Integrin α1β1 participates in Chondrocyte Transduction of Osmotic Stress

Abstract

Purpose: To determine the role of the collagen binding receptor integrin α1β1 in regulating chondrocyte osmotransduction. Methods: The [Ca2+]i transient response of wildtype and integrin α1-null chondrocytes to osmotic stress was measured ex vivo and in vitro using real-time confocal microscopy. Immunocytochemistry was performed to detect the presence of the osmosensor, transient receptor potential vanilloid 4 (TRPV4), and the agonist GSK1016790A (GSK101) was used to test for its functionality. Results: Deletion of the integrin α1 subunit inhibited the ability of chondrocytes to respond to a hypo-osmotic stress ex vivo and in vitro. TRPV4 protein was expressed by both wildtype and integrin α1-null chondrocytes, however TRPV4 could only be activated on wildtype chondrocytes. Conclusion: Integrin α1β1 is a key participant in chondrocyte transduction of a hypo-osmotic stress. Furthermore, the mechanism by which integrin α1β1 influences osmotransduction is independent of matrix binding, but likely dependent on the chondrocyte osmosensor TRPV4.