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Gu B, Han K, Cao H, Huang X, Li X, Mao M, Zhu H, Cai H, Li D, He J. Heart-on-a-chip systems with tissue-specific functionalities for physiological, pathological, and pharmacological studies. Mater Today Bio 2024; 24:100914. [PMID: 38179431 PMCID: PMC10765251 DOI: 10.1016/j.mtbio.2023.100914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 12/08/2023] [Accepted: 12/12/2023] [Indexed: 01/06/2024] Open
Abstract
Recent advances in heart-on-a-chip systems hold great promise to facilitate cardiac physiological, pathological, and pharmacological studies. This review focuses on the development of heart-on-a-chip systems with tissue-specific functionalities. For one thing, the strategies for developing cardiac microtissues on heart-on-a-chip systems that closely mimic the structures and behaviors of the native heart are analyzed, including the imitation of cardiac structural and functional characteristics. For another, the development of techniques for real-time monitoring of biophysical and biochemical signals from cardiac microtissues on heart-on-a-chip systems is introduced, incorporating cardiac electrophysiological signals, contractile activity, and biomarkers. Furthermore, the applications of heart-on-a-chip systems in intelligent cardiac studies are discussed regarding physiological/pathological research and pharmacological assessment. Finally, the future development of heart-on-a-chip toward a higher level of systematization, integration, and maturation is proposed.
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Affiliation(s)
- Bingsong Gu
- State Key Laboratory for Manufacturing System Engineering, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Medical Products Administration (NMPA) Key Laboratory for Research and Evaluation of Additive Manufacturing Medical Devices, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Innovation Platform (Center) for Industry-Education Integration of Medical Technology, Xi'an Jiaotong University, China
| | - Kang Han
- State Key Laboratory for Manufacturing System Engineering, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Medical Products Administration (NMPA) Key Laboratory for Research and Evaluation of Additive Manufacturing Medical Devices, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Innovation Platform (Center) for Industry-Education Integration of Medical Technology, Xi'an Jiaotong University, China
| | - Hanbo Cao
- Shaanxi Provincial Institute for Food and Drug Control, Xi’ an, 710065, China
| | - Xinxin Huang
- State Key Laboratory for Manufacturing System Engineering, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Medical Products Administration (NMPA) Key Laboratory for Research and Evaluation of Additive Manufacturing Medical Devices, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Innovation Platform (Center) for Industry-Education Integration of Medical Technology, Xi'an Jiaotong University, China
| | - Xiao Li
- State Key Laboratory for Manufacturing System Engineering, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Medical Products Administration (NMPA) Key Laboratory for Research and Evaluation of Additive Manufacturing Medical Devices, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Innovation Platform (Center) for Industry-Education Integration of Medical Technology, Xi'an Jiaotong University, China
| | - Mao Mao
- State Key Laboratory for Manufacturing System Engineering, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Medical Products Administration (NMPA) Key Laboratory for Research and Evaluation of Additive Manufacturing Medical Devices, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Innovation Platform (Center) for Industry-Education Integration of Medical Technology, Xi'an Jiaotong University, China
| | - Hui Zhu
- State Key Laboratory for Manufacturing System Engineering, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Medical Products Administration (NMPA) Key Laboratory for Research and Evaluation of Additive Manufacturing Medical Devices, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Innovation Platform (Center) for Industry-Education Integration of Medical Technology, Xi'an Jiaotong University, China
| | - Hu Cai
- Shaanxi Provincial Institute for Food and Drug Control, Xi’ an, 710065, China
| | - Dichen Li
- State Key Laboratory for Manufacturing System Engineering, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Medical Products Administration (NMPA) Key Laboratory for Research and Evaluation of Additive Manufacturing Medical Devices, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Innovation Platform (Center) for Industry-Education Integration of Medical Technology, Xi'an Jiaotong University, China
| | - Jiankang He
- State Key Laboratory for Manufacturing System Engineering, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Medical Products Administration (NMPA) Key Laboratory for Research and Evaluation of Additive Manufacturing Medical Devices, Xi'an Jiaotong University, Xi’ an, 710049, China
- National Innovation Platform (Center) for Industry-Education Integration of Medical Technology, Xi'an Jiaotong University, China
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Kapustina M, Li D, Zhu J, Wall B, Weinreb V, Cheney RE. Changes in cell surface excess are coordinated with protrusion dynamics during 3D motility. Biophys J 2023; 122:3656-3677. [PMID: 37207658 PMCID: PMC10541482 DOI: 10.1016/j.bpj.2023.04.023] [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: 09/08/2022] [Revised: 03/23/2023] [Accepted: 04/20/2023] [Indexed: 05/21/2023] Open
Abstract
To facilitate rapid changes in morphology without endangering cell integrity, each cell possesses a substantial amount of cell surface excess (CSE) that can be promptly deployed to cover cell extensions. CSE can be stored in different types of small surface projections such as filopodia, microvilli, and ridges, with rounded bleb-like projections being the most common and rapidly achieved form of storage. We demonstrate that, similar to rounded cells in 2D culture, rounded cells in 3D collagen contain large amounts of CSE and use it to cover developing protrusions. Upon retraction of a protrusion, the CSE this produces is stored over the cell body similar to the CSE produced by cell rounding. We present high-resolution imaging of F-actin and microtubules (MTs) for different cell lines in a 3D environment and demonstrate the correlated changes between CSE and protrusion dynamics. To coordinate CSE storage and release with protrusion formation and motility, we expect cells to have specific mechanisms for regulating CSE, and we hypothesize that MTs play a substantial role in this mechanism by reducing cell surface dynamics and stabilizing CSE. We also suggest that different effects of MT depolymerization on cell motility, such as inhibiting mesenchymal motility and enhancing amoeboid, can be explained by this role of MTs in CSE regulation.
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Affiliation(s)
- Maryna Kapustina
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
| | - Donna Li
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - James Zhu
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Brittany Wall
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Violetta Weinreb
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Richard E Cheney
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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Pudelko K, Wieland A, Hennecke M, Räschle M, Bastians H. Increased Microtubule Growth Triggered by Microvesicle-mediated Paracrine Signaling is Required for Melanoma Cancer Cell Invasion. CANCER RESEARCH COMMUNICATIONS 2022; 2:366-379. [PMID: 36875714 PMCID: PMC9981201 DOI: 10.1158/2767-9764.crc-22-0010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 03/25/2022] [Accepted: 05/03/2022] [Indexed: 11/16/2022]
Abstract
The acquisition of cell invasiveness is the key transition from benign melanocyte hyperplasia to aggressive melanoma. Recent work has provided an intriguing new link between the presence of supernumerary centrosomes and increased cell invasion. Moreover, supernumerary centrosomes were shown to drive non-cell-autonomous invasion of cancer cells. Although centrosomes are the principal microtubule organizing centers, the role of dynamic microtubules for non-cell-autonomous invasion remains unexplored, in particular, in melanoma. We investigated the role of supernumerary centrosomes and dynamic microtubules in melanoma cell invasion and found that highly invasive melanoma cells are characterized by the presence of supernumerary centrosomes and by increased microtubule growth rates, both of which are functionally interlinked. We demonstrate that enhanced microtubule growth is required for increased three-dimensional melanoma cell invasion. Moreover, we show that the activity to enhance microtubule growth can be transferred onto adjacent noninvasive cells through microvesicles involving HER2. Hence, our study suggests that suppressing microtubule growth, either directly using anti-microtubule drugs or through HER2 inhibitors might be therapeutically beneficial to inhibit cell invasiveness and thus, metastasis of malignant melanoma. Significance This study shows that increased microtubule growth is required for melanoma cell invasion and can be transferred onto adjacent cells in a non-cell-autonomous manner through microvesicles involving HER2.
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Affiliation(s)
- Karoline Pudelko
- Institute of Molecular Oncology, Section for Cellular Oncology, Georg-August University Göttingen, University Medical Center Göttingen (UMG) and Göttingen Center for Molecular Biosciences (GZMB), Göttingen, Germany
| | - Angela Wieland
- Department of Molecular Genetics, Technical University of Kaiserslautern, Kaiserslautern, Germany
| | - Magdalena Hennecke
- Institute of Molecular Oncology, Section for Cellular Oncology, Georg-August University Göttingen, University Medical Center Göttingen (UMG) and Göttingen Center for Molecular Biosciences (GZMB), Göttingen, Germany
| | - Markus Räschle
- Department of Molecular Genetics, Technical University of Kaiserslautern, Kaiserslautern, Germany
| | - Holger Bastians
- Institute of Molecular Oncology, Section for Cellular Oncology, Georg-August University Göttingen, University Medical Center Göttingen (UMG) and Göttingen Center for Molecular Biosciences (GZMB), Göttingen, Germany
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Chai Y, Maruko Y, Liu Z, Tagaya M. Design of oriented mesoporous silica films for guiding protein adsorption states. J Mater Chem B 2021; 9:2054-2065. [PMID: 33587739 DOI: 10.1039/d0tb02544e] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The highly-oriented cylindrical mesoporous silica films were synthesized on the rubbing-treated polyimide by adjusting the molar ratio of the orientation-directing agent (Brij56) to the structure-directing agent (P123) as surfactants in the silica precursor solutions for guiding protein adsorption states. As a result, the diameter and the orientation degree of mesopores changed with the molar ratio of Brij56 to P123. The maximum orientation degree (93%) of cylindrical mesopores oriented in the direction perpendicular to the rubbing direction was observed when the molar ratio of Brij56 to P123 was 3. Then, the dissolution features in simulated body fluid and the protein adsorption properties of the oriented cylindrical mesoporous silica films were investigated. The silica skeletons were gradually dissolved from the upper film surfaces and subsequently, the mesopore structures were collapsed when the films were immersed for 90 min. Moreover, the protein adsorption amount and the ratio from the mono-component and two-component solutions on the films were higher than those on the unoriented cylindrical mesoporous silica films due to the formation of open-ended cylindrical mesopore shapes and sizes. In addition, the shapes of the proteins adsorbed on the films had anisotropy, which would be reflected by the cylindrical mesopore shapes generated by the dissolution of silica layers and subsequent exposure of inner mesopore surfaces. Therefore, the synthesized highly-oriented cylindrical mesoporous silica films were useful to adsorb mesoscale biomolecules such as proteins and can effectively guide their anisotropic adsorption shapes, and therefore have the potential to be used as surface-coating films of polyimide in biomedical fields.
