and to identify constitutive models that are able to capture the tissue response under these conditions. We performed the first series of experiments on human adipose tissue specimens to characterize the multi-directional compression and shear behavior at impact loading rates and obtained scanning electron microscope images to investigate whether the macrostructural response can be related to the underlying microstructure. The results showed that human adipose tissue is nonlinear, viscoelastic and direction dependent, and its mechanical response under compression and shear tests at different loading rates can be captured by incorporating quasi-linear viscoelasticity in an Ogden-type hyperelastic model.
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30
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Sun Z, Gepner BD, Cottler PS, Lee SH, Kerrigan JR. In Vitro Mechanical Characterization and Modeling of Subcutaneous Adipose Tissue: A Comprehensive Review. J Biomech Eng 2021; 143:070803. [PMID: 33625495 DOI: 10.1115/1.4050286] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Indexed: 11/08/2022]
Abstract
Mechanical models of adipose tissue are important for various medical applications including cosmetics, injuries, implantable drug delivery systems, plastic surgeries, biomechanical applications such as computational human body models for surgery simulation, and blunt impact trauma prediction. This article presents a comprehensive review of in vivo experimental approaches that aimed to characterize the mechanical properties of adipose tissue, and the resulting constitutive models and model parameters identified. In particular, this study examines the material behavior of adipose tissue, including its nonlinear stress-strain relationship, viscoelasticity, strain hardening and softening, rate-sensitivity, anisotropy, preconditioning, failure behavior, and temperature dependency.
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Affiliation(s)
- Zhaonan Sun
- Center for Applied Biomechanics, University of Virginia, Charlottesville, VA 22911
| | - Bronislaw D Gepner
- Center for Applied Biomechanics, University of Virginia, Charlottesville, VA 22911
| | - Patrick S Cottler
- Department of Plastic Surgery, University of Virginia, Charlottesville, VA 22903
| | - Sang-Hyun Lee
- Center for Applied Biomechanics, University of Virginia, Charlottesville, VA 22911
| | - Jason R Kerrigan
- Center for Applied Biomechanics, University of Virginia, Charlottesville, VA 22911
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31
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Sachs D, Wahlsten A, Kozerke S, Restivo G, Mazza E. A biphasic multilayer computational model of human skin. Biomech Model Mechanobiol 2021; 20:969-982. [PMID: 33566274 PMCID: PMC8154831 DOI: 10.1007/s10237-021-01424-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 01/12/2021] [Indexed: 11/26/2022]
Abstract
The present study investigates the layer-specific mechanical behavior of human skin. Motivated by skin’s histology, a biphasic model is proposed which differentiates between epidermis, papillary and reticular dermis, and hypodermis. Inverse analysis of ex vivo tensile and in vivo suction experiments yields mechanical parameters for each layer and predicts a stiff reticular dermis and successively softer papillary dermis, epidermis and hypodermis. Layer-specific analysis of simulations underlines the dominating role of the reticular dermis in tensile loading. Furthermore, it shows that the observed out-of-plane deflection in ex vivo tensile tests is a direct consequence of the layered structure of skin. In in vivo suction experiments, the softer upper layers strongly influence the mechanical response, whose dissipative part is determined by interstitial fluid redistribution within the tissue. Magnetic resonance imaging-based visualization of skin deformation in suction experiments confirms the deformation pattern predicted by the multilayer model, showing a consistent decrease in dermal thickness for large probe opening diameters.
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Affiliation(s)
- David Sachs
- ETH Zurich, Institute for Mechanical Systems, Zürich, Switzerland
| | - Adam Wahlsten
- ETH Zurich, Institute for Mechanical Systems, Zürich, Switzerland
| | - Sebastian Kozerke
- University and ETH Zurich, Institute for Biomedical Engineering, Zürich, Switzerland
| | - Gaetana Restivo
- Department of Dermatology, University Hospital Zürich, Zürich, Switzerland
| | - Edoardo Mazza
- ETH Zurich, Institute for Mechanical Systems, Zürich, Switzerland
- EMPA, Swiss Federal Laboratories for Materials Science and Technology, Experimental Continuum Mechanics, Dübendorf, Switzerland
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32
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Sandulescu T, Weniger J, Philippou S, Mücke T, Naumova EA, Arnold WH. Immunohistochemical evidence of striated muscle cells within midfacial superficial musculoaponeurotic system. Ann Anat 2020; 234:151647. [PMID: 33221387 DOI: 10.1016/j.aanat.2020.151647] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Revised: 10/23/2020] [Accepted: 10/24/2020] [Indexed: 10/23/2022]
Abstract
INTRODUCTION The superficial musculoaponeurotic system (SMAS) is a controversial functional fibro-adipose layer that connects the mimic muscles to the skin and is involved in a variety of facial mimic expressions. The presence of muscle fibers within SMAS fibrous septa is hypothetical. The present study analyzed SMAS fibrous septa composition for the existence of striated muscle cells. METHODS Histological serial sections of the sample borders (n=107) of 19 in sano-resected and diagnosed cutaneous tumors of the midfacial region were investigated. Immunohistochemical (actin and myosin) and hematoxylin and eosin staining were performed to detect striated muscle cells in SMAS fibrous septa. RESULTS A fibro-neuro-musculo-vascular functional unit within SMAS fibrous septa was demonstrated. SMAS striated muscle cells were morphologically independent from preparotideal and periorbital mimic muscles. Intraseptal blood vessels draining the superficial and deep SMAS vascular system were described. CONCLUSIONS Striated muscle cells were demonstrated within SMAS fibrous septa. Nerve cells and vascular tissue together with the SMAS fibro-muscular meshwork demonstrated an autonomous operating functional unit that hypothetical modulated individual mimic expression contributing to the diversity of mimic expression. The SMAS develops with mimic muscle contractions as a synergetic effect during facial crease and fold formation processes.
