Effect and interaction of transforming growth factor-beta (TGF-β) and bone morphogenetic protein (BMP) on proliferation and differentiation of primary cult ured osteoblast-like cells of fetal rabbit calvarium

Objective To study the effects and interactions of transforming gr owth factor-beta (TGF-β) and bone morphogenetic protein (BMP) on the prolifer ation and differentiation of osteoblast-like cells primary cultured in vitro. M ethods Different in vitro culture models of osteoblast-like cells of fetal rabb it calvarium were established and treated continuously with TGF-βand BMP, alone or in combination, and sequentially either with BMP from day 0 to day 9, followed by TGF-βfrom day 9 to day 19, or with TGF-βfrom da y 0 to day 10, followed by BMP from day 10 to day 21. DNA content, alkaline phos phatase (ALP) activity, osteocalcin and calcium content were measured at differe nt timed-points. Results TGF-βincreased DNA content, but inhibited ALP activi ty, osteocalcin production and mineralization of the matrix formed by osteoblast -like cells. In contrast, BMP increased ALP activity, osteocalcin levels and ca lcium deposition in the extracellular matrix, and decreased DNA content. In the co-treatment with TGF-βand BMP, TGF-βattenuated the stimulatory effect of B MP on osteocalcin levels and ALP activity, whereas BMP reduced the TGF-β-enha nced DNA synthesis. In the sequential treatments with TGF-βand BMP, an early ( 9 days) treatment with BMP did not affect the subsequent TGF-βinhibition of os teoblast-like cells on ALP activity and calcium deposition in the extracellular matrix, whereas an early (10 days) treatment with TGF-βinduced the subsequent BMP action on osteoblast-like cell differentiation. Conclusions TGF-βstimula tes cell proliferation whereas BMP promotes cell differentiation towards the ost eoblastic lineage. TGF-βand BMP interact with each other in a sequential manne r at different stages to modulate cooperatively and synergistically the prolifer ation and differentiation of osteoblast-like cells.