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Affiliation(s)
- Yadong Chai
- Department of Materials Science and Technology, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka, Niigata 940-2188, Japan.
| | - Yuri Maruko
- Department of Materials Science and Technology, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka, Niigata 940-2188, Japan.
| | - Zizhen Liu
- Department of Materials Science and Technology, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka, Niigata 940-2188, Japan.
| | - Motohiro Tagaya
- Department of Materials Science and Technology, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka, Niigata 940-2188, Japan.
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Chen R, Wang B, Liu Y, He J, Lin R, Li D. Gelatin-based perfusable, endothelial carotid artery model for the study of atherosclerosis. Biomed Eng Online 2019; 18:87. [PMID: 31391047 PMCID: PMC6685230 DOI: 10.1186/s12938-019-0706-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 07/29/2019] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Carotid artery geometry is important for recapitulating a pathophysiological microenvironment to study wall shear stress (WSS)-induced endothelial dysfunction in atherosclerosis. Endothelial cells (ECs) cultured with hydrogel have been shown to exhibit in vivo-like behaviours. However, to date, studies using hydrogel culture have not fully recapitulated the 3D geometry and blood flow patterns of real-life healthy or diseased carotid arteries. In this study, we developed a gelatin-patterned, endothelialized carotid artery model to study the endothelium response to WSS. RESULTS Two representative regions were selected based on the computational fluid dynamics on the TF-shaped carotid artery: Region ECA (external carotid artery) and Region CS (carotid sinus). Progressive elongation and alignment of the ECs in the flow direction were observed in Region ECA after 8, 16 and 24 h. However, the F-actin cytoskeleton remained disorganized in Region CS after 24 h. Further investigation revealed that expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) was greatly increased in Region CS relative to that in Region ECA. The physiological WSS in the carotid artery system was found to stimulate nitric oxide (NO) and prostacyclin (PGI2) release and inhibit endothelin-1 (ET-1) release after 24-h perfusion experiments. The effective permeability (E.P) of fluorescein isothiocyanate (FITC)-dextran 40 kDa in Regions ECA and CS was monitored, and it was found that the turbulence WSS value (in Region CS) was less than 0.4 Pa, and there was a significant increase in the E.P relative to that in Region ECA, in which laminar WSS value was 1.56 Pa. The tight junction protein (ZO-1) production was shown that the low WSS in Region CS induced ZO-1-level downregulation compared with that in Region ECA. CONCLUSIONS The results suggested that the gelatin-based perfusable, endothelial carotid artery model can be effective for studying the pathogenesis of atherosclerosis by which flow dynamics control the endothelium layer function in vitro.
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Affiliation(s)
- Ruomeng Chen
- State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, China
| | - Bo Wang
- Departments of Pharmacology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, China
| | - Yaxiong Liu
- State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, China
| | - Jiankang He
- State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, China
| | - Rong Lin
- Departments of Pharmacology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, China
| | - Dichen Li
- State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, China
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The Cytoskeleton of the Retinal Pigment Epithelium: from Normal Aging to Age-Related Macular Degeneration. Int J Mol Sci 2019; 20:ijms20143578. [PMID: 31336621 PMCID: PMC6678077 DOI: 10.3390/ijms20143578] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 07/15/2019] [Accepted: 07/18/2019] [Indexed: 12/15/2022] Open
Abstract
The retinal pigment epithelium (RPE) is a unique epithelium, with major roles which are essential in the visual cycle and homeostasis of the outer retina. The RPE is a monolayer of polygonal and pigmented cells strategically placed between the neuroretina and Bruch membrane, adjacent to the fenestrated capillaries of the choriocapillaris. It shows strong apical (towards photoreceptors) to basal/basolateral (towards Bruch membrane) polarization. Multiple functions are bound to a complex structure of highly organized and polarized intracellular components: the cytoskeleton. A strong connection between the intracellular cytoskeleton and extracellular matrix is indispensable to maintaining the function of the RPE and thus, the photoreceptors. Impairments of these intracellular structures and the regular architecture they maintain often result in a disrupted cytoskeleton, which can be found in many retinal diseases, including age-related macular degeneration (AMD). This review article will give an overview of current knowledge on the molecules and proteins involved in cytoskeleton formation in cells, including RPE and how the cytoskeleton is affected under stress conditions—especially in AMD.
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The Cytoskeleton-A Complex Interacting Meshwork. Cells 2019; 8:cells8040362. [PMID: 31003495 PMCID: PMC6523135 DOI: 10.3390/cells8040362] [Citation(s) in RCA: 181] [Impact Index Per Article: 36.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 04/15/2019] [Accepted: 04/15/2019] [Indexed: 12/22/2022] Open
Abstract
The cytoskeleton of animal cells is one of the most complicated and functionally versatile structures, involved in processes such as endocytosis, cell division, intra-cellular transport, motility, force transmission, reaction to external forces, adhesion and preservation, and adaptation of cell shape. These functions are mediated by three classical cytoskeletal filament types, as follows: Actin, microtubules, and intermediate filaments. The named filaments form a network that is highly structured and dynamic, responding to external and internal cues with a quick reorganization that is orchestrated on the time scale of minutes and has to be tightly regulated. Especially in brain tumors, the cytoskeleton plays an important role in spreading and migration of tumor cells. As the cytoskeletal organization and regulation is complex and many-faceted, this review aims to summarize the findings about cytoskeletal filament types, including substructures formed by them, such as lamellipodia, stress fibers, and interactions between intermediate filaments, microtubules and actin. Additionally, crucial regulatory aspects of the cytoskeletal filaments and the formed substructures are discussed and integrated into the concepts of cell motility. Even though little is known about the impact of cytoskeletal alterations on the progress of glioma, a final point discussed will be the impact of established cytoskeletal alterations in the cellular behavior and invasion of glioma.
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9
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The stellate cell system (vitamin A-storing cell system). Anat Sci Int 2017; 92:387-455. [PMID: 28299597 DOI: 10.1007/s12565-017-0395-9] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 02/15/2017] [Indexed: 01/18/2023]
Abstract
Past, present, and future research into hepatic stellate cells (HSCs, also called vitamin A-storing cells, lipocytes, interstitial cells, fat-storing cells, or Ito cells) are summarized and discussed in this review. Kupffer discovered black-stained cells in the liver using the gold chloride method and named them stellate cells (Sternzellen in German) in 1876. Wake rediscovered the cells in 1971 using the same gold chloride method and various modern histological techniques including electron microscopy. Between their discovery and rediscovery, HSCs disappeared from the research history. Their identification, the establishment of cell isolation and culture methods, and the development of cellular and molecular biological techniques promoted HSC research after their rediscovery. In mammals, HSCs exist in the space between liver parenchymal cells (PCs) or hepatocytes and liver sinusoidal endothelial cells (LSECs) of the hepatic lobule, and store 50-80% of all vitamin A in the body as retinyl ester in lipid droplets in the cytoplasm. SCs also exist in extrahepatic organs such as pancreas, lung, and kidney. Hepatic (HSCs) and extrahepatic stellate cells (EHSCs) form the stellate cell (SC) system or SC family; the main storage site of vitamin A in the body is HSCs in the liver. In pathological conditions such as liver fibrosis, HSCs lose vitamin A, and synthesize a large amount of extracellular matrix (ECM) components including collagen, proteoglycan, glycosaminoglycan, and adhesive glycoproteins. The morphology of these cells also changes from the star-shaped HSCs to that of fibroblasts or myofibroblasts.
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Abstract
ABSTRACT
Three-dimensional (3D) cell motility underlies essential processes, such as embryonic development, tissue repair and immune surveillance, and is involved in cancer progression. Although the cytoskeleton is a well-studied regulator of cell migration, most of what we know about its functions originates from studies conducted in two-dimensional (2D) cultures. This research established that the microtubule network mediates polarized trafficking and signaling that are crucial for cell shape and movement in 2D. In parallel, developments in light microscopy and 3D cell culture systems progressively allowed to investigate cytoskeletal functions in more physiologically relevant settings. Interestingly, several studies have demonstrated that microtubule involvement in cell morphogenesis and motility can differ in 2D and 3D environments. In this Commentary, we discuss these differences and their relevance for the understanding the role of microtubules in cell migration in vivo. We also provide an overview of microtubule functions that were shown to control cell shape and motility in 3D matrices and discuss how they can be investigated further by using physiologically relevant models.
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Affiliation(s)
- Benjamin P. Bouchet
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, Utrecht 3584 CH, The Netherlands
| | - Anna Akhmanova
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, Utrecht 3584 CH, The Netherlands
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11
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Bouchet BP, Noordstra I, van Amersfoort M, Katrukha EA, Ammon YC, Ter Hoeve ND, Hodgson L, Dogterom M, Derksen PWB, Akhmanova A. Mesenchymal Cell Invasion Requires Cooperative Regulation of Persistent Microtubule Growth by SLAIN2 and CLASP1. Dev Cell 2016; 39:708-723. [PMID: 27939686 DOI: 10.1016/j.devcel.2016.11.009] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 09/27/2016] [Accepted: 11/10/2016] [Indexed: 11/18/2022]
Abstract
Microtubules regulate signaling, trafficking, and cell mechanics, but the respective contribution of these functions to cell morphogenesis and migration in 3D matrices is unclear. Here, we report that the microtubule plus-end tracking protein (+TIP) SLAIN2, which suppresses catastrophes, is not required for 2D cell migration but is essential for mesenchymal cell invasion in 3D culture and in a mouse cancer model. We show that SLAIN2 inactivation does not affect Rho GTPase activity, trafficking, and focal adhesion formation. However, SLAIN2-dependent catastrophe inhibition determines microtubule resistance to compression and pseudopod elongation. Another +TIP, CLASP1, is also needed to form invasive pseudopods because it prevents catastrophes specifically at their tips. When microtubule growth persistence is reduced, inhibition of depolymerization is sufficient for pseudopod maintenance but not remodeling. We propose that catastrophe inhibition by SLAIN2 and CLASP1 supports mesenchymal cell shape in soft 3D matrices by enabling microtubules to perform a load-bearing function.
