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Rappold R, Kalogeropoulos K, Auf dem Keller U, Vogel V, Slack E. Salmonella-driven intestinal edema in mice is characterized by tensed fibronectin fibers. FEBS J 2024; 291:3104-3127. [PMID: 38487972 DOI: 10.1111/febs.17120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 12/04/2023] [Accepted: 03/05/2024] [Indexed: 07/19/2024]
Abstract
Intestinal edema is a common manifestation of numerous gastrointestinal diseases and is characterized by the accumulation of fluid in the interstitial space of the intestinal wall. Technical advances in laser capture microdissection and low-biomass proteomics now allow us to specifically characterize the intestinal edema proteome. Using advanced proteomics, we identify peptides derived from antimicrobial factors with high signal intensity, but also highlight major contributions from the blood clotting system, extracellular matrix (ECM) and protease-protease inhibitor networks. The ECM is a complex fibrillar network of macromolecules that provides structural and mechanical support to the intestinal tissue. One abundant component of the ECM observed in Salmonella-driven intestinal edema is the glycoprotein fibronectin, recognized for its structure-function interplay regulated by mechanical forces. Using mechanosensitive staining of fibronectin fibers reveals that they are tensed in the edema, despite the high abundance of proteases able to cleave fibronectin. In contrast, fibronectin fibers increasingly relax in other cecal tissue areas as the infection progresses. Co-staining for fibrin(ogen) indicates the formation of a provisional matrix in the edema, similar to what is observed in response to skin injury, while collagen staining reveals a sparse and disrupted collagen fiber network. These observations plus the absence of low tensional fibronectin fibers and the additional finding of a high number of protease inhibitors in the edema proteome could indicate a critical role of stretched fibronectin fibers in maintaining tissue integrity in the severely inflamed cecum. Understanding these processes may also provide valuable functional diagnostic markers of intestinal disease progression in the future.
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Affiliation(s)
- Ronja Rappold
- Institute of Translational Medicine, ETH Zurich, Switzerland
- Institute of Food, Nutrition and Health, ETH Zurich, Switzerland
| | | | - Ulrich Auf dem Keller
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Viola Vogel
- Institute of Translational Medicine, ETH Zurich, Switzerland
- Botnar Research Center for Child Health, Basel, Switzerland
| | - Emma Slack
- Institute of Food, Nutrition and Health, ETH Zurich, Switzerland
- Botnar Research Center for Child Health, Basel, Switzerland
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2
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Trachsel B, Imobersteg S, Valpreda G, Singer G, Grabherr R, Ormos M, Burger IA, Kubik-Huch RA, Schibli R, Vogel V, Béhé M. Relaxed fibronectin: a potential novel target for imaging endometriotic lesions. EJNMMI Res 2024; 14:17. [PMID: 38340184 DOI: 10.1186/s13550-024-01070-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2023] [Accepted: 01/24/2024] [Indexed: 02/12/2024] Open
Abstract
BACKGROUND Endometriosis is characterized by the ectopic occurrence of endometrial tissue. Though considered benign, endometriotic lesions possess tumor-like properties such as tissue invasion and remodeling of the extracellular matrix. One major clinical hurdle concerning endometriosis is its diagnosis. The diagnostic modalities ultrasound and MRI are often unable to detect all lesions, and a clear correlation between imaging and clinical symptoms is still controversial. Therefore, it was our aim to identify a potential target to image active endometriotic lesions. RESULTS For our studies, we employed the preclinical radiotracer [111In]In-FnBPA5, which specifically binds to relaxed fibronectin-an extracellular matrix protein with key functions in homeostasis that has been implicated in the pathogenesis of diseases such as cancer and fibrosis. We employed this tracer in biodistribution as well as SPECT/CT studies in mice and conducted immunohistochemical stainings on mouse uterine tissue as well as on patient-derived endometriosis tissue. In biodistribution and SPECT/CT studies using the radiotracer [111In]In-FnBPA5, we found that radiotracer uptake in the myometrium varies with the estrous cycle of the mouse, leading to higher uptake of [111In]In-FnBPA5 during estrogen-dependent phases, which indicates an increased abundance of relaxed fibronectin when estrogen levels are high. Finally, immunohistochemical analysis of patient samples demonstrated that there is preferential relaxation of fibronectin in the proximity of the endometriotic stroma. CONCLUSION Estrous cycle stages characterized by high estrogen levels result in a higher abundance of relaxed fibronectin in the murine myometrium. This finding together with a first proof-of-concept study employing human endometriosis tissues suggests that relaxed fibronectin could be a potential target for the development of a diagnostic radiotracer targeting endometriotic lesions. With [111In]In-FnBPA5, the matching targeting molecule is in preclinical development.
