Mechanistic Insight on the Interaction between OPN and Integrin ανβ3 in Osteoarthritis

Figure 4

Effect of overexpression and knockdown of OPN. (a, b) rhOPN-mediated overexpression of OPN increased the protein levels of integrin ανβ3 and HAS1 in OA chondrocytes. Depleting chondrocytes of OPN decreased the protein levels of integrin ανβ3 and HAS1 in OA chondrocytes. Treating OPN-overexpressing OA chondrocytes with GRGDSP significantly reduced the protein levels of integrin ανβ3 and HAS1. However, using the antibody specific for integrin ανβ3 in OPN-overexpressing OA chondrocytes downregulated integrin ανβ3 and HAS1. (c, d) From the mRNA level, the expression of integrin ανβ3 was downregulated in the rhOPN group and upregulated in the si-OPN group. The mRNA levels of HAS1, HAS2, and HAS3 positively correlated with the expression of OPN. The mRNA levels of HAS1, HAS2, HAS3, and integrin ανβ3 decreased upon blocking the binding between OPN and integrin receptor. (e, f) Toluidine blue staining showed that the content of glycosaminoglycan increased in rhOPN group, but decreased significantly in si-OPN, GRGDSP+rhOPN, and integrin ανβ3+rhOPN groups. (g) Enzyme-linked immunosorbent assay showed that the OA chondrocytes secreted HA commensurate with the changes in HAS expression. , , .

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