SEMA4A and rheumatoid arthritis: The invasive ability of RA synovial fibroblasts (RASF) was potentiated by recombinant human Sema4A (rhSema4A) and blocked with Sema4A small interfering RNA (siRNA), thus showing a pro-invasion activity of Sema4A, which induces MMP-3 and MMP-9 expression.