1
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Huff RD, Houghton F, Earl CC, Ghajar-Rahimi E, Dogra I, Yu D, Harris-Adamson C, Goergen CJ, O'Connell GD. Deep learning enables accurate soft tissue tendon deformation estimation in vivo via ultrasound imaging. Sci Rep 2024; 14:18401. [PMID: 39117664 PMCID: PMC11310354 DOI: 10.1038/s41598-024-68875-w] [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: 02/08/2024] [Accepted: 07/29/2024] [Indexed: 08/10/2024] Open
Abstract
Image-based deformation estimation is an important tool used in a variety of engineering problems, including crack propagation, fracture, and fatigue failure. These tools have been important in biomechanics research where measuring in vitro and in vivo tissue deformations are important for evaluating tissue health and disease progression. However, accurately measuring tissue deformation in vivo is particularly challenging due to limited image signal-to-noise ratio. Therefore, we created a novel deep-learning approach for measuring deformation from a sequence of images collected in vivo called StrainNet. Utilizing a training dataset that incorporates image artifacts, StrainNet was designed to maximize performance in challenging, in vivo settings. Artificially generated image sequences of human flexor tendons undergoing known deformations were used to compare benchmark StrainNet against two conventional image-based strain measurement techniques. StrainNet outperformed the traditional techniques by nearly 90%. High-frequency ultrasound imaging was then used to acquire images of the flexor tendons engaged during contraction. Only StrainNet was able to track tissue deformations under the in vivo test conditions. Findings revealed strong correlations between tendon deformation and applied forces, highlighting the potential for StrainNet to be a valuable tool for assessing rehabilitation strategies or disease progression. Additionally, by using real-world data to train our model, StrainNet was able to generalize and reveal important relationships between the effort exerted by the participant and tendon mechanics. Overall, StrainNet demonstrated the effectiveness of using deep learning for image-based strain analysis in vivo.
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Affiliation(s)
- Reece D Huff
- Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Frederick Houghton
- Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Conner C Earl
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Elnaz Ghajar-Rahimi
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Ishan Dogra
- Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Denny Yu
- School of Industrial Engineering, Purdue University, West Lafayette, IN, 47906, USA
| | - Carisa Harris-Adamson
- School of Public Health, University of California, Berkeley, Berkeley, CA, 94704, USA
- Department of Occupational and Environmental Medicine, University of California, San Francisco, San Francisco, CA, 94117, USA
| | - Craig J Goergen
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Grace D O'Connell
- Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA.
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, 94142, USA.
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2
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Kobeissi H, Jilberto J, Karakan MÇ, Gao X, DePalma SJ, Das SL, Quach L, Urquia J, Baker BM, Chen CS, Nordsletten D, Lejeune E. MicroBundleCompute: Automated segmentation, tracking, and analysis of subdomain deformation in cardiac microbundles. PLoS One 2024; 19:e0298863. [PMID: 38530829 DOI: 10.1371/journal.pone.0298863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 02/01/2024] [Indexed: 03/28/2024] Open
Abstract
Advancing human induced pluripotent stem cell derived cardiomyocyte (hiPSC-CM) technology will lead to significant progress ranging from disease modeling, to drug discovery, to regenerative tissue engineering. Yet, alongside these potential opportunities comes a critical challenge: attaining mature hiPSC-CM tissues. At present, there are multiple techniques to promote maturity of hiPSC-CMs including physical platforms and cell culture protocols. However, when it comes to making quantitative comparisons of functional behavior, there are limited options for reliably and reproducibly computing functional metrics that are suitable for direct cross-system comparison. In addition, the current standard functional metrics obtained from time-lapse images of cardiac microbundle contraction reported in the field (i.e., post forces, average tissue stress) do not take full advantage of the available information present in these data (i.e., full-field tissue displacements and strains). Thus, we present "MicroBundleCompute," a computational framework for automatic quantification of morphology-based mechanical metrics from movies of cardiac microbundles. Briefly, this computational framework offers tools for automatic tissue segmentation, tracking, and analysis of brightfield and phase contrast movies of beating cardiac microbundles. It is straightforward to implement, runs without user intervention, requires minimal input parameter setting selection, and is computationally inexpensive. In this paper, we describe the methods underlying this computational framework, show the results of our extensive validation studies, and demonstrate the utility of exploring heterogeneous tissue deformations and strains as functional metrics. With this manuscript, we disseminate "MicroBundleCompute" as an open-source computational tool with the aim of making automated quantitative analysis of beating cardiac microbundles more accessible to the community.
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Affiliation(s)
- Hiba Kobeissi
- Department of Mechanical Engineering, Boston University, Boston, MA, United States of America
- Center for Multiscale and Translational Mechanobiology, Boston University, Boston, MA, United States of America
| | - Javiera Jilberto
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
| | - M Çağatay Karakan
- Department of Mechanical Engineering, Boston University, Boston, MA, United States of America
- Photonics Center, Boston University, Boston, MA, United States of America
- Department of Biomedical Engineering, Boston University, Boston, MA, United States of America
| | - Xining Gao
- Department of Biomedical Engineering, Boston University, Boston, MA, United States of America
- Harvard-MIT Program in Health Sciences and Technology, Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, United States of America
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, United States of America
| | - Samuel J DePalma
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
| | - Shoshana L Das
- Department of Biomedical Engineering, Boston University, Boston, MA, United States of America
- Harvard-MIT Program in Health Sciences and Technology, Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, United States of America
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, United States of America
| | - Lani Quach
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
| | - Jonathan Urquia
- Department of Electrical and Computer Engineering, New York Institute of Technology, New York, NY, United States of America
| | - Brendon M Baker
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
| | - Christopher S Chen
- Department of Biomedical Engineering, Boston University, Boston, MA, United States of America
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, United States of America
| | - David Nordsletten
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
- Department of Cardiac Surgery, University of Michigan, Ann Arbor, MI, United States of America
- Department of Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, King's Health Partners, King's College London, King's Health Partners, London, United Kingdom
| | - Emma Lejeune
- Department of Mechanical Engineering, Boston University, Boston, MA, United States of America
- Center for Multiscale and Translational Mechanobiology, Boston University, Boston, MA, United States of America
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3
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Christoph J, Ripplinger CM. Paralysis by analysis: Overcoming cardiac contraction with computer vision. Proc Natl Acad Sci U S A 2023; 120:e2314448120. [PMID: 37792520 PMCID: PMC10589680 DOI: 10.1073/pnas.2314448120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/06/2023] Open
Affiliation(s)
- Jan Christoph
- Cardiovascular Research Institute and Division of Cardiology, University of California, San Francisco, CA94158
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4
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Lake SP, Snedeker JG, Wang VM, Awad H, Screen HRC, Thomopoulos S. Guidelines for ex vivo mechanical testing of tendon. J Orthop Res 2023; 41:2105-2113. [PMID: 37312619 PMCID: PMC10528429 DOI: 10.1002/jor.25647] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 05/27/2023] [Accepted: 05/30/2023] [Indexed: 06/15/2023]
Abstract
Tendons are critical for the biomechanical function of joints. Tendons connect muscles to bones and allow for the transmission of muscle forces to facilitate joint motion. Therefore, characterizing the tensile mechanical properties of tendons is important for the assessment of functional tendon health and efficacy of treatments for acute and chronic injuries. In this guidelines paper, we review methodological considerations, testing protocols, and key outcome measures for mechanical testing of tendons. The goal of the paper is to present a simple set of guidelines to the nonexpert seeking to perform tendon mechanical tests. The suggested approaches provide rigorous and consistent methodologies for standardized biomechanical characterization of tendon and reporting requirements across laboratories.