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Affiliation(s)
- Tudor Sandulescu
- Department of Biological and Material Sciences in Dentistry, School of Dentistry, Faculty of Health, Witten/Herdecke University, Germany.
| | - Judith Weniger
- Department of Biological and Material Sciences in Dentistry, School of Dentistry, Faculty of Health, Witten/Herdecke University, Germany
| | - Stathis Philippou
- Department of Pathology and Cytology, Augusta Kliniken Bochum Hattingen, Bochum, Germany
| | - Thomas Mücke
- Department of Oral and Maxillofacial Surgery, Malteser Klinikum Krefeld-Uerdingen and Duisburg Homberg, Krefeld, Germany
| | - Ella A Naumova
- Department of Biological and Material Sciences in Dentistry, School of Dentistry, Faculty of Health, Witten/Herdecke University, Germany
| | - Wolfgang H Arnold
- Department of Biological and Material Sciences in Dentistry, School of Dentistry, Faculty of Health, Witten/Herdecke University, Germany
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33
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A versatile biaxial testing platform for soft tissues. J Mech Behav Biomed Mater 2020; 114:104144. [PMID: 33153924 DOI: 10.1016/j.jmbbm.2020.104144] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 09/02/2020] [Accepted: 10/14/2020] [Indexed: 11/20/2022]
Abstract
Uniaxial testing remains the most common modality of mechanical analysis for biological and other soft materials; however, biaxial testing enables a more comprehensive understanding of these materials' mechanical behavior. In recent years, a number of commercially available biaxial testing systems designed for biological materials have been produced; however, there are common limitations that are often associated with using these systems. For example, the range of allowable sample geometries are relatively constrained, the clamping systems are relatively limited with respect to allowable configurations, the load and displacement ranges are relatively small, and the software and control elements offer relatively limited options. Due to these constraints, there are significant benefits associated with designing custom biaxial testing systems that meet the technical requirements for testing a broad range of materials. Herein we present a design for a biaxial testing system with capabilities that extend beyond those associated with typical commercially available systems. Our design is capable of performing uniaxial tests, traditional biaxial tests, and double lap shear (simple shear) tests, in either a displacement or load control mode. Testing protocols have been developed and proof-of-concept experiments have been performed on commercially available silicone membranes and rat abdominal skin samples.
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34
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Comparison of porcine and human adipose tissue loading responses under dynamic compression and shear: A pilot study. J Mech Behav Biomed Mater 2020; 113:104112. [PMID: 33010697 DOI: 10.1016/j.jmbbm.2020.104112] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 09/17/2020] [Accepted: 09/21/2020] [Indexed: 11/21/2022]
Abstract
Understanding the mechanical properties of human adipose tissue, and its influence on seat belt-pelvis interaction is beneficial for computational human body models that are developed for injury prediction in the vehicle crashworthiness simulations. While various studies have characterized adipose tissue, most of the studies used porcine adipose tissue as a surrogate, and none of the studies were performed at loading rates relevant for motor vehicle collisions. In this work, the mechanical response of human and porcine adipose tissue was studied. Two dynamic loading modes (compression and simple shear) were tested in adipose tissue extracted from the human abdomen and porcine back. An Ogden hyperelastic model was used to fit the loading response, and specific material parameters were obtained for each specimen. Two-sample t-tests were performed to compare the effective shear moduli and peak stresses from porcine and human samples. The material response of the human adipose tissue was consistent with previous studies. Porcine adipose tissue was found to be significantly stiffer than human adipose tissue under compression and shear loading. Also, when material model parameters were fit to only one loading mode, the predicted response in the other mode showed a poor fit.
