Effects And Mechanisms Of MSCs On T Cell Autophagy In SLE Patients

1.BackgroundSystemic lupus erythematosus(SLE)is a kind of prototypic autoimmune disease,characterized by overactivated immune responses,formation of autoantibodies,etc.And it could cause damage to multiple organs.Although there are increasing studies focusing on the pathogenesis of this disease,the underline mechanism is still not clearly elucidated.T cells play important roles in the onset of SLE,including secreting inflammatory factors and helping B cells to produce autoantibodies,such as ANA and anti-dsDNA antibodies.As it has been shown,T cells from patients with SLE undergo increasing spontaneous apoptosis.However,the reason remains unknown and the consequence on SLE is not clear,either.Some studies showed that immune complexes containing DNA from apoptotic cells could induce the production of inflammatory factors,such as IFNa,TNFa,IL-1?,IL-10,etc,and promote the formation of anti-dsDNA antibodies.However,so far there are no reports on whether apoptotic T cells participate in this process in SLE.Autophagy is essential for cellular basal homeostasis.It could prevent cells from death under stress,such as inflammation,nutrient starvation,etc.However,overactivated autophagy could lead to cell death as well.Recent studies demonstrated that autophagy played an important role in autoimmune diseases,including SLE.However,it remains unclear how the autophagy participates in the onset of SLE.As a novel therapy for SLE,UC-MSCs transplantation has shown marked clinical effect.Besides multiple differentiating potential and repairing function,UC-MSCs are also very powerful in immune-regulation.They can regulate both the number and function of T/B/APC cell subsets,decrease inflammatory factors and autoantibodies,and improve organ function as well.However,there are still no reports of their roles on T cell autophagy.Meanwhile,the mechanism of UC-MSCs to decrease autoantibody formation remains unclear,either.2.Aims(1)To elucidate the pathogenic role of aberrant T cell autophagy in SLE;(2)To investigate UC-MSCs' regulation on T cell autophagy.3.ResultsPart ? Enhanced T cell autophagy in SLEAs it is shown before,T cells from patients with SLE have an increased spontaneous apoptosis and aberrant autophagy comparing to that of healthy donors.The appearance of nucleosomes from apoptotic cells could induce autoantibody formation,such as anti-dsDNA and ANA antibodies.However,the relationship between autophagy and apoptosis in SLE is still unclear.In this study,we found that T cells from SLE patients had an elevated basal autophagy and higher response to anti-CD3/CD28 stimulation of autophagy,which could lead to T cell apoptosis.Furthermore,the spontaneous apoptosis rate of CD8+T cells had a significant correlation with serum anti-dsDNA antibody level.Supernatants from apoptotic T cells could stimulate ANA antibody formation by PBMC from SLE patients.Our findings demonstrate aberrant autophagy may lead to the increase of T cell apoptosis and thus contribute to autoantibody formation in SLE patients.Part ? UC-MSCs inhibit the autophagy of T cells from SLE patientsOur previous clinical trials have shown that UC-MSCs transplantation had significant efficacy,including organ improvement and autoantibody decrease in SLE patients.In this study,we found that mitochondrial function of T cells from SLE patients was impaired,which could lead to AMPK activation and subsequent autophagy upregulation.We found UC-MSCs could decrease the apoptosis rate of T cells from SLE patients by transferring mitochondria to T cells and downregulating their autophagy level,subsequently decreasing the production of autoantibodies induced by apoptotic T cells.Meanwhile,UC-MSCs could also inhibit T cell proliferation by suppressing mTOR activation.Our results suggest a new mechanism for the treatment of UC-MSCs in SLE patients.Part ? Impaired autophagy of MSCs influence their regulatory function on T cellsBesides T cells,we found bone-marrow-derived mesenchymal stem cells(BMMSCs)from SLE patients had an abnormal autophagy as well.Comparing to BMMSCs from healthy donors,SLE BMMSCs had a decreased autophagy flux and an accumulation of LC3IIB.Autophagy plays an important role in keeping the homestasis of proliferating cells,including clearance of impaired mitochondria.Thus the accumulation of impaired mitochondria due to abnormal autophagy would result in weakened regulatory function of UC-MSCs towards T cells in SLE.Our further experiments demonstrated that autophagy obstruction of UC-MSCs with chloroquine caused mitochondria accumulation and abrogated their regulation on T cell apoptosis and autophagy.To investigate the possible reasons for BMMSCs autophagy impairment,we found that IFNa,IFNy and TNFa could decrease the autophagy flux of UC-MSCs,leading to the accumulation of p62.The above results further confirm the important role of autophagy in the pathogenesis of SLE and suggest abnormal autophagy of BMMSCs from SLE patients due to elevated inflammatory factors could influence their regulatory function on T cells.