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Affiliation(s)
- Spencer P. Lake
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, Missouri, USA
| | | | - Vincent M. Wang
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, Virginia, USA
| | - Hani Awad
- Department of Orthopaedics, Department of Biomedical Engineering, University of Rochester, Rochester, New York, USA
| | - Hazel R. C. Screen
- School of Engineering & Materials Science, Queen Mary University of London, London, UK
| | - Stavros Thomopoulos
- Department of Orthopaedic Surgery, Department of Biomedical Engineering, Columbia University, New York, New York, USA
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5
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Woodhams LG, Guo J, Schuftan D, Boyle JJ, Pryse KM, Elson EL, Huebsch N, Genin GM. Virtual blebbistatin: A robust and rapid software approach to motion artifact removal in optical mapping of cardiomyocytes. Proc Natl Acad Sci U S A 2023; 120:e2212949120. [PMID: 37695908 PMCID: PMC10515162 DOI: 10.1073/pnas.2212949120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 07/31/2023] [Indexed: 09/13/2023] Open
Abstract
Fluorescent reporters of cardiac electrophysiology provide valuable information on heart cell and tissue function. However, motion artifacts caused by cardiac muscle contraction interfere with accurate measurement of fluorescence signals. Although drugs such as blebbistatin can be applied to stop cardiac tissue from contracting by uncoupling calcium-contraction, their usage prevents the study of excitation-contraction coupling and, as we show, impacts cellular structure. We therefore developed a robust method to remove motion computationally from images of contracting cardiac muscle and to map fluorescent reporters of cardiac electrophysiological activity onto images of undeformed tissue. When validated on cardiomyocytes derived from human induced pluripotent stem cells (iPSCs), in both monolayers and engineered tissues, the method enabled efficient and robust reduction of motion artifact. As with pharmacologic approaches using blebbistatin for motion removal, our algorithm improved the accuracy of optical mapping, as demonstrated by spatial maps of calcium transient decay. However, unlike pharmacologic motion removal, our computational approach allowed direct analysis of calcium-contraction coupling. Results revealed calcium-contraction coupling to be more uniform across cells within engineered tissues than across cells in monolayer culture. The algorithm shows promise as a robust and accurate tool for optical mapping studies of excitation-contraction coupling in heart tissue.
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Affiliation(s)
- Louis G Woodhams
- Department of Mechanical Engineering and Material Science, Washington University in Saint Louis, St. Louis, MO 63130
| | - Jingxuan Guo
- Department of Mechanical Engineering and Material Science, Washington University in Saint Louis, St. Louis, MO 63130
| | - David Schuftan
- Department of Biomedical Engineering, Washington University in Saint Louis, St. Louis, MO 63130
| | - John J Boyle
- Department of Biomedical Engineering, Washington University in Saint Louis, St. Louis, MO 63130
| | - Kenneth M Pryse
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
| | - Elliot L Elson
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110
- NSF Science and Technology Center for Engineering Mechanobiology, Washington University in Saint Louis, St. Louis, MO 63130
| | - Nathaniel Huebsch
- Department of Biomedical Engineering, Washington University in Saint Louis, St. Louis, MO 63130
- NSF Science and Technology Center for Engineering Mechanobiology, Washington University in Saint Louis, St. Louis, MO 63130
| | - Guy M Genin
- Department of Mechanical Engineering and Material Science, Washington University in Saint Louis, St. Louis, MO 63130
- NSF Science and Technology Center for Engineering Mechanobiology, Washington University in Saint Louis, St. Louis, MO 63130
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6
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Abstract
A strain gradient was created by punching a hole in the center of a stretched elastic polydimethylsiloxane membrane to determine the effect of different strains on cultured human keratocytes (HK). In this study, two stretching methods were used: continuous stretching and cyclic stretching. Continuous stretching is relatively static, while acyclic stretching is relatively dynamic. These methods, respectively, represented the effects of high intraocular pressure and rubbing of the eyes on corneal cells. Image processing codes were developed to observe the effects of stress concentration, shear stress, continuous stretching, and cyclic stretching on HKs. The results demonstrate that stretching and shear stress are not conducive to the proliferation of corneal cells and instead cause cell death. A 10% strain had greater inhibitory effects than a 3% strain on cell proliferation. Cell survival rates for continuous stretching (static) were higher than those for cyclic stretching (dynamic). The stretching experiment revealed that cyclic stretching has a greater inhibitory effect on the growth and proliferation of corneal cells than continuous stretching. Accordingly, it shows that cyclic loading is more harmful than high intraocular pressure (static loading) to corneal cells.
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7
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Dai ZX, Shih PJ, Yen JY, Wang IJ. Functional assistance for stress distribution in cell culture membrane under periodically stretching. J Biomech 2021; 125:110564. [PMID: 34237658 DOI: 10.1016/j.jbiomech.2021.110564] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 05/28/2021] [Accepted: 05/31/2021] [Indexed: 11/19/2022]
Abstract
Dynamic cell cultures simulate the in vivo cell environment for a regular loading system with curtain strains. However, it is difficult to obtain strains that are suitable for cells without conducting multiple trials. This study develops a device that increases the strain gradient by changing the tensile section, in order to determine the effect of various cyclic strains on cultured human keratinocytes (HK) cells. This device is used to determine the effect of 3% and 5% cyclic strain and shear strain on cell proliferation and arrangement at 1 Hz. The results show that compared with static and 3% strain, a 5% cyclic strain better inhibits the proliferation of HK cells. Compared to the initial cell attachment when there is no specific directionality, the cells are aligned in the vertical stretching direction after cyclic stretching. This equipment increases the efficiency of the experiment and more intuitively maps the cell behavior and shape to the strain field and the response to the shear strain.
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Affiliation(s)
- Zhi-Xuan Dai
- Department of Mechanical Engineering, National Taiwan University, 10617 Taipei, Taiwan
| | - Po-Jen Shih
- Department of Biomedical Engineering, National Taiwan University, 10617 Taipei, Taiwan.
| | - Jia-Yush Yen
- Department of Mechanical Engineering, National Taiwan University, 10617 Taipei, Taiwan; Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan
| | - I-Jong Wang
- Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan
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8
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Shakiba D, Alisafaei F, Savadipour A, Rowe RA, Liu Z, Pryse KM, Shenoy VB, Elson EL, Genin GM. The Balance between Actomyosin Contractility and Microtubule Polymerization Regulates Hierarchical Protrusions That Govern Efficient Fibroblast-Collagen Interactions. ACS NANO 2020; 14:7868-7879. [PMID: 32286054 DOI: 10.1021/acsnano.9b09941] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Fibroblasts undergo a critical transformation from an initially inactive state to a morphologically different and contractile state after several hours of being embedded within a physiologically relevant three-dimensional (3D) fibrous collagen-based extracellular matrix (ECM). However, little is known about the critical mechanisms by which fibroblasts adapt themselves and their microenvironment in the earliest stage of cell-matrix interaction. Here, we identified the mechanisms by which fibroblasts interact with their 3D collagen fibrous matrices in the early stages of cell-matrix interaction and showed that fibroblasts use energetically efficient hierarchical micro/nano-scaled protrusions in these stages as the primary means for the transformation and adaptation. We found that actomyosin contractility in these protrusions in the early stages of cell-matrix interaction restricts the growth of microtubules by applying compressive forces on them. Our results show that actomyosin contractility and microtubules work in concert in the early stages of cell-matrix interaction to adapt fibroblasts and their microenvironment to one another. These early stage interactions result in responses to disruption of the microtubule network and/or actomyosin contractility that are opposite to well-known responses to late-stage disruption and reveal insight into the ways that cells adapt themselves and their ECM recursively.