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35
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Naseri H, Iraeus J, Johansson H. The effect of adipose tissue material properties on the lap belt-pelvis interaction: A global sensitivity analysis. J Mech Behav Biomed Mater 2020; 107:103739. [DOI: 10.1016/j.jmbbm.2020.103739] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 02/03/2020] [Accepted: 02/26/2020] [Indexed: 11/16/2022]
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36
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Geith MA, Eckmann JD, Haspinger DC, Agrafiotis E, Maier D, Szabo P, Sommer G, Schratzenstaller TG, Holzapfel GA. Experimental and mathematical characterization of coronary polyamide-12 balloon catheter membranes. PLoS One 2020; 15:e0234340. [PMID: 32579587 PMCID: PMC7313739 DOI: 10.1371/journal.pone.0234340] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 05/23/2020] [Indexed: 11/18/2022] Open
Abstract
The experimental quantification and modeling of the multiaxial mechanical response of polymer membranes of coronary balloon catheters have not yet been carried out. Due to the lack of insights, it is not shown whether isotropic material models can describe the material response of balloon catheter membranes expanded with nominal or higher, supra-nominal pressures. Therefore, for the first time, specimens of commercial polyamide-12 balloon catheters membranes were investigated during uniaxial and biaxial loading scenarios. Furthermore, the influence of kinematic effects on the material response was observed by comparing results from quasi-static and dynamic biaxial extension tests. Novel clamping techniques are described, which allow to test even tiny specimens taken from the balloon membranes. The results of this study reveal the semi-compliant, nonlinear, and viscoelastic character of polyamide-12 balloon catheter membranes. Above nominal pressure, the membranes show a pronounced anisotropic mechanical behavior with a stiffer response in the circumferential direction. The anisotropic feature intensifies with an increasing strain-rate. A modified polynomial model was applied to represent the realistic mechanical response of the balloon catheter membranes during dynamic biaxial extension tests. This study also includes a compact set of constitutive model parameters for the use of the proposed model in future finite element analyses to perform more accurate simulations of expanding balloon catheters.
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Affiliation(s)
- Markus A. Geith
- Faculty of Computer Science and Biomedical Engineering, Institute of Biomechanics, Graz University of Technology, Graz, Austria
- Biomedical Engineering Department, King’s College London, London, United Kingdom
- * E-mail: (GAH); (MAG)
| | - Jakob D. Eckmann
- Faculty of Computer Science and Biomedical Engineering, Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | - Daniel Ch. Haspinger
- Faculty of Computer Science and Biomedical Engineering, Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | - Emmanouil Agrafiotis
- Faculty of Computer Science and Biomedical Engineering, Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | - Dominik Maier
- Faculty of Computer Science and Biomedical Engineering, Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | - Patrick Szabo
- Faculty of Computer Science and Biomedical Engineering, Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | - Gerhard Sommer
- Faculty of Computer Science and Biomedical Engineering, Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | - Thomas G. Schratzenstaller
- Medical Device Laboratory, Regensburg Center of Biomedical Engineering, Technical University of Applied Sciences Regensburg, Regensburg, Germany
| | - Gerhard A. Holzapfel
- Faculty of Computer Science and Biomedical Engineering, Institute of Biomechanics, Graz University of Technology, Graz, Austria
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
- * E-mail: (GAH); (MAG)
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37
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Chardon MK, Suresh NL, Dhaher YY, Rymer WZ. In-Vivo Study of Passive Musculotendon Mechanics in Chronic Hemispheric Stroke Survivors. IEEE Trans Neural Syst Rehabil Eng 2020; 28:1022-1031. [PMID: 32149642 PMCID: PMC7233468 DOI: 10.1109/tnsre.2020.2972206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We characterized the passive mechanical properties of the affected and contralateral musculotendon units in 9 chronic stroke survivors as well as in 6 neurologically-intact controls. Using a position-controlled motor, we precisely indented the distal tendon of the biceps brachii to a 20 mm depth from skin, recording both its sagittal motion using ultrasound movies and the compression force at the tip of the indenter. Length changes of 8 equally-spaced features along the aponeurosis axis were quantified using a pixel-tracking protocol. We report that, on the aggregate and with respect to contralateral and control, respectively, the affected side initiates feature motion at a shorter indentation distance by 61% and 50%, travels further by 15% and 9%, at a lower rate of 28% and 15%, and is stiffer by 40% and 57%. In an extended analysis including the spatial location of the 8 designated features, we report that in contrast to the contralateral and control muscles, the affected musculotendon unit does not strain measurably within the imaging window. These results confirm that chronic stroke-induced spasticity changes musculotendon unit passive mechanics, causing it to not strain under stretch. The mechanisms responsible for altered passive mechanics may lie within extracellular matrix fibrosis.
