Age-related increase in collagen production in cultured human osteoblast-like periosteal cells

Since collagen synthesis is a primary function of differentiated osteoblasts, we investigated the age-related changes in hydroxyproline content, procollagen mRNA level, collagenase activity and collagenase inhibitory activity in human osteoblast-like periosteal cell (OP cell) cultures established from donors of various ages. After achieving confluent growth, the OP cells were treated with 10(-8) M 1,25(OH)2 vitamin D3 in the presence of 2 mM alpha-glycerophosphate for 10 days to facilitate osteoblast differentiation. Hydroxyproline content of the treated cells increased with donor age. But pro alpha 1(I) collagen mRNA level increased until a donor age of 65, and decreased thereafter with increasing door age. Collagenase activity was not detected in cell extracts or the conditioned medium concentrated more than 10 times. However, OP cells had collagenase inhibitory activity which was five times higher in cells from aged donors than in cells from young donors. It is possible that cells from elderly donors accumulated much more collagen than cells from younger donors by inhibiting collagen degradation.