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Affiliation(s)
- Delaram Shakiba
- NSF Science and Technology Center for Engineering Mechanobiology and Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri 63130 United States
| | - Farid Alisafaei
- NSF Science and Technology Center for Engineering Mechanobiology and Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Alireza Savadipour
- NSF Science and Technology Center for Engineering Mechanobiology and Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri 63130 United States
| | - Roger A Rowe
- NSF Science and Technology Center for Engineering Mechanobiology and Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri 63130 United States
| | - Zhangao Liu
- NSF Science and Technology Center for Engineering Mechanobiology and Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri 63130 United States
| | - Kenneth M Pryse
- NSF Science and Technology Center for Engineering Mechanobiology and Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri 63130 United States
| | - Vivek B Shenoy
- NSF Science and Technology Center for Engineering Mechanobiology and Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Elliot L Elson
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, United States
| | - Guy M Genin
- NSF Science and Technology Center for Engineering Mechanobiology and Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri 63130 United States
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9
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Boyle JJ, Pless RB, Thomopoulos S, Genin GM. Direct Estimation of Surface Strain Fields From a Stereo Vision System. J Biomech Eng 2020; 142:074503. [PMID: 31891380 PMCID: PMC7104767 DOI: 10.1115/1.4045813] [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: 05/30/2019] [Revised: 12/07/2019] [Indexed: 11/08/2022]
Abstract
Estimating strain on surfaces of deforming three-dimensional (3D) structures is a critical need in experimental mechanics. Although single-camera techniques excel at estimating deformation on a surface parallel to the imaging plane, they are prone to artifact for 3D motion because they cannot distinguish between out-of-plane motion and in-plane dilatation. Multiview (e.g., stereo) camera systems overcome this via a three-step process consisting of: (1) independent surface registration, (2) triangulation to estimate surface displacements, and (3) deformation estimation. However, existing methods are prone to errors associated with numerical differentiation when computing estimating strain fields from displacement fields unless regularization schemes are used. Such regularization schemes can introduce inaccuracy into strain estimation. Inspired by previous work which combined registration and deformation estimation into a single step for 2D images and 3D imaging stacks, we developed a theory for simultaneous image registration, 3D triangulation, and deformation estimation in a multiview system. The deformation estimation does not require numerical differentiation of displacement fields to estimate strain fields. We present here the theoretical foundations and derivation of two related implementations of this approach, and discuss their strengths and weaknesses.
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Affiliation(s)
- John J Boyle
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032-3702; Department of Biomedical Engineering, Washington University, St Louis, MO 63130
| | - Robert B Pless
- Department of Computer Science, George Washington University, Washington, DC 20052
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032; Department of Biomedical Engineering, Columbia University, New York, NY 10032
| | - Guy M Genin
- Department of Mechanical Engineering and Materials Science, NSF Science and Technology Center for Engineering MechanoBiology, Washington University, St Louis, MO 63130
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10
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Gomez AD, Knutsen AK, Pham DL, Bayly PV, Prince JL. Quantitative Validation of MRI-Based Motion Estimation for Brain Impact Biomechanics. COMPUTATIONAL BIOMECHANICS FOR MEDICINE 2020; 2020:61-71. [PMID: 37067891 PMCID: PMC10103905 DOI: 10.1007/978-3-030-15923-8_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Head impact can cause traumatic brain injury (TBI) through axonal overstretch or subsequent inflammation and understanding the biomechanics of the impact event is useful for TBI prevention research. Tagged magnetic resonance imaging (MRI) acquired during a mild-acceleration impact has enabled measurement and visualization of brain deformation in vivo. However, measurements using MRI are subject to error, and having independent validation while imaging in vivo is very difficult. Thus, characterizing the accuracy of these measurements needs to be done in a separate experiment using a phantom where a gold standard is available. This study describes a method for error quantification using a calibration phantom compatible with MRI and high-speed video (the gold standard). During linear acceleration, the maximum shear strain (MSS) in the phantom ranged from 0 to 12%, which is similar to in vivo brain deformation at a similar acceleration. The mean displacement error against video was 0.3±0.3 mm, and the MSS error was 1.4±0.3%. To match resolutions, video data was filtered temporally using an averaging filter. Compared to the unfiltered results, resolution matching improved the agreement between MRI and video results by 15%. In conclusion, tagged MRI analysis compares well to video data provided that resolutions are matched-a finding that is also applicable when using MRI to validate simulations.
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Affiliation(s)
- Arnold D Gomez
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, USA
| | - Andrew K Knutsen
- Center for Neuroscience and Regenerative Medicine, Henry Jackson Foundation, Bethesda, USA
| | - Dzung L Pham
- Center for Neuroscience and Regenerative Medicine, Henry Jackson Foundation, Bethesda, USA
| | - Philip V Bayly
- Mechanical Engineering Department, Washington University in St. Louis, St. Louis, USA
| | - Jerry L Prince
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, USA
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11
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Stepien TL, Lynch HE, Yancey SX, Dempsey L, Davidson LA. Using a continuum model to decipher the mechanics of embryonic tissue spreading from time-lapse image sequences: An approximate Bayesian computation approach. PLoS One 2019; 14:e0218021. [PMID: 31246967 PMCID: PMC6597152 DOI: 10.1371/journal.pone.0218021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 05/24/2019] [Indexed: 11/18/2022] Open
Abstract
Advanced imaging techniques generate large datasets capable of describing the structure and kinematics of tissue spreading in embryonic development, wound healing, and the progression of many diseases. These datasets can be integrated with mathematical models to infer biomechanical properties of the system, typically identifying an optimal set of parameters for an individual experiment. However, these methods offer little information on the robustness of the fit and are generally ill-suited for statistical tests of multiple experiments. To overcome this limitation and enable efficient use of large datasets in a rigorous experimental design, we use the approximate Bayesian computation rejection algorithm to construct probability density distributions that estimate model parameters for a defined theoretical model and set of experimental data. Here, we demonstrate this method with a 2D Eulerian continuum mechanical model of spreading embryonic tissue. The model is tightly integrated with quantitative image analysis of different sized embryonic tissue explants spreading on extracellular matrix (ECM) and is regulated by a small set of parameters including forces on the free edge, tissue stiffness, strength of cell-ECM adhesions, and active cell shape changes. We find statistically significant trends in key parameters that vary with initial size of the explant, e.g., for larger explants cell-ECM adhesion forces are weaker and free edge forces are stronger. Furthermore, we demonstrate that estimated parameters for one explant can be used to predict the behavior of other similarly sized explants. These predictive methods can be used to guide further experiments to better understand how collective cell migration is regulated during development.
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Affiliation(s)
- Tracy L. Stepien
- Department of Mathematics, University of Arizona, Tucson, AZ, United States of America
| | - Holley E. Lynch
- Department of Physics, Stetson University, DeLand, FL, United States of America
| | - Shirley X. Yancey
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Laura Dempsey
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Lance A. Davidson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States of America
- Department of Developmental Biology, University of Pittsburgh, Pittsburgh, PA, United States of America
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA, United States of America
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12
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Cebull HL, Soepriatna AH, Boyle JJ, Rothenberger SM, Goergen CJ. Strain Mapping From Four-Dimensional Ultrasound Reveals Complex Remodeling in Dissecting Murine Abdominal Aortic Aneurysms. J Biomech Eng 2019; 141:2728066. [DOI: 10.1115/1.4043075] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2018] [Indexed: 12/12/2022]
Abstract
Current in vivo abdominal aortic aneurysm (AAA) imaging approaches tend to focus on maximum diameter but do not measure three-dimensional (3D) vascular deformation or strain. Complex vessel geometries, heterogeneous wall compositions, and surrounding structures can all influence aortic strain. Improved understanding of complex aortic kinematics has the potential to increase our ability to predict aneurysm expansion and eventual rupture. Here, we describe a method that combines four-dimensional (4D) ultrasound and direct deformation estimation to compute in vivo 3D Green-Lagrange strain in murine angiotensin II-induced suprarenal dissecting aortic aneurysms, a commonly used small animal model. We compared heterogeneous patterns of the maximum, first-component 3D Green-Lagrange strain with vessel composition from mice with varying AAA morphologies. Intramural thrombus and focal breakage in the medial elastin significantly reduced aortic strain. Interestingly, a dissection that was not detected with high-frequency ultrasound also experienced reduced strain, suggesting medial elastin breakage that was later confirmed via histology. These results suggest that in vivo measurements of 3D strain can provide improved insight into aneurysm disease progression. While further work is needed with both preclinical animal models and human imaging studies, this initial murine study indicates that vessel strain should be considered when developing an improved metric for predicting aneurysm growth and rupture.
