地塞米松诱导骨髓来源抑制细胞对同种异系小鼠皮肤移植排斥反应的作用

Effects of myeloid-derived suppressor cells induced by dexamethasone on rejection of skin transplantation of mice

目的探讨地塞米松诱导骨髓来源抑制细胞(MDSCs)在同种异系小鼠皮肤移植模型中的表达及免疫负调节作用。方法以雌性BALB/c小鼠皮肤为供体,雄性C57BL/6小鼠为受体,建立同种异系小鼠尾—背皮肤移植模型(n=40)。受体小鼠随机分为实验组和对照组(n=20),实验组每日地塞米松磷酸盐溶液5 mg/kg腹腔注射,对照组等体积生理盐水腹腔注射,观察小鼠移植皮肤排斥反应情况,确定移植皮肤排斥时间;术后第7日切取小鼠移植皮肤行病理学检查;术后第9日处死部分小鼠,获取脾脏及移植皮肤引流淋巴结,行流式细胞术检测。结果实验组小鼠移植皮肤的中位生存期为(24±3.062)d,显著长于对照组小鼠的(9±0.816)d(P<0.05)。石蜡切片苏木精-伊红(HE)染色可见,与对照组比较,实验组移植皮肤的排斥反应显著减轻。流式细胞术检测结果显示:在脾脏组织,与对照组比较,实验组CD11b+GR1+细胞比例明显增高(P<0.05),肿瘤坏死因子-α(TNF-α)表达下调(P<0.05)、白介素-10(IL-10)表达上调(P<0.05),并伴有趋化因子受体CXCR2和黏附分子CD44、CD62L表达增加(P<0.05);在引流淋巴结,与对照组比较,实验组CD11b+GR1+细胞比例显著增高(P<0.05),而CD4+T细胞比例及γ干扰素(IFN-γ)表达显著减少(P<0.05)。结论地塞米松可能通过诱导产生MDSCs,使其向移植物局部迁移并作用于CD4+T细胞,抑制其功能,从而达到减轻移植物排斥反应及延长移植物生存的效应。

Objective To investigate the expression and immunoregulation effect of myeloid-derived suppressor cells （MDSCs） induced by dexamethasone in the skin transplantation model of mice. Methods The male C57BL/6 mice were receptors and the female BALB/c mice were donors. The tailback skin transplantation model of mice was then established （n=40）. Donor mice were randomly divided into the experiment group and control group （n=20）. Mice of the experiment group received an intraperitoneal injection of dexamethasone 5 mg/kg per day while mice of the control group received an equal volume of saline. The rejection of skin allograft was observed and the rejection time was determined. The transplanted skin was excised for pathological examination on the seventh day after operations. Some mice were sacrificed on the ninth day after operations and their spleens and draining lymph nodes of transplanted skin were obtained and detected by the flow cytometry. Results The median survival time of allograft skin of the experiment group was （24±3.062） days, significantly longer than （9±0.816） days of the control group （P〈0.05）. HE stained paraffin sections showed that the rejection of skin graft of the experiment group was significantly less serious than that of the control group. The results of the flow cytometry indicated that in spleen tissues of the experiment group, the proportion of CD11b＋GR1＋ cells was significantly higher than that of the control group, the expression of TNF-α was down-regulated （P〈0.05）, the expression of IL-10 was up-regulated （P〈0.05）, and expressions of chemotactic factor receptor CXCR2 and adhesion molecules CD44 and CD62L were increased （P〈0.05）. In the draining lymph nodes of the experiment group, the proportion of CD11b＋GR1＋ cells was significantly higher than that of the control group （P〈0.05）, while the proportion of CD4＋T cells and the expression of IFN-γ were significantly decreased （P〈0.05）. Conclusion Dexamethasone may induce the MDSCs and promote MDSCs migrate to the allograft region. By inhibiting the function of CD4＋T cells, MDSCs can relieve the graft rejection and extend the survival time of grafts.