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38
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Towards microstructure-informed material models for human brain tissue. Acta Biomater 2020; 104:53-65. [PMID: 31887455 DOI: 10.1016/j.actbio.2019.12.030] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 12/19/2019] [Accepted: 12/20/2019] [Indexed: 02/06/2023]
Abstract
Emerging evidence suggests that the mechanical behavior of the brain plays a critical role in development, disease, and aging. Recent studies have begun to characterize the mechanical behavior of gray and white matter tissue and to identify sets of material models that best reproduce the stress-strain behavior of different brain regions. Yet, these models are mainly phenomenological in nature, their parameters often lack clear physical interpretation, and they fail to correlate the mechanical behavior to the underlying microstructural composition. Here we make a first attempt towards identifying general relations between microstructure and mechanics with the ultimate goal to develop microstructurally motivated constitutive equations for human brain tissue. Using histological staining, we analyze the microstructure of brain specimens from different anatomical regions, the cortex, basal ganglia, corona radiata, and corpus callosum, and identify the regional stiffness and viscosity under multiple loading conditions, simple shear, compression, and tension. Strikingly, our study reveals a negative correlation between cell count and stiffness, a positive correlation between myelin content and stiffness, and a negative correlation between proteoglycan content and stiffness. Additionally, our analysis shows a positive correlation between lipid and proteoglycan content and viscosity. We demonstrate how understanding the microstructural origin of the macroscopic behavior of the brain can help us design microstructure-informed material models for human brain tissue that inherently capture regional heterogeneities. This study represents an important step towards using brain tissue stiffness and viscosity as early diagnostic markers for clinical conditions including chronic traumatic encephalopathy, Alzheimer's and Parkinson's disease, or multiple sclerosis. STATEMENT OF SIGNIFICANCE: The complex and heterogeneous mechanical properties of brain tissue play a critical role for brain function. To understand and predict how brain tissue properties vary in space and time, it will be key to link the mechanical behavior to the underlying microstructural composition. Here we use histological staining to quantify area fractions of microstructural components of mechanically tested specimens and evaluate their individual contributions to the nonlinear macroscopic mechanical response. We further propose a microstructure-informed material model for human brain tissue that inherently captures regional heterogeneities. The current work provides unprecedented insights into the biomechanics of human brain tissue, which are highly relevant to develop refined computational models for brain tissue behavior or to advance neural tissue engineering.
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39
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He Z, Mongrain R, Lessard S, Chayer B, Cloutier G, Soulez G. Anthropomorphic and biomechanical mockup for abdominal aortic aneurysm. Med Eng Phys 2020; 77:60-68. [PMID: 31954613 DOI: 10.1016/j.medengphy.2019.12.005] [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: 03/27/2019] [Revised: 09/08/2019] [Accepted: 12/15/2019] [Indexed: 11/16/2022]
Abstract
Abdominal aortic aneurysm (AAA) is an asymptomatic condition due to the dilation of abdominal aorta along with progressive wall degeneration, where rupture of AAA is life-threatening. Failures of AAA endovascular repair (EVAR) reflect our inadequate knowledge about the complex interaction between the aortic wall and medical devices. In this regard, we are presenting a hydrogel-based anthropomorphic mockup (AMM) to better understand the biomechanical constraints during EVAR. By adjusting the cryogenic treatments, we tailored the hydrogel to mimic the mechanical behavior of human AAA wall, thrombus and abdominal fat. A specific molding sequence and a pressurizing system were designed to reproduce the geometrical and diseased characteristics of AAA. A mechanically, anatomically and pathologically realistic AMM for AAA was developed for the first time, EVAR experiments were then performed with and without the surrounding fat. Substantial displacements of the aortic centerlines and vessel expansion were observed in the case without surrounding fat, revealing an essential framework created by the surrounding fat to account for the interactions with medical devices. In conclusion, the importance to consider surrounding tissue for the global deformation of AAA during EVAR was highlighted. Furthermore, potential use of this AMM for medical training was also suggested.
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Affiliation(s)
- Zinan He
- McGill University, 845 Sherbrooke Street West, Montréal, Québec H3A 0G4, Canada; Centre de recherche du Centre hospitalier de l'Université de Montréal (CRCHUM), 900 Rue Saint-Denis, Montréal, Québec H2X 0A9, Canada
| | - Rosaire Mongrain
- McGill University, 845 Sherbrooke Street West, Montréal, Québec H3A 0G4, Canada
| | - Simon Lessard
- Centre de recherche du Centre hospitalier de l'Université de Montréal (CRCHUM), 900 Rue Saint-Denis, Montréal, Québec H2X 0A9, Canada
| | - Boris Chayer
- Centre de recherche du Centre hospitalier de l'Université de Montréal (CRCHUM), 900 Rue Saint-Denis, Montréal, Québec H2X 0A9, Canada
| | - Guy Cloutier
- Centre de recherche du Centre hospitalier de l'Université de Montréal (CRCHUM), 900 Rue Saint-Denis, Montréal, Québec H2X 0A9, Canada; Université de Montréal, 2900 Boulevard Edouard-Montpetit, Montréal, Québec H3T 1J4, Canada
| | - Gilles Soulez
- Centre de recherche du Centre hospitalier de l'Université de Montréal (CRCHUM), 900 Rue Saint-Denis, Montréal, Québec H2X 0A9, Canada; Université de Montréal, 2900 Boulevard Edouard-Montpetit, Montréal, Québec H3T 1J4, Canada.