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Affiliation(s)
- Hannah L. Cebull
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN 47907 e-mail:
| | - Arvin H. Soepriatna
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN 47907 e-mail:
| | - John J. Boyle
- Department of Biomedical Engineering, Washington University, 1 Brookings Drive, St Louis, MO 63130
- Department of Orthopaedic Surgery, Columbia University, 116th Street and Broadway, New York, NY 10027 e-mail:
| | - Sean M. Rothenberger
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN 47907 e-mail:
| | - Craig J. Goergen
- Mem. ASME Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN 47907 e-mail:
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13
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Huang L, Korhonen RK, Turunen MJ, Finnilä MAJ. Experimental mechanical strain measurement of tissues. PeerJ 2019; 7:e6545. [PMID: 30867989 PMCID: PMC6409087 DOI: 10.7717/peerj.6545] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 01/31/2019] [Indexed: 12/22/2022] Open
Abstract
Strain, an important biomechanical factor, occurs at different scales from molecules and cells to tissues and organs in physiological conditions. Under mechanical strain, the strength of tissues and their micro- and nanocomponents, the structure, proliferation, differentiation and apoptosis of cells and even the cytokines expressed by cells probably shift. Thus, the measurement of mechanical strain (i.e., relative displacement or deformation) is critical to understand functional changes in tissues, and to elucidate basic relationships between mechanical loading and tissue response. In the last decades, a great number of methods have been developed and applied to measure the deformations and mechanical strains in tissues comprising bone, tendon, ligament, muscle and brain as well as blood vessels. In this article, we have reviewed the mechanical strain measurement from six aspects: electro-based, light-based, ultrasound-based, magnetic resonance-based and computed tomography-based techniques, and the texture correlation-based image processing method. The review may help solving the problems of experimental and mechanical strain measurement of tissues under different measurement environments.
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Affiliation(s)
- Lingwei Huang
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Rami K Korhonen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Mikael J Turunen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Mikko A J Finnilä
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.,Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland.,Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland
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14
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Boyle JJ, Soepriatna A, Damen F, Rowe RA, Pless RB, Kovacs A, Goergen CJ, Thomopoulos S, Genin GM. Regularization-Free Strain Mapping in Three Dimensions, With Application to Cardiac Ultrasound. J Biomech Eng 2019; 141:2705368. [PMID: 30267039 PMCID: PMC6298532 DOI: 10.1115/1.4041576] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Revised: 09/21/2018] [Indexed: 12/17/2022]
Abstract
Quantifying dynamic strain fields from time-resolved volumetric medical imaging and microscopy stacks is a pressing need for radiology and mechanobiology. A critical limitation of all existing techniques is regularization: because these volumetric images are inherently noisy, the current strain mapping techniques must impose either displacement regularization and smoothing that sacrifices spatial resolution, or material property assumptions that presuppose a material model, as in hyperelastic warping. Here, we present, validate, and apply the first three-dimensional (3D) method for estimating mechanical strain directly from raw 3D image stacks without either regularization or assumptions about material behavior. We apply the method to high-frequency ultrasound images of mouse hearts to diagnose myocardial infarction. We also apply the method to present the first ever in vivo quantification of elevated strain fields in the heart wall associated with the insertion of the chordae tendinae. The method shows promise for broad application to dynamic medical imaging modalities, including high-frequency ultrasound, tagged magnetic resonance imaging, and confocal fluorescence microscopy.
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Affiliation(s)
- John J. Boyle
- Department of Biomedical Engineering,
Washington University in St. Louis,
St. Louis, MO 63130;
Department of Orthopaedic Surgery,Columbia University,
Black Building 1406, 650 W 168 Street,
New York, NY 10032
e-mail:
| | - Arvin Soepriatna
- Weldon School of Biomedical Engineering,
Purdue University,
206 S. Martin Jischke Drive, Room 3025,
West Lafayette, IN 47907
e-mail:
| | - Frederick Damen
- Weldon School of Biomedical Engineering,
Purdue University,
206 S. Martin Jischke Drive, Room 3025,
West Lafayette, IN 47907
e-mail:
| | - Roger A. Rowe
- Department of Mechanical Engineering and
Materials Science,
Washington University in St. Louis,
Jolley Hall, CB 1185, 1 Brookings Drive,
St. Louis, MO 63130
e-mail:
| | - Robert B. Pless
- Department of Computer Science,
George Washington University,
800 22nd Street NW Room 4000,
Washington, DC 20052
e-mail:
| | - Attila Kovacs
- Department of Internal Medicine,
Cardiovascular Division,
Washington University School of Medicine,
660 S. Euclid Avenue, CB 8086,
St. Louis, MO 63110
e-mail:
| | - Craig J. Goergen
- Mem. ASME
Weldon School of Biomedical Engineering,
Purdue University,
206 S. Martin Jischke Drive, Room 3025,
West Lafayette, IN 47907
e-mail:
| | - Stavros Thomopoulos
- Mem. ASMEDepartment of Orthopaedic Surgery,
Columbia University,
New York, NY 10032;
Department of Biomedical Engineering,Columbia University,
Black Building 1408, 650 W 168 Street,
New York, NY 10032
e-mail:
| | - Guy M. Genin
- Fellow ASME
Department of Biomedical Engineering,
Washington University in St. Louis,
St. Louis, MO 63130;
Department of Mechanical Engineering and
Materials Science,
Washington University in St. Louis,
St. Louis, MO 63130;
NSF Science and Technology Center
for Engineering Mechanobiology,
Washington University in St. Louis,
Green Hall, CB 1099, 1 Brookings Drive,
St. Louis, MO 63130
e-mail:
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15
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Yeroslavsky G, Kamimura M, Inoue R, Kogo Y, Soga K. Visualization of Strain in Elastic Silicone Polymers Using Fluorescence Energy Transfer. J PHOTOPOLYM SCI TEC 2018. [DOI: 10.2494/photopolymer.31.533] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Gil Yeroslavsky
- Department of Material Science and Technology, Tokyo University of Science
- Imaging Frontier Center (IFC), Research Institute for Science and Technology (RIST), Tokyo University of Science
| | - Masao Kamimura
- Department of Material Science and Technology, Tokyo University of Science
- Imaging Frontier Center (IFC), Research Institute for Science and Technology (RIST), Tokyo University of Science
| | - Ryo Inoue
- Department of Material Science and Technology, Tokyo University of Science
| | - Yasuo Kogo
- Department of Material Science and Technology, Tokyo University of Science
| | - Kohei Soga
- Department of Material Science and Technology, Tokyo University of Science
- Imaging Frontier Center (IFC), Research Institute for Science and Technology (RIST), Tokyo University of Science
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16
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Abstract
The connective tissues of the musculoskeletal system can be grouped into fibrous, cartilaginous, and calcified tissues. While each tissue type has a distinct composition and function, the intersections between these tissues result in the formation of complex, composite, and graded junctions. The complexity of these interfaces is a critical aspect of their healthy function, but poses a significant challenge for their repair. In this review, we describe the organization and structure of complex musculoskeletal interfaces, identify emerging technologies for engineering such structures, and outline the requirements for assessing the complex nature of these tissues in the context of recapitulating their function through tissue engineering.