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Affiliation(s)
- Belinda Trachsel
- Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Forschungsstrasse 111, 5232, Villigen, Switzerland
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zurich, 8093, Zurich, Switzerland
| | - Stefan Imobersteg
- Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Forschungsstrasse 111, 5232, Villigen, Switzerland
| | - Giulia Valpreda
- Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Forschungsstrasse 111, 5232, Villigen, Switzerland
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zurich, 8093, Zurich, Switzerland
| | - Gad Singer
- Kantonsspital Baden, 5404, Baden, Switzerland
| | | | - Mark Ormos
- Kantonsspital Baden, 5404, Baden, Switzerland
| | | | | | - Roger Schibli
- Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Forschungsstrasse 111, 5232, Villigen, Switzerland
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zurich, 8093, Zurich, Switzerland
| | - Viola Vogel
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zurich, 8093, Zurich, Switzerland
| | - Martin Béhé
- Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Forschungsstrasse 111, 5232, Villigen, Switzerland.
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3
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Selcuk K, Leitner A, Braun L, Le Blanc F, Pacak P, Pot S, Vogel V. Transglutaminase 2 has higher affinity for relaxed than for stretched fibronectin fibers. Matrix Biol 2024; 125:113-132. [PMID: 38135164 DOI: 10.1016/j.matbio.2023.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 11/20/2023] [Accepted: 12/18/2023] [Indexed: 12/24/2023]
Abstract
Transglutaminase 2 (TG2) plays a vital role in stabilizing extracellular matrix (ECM) proteins through enzymatic crosslinking during tissue growth, repair, and inflammation. TG2 also binds non-covalently to fibronectin (FN), an essential component of the ECM, facilitating cell adhesion, migration, proliferation, and survival. However, the interaction between TG2 and fibrillar FN remains poorly understood, as most studies have focused on soluble or surface-adsorbed FN or FN fragments, which differ in their conformations from insoluble FN fibers. Using a well-established in vitro FN fiber stretch assay, we discovered that the binding of a crosslinking enzyme to ECM fibers is mechano-regulated. TG2 binding to FN is tuned by the mechanical tension of FN fibers, whereby TG2 predominantly co-localizes to low-tension FN fibers, while fiber stretching reduces their affinity for TG2. This mechano-regulated binding relies on the proximity between the N-terminal β-sandwich and C-terminal β-barrels of TG2. Crosslinking mass spectrometry (XL-MS) revealed a novel TG2-FN synergy site within TG2's C-terminal β-barrels that interacts with FN regions located outside of the canonical gelatin binding domain, specifically FNI2 and FNIII14-15. Combining XL-MS distance restraints with molecular docking revealed the mechano-regulated binding mechanism between TG2 and modules FNI7-9 by which mechanical forces regulate TG2-FN interactions. This highlights a previously unrecognized role of TG2 as a tension sensor for FN fibers. This novel interaction mechanism has significant implications in physiology and mechanobiology, including how forces regulate cell adhesion, spreading, migration, phenotype modulation, depending on the tensional state of ECM fibers. Data are available via ProteomeXchange with identifier PXD043976.
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Affiliation(s)
- Kateryna Selcuk
- Department of Health Sciences and Technology, Institute of Translational Medicine, Laboratory of Applied Mechanobiology, ETH Zurich, Gloriastrasse 37-39 GLC G11, CH-8092 Zurich, Switzerland
| | - Alexander Leitner
- Department of Biology, Institute of Molecular Systems Biology, ETH Zurich, Otto-Stern-Weg 3, CH-8093 Zurich, Switzerland
| | - Lukas Braun
- Department of Health Sciences and Technology, Institute of Translational Medicine, Laboratory of Applied Mechanobiology, ETH Zurich, Gloriastrasse 37-39 GLC G11, CH-8092 Zurich, Switzerland
| | - Fanny Le Blanc
- Department of Biology, Institute of Molecular Systems Biology, ETH Zurich, Otto-Stern-Weg 3, CH-8093 Zurich, Switzerland
| | - Paulina Pacak
- Department of Health Sciences and Technology, Institute of Translational Medicine, Laboratory of Applied Mechanobiology, ETH Zurich, Gloriastrasse 37-39 GLC G11, CH-8092 Zurich, Switzerland
| | - Simon Pot
- Department of Health Sciences and Technology, Institute of Translational Medicine, Laboratory of Applied Mechanobiology, ETH Zurich, Gloriastrasse 37-39 GLC G11, CH-8092 Zurich, Switzerland
| | - Viola Vogel
- Department of Health Sciences and Technology, Institute of Translational Medicine, Laboratory of Applied Mechanobiology, ETH Zurich, Gloriastrasse 37-39 GLC G11, CH-8092 Zurich, Switzerland.
