Signal regulatory proteins (SIRP) belong to immunoglobulin super family (IgSF) and relate to integrin signaling cascades. It has been shown that SIRPa is expressed in a variety of cells including myeloid cells and neurons. In the present study the expression of this IgSF member in articular chondrocytes was investigated. Methods: Using a panel of anti-SIRPalpha antibodies, immunohistochemistry, Western-blotting and methods, expression of SIRP electrophysiologya and its role in chondrocyte mechano-transduction were assessed. Results: No identifiable positive signal was obtained by using immunohistochemistry methods on frozen and paraffin sections. SIRPa is expressed by both normal and osteoarthritis cultured chondrocytes. The electrophysiological response of chondrocytes in the presence of SE7C2 mAb was significantly inhibited whereas SE5A5 did not show any modification in this response. Conclusions: It seems likely that SIRPa could be associated with other proteins such as integrins, CD47 and ion channels, which contribute to the electrophysiological response of human articular chondrocytes. In any case, this study has provided a specific functional role for SIRPalpha in chondrocyte mechano-transduction.

Keywords: Cartilage, Chondrocyte, Osteoarthritis (OA), Signal regulatory proteins (SIRP)

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