Procyanidin B3(B3) is a procyanidin dimer that is widely studied due to its high abundance in the human diet and antioxidant activity.

We observed that Procyanidin B3 inhibited H(2)O(2)-induced apoptosis in primary chondrocytes, suppressed H(2)O(2)- or IL-1?-induced nitric oxide synthase (iNOS) production, and prevented IL-1?-induced suppression of chondrocyte differentiation marker gene expression in primary chondrocytes. Moreover, Procyanidin B3 treatment enhanced the early differentiation of ATDC5 cells. To examine whether Procyanidin B3 prevents cartilage destruction in vivo, OA was surgically induced in C57BL/6J mice followed by oral administration of Procyanidin B3 or vehicle control. Daily oral Procyanidin B3 administration protected articular cartilage from OA and prevented chondrocyte apoptosis in surgically-induced OA joints. Furthermore, Procyanidin B3 administration prevented heterotopic cartilage formation near the surgical region. iNOS protein expression was enhanced in the synovial tissues and the pseudocapsule around the surgical region in OA mice fed a control diet, but was reduced in mice that received Procyanidin B3. Together, these data indicated that in the OA model, Procyanidin B3 prevented OA progression and heterotopic cartilage formation, at least in a part through the suppression of iNOS.