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40
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Boyle CJ, Carpanen D, Pandelani T, Higgins CA, Masen MA, Masouros SD. Lateral pressure equalisation as a principle for designing support surfaces to prevent deep tissue pressure ulcers. PLoS One 2020; 15:e0227064. [PMID: 31899778 PMCID: PMC6941906 DOI: 10.1371/journal.pone.0227064] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 12/10/2019] [Indexed: 11/19/2022] Open
Abstract
When immobile or neuropathic patients are supported by beds or chairs, their soft tissues undergo deformations that can cause pressure ulcers. Current support surfaces that redistribute under-body pressures at vulnerable body sites have not succeeded in reducing pressure ulcer prevalence. Here we show that adding a supporting lateral pressure can counter-act the deformations induced by under-body pressure, and that this 'pressure equalisation' approach is a more effective way to reduce ulcer-inducing deformations than current approaches based on redistributing under-body pressure. A finite element model of the seated pelvis predicts that applying a lateral pressure to the soft tissue reduces peak von Mises stress in the deep tissue by a factor of 2.4 relative to a standard cushion (from 113 kPa to 47 kPa)-a greater effect than that achieved by using a more conformable cushion, which reduced von Mises stress to 75 kPa. Combining both a conformable cushion and lateral pressure reduced peak von Mises stresses to 25 kPa. The ratio of peak lateral pressure to peak under-body pressure was shown to regulate deep tissue stress better than under-body pressure alone. By optimising the magnitude and position of lateral pressure, tissue deformations can be reduced to that induced when suspended in a fluid. Our results explain the lack of efficacy in current support surfaces and suggest a new approach to designing and evaluating support surfaces: ensuring sufficient lateral pressure is applied to counter-act under-body pressure.
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Affiliation(s)
- Colin J. Boyle
- Department of Bioengineering, Imperial College London, London, United
Kingdom
- Department of Mechanical Engineering, Imperial College London, London,
United Kingdom
- * E-mail:
| | - Diagarajen Carpanen
- Department of Bioengineering, Imperial College London, London, United
Kingdom
| | - Thanyani Pandelani
- Department of Bioengineering, Imperial College London, London, United
Kingdom
| | - Claire A. Higgins
- Department of Bioengineering, Imperial College London, London, United
Kingdom
| | - Marc A. Masen
- Department of Mechanical Engineering, Imperial College London, London,
United Kingdom
| | - Spyros D. Masouros
- Department of Bioengineering, Imperial College London, London, United
Kingdom
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Calvo-Gallego JL, Domínguez J, Gómez Cía T, Ruiz-Moya A, Gómez Ciriza G, Martínez-Reina J. Comparison of the viscoelastic properties of human abdominal and breast adipose tissue and its incidence on breast reconstruction surgery. A pilot study. Clin Biomech (Bristol, Avon) 2020; 71:37-44. [PMID: 31683080 DOI: 10.1016/j.clinbiomech.2019.10.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 08/14/2019] [Accepted: 10/02/2019] [Indexed: 02/07/2023]
Abstract
BACKGROUND Breast cancer is the leading malignant tumor in women in the world. Reconstruction after mastectomy plays a key role in the physical and psychological recuperation, being the abdominal skin and adipose tissue the best current option for the DIEP surgery. The aim of the surgery is to obtain a reconstructed breast which looks and behaves naturally. Therefore, it would be useful to characterize the mechanical behaviour of the adipose tissue in the abdomen and breast to compare their mechanical properties, also investigating possible regional differences. METHODS Experimental tests have been carried out in breast and abdominal adipose tissue samples, obtaining their viscoelastic properties. The specimens have been subjected to uniaxial compression relaxation tests and a mechanical behaviour model has been fitted to the experimental curves. Afterwards, statistical analyses have been used to detect differences between different individuals' abdominal fat tissue and finally between different areas of the same individual's breast and abdominal adipose tissue. FINDINGS Several conclusions could be extracted from the results: 1) inter-individual differences may exist in the abdominal adipose tissue; 2) the breast fat could be regarded as a unique tissue from the mechanical point of view; 3) significant differences were detected between the superficial breast and all the locations of the abdomen, except for the superficial lateral one and 4) the mechanical properties of the abdominal adipose tissue seem to change with the depth. These conclusions can be of great value for DIEP surgeries and other surgeries in which the adipose tissue is involved.