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Affiliation(s)
- Edward D Bonnevie
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, and Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA;
- Translational Musculoskeletal Research Center, Col. Michael J. Crescenz Veterans Administration Medical Center, Philadelphia, Pennsylvania 19104, USA
| | - Robert L Mauck
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, and Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA;
- Translational Musculoskeletal Research Center, Col. Michael J. Crescenz Veterans Administration Medical Center, Philadelphia, Pennsylvania 19104, USA
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17
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Linderman SW, Golman M, Gardner TR, Birman V, Levine WN, Genin GM, Thomopoulos S. Enhanced tendon-to-bone repair through adhesive films. Acta Biomater 2018; 70:165-176. [PMID: 29427745 DOI: 10.1016/j.actbio.2018.01.032] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Revised: 01/04/2018] [Accepted: 01/23/2018] [Indexed: 12/16/2022]
Abstract
Tendon-to-bone surgical repairs have unacceptably high failure rates, possibly due to their inability to recreate the load transfer mechanisms of the native enthesis. Instead of distributing load across a wide attachment footprint area, surgical repairs concentrate shear stress on a small number of suture anchor points. This motivates development of technologies that distribute shear stresses away from suture anchors and across the enthesis footprint. Here, we present predictions and proof-of-concept experiments showing that mechanically-optimized adhesive films can mimic the natural load transfer mechanisms of the healthy attachment and increase the load tolerance of a repair. Mechanical optimization, based upon a shear lag model corroborated by a finite element analysis, revealed that adhesives with relatively high strength and low stiffness can, theoretically, strengthen tendon-to-bone repairs by over 10-fold. Lap shear testing using tendon and bone planks validated the mechanical models for a range of adhesive stiffnesses and strengths. Ex vivo human supraspinatus repairs of cadaveric tissues using multipartite adhesives showed substantial increase in strength. Results suggest that adhesive-enhanced repair can improve repair strength, and motivate a search for optimal adhesives. STATEMENT OF SIGNIFICANCE Current surgical techniques for tendon-to-bone repair have unacceptably high failure rates, indicating that the initial repair strength is insufficient to prevent gapping or rupture. In the rotator cuff, repair techniques apply compression over the repair interface to achieve contact healing between tendon and bone, but transfer almost all force in shear across only a few points where sutures puncture the tendon. Therefore, we evaluated the ability of an adhesive film, implanted between tendon and bone, to enhance repair strength and minimize the likelihood of rupture. Mechanical models demonstrated that optimally designed adhesives would improve repair strength by over 10-fold. Experiments using idealized and clinically-relevant repairs validated these models. This work demonstrates an opportunity to dramatically improve tendon-to-bone repair strength using adhesive films with appropriate material properties.
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18
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Morrell AE, Brown GN, Robinson ST, Sattler RL, Baik AD, Zhen G, Cao X, Bonewald LF, Jin W, Kam LC, Guo XE. Mechanically induced Ca 2+ oscillations in osteocytes release extracellular vesicles and enhance bone formation. Bone Res 2018; 6:6. [PMID: 29581909 PMCID: PMC5859015 DOI: 10.1038/s41413-018-0007-x] [Citation(s) in RCA: 104] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 11/23/2017] [Indexed: 02/01/2023] Open
Abstract
The vast osteocytic network is believed to orchestrate bone metabolic activity in response to mechanical stimuli through production of sclerostin, RANKL, and osteoprotegerin (OPG). However, the mechanisms of osteocyte mechanotransduction remain poorly understood. We've previously shown that osteocyte mechanosensitivity is encoded through unique intracellular calcium (Ca2+) dynamics. Here, by simultaneously monitoring Ca2+ and actin dynamics in single cells exposed to fluid shear flow, we detected actin network contractions immediately upon onset of flow-induced Ca2+ transients, which were facilitated by smooth muscle myosin and further confirmed in native osteocytes ex vivo. Actomyosin contractions have been linked to the secretion of extracellular vesicles (EVs), and our studies demonstrate that mechanical stimulation upregulates EV production in osteocytes through immunostaining for the secretory vesicle marker Lysosomal-associated membrane protein 1 (LAMP1) and quantifying EV release in conditioned medium, both of which are blunted when Ca2+ signaling was inhibited by neomycin. Axial tibia compression was used to induce anabolic bone formation responses in mice, revealing upregulated LAMP1 and expected downregulation of sclerostin in vivo. This load-related increase in LAMP1 expression was inhibited in neomycin-injected mice compared to vehicle. Micro-computed tomography revealed significant load-related increases in both trabecular bone volume fraction and cortical thickness after two weeks of loading, which were blunted by neomycin treatment. In summary, we found mechanical stimulation of osteocytes activates Ca2+-dependent contractions and enhances the production and release of EVs containing bone regulatory proteins. Further, blocking Ca2+ signaling significantly attenuates adaptation to mechanical loading in vivo, suggesting a critical role for Ca2+-mediated signaling in bone adaptation.
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Affiliation(s)
- Andrea E. Morrell
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY USA
| | - Genevieve N. Brown
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY USA
| | - Samuel T. Robinson
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY USA
| | - Rachel L. Sattler
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY USA
| | - Andrew D. Baik
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY USA
| | - Gehua Zhen
- Center for Musculoskeletal Research, Department of Orthopaedic Surgery, Johns Hopkins University, Baltimore, MD USA
| | - Xu Cao
- Center for Musculoskeletal Research, Department of Orthopaedic Surgery, Johns Hopkins University, Baltimore, MD USA
| | - Lynda F. Bonewald
- Indiana Center for Musculoskeletal Health, Indiana University School of Medicine, Indianapolis, IN USA
| | - Weiyang Jin
- Microscale Biocomplexity Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY USA
| | - Lance C. Kam
- Microscale Biocomplexity Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY USA
| | - X. Edward Guo
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY USA
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19
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Kim D, Lee B, Thomopoulos S, Jun YS. The role of confined collagen geometry in decreasing nucleation energy barriers to intrafibrillar mineralization. Nat Commun 2018; 9:962. [PMID: 29511184 PMCID: PMC5840387 DOI: 10.1038/s41467-018-03041-1] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 01/16/2018] [Indexed: 12/03/2022] Open
Abstract
Mineralization of collagen is critical for the mechanical functions of bones and teeth. Calcium phosphate nucleation in collagenous structures follows distinctly different patterns in highly confined gap regions (nanoscale confinement) than in less confined extrafibrillar spaces (microscale confinement). Although the mechanism(s) driving these differences are still largely unknown, differences in the free energy for nucleation may explain these two mineralization behaviors. Here, we report on experimentally obtained nucleation energy barriers to intra- and extrafibrillar mineralization, using in situ X-ray scattering observations and classical nucleation theory. Polyaspartic acid, an extrafibrillar nucleation inhibitor, increases interfacial energies between nuclei and mineralization fluids. In contrast, the confined gap spaces inside collagen fibrils lower the energy barrier by reducing the reactive surface area of nuclei, decreasing the surface energy penalty. The confined gap geometry, therefore, guides the two-dimensional morphology and structure of bioapatite and changes the nucleation pathway by reducing the total energy barrier.
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Affiliation(s)
- Doyoon Kim
- Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Byeongdu Lee
- X-ray Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, NY, 10032, USA
| | - Young-Shin Jun
- Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA.
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20
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Huang G, Li F, Zhao X, Ma Y, Li Y, Lin M, Jin G, Lu TJ, Genin GM, Xu F. Functional and Biomimetic Materials for Engineering of the Three-Dimensional Cell Microenvironment. Chem Rev 2017; 117:12764-12850. [PMID: 28991456 PMCID: PMC6494624 DOI: 10.1021/acs.chemrev.7b00094] [Citation(s) in RCA: 469] [Impact Index Per Article: 67.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The cell microenvironment has emerged as a key determinant of cell behavior and function in development, physiology, and pathophysiology. The extracellular matrix (ECM) within the cell microenvironment serves not only as a structural foundation for cells but also as a source of three-dimensional (3D) biochemical and biophysical cues that trigger and regulate cell behaviors. Increasing evidence suggests that the 3D character of the microenvironment is required for development of many critical cell responses observed in vivo, fueling a surge in the development of functional and biomimetic materials for engineering the 3D cell microenvironment. Progress in the design of such materials has improved control of cell behaviors in 3D and advanced the fields of tissue regeneration, in vitro tissue models, large-scale cell differentiation, immunotherapy, and gene therapy. However, the field is still in its infancy, and discoveries about the nature of cell-microenvironment interactions continue to overturn much early progress in the field. Key challenges continue to be dissecting the roles of chemistry, structure, mechanics, and electrophysiology in the cell microenvironment, and understanding and harnessing the roles of periodicity and drift in these factors. This review encapsulates where recent advances appear to leave the ever-shifting state of the art, and it highlights areas in which substantial potential and uncertainty remain.
