目的:探讨胞内转运途径受到抑制后,根尖牙乳头干细胞(stem cells from apical papilla, SCAP)表面CXC趋化因子受体4(CXC chemokine receptor 4, CXCR4)表达的变化,为了解SCAP迁移机制提供实验依据。方法:采用免疫荧光共染色方法和原位邻近连接技术(proximity ligation assay, PLA)检测SCAP胞内CXCR4与细胞胞内转运相关细胞器标记蛋白的共定位,检测指标包括早期胞内体标记蛋白Rab5、循环胞内体标记蛋白Rab11A、溶酶体标记蛋白Lamp1。分别采用80 μmol/L的内吞抑制剂Blebbistatin、80 μmol/L的内吞抑制剂Dyanasore对SCAP进行预处理1 h,流式细胞分析方法检测表面阳性表达CXCR4的SCAP所占百分比,使用单因素方差分析进行统计学分析。结果:免疫荧光共染色结果显示,CXCR4在SCAP胞内的表达位置与早期胞内体标记物Rab5、循环胞内体标记物Rab11A的表达位置重合,小部分与溶酶体标记物Lamp1的表达位置重合。PLA结果显示,CXCR4在SCAP胞内与Rab5、Rab11A、Lamp1均存在共定位。阴性对照组SCAP CXCR4阳性表达的细胞为 0.13%±0.10%, 经Blebbistatin、Dynasore抑制内吞后,表面CXCR4阳性表达的SCAP显著增多,分别为13.34%±1.31%、4.03%±0.92%,差异有统计学意义(F=161.762,P<0.001), 且Blebbistatin组多于Dynasore组,差异有统计学意义(P<0.001)。结论:采用内吞抑制剂抑制CXCR4的胞内转运途径,可使表面表达CXCR4的SCAP增多,提升了SCAP迁移的潜能。

Objective: To evaluate the change of cell surface CXC chemokine receptor 4 (CXCR4) expression of stem cells from apical papilla (SCAP) after the inhibition of endocytotic pathway, thus to provide experimental basis for the mechanism of SCAP migration. Methods: The immunofluorescence analysis was conducted to examine the co-expression of CXCR4 and endocytotic compartments, including early endosomes, recycling endosomes and lysosomes in SCAP. Several Rab proteins were applied as markers of organelles in the endocytotic pathway, including Rab5 for early endosomes, Rab11A for recycling endosomes, and Lamp1 for lysosomes. The co-localization of CXCR4 with these endodontic compartments was further observed by proximity ligation assay (PLA). SCAP was treated with two kinds of endocytotic inhibitors, Blebbistatin and Dynasore, at a concentration of 80 μmol/L, respectively. The conditioning time was 1 hour. Flow cytometry was carried out to evaluate the proportion of SCAP that expressed CXCR4 on cell surface. The data were analysed by analysis of variance (ANOVA). Results: The red staining of CXCR4 on immunofluorescence confocal microscopy predominantly overlapped with the green staining of Rab5 and Rab11A, and partly overlapped with Lamp1. It indicated that most CXCR4 molecules were located in early endosomes and recycling endosomes, and some were located in lysosomes. The PLA results revealed that the co-localizaiton of CXCR4 with endocytotic compartments could be observed in early endosomes, recycling endosomes and lysosomes. According to the results of flow cytometry, the proportion of SCAP that expressed CXCR4 on cell surface was as low as 0.13%±0.10%. After the inhibition of endocytosis by pretreating the cells with the following two inhibitors, Blebbistatin and Dynasore, the percentage of SCAP that positively expressed CXCR4 on cell surface was significantly increased to 13.34%±1.31% in Blebbistatin group and 4.03%±0.92% in Dynasore group (F=16.721, P<0.001). Moreover, the number of SCAP that expressed CXCR4 on cell surface in Blebbistatin group was significantly higher than that in Dynasore group (P<0.001). Conclusion: The inhibition of endocytotic pathway could increase the number of SCAP that expressed CXCR4 on cell surface, and provide potency for the migration of SCAP.