Prostaglandins regulate the expression of fibroblast growth factor-2 in bone

Fibroblast growth factor-2 (FGF-2) and prostaglandins (PGs) are mitogenic for bone cells and have biphasic effects on bone formation. FGF has been shown to stimulate prostaglandin production. In this study we examined the effect of PGs, particularly prostaglandin F2 alpha (PGF2alpha) and the selective PGF2alpha agonist, fluprostenol (Flup), on FGF-2 mRNA and protein in the immortalized rat osteoblastic cell line Py1a and 21 day fetal rat calvariae. Py1a cells were grown to confluence in Ham’s F-12 medium containing 5% fetal calf serum and then serum deprived for 24 h before treatment with PGs. FGF-2 mRNA levels were analyzed be Northern blot, quantitated by densitometry and normalized to glyceraldehyde 3 phosphate dehydrogenase mRNA. In control cultures, Py1a cells constitutively expressed FGF-2 transcripts of approximately 4, 2, and 1.5 kb with low levels of a 6 kd transcript. Treatment with Flup for 3 hours caused an approximately 2-fold increase in cytoplasmic labeling for FGF-2 protein in periosteal cells, osteoblasts and osteocytes. However, there was decreased labeling of the matrix. We conclude that PGs can induce high molecular weight FGF-2 transcripts and increase FGF-2 protein in bone cells. These data suggest that some effects of PGs on bone remodeling may be mediated by the regulation of endogenous FGF-2 production.