CCN4 induces vascular cell adhesion molecule-1 expression in human synovial fibroblasts and promotes monocyte adhesion

► CCN4 was highly expressed in OA synovial fibroblasts as compared to normal SFs. ► CCN4 induces the monocyte adhesion in OASFs by up-regulation of VCAM-1 expression. ► CCN4 acts through the αvβ5/α6β1 integrin, Syk, PKCδ, and JNK pathways to induce VCAM-1. ► AP-1 is key transcription factor of CCN4-induced VCAM-1 expression.