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Affiliation(s)
- Benjamin P Bouchet
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Ivar Noordstra
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Miranda van Amersfoort
- Department of Pathology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands
| | - Eugene A Katrukha
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - York-Christoph Ammon
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Natalie D Ter Hoeve
- Department of Pathology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands
| | - Louis Hodgson
- Department of Anatomy and Structural Biology, Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Marileen Dogterom
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ ,Delft, The Netherlands
| | - Patrick W B Derksen
- Department of Pathology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands
| | - Anna Akhmanova
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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Heading in the Right Direction: Understanding Cellular Orientation Responses to Complex Biophysical Environments. Cell Mol Bioeng 2015; 9:12-37. [PMID: 26900408 PMCID: PMC4746215 DOI: 10.1007/s12195-015-0422-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 10/10/2015] [Indexed: 01/09/2023] Open
Abstract
The aim of cardiovascular regeneration is to mimic the biological and mechanical functioning of tissues. For this it is crucial to recapitulate the in vivo cellular organization, which is the result of controlled cellular orientation. Cellular orientation response stems from the interaction between the cell and its complex biophysical environment. Environmental
biophysical cues are continuously detected and transduced to the nucleus through entwined mechanotransduction pathways. Next to the biochemical cascades invoked by the mechanical stimuli, the structural mechanotransduction pathway made of focal adhesions and the actin cytoskeleton can quickly transduce the biophysical signals directly to the nucleus. Observations linking cellular orientation response to biophysical cues have pointed out that the anisotropy and cyclic straining of the substrate influence cellular orientation. Yet, little is known about the mechanisms governing cellular orientation responses in case of cues applied separately and in combination. This review provides the state-of-the-art knowledge on the structural mechanotransduction pathway of adhesive cells, followed by an overview of the current understanding of cellular orientation responses to substrate anisotropy and uniaxial cyclic strain. Finally, we argue that comprehensive understanding of cellular orientation in complex biophysical environments requires systematic approaches based on the dissection of (sub)cellular responses to the individual cues composing the biophysical niche.
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Abstract
Type I collagen is a fibrillar protein, a member of a large family of collagen proteins. It is present in most body tissues, usually in combination with other collagens and other components of extracellular matrix. Its synthesis is increased in various pathological situations, in healing wounds, in fibrotic tissues and in many tumors. After extraction from collagen-rich tissues it is widely used in studies of cell behavior, especially those of fibroblasts and myofibroblasts. Cells cultured in a classical way, on planar plastic dishes, lack the third dimension that is characteristic of body tissues. Collagen I forms gel at neutral pH and may become a basis of a 3D matrix that better mimics conditions in tissue than plastic dishes.
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Affiliation(s)
- Jiří Kanta
- a Department of Medical Biochemistry; Medical Faculty in Hradec Králové; Charles University ; Prague , Czech Republic
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14
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Kamel PI, Qu X, Geiszler AM, Nagrath D, Harmancey R, Taegtmeyer H, Grande-Allen KJ. Metabolic regulation of collagen gel contraction by porcine aortic valvular interstitial cells. J R Soc Interface 2014; 11:20140852. [PMID: 25320066 PMCID: PMC4223906 DOI: 10.1098/rsif.2014.0852] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 09/22/2014] [Indexed: 12/20/2022] Open
Abstract
Despite a high incidence of calcific aortic valve disease in metabolic syndrome, there is little information about the fundamental metabolism of heart valves. Cell metabolism is a first responder to chemical and mechanical stimuli, but it is unknown how such signals employed in valve tissue engineering impact valvular interstitial cell (VIC) biology and valvular disease pathogenesis. In this study porcine aortic VICs were seeded into three-dimensional collagen gels and analysed for gel contraction, lactate production and glucose consumption in response to manipulation of metabolic substrates, including glucose, galactose, pyruvate and glutamine. Cell viability was also assessed in two-dimensional culture. We found that gel contraction was sensitive to metabolic manipulation, particularly in nutrient-depleted medium. Contraction was optimal at an intermediate glucose concentration (2 g l(-1)) with less contraction with excess (4.5 g l(-1)) or reduced glucose (1 g l(-1)). Substitution with galactose delayed contraction and decreased lactate production. In low sugar concentrations, pyruvate depletion reduced contraction. Glutamine depletion reduced cell metabolism and viability. Our results suggest that nutrient depletion and manipulation of metabolic substrates impacts the viability, metabolism and contractile behaviour of VICs. Particularly, hyperglycaemic conditions can reduce VIC interaction with and remodelling of the extracellular matrix. These results begin to link VIC metabolism and macroscopic behaviour such as cell-matrix interaction.
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Affiliation(s)
- Peter I Kamel
- Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005, USA
| | - Xin Qu
- Department of Bioengineering, Rice University, Houston, TX 77005, USA
| | - Andrew M Geiszler
- Department of Bioengineering, Rice University, Houston, TX 77005, USA
| | - Deepak Nagrath
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX 77005, USA
| | - Romain Harmancey
- Department of Internal Medicine, Division of Cardiology, The University of Texas Medical School at Houston, Houston, TX 77030, USA
| | - Heinrich Taegtmeyer
- Department of Internal Medicine, Division of Cardiology, The University of Texas Medical School at Houston, Houston, TX 77030, USA
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15
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Peters AS, Brunner G, Krieg T, Eckes B. Cyclic mechanical strain induces TGFβ1-signalling in dermal fibroblasts embedded in a 3D collagen lattice. Arch Dermatol Res 2014; 307:191-7. [PMID: 25348252 DOI: 10.1007/s00403-014-1514-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 09/30/2014] [Accepted: 10/07/2014] [Indexed: 12/01/2022]
Abstract
Many tissues are constantly exposed to mechanical stress, e.g. shear stress in vascular endothelium, compression forces in cartilage or tensile strain in the skin. Dermal fibroblasts can differentiate into contractile myofibroblasts in a process requiring the presence of TGFβ1 in addition to mechanical load. We aimed at investigating the effect of cyclic mechanical strain on dermal fibroblasts grown in a three-dimensional environment. Therefore, murine dermal fibroblasts were cultured in collagen gels and subjected to cyclic tension at a frequency of 0.1 Hz (6 cycles/min) with a maximal increase in surface area of 10 % for 24 h. This treatment resulted in a significant increase in active TGFβ1 levels, leaving the amount of total TGFβ1 unaffected. TGFβ1 activation led to pSMAD2-mediated transcriptional elevation of downstream mediators, such as CTGF, and an auto-induction of TGFβ1, respectively.
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Affiliation(s)
- Andreas S Peters
- Department of Vascular and Endovascular Surgery, University of Heidelberg, Im Neuenheimer Feld 110, 69120, Heidelberg, Germany,
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16
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Kihara T, Ito J, Miyake J. Measurement of biomolecular diffusion in extracellular matrix condensed by fibroblasts using fluorescence correlation spectroscopy. PLoS One 2013; 8:e82382. [PMID: 24312418 PMCID: PMC3842966 DOI: 10.1371/journal.pone.0082382] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Accepted: 10/30/2013] [Indexed: 11/18/2022] Open
Abstract
The extracellular matrix (ECM) comprises the heterogeneous environment outside of cells in a biological system. The ECM is dynamically organized and regulated, and many biomolecules secreted from cells diffuse throughout the ECM, regulating a variety of cellular processes. Therefore, investigation of the diffusive behaviors of biomolecules in the extracellular environment is critical. In this study, we investigated the diffusion coefficients of biomolecules of various sizes, measuring from 1 to 10 nm in radius, by fluorescence correlation spectroscopy in contracted collagen gel caused by fibroblasts, a traditional culture model of dynamic rearrangement of collagen fibers. The diffusion coefficients of the biomolecules in control collagen gel without cells decreased slightly as compared to those in solution, while the diffusion coefficients of biomolecules in the contracted gel at the cell vicinity decreased dramatically. Additionally, the diffusion coefficients of biomolecules were inversely correlated with molecular radius. In collagen gels populated with fibroblasts, the diffusion coefficient at the cell vicinity clearly decreased in the first 24 h of culture. Furthermore, molecular diffusion was greatly restricted, with a central focus on the populated cells. By using the obtained diffusion coefficients of biomolecules, we calculated the collagen fiber condensation ratio by fibroblasts in the cell vicinity at 3 days of culture to represent a 52-fold concentration. Thus, biomolecular diffusion is restricted in the vicinity of the cells where collagen fibers are highly condensed.
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Affiliation(s)
- Takanori Kihara
- Department of Life and Environment Engineering, Faculty of Environmental Engineering, The University of Kitakyushu, 1-1 Hibikino, Wakamatsu, Kitakyushu, Fukuoka, Japan
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, Japan
- * E-mail:
| | - Junri Ito
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, Japan
| | - Jun Miyake
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, Japan
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17
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McNary SM, Athanasiou KA, Reddi AH. Transforming growth factor β-induced superficial zone protein accumulation in the surface zone of articular cartilage is dependent on the cytoskeleton. Tissue Eng Part A 2013; 20:921-9. [PMID: 24116978 DOI: 10.1089/ten.tea.2013.0043] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The phenotype of articular chondrocytes is dependent on the cytoskeleton, specifically the actin microfilament architecture. Articular chondrocytes in monolayer culture undergo dedifferentiation and assume a fibroblastic phenotype. This process can be reversed by altering the actin cytoskeleton by treatment with cytochalasin. Whereas dedifferentiation has been studied on chondrocytes isolated from the whole cartilage, the effects of cytoskeletal alteration on specific zones of cells such as superficial zone chondrocytes are not known. Chondrocytes from the superficial zone secrete superficial zone protein (SZP), a lubricating proteoglycan that reduces the coefficient of friction of articular cartilage. A better understanding of this phenomenon may be useful in elucidating chondrocyte dedifferentiation in monolayer and accumulation of the cartilage lubricant SZP, with an eye toward tissue engineering functional articular cartilage. In this investigation, the effects of cytoskeletal modulation on the ability of superficial zone chondrocytes to secrete SZP were examined. Primary superficial zone chondrocytes were cultured in monolayer and treated with a combination of cytoskeleton modifying reagents and transforming growth factor β (TGFβ) 1, a critical regulator of SZP production. Whereas cytochalasin D maintains the articular chondrocyte phenotype, the hallmark of the superficial zone chondrocyte, SZP, was inhibited in the presence of TGFβ1. A decrease in TGFβ1-induced SZP accumulation was also observed when the microtubule cytoskeleton was modified using paclitaxel. These effects of actin and microtubule alteration were confirmed through the application of jasplakinolide and colchicine, respectively. As Rho GTPases regulate actin organization and microtubule polymerization, we hypothesized that the cytoskeleton is critical for TGFβ-induced SZP accumulation. TGFβ-mediated SZP accumulation was inhibited by small molecule inhibitors ML141 (Cdc42), NSC23766 (Rac1), and Y27632 (Rho effector Rho Kinase). On the other hand, lysophosphatidic acid, an upstream activator of Rho, increased SZP synthesis in response to TGFβ1. These results suggest that SZP production is dependent on the functional cytoskeleton, and Rho GTPases contribute to SZP accumulation by modulating the actions of TGFβ.