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Affiliation(s)
- J L Calvo-Gallego
- Department of Mechanical Engineering, University of Seville, Camino de los Descubrimientos s/n, Seville 41092, Spain.
| | - J Domínguez
- Department of Mechanical Engineering, University of Seville, Camino de los Descubrimientos s/n, Seville 41092, Spain
| | - T Gómez Cía
- Cirugía Plástica y Grandes Quemados, Hospital Virgen del Rocío, Seville, Spain
| | - A Ruiz-Moya
- Cirugía Plástica y Grandes Quemados, Hospital Virgen del Rocío, Seville, Spain
| | - G Gómez Ciriza
- Grupo de Innovación Tecnológica, Hospital Virgen del Rocío, Seville, Spain
| | - J Martínez-Reina
- Department of Mechanical Engineering, University of Seville, Camino de los Descubrimientos s/n, Seville 41092, Spain
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Voňavková T, Horný L. Effect of axial prestretch and adipose tissue on the inflation-extension behavior of the human abdominal aorta. Comput Methods Biomech Biomed Engin 2019; 23:81-91. [PMID: 31814443 DOI: 10.1080/10255842.2019.1699544] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Our study aims to show that perivascular adipose tissue may significantly change the mechanical state of the abdominal aorta. To this end, uniaxial tensile tests with perivascular fat tissue were carried out. In the subsequent regression analysis, stress-strain data were fitted by the polynomial strain energy density. A constitutive model of adipose tissue was used in the analytical simulation of the inflation-extension behavior of the human abdominal aorta. The computational model was based on the theory of the bi-layered thick-walled tube. In addition to the effect of perivascular tissue, the effect of axial prestretch was also studied. It was found that the presence of perivascular tissue reduces the distensibility of the aorta. Axial prestretch applied to the aorta embedded in adipose tissue had an effect opposite to that of adipose tissue. Axially prestrained aorta exhibited higher distensiblity than non-prestrained aorta. It was also shown that the perivascular envelope bears some portion of the pressure loading and thus reduces the mechanical stresses inside the wall of aorta. A similar effect was found for axial prestretch.
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Affiliation(s)
- Tereza Voňavková
- Faculty of Mechanical Engineering, Czech Technical University in Prague, Prague, Czech Republic
| | - Lukáš Horný
- Faculty of Mechanical Engineering, Czech Technical University in Prague, Prague, Czech Republic
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Sherifova S, Sommer G, Viertler C, Regitnig P, Caranasos T, Smith MA, Griffith BE, Ogden RW, Holzapfel GA. Failure properties and microstructure of healthy and aneurysmatic human thoracic aortas subjected to uniaxial extension with a focus on the media. Acta Biomater 2019; 99:443-456. [PMID: 31465883 DOI: 10.1016/j.actbio.2019.08.038] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 08/14/2019] [Accepted: 08/21/2019] [Indexed: 12/14/2022]
Abstract
Current clinical practice for aneurysmatic interventions is often based on the maximum diameter of the vessel and/or on the growth rate, although rupture can occur at any diameter and growth rate, leading to fatality. For 27 medial samples obtained from 12 non-aneurysmatic (control) and 9 aneurysmatic human descending thoracic aortas we examined: the mechanical responses up to rupture using uniaxial extension tests of circumferential and longitudinal specimens; the structure of these tissues using second-harmonic imaging and histology, in particular, the content proportions of collagen, elastic fibers and smooth muscle cells in the media. It was found that the mean failure stresses were higher in the circumferential directions (Control-C 1474kPa; Aneurysmatic-C 1446kPa), than in the longitudinal directions (Aneurysmatic-L 735kPa; Control-L 579kPa). This trend was the opposite to that observed for the mean collagen fiber directions measured from the loading axis (Control-L > Aneurysmatic-L > Aneurysmatic-C > Control-C), thus suggesting that the trend in the failure stress can in part be attributed to the collagen architecture. The difference in the mean values of the out-of-plane dispersion in the radial/longitudinal plane between the control and aneurysmatic groups was significant. The difference in the mean values of the mean fiber angle from the circumferential direction was also significantly different between the two groups. Most specimens showed delamination zones near the ruptured region in addition to ruptured collagen and elastic fibers. This study provides a basis for further studies on the microstructure and the uniaxial failure properties of (aneurysmatic) arterial walls towards realistic modeling and prediction of tissue failure. STATEMENT OF SIGNIFICANCE: A data set relating uniaxial failure properties to the microstructure of non-aneurysmatic and aneurysmatic human thoracic aortic medias under uniaxial extension tests is presented for the first time. It was found that the mean failure stresses were higher in the circumferential directions, than in the longitudinal directions. The general trend for the failure stresses was Control-C > Aneurysmatic-C > Aneurysmatic-L > Control-L, which was the opposite of that observed for the mean collagen fiber direction relative to the loading axis (Control-L > Aneurysmatic-L > Aneurysmatic-C > Control-C) suggesting that the trend in the failure stress can in part be attributed to the collagen architecture. This study provides a first step towards more realistic modeling and prediction of tissue failure.