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4
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Wang X, Yao C, Yao X, Lin J, Li R, Huang K, Lin W, Long X, Dai C, Dong J, Yu X, Huang W, Weng W, Wang Q, Ouyang H, Cheng K. Dynamic photoelectrical regulation of ECM protein and cellular behaviors. Bioact Mater 2023; 22:168-179. [PMID: 36203959 PMCID: PMC9529514 DOI: 10.1016/j.bioactmat.2022.09.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 09/07/2022] [Accepted: 09/21/2022] [Indexed: 12/02/2022] Open
Abstract
Dynamic regulation of cell-extracellular matrix (ECM)-material interactions is crucial for various biomedical applications. In this study, a light-activated molecular switch for the modulation of cell attachment/detachment behaviors was established on monolayer graphene (Gr)/n-type Silicon substrates (Gr/Si). Initiated by light illumination at the Gr/Si interface, pre-adsorbed proteins (bovine serum albumin, ECM proteins collagen-1, and fibronectin) underwent protonation to achieve negative charge transfer to Gr films (n-doping) through π-π interactions. This n-doping process stimulated the conformational switches of ECM proteins. The structural alterations in these ECM interactors significantly reduced the specificity of the cell surface receptor-ligand interaction (e.g., integrin recognition), leading to dynamic regulation of cell adhesion and eventual cell detachment. RNA-sequencing results revealed that the detached bone marrow mesenchymal stromal cell sheets from the Gr/Si system manifested regulated immunoregulatory properties and enhanced osteogenic differentiation, implying their potential application in bone tissue regeneration. This work not only provides a fast and feasible method for controllable cells/cell sheets harvesting but also gives new insights into the understanding of cell-ECM-material communications. A light-activated molecular switch for regulation of cell attachment/detachment behaviors was established on (Gr/Si) substrates. Light-induced charge transfer from ECM protein to Gr/Si through π-π interactions, resulting in the conformational alteration of ECM proteins. Structural changes in ECM weakened the binding between RGD and integrin, inducing cell detachment. This work provides a feasible method for cell harvesting and improves the understanding of cell-ECM-material communications.
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Affiliation(s)
- Xiaozhao Wang
- Dr. Li Dak Sum & Yip Yio Chin Center for Stem Cells and Regenerative Medicine, Department of Orthopedic Surgery of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Department of Sports Medicine, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Key Laboratory of Tissue Engineering and Regenerative Medicine of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, 314400, China
- China Orthopedic Regenerative Medicine Group (CORMed), Hangzhou, 310058, China
| | - Cai Yao
- School of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | - Xudong Yao
- International Institutes of Medicine, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, No. N1, Shangcheng Avenue, Yiwu, 322000, China
| | - Junxin Lin
- Dr. Li Dak Sum & Yip Yio Chin Center for Stem Cells and Regenerative Medicine, Department of Orthopedic Surgery of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Department of Sports Medicine, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Key Laboratory of Tissue Engineering and Regenerative Medicine of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, 314400, China
- China Orthopedic Regenerative Medicine Group (CORMed), Hangzhou, 310058, China
| | - Rui Li
- Dr. Li Dak Sum & Yip Yio Chin Center for Stem Cells and Regenerative Medicine, Department of Orthopedic Surgery of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Department of Sports Medicine, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Key Laboratory of Tissue Engineering and Regenerative Medicine of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, 314400, China
- China Orthopedic Regenerative Medicine Group (CORMed), Hangzhou, 310058, China
| | - Kun Huang
- School of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou, 310027, China
| | - Weiming Lin
- School of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou, 310027, China
| | - Xiaojun Long
- Dr. Li Dak Sum & Yip Yio Chin Center for Stem Cells and Regenerative Medicine, Department of Orthopedic Surgery of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Department of Sports Medicine, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Key Laboratory of Tissue Engineering and Regenerative Medicine of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, 314400, China
- China Orthopedic Regenerative Medicine Group (CORMed), Hangzhou, 310058, China
| | - Chao Dai
- Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Key Laboratory of Tissue Engineering and Regenerative Medicine of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, 314400, China
| | - Jiajun Dong
- Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Key Laboratory of Tissue Engineering and Regenerative Medicine of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, 314400, China
| | - Xuegong Yu
- School of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou, 310027, China
| | - Wenwen Huang
- Dr. Li Dak Sum & Yip Yio Chin Center for Stem Cells and Regenerative Medicine, Department of Orthopedic Surgery of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Department of Sports Medicine, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Key Laboratory of Tissue Engineering and Regenerative Medicine of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, 314400, China
- China Orthopedic Regenerative Medicine Group (CORMed), Hangzhou, 310058, China
| | - Wenjian Weng
- School of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou, 310027, China
| | - Qi Wang
- School of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | - Hongwei Ouyang
- Dr. Li Dak Sum & Yip Yio Chin Center for Stem Cells and Regenerative Medicine, Department of Orthopedic Surgery of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Department of Sports Medicine, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Key Laboratory of Tissue Engineering and Regenerative Medicine of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, 314400, China
- China Orthopedic Regenerative Medicine Group (CORMed), Hangzhou, 310058, China
- Corresponding author. Dr. Li Dak Sum & Yip Yio Chin Center for Stem Cells and Regenerative Medicine, Department of Orthopedic Surgery of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China.
| | - Kui Cheng
- School of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou, 310027, China
- Corresponding author.
