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Zhang Q, Wang P, Fang X, Lin F, Fang J, Xiong C. Collagen gel contraction assays: From modelling wound healing to quantifying cellular interactions with three-dimensional extracellular matrices. Eur J Cell Biol 2022; 101:151253. [PMID: 35785635 DOI: 10.1016/j.ejcb.2022.151253] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2021] [Revised: 06/06/2022] [Accepted: 06/24/2022] [Indexed: 12/12/2022] Open
Abstract
Cells respond to and actively remodel the extracellular matrix (ECM). The dynamic and bidirectional interaction between cells and ECM, especially their mechanical interactions, has been found to play an essential role in triggering a series of complex biochemical and biomechanical signal pathways and in regulating cellular functions and behaviours. The collagen gel contraction assay (CGCA) is a widely used method to investigate cell-ECM interactions in 3D environments and provides a mechanically associated readout reflecting 3D cellular contractility. In this review, we summarize various versions of CGCA, with an emphasis on recent high-throughput and low-consumption CGCA techniques. More importantly, we focus on the technique of force monitoring during the contraction of collagen gel, which provides a quantitative characterization of the overall forces generated by all the resident cells in the collagen hydrogel. Accordingly, we present recent biological applications of the CGCA, which have expanded from the initial wound healing model to other studies concerning cell-ECM interactions, including fibrosis, cancer, tissue repair and the preparation of biomimetic microtissues.
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Affiliation(s)
- Qing Zhang
- Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China
| | - Pudi Wang
- Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China
| | - Xu Fang
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Feng Lin
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325000, China
| | - Jing Fang
- Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China; Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Chunyang Xiong
- Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China; Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China; Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325000, China.
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2
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Siadat SM, Silverman AA, Susilo ME, Paten JA, DiMarzio CA, Ruberti JW. Development of Fluorescently Labeled, Functional Type I Collagen Molecules. Macromol Biosci 2021; 22:e2100144. [PMID: 34856056 DOI: 10.1002/mabi.202100144] [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: 04/12/2021] [Revised: 10/22/2021] [Indexed: 11/11/2022]
Abstract
While de novo collagen fibril formation is well-studied, there are few investigations into the growth and remodeling of extant fibrils, where molecular collagen incorporation into and erosion from the fibril surface must delicately balance during fibril growth and remodeling. Observing molecule/fibril interactions is difficult, requiring the tracking of molecular dynamics while, at the same time, minimizing the effect of the observation on fibril structure and assembly. To address the observation-interference problem, exogenous collagen molecules are tagged with small fluorophores and the fibrillogenesis kinetics of labeled collagen molecules as well as the structure and network morphology of assembled fibrils are examined. While excessive labeling significantly disturbs fibrillogenesis kinetics and network morphology of assembled fibrils, adding less than ≈1.2 labels per collagen molecule preserves these characteristics. Applications of the functional, labeled collagen probe are demonstrated in both cellular and acellular systems. The functional, labeled collagen associates strongly with native fibrils and when added to an in vitro model of corneal stromal development at low concentration, the labeled collagen is incorporated into a fine extracellular matrix (ECM) network associated with the cells within 24 h.