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Affiliation(s)
- Sean M McNary
- 1 Department of Orthopaedic Surgery, Lawrence Ellison Center for Tissue Regeneration and Repair, School of Medicine, University of California , Davis, Sacramento, California
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18
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Miron-Mendoza M, Koppaka V, Zhou C, Petroll WM. Techniques for assessing 3-D cell-matrix mechanical interactions in vitro and in vivo. Exp Cell Res 2013; 319:2470-80. [PMID: 23819988 PMCID: PMC3826791 DOI: 10.1016/j.yexcr.2013.06.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 06/22/2013] [Accepted: 06/24/2013] [Indexed: 12/19/2022]
Abstract
Cellular interactions with extracellular matrices (ECM) through the application of mechanical forces mediate numerous biological processes including developmental morphogenesis, wound healing and cancer metastasis. They also play a key role in the cellular repopulation and/or remodeling of engineered tissues and organs. While 2-D studies can provide important insights into many aspects of cellular mechanobiology, cells reside within 3-D ECMs in vivo, and matrix structure and dimensionality have been shown to impact cell morphology, protein organization and mechanical behavior. Global measurements of cell-induced compaction of 3-D collagen matrices can provide important insights into the regulation of overall cell contractility by various cytokines and signaling pathways. However, to understand how the mechanics of cell spreading, migration, contraction and matrix remodeling are regulated at the molecular level, these processes must also be studied in individual cells. Here we review the evolution and application of techniques for imaging and assessing local cell-matrix mechanical interactions in 3-D culture models, tissue explants and living animals.
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Affiliation(s)
- Miguel Miron-Mendoza
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Vindhya Koppaka
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Chengxin Zhou
- Graduate Program in Biomedical Engineering, University of Texas Southwestern Medical Center, Dallas, TX
| | - W. Matthew Petroll
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX
- Graduate Program in Biomedical Engineering, University of Texas Southwestern Medical Center, Dallas, TX
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19
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Caserta S, Campello S, Tomaiuolo G, Sabetta L, Guido S. A methodology to study chemotaxis in 3-D collagen gels. AIChE J 2013. [DOI: 10.1002/aic.14164] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
| | - Silvia Campello
- Dept. of Experimental Neuroscience, IRCCS Fondazione Santa Lucia; 00143; Rome; Italy
| | | | - Luigi Sabetta
- Dipartimento di Ingegneria Chimica dei Materiali e della Produzione Industriale, Università degli studi di Napoli Federico II; P.le V. Tecchio 80; 80125; Naples; Italy
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20
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Albright CD, Hay R, Jones RT, Resau JH. Discrimination of normal and transformed cells in vitro by cytologic and morphologic analysis. Cytotechnology 2012; 2:187-201. [PMID: 22358733 DOI: 10.1007/bf00133244] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/1988] [Accepted: 03/24/1989] [Indexed: 11/27/2022] Open
Abstract
Malignant A-549 lung carcinoma and adenovirus-12 SV40 hybrid virus transformed non-tumorigenic human bronchial epithelial cells (BEAS-2B) were objectively discriminated from normal bronchial epithelial (BE) cells on the basis of Papanicolaou stained nuclear features (e.g. shape, chromatin texture, hyperchromasia) and nucleolar morphology (e.g. number per cell, irregular contours). Morphometric analysis indicated that significant differences in cellular morphology existed between BE, BEAS-2B, and A-549 cells. Similar analyses of transformed, tumorigenic cell lines demonstrated that nuclear features (i.e., chromatin texture, clearing of parachromatin, hyperchromasia, variation in thickness of the nuclear envelope, sharp indentations in the nuclear envelope), and nucleolar features (i.e., degree of roundness, presence of angular projections, number per cell) discriminated chemically and virally transformed cells from spontaneously transformed cells. Nuclear and nucleolar features were correlated with the growth rate of tumorigenic cell lines. These analytical approaches will be helpful in studies of the effects of various factors (e.g. vitamin A, phorbol ester, oncogene transfection) on cellular proliferation and/or differentiation.
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Affiliation(s)
- C D Albright
- Department of Pathology, University of Maryland School of Medicine, 21201, Baltimore, Maryland, USA
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21
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Abstract
Initial efforts at biologic skin replacement strategies were mainly directed toward keratinocyte regeneration and epithelial replacement. It soon became evident that without a good dermal scaffold, the long-term efficacy of epithelial replacement was very limited. Further studies have focused on matrix replacement predominantly involving collagen frameworks with or without cellular additions. The fibroblast is central to the process of dermal regeneration and to the success of biologic matrix design. The sequence of cellular focal adhesion, integrin phosphorylated activation, intracellular and extracellular signaling, cytoskeletal activation, changes in cell morphology, and cytokine growth factor interaction are all important in influencing cell proliferation, cell spreading, neocollagenesis, and collagen translocation. A basic acellular matrix with chemical composition and correct physical structure (pore size and resistance) that takes cognizance of this sequence of matrix deposition and fibroblast functionality should be successful in promoting intrinsic healing and dermal replacement.
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22
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van Vlimmeren MAA, Driessen-Mol A, Oomens CWJ, Baaijens FPT. Passive and active contributions to generated force and retraction in heart valve tissue engineering. Biomech Model Mechanobiol 2012; 11:1015-27. [PMID: 22246054 DOI: 10.1007/s10237-011-0370-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 12/27/2011] [Indexed: 01/13/2023]
Abstract
In tissue engineered heart valves, cell-mediated stress development during culture results in leaflet retraction at time of implantation. This tissue retraction is partly active due to traction forces exerted by the cells and partly passive due to release of residual stress in the extracellular matrix and the cells. Within this study, we unraveled the passive and active contributions of cells and matrix to generated force and retraction in engineered heart valve tissues. Tissue engineered rectangular strips, fabricated from PGA/P4HB scaffolds and seeded with human myofibroblasts, were cultured for 4 weeks, after which the cellular contribution was changed at different levels. Elimination of the active cellular traction forces was achieved with Cytochalasin D and inhibition of the Rho-associated kinase pathway. Both active and passive cellular contributions were eliminated by lysation and/or decellularization of the tissue. Maximum cell activity was reached by increasing the fetal bovine serum concentration to 50%. The generated force decreased ~20% after elimination of the active cellular component, ~25% when the passive cellular component was removed as well and remained unaffected by increased serum concentrations. Passive retraction accounted for ~60% of total retraction, of which ~15% was residual stress in the matrix and ~45% was passive cell retraction. Cell traction forces accounted for the remainder ~40% of the retraction. Full activation of the cells increased retraction by ~45%. These results illustrate the importance of the cells in the process of tissue retraction, not only actively retracting the tissue, but also in a passive manner to a large extent.
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Affiliation(s)
- Marijke A A van Vlimmeren
- Department of Biomedical Engineering, WH4.12, Eindhoven University of Technology, PO Box 513, 5600 MB, Eindhoven, The Netherlands.
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23
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Foolen J, van Donkelaar CC, Ito K. Intracellular tension in periosteum/perichondrium cells regulates long bone growth. J Orthop Res 2011; 29:84-91. [PMID: 20690184 DOI: 10.1002/jor.21224] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Perichondrium/periosteum is involved in regulating long bone growth. Long bones grow faster after removal or circumferential division of periosteum. This can be countered by culturing them in conditioned medium from perichondrium/periosteum cells. Because both complete removal and circumferential division are effective, we hypothesized that perichondrium/periosteum cells require an intact environment to release the appropriate soluble factors. More specifically, we propose that this release depends on their ability to generate intracellular tension. This hypothesis was explored by modulating the ability of perichondrium/periosteum cells to generate intracellular tension and monitoring the effect thereof on long bone growth. Perichondrium/periosteum cells were cultured on substrates with different stiffness. The medium produced by these cultures was added to embryonic chick tibiotarsi from which perichondrium/periosteum was either stripped or left intact. After 3 culture days, long bone growth was proportionally related to the stiffness of the substrate on which perichondrium/periosteum cells were grown while they produced conditioned medium. A second set of experiments demonstrated that the effect occurred through expression of a growth-inhibiting factor, rather than through the reduction of a stimulatory factor. Finally, evidence for the importance of intracellular tension was obtained by showing that the inhibitory effect was abolished when perichondrium/periosteum cells were treated with cytochalasin D, which disrupts the actin microfilaments. Thus, we concluded that modulation of long bone growth occurs through release of soluble inhibitors by perichondrium/periosteum cells, and that the ability of cells to develop intracellular tension through their actin microfilaments is at the base of this mechano-regulated control pathway.
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Affiliation(s)
- Jasper Foolen
- Department of Biomedical Engineering, Eindhoven University of Technology, PO Box 513, WH 4.115, 5600 MB Eindhoven, The Netherlands
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24
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Iwashiro H, Hosoya S, Hirai K, Mima T, Ohashi S, Aihara T, Ito S, Ohara S, Adachi E. Characterization of dense artificial connective tissues generated in a newly designed bioreactor. Connect Tissue Res 2010; 52:340-52. [PMID: 21117908 DOI: 10.3109/03008207.2010.531801] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Dense connective tissues were generated simultaneously by accumulating collagen fibrils and fibroblasts on stainless steel mesh using a bioreactor system that we designed. The advantage of our system is that the artificial connective tissues can be generated within 24 hr in the absence of inhibitors against matrix metalloproteinases. The fibroblasts were suspended in 200 mL of Dulbecco's modified Eagle's medium containing 10% fetal bovine serum and 0.5 mg/mL type I collagen. The mixed solution was circulated in two types of bioreactors with cylindrical or vertical configurations to generate luminal or parenchymal tissues, respectively. The gelatin zymography showed that MMPs were first detected in the media after 8 hr from the start of circulation and reached the highest levels on day 3. Glossy white aggregates, 1-3 mm in thickness, depending on the circulation period, accumulated on mesh grids. Fibroblasts were embedded in the network of collagen fibrils and possessed oval nuclei with or without prominent cell processes to form a bipolar shape. We could not observe distended cisternae of the endoplasmic reticula, the Golgi apparatus, or exploded mitochondria, showing hypoxic degenerative alterations of fibroblasts in dense connective tissues. The artificial tissues generated by our system will be useful for biological studies and transplantation therapy.