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5
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Dual MVK cleavable linkers effectively reduce renal retention of 111In-fibronectin-binding peptides. Bioorg Med Chem 2022; 73:117040. [DOI: 10.1016/j.bmc.2022.117040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 09/21/2022] [Accepted: 09/23/2022] [Indexed: 11/21/2022]
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Fonta CM, Arnoldini S, Jaramillo D, Moscaroli A, Oxenius A, Behe M, Vogel V. Fibronectin fibers are highly tensed in healthy organs in contrast to tumors and virus-infected lymph nodes. Matrix Biol Plus 2020; 8:100046. [PMID: 33543039 PMCID: PMC7852196 DOI: 10.1016/j.mbplus.2020.100046] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 07/09/2020] [Accepted: 07/09/2020] [Indexed: 12/12/2022] Open
Abstract
The extracellular matrix (ECM) acts as reservoir for a plethora of growth factors and cytokines some of which are hypothesized to be regulated by ECM fiber tension. Yet, ECM fiber tension has never been mapped in healthy versus diseased organs. Using our recently developed tension nanoprobe derived from the bacterial adhesin FnBPA5, which preferentially binds to structurally relaxed fibronectin fibers, we discovered here that fibronectin fibers are kept under high tension in selected healthy mouse organs. In contrast, tumor tissues and virus-infected lymph nodes exhibited a significantly higher content of relaxed or proteolytically cleaved fibronectin fibers. This demonstrates for the first time that the tension of ECM fibers is significantly reduced upon pathological tissue transformations. This has wide implications, as the active stretching of fibronectin fibers adjusts critical cellular niche parameters and thereby tunes the reciprocal cell-ECM crosstalk. Mapping the tensional state of fibronectin fibers opens novel and unexpected diagnostic opportunities. Mechanobiology of extracellular matrix changes upon pathological transformations. Fibronectin is significantly more relaxed in tumors than in healthy organs. Relaxed fibronectin is found close to myofibroblasts and dense collagen fibers. Viral infection reduces fibronectin fiber tension in lymph nodes. Use of a tension-sensitive adhesin to probe fibronectin fiber tension in tissues
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Key Words
- CAFs, cancer associated fibroblasts
- CLEC-2, C-type Lectin Receptor
- Cancer
- DCs, dendritic cells
- ECM, extracellular matrix
- Extracellular matrix
- FRCs, fibroblastic reticular cells
- Fibronectin
- IHC, immunohistochemistry
- IL-7, Interleukin 7
- LCMV, lymphocytic choriomeningitis virus
- Lymph node
- MMPs, matrix metalloproteinases
- Mechanobiology
- PDPN, podoplanin
- SHG, second harmonic generation
- TGF-β, Transforming Growth Factor-beta
- Virus infection
- α-SMA, alpha smooth muscle actin
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Affiliation(s)
- Charlotte M Fonta
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Simon Arnoldini
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zurich, CH-8093 Zurich, Switzerland
| | | | - Alessandra Moscaroli
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Annette Oxenius
- Institute of Microbiology, ETH Zürich, CH-8093 Zurich, Switzerland
| | - Martin Behe
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Viola Vogel
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zurich, CH-8093 Zurich, Switzerland
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Graham J, Raghunath M, Vogel V. Fibrillar fibronectin plays a key role as nucleator of collagen I polymerization during macromolecular crowding-enhanced matrix assembly. Biomater Sci 2019; 7:4519-4535. [PMID: 31436263 PMCID: PMC6810780 DOI: 10.1039/c9bm00868c] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Macromolecular crowding is used by tissue engineers to accelerate extracellular matrix assembly in vitro, however, most mechanistic studies focus on the impact of crowding on collagen fiber assembly and largely ignore the highly abundant provisional matrix protein fibronectin. We show that the accelerated collagen I assembly as induced by the neutral crowding molecule Ficoll is regulated by cell access to fibronectin. Ficoll treatment leads to significant increases in the amount of surface adherent fibronectin, which can readily be harvested by cells to speed up fibrillogenesis. FRET studies reveal that Ficoll crowding also upregulates the total amount of fibronectin fibers in a low-tension state through upregulating fibronectin assembly. Since un-stretched fibronectin fibers have more collagen binding sites to nucleate the onset of collagen fibrillogenesis, our data suggest that the Ficoll-induced upregulation of low-tension fibronectin fibers contributes to enhanced collagen assembly in crowded conditions. In contrast, chemical cross-linking of fibronectin to the glass substrate prior to cell seeding prevents early force mediated fibronectin harvesting from the substrate and suppresses upregulation of collagen I assembly in the presence of Ficoll, even though the crowded environment is known to drive enzymatic cleavage of procollagen and collagen fiber formation. To show that our findings can be exploited for tissue engineering applications, we demonstrate that the addition of supplemental fibronectin in the form of an adsorbed coating markedly improves the speed of tissue formation under crowding conditions.
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Affiliation(s)
- Jenna Graham
- Department of Health Sciences and Technology, ETH Zürich, CH-8093 Zürich, Switzerland.
| | - Michael Raghunath
- ZHAW School of Life Sciences and Facility Management, Institute for Chemistry and Biotechnology, Center for Cell Biology and Tissue Engineering, CH-8820 Wädenswil, Switzerland
| | - Viola Vogel
- Department of Health Sciences and Technology, ETH Zürich, CH-8093 Zürich, Switzerland.