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Affiliation(s)
- Guoyou Huang
- MOE Key Laboratory of Biomedical Information
Engineering, School of Life Science and Technology, Xi’an Jiaotong
University, Xi’an 710049, People’s Republic of China
- Bioinspired Engineering and Biomechanics Center
(BEBC), Xi’an Jiaotong University, Xi’an 710049, People’s
Republic of China
| | - Fei Li
- Bioinspired Engineering and Biomechanics Center
(BEBC), Xi’an Jiaotong University, Xi’an 710049, People’s
Republic of China
- Department of Chemistry, School of Science,
Xi’an Jiaotong University, Xi’an 710049, People’s Republic
of China
| | - Xin Zhao
- Bioinspired Engineering and Biomechanics Center
(BEBC), Xi’an Jiaotong University, Xi’an 710049, People’s
Republic of China
- Interdisciplinary Division of Biomedical
Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong,
People’s Republic of China
| | - Yufei Ma
- MOE Key Laboratory of Biomedical Information
Engineering, School of Life Science and Technology, Xi’an Jiaotong
University, Xi’an 710049, People’s Republic of China
- Bioinspired Engineering and Biomechanics Center
(BEBC), Xi’an Jiaotong University, Xi’an 710049, People’s
Republic of China
| | - Yuhui Li
- MOE Key Laboratory of Biomedical Information
Engineering, School of Life Science and Technology, Xi’an Jiaotong
University, Xi’an 710049, People’s Republic of China
- Bioinspired Engineering and Biomechanics Center
(BEBC), Xi’an Jiaotong University, Xi’an 710049, People’s
Republic of China
| | - Min Lin
- MOE Key Laboratory of Biomedical Information
Engineering, School of Life Science and Technology, Xi’an Jiaotong
University, Xi’an 710049, People’s Republic of China
- Bioinspired Engineering and Biomechanics Center
(BEBC), Xi’an Jiaotong University, Xi’an 710049, People’s
Republic of China
| | - Guorui Jin
- MOE Key Laboratory of Biomedical Information
Engineering, School of Life Science and Technology, Xi’an Jiaotong
University, Xi’an 710049, People’s Republic of China
- Bioinspired Engineering and Biomechanics Center
(BEBC), Xi’an Jiaotong University, Xi’an 710049, People’s
Republic of China
| | - Tian Jian Lu
- Bioinspired Engineering and Biomechanics Center
(BEBC), Xi’an Jiaotong University, Xi’an 710049, People’s
Republic of China
- MOE Key Laboratory for Multifunctional Materials
and Structures, Xi’an Jiaotong University, Xi’an 710049,
People’s Republic of China
| | - Guy M. Genin
- MOE Key Laboratory of Biomedical Information
Engineering, School of Life Science and Technology, Xi’an Jiaotong
University, Xi’an 710049, People’s Republic of China
- Bioinspired Engineering and Biomechanics Center
(BEBC), Xi’an Jiaotong University, Xi’an 710049, People’s
Republic of China
- Department of Mechanical Engineering &
Materials Science, Washington University in St. Louis, St. Louis 63130, MO,
USA
- NSF Science and Technology Center for
Engineering MechanoBiology, Washington University in St. Louis, St. Louis 63130,
MO, USA
| | - Feng Xu
- MOE Key Laboratory of Biomedical Information
Engineering, School of Life Science and Technology, Xi’an Jiaotong
University, Xi’an 710049, People’s Republic of China
- Bioinspired Engineering and Biomechanics Center
(BEBC), Xi’an Jiaotong University, Xi’an 710049, People’s
Republic of China
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21
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Lipner J, Boyle JJ, Xia Y, Birman V, Genin GM, Thomopoulos S. Toughening of fibrous scaffolds by mobile mineral deposits. Acta Biomater 2017; 58:492-501. [PMID: 28532898 DOI: 10.1016/j.actbio.2017.05.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 05/10/2017] [Accepted: 05/15/2017] [Indexed: 10/19/2022]
Abstract
Partially mineralized fibrous tissue situated between tendon and bone is believed to be tougher than either tendon or bone, possibly serving as a compliant, energy absorptive, protective barrier between the two. This tissue does not reform following surgical repair (e.g., rotator cuff tendon-to-bone re-attachment) and might be a factor in the poor outcomes following such surgeries. Towards our long-term goal of tissue engineered solutions to functional tendon-to-bone re-attachment, we tested the hypotheses that partially mineralized fibrous matrices can derive toughness from mobility of mineral along their fibers, and that in such cases toughness is maximized at levels of mineralization sufficiently low to allow substantial mobility. Nanofibrous electrospun poly(lactic-co-glycolic acid) (PLGA) scaffolds mineralized for prescribed times were fabricated as model systems to test these hypotheses. Tensile tests performed at varying angles relative to the dominant fiber direction confirmed that mineral cross-linked PLGA nanofibers without adhering to them. Peel tests revealed that fracture toughness increased with mineralization time up to a peak value, then subsequently decreased with increasing mineralization time back to the baseline toughness of unmineralized scaffolds. These experimental results were predicted by a theoretical model combining mineral growth kinetics with fracture energetics, suggesting that toughness increased with mineralization time until mineral mobility was attenuated by steric hindrance, then returned to baseline levels following the rigid percolation threshold. Results supported our hypotheses, and motivate further study of the roles of mobile mineral particles in toughening the tendon-to-bone attachment. STATEMENT OF SIGNIFICANCE Effective surgical repair of interfaces between tendon and bone remains an unmet clinical need, in part due to a lack of understanding of how toughness is achieved in the healthy tissue. Using combined synthesis, experiment, and modeling approaches, the current work supported the hypothesis that toughening of a fibrous scaffold arises from brittle mineral particles that crosslink the fibers, but only if the particles are free to slide relative to the fibers. In the case of the tendon-to-bone interface, this suggests that partially mineralized tissue between tendon and bone, with mobile mineral but relatively low stiffness, may serve as a compliant, energy-absorbing barrier that guards against injury. These results suggest an opportunity for fabrication of tough and strong fibrous scaffolds for tissue engineering applications.
