Differentiation of osteoblast in vitro is regulated by progesterone.

The regulation of cellular differentiation by progesterone in fetal rat calvarial osteoblasts was investigated. Our results showed that cells cultured in the presence of progesterone had a 7% increase in the alkaline phosphatase activity when compared to untreated cells. The concentration of osteocalcin in the conditioned medium from progesterone treated osteoblasts was 28% higher than that of untreated controls. In addition, administration of progesterone significantly enhanced the number and area of bone nodules. In conclusion, progesterone stimulates the differentiation of fetal rat calvarial osteoblastic cells in vitro.