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Affiliation(s)
| | | | - Monica E Susilo
- Department of Bioengineering, Northeastern University, Boston, MA, 02115, USA
| | - Jeffrey A Paten
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02134, USA
| | - Charles A DiMarzio
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA, 02115, USA
| | - Jeffrey W Ruberti
- Department of Bioengineering, Northeastern University, Boston, MA, 02115, USA
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3
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McKay TB, Guo X, Hutcheon AEK, Karamichos D, Ciolino JB. Methods for Investigating Corneal Cell Interactions and Extracellular Vesicles In Vitro. ACTA ACUST UNITED AC 2021; 89:e114. [PMID: 32986311 DOI: 10.1002/cpcb.114] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Science and medicine have become increasingly "human-centric" over the years. A growing shift away from the use of animals in basic research has led to the development of sophisticated in vitro models of various tissues utilizing human-derived cells to study physiology and disease. The human cornea has likewise been modeled in vitro using primary cells derived from corneas obtained from cadavers or post-transplantation. By utilizing a cell's intrinsic ability to maintain its tissue phenotype in a pre-designed microenvironment containing the required growth factors, physiological temperature, and humidity, tissue-engineered corneas can be grown and maintained in culture for relatively long periods of time on the scale of weeks to months. Due to its transparency and avascularity, the cornea is an optimal tissue for studies of extracellular matrix and cell-cell interactions, toxicology and permeability of drugs, and underlying mechanisms of scarring and tissue regeneration. This paper describes methods for the cultivation of corneal keratocytes, fibroblasts, epithelial, and endothelial cells for in vitro applications. We also provide detailed, step-by-step protocols for assembling and culturing 3D constructs of the corneal stroma, epithelial- and endothelial-stromal co-cultures and isolation of extracellular vesicles. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Isolating and culturing human corneal keratocytes and fibroblasts Basic Protocol 2: Isolating and culturing human corneal epithelial cells Basic Protocol 3: Isolating and culturing human corneal endothelial cells Basic Protocol 4: 3D corneal stromal construct assembly Basic Protocol 5: 3D corneal epithelial-stromal construct assembly Basic Protocol 6: 3D corneal endothelial-stromal construct assembly Basic Protocol 7: Isolating extracellular vesicles from corneal cell conditioned medium Support Protocol: Cryopreserving human corneal fibroblasts, corneal epithelial cells, and corneal endothelial cells.
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Affiliation(s)
- Tina B McKay
- Schepens Eye Research Institute of Massachusetts Eye and Ear and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts
| | - Xiaoqing Guo
- Schepens Eye Research Institute of Massachusetts Eye and Ear and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts
| | - Audrey E K Hutcheon
- Schepens Eye Research Institute of Massachusetts Eye and Ear and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts
| | - Dimitrios Karamichos
- Department of Pharmaceutical Sciences and The North Texas Eye Research Institute, University of North Texas Health Science Center, Fort Worth, Texas
| | - Joseph B Ciolino
- Schepens Eye Research Institute of Massachusetts Eye and Ear and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts
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4
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Siadat SM, Silverman AA, DiMarzio CA, Ruberti JW. Measuring collagen fibril diameter with differential interference contrast microscopy. J Struct Biol 2021; 213:107697. [PMID: 33545351 DOI: 10.1016/j.jsb.2021.107697] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 12/04/2020] [Accepted: 01/12/2021] [Indexed: 02/01/2023]
Abstract
Collagen fibrils, linear arrangements of collagen monomers, 20-500 nm in diameter, comprising hundreds of molecules in their cross-section, are the fundamental structural unit in a variety of load-bearing tissues such as tendons, ligaments, skin, cornea, and bone. These fibrils often assemble into more complex structures, providing mechanical stability, strength, or toughness to the host tissue. Unfortunately, there is little information available on individual fibril dynamics, mechanics, growth, aggregation and remodeling because they are difficult to image using visible light as a probe. The principle quantity of interest is the fibril diameter, which is difficult to extract accurately, dynamically, in situ and non-destructively. An optical method, differential interference contrast (DIC) microscopy has been used to visualize dynamic structures that are as small as microtubules (25 nm diameter) and has been shown to be sensitive to the size of objects smaller than the wavelength of light. In this investigation, we take advantage of DIC microscopy's ability to report dimensions of nanometer scale objects to generate a curve that relates collagen diameter to DIC edge intensity shift (DIC-EIS). We further calibrate the curve using electron microscopy and demonstrate a linear correlation between fibril diameter and the DIC-EIS. Using a non-oil immersion, 40x objective (NA 0.6), collagen fibril diameters between ~100 nm to ~ 300 nm could be obtained with ±11 and ±4 nm accuracy for dehydrated and hydrated fibrils, respectively. This simple, nondestructive, label free method should advance our ability to directly examine fibril dynamics under experimental conditions that are physiologically relevant.
