WISP-1 represses chondrogenic differentiation of ATDC5 cells. A: Western blot of WISP-1 produced by the ATDC5/control, ATDC5/WISP-1L, and ATDC5/WISP-1H cell lines. Saturation density (B) and photomicrograph (C) of ATDC5 cell lines grown to confluency. D: Proliferation of ATDC5 (open squares), ATDC5/control (filled squares), ATDC5/WISP-1L (open circles), and ATDC5/WISP-1H cells (filled circles). E: Relative expression of collagen 2 in ATDC5/control, ATDC5/WISP-1L, and ATDC5/WISP-1H cells before (black bars) and after inducing chondrocytic differentiation by BMP-2 (gray bars) or GDF-5 (white bars).