Bone Abstracts

The effects of prolactin on bone metabolism have been the subjects of several studies. It is believed that prolactin acts directly influencing the synthesis of bone matrix by stimulating the osteoblastic activity, since receptors for this hormone have been identified in osteoblasts and human mesenchymal stem cells (MSCs). However, no study on the effects of prolactin on the osteogenic differentiation of MSCs was found in the literature. The objective of this study was to verify the in vitro effect of prolactin under osteogenic potential of bone marrow mesenchymal stem cells (BMMSCs) of young female rats. BMMSCs were grown in osteogenic medium and were separated into two groups: i) BMMSCs of young rats (control) and ii) BMMSCs of young rats treated with prolactin (100 ng/ml). At 7, 14, and 21 days of osteogenic differentiation of BMMSCs, 3-4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) conversion, gene expression for collagen I, osteocalcin, osteopontin, BMP-2, osterix and the cells number/field were analyzed. The percentage of mineralized nodules was analyzed at 21 days. The addition of prolactin in the BMMSCs culture increased the expression of osterix at 7 days and alkaline phosphatase at 14 days. However the expression of osteopontin in the prolactin group was lower at 21 days when compared to the control group. Expression of BMP-2, osteocalcin, type I collagen was not different between groups. Also no significant difference between groups in the conversion of MTT into formazan crystals, cell number and percentage of mineralized nodules. It was concluded that the prolactin in a dose of 100 ng/ml does not alter the osteogenic potential of BMMSCs of young female rats.