The effect of 1,25-dihydroxyvitamin D3 on cartilage growth in neonatal mice.

The in vivo effects of 1,25(OH)2D3 on cell proliferation, tissue organization and matrix mineralization have been studied in condylar cartilage of neonatal mice. A relatively low dose of the metabolite, 50 ng/kg body weight, significantly reduced the incorporation of [3H]thymidine as well as the number of chondroblasts. The cartilage as a whole underwent a marked derangement in its organization, as many fibroblastlike cells appeared to occupy the zone of progenitor cells. There was a high degree of correlation observed between the effects of 1,25(OH)2D3 upon [3H]thymidine incorporation and the size of the condylar zone of chondroblasts. With increasing doses, enhanced mineralization was noted in the cartilaginous matrix, along with cartilage cell degeneration. These findings indicate that 1,25(OH)2D3 possesses an inhibitory effect upon both the proliferative activity of prechondroblasts and upon the capacity of those cells to differentiate into chondroblasts.