Chondrocyte markers and MafB expression in neonatal bone: responses to different levels of maternal dietary vitamin A and direct neonatal supplementation with vitamin A and retinoic acid

Vitamin A (VA) and its active form, retinoic acid (RA), regulate skeletal development and chondrogenesis. We investigated whether maternal VA intake and direct oral supplementation of neonates with VA+RA (VARA) alters neonatal bone formation. Weanling rats were assigned to three groups: VA marginal, VA adequate and VA supplemented, fed for 10 wk, mated, and their offspring were then studied at birth (P0) and on postnatal day 7 (P7). Additionally, some of the newborns were orally supplemented with VARA or oil every other day, and bone was collected 6 h after the last oral dose on P7. Neonatal VA status (liver, lung and plasma retinol) and VA homeostatic genes (CYP26A1, B1, LRAT) were regulated by both maternal VA status and neonatal treatment with VARA ( P <0.05). However, bone formation assessed by Alcian blue and von Kossa staining were not changed by maternal dietary VA. Neither collagen type II nor type X, chondrocyte markers, were significantly changed. MafB is a transcription factor involved in development. MafB mRNA and protein were highly expressed in proliferative but not hypertrophic chondrocytes. Moreover, MafB expression was not altered by VA intake. In conclusion, intakes of VA within the range present in most human diets, from marginal to supplemented, as well as neonatal supplementation with VARA, did not perturb MafB and other markers of collagen and bone formation in neonatal bone. Grant Funding Source : NIH CA‐90214 and Dept. Nutritional Sciences