ABSTRACT
Objective To investigate the effect of human umbilical cord mesenchymal stem cells (hUC-MSCs) on autophagy and the secretion of chemokine receptor CXCR4 induced by low-dose immunosuppressive durgs.Methods Flow cytometry was used to detect the changes of hUC-MSCs surface markers after treatment with low-dose tacrolimus and rapamycin.The effect of treatment with tacrolimus and rapamycin on proliferation of hUC-MSCs was analyzed with WST-1 assay.Regular RT-PCR was applied to analyze the mRNAs expression of ligands such as LC3B,Atg5 and Beclin1 in hUC-MSCs.Western blotting was carried out to detect the expression of LC3B,Atg5,Beclin1 and p-ULK1 in hUC-MSCs after treatment with tacrolimus and rapamycin.The secretion of chemokine receptor CXCR4 in hUC-MSCs was analyzed under the state of autophay by flow cytometry.Results Flow cytometry analysis confirmed low-dose immunosuppressive drugs tacrolimus and rapamycin did not cause changes in hUC-MSCs phenotypes significantly.Low-dose tacrolimus had no cytotoxic effect on hUC-MSCs,while,rapamycin could inhibit the proliferation of hUC-MSCs after 24 h or 48 h,with survival rate being 73.66％ and 68.81％ (P＜0.05) of controls,respectively.Moreover,both tacrolimus and rapamycin could inhibit PI3K/AKt/mTOR signaling pathway to activate hUC-MSCs autophagy,and the related proteins of LC3B,Atg5 and Beclin1 increased significantly and induced the up-regulation of CXCR4 secretion.Conclusion Our results here demonstrated that low-dose tacrolimus and rapamycin induce autophagy in hUC-MSCs and promote the secretion of CXCR4.