PECAM1 and rheumatoid arthritis: Since VEGF-induced angiogenesis has been reported to play an important role in the progression of RA, a type of inflammatory arthritis, we investigated VEGF and CD31 (a marker of angiogenesis) expression in human synovial membrane samples collected from de-identified age-matched (40–60 years) healthy human subjects (3 females and 3 males) who had undergone amputation due to injury and RA patients (3 females and 3 males) who underwent joint replacement surgery.