Effects of vitamin D metabolites on collagen production and cell proliferation of growth zone and resting zone cartilage cells in vitro

Previous studies have suggested that vitamin D metabolites directly influence the differentiation and maturation of chondrocytes in calcifying cartilage. Recently, this laboratory has shown that the response of chondrocyte plasma membrane and matrix vesicle enzymes to 1,25-(OH)2D3 and 24,25-(OH)2D3 is both cell and membrane specific. The current study demonstrates that cell replication and matrix protein synthesis are also modulated by vitamin D. Confluent, third-passage growth zone (GC) and resting zone (RC) costochondral chondrocytes were incubated in medium containing 10(-13)-10(-7) M 1,25-(OH)2D3 or 10(-12)-10(-6) M 24,25-(OH)2D3. The amount of collagenase-digestible protein (CDP) secreted into the media was inversely proportional to the concentration of fetal bovine serum (FBS). At 10% FBS, greater than 80% of the CDP was incorporated into the matrix. 1,25-(OH)2D3 stimulated CDP and percentage collagen synthesis by GC cells but had no effect on the synthesis of noncollagenous protein (NCP). 1,25-(OH)2D3 inhibited CDP and percentage collagen synthesis by RC cells but did not alter NCP synthesis. [3H]thymidine incorporation was inhibited in both cell types, whether confluent or subconfluent cultures were examined. At 10(-6) and 10(-7) M 24,25-(OH)2D3, there was a significant decrease in CDP production and percentage collagen synthesis by RC cells but no effect on NCP. However, at 10(-9) and 10(-10) M hormone there was an increase in NCP production but no effect on CDP, resulting in a decrease in percentage collagen synthesis. CDP and NCP production were unaffected by 24,25-(OH)2D3 in GC cells. High concentrations of hormone inhibited [3H]thymidine incorporation in both cell types.(ABSTRACT TRUNCATED AT 250 WORDS)