Influence of Wnt proteins (A) and GSK-3β inhibitors (B) on superficial zone protein (SZP) accumulation in surface zone articular chondrocytes. Primary cells were cultured for 4 days as monolayers in serum-free chemically defined medium with graded levels (10, 30, and 100 ng/ml) of Wnt proteins (Wnt-3a, -5a, and -11) or indicated concentration of GSK-3β inhibitors (Lithium chloride (LiCl), BIO, SB415286 and SB216763). SZP accumulation in spent medium was quantified according to enzyme-linked immunosorbent assay. Wnt-3a significantly suppressed SZP accumulation, but Wnt-5a and -11 had no influence on SZP accumulation (A). All GSK-3β inhibitors significantly suppressed SZP accumulation compared to untreated and vehicle control (B). Values are the mean ± standard deviations, with n=6 (*p<0.01 compared with the value of the control cultures).