Hyperpolarisation of cultured human chondrocytes following cyclical pressure‐induced strain: Evidence of a role for α5β1 integrin as a chondrocyte mechanoreceptor

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Abstract
Mechanical stimuli influence chondrocyte metabolism, inducing changes in intracellular cyclic adenosine monophosphate and proteoglycan production. We have previously demonstrated that primary monolaycr cultures of human chondrocyles have an electropysiological response after intermittent pressure-induced strain characterised by a membrane hyperpolarisation of approximately 40%. The mechanisms responsible for these changes are not fully understood but potentially involve signalling molecules such as integrins that link extracellular matrix with cytoplasmic components. The results reported in this paper demonstrate that the transduction pathways involved in the hyperpolarisation response of human articular chondrocytes in vitro after cyclical pressure-induced strain involve α5β1 integrin. We have demonstrated, using pharmacological inhibitors of a variety of intracellular signalling pathways, that the actin cytoskeleton, the phospholipase C calmodulin pathway, and both tyrosine protein kinase and protein kinase C activities are important in the transduction of the electrophysiological response. These results suggest that α5β1 is an important chondrocyte mechanoreceptor and a potential regulator of chondrocyte function.