CONICET | Buscador de Institutos y Recursos Humanos

Phytoestrogens have been proposed as a natural therapy for prevention of bone loss. In this work, we studied the mechanism ofaction of genistein on osteoblast differentiation. Primary cell cultures of calvarial osteoblasts isolated from female Wistar ratswere in vitro exposed to genistein. Osteoblast differentiation markers were measured. Genistein stimulated osteoblast migration(71?257% above control). An earlier upregulation of estrogen receptor alpha gene expression and an enhancement of mRNAlevels of the Runt-related transcription factor 2 were detected after 3 days of culture. The isoflavone significantly increasedosteocalcin expression, extracellular collagen deposition, and alkaline phosphatase activity. The mechanism displayed by genisteininvolved estrogen receptor and nitric oxide pathway participation, since cell preincubation with the estrogen receptorantagonist ICI 182780, or the nitric oxide synthase inhibitor L-NAME, suppressed the phytoestrogen action. Evidence ofMAPK and PI3K transduction systems participation on the stimulatory action of genistein on extracellular collagen depositionand alkaline phosphatase activity was also obtained. Genistein favored monocyte adhesion to osteoblasts (77%above control) inan ER; NOS; and MAPK kinase?dependent and PI3K-dependent manner. Co-cultured osteoblast-monocyte long term exposed(21 days) to genistein exhibited a high number of multinucleated and tartrate-resistant acid phosphatase?positive cells added toosteoblasts, suggesting that the phytoestrogen promotes osteoclast differentiation. In conclusion, genistein promoted osteoblastogenesisthrough the participation of ER and NOS pathways, and the contribution of ERK or PI3K signal transduction pathways,and also stimulates osteoclast differentiation from its mononuclear progenitor