The protection of MSCs from apoptosis in nerve regeneration by TGFβ1 through reducing inflammation and promoting VEGF-dependent angiogenesis

Our previous report demonstrated that autologous adipose-derived mesenchymal stem cells (ADSCs) combined with xenogeneic acellular nerve matrix (XANM) can support the regeneration of defective nerves. Although ADSCs had the potential to replace Schwann cells in engineered-tissue nerves, apoptosis easily obstructed the ability to treat serious nerve injury in the host, such as a >50-mm-long nerve defect. In the present study, we found that, in combination with transforming growth factor beta 1 (TGF beta 1), an ADSCs-XANM graft was sufficient to support the regeneration of a 50-mm sciatic nerve defect, which was not achieved using an ADSCs-XANM graft alone. Based on this finding, we further investigated how TGF beta 1 coordinated with ADSCs to enhance nerve regeneration. In vitro, cell culture experiments demonstrated that TGF beta 1 did not have a direct effect on ADSC proliferation, apoptosis, the cell cycle, or neural differentiation. The expression of VEGF, however, was significantly increased in ADSCs cultured with TGF beta 1. In vivo, fluorescence labeling experiments demonstrated that the survival of transplanted ADSCs inoculated with XANM-TGF beta 1 was higher than with XANM. Further study showed that TGF beta 1 was capable of impairing the host immune response that was trigged by transplanted XANM. Additionally, we discovered that XANM-ADSCs in immunodeficient mice had apoptosis rates similar to XANM-ADSCs-TGF beta 1 over a short time course (7 days). Once we blocked VEGF with a neutralizing antibody, the protective effect of TGF beta 1 was impaired over a long time course (28 days). These results suggested that TGF beta 1 was capable of enhancing the regenerative capacity of an XANM-ADSCs graft, mainly by protecting transplanted ADSCs from apoptosis. This effect was achieved in part through decreasing inflammation and promoting VEGF-dependent angiogenesis. (C) 2012 Elsevier Ltd. All rights reserved.