IFN-γ synergizes with TNF-α to induce RIPK1-independent necroptosis of mesenchymal stem/stromal cells

Interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α) are two vital inflammatory factors elevated in many diseases. An inflammatory microenvironment is detrimental to residual cells, yet the precise mechanisms of cell impairment are not fully understood. IFN-γ and TNF-α have distinct effects on the immunoregulatory properties of mesenchymal stem/stromal cells (MSCs) and they have been raised to be optimal prime factors to enhance the immunosuppressive capacity of in vitro engineered MSCs. However, controversies remain with regard to the normal function maintenance of cells as they may be impaired after exposure to inflammatory factors. Here, we found that IFN-γ synergises with TNF-α to induce cell dysfunction and death of MSCs via necroptosis. When MSCs were exposed to both IFN-γ and TNF-a, its morphological features and biological functions were injured. Mechanistically revealed by RNA-Sequencing, the injured MSCs undergone a unique cell death process, namely necroptosis. Compared with controls, IFN-γ and TNF-a synergistically increased the expression of RIPK1, RIPK3, MLKL and all other genes associated with necroptosis significantly. Rescue experiments further showed that the process could be reversed by RIPK3 and MLKL inhibitor but RIPK1inhibitor, suggesting a RIPK1-independent pathway and a promising cell preservative approach. Collectively, these results disclose an inflammatory injury mechanism of MSCs, which may shed new light on revealing the MSCs deficits in some inflammation associated diseases with expectations to innovate some potential targeted therapies. In addition, inflammatory impairment should be taken into consideration when delivering cell therapy based on MSCs primed with IFN-γ and TNF-α.