地西他滨诱导体内Foxp3基因表达上调延长心脏移植小鼠的存活时间

Prolongation of cardiac allograft survival in mice by Decitabine-induced upregulation of Foxp3 expression

目的探讨甲基转移酶抑制剂地西他滨诱导体内叉状头螺旋转录因子（Foxp3）基因表达延长同种心脏移植小鼠存活时间的作用及其机制。方法以经丝裂霉素处理的Balb／c小鼠和C57BL／6小鼠脾细胞作为刺激细胞，未经丝裂霉素处理的C57BL／6小鼠脾细胞作为反应细胞，进行体外单向混合淋巴细胞培养，观察地西他滨对培养体系中CD4^＋CD25^＋调节性T淋巴细胞（Treg细胞）比例的影响。分别以Balb／c小鼠和C57BL／6小鼠作为供、受者，建立同种小鼠腹部异位心脏移植模型。实验组受鼠术后1～3d经尾静脉注射地西他滨（1．5mg／kg），同种对照组受鼠术后1～3d经尾静脉注射等体积生理盐水。监测两组移植心存活时间，检测受鼠外周血CD4^＋CD25^＋Treg细胞比例及Foxp3mRNA的表达，观察移植心组织病理学变化。结果地西他滨能够上调体外同种混合淋巴细胞反应体系中CD4^＋CD25^＋Treg细胞的水平。同种对照组和实验组移植心脏中位存活时间分别为7和11d，实验组较对照组明显延长（P〈0．01）。与同种对照组相比，实验组CD4^＋CD25^＋Treg细胞比例和Foxp3mRNA的表达均明显升高（P〈0．01）；移植心肌炎症细胞浸润的程度明显减轻。结论地西他滨能够诱导同种心脏移植小鼠体内Foxp3基因的表达，从而明显减轻急性排斥反应，延长移植心存活时间，其机制可能与Foxp3表达能够诱导CD4^＋CD25^＋Foxp3^＋Treg细胞的增殖和分化密切相关。

Objective To investigate the effect of Foxp3 gene expression induced with the DNA methyltransferase inhibitor 5-aza-2-deoxycytidine （Aza） in recipients on ameliorating allograft rejection and prolonging allograft survival and the possible mechanisms. Method BALB/c and C57BL/6 splenocytes treated with mitomycin （MMC） served as the stimulators, those not treated with MMC as responders, and they were subjected to one-way mixed lymphocyte culture （MLC）. In the presence or absence of Aza, the percentage of CD4^＋ CD25^＋ Tregs was detected by flow cytometry. Abdominal heterotopic heart transplantation model was established by using inbred male Balb/c mice as donors and C57BL/6 as recipients respectivdy. In experimental group, recipients were intravenously administrated with decitabine （1.5 mg/kg/day） on the day 1 to day 3 post-transplantation. The control mice were treated with normal saline. CD4^＋ CD25^＋ Tregs proportion in the blood and Foxp3 mRNA in cardiac grafts and spleen of recipients were measured respectively, and the survival and the histopathologic changes of the cardiac grafts were also observed. Result Decitabine enhanced the proliferation CD4^＋ CD25^＋ Tregs of MLC in vitro. The median survival time of the cardiac grafts in experimental group （ 11 days） was longer than that in control group （7 days） （P~ 0. 01 ）. As compared with control group, Foxp3 mRNA expression in the cardiac grafts and spleen in recipient mice was significantly up-regulated, and CD4^＋ CD25^＋ Tregs proportion was increased （P%0. 01 ） and the proliferation of lymphoeytes and monoeytes infiltration was inhibited. Conclusion Up-regulation of Foxp3 gene expression induced with decitabine in recipients could alleviate cardiac allograft rejection and prolong cardiac allograft survival via the induction of proliferation and differentiation of CD4^＋ CD25^＋ Foxp3 ; Tregs.