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Affiliation(s)
- Hironobu Iwashiro
- Department of Plastic and Reconstructive Surgery, Kitasato University School of Medicine, Kanagawa, Japan
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25
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Picone R, Ren X, Ivanovitch KD, Clarke JDW, McKendry RA, Baum B. A polarised population of dynamic microtubules mediates homeostatic length control in animal cells. PLoS Biol 2010; 8:e1000542. [PMID: 21103410 PMCID: PMC2982804 DOI: 10.1371/journal.pbio.1000542] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Accepted: 10/01/2010] [Indexed: 11/18/2022] Open
Abstract
An analysis of cells grown on micro-patterned lines, and of cells during zebrafish development, identifies a population of microtubules that align along the long axis of cells to mediate homeostatic length control. Because physical form and function are intimately linked, mechanisms that maintain cell shape and size within strict limits are likely to be important for a wide variety of biological processes. However, while intrinsic controls have been found to contribute to the relatively well-defined shape of bacteria and yeast cells, the extent to which individual cells from a multicellular animal control their plastic form remains unclear. Here, using micropatterned lines to limit cell extension to one dimension, we show that cells spread to a characteristic steady-state length that is independent of cell size, pattern width, and cortical actin. Instead, homeostatic length control on lines depends on a population of dynamic microtubules that lead during cell extension, and that are aligned along the long cell axis as the result of interactions of microtubule plus ends with the lateral cell cortex. Similarly, during the development of the zebrafish neural tube, elongated neuroepithelial cells maintain a relatively well-defined length that is independent of cell size but dependent upon oriented microtubules. A simple, quantitative model of cellular extension driven by microtubules recapitulates cell elongation on lines, the steady-state distribution of microtubules, and cell length homeostasis, and predicts the effects of microtubule inhibitors on cell length. Together this experimental and theoretical analysis suggests that microtubule dynamics impose unexpected limits on cell geometry that enable cells to regulate their length. Since cells are the building blocks and architects of tissue morphogenesis, such intrinsically defined limits may be important for development and homeostasis in multicellular organisms. Because many physical processes change with scale, size control is a fundamental problem for living systems. While in some instances the size of a structure is directly determined by the dimensions of its individual constituents, many biological structures are dynamic, self-organising assemblies of relatively small component parts. How such assemblies are maintained within defined size limits remains poorly understood. Here, by confining cells to spread on lines, we show that animal cells reach a defined length that is independent of their volume and width. In searching for a “ruler” that might determine this axial limit to cell spreading, we identified a population of dynamic microtubule polymers that become oriented along the long axis of cells. This growing population of oriented microtubules drives extension of the spreading cell margin while, conversely, interactions with the cell margin promote microtubule depolymerisation, leading to cell shortening. Using a mathematical model we show that this coupling of dynamic microtubule polymerisation and depolymerisation with directed cell elongation is sufficient to explain the limit to cell spreading and cell length homeostasis. Because microtubules appear to regulate cell length in a similar way in the developing zebrafish neural tube, we suggest that this microtubule-dependent mechanism is likely to be of widespread importance for the regulation of cell and tissue geometry.
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Affiliation(s)
- Remigio Picone
- Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, University College London, London, United Kingdom
- London Centre for Nanotechnology, London, United Kingdom
- Department of Medicine, University College London, London, United Kingdom
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Xiaoyun Ren
- Medical Research Council Centre for Developmental Neurobiology, King's College London, London, United Kingdom
| | - Kenzo D. Ivanovitch
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Jon D. W. Clarke
- Medical Research Council Centre for Developmental Neurobiology, King's College London, London, United Kingdom
| | - Rachel A. McKendry
- London Centre for Nanotechnology, London, United Kingdom
- Department of Medicine, University College London, London, United Kingdom
- * E-mail: (RAM); (BB)
| | - Buzz Baum
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- * E-mail: (RAM); (BB)
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26
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Zhou J, Kim HY, Wang JHC, Davidson LA. Macroscopic stiffening of embryonic tissues via microtubules, RhoGEF and the assembly of contractile bundles of actomyosin. Development 2010; 137:2785-94. [PMID: 20630946 PMCID: PMC2910388 DOI: 10.1242/dev.045997] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/09/2010] [Indexed: 11/20/2022]
Abstract
During morphogenesis, forces generated by cells are coordinated and channeled by the viscoelastic properties of the embryo. Microtubules and F-actin are considered to be two of the most important structural elements within living cells accounting for both force production and mechanical stiffness. In this paper, we investigate the contribution of microtubules to the stiffness of converging and extending dorsal tissues in Xenopus laevis embryos using cell biological, biophysical and embryological techniques. Surprisingly, we discovered that depolymerizing microtubules stiffens embryonic tissues by three- to fourfold. We attribute tissue stiffening to Xlfc, a previously identified RhoGEF, which binds microtubules and regulates the actomyosin cytoskeleton. Combining drug treatments and Xlfc activation and knockdown lead us to the conclusion that mechanical properties of tissues such as viscoelasticity can be regulated through RhoGTPase pathways and rule out a direct contribution of microtubules to tissue stiffness in the frog embryo. We can rescue nocodazole-induced stiffening with drugs that reduce actomyosin contractility and can partially rescue morphogenetic defects that affect stiffened embryos. We support these conclusions with a multi-scale analysis of cytoskeletal dynamics, tissue-scale traction and measurements of tissue stiffness to separate the role of microtubules from RhoGEF activation. These findings suggest a re-evaluation of the effects of nocodazole and increased focus on the role of Rho family GTPases as regulators of the mechanical properties of cells and their mechanical interactions with surrounding tissues.
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Affiliation(s)
- Jian Zhou
- Department of Bioengineering, Biomedical Science Tower 3-5059, 3051 Fifth Avenue, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Hye Young Kim
- Department of Bioengineering, Biomedical Science Tower 3-5059, 3051 Fifth Avenue, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - James H.-C. Wang
- Departments of Orthopedic Surgery and Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Lance A. Davidson
- Department of Bioengineering and Developmental Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
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27
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The cytoskeletal organization of breast carcinoma and fibroblast cells inside three dimensional (3-D) isotropic silicon microstructures. Biomaterials 2010; 31:4552-61. [DOI: 10.1016/j.biomaterials.2010.02.034] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Accepted: 02/11/2010] [Indexed: 11/23/2022]
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Abstract
Dysregulated wound healing and pathologic fibrosis cause abnormal scarring, leading to poor functional and aesthetic results in hand burns. Understanding the underlying biologic mechanisms involved allows the hand surgeon to better address these issues, and suggests new avenues of research to improve patient outcomes. In this article, the authors review the biology of scar and contracture by focusing on potential causes of abnormal wound healing, including depth of injury, cytokines, cells, the immune system, and extracellular matrix, and explore therapeutic measures designed to target the various biologic causes of poor scar.
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Affiliation(s)
- Peter Kwan
- Division of Plastic and Reconstructive Surgery, Department of Surgery, 2D2.28 WMC, University of Alberta, 8440-112 Street, Edmonton, AB T6G 2B7, Canada
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29
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Pot SA, Liliensiek SJ, Myrna KE, Bentley E, Jester JV, Nealey PF, Murphy CJ. Nanoscale topography-induced modulation of fundamental cell behaviors of rabbit corneal keratocytes, fibroblasts, and myofibroblasts. Invest Ophthalmol Vis Sci 2009; 51:1373-81. [PMID: 19875665 DOI: 10.1167/iovs.09-4074] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Keratocyte-to-myofibroblast differentiation is a key factor in corneal wound healing. The purpose of this study was to determine the influence of environmental nanoscale topography on keratocyte, fibroblast, and myofibroblast cell behavior. METHODS Primary rabbit corneal keratocytes, fibroblasts, and myofibroblasts were seeded onto planar polyurethane surfaces with six patterned areas, composed of anisotropically ordered grooves and ridges with a 400-, 800-, 1200-, 1600-, 2000-, and 4000-nm pitch (pitch = groove + ridge width). After 24 hours cells were fixed, stained, imaged, and analyzed for cell shape and orientation. For migration studies, cells on each patterned surface were imaged every 10 minutes for 12 hours, and individual cell trajectories and migration rates were calculated. RESULTS Keratocytes, fibroblasts, and myofibroblasts aligned and elongated to pitch sizes larger than 1000 nm. A lower limit to the topographic feature sizes that the cells responded to was identified for all three phenotypes, with a transition zone around the 800- to 1200-nm pitch size. Fibroblasts and myofibroblasts migrated parallel to surface ridges larger than 1000 nm but lacked directional guidance on submicron and nanoscale topographic features and on planar surfaces. Keratocytes remained essentially immobile. CONCLUSIONS Corneal stromal cells elongated, aligned, and migrated, differentially guided by substratum topographic features. All cell types failed to respond to topographic features approximating the dimensions of individual stromal fibers. These findings contribute to our understanding of corneal stromal cell biology in health and disease and their interaction with biomaterials and their native extracellular matrix.
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Affiliation(s)
- Simon A Pot
- Department of Surgical Sciences, School of Veterinary Medicine, and
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30
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Transforming growth factor-beta1 stimulation enhances Dupuytren's fibroblast contraction in response to uniaxial mechanical load within a 3-dimensional collagen gel. J Hand Surg Am 2009; 34:1102-10. [PMID: 19505772 DOI: 10.1016/j.jhsa.2009.02.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2007] [Revised: 02/04/2009] [Accepted: 02/06/2009] [Indexed: 02/02/2023]
Abstract
PURPOSE A function of fibroblasts is the generation of cytomechanical force within their surrounding extracellular matrix. Abnormalities in force generation may be the cause of many pathologic conditions including scarring, and some fibroproliferative disorders such as Dupuytren's disease, which is the focus of this report. METHODS This work investigated the cytomechanical responses of Dupuytren's-derived fibroblasts to externally applied mechanical force using a culture force monitor model, with and without stimulation with the fibrosis-linked cytokine, transforming growth factor-beta1 (TGF-beta1). We compared these responses with cytomechanical responses of fibroblasts derived from the transverse carpal ligament. RESULTS Dupuytren's fibroblasts display a significantly greater ability to contract a collagen matrix compared with control fibroblasts, with a maximum generated force of 131 dynes (p < .001). These cells did not exhibit a characteristic plateau phase in the contraction, which indicates a delay in achieving tensional homeostasis from Dupuytren's-derived cells. After being subjected to uniaxial overload and underload, Dupuytren's fibroblasts responded by increased force generation, whereas control fibroblasts responded by a reduction in force in response to an overload, and contraction in response to an underload. These changes were exacerbated by the addition of the profibrotic factor TGF-beta1, with a significant increase in generated force for all cell types, in particular during the early phase of fibroblast attachment and contraction, and a positive contraction gradient in response to overloading forces. CONCLUSIONS These data suggest that cells derived from this fibrotic disease display characteristic abnormalities in force generation profiles. Their default response to loading or underloading is contraction, or increased force generation. This work highlights the role of TGF-beta1 as a mechano-transduction cytokine, which has an influence on the early phase cell of force generation, as well as a role in mechanical responses of cells to external mechanical stimuli. This, in turn, may influence the progression of Dupuytren's disease and the high rates of recurrence seen postoperatively.