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Affiliation(s)
| | | | - Charles A DiMarzio
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA
| | - Jeffrey W Ruberti
- Department of Bioengineering, Northeastern University, Boston, MA 02115, USA.
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5
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Petroll WM, Varner VD, Schmidtke DW. Keratocyte mechanobiology. Exp Eye Res 2020; 200:108228. [PMID: 32919993 PMCID: PMC7655662 DOI: 10.1016/j.exer.2020.108228] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/31/2020] [Accepted: 09/02/2020] [Indexed: 01/22/2023]
Abstract
In vivo, corneal keratocytes reside within a complex 3D extracellular matrix (ECM) consisting of highly aligned collagen lamellae, growth factors, and other extracellular matrix components, and are subjected to various mechanical stimuli during developmental morphogenesis, fluctuations in intraocular pressure, and wound healing. The process by which keratocytes convert changes in mechanical stimuli (e.g. local topography, applied force, ECM stiffness) into biochemical signaling is known as mechanotransduction. Activation of the various mechanotransductive pathways can produce changes in cell migration, proliferation, and differentiation. Here we review how corneal keratocytes respond to and integrate different biochemical and biophysical factors. We first highlight how growth factors and other cytokines regulate the activity of Rho GTPases, cytoskeletal remodeling, and ultimately the mechanical phenotype of keratocytes. We then discuss how changes in the mechanical properties of the ECM have been shown to regulate keratocyte behavior in sophisticated 2D and 3D experimental models of the corneal microenvironment. Finally, we discuss how ECM topography and protein composition can modulate cell phenotypes, and review the different methods of fabricating in vitro mimics of corneal ECM topography, novel approaches for examining topographical effects in vivo, and the impact of different ECM glycoproteins and proteoglycans on keratocyte behavior.
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Affiliation(s)
- W Matthew Petroll
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Victor D Varner
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, USA; Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - David W Schmidtke
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, USA; Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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6
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McLean JP, Fang S, Gallos G, Myers KM, Hendon CP. Three-dimensional collagen fiber mapping and tractography of human uterine tissue using OCT. BIOMEDICAL OPTICS EXPRESS 2020; 11:5518-5541. [PMID: 33149968 PMCID: PMC7587264 DOI: 10.1364/boe.397041] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/23/2020] [Accepted: 07/30/2020] [Indexed: 05/10/2023]
Abstract
Automatic quantification and visualization of 3-D collagen fiber architecture using Optical Coherence Tomography (OCT) has previously relied on polarization information and/or prior knowledge of tissue-specific fiber architecture. This study explores image processing, enhancement, segmentation, and detection algorithms to map 3-D collagen fiber architecture from OCT images alone. 3-D fiber mapping, histogram analysis, and 3-D tractography revealed fiber groupings and macro-organization previously unseen in uterine tissue samples. We applied our method on centimeter-scale mosaic OCT volumes of uterine tissue blocks from pregnant and non-pregnant specimens revealing a complex, patient-specific network of fibrous collagen and myocyte bundles.