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Yalak G, Shiu JY, Schoen I, Mitsi M, Vogel V. Phosphorylated fibronectin enhances cell attachment and upregulates mechanical cell functions. PLoS One 2019; 14:e0218893. [PMID: 31291285 PMCID: PMC6619657 DOI: 10.1371/journal.pone.0218893] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 06/11/2019] [Indexed: 01/29/2023] Open
Abstract
A large number of extracellular matrix proteins have been found in phosphorylated states, yet little is known about how the phosphorylation of extracellular matrix proteins might affect cell functions. We thus tested the hypothesis whether the phosphorylation of fibronectin, a major adhesion protein, affects cell behavior. Controlled in vitro phosphorylation of fibronectin by a casein kinase II (CKII) significantly upregulated cell traction forces and total strain energy generated by fibroblasts on nanopillar arrays, and consequently other elementary cell functions including cell spreading and metabolic activity. Mass spectrometry of plasma fibronectin from healthy human donors then identified a constitutively phosphorylated site in the C-terminus, and numerous other residues that became phosphorylated by the CKII kinase in vitro. Our findings open up novel strategies for translational applications including targeting diseased ECM, or to develop assays that probe the phosphorylation state of the ECM or blood as potential cancer markers.
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Affiliation(s)
- Garif Yalak
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zürich, Zurich, Switzerland
| | - Jau-Ye Shiu
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zürich, Zurich, Switzerland
| | - Ingmar Schoen
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zürich, Zurich, Switzerland
| | - Maria Mitsi
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zürich, Zurich, Switzerland
| | - Viola Vogel
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zürich, Zurich, Switzerland
- * E-mail:
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Abstract
Cells need to be anchored to extracellular matrix (ECM) to survive, yet the role of ECM in guiding developmental processes, tissue homeostasis, and aging has long been underestimated. How ECM orchestrates the deterioration of healthy to pathological tissues, including fibrosis and cancer, also remains poorly understood. Inquiring how alterations in ECM fiber tension might drive these processes is timely, as mechanobiology is a rapidly growing field, and many novel mechanisms behind the mechanical forces that can regulate protein, cell, and tissue functions have recently been deciphered. The goal of this article is to review how forces can switch protein functions, and thus cell signaling, and thereby inspire new approaches to exploit the mechanobiology of ECM in regenerative medicine as well as for diagnostic and therapeutic applications. Some of the mechanochemical switching concepts described here for ECM proteins are more general and apply to intracellular proteins as well.
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Affiliation(s)
- Viola Vogel
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department for Health Sciences and Technology, ETH Zürich, CH-8093 Zürich, Switzerland;
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10
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Ortiz Franyuti D, Mitsi M, Vogel V. Mechanical Stretching of Fibronectin Fibers Upregulates Binding of Interleukin-7. NANO LETTERS 2018; 18:15-25. [PMID: 28845674 DOI: 10.1021/acs.nanolett.7b01617] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Since evidence is rising that extracellular matrix (ECM) fibers might serve as reservoirs for growth factors and cytokines, we investigated the interaction between fibronectin (FN) and interleukin-7 (IL-7), a cytokine of immunological significance and a target of several immunotherapies. By employing a FN fiber stretch assay and Förster resonance energy transfer (FRET) confocal microscopy, we found that stretching of FN fibers increased IL-7 binding. We localized the FN binding site on the CD loop of IL-7, since a synthetic CD loop peptide also bound stronger to stretched than to relaxed FN fibers. On the basis of a structural model, we propose that the CD loop can bind to FN, while IL-7 is bound to its cognate cell surface receptors. Sequence alignment with bacterial adhesins, which also bind the FN N-terminus, suggests that a conserved motif on the CD loop (110TKSLEEN116 and the truncated 112SLEE115 in human and mouse IL-7, respectively) might bind to the second FN type I module (FnI2) and that additional epitopes enhance the stretch-upregulated binding. FN fiber stretching might thus serve as a mechano-regulated mechanism to locally concentrate IL-7 in an ECM-bound state, thereby upregulating the potency of IL-7 signaling. A feedback model mechanism is proposed that could explain the well-known, but poorly understood, function of IL-7 in ECM homeostasis. Understanding how local IL-7 availability and signaling might be modulated by the tensional state of the ECM niche, which is adjusted by residing stroma cells, is highly relevant for basic science but also for advancing IL-7 based immunotherapies.
