Effects of ascorbic acid on collagen mRNA levels in short term chondrocyte cultures

Chondrocytes isolated from 16 day chicken embryo sterna and adult (18 month) bovine metacarpalphalangeal joint cartilage were grown in monolayer culture for up to 5 days in the presence and absence of ascorbate (50 micrograms/ml). RNA was isolated from these cultures and the steady-state levels of alpha 1(I), alpha 2(I) and alpha 1(II) mRNAs were assayed using cloned DNA probes encoding the respective procollagen mRNAs. Both ascorbate-treated and control chicken chondrocytes maintained the characteristic morphology and phenotype synthesizing the same levels of type II procollagen mRNA observed for sternal chondrocytes. The chicken chondrocytes, with or without ascorbate, did not synthesize increased levels of alpha 1(I) or alpha 2(I) mRNA. In contrast, when bovine articular chondrocytes were cultured with ascorbate, an increase in type II procollagen mRNA and, more interestingly, an increase in type I procollagen mRNA was observed during the 5 day culture period. Low levels of type I procollagen mRNA were detected in untreated chicken and bovine cultured chondrocytes and chicken chondrocytes isolated from sterna. These experiments suggest that when cultured in the presence of ascorbate under the conditions examined, chicken embryo chondrocytes retain the differentiated phenotype unaffected by ascorbic acid while bovine articular chondrocytes begin to undergo a phenotypic change.