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22
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Deymier AC, An Y, Boyle JJ, Schwartz AG, Birman V, Genin GM, Thomopoulos S, Barber AH. Micro-mechanical properties of the tendon-to-bone attachment. Acta Biomater 2017; 56:25-35. [PMID: 28088669 DOI: 10.1016/j.actbio.2017.01.037] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2016] [Revised: 12/14/2016] [Accepted: 01/10/2017] [Indexed: 10/20/2022]
Abstract
The tendon-to-bone attachment (enthesis) is a complex hierarchical tissue that connects stiff bone to compliant tendon. The attachment site at the micrometer scale exhibits gradients in mineral content and collagen orientation, which likely act to minimize stress concentrations. The physiological micromechanics of the attachment thus define resultant performance, but difficulties in sample preparation and mechanical testing at this scale have restricted understanding of structure-mechanical function. Here, microscale beams from entheses of wild type mice and mice with mineral defects were prepared using cryo-focused ion beam milling and pulled to failure using a modified atomic force microscopy system. Micromechanical behavior of tendon-to-bone structures, including elastic modulus, strength, resilience, and toughness, were obtained. Results demonstrated considerably higher mechanical performance at the micrometer length scale compared to the millimeter tissue length scale, describing enthesis material properties without the influence of higher order structural effects such as defects. Micromechanical investigation revealed a decrease in strength in entheses with mineral defects. To further examine structure-mechanical function relationships, local deformation behavior along the tendon-to-bone attachment was determined using local image correlation. A high compliance zone near the mineralized gradient of the attachment was clearly identified and highlighted the lack of correlation between mineral distribution and strain on the low-mineral end of the attachment. This compliant region is proposed to act as an energy absorbing component, limiting catastrophic failure within the tendon-to-bone attachment through higher local deformation. This understanding of tendon-to-bone micromechanics demonstrates the critical role of micrometer scale features in the mechanics of the tissue. STATEMENT OF SIGNIFICANCE The tendon-to-bone attachment (enthesis) is a complex hierarchical tissue with features at a numerous scales that dissipate stress concentrations between compliant tendon and stiff bone. At the micrometer scale, the enthesis exhibits gradients in collagen and mineral composition and organization. However, the physiological mechanics of the enthesis at this scale remained unknown due to difficulty in preparing and testing micrometer scale samples. This study is the first to measure the tensile mechanical properties of the enthesis at the micrometer scale. Results demonstrated considerably enhanced mechanical performance at the micrometer length scale compared to the millimeter tissue length scale and identified a high-compliance zone near the mineralized gradient of the attachment. This understanding of tendon-to-bone micromechanics demonstrates the critical role of micrometer scale features in the mechanics of the tissue.
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23
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Rossetti L, Kuntz LA, Kunold E, Schock J, Müller KW, Grabmayr H, Stolberg-Stolberg J, Pfeiffer F, Sieber SA, Burgkart R, Bausch AR. The microstructure and micromechanics of the tendon-bone insertion. NATURE MATERIALS 2017; 16:664-670. [PMID: 28250445 DOI: 10.1038/nmat4863] [Citation(s) in RCA: 172] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 01/17/2017] [Indexed: 05/28/2023]
Abstract
The exceptional mechanical properties of the load-bearing connection of tendon to bone rely on an intricate interplay of its biomolecular composition, microstructure and micromechanics. Here we identify that the Achilles tendon-bone insertion is characterized by an interface region of ∼500 μm with a distinct fibre organization and biomolecular composition. Within this region, we identify a heterogeneous mechanical response by micromechanical testing coupled with multiscale confocal microscopy. This leads to localized strains that can be larger than the remotely applied strain. The subset of fibres that sustain the majority of loading in the interface area changes with the angle of force application. Proteomic analysis detects enrichment of 22 proteins in the interfacial region that are predominantly involved in cartilage and skeletal development as well as proteoglycan metabolism. The presented mechanisms mark a guideline for further biomimetic strategies to rationally design hard-soft interfaces.
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Affiliation(s)
- L Rossetti
- Lehrstuhl für Zellbiophysik, Technische Universität München, D-85748 Garching, Germany
| | - L A Kuntz
- Lehrstuhl für Zellbiophysik, Technische Universität München, D-85748 Garching, Germany
- Klinik für Orthopädie und Sportorthopädie, Klinikum rechts der Isar, Technische Universität München, D-81675 München, Germany
| | - E Kunold
- Center for Integrated Protein Science (CIPSM), Department of Chemistry, Technische Universität München, D-85747 Garching, Germany
| | - J Schock
- Lehrstuhl für Biomedizinische Physik, Physik-Department &Institut für Medizintechnik, Technische Universität München, D-85748 Garching, Germany
| | - K W Müller
- Institute for Computational Mechanics, Technische Universität München, D-85748 Garching, Germany
- Structural and Applied Mechanics Group, Computational Engineering Division, Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, California 94550, USA
| | - H Grabmayr
- Lehrstuhl für Zellbiophysik, Technische Universität München, D-85748 Garching, Germany
- Department of Physics and Center for Nanoscience, Ludwig Maximilian University, D-80539 Munich, Germany
| | - J Stolberg-Stolberg
- Klinik für Orthopädie und Sportorthopädie, Klinikum rechts der Isar, Technische Universität München, D-81675 München, Germany
- University Hospital Münster, Department of Trauma-, Hand- and Reconstructive Surgery, Albert-Schweitzer-Campus 1, Building W1, D-48149 Münster, Germany
| | - F Pfeiffer
- Lehrstuhl für Biomedizinische Physik, Physik-Department &Institut für Medizintechnik, Technische Universität München, D-85748 Garching, Germany
- Institut für diagnostische und interventionelle Radiologie, Klinikum rechts der Isar, Technische Universität München, D-81675 München, Germany
| | - S A Sieber
- Center for Integrated Protein Science (CIPSM), Department of Chemistry, Technische Universität München, D-85747 Garching, Germany
| | - R Burgkart
- Klinik für Orthopädie und Sportorthopädie, Klinikum rechts der Isar, Technische Universität München, D-81675 München, Germany
| | - A R Bausch
- Lehrstuhl für Zellbiophysik, Technische Universität München, D-85748 Garching, Germany
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24
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Claeson AA, Barocas VH. Planar biaxial extension of the lumbar facet capsular ligament reveals significant in-plane shear forces. J Mech Behav Biomed Mater 2016; 65:127-136. [PMID: 27569760 DOI: 10.1016/j.jmbbm.2016.08.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 08/02/2016] [Accepted: 08/09/2016] [Indexed: 10/21/2022]
Abstract
The lumbar facet capsular ligament (FCL) articulates with six degrees of freedom during spinal motions of flexion/extension, lateral bending, and axial rotation. The lumbar FCL is composed of highly aligned collagen fiber bundles on the posterior surface (oriented primarily laterally between the rigid articular facets) and irregularly oriented elastin on the anterior surface. Because the FCL is a capsule, it has multiple insertion sites across the lumbar facet joint, which, along with its material structure, give rise to complicated deformations in vivo. We performed planar equibiaxial mechanical tests on excised healthy cadaveric lumbar FCLs (n=6) to extract normal and shear reaction forces, and fit sample-specific two-fiber-family finite element models to the experimental force data. An eight-parameter anisotropic, hyperelastic model was used. Shear forces at maximum extension (mean values of 1.68N and 3.01N in the two directions) were of comparable magnitude to the normal forces perpendicular to the aligned collagen fiber bundles (4.67N) but smaller than normal forces in the fiber direction (16.11N). Inclusion of the experimental shear forces in the model optimization yielded fits with highly aligned fibers oriented at a specific angle across all samples, typically with one fiber population aligned nearly horizontally and the other at an oblique angle. Conversely, models fit to only the normal force data resulted in a broad range of fiber angles with low specificity. We found that shear forces generated through planar equibiaxial extension aided the model fit in describing the anisotropic nature of the FCL surface.
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Affiliation(s)
- Amy A Claeson
- Department of Biomedical Engineering, University of Minnesota - Twin Cities, Minneapolis, MN, USA
| | - Victor H Barocas
- Department of Biomedical Engineering, University of Minnesota - Twin Cities, Minneapolis, MN, USA.
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25
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Kim D, Lee B, Thomopoulos S, Jun YS. In Situ Evaluation of Calcium Phosphate Nucleation Kinetics and Pathways during Intra- and Extrafibrillar Mineralization of Collagen Matrices. CRYSTAL GROWTH & DESIGN 2016; 16:5359-5366. [PMID: 27891066 PMCID: PMC5120680 DOI: 10.1021/acs.cgd.6b00864] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
We revealed that nucleation sites within collagen fibrils determined pathways for calcium phosphate (CaP) nucleation and its transformation, from amorphous species to crystalline plates, during the biomineralization process. Using in situ small-angle X-ray scattering (SAXS), we examined the nucleation and growth of CaP within collagen matrices and elucidated how a nucleation inhibitor, polyaspartic acid (pAsp), governs mineralization kinetics and pathways at multiple length scales. Mineralization without pAsp led initially to spherical aggregates of CaP in the entire extrafibrillar spaces. With time, the spherical aggregates transformed into plates at the outermost surface of the collagen matrix, preventing intrafibrillar mineralization inside. However, mineralization with pAsp led directly to the formation of intrafibrillar CaP plates with a spatial distribution gradient through the depth of the matrix. The results illuminate mineral nucleation kinetics and real-time nanoparticle distributions within organic matrices in solutions containing body fluid components. Because the macroscale mechanical properties of collagen matrices depend on their mineral content, phase, and arrangement at the nanoscale, this study contributes to better design and fabrication of biomaterials for regenerative medicine.