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Affiliation(s)
- Daniela Ortiz Franyuti
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department for Health Sciences and Technology (D-HEST), ETH Zurich , Vladimir-Prelog-Weg 4, HCI F443 CH-8093 Zürich, Switzerland
| | - Maria Mitsi
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department for Health Sciences and Technology (D-HEST), ETH Zurich , Vladimir-Prelog-Weg 4, HCI F443 CH-8093 Zürich, Switzerland
| | - Viola Vogel
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department for Health Sciences and Technology (D-HEST), ETH Zurich , Vladimir-Prelog-Weg 4, HCI F443 CH-8093 Zürich, Switzerland
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Arnoldini S, Moscaroli A, Chabria M, Hilbert M, Hertig S, Schibli R, Béhé M, Vogel V. Novel peptide probes to assess the tensional state of fibronectin fibers in cancer. Nat Commun 2017; 8:1793. [PMID: 29176724 PMCID: PMC5702617 DOI: 10.1038/s41467-017-01846-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 10/19/2017] [Indexed: 01/16/2023] Open
Abstract
Transformations of extracellular matrix (ECM) accompany pathological tissue changes, yet how cell-ECM crosstalk drives these processes remains unknown as adequate tools to probe forces or mechanical strains in tissues are lacking. Here, we introduce a new nanoprobe to assess the mechanical strain of fibronectin (Fn) fibers in tissue, based on the bacterial Fn-binding peptide FnBPA5. FnBPA5 exhibits nM binding affinity to relaxed, but not stretched Fn fibers and is shown to exhibit strain-sensitive ECM binding in cell culture in a comparison with an established Fn-FRET probe. Staining of tumor tissue cryosections shows large regions of relaxed Fn fibers and injection of radiolabeled 111In-FnBPA5 in a prostate cancer mouse model reveals specific accumulation of 111In-FnBPA5 in tumor with prolonged retention compared to other organs. The herein presented approach enables to investigate how Fn fiber strain at the tissue level impacts cell signaling and pathological progression in different diseases.
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Affiliation(s)
- Simon Arnoldini
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, 8093, Zurich, Switzerland
| | - Alessandra Moscaroli
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, OIPA/103, 5232, Villigen PSI, Switzerland
| | - Mamta Chabria
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, 8093, Zurich, Switzerland
| | - Manuel Hilbert
- Laboratory of Biomolecular Research, Paul Scherrer Institute, OFLC/102, 5232, Villigen PSI, Switzerland
| | - Samuel Hertig
- Hertig Visualizations, Technikumstrasse 10B, 3400, Burgdorf, Switzerland
| | - Roger Schibli
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, OIPA/103, 5232, Villigen PSI, Switzerland.,Institute for Pharamaceutical Science, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 4, 8093, Zurich, Switzerland
| | - Martin Béhé
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, OIPA/103, 5232, Villigen PSI, Switzerland.
| | - Viola Vogel
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, 8093, Zurich, Switzerland.
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12
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Foolen J, Shiu JY, Mitsi M, Zhang Y, Chen CS, Vogel V. Full-Length Fibronectin Drives Fibroblast Accumulation at the Surface of Collagen Microtissues during Cell-Induced Tissue Morphogenesis. PLoS One 2016; 11:e0160369. [PMID: 27564551 PMCID: PMC5001707 DOI: 10.1371/journal.pone.0160369] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 07/18/2016] [Indexed: 12/03/2022] Open
Abstract
Generating and maintaining gradients of cell density and extracellular matrix (ECM) components is a prerequisite for the development of functionality of healthy tissue. Therefore, gaining insights into the drivers of spatial organization of cells and the role of ECM during tissue morphogenesis is vital. In a 3D model system of tissue morphogenesis, a fibronectin-FRET sensor recently revealed the existence of two separate fibronectin populations with different conformations in microtissues, i.e. 'compact and adsorbed to collagen' versus 'extended and fibrillar' fibronectin that does not colocalize with the collagen scaffold. Here we asked how the presence of fibronectin might drive this cell-induced tissue morphogenesis, more specifically the formation of gradients in cell density and ECM composition. Microtissues were engineered in a high-throughput model system containing rectangular microarrays of 12 posts, which constrained fibroblast-populated collagen gels, remodeled by the contractile cells into trampoline-shaped microtissues. Fibronectin's contribution during the tissue maturation process was assessed using fibronectin-knockout mouse embryonic fibroblasts (Fn-/- MEFs) and floxed equivalents (Fnf/f MEFs), in fibronectin-depleted growth medium with and without exogenously added plasma fibronectin (full-length, or various fragments). In the absence of full-length fibronectin, Fn-/- MEFs remained homogenously distributed throughout the cell-contracted collagen gels. In contrast, in the presence of full-length fibronectin, both cell types produced shell-like tissues with a predominantly cell-free compacted collagen core and a peripheral surface layer rich in cells. Single cell assays then revealed that Fn-/- MEFs applied lower total strain energy on nanopillar arrays coated with either fibronectin or vitronectin when compared to Fnf/f MEFs, but that the presence of exogenously added plasma fibronectin rescued their contractility. While collagen decoration of single fibronectin fibers enhanced the non-persistent migration of both Fnf/f and Fn-/- MEFs, the migration speed was increased for Fn-/- MEFs on plasma fibronectin fibers compared to Fnf/f MEFs. In contrast, the average speed was the same for all cells on collagen-coated Fn fibers. A Fn-FRET sensor revealed that fibronectin on average was more extended on the microtissue surface compared to fibronectin in the core. Gradients of collagen-to-fibronectin ratios and of the fraction of collagen-adsorbed to stretched fibrillar fibronectin conformations might thereby provide critical cell migration cues. This study highlights a dominant role for fibronectin in tissue morphogenesis and the development of tissue heterogeneities.