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Modeling of the human mandibular periosteum material properties and comparison with the calvarial periosteum. Biomech Model Mechanobiol 2019; 19:461-470. [PMID: 31512012 DOI: 10.1007/s10237-019-01221-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 08/27/2019] [Indexed: 10/26/2022]
Abstract
Knowledge of mandibular periosteum mechanical properties is fundamental for understanding its role in craniofacial growth, in trauma and bone regeneration. There is a lack in the literature regarding mechanical behavior of the human periosteum, including both experimental and modeling aspects. The proposed study involves tensile tests of periosteum samples from different locations including two locations of human mandibular periosteum: lingual and vestibular, compared with samples from various locations of the calvarial periosteum. We propose to analyze the tensile response of the mandibular periosteum using a model, initially applied on the skin, and based on a structural approach involving the mechanical properties of the corrugation of the collagen. Two different approaches for the model parameters' identification are proposed: (1) identification from experimental curve fitting and (2) identification from histological study. This approach allows us to compare parameters extracted from the traction test fitting to structural parameters measured on periosteum histological slices. Concerning experimental aspects, we showed significant differences, in terms of stiffness, between calvarial and mandibular periostea. (The mean final stiffness is [Formula: see text] for the mandible versus [Formula: see text] for the calvaria.) About modeling, we succeed to capture the correct mechanical behavior for the periosteum, and the statistical analysis showed that certain parameters from the geometric data and traction data are significantly comparable (e.g., [Formula: see text] for [Formula: see text]). However, we also observed a discrepancy between these two approaches for the elongation at which the fibril has become straight ([Formula: see text]).
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45
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Jafari J, Han XL, Palmer J, Tran PA, O'Connor AJ. Remote Control in Formation of 3D Multicellular Assemblies Using Magnetic Forces. ACS Biomater Sci Eng 2019; 5:2532-2542. [PMID: 33405759 DOI: 10.1021/acsbiomaterials.9b00297] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cell constructs have been utilized as building blocks in tissue engineering to closely mimic the natural tissue and also overcome some of the limitations caused by two-dimensional cultures or using scaffolds. External forces can be used to enhance the cells' adhesion and interaction and thus provide better control over production of these structures compared to methods like cell seeding and migration. In this paper, we demonstrate an efficient method to generate uniform, three-dimensional cell constructs using magnetic forces. This method produced spheroids with higher densities and more symmetrical structures than the commonly used centrifugation method for production of cell spheroids. It was also shown that shape of the cell constructs could be changed readily by using different patterns of magnetic field. The application of magnetic fields to impart forces on the cells enhanced the fusion of these spheroids, which could be used to produce larger and more complicated structures for future tissue engineering applications.
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Affiliation(s)
- Javad Jafari
- Department of Biomedical Engineering, Particulate Fluids Processing Centre, The University of Melbourne, Grattan St., Parkville, Victoria 3010, Australia
| | - Xiao-Lian Han
- O'Brien Institute Department, St. Vincent's Institute, 42 Fitzroy Street, Fitzroy, Victoria 3065, Australia
| | - Jason Palmer
- O'Brien Institute Department, St. Vincent's Institute, 42 Fitzroy Street, Fitzroy, Victoria 3065, Australia
| | - Phong A Tran
- Department of Biomedical Engineering, Particulate Fluids Processing Centre, The University of Melbourne, Grattan St., Parkville, Victoria 3010, Australia.,Interface Science and Materials Engineering Group, School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology (QUT), 2 George St., Brisbane, Queensland 4000, Australia
| | - Andrea J O'Connor
- Department of Biomedical Engineering, Particulate Fluids Processing Centre, The University of Melbourne, Grattan St., Parkville, Victoria 3010, Australia
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Ahmad F, Prabhu RJ, Liao J, Soe S, Jones MD, Miller J, Berthelson P, Enge D, Copeland KM, Shaabeth S, Johnston R, Maconochie I, Theobald PS. Biomechanical properties and microstructure of neonatal porcine ventricles. J Mech Behav Biomed Mater 2018; 88:18-28. [PMID: 30118921 DOI: 10.1016/j.jmbbm.2018.07.038] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 06/26/2018] [Accepted: 07/27/2018] [Indexed: 12/29/2022]
Abstract
Neonatal heart disorders represent a major clinical challenge, with congenital heart disease alone affecting 36,000 new-borns annually within the European Union. Surgical intervention to restore normal function includes the implantation of synthetic and biological materials; however, a lack of experimental data describing the mechanical behaviour of neonatal cardiac tissue is likely to contribute to the relatively poor short- and long-term outcome of these implants. This study focused on characterising the mechanical behaviour of neonatal cardiac tissue using a porcine model, to enhance the understanding of how this differs to the equivalent mature tissue. The biomechanical properties of neonatal porcine cardiac tissue were characterised by uniaxial tensile, biaxial tensile, and simple shear loading modes, using samples collected from the anterior and posterior walls of the right and left ventricles. Histological images were prepared using Masson's trichrome staining, to enable assessment of the microstructure and correlation with tissue behaviour. The mechanical tests demonstrated that the neonatal cardiac tissue is non-linear, anisotropic, viscoelastic and heterogeneous. Our data provide a baseline describing the biomechanical behaviour of immature porcine cardiac tissue. Comparison with published data also indicated that the neonatal porcine cardiac tissue exhibits one-half the stiffness of mature porcine tissue in uniaxial extension testing, one-third in biaxial extension testing, and one-fourth stiffness in simple shear testing; hence, it provides an indication as to the relative change in characteristics associated with tissue maturation. These data may prove valuable to researchers investigating neonatal cardiac mechanics.