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Affiliation(s)
- Doyoon Kim
- Department of Energy, Environmental & Chemical Engineering, Washington University, St. Louis, Missouri 63130, United States
| | - Byeongdu Lee
- X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, New York 10032-3072, United States
| | - Young-Shin Jun
- Department of Energy, Environmental & Chemical Engineering, Washington University, St. Louis, Missouri 63130, United States
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26
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Smith LJ, Deymier AC, Boyle JJ, Li Z, Linderman SW, Pasteris JD, Xia Y, Genin GM, Thomopoulos S. Tunability of collagen matrix mechanical properties via multiple modes of mineralization. Interface Focus 2016; 6:20150070. [PMID: 26855755 DOI: 10.1098/rsfs.2015.0070] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Functionally graded, mineralized collagen tissues exist at soft-to-hard material attachments throughout the body. However, the details of how collagen and hydroxyapatite mineral (HA) interact are not fully understood, hampering efforts to develop tissue-engineered constructs that can assist with repair of injuries at the attachments of soft tissues to bone. In this study, spatial control of mineralization was achieved in collagen matrices using simulated body fluids (SBFs). Based upon previous observations of poor bonding between reconstituted collagen and HA deposited using SBF, we hypothesized that mineralizing collagen in the presence of fetuin (which inhibits surface mineralization) would lead to more mineral deposition within the scaffold and therefore a greater increase in stiffness and toughness compared with collagen mineralized without fetuin. We tested this hypothesis through integrated synthesis, mechanical testing and modelling of graded, mineralized reconstituted collagen constructs. Results supported the hypothesis, and further suggested that mineralization on the interior of reconstituted collagen constructs, as promoted by fetuin, led to superior bonding between HA and collagen. The results provide us guidance for the development of mineralized collagen scaffolds, with implications for bone and tendon-to-bone tissue engineering.
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Affiliation(s)
- Lester J Smith
- Department of Orthopaedic Surgery , Washington University , St Louis, MO 63130 , USA
| | - Alix C Deymier
- Department of Orthopaedic Surgery , Washington University , St Louis, MO 63130 , USA
| | - John J Boyle
- Department of Orthopaedic Surgery, Washington University, St Louis, MO 63130, USA; Department of Biomedical Engineering, Washington University, St Louis, MO 63130, USA
| | - Zhen Li
- Department of Earth and Planetary Sciences , Washington University , St Louis, MO 63130 , USA
| | - Stephen W Linderman
- Department of Orthopaedic Surgery, Washington University, St Louis, MO 63130, USA; Department of Biomedical Engineering, Washington University, St Louis, MO 63130, USA
| | - Jill D Pasteris
- Department of Earth and Planetary Sciences , Washington University , St Louis, MO 63130 , USA
| | - Younan Xia
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA; School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA; School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Guy M Genin
- Department of Mechanical Engineering and Materials Science , Washington University , St Louis, MO 63130 , USA
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA; Department of Biomedical Engineering, Columbia University, New York, NY 10032, USA
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27
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Claeson AA, Yeh YJ, Black AJ, Akkin T, Barocas VH. Marker-Free Tracking of Facet Capsule Motion Using Polarization-Sensitive Optical Coherence Tomography. Ann Biomed Eng 2015; 43:2953-66. [PMID: 26055969 DOI: 10.1007/s10439-015-1349-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 05/27/2015] [Indexed: 12/28/2022]
Abstract
We proposed and tested a method by which surface strains of biological tissues can be captured without the use of fiducial markers by instead, utilizing the inherent structure of the tissue. We used polarization-sensitive optical coherence tomography (PS OCT) to obtain volumetric data through the thickness and across a partial surface of the lumbar facet capsular ligament during three cases of static bending. Reflectivity and phase retardance were calculated from two polarization channels, and a power spectrum analysis was performed on each a-line to extract the dominant banding frequency (a measure of degree of fiber alignment) through the maximum value of the power spectrum (maximum power). Maximum powers of all a-lines for each case were used to create 2D visualizations, which were subsequently tracked via digital image correlation. In-plane strains were calculated from measured 2D deformations and converted to 3D surface strains by including out-of-plane motion obtained from the PS OCT image. In-plane strains correlated with 3D strains (R(2) ≥ 0.95). Using PS OCT for marker-free motion tracking of biological tissues is a promising new technique because it relies on the structural characteristics of the tissue to monitor displacement instead of external fiducial markers.
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Affiliation(s)
- Amy A Claeson
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
| | - Yi-Jou Yeh
- Department of Electrical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Adam J Black
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Taner Akkin
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Victor H Barocas
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
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28
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Lipner J, Liu W, Liu Y, Boyle J, Genin GM, Xia Y, Thomopoulos S. The mechanics of PLGA nanofiber scaffolds with biomimetic gradients in mineral for tendon-to-bone repair. J Mech Behav Biomed Mater 2014; 40:59-68. [PMID: 25194525 DOI: 10.1016/j.jmbbm.2014.08.002] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 08/01/2014] [Accepted: 08/05/2014] [Indexed: 01/08/2023]
Abstract
Attachment of dissimilar materials is prone to failure due to stress concentrations that can arise their interface. A compositionally or structurally graded transition can dissipate these stress concentrations and thereby toughen an attachment. The interface between compliant tendon and stiff bone utilizes a monotonic change in hydroxylapatite mineral ("mineral") content to produce a gradient in mechanical properties and mitigate stress concentrations. Previous efforts to mimic the natural tendon-to-bone attachment have included electrospun nanofibrous polymer scaffolds with gradients in mineral. Mineralization of the nanofiber scaffolds has typically been achieved using simulated body fluid (SBF). Depending on the specific formulation of SBF, mineral morphologies ranged from densely packed small crystals to platelike crystal florets. Although this mineralization of scaffolds produced increases in modulus, the peak modulus achieved remained significantly below that of bone. Missing from these prior empirical approaches was insight into the effect of mineral morphology on scaffold mechanics and on the potential for the approach to ultimately achieve moduli approaching that of bone. Here, we applied two mineralization methods to generate scaffolds with spatial gradations in mineral content, and developed methods to quantify the stiffening effects and evaluate them in the context of theoretical bounds. We asked whether either of the mineralization methods we developed holds potential to achieve adequate stiffening of the scaffold, and tested the hypothesis that the smoother, denser mineral coating could attain more potent stiffening effects. Testing this hypothesis required development of and comparison to homogenization bounds, and development of techniques to estimate mineral volume fractions and spatial gradations in modulus. For both mineralization strategies, energy dispersive X-ray analysis demonstrated the formation of linear gradients in mineral concentration along the length of the scaffolds, and Raman spectroscopic analysis revealed that the mineral produced was hydroxylapatite. Mechanical testing showed that the stiffness gradient using the new method was significantly steeper. By analyzing the scaffolds using micromechanical modeling techniques and extrapolating from our experimental results, we present evidence that the new mineralization protocol has the potential to achieve levels of stiffness adequate to contribute to enhanced repair of tendon-to-bone attachments.
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Affiliation(s)
- J Lipner
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA; Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA
| | - W Liu
- Department of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Y Liu
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, MO, USA
| | - J Boyle
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA; Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA
| | - G M Genin
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, MO, USA
| | - Y Xia
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
| | - S Thomopoulos
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA; Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA.
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