9-cis retinoic acid antagonizes the stimulatory effect of 1,25 dihydroxyvitamin D3 on chondrogenesis of chick limb bud mesenchymal cells: interactions of their receptors.

Retinoids or vitamin D have been found to profoundly affect pattern formation and chondrogenesis in the developing limb. These substances mediate their actions through their nuclear receptors. In the present investigation, we present data showing that 9-cis RA, the ligand for RXR can stimulate chondrogenesis of chick limb bud mesenchymal cells, however, in combination, it antagonizes the stimulatory effect of vitamin D in the same system. The receptors for 9-cis RA (RXR) and vitamin D (VDR) were also shown to be present in the mesenchymal cells and to form heterodimers. These results implicate these receptors in cartilage differentiation during limb development.