IFN-γ Synergizes with TNF-α to Induce RIPK1-Independent Necroptosis of Mesenchymal Stem/Stromal Cells

Abstract

IFN-γ and TNF-α are two vital inflammatory factors elevated aberrantly in many diseases. Such an inflammatory microenvironment is detrimental to residual cells such as mesenchymal stem cells (MSCs), yet the precise mechanisms are not fully understood. IFN-γ and TNF-α have distinct effects on the immunoregulatory properties of MSCs, and they have been proposed as optimal priming factors to enhance the immunosuppressive capacity of engineered MSCs. Thus, the overall effects of IFN-γ and/or TNF-α exposure on MSCs needs to be elucidated. Here, it is found that IFN-γ and TNF-α synergistically induce cell death of MSCs via necroptosis. When MSCs are exposed to both IFN-γ and TNF-α, their morphological features and biological functions are impaired. Mechanistically revealed by RNA-Sequencing, the injured MSCs undergo a unique cell death process, namely necroptosis. Compared with controls, IFN-γ synergized with TNF-α to increase the expression of RIPK1, RIPK3, MLKL, and all other genes associated with necroptosis. Rescue experiments further demonstrate that this process can be reversed by RIPK3 and MLKL inhibitors but not by the RIPK1 inhibitor, suggesting a RIPK1-independent pathway. Collectively, this study discloses an inflammatory injury mechanism of MSCs, which may shed new light on revealing the MSCs deficits in many inflammatory diseases with expectations to inspire 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.

Keywords: IFN‐γ; TNF‐α; cell death; mesenchymal stem/stromal cells; necroptosis.