Integrin‐mediated adhesion of human articular chondrocytes to cartilage

Abstract

Objective. To determine 1) the kinetics and strength of adhesion of human articular chondrocytes to a cut cartilage surface, and 2) the role of specific integrins in mediating such adhesion, using an in vitro model.Methods. Human articular chondrocytes isolated from cadaveric donors (mean ؎ SD age 38 ؎ 13 years) were cultured in high-density or low-density monolayer. Following release from culture with trypsin and a 2-2.5-hour recovery period, chondrocytes were analyzed either for adhesion to cartilage or for integrin expression by flow cytometry.Results. Following culture in monolayer, adhesion of chondrocytes to cartilage increased with time, from 6-16% at 10 minutes to a maximum of 59-82% at 80-320 minutes. After 80 minutes of adhesion, the resistance of cells to flow-induced shear stress (50% detachment) was ϳ21 Pa. Chondrocyte adhesion to cartilage decreased with pretreatment of cells with monoclonal antibodies that bound to and blocked certain integrins. After an 80-minute incubation time, adhesion of chondrocytes cultured in high-density monolayer decreased from the value of IgG1-treated controls (55%) with blocking of the ␤1 integrin subunit (to 23%) or with blocking of ␣5␤1 (to 36%). Following expansion of chondrocytes in low-density monolayer, the mechanisms of adhesion to cartilage were generally similar. After an 80-minute incubation time, adhesion of chondrocytes cultured in low-density monolayer decreased from the value of IgG1-treated controls (62%) with blocking of the ␤1 integrin subunit (to 30%) or with blocking of ␣5␤1 (to 44%). Additionally, adhesion of these cells decreased to 46% by blocking of ␣v␤5, with a similar trend in effect for chondrocytes cultured in high-density monolayer. Blocking of the ␣1 or ␣3 integrin subunits or ␣v␤3 had no detectable effect on adhesion, even though these receptors were detected by flow cytometry.Conclusion. Under the culture and seeding conditions studied, ␤1, ␣5␤1, and ␣v␤5 integrins mediate human chondrocyte adhesion to cartilage. These chondrocyte integrins have a potential role in the initial adhesion and retention of chondrocytes at a cartilage defect site following clinical procedures of chondrocyte transplantation.

αvβ5 Integrin promotes dedifferentiation of monolayer-cultured articular chondrocytes

“…Nonetheless, ␣v␤5 integrin could be another important integrin in chondrocytes. The results of previous studies, along with the findings of the present study, consistently indicate that ␣v␤5 integrin is abundantly expressed on articular chondrocytes (19,20) and that ␣v␤5 integrin mediates chondrocyte attachment to various matrices (45,46). Therefore, it would not be surprising to find that ␣v␤5 integrin is involved in the metabolic and morphologic changes that occur in monolayer-cultured chondrocytes after plating.…”

“…The activity of R-Ras increased noticeably during culture, which likely caused the increase in cell attachment via the activation of ␣v␤5 integrin. An increase in chondrocyte attachment by culture has been demonstrated previously (45,52), but the mechanism(s) of the increase have not yet been determined. This is the first study to show that the elevation of R-Ras activity might account for that phenomenon.…”

Synthesis of proteoglycan 4 by chondrocyte subpopulations in cartilage explants, monolayer cultures, and resurfaced cartilage cultures

“…Isolated chondrocytes were also seeded onto a cartilage substrate and cultured to form an in vitro transplant model similar to that previously described (30,31,35). Briefly, individual cartilage sections were secured between a polysulfone tube and an annular base, creating a well, with cartilage forming the bottom surface.…”

Cellular and Acellular Approaches for Cartilage Repair

“…After 80 minutes of adhesion, the resistance of cells to flow-induced shear stress (50% detachment) was approximately 21 Pa. 38 It was also shown that under the culture and seeding conditions studied, β1, α5β1, and αVβ5 integrins mediate human chondrocyte adhesion to cartilage. 38 It is not known if adhesion on other surfaces such as from scaffolds involves other integrins.…”