The Mechanism Of MSCs Regulation On CD4~+LAP~+T Cells In The Treatment Of Patients With Systemic Lupus Erythematosus

Background:Systemic lupus erythematosus(SLE)is a chronic systemic autoimmune disease with multiple organ damage.The pathogenesis is complicated,including reduced number and impaired function of regulatory T cells(Treg),overactivated B cells and excessive antibody production.Recently,CD4+LAP+(Latency-associated peptide)T cells,a new Treg subset,have been identified.A few studies have shown that CD4+LAP+T cells exhibited strong immunoregulatory capability,and play an important role in many diseases.Mesenchymal stem cells(MSCs)are pluripotent stem cells with immunoregulatory function and exert significant therapeutic effect on refractory SLE.However,the mechanism remains unclear.Objective:This study was to investigate the percentage change of CD4+LAP+T cells and its clinical significance,and to explore how umbilical cord mesenchymal stem cells(UC-MSCs)regulate CD4+LAP+T cells in SLE patients.Methods:The percentages of CD4+LAP+T cells in peripheral blood from SLE patients,rheumatoid arthritis(RA)patients and healthy control(HC)were detected by flow cytometry(FCM).The correlations between the percentages of CD4+LAP+T cells and SLE disease activity index(SLEDAI)scores,serum levels of complement C3,C4 and C-reactive protein(CRP)were analyzed respectively.Peripheral blood mononuclear cells(PBMCs)from SLE patients and HC were cultured and activated in vitro,then the percentage of CD4+LAP+T cells was determined by FCM.SLE and HC PBMCs were cultured in the presence of IL-2 or IL-6 respectively,and the percentage of CD4+LAP+T cells were measured.Naive CD4+T cells were isolated from the peripheral blood of HC and cultured with IL-2 or IL-6,and the percentage of CD4+LAP+T cells was examined.Gene expression of transforming growth factor-p receptor 1(TGF-βR1)and TGF-βR2 in SLE and HC PBMCs was measured by RT-PCR.Five SLE patients recieved UC-MSCs transplantation,and their peripheral blood was collected before and after 24 hours of cell infusion.The pecentages of CD4+LAP+T cells were detected by FCM and the plasma TGF-β1 was determined by ELISA.SLE PBMCs were cocultured with or without UC-MSCs for 24 hours,and then gene expression of TGF-βR1 and TGF-PR2 was examined by RT-PCR.Results:Compared to HC,fewer CD4+LAP+T cells were detected in SLE patients(2.5±0.2%vs 3.4±0.2%,p<0.01),and it negatively correlated with serum CRP and liver enzyme levels respectively.After activation,the percentages of CD4+LAP+T cells in PBMCs of SLE were significantly higher than those of HC(6.6±0.8%vs 4.2±0.6%,p<0.05).Neither IL-2 nor IL-6 had an effect on the poliferation and differentiation of CD4+LAP+T cells.However,both the gene expression of TGF-βRl and TGF-βR2 in SLE PBMCs showed a declined trend compared with that in HC PBMCs,and there was no statistical significance.24 hours after UC-MSCs transplantation,the percentages of CD4+LAP+T cells increased obviously in SLE patients(3.6±0.9%vs 2.1±0.6%,p<0.05).Furthermore,SLE PBMCs cocultured with UC-MSCs exhibited higher gene expression of TGF-βR2 than that cultured alone(5.17±0.74 vs 1.17±0.33,p<0.01).Conclusions:The significantly decreased percentages of CD4+LAP+T cells in patients with SLE suggest that it may participate in the pathogenesis of SLE.UC-MSCs transplantation can upregulate the percentages of CD4+LAP+T cells in SLE patients,which probably through the upregulation of TGF-βR2.The modulatory effects of UC-MSCs on CD4+LAP+T cells may be one of the mechanisms of UC-MSCs therapy in ameliorating lupus disease.