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Affiliation(s)
- James P. McLean
- Department of Electrical Engineering, Columbia University, New York, NY 10027, USA
| | - Shuyang Fang
- Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA
| | - George Gallos
- Department of Anesthesiology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Kristin M. Myers
- Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA
| | - Christine P. Hendon
- Department of Electrical Engineering, Columbia University, New York, NY 10027, USA
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7
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Koudouna E, Spurlin J, Babushkina A, Quantock AJ, Jester JV, Lwigale P. Recapitulation of normal collagen architecture in embryonic wounded corneas. Sci Rep 2020; 10:13815. [PMID: 32796881 PMCID: PMC7427794 DOI: 10.1038/s41598-020-70658-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 07/31/2020] [Indexed: 02/06/2023] Open
Abstract
Wound healing is characterized by cell and extracellular matrix changes mediating cell migration, fibrosis, remodeling and regeneration. We previously demonstrated that chick fetal wound healing shows a regenerative phenotype regarding the cellular and molecular organization of the cornea. However, the chick corneal stromal structure is remarkably complex in the collagen fiber/lamellar organization, involving branching and anastomosing of collagen bundles. It is unknown whether the chick fetal wound healing is capable of recapitulating this developmentally regulated organization pattern. The purpose of this study was to examine the three-dimensional collagen architecture of wounded embryonic corneas, whilst identifying temporal and spatial changes in collagen organization during wound healing. Linear corneal wounds that traversed the epithelial layer, Bowman´s layer, and anterior stroma were generated in chick corneas on embryonic day 7. Irregular thin collagen fibers are present in the wounded cornea during the early phases of wound healing. As wound healing progresses, the collagen organization dramatically changes, acquiring an orthogonal arrangement. Fourier transform analysis affirmed this observation and revealed that adjacent collagen lamellae display an angular displacement progressing from the epithelium layer towards the endothelium. These data indicate that the collagen organization of the wounded embryonic cornea recapitulate the native macrostructure.
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Affiliation(s)
- Elena Koudouna
- Gavin Herbert Eye Institute, University of California Irvine, Irvine, CA, USA.,Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, UK
| | - James Spurlin
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, USA
| | - Anna Babushkina
- Department of Biosciences, Rice University, Houston, TX, USA
| | - Andrew J Quantock
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, UK
| | - James V Jester
- Gavin Herbert Eye Institute, University of California Irvine, Irvine, CA, USA
| | - Peter Lwigale
- Department of Biosciences, Rice University, Houston, TX, USA.
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8
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McLean JP, Gan Y, Lye TH, Qu D, Lu HH, Hendon CP. High-speed collagen fiber modeling and orientation quantification for optical coherence tomography imaging. OPTICS EXPRESS 2019; 27:14457-14471. [PMID: 31163895 PMCID: PMC6825605 DOI: 10.1364/oe.27.014457] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 04/18/2019] [Accepted: 04/24/2019] [Indexed: 05/03/2023]
Abstract
Quantifying collagen fiber architecture has clinical and scientific relevance across a variety of tissue types and adds functionality to otherwise largely qualitative imaging modalities. Optical coherence tomography (OCT) is uniquely suited for this task due to its ability to capture the collagen microstructure over larger fields of view than traditional microscopy. Existing image processing techniques for quantifying fiber architecture, while accurate and effective, are very slow for processing large datasets and tend to lack structural specificity. We describe here a computationally efficient method for quantifying and visualizing collagen fiber organization. The algorithm is demonstrated on swine atria, bovine anterior cruciate ligament, and human cervical tissue samples. Additionally, we show an improved performance for images with crimped fiber textures and low signal to noise when compared to similar methods.
