Transforming Growth Factor Beta (TGF-β) Regulates Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells by Promoting Wnt Signaling Pathway in Atrophic Nonunion

Abstract

During atrophic nonunion, Wnt signaling pathway is inhibited, resulting in inhibition of BMSC osteogenic differentiation. TGF-β regulates growth and development of the body. However, TGF-β’s effect on osteogenic differentiation of BMSCs in atrophic nonunion has not been reported. The bone tissue and serum of patients with atrophic nonunion and normal healing fractures were collected, and TGF-β mRNA and serum secretion were analyzed by Real time PCR and ELISA. Rat BMSCs were cultured and randomly divided into control group, TGF-β group and TGF-β siRNA group which was transfected with pcDNA-TGF-β plasmid or TGF-β siRNA respectively followed by analysis of cell proliferation by MTT assay, alkaline phosphatase (ALP) activity, Caspase3 activity, expression of RUNX2 and OPN and PPARγ2 mRNA by Real time PCR, and WNT5A and FZD3 expression by Western blot. TGF-β mRNA level and secretion in patients with atrophic nonunion was significantly reduced compared with patients with normal healing fractures (P < 0.05). Transfection of TGF-β siRNA down-regulated TGF-β expression in BMSCs, significantly inhibited cell proliferation, increased Caspase3 activity, decreased ALP activity, RUNX2 and OPN expression, increased PPARγ2 expression and deceased WNT5A and FZD3 expression (P < 0.05). However, transfection of pcDNA-TGF-β plasmid up-regulated TGF-β expression in BMSCs and reversed the above changes (P < 0.05). TGF-β is reduced in atrophic nonunion patients. Targeting TGF-β promotes BMSCs proliferation and osteogenic differentiation by regulating Wnt signaling pathway.