Effect of Retinoic Acid on Osteocalcin Gene Expression in Human Osteoblasts

Abstract It is well known that the expression of osteocalcin, the only recognized osteoblast-specific protein, is regulated by 1α-25-dihydroxyvitamin D 3 through a distinct vitamin D 3 receptor and a cis-acting DNA response element. In addition, recent data obtained with plasmid constructs have shown a positive interaction between retinoic acid activated receptor(s) and the osteocalcin gene promoter. Our studies, carried out on primary cultures of human osteoblasts, have demonstrated for the first time the activation of the osteocalcin gene expression by retinoic acid. Moreover, a remarkable synergistic effect between the hormonal forms of vitamin A and D 3 on the synthesis of this bone-specific protein was observed.