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Affiliation(s)
- James P. McLean
- Electrical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, 1300 West 120th Street, New York, NY 10025,
USA
| | - Yu Gan
- Electrical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, 1300 West 120th Street, New York, NY 10025,
USA
| | - Theresa H. Lye
- Electrical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, 1300 West 120th Street, New York, NY 10025,
USA
| | - Dovina Qu
- Biomedical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, 1300 West 120th Street, New York, NY 10025,
USA
| | - Helen H. Lu
- Biomedical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, 1300 West 120th Street, New York, NY 10025,
USA
| | - Christine P. Hendon
- Electrical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, 1300 West 120th Street, New York, NY 10025,
USA
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9
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Koudouna E, Mikula E, Brown DJ, Young RD, Quantock AJ, Jester JV. Cell regulation of collagen fibril macrostructure during corneal morphogenesis. Acta Biomater 2018; 79:96-112. [PMID: 30170195 DOI: 10.1016/j.actbio.2018.08.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 08/06/2018] [Accepted: 08/17/2018] [Indexed: 11/26/2022]
Abstract
While tissue form and function is highly dependent upon tissue-specific collagen composition and organization, little is known of the mechanisms controlling the bundling of collagen fibrils into fibers and larger structural designs that lead to the formation of bones, tendons and other tissues. Using the cornea as a model system, our previous 3 dimensional mapping of collagen fiber organization has demonstrated that macrostructural organization of collagen fibers involving interweaving, branching and anastomosing plays a critical role in controlling mechanical stiffness, corneal shape and refractive power. In this work, the cellular and mechanical mechanisms regulating critical events in the assembly of collagen macrostructure are analysed in the developing chicken cornea. We elucidated the temporal events leading to adult corneal structure and determined the effects of intraocular pressure (IOP) on the organization of the collagen macrostructure. Our findings indicate that the complex adult collagen organization begins to appear on embryonic day 10 (E10) after deposition of the primary stroma and full invasion of keratocytes. Importantly, organizational changes in keratocytes appearing at E9 preceded and predicted later changes in collagen organization. Corneal collagen organization remained unaffected when the development of IOP was blocked at E4. These findings support a primary role for keratocytes in controlling stromal organization, mechanical stiffness and corneal shape that are not regulated by the IOP. Our findings also suggest that the avian cornea represents an excellent experimental model for elucidating key regulatory steps and mechanisms controlling the collagen fiber organization that is critical to determining tissue form and function. STATEMENT OF SIGNIFICANCE This work by using an ex ovo model system, begins to investigate the potential mechanisms controlling collagen fibril macrostructure. In particular, this work highlights a convergent role for the corneal keratocytes in organizing the complex collagen macrostructure, necessary to support high visual acuity. Our data supports that the intraocular pressure does not influence collagen fibril macrostructure and suggest that the avian cornea represents an excellent experimental model for elucidating key regulatory steps and mechanisms controlling the collagen fiber organization that is critical to determining tissue form and function. Clearly understanding the cellular and molecular mechanisms that underlie collagen fibril macrostructure will be highly beneficial for future tissue engineering and regenerative medicine applications.
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10
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Kivanany PB, Grose KC, Tippani M, Su S, Petroll WM. Assessment of Corneal Stromal Remodeling and Regeneration after Photorefractive Keratectomy. Sci Rep 2018; 8:12580. [PMID: 30135552 PMCID: PMC6105640 DOI: 10.1038/s41598-018-30372-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 07/16/2018] [Indexed: 01/17/2023] Open
Abstract
This study utilizes high resolution multi-dimensional imaging to identify temporal and spatial changes in cell/extracellular matrix (ECM) patterning mediating cell migration, fibrosis, remodeling and regeneration during wound healing. Photorefractive keratectomy (PRK) was performed on rabbits. In some cases, 5([4,6-dichlorotriazin-2yl]-amino)fluorescein (DTAF) was applied immediately after surgery to differentiate native vs. cell-secreted collagen. Corneas were assessed 3–180 days postoperatively using in vivo confocal microscopy, and cell/ECM patterning was evaluated in situ using multiphoton and second harmonic generation (SHG) imaging. 7 days post-PRK, migrating fibroblasts below the ablation site were co-aligned with the stromal lamellae. At day 21, randomly patterned myofibroblasts developed on top of the ablation site; whereas cells underneath were elongated, co-aligned with collagen, and lacked stress fibers. Over time, fibrotic tissue was remodeled into more transparent stromal lamellae. By day 180, stromal thickness was almost completely restored. Stromal regrowth occurred primarily below the ablation interface, and was characterized by co-localization of gaps in DTAF labeling with elongated cells and SHG collagen signaling. Punctate F-actin labeling was detected along cells co-aligned with DTAF and non-DTAF labeled collagen, suggesting cell-ECM interactions. Overall, collagen lamellae appear to provide a template for fibroblast patterning during wound healing that mediates stromal repopulation, regeneration and remodeling.