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Ren R, Hutcheon AEK, Guo XQ, Saeidi N, Melotti SA, Ruberti JW, Zieske JD, Trinkaus-Randall V. Human primary corneal fibroblasts synthesize and deposit proteoglycans in long-term 3-D cultures. Dev Dyn 2008; 237:2705-15. [PMID: 18624285 DOI: 10.1002/dvdy.21606] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Our goal was to develop a 3-D multi-cellular construct using primary human corneal fibroblasts cultured on a disorganized collagen substrate in a scaffold-free environment and to use it to determine the regulation of proteoglycans over an extended period of time (11 weeks). Electron micrographs revealed multi-layered constructs with cells present in between alternating parallel and perpendicular arrays of fibrils. Type I collagen increased 2-4-fold. Stromal proteoglycans including lumican, syndecan4, decorin, biglycan, mimecan, and perlecan were expressed. The presence of glycosaminoglycan chains was demonstrated for a subset of the core proteins (lumican, biglycan, and decorin) using lyase digestion. Cuprolinic blue-stained cultures showed that sulfated proteoglycans were present throughout the construct and most prominent in its mid-region. The size of the Cuprolinic-positive filaments resembled those previously reported in a human corneal stroma. Under the current culture conditions, the cells mimic a development or nonfibrotic repair phenotype.
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Affiliation(s)
- R Ren
- Departments of Biochemistry and Ophthalmology, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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Petroll WM, Ma L. Localized application of mechanical and biochemical stimuli in 3-D culture. Dev Dyn 2008; 237:2726-36. [PMID: 18697223 DOI: 10.1002/dvdy.21629] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The goal of this study was to investigate the responses of isolated cells in 3-D culture to localized application of mechanical and biochemical signals. Corneal fibroblasts were plated inside collagen matrices for 24 hours, then imaged using time-lapse DIC. For mechanical perturbation, a microinjection needle (Femtotip) was inserted axially into the ECM, then displaced laterally to alter local ECM stress. For biochemical stimulation, PDGF or vehicle control solution was microinjected into the matrix. Compressing the ECM perpendicular to the cell axis had no appreciable effect on cell behavior. However, pushing the ECM parallel to the cell axis induced rapid cellular contraction, followed by secondary cell spreading and tractional force generation. Injection of PDGF induced a similar cell spreading response. Cells in 3-D matrices showed remarkable plasticity, and extension of pseudopodia could be induced at both the leading and trailing edges of migrating cells.
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Affiliation(s)
- W Matthew Petroll
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9057, USA.
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33
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Karamichos D, Skinner J, Brown R, Mudera V. Matrix stiffness and serum concentration effects matrix remodelling and ECM regulatory genes of human bone marrow stem cells. J Tissue Eng Regen Med 2008; 2:97-105. [PMID: 18338818 DOI: 10.1002/term.69] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The effects of mechanical stimulation of cell-seeded collagen constructs on cell orientation, intracellular signalling and molecular responses have been widely reported. In this study we investigated in vitro the contractile responses of human bone marrow stem cells (HBMSCs) to increasing collagen gel substrate stiffness and their effect on extracellular matrix (ECM) regulatory genes. Human dermal fibroblasts (HDFs) were used as controls. Cells were cultured in 10% and 20% FCS and embedded in collagen constructs at a density of 1 million cells/ml collagen. Matrix stiffness was achieved by subjecting the constructs to three different strain regimes (0%, 5% and 10%), using a computer-driven tensional culture force monitor (t-CFM) capable of uniaxial loading. The contraction forces generated by the cells were quantified over 24 h. Molecular outputs were quantified using RT-PCR. HBMSCs significantly increased force generation to increasing serum concentration (i.e 10% to 20%). 10% FCS concentration significantly reduced contraction as pre-strain stiffness was increased in HBMSCs and HDFs (0% > 5% > 10%). However, at 20% FCS HBMSCs generated similar peak force contraction at 24 h to 5% and 10% pre-strain (0% = 5% = 10%). The ECM regulatory gene for MMP2 showed upregulation at 5% pre-strain, but a 50% downregulation when pre-strain was increased to 10%. MMP9 was upregulated at 5% pre-strain and further upregulated at 10% pre-strain. In designing tissue-engineering solutions, predictable responses of cells, embedded within bio-artificial matrices, to external mechanical forces are critical. To take into account the increasing stiffness of the matrix as increasing ECM is deposited, it would be necessary to take mechanical stimulation into account to determine predictable cellular responses.
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Affiliation(s)
- Dimitris Karamichos
- University College London, Tissue Repair and Engineering Centre, Institute of Orthopaedics and Musculoskeletal Sciences, Stanmore, Middlesex, UK
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Humphrey JD. Vascular adaptation and mechanical homeostasis at tissue, cellular, and sub-cellular levels. Cell Biochem Biophys 2007; 50:53-78. [PMID: 18209957 DOI: 10.1007/s12013-007-9002-3] [Citation(s) in RCA: 262] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/22/2007] [Indexed: 12/20/2022]
Abstract
Blood vessels exhibit a remarkable ability to adapt throughout life that depends upon genetic programming and well-orchestrated biochemical processes. Findings over the past four decades demonstrate, however, that the mechanical environment experienced by these vessels similarly plays a critical role in governing their adaptive responses. This article briefly reviews, as illustrative examples, six cases of tissue level growth and remodeling, and then reviews general observations at cell-matrix, cellular, and sub-cellular levels, which collectively point to the existence of a "mechanical homeostasis" across multiple length and time scales that is mediated primarily by endothelial cells, vascular smooth muscle cells, and fibroblasts. In particular, responses to altered blood flow, blood pressure, and axial extension, disease processes such as cerebral aneurysms and vasospasm, and diverse experimental manipulations and clinical treatments suggest that arteries seek to maintain constant a preferred (homeostatic) mechanical state. Experiments on isolated microvessels, cell-seeded collagen gels, and adherent cells isolated in culture suggest that vascular cells and sub-cellular structures such as stress fibers and focal adhesions likewise seek to maintain constant a preferred mechanical state. Although much is known about mechanical homeostasis in the vasculature, there remains a pressing need for more quantitative data that will enable the formulation of an integrative mathematical theory that describes and eventually predicts vascular adaptations in response to diverse stimuli. Such a theory promises to deepen our understanding of vascular biology as well as to enable the design of improved clinical interventions and implantable medical devices.
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Affiliation(s)
- J D Humphrey
- Department of Biomedical Engineering, 337 Zachry Engineering Center, Texas A&M University, 3120 TAMU, College Station, TX 77843-3120, USA.
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Kim A, Petroll WM. Microtubule regulation of corneal fibroblast morphology and mechanical activity in 3-D culture. Exp Eye Res 2007; 85:546-56. [PMID: 17716657 PMCID: PMC2081970 DOI: 10.1016/j.exer.2007.07.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Revised: 07/06/2007] [Accepted: 07/12/2007] [Indexed: 10/23/2022]
Abstract
The purpose of this study was to investigate the role of microtubules in regulating corneal fibroblast structure and mechanical behavior using static (3-D) and dynamic (4-D) imaging of both cells and their surrounding matrix. Human corneal fibroblasts transfected to express GFP-zyxin (to label focal adhesions) or GFP-tubulin (to label microtubules) were plated at low density inside 100 microm thick type I collagen matrices. After 24h, the effects of nocodazole (to depolymerize microtubules), cytochalasin D (to disrupt f-actin), and/or Y-27632 (to block Rho-kinase) were evaluated using 3-D and 4-D imaging of both cells and ECM. After 24h of incubation, cells had well organized microtubules and prominent focal adhesions, and significant cell-induced matrix compaction was observed. Addition of nocodazole induced rapid microtubule disruption which resulted in Rho activation and additional cellular contraction. The matrix was pulled inward by retracting pseudopodial processes, and focal adhesions appeared to mediate this process. Following 24h exposure to nocodazole, there was an even greater increase in both the number of stress fibers and the amount of matrix compaction and alignment at the ends of cells. When Rho-kinase was inhibited, disruption of microtubules resulted in retraction of dendritic cell processes, and rapid formation and extension of lamellipodial processes at random locations along the cell body, eventually leading to a convoluted, disorganized cell shape. These data suggest that microtubules modulate both cellular contractility and local collagen matrix reorganization via regulation of Rho/Rho-kinase activity. In addition, microtubules appear to play a central role in dynamic regulation of cell spreading mechanics, morphology and polarity in 3-D culture.
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Affiliation(s)
- Areum Kim
- Graduate Program in Biomedical Engineering, University of Texas Southwestern Medical Center, Dallas, TX
| | - W. Matthew Petroll
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX
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Karamichos D, Brown RA, Mudera V. Complex dependence of substrate stiffness and serum concentration on cell-force generation. J Biomed Mater Res A 2006; 78:407-15. [PMID: 16715519 DOI: 10.1002/jbm.a.30814] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Collagen is a widely used biomaterial in tissue engineering. Mechanical stimulation of cell-seeded collagen constructs and its effects on cell orientation, intracellular signaling, and molecular responses have been reported. Our aim was to study the transfer of applied mechanical load to resident cells in 3D collagen constructs. Stainless steel markers were embedded in constructs as reporters of micromovement and uniaxial (0-15%) strain was applied. Cell-seeded collagen constructs were also subjected to (0-15%) uniaxial strain and material responses recorded. The viscoelastic properties of collagen resulted in comparatively small movement of the marker bars relative to gel deformation. Cell seeding density of 1 million/mL had no significant effect on the viscoelastic properties of collagen for the range of strain tested. Our findings indicate that viscoelastic properties of collagen result in minimal force transfer of applied loads as recorded by movement of stainless steel markers. At higher strain rates as collagen got stiffer the movement decreased. These findings indicate that as cell-seeded collagen constructs mature in a bioreactor and become stiffer due to ECM production/deposition, mechanical stimulation will have to be tailored over time to account for increased stiffness of constructs in vitro to elicit predictable and consistent cellular responses.
