Involvement of α5β1 Integrin in Matrix Interactions and Proliferation of Chondrocytes

Abstract

Integrins are cell surface receptors involved in cellular processes including adhesion, migration, and matrix assembly. In the present study, we analyzed the possible involvement of ␣5␤1 integrin in the regulation of chondrocyte adhesion, spreading, and proliferation. We found that rabbit growth plate chondrocytes were able to attach to substrates coated with type I collagen, type II collagen, or fibronectin within 24 h of culture. During this time period, attachment to fibronectin appeared to be dependent on ␣5␤1 integrin, whereas adhesion to collagens was not. By day 3 of culture, chondrocytes spread onto all the substrates tested. We found that regardless of the nature of the substrate, cell spreading was reversed by treatment with RGD peptide or antibodies against ␣5␤1 or fibronectin, indicating that cell spreading involved ␣5␤1 and fibronectin endogenously produced and deposited by the chondrocytes themselves. Colony formation by chondrocytes in soft agar was inhibited by treatment with RGD peptides or BIIG2, an antibody that interferes with ␣5␤1 integrin-ligand interactions. Furthermore, DNA content was decreased by treatment with anti-fibronectin antibody in micromass culture of chondrocytes. Immunohistochemical analysis on tissue sections revealed that the ␣5 subunit was particularly abundant in the proliferative and hypertrophic zones of growth plate. The results of the study indicate that ␣5␤1 integrin plays multiple roles in chondrocyte behavior and function and appears to be involved in the regulation of both chondrocyte-matrix interactions and

αvβ5 Integrin promotes dedifferentiation of monolayer-cultured articular chondrocytes

“…Among the integrins expressed on chondrocytes, ␣5␤1 integrin is the one most studied to date. Previous studies have shown that this integrin regulates various aspects of chondrocyte biology (21)(22)(23)(24)(25). However, the involvement of this integrin in dedifferentiation was not supported by the results of the present study.…”

“…Chondrocytes express several types of integrins (17)(18)(19)(20), which are known to regulate various aspects of cell behavior. In addition to cell attachment, integrins on the chondrocytes are involved in proliferation, survival, differentiation, matrix remodeling, and response to mechanical stimuli (21)(22)(23)(24)(25). Integrins are also believed to play a role in the dedifferentiation of chondrocytes, but their involvement in the process has not yet been demonstrated.…”

A new peptide-based urethane polymer: synthesis, biodegradation, and potential to support cell growth in vitro

“…9A). Whether the cells attach to the polymer through binding to lysine groups, or through fibronectin synthesized by cells for attachment is as yet not clear [23]. Continuous culture of BMSC on polymers for 7 days showed that BMSC retained their morphology similar to the cells grown on tissue culture polystyrene (TCPS; data not shown).…”

“…Collagen type I is hydroxyproline-rich protein secreted in significant concentrations by BMSC cells [23,24]. Since collagen type I contains 10-15% hydroxyproline and it is the major protein synthesized by BMSC, we measured hydroxyproline contents in the culture supernatents to compare collagen synthesis in BMSC cultured on LDI-glycerol polymer or on the TCPS.…”

Functional Genomic Analysis in Arthritis-Affected Cartilage: Yin-Yang Regulation of Inflammatory Mediators by α5β1 and αVβ3 Integrins

“…These ECM proteins may alter chondrocyte functions; FN and FN fragments have been reported to induce IL-1␤, IL-6, GM-CSF, matrix metalloproteinases (MMPs), and proteoglycan release in chondrocytes (5,6). Engagement of ␣ 5 ␤ 1 integrin by FN has also been implicated in chondrocyte adhesion, spreading, and proliferation in vitro (7,8).…”