Prostaglandins E (PGEs) are abundantly produced in the skeletal tissue, the turnover of which they can modulate acting on both bone deposition and resorption. We compared the effects of PGE1 and PGE2 on the growth and differentiation of rat bone-marrow osteoblast-like cells cultured in vitro. Both PGEs stimulated cultured cell growth, PGE2 being more effective than PGE1. PGE1 inhibited and PGE2 enhanced alkaline phosphatase activity. Both PGEs markedly raised osteocalcin synthesis, without apparently affecting collagenase-digestible protein production. Scanning electron microscopy showed that untreated cultured osteoblast-like cells were arranged in clusters and displayed a polygonal shape. PGE1 did not alter cell morphology, while PGE2 provoked elongation of cultured cells and sprouting of slend cytoplasmic processes. Morphometric analysis indicated that PGE1 decreased and PGE2 increased cultured-cell dimensions. Collectively, these findings allow us to conclude that PGE1 and PGE2, although being both able to enhance proliferation of osteoblast-like cells cultured in vitro, exert divergent effects on their differentiation. PGE1 seems to slow-down osteoblast maturation, while PGE2 appears to stimulate osteoblast differentiation to mature osteocytes.

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