Fig. 4

a and b, Effects of bone morphogenetic protein (BMP) family members on SZP accumulation in superficial zone articular chondrocytes (a) and synoviocytes (b). Primary superficial zone articular chondrocytes and synoviocytes were cultured for 3 days as monolayers in serum-free chemically defined medium with or without the addition of BMPs or growth differentiation factor 5 (GDF-5). SZP accumulation in the culture medium was quantified by enzyme-linked immunosorbent assay. Responses to BMPs were much higher in synoviocytes than in chondrocytes. * = P < 0.05; ** = P < 0.01, versus control. C and D, Effects of concurrent treatment with TGFβ1 (1 ng/ml) and BMPs (100 ng/ml) on SZP accumulation in superficial zone articular chondrocytes (c) and synoviocytes (d). SZP accumulation with the combined treatment was significantly higher than that observed with each treatment alone (P < 0.05), and the additive action was seen in both superficial zone articular chondrocytes and synoviocytes. Values are the mean and SEM from 7 individual experiments, each with cartilage from a different animal. T + B2 = TGFβ1 plus BMP-2; T + B4 = TGFβ1 plus BMP-4; T + B7 = TGFβ1 plus BMP-7; T + G5 = TGFβ1 plus GDF-5 [82]