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Affiliation(s)
- Pouriska B Kivanany
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA.,Biomedical Engineering Graduate Program, UT Southwestern Medical Center, Dallas, TX, USA
| | - Kyle C Grose
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Madhavi Tippani
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Shan Su
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - W Matthew Petroll
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA. .,Biomedical Engineering Graduate Program, UT Southwestern Medical Center, Dallas, TX, USA.
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11
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McLean JP, Ling Y, Hendon CP. Frequency-constrained robust principal component analysis: a sparse representation approach to segmentation of dynamic features in optical coherence tomography imaging. OPTICS EXPRESS 2017; 25:25819-25830. [PMID: 29041245 PMCID: PMC5644470 DOI: 10.1364/oe.25.025819] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 10/05/2017] [Accepted: 10/05/2017] [Indexed: 05/18/2023]
Abstract
Sparse representation theory is an exciting area of research with recent applications in medical imaging and detection, segmentation, and quantitative analysis of biological processes. We present a variant on the robust-principal component analysis (RPCA) algorithm, called frequency constrained RPCA (FC-RPCA), for selectively segmenting dynamic phenomena that exhibit spectra within a user-defined range of frequencies. The algorithm lacks subjective parameter tuning and demonstrates robust segmentation in datasets containing multiple motion sources and high amplitude noise. When tested on 17 ex-vivo, time lapse optical coherence tomography (OCT) B-scans of human ciliated epithelium, segmentation accuracies ranged between 91-99% and consistently out-performed traditional RPCA.
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12
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Zhang W, Chen J, Backman LJ, Malm AD, Danielson P. Surface Topography and Mechanical Strain Promote Keratocyte Phenotype and Extracellular Matrix Formation in a Biomimetic 3D Corneal Model. Adv Healthc Mater 2017; 6. [PMID: 28026154 DOI: 10.1002/adhm.201601238] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 11/28/2016] [Indexed: 11/09/2022]
Abstract
The optimal functionality of the native corneal stroma is mainly dependent on the well-ordered arrangement of extracellular matrix (ECM) and the pressurized structure. In order to develop an in vitro corneal model, it is crucial to mimic the in vivo microenvironment of the cornea. In this study, the influence of surface topography and mechanical strain on keratocyte phenotype and ECM formation within a biomimetic 3D corneal model is studied. By modifying the surface topography of materials, it is found that patterned silk fibroin film with 600 grooves mm-1 optimally supports cell alignment and ECM arrangement. Furthermore, treatment with 3% dome-shaped mechanical strain, which resembles the shape and mechanics of native cornea, significantly enhances the expression of keratocyte markers as compared to flat-shaped strain. Accordingly, a biomimetic 3D corneal model, in the form of a collagen-modified, silk fibroin-patterned construct subjected to 3% dome-shaped strain, is created. Compared to traditional 2D cultures, it supports a significantly higher expression of keratocyte and ECM markers, and in conclusion better maintains keratocyte phenotype, alignment, and fusiform cell shape. Therefore, the novel biomimetic 3D corneal model developed in this study serves as a useful in vitro 3D culture model to improve current 2D cultures for corneal studies.
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Affiliation(s)
- Wei Zhang
- Department of Integrative Medical Biology, Anatomy; Umeå University; Umeå 90187 Sweden
| | - Jialin Chen
- Department of Integrative Medical Biology, Anatomy; Umeå University; Umeå 90187 Sweden
| | - Ludvig J. Backman
- Department of Integrative Medical Biology, Anatomy; Umeå University; Umeå 90187 Sweden
| | - Adam D. Malm
- Department of Integrative Medical Biology, Anatomy; Umeå University; Umeå 90187 Sweden
| | - Patrik Danielson
- Department of Integrative Medical Biology, Anatomy; Umeå University; Umeå 90187 Sweden
- Department of Clinical Sciences, Ophthalmology; Umeå University; Umeå 90187 Sweden
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