Cell–cell contact with proinflammatory macrophages enhances the immunotherapeutic effect of mesenchymal stem cells in two abortion models

Mesenchymal stem cells(MSCs),which are pluripotent cells with immunomodulatory properties,have been considered good candidates for the therapy of several immune disorders,such as inflammatory bowel diseases,concanavalin A-induced liver injury,and graft-versus-host disease.The embryo is a natural allograft to the maternal immune system.A successful pregnancy depends on the timely extinction of the inflammatory response induced by embryo implantation,followed by the switch to a tolerant immune microenvironment in both the uterus and the system.Excessive infiltration of immune cells and serious inflammatory responses are triggers for embryo rejection,which results in miscarriage.Here,we demonstrated that adoptive transfer of MSCs could prevent fetal loss in a lipopolysaccharide(LPS)-induced abortion model and immune response-mediated spontaneous abortion model.The immunosuppressive MSCs alleviated excessive inflammation by inhibiting CD4+T cell proliferation and promoting the decidual macrophage switch to M2 in a tumor necrosis factor-stimulated gene-6(TSG-6)-dependent manner.Cell-tocell contact with proinflammatory macrophages increased the TSG-6 production by the MSCs,thereby enhancing the suppressive regulation of T cells and macrophages.Moreover,proinflammatory macrophages in contact with the MSCs upregulated the expression of CD200 on the stem cells and facilitated the reprogramming of macrophages towards an anti-inflammatory skew through the interaction of CD200 with CD200R on proinflammatory macrophages.Therefore,the results demonstrate that a TSG-6-mediated paracrine effect,reinforced by cell-to-cell contact between MSCs and proinflammatory macrophages,is involved in the mechanism of MSC-mediated abortion relief through the induction of immune tolerance.Our study also indicates the potential application of MSCs in clinical recurrent miscarriages.

Inflammation-induced inhibition of chaperone-mediated autophagy maintains the immunosuppressive function of murine mesenchymal stromal cells

Macroautophagy has been implicated in modulating the therapeutic function of mesenchymal stromal cells(MSCs).However,the biological function of chaperone-mediated autophagy(CMA)in MSCs remains elusive.Here,we found that CMA was inhibited in MSCs in response to the proinflammatory cytokines interferon-γ(IFN-γ)and tumor necrosis factor-α(TNF-α).In addition,suppression of CMA by knocking down the CMA-related lysosomal receptor lysosomal-associated membrane protein 2(LAMP-2A)in MSCs significantly enhanced the immunosuppressive effect of MSCs on T cell proliferation,and as expected,LAMP-2A overexpression in MSCs exerted the opposite effect on T cell proliferation.This effect of CMA on the immunosuppressive function of MSCs was attributed to its negative regulation of the expression of chemokine C-X-C motif ligand 10(CXCL10),which recruits inflammatory cells,especially T cells,to MSCs,and inducible nitric oxide synthase(iNOS),which leads to the subsequent inhibition of T cell proliferation via nitric oxide(NO).Mechanistically,CMA inhibition dramatically promoted IFN-γplus TNF-α-induced activation of NF-κB and STAT1,leading to the enhanced expression of CXCL10 and iNOS in MSCs.Furthermore,we found that IFN-γplus TNF-α-induced AKT activation contributed to CMA inhibition in MSCs.More interestingly,CMA-deficient MSCs exhibited improved therapeutic efficacy in inflammatory liver injury.Taken together,our findings established CMA inhibition as a critical contributor to the immunosuppressive function of MSCs induced by inflammatory cytokines nd highlighted a previously unknown function of CMA.