关键词: 根尖牙乳头干细胞, CD4+ T细胞, 调节性T细胞, Foxp3, DNA去甲基化

Abstract: Objective    To study the effect of stem cells from apical papilla（SCAP）on methylation status of Foxp3 locus in CD4+ T cells，clarifying the role of SCAP in promoting the conversion of CD4+ T cells to regulatory T cells（Tregs）. Thus this study can provide theoretical foundation and experimental basis for further exploring the mechanism of immunoregulatory role of the dental-derived stem cells. Methods    Human SCAP and mouse spleen CD4+ T cells were isolated and identified respectively. SCAP and CD4+ T cells were co-cultured at a ratio of 1∶5 for 72 h via transwell in vitro（co-culture group），and CD4+ T cells cultured alone were used as the control group. Flow cytometry was used to detect the ratio of Tregs. Hydroxymethylated DNA immunoprecipitation-polymerase chain reaction（hMeDIP-PCR）was used to evaluate the expression level of 5-hydroxymethylcytosine（5hmC）at Foxp3 locus in CD4+ T cells. Enzyme-linked immunosorbent assay（ELISA）was used to measure the expression level of the Tregs′ effector interleukin-10（IL-10）in the co-culture supernatant. Results    Primary cultured SCAP expressed mesenchymal stem cell surface markers （CD105，CD90，CD44，CD29）， and were negative for hematopoietic stem cell markers （CD45，CD34）. Compared with the control group，the ratio of Tregs and the expression level of 5hmC at Foxp3 locus in CD4+ T cells was elevated by SCAP in the co-culture group. The level of anti-inflammatory cytokine interleukin-10（IL-10）in the co-culture supernatant was increased by SCAP as well. The differences were statistically significant（P < 0.001）. Conclusion　SCAP can up-regulate the expression level of Foxp3，and induce DNA demethylation of Foxp3 locus in CD4+ T cells by paracrine factors，which promotes CD4+ T cells to convert to Tregs and then plays a role in immunoregulation.

Key words: stem cells from apical papilla, SCAP；CD4+ T cells；regulatory T cells, Tregs；Foxp3；DNA demethylation