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Affiliation(s)
- D Karamichos
- UCL, Tissue Repair and Engineering Centre, Institute of Orthopaedics and Musculoskeletal Sciences, Stanmore, London, HA7 4LP, United Kingdom
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Knapp DM, Tower TT, Tranquillo RT, Barocas VH. Estimation of cell traction and migration in an isometric cell traction assay. AIChE J 2006. [DOI: 10.1002/aic.690451219] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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Lijnen P, Petrov V, Diaz-Araya G, Fagard R. Effect of bestatin on angiotensin I-, II- and III-induced collagen gel contraction in cardiac fibroblasts. J Renin Angiotensin Aldosterone Syst 2005; 5:183-8. [PMID: 15803436 DOI: 10.3317/jraas.2004.038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
OBJECTIVE The purpose of this investigation was to determine whether the aminopeptidase inhibitor with broad specificity, bestatin, affects angiotensin I (Ang I)-, angiotensin II (Ang II)- or angiotensin III (Ang III)-stimulated collagen gel contraction in cardiac fibroblasts. DESIGN AND METHODS Cardiac fibroblasts (from normal male adult rats) were cultured to confluency in Dulbeccos modified Eagles medium (DMEM) with 10% foetal bovine serum (FBS). These fibroblasts (100,000 cells) were then further incubated in a floating collagen gel lattice with the test products Ang I (1 micromol/L), Ang II (100 nmol/L), Ang III (100 nmol/L) and bestatin (100 micromol/L) for three days in DMEM without FBS. The area of the collagen gels embedded with cardiac fibroblasts was determined by a densitometric analysis. Aminopeptidase activity was estimated by spectrophotometric determination of the liberation of p-nitroaniline from alanine- or arginine-p-nitroanilide. RESULTS Ang I, II and III stimulated (p<0.05) collagen gel contraction by 30.4+/-4.8 (SEM)%, 27.1+/-3.1% and 15.4+/-3.6% respectively. Ang I- and II-induced stimulation of collagen gel contraction was of the same order but more pronounced (p<0.05) than Ang III- stimulated collagen gel contraction. The Ang I-, II- and III-stimulated collagen contraction was reduced by bestatin. Bestatin, however, did not affect basal collagen gel contraction in cardiac fibroblasts. Bestatin dose-dependently inhibited the hydrolysis of arginine- and alanine-p-nitroanilide in cardiac fibroblasts. When a neutralising antibody to transforming growth factor TGF-b1 was added to the collagen gel simultaneously with the angiotensins, the stimulated collagen contraction was not affected. Beta-aminoproprionitrile, an inhibitor of lysyl oxidase, completely abolished basal as well as Ang I-, II- and III-stimulated collagen contraction in cardiac fibroblasts. RESULTS Our data suggest that aminopeptidases are involved in the Ang I-, II- and III-induced stimulation of collagen contraction in cardiac fibroblasts.
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Affiliation(s)
- Paul Lijnen
- Hypertension Unit, Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
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Hirano S, Shelden EA, Gilmont RR. HSP27 regulates fibroblast adhesion, motility, and matrix contraction. Cell Stress Chaperones 2005; 9:29-37. [PMID: 15270075 PMCID: PMC1065303 DOI: 10.1379/471.1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Heat shock protein 27 (HSP27) modulates actin-dependent cell functions in several systems. We hypothesized that HSP27 modulates wound contraction. Stably transfected fibroblast cell lines that overexpress HSP27 (SS12) or underexpress HSP27 (AS10) were established, and cell behaviors related to wound contraction were examined. First, fibroblast-populated collagen lattice (FPCL) contraction was examined because it has been studied as a wound-healing model. In floating FPCL contraction assays, SS12 cells caused increased contraction, whereas AS10 cells caused reduced contraction. Because floating matrix contraction is thought to be mediated by the tractional force of the cells, cell behaviors related to tractional force were examined. In collagen matrix, SS12 cells elongated faster and to a greater extent and contained longer stress fibers than control cells, whereas AS10 cells were slower to elongate than control cells. SS12 cells attached to the dishes more efficiently than the control, whereas AS10 cells attached less efficiently. Migration of SS12 cells on collagen-coated dishes was also enhanced, although AS10 cells did not differ from the control cells. In summary, HSP27 regulates fibroblast adhesion, elongation, and migration and the contraction of the floating matrix in a manner dependent on the level of its expression.
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Affiliation(s)
- Sahoko Hirano
- Department of Surgery, University of Michigan Medical Center, Ann Arbor, MI 48109-0592, USA
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40
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Pizzo AM, Kokini K, Vaughn LC, Waisner BZ, Voytik-Harbin SL. Extracellular matrix (ECM) microstructural composition regulates local cell-ECM biomechanics and fundamental fibroblast behavior: a multidimensional perspective. J Appl Physiol (1985) 2004; 98:1909-21. [PMID: 15618318 DOI: 10.1152/japplphysiol.01137.2004] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The extracellular matrix (ECM) provides the principal means by which mechanical information is communicated between tissue and cellular levels of function. These mechanical signals play a central role in controlling cell fate and establishing tissue structure and function. However, little is known regarding the mechanisms by which specific structural and mechanical properties of the ECM influence its interaction with cells, especially within a tissuelike context. This lack of knowledge precludes formulation of biomimetic microenvironments for effective tissue repair and replacement. The present study determined the role of collagen fibril density in regulating local cell-ECM biomechanics and fundamental fibroblast behavior. The model system consisted of fibroblasts seeded within collagen ECMs with controlled microstructure. Confocal microscopy was used to collect multidimensional images of both ECM microstructure and specific cellular characteristics. From these images temporal changes in three-dimensional cell morphology, time- and space-dependent changes in the three-dimensional local strain state of a cell and its ECM, and spatial distribution of beta1-integrin were quantified. Results showed that fibroblasts grown within high-fibril-density ECMs had decreased length-to-height ratios, increased surface areas, and a greater number of projections. Furthermore, fibroblasts within low-fibril-density ECMs reorganized their ECM to a greater extent, and it appeared that beta1-integrin localization was related to local strain and ECM remodeling events. Finally, fibroblast proliferation was enhanced in low-fibril-density ECMs. Collectively, these results are significant because they provide new insight into how specific physical properties of a cell's ECM microenvironment contribute to tissue remodeling events in vivo and to the design and engineering of functional tissue replacements.
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Affiliation(s)
- A M Pizzo
- School of Mechanical Engineering, School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, USA
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41
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Beningo KA, Dembo M, Wang YL. Responses of fibroblasts to anchorage of dorsal extracellular matrix receptors. Proc Natl Acad Sci U S A 2004; 101:18024-9. [PMID: 15601776 PMCID: PMC539758 DOI: 10.1073/pnas.0405747102] [Citation(s) in RCA: 199] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Fibroblasts in 2D cultures differ dramatically in behavior from those in the 3D environment of a multicellular organism. However, the basis of this disparity is unknown. A key difference is the spatial arrangement of anchored extracellular matrix (ECM) receptors to the ventral surface in 2D cultures and throughout the entire surface in 3D cultures. Therefore, we asked whether changing the topography of ECM receptor anchorage alone could invoke a morphological response. By using polyacrylamide-based substrates to present anchored fibronectin or collagen on dorsal cell surfaces, we found that well spread fibroblasts in 2D cultures quickly changed into a bipolar or stellate morphology similar to fibroblasts in vivo. Cells in this environment lacked lamellipodia and large actin bundles and formed small focal adhesions only near focused sites of protrusion. These responses depend on substrate rigidity, calcium ion, and, likely, the calcium-dependent protease calpain. We suggest that fibroblasts respond to both spatial distribution and mechanical input of anchored ECM receptors. Changes in cell shape may in turn affect diverse cellular activities, including gene expression, growth, and differentiation, as shown in numerous previous studies.
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Affiliation(s)
- Karen A Beningo
- Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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42
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Petroll WM, Cavanagh HD, Jester JV. Dynamic three-dimensional visualization of collagen matrix remodeling and cytoskeletal organization in living corneal fibroblasts. SCANNING 2004; 26:1-10. [PMID: 15000286 DOI: 10.1002/sca.4950260102] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The remodeling of extracellular matrices by cells plays a defining role in developmental morphogenesis and wound healing, as well as in tissue engineering. Three-dimensional (3-D) type I collagen matrices have been used extensively as an in vitro model for studying cell-induced matrix reorganization at the macroscopic level. However, few studies have directly assessed the dynamic process of 3-D matrix remodeling at the cellular and subcellular level. We recently developed an experimental model for investigating cell-matrix mechanical interactions by plating green fluorescen protein (GFP)-zyxin transfected cells inside fibrillar collagen matrices and performing high-magnification time-lapse differential interference microscopy (DIC) and wide-field fluorescent imaging. In this study, we extend this experimental model by performing four-dimensional (4-D) reflected light and fluorescent confocal imaging (using either visible light or multiphoton excitation) of living corneal fibroblasts transfected to express GFP-zyxin or GFP-alpha-actinin, 18 h after plating inside 3-D collagen matrices. Reflected light confocal imaging allowed detailed visualization of the cells and the fibrillar collagen surrounding them. By overlaying maximum intensity projections of reflected light and GFP-zyxin or GFP-alpha-actinin images and generating stereo pair reconstructions, 3-D interactions between focal adhesions and collagen fibrils in living cells could be visualized directly. Focal adhesions were generally oriented parallel to the direction of collagen fibril alignment in front of the cell. Killing the cells induced relaxation of transient cell-induced tension on the matrix; however, significant permanent remodeling always remained. Time-lapse 3-D imaging demonstrated an active response to the Rho-kinase inhibitor Y-27632, as indicated by cell elongation, extracellular matrix relaxation, and extension of pseudopodial processes. It is interesting that, at higher cell densities, groups of collagen fibrils were compacted and aligned into straps between neighboring cells. Overall, the continued development and application of this new approach should provide important insights into the basic underlying biochemical and biomechanical regulatory mechanisms controlling matrix remodeling by corneal fibroblasts.
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Affiliation(s)
- W Matthew Petroll
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9057, USA.