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Affiliation(s)
- Jasper Foolen
- Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, Zurich, Switzerland
| | - Jau-Ye Shiu
- Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, Zurich, Switzerland
| | - Maria Mitsi
- Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, Zurich, Switzerland
| | - Yang Zhang
- Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, Zurich, Switzerland
| | - Christopher S. Chen
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, Massachusetts, United States of America
| | - Viola Vogel
- Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zurich, Vladimir-Prelog-Weg 4, Zurich, Switzerland
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13
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Abstract
Molecular dynamics (MD) simulations have become a powerful and popular method for the study of protein allostery, the widespread phenomenon in which a stimulus at one site on a protein influences the properties of another site on the protein. By capturing the motions of a protein's constituent atoms, simulations can enable the discovery of allosteric binding sites and the determination of the mechanistic basis for allostery. These results can provide a foundation for applications including rational drug design and protein engineering. Here, we provide an introduction to the investigation of protein allostery using molecular dynamics simulation. We emphasize the importance of designing simulations that include appropriate perturbations to the molecular system, such as the addition or removal of ligands or the application of mechanical force. We also demonstrate how the bidirectional nature of allostery-the fact that the two sites involved influence one another in a symmetrical manner-can facilitate such investigations. Through a series of case studies, we illustrate how these concepts have been used to reveal the structural basis for allostery in several proteins and protein complexes of biological and pharmaceutical interest.
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14
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Ariga K, Li J, Fei J, Ji Q, Hill JP. Nanoarchitectonics for Dynamic Functional Materials from Atomic-/Molecular-Level Manipulation to Macroscopic Action. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:1251-86. [PMID: 26436552 DOI: 10.1002/adma.201502545] [Citation(s) in RCA: 291] [Impact Index Per Article: 36.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 07/27/2015] [Indexed: 05/21/2023]
Abstract
Objects in all dimensions are subject to translational dynamism and dynamic mutual interactions, and the ability to exert control over these events is one of the keys to the synthesis of functional materials. For the development of materials with truly dynamic functionalities, a paradigm shift from "nanotechnology" to "nanoarchitectonics" is proposed, with the aim of design and preparation of functional materials through dynamic harmonization of atomic-/molecular-level manipulation and control, chemical nanofabrication, self-organization, and field-controlled organization. Here, various examples of dynamic functional materials are presented from the atom/molecular-level to macroscopic dimensions. These systems, including atomic switches, molecular machines, molecular shuttles, motional crystals, metal-organic frameworks, layered assemblies, gels, supramolecular assemblies of biomaterials, DNA origami, hollow silica capsules, and mesoporous materials, are described according to their various dynamic functions, which include short-term plasticity, long-term potentiation, molecular manipulation, switchable catalysis, self-healing properties, supramolecular chirality, morphological control, drug storage and release, light-harvesting, mechanochemical transduction, molecular tuning molecular recognition, hand-operated nanotechnology.
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Affiliation(s)
- Katsuhiko Ariga
- World Premier International (WPI) Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Junbai Li
- Beijing National Laboratory for Molecular Science, CAS Key Lab of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Science, Beijing, 100190, P. R. China
| | - Jinbo Fei
- Beijing National Laboratory for Molecular Science, CAS Key Lab of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Science, Beijing, 100190, P. R. China
| | - Qingmin Ji
- World Premier International (WPI) Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Jonathan P Hill
- World Premier International (WPI) Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, 305-0044, Japan
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15
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Kubow KE, Vukmirovic R, Zhe L, Klotzsch E, Smith ML, Gourdon D, Luna S, Vogel V. Mechanical forces regulate the interactions of fibronectin and collagen I in extracellular matrix. Nat Commun 2015; 6:8026. [PMID: 26272817 PMCID: PMC4539566 DOI: 10.1038/ncomms9026] [Citation(s) in RCA: 213] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 07/09/2015] [Indexed: 12/11/2022] Open
Abstract
Despite the crucial role of extracellular matrix (ECM) in directing cell fate in healthy and diseased tissues--particularly in development, wound healing, tissue regeneration and cancer--the mechanisms that direct the assembly and regulate hierarchical architectures of ECM are poorly understood. Collagen I matrix assembly in vivo requires active fibronectin (Fn) fibrillogenesis by cells. Here we exploit Fn-FRET probes as mechanical strain sensors and demonstrate that collagen I fibres preferentially co-localize with more-relaxed Fn fibrils in the ECM of fibroblasts in cell culture. Fibre stretch-assay studies reveal that collagen I's Fn-binding domain is responsible for the mechano-regulated interaction. Furthermore, we show that Fn-collagen interactions are reciprocal: relaxed Fn fibrils act as multivalent templates for collagen assembly, but once assembled, collagen fibres shield Fn fibres from being stretched by cellular traction forces. Thus, in addition to the well-recognized, force-regulated, cell-matrix interactions, forces also tune the interactions between different structural ECM components.
