Effects of Transforming growth factor-beta3 on osteoblast proliferation and differentiation

Exogenous application of transforming growth factor-beta3 (Tgf-beta3) cytokine has been shown to inhibit cranial suture fusion in wild-type murine models and in craniosynostotic rabbits. It is necessary to establish the mechanism by which Tgf-beta3 inhibits the cranial suture fusion before it can be considered for therapeutic applications. It has been speculated that Tgf-beta3-induced suture maintenance is possibly mediated by upregulation of apoptosis, accompanied by decreased levels of cell proliferation and differentiation. Objective: This study was designed to determine the effects of Tgf-beta3 on the proliferation and differentiation of osteoblasts. Methods: Mouse osteoblast-like MC3T3-E1 cells were cultured in 6-well culture plates with or without Tgf-beta3. Controls received growth factor vehicle only (0.1% BSA). Cell proliferation and osteoblast differentiation were determined by Alamar blue assay and alkaline phosphatase (AP) activity assay, respectively. Results: Proliferation of osteoblasts treated with Tgf-beta3 was reduced at least 20% and 60% on day 5 and 7 respectively. AP activity of cells treated with Tgf-beta3 was similar to that of controls. Conclusion: Tgf-beta3 did not affect the differentiation of osteoblasts. However Tgf-beta3 inhibited osteoblast proliferation, which may have inhibited the fusion of Tgf-beta3-treated cranial sutures.