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Hirano S, Shelden EA, Gilmont RR. HSP27 regulates fibroblast adhesion, motility, and matrix contraction. Cell Stress Chaperones 2004. [DOI: 10.1379/1466-1268(2004)009<0029:hrfama>2.0.co;2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Wakatsuki T, Elson EL. Reciprocal interactions between cells and extracellular matrix during remodeling of tissue constructs. Biophys Chem 2003; 100:593-605. [PMID: 12646393 DOI: 10.1016/s0301-4622(02)00308-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Cells remodel extracellular matrix during tissue development and wound healing. Similar processes occur when cells compress and stiffen collagen gels. An important task for cell biologists, biophysicists, and tissue engineers is to guide these remodeling processes to produce tissue constructs that mimic the structure and mechanical properties of natural tissues. This requires an understanding of the mechanisms by which this remodeling occurs. Quantitative measurements of the contractile force developed by cells and the extent of compression and stiffening of the matrix describe the results of the remodeling processes. Not only do forces exerted by cells influence the structure of the matrix but also external forces exerted on the matrix can modulate the structure and orientation of the cells. The mechanisms of these processes remain largely unknown, but recent studies of the regulation of myosin-dependent contractile force and of cell protrusion driven by actin polymerization provide clues about the regulation of cellular functions during remodeling.
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Affiliation(s)
- Tetsuro Wakatsuki
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Campus Box 8231, 660 South Euclid Avenue, St. Louis, MO 63110-1093, USA
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Petroll WM, Ma L. Direct, dynamic assessment of cell-matrix interactions inside fibrillar collagen lattices. CELL MOTILITY AND THE CYTOSKELETON 2003; 55:254-64. [PMID: 12845599 DOI: 10.1002/cm.10126] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cell mechanical behavior has traditionally been studied using 2-D planar elastic substrates. The goal of this study was to directly assess cell-matrix mechanical interactions inside more physiologic 3-D collagen matrices. Rabbit corneal fibroblasts transfected to express GFP-zyxin were plated at low density inside 100 micro m-thick type I collagen matrices. 3-D datasets of isolated cells were acquired at 1-3-min intervals for up to 5 h using fluorescent and Nomarski DIC imaging. Unlike cells on 2-D substrates, cells inside the collagen matrices had a bipolar morphology with thin pseudopodial processes, and without lamellipodia. The organization of the collagen fibrils surrounding each cell was clearly visualized using DIC. Using time-lapse color overlays of GFP and DIC images, displacement and/or realignment of collagen fibrils by focal adhesions could be directly visualized. During pseudopodial extension, new focal adhesions often formed in a line along collagen fibrils in front of the cell, while existing adhesions moved backward. This process generated tractional forces as indicated by the pulling in of collagen fibrils in front of the cell. Meanwhile, adhesions on both the dorsal and ventral surface of the cell body generally moved forward, resulting in contractile shortening along the pseudopodia and localized extracellular matrix (ECM) compression. Cytochalasin D induced rapid disassembly of focal adhesions, cell elongation, and ECM relaxation. This experimental model allows direct, dynamic assessment of cell-matrix interactions inside a 3-D fibrillar ECM. The data suggest that adhesions organize along actin-based contractile elements that are much less complex than the network of actin filaments that mechanically links lamellar adhesions on 2-D substrates.
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Affiliation(s)
- W Matthew Petroll
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA.
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Abstract
In 1993, a Commentary in this journal described how a simple mechanical model of cell structure based on tensegrity architecture can help to explain how cell shape, movement and cytoskeletal mechanics are controlled, as well as how cells sense and respond to mechanical forces (J. Cell Sci. 104, 613-627). The cellular tensegrity model can now be revisited and placed in context of new advances in our understanding of cell structure, biological networks and mechanoregulation that have been made over the past decade. Recent work provides strong evidence to support the use of tensegrity by cells, and mathematical formulations of the model predict many aspects of cell behavior. In addition, development of the tensegrity theory and its translation into mathematical terms are beginning to allow us to define the relationship between mechanics and biochemistry at the molecular level and to attack the larger problem of biological complexity. Part I of this two-part article covers the evidence for cellular tensegrity at the molecular level and describes how this building system may provide a structural basis for the hierarchical organization of living systems--from molecule to organism. Part II, which focuses on how these structural networks influence information processing networks, appears in the next issue.
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Affiliation(s)
- Donald E Ingber
- Department of Surgery, Children's Hospital and Harvard Medical School, Enders 1007, 300 Longwood Avenue, Boston, MA 02115, USA.
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Grinnell F, Ho CH, Tamariz E, Lee DJ, Skuta G. Dendritic fibroblasts in three-dimensional collagen matrices. Mol Biol Cell 2003; 14:384-95. [PMID: 12589041 PMCID: PMC149979 DOI: 10.1091/mbc.e02-08-0493] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Cell motility determines form and function of multicellular organisms. Most studies on fibroblast motility have been carried out using cells on the surfaces of culture dishes. In situ, however, the environment for fibroblasts is the three-dimensional extracellular matrix. In the current research, we studied the morphology and motility of human fibroblasts embedded in floating collagen matrices at a cell density below that required for global matrix remodeling (i.e., contraction). Under these conditions, cells were observed to project and retract a dendritic network of extensions. These extensions contained microtubule cores with actin concentrated at the tips resembling growth cones. Platelet-derived growth factor promoted formation of the network; lysophosphatidic acid stimulated its retraction in a Rho and Rho kinase-dependent manner. The dendritic network also supported metabolic coupling between cells. We suggest that the dendritic network provides a mechanism by which fibroblasts explore and become interconnected to each other in three-dimensional space.
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Affiliation(s)
- Frederick Grinnell
- Department of Cell Biology, University of Texas Southwestern Medical School, Dallas 75390-9039, USA.
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Tamariz E, Grinnell F. Modulation of fibroblast morphology and adhesion during collagen matrix remodeling. Mol Biol Cell 2002; 13:3915-29. [PMID: 12429835 PMCID: PMC133603 DOI: 10.1091/mbc.e02-05-0291] [Citation(s) in RCA: 193] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
When fibroblasts are placed within a three-dimensional collagen matrix, cell locomotion results in translocation of the flexible collagen fibrils of the matrix, a remodeling process that has been implicated in matrix morphogenesis during development and wound repair. In the current experiments, we studied formation and maturation of cell-matrix interactions under conditions in which we could distinguish local from global matrix remodeling. Local remodeling was measured by the movement of collagen-embedded beads towards the cells. Global remodeling was measured by matrix contraction. Our observations show that no direct relationship occurs between protrusion and retraction of cell extensions and collagen matrix remodeling. As fibroblasts globally remodel the collagen matrix, however, their overall morphology changes from dendritic to stellate/bipolar, and cell-matrix interactions mature from punctate to focal adhesion organization. The less well organized sites of cell-matrix interaction are sufficient for translocating collagen fibrils, and focal adhesions only form after a high degree of global remodeling occurs in the presence of growth factors. Rho kinase activity is required for maturation of fibroblast morphology and formation of focal adhesions but not for translocation of collagen fibrils.
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Affiliation(s)
- Elisa Tamariz
- Department of Cell Biology, University of Texas Southwestern Medical School, Dallas, Texas 75235-9039, USA
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Lijnen P, Petrov V, Rumilla K, Fagard R. Stimulation of collagen gel contraction by angiotensin II and III in cardiac fibroblasts. J Renin Angiotensin Aldosterone Syst 2002; 3:160-6. [PMID: 12563566 DOI: 10.3317/jraas.2002.036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
OBJECTIVE The aim of the present study was to investigate whether angiotensin II (Ang II), angiotensin III (Ang III) or Ang II (2-8), angiotensin IV (Ang IV) or Ang II (3-8) and Ang II (1-7), Ang II (4-8), Ang II (5-8) and Ang II (1-4) can stimulate collagen gel contraction in cardiac fibroblasts in serum-free conditions. METHODS Cardiac fibroblasts (from male adult Wistar rats) from passage 2 were cultured to confluency and added to a hydrated collagen gel in a Dulbecco's Modified Eagle's Medium, with or without foetal bovine serum, for one, two or three days. The area of the collagen gels embedded with cardiac fibroblasts was determined by a densitometric analysis. Collagen gel contraction was characterised by a decrease in the gel area. RESULTS Ang II dose-dependently stimulated the contraction of collagen mediated by cardiac fibroblasts after one, two or three days of incubation in a serum-free medium. Telmisartan completely blocked the Ang II-induced collagen contraction by cardiac fibroblasts. PD 123319 and des-Asp(1)-Ile(8)-Ang II had no effect on the Ang II-induced collagen contraction by cardiac fibroblasts. Ang III also stimulated the contraction of collagen mediated by cardiac fibroblasts after one, two or three days of incubation in a serum-free medium. des-Asp(1)-Ile(8)-Ang II and telmisartan completely blocked the Ang III-induced collagen gel contraction by cardiac fibroblasts. des-Asp(1)-Ile(8)-Ang II, however, had no effect on the Ang II-induced collagen gel contraction by cardiac fibroblasts. Ang IV and Ang II (4-8), (5-8), (1-7) and (1-4), however, had no effect on collagen gel contraction by cardiac fibroblasts. Addition of telmisartan, PD 123319 or des-Asp(1)-Ile(8)-Ang II alone did not affect collagen gel contraction by cardiac fibroblasts. CONCLUSION Our data demonstrate that the effects of Ang II on the collagen gel contraction by adult rat cardiac fibroblasts in serum-free conditions are Ang II type 1(AT(1))-receptor- mediated, because they are abolished by the specific AT(1)-receptor antagonist, telmisartan, and not by the AT(2)-receptor antagonist PD 123319 or by the Ang III antagonist des-Asp(1)-Ile(8)-angiotensin. The Ang III- stimulated contraction of collagen by cardiac fibroblasts is completely blocked by the Ang III receptor antagonist, des-Asp(1)-Ile(8)-angiotensin II, and by telmisartan.
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Affiliation(s)
- Paul Lijnen
- Department of Molecular and Cardiovascular Research, University of Leuven, Belgium.
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Abstract
Migrating cells display a characteristic polarization of the actin cytoskeleton. Actin filaments polymerise in the protruding front of the cell whereas actin filament bundles contract in the cell body, which results in retraction of the cell’s rear. The dynamic organization of the actin cytoskeleton provides the force for cell motility and is regulated by small GTPases of the Rho family, in particular Rac1, RhoA and Cdc42. Although the microtubule cytoskeleton is also polarized in a migrating cell, and microtubules are essential for the directed migration of many cell types, their role in cell motility is not well understood at a molecular level. Here, we discuss the potential molecular mechanisms for interplay of microtubules, actin and Rho GTPase signalling in cell polarization and motility. Recent evidence suggests that microtubules locally modulate the activity of Rho GTPases and, conversely, Rho GTPases might be responsible for the initial polarization of the microtubule cytoskeleton. Thus, microtubules might be part of a positive feedback mechanism that maintains the stable polarization of a directionally migrating cell.
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Affiliation(s)
- T Wittmann
- The Scripps Research Institute, Department of Cell Biology, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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