Effects of TGF-β1 Overexpression on Biological Characteristics of Human Dental Pulp-derived Mesenchymal Stromal Cells

OBJECTIVE: The aim of our study was to investigate the effect of Transforming growth factor beta-1 (TGF-β1) gene therapy on the surface markers, multilineage differentiation, viability, apoptosis, cell cycle, DNA damage and senescence of human Dental Pulp-derived Mesenchymal Stromal Cells (hDPSC). METHODS: hDPSCs were isolated from human teeth, and were cultured with 20% Fetal Bovine Serum (FBS) in minimum essential media-alpha (α-MEM). TGF-β1 gene transfer into hDPSCs was performed by electroporation method after the plasmid was prepared. The transfection efficiency was achieved by using western blot and flow cytometry analyses and GFP transfection. Mesenchymal stem cell (MSC) markers, multilineage differentiation, cell proliferation, apoptosis, cell cycle, DNA damage and cellular senescence assays were performed by comparing the transfected and non-transfected cells. Statistical analyses were performed using GraphPad Prism. RESULTS: Strong expression of TGF-β1 in pCMV-TGF-β1-transfected hDPSCs was detected in flow cytometry analysis. TGF-β1 transfection efficiency was measured as 95%. Western blot analysis showed that TGF-β1 protein levels increased at third and sixth days in pCMV-TGF-β1-transfected hDPSCs. The continuous TGF-β1 overexpression in hDPSCs did not influence the immunophenotype and surface marker expression of MSCs. Our results showed that TGF-β1 increased osteogenic and chondrogenic differentiation, but decreased adipogenic differentiation. Overexpression of TGF-β1 increased the proliferation rate and decreased total apoptosis in hDPSCs (p<0.05). The number of cells at “S” phase was higher with TGF-β1 transfection (p<0.05). Cellular senescence decreased in TGF-β1 transfected group (p<0.05). CONCLUSIONS: These results reflect that TGF-β1 has major impact on MSC differentiation. TGF-β1 transfection has positive effect on proliferation, cell cycle, and prevents cellular senescence and apoptosis.