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Affiliation(s)
- Kristopher E. Kubow
- Department of Biology, James Madison University, Harrisonburg, Virginia 22807, USA
- Department of Health Sciences and Technology, ETH Zurich, CH-8093 Zürich, Switzerland
| | - Radmila Vukmirovic
- Department of Health Sciences and Technology, ETH Zurich, CH-8093 Zürich, Switzerland
| | - Lin Zhe
- Department of Health Sciences and Technology, ETH Zurich, CH-8093 Zürich, Switzerland
| | - Enrico Klotzsch
- Department of Health Sciences and Technology, ETH Zurich, CH-8093 Zürich, Switzerland
- Centre for Vascular Research, ARC Centre of Excellence in Advanced Molecular Imaging and Australian Centre for Nanomedicine, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Michael L. Smith
- Department of Health Sciences and Technology, ETH Zurich, CH-8093 Zürich, Switzerland
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215, USA
| | - Delphine Gourdon
- Department of Health Sciences and Technology, ETH Zurich, CH-8093 Zürich, Switzerland
- Department of Material Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Sheila Luna
- Department of Health Sciences and Technology, ETH Zurich, CH-8093 Zürich, Switzerland
| | - Viola Vogel
- Department of Health Sciences and Technology, ETH Zurich, CH-8093 Zürich, Switzerland
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16
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Bradshaw MJ, Smith ML. Multiscale relationships between fibronectin structure and functional properties. Acta Biomater 2014; 10:1524-31. [PMID: 23978411 DOI: 10.1016/j.actbio.2013.08.027] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 07/24/2013] [Accepted: 08/14/2013] [Indexed: 12/11/2022]
Abstract
Cell behavior is tightly coupled to the properties of the extracellular matrix (ECM) to which they attach. Fibronectin (Fn) forms a supermolecular, fibrillar component of the ECM that is prominent during development, wound healing and the progression of numerous diseases. This indicates that Fn has an important function in controlling cell behavior during dynamic events in vivo. The multiscale architecture of Fn molecules assembled into these fibers determines the ligand density of cell adhesion sites on the surface of the Fn fiber, Fn fiber porosity for cell signaling molecules such as growth factors, the mechanical stiffness of the Fn matrix and the adhesivity of Fn for its numerous soluble ligands. These parameters are altered by mechanical strain applied to the ECM. Recent efforts have attempted to link the molecular properties of Fn with bulk properties of Fn matrix fibers. Studies of isolated Fn fibers have helped to characterize the fiber's material properties and, in combination with models of Fn molecular behavior in the fibers, have begun to provide insights into the Fn molecular arrangement and intermolecular adhesions within the fibers. A review of these studies allows the development of an understanding of the mechanobiological functions of Fn.
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Affiliation(s)
- M J Bradshaw
- Department of Mechanical Engineering, Boston University, 44 Cummington St., ERB 502, Boston, MA 02215, USA
| | - M L Smith
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA.
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17
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Klotzsch E, Schoen I, Ries J, Renn A, Sandoghdar V, Vogel V. Conformational distribution of surface-adsorbed fibronectin molecules explored by single molecule localization microscopy. Biomater Sci 2014; 2:883-892. [DOI: 10.1039/c3bm60262a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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18
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Heparin-dependent regulation of fibronectin matrix conformation. Matrix Biol 2013; 34:124-31. [PMID: 24148804 DOI: 10.1016/j.matbio.2013.10.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Revised: 09/30/2013] [Accepted: 10/01/2013] [Indexed: 12/26/2022]
Abstract
Extracellular matrix (ECM) conformation is regulated by a variety of stimuli in vivo, including mechanical forces and allosteric binding partners, and these conformational changes contribute to the regulation of cell behavior. Heparin and heparan sulfate, for example, have been shown to regulate the sequestration and presentation of numerous growth factors, including vascular endothelial growth factor, on the heparin 2 binding domain in fibronectin (Fn). However, mechanical force also alters Fn conformation, indicating that the growth factor binding region may be co-regulated by both heparin and mechanical force. Herein, we describe a simple antibody-based method for evaluating the conformation of the heparin 2 binding domain in Fn, and use it to determine the relative contributions of heparin and mechanical strain to the regulation of Fn conformation. We achieved specificity in quantifying conformational changes in this region of Fn by measuring the ratio of two fluorescent monoclonal antibodies, one that is insensitive to Fn conformational changes and a second whose binding is reduced or enhanced by non-equilibrium conformational changes. Importantly, this technique is shown to work on Fn adsorbed on surfaces, single Fn fibers, and Fn matrix fibers in cell culture. Using our dual antibody approach, we show that heparin and mechanical strain co-regulate Fn conformation in matrix fibrils, which is the first demonstration of heparin-dependent regulation of Fn in its physiologically-relevant fibrillar state. Furthermore, the dual antibody approach utilizes commercially available antibodies and simple immunohistochemistry, thus making it accessible to a wide range of scientists interested in Fn mechanobiology.
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