COL2A1 and synovitis: Notably, 50% Lr-PRG supernatant exhibited a trend to counteract the COL2A1 downregulation (catabolic) effect of LPS in this in vitro system of synovitis, which could indicate that PRP (particularly Lr-PRP) preparations could be useful to induce chondrogenic differentiation of stem cells from synovial membrane in patients with OA [24, 25].