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Affiliation(s)
| | - Ra J Prabhu
- Centre for Advanced Vehicular Systems and Department of Biological Engineering, Mississippi State University, USA
| | - Jun Liao
- Centre for Advanced Vehicular Systems and Department of Biological Engineering, Mississippi State University, USA; Department of Bioengineering, The University of Texas at Arlington, USA.
| | - Shwe Soe
- School of Engineering, Cardiff University, UK
| | | | - Jonathan Miller
- Centre for Advanced Vehicular Systems and Department of Biological Engineering, Mississippi State University, USA
| | - Parker Berthelson
- Centre for Advanced Vehicular Systems and Department of Biological Engineering, Mississippi State University, USA
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Mohammadi H, Lessard S, Therasse E, Mongrain R, Soulez G. A Numerical Preoperative Planning Model to Predict Arterial Deformations in Endovascular Aortic Aneurysm Repair. Ann Biomed Eng 2018; 46:2148-2161. [DOI: 10.1007/s10439-018-2093-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 07/06/2018] [Indexed: 12/19/2022]
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48
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Fontanella CG, Macchi V, Carniel EL, Frigo A, Porzionato A, Picardi EEE, Favero M, Ruggieri P, de Caro R, Natali AN. Biomechanical behavior of Hoffa’s fat pad in healthy and osteoarthritic conditions: histological and mechanical investigations. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2018; 41:657-667. [DOI: 10.1007/s13246-018-0661-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 06/18/2018] [Indexed: 12/30/2022]
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49
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Aldieri A, Terzini M, Bignardi C, Zanetti EM, Audenino AL. Implementation and validation of constitutive relations for human dermis mechanical response. Med Biol Eng Comput 2018; 56:2083-2093. [PMID: 29777504 DOI: 10.1007/s11517-018-1843-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 05/05/2018] [Indexed: 12/26/2022]
Abstract
Finite element models in conjunction with adequate constitutive relations are pivotal in several physiological and medical applications related to both native and engineered tissues, allowing to predict the tissue response under various loading states. In order to get reliable results, however, the validation of the constitutive models is crucial. Therefore, the main purpose of this work is to provide an experimental-computational approach to the biomechanical investigation of soft tissues such as the dermis. This is accomplished by implementing and validating three widely adopted hyperelastic constitutive models (the Ogden, the Holzapfel, and the Gasser-Ogden-Holzapfel laws) supposed to be adequate to reproduce human reticular dermis mechanical behavior. Biaxial experimental data have represented the basis for the determination of the respective material parameters identified thanks to the definition of a cost function accounting for the discrepancy between experimental and predicted data. Afterwards, the experimental tests have been reproduced through finite element simulations. Hence, the constitutive laws have been validated comparing experimental and numerical outcomes in terms of displacements of four reference points and stress-strain relations. Hence, an experimental-numerical framework is proposed for the investigation of collagenous tissues, which could become more accurate with larger and independent experimental datasets. Graphical abstract ᅟ.
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Affiliation(s)
- Alessandra Aldieri
- PolitoBIOMed Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, 24, Corso Duca degli Abruzzi, 10129, Turin, Italy.
| | - Mara Terzini
- PolitoBIOMed Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, 24, Corso Duca degli Abruzzi, 10129, Turin, Italy
| | - Cristina Bignardi
- PolitoBIOMed Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, 24, Corso Duca degli Abruzzi, 10129, Turin, Italy
| | | | - Alberto L Audenino
- PolitoBIOMed Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, 24, Corso Duca degli Abruzzi, 10129, Turin, Italy
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50
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Comparison of different constitutive models to characterize the viscoelastic properties of human abdominal adipose tissue. A pilot study. J Mech Behav Biomed Mater 2018; 80:293-302. [DOI: 10.1016/j.jmbbm.2018.02.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 02/03/2018] [Accepted: 02/09/2018] [Indexed: 11/20/2022]
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