孕激素诱导cyclin G1在小鼠子宫内膜上皮细胞的表达及其对细胞增殖的影响

The progesterone-induced expression of cyclin G1 and its effect on the proliferation of mouse uterine epithelial cells

本文在体外培养条件下研究卵巢激素诱导小鼠子宫内膜上皮细胞cyclin G1的表达及细胞增殖和细胞周期进程的变化,以探讨孕激素依赖的细胞周期调控因子cyclin G1对子宫内膜上皮细胞增殖的负调控作用。原代培养小鼠子宫内膜上皮细胞,待其生长汇合后分为4组:对照组(C组)、雌激素组(E组)、孕激素组(P组)、雌、孕激素共同作用组(EP组)。加入相应激素作用24h后,用细胞免疫化学方法检测各组细胞cyclin G1的表达水平;四甲基偶氮唑蓝(MTT)比色法检测各组细胞活力,间接观察子宫内膜上皮细胞的增殖情况;用流式细胞仪检测分布在细胞周期各时相的子宫内膜上皮细胞所占百分数。细胞免疫化学结果显示,cyclin G1在C组和E组子宫内膜上皮细胞上无明显表达,而在P组和EP组子宫内膜上皮细胞中表达明显,且定位于细胞核内。MTT法结果显示,与C组相比,E组细胞活力明显增高,而P组和EP组的细胞活力均明显下降,表明雌激素能促进子宫内膜上皮细胞增殖,而孕激素则具有抑制子宫内膜上皮细胞增殖的作用。流式细胞术检测显示,与C组相比,E组中处于S期的子宫内膜上皮细胞百分数增多;P组与EP组中处于S期的子宫内膜上皮细胞百分数明显减少,而处于G1期的细胞百分数和G2/M期的细胞百分数则明显增加。上述结果提示,孕激素依赖的cyclin G1可能通过阻滞细胞周期进程来参与孕激素对子宫内膜上皮细胞增殖的负调控作用。

The aim of the present study is to investigate the effect of progesterone-induced expression of cyclin G1 on the proliferation of endometrial epithelial cells. To obtain mouse endometrial epithelial cells, the uteri were isolated from ovariectomized mice which were injected subcutaneously with 100 ng estradiol per day for two days. Then the uteri were digested by dispase and pancreatin respectively. Endometrial epithelial cells were cultured in DMEM/F12 containing 6% fetal bovine serum, and divided into four groups when they grew to confluence. Each of the groups was treated as follows： Group E was treated with 0.01 μmol/L estradiol only, group P was treated with 1 μmol/L progesterone, group EP was treated with both 0.01 μmol/L estradiol and 1 μmol/L progesterone, and group C was treated with 0.01% DMSO for control. Immunocytochemistry was used to examine the expression of cyclin G1 protein. MTT assay was used to evaluate metabolic activity of cells. Flow cytometry was used to check the number of cells distributing in each phase of the cell cycle. The result of immunocytochemistry showed that there was no expression of cyclin G1 protein in group C and group E, while cyclin G1 was obviously expressed in group P and group EP and localized in nucleus. In the MTT assay, compared with group C, the viability of group E significantly increased, while that of both group P and group EP decreased significantly. The results of flow cytometry were in accordance with those of MTT, which showed that compared with group C, group E had a higher proportion of cells in S phase, while group P, as well as group EP had a lower proportion of cells in S phase but a higher proportion in G1 phase and G2/Mphase. These results indicate that progesterone could induce cyclin G1 expression in the primary culture of mouse endometrial epithelial cells, meanwhile inhibit the proliferation of cells and block the cell cycle progression. Thus, progesterone-induced expression of cyclin G1 is probably a negative factor in regulating cell cycle, which is involved in the inhibitory effect of progesterone on the proliferation of endometrial epithelial cells.