人胎儿卵泡形成过程中卵细胞的凋亡

Study on the oocyte apoptosis during human fetal folliculogenesis

目的:研究人胎儿卵泡形成过程中卵细胞凋亡及其意义。方法:收集13例水囊引产胎儿(20～38孕周)的卵巢组织,其中孕中期(20～28孕周)7例、孕晚期(29-38孕周)6例。利用电镜和末端标记法(TUNEL)观察胎儿卵泡形成过程中卵细胞凋亡的发生。结果:部分卵细胞超微结构改变呈现细胞凋亡的特征:早期表现主要有染色质凝集趋边、核周间隙扩张;进一步发展出现胞浆空泡化、胞浆内凋亡小体和自噬体形成、线粒体嵴脱失等。另外,凋亡早期卵细胞内线粒体比正常卵细胞明显减少。末端标记见到阳性细胞(凋亡卵细胞),孕中期卵细胞凋亡指数(9.8±1.2)％明显高于孕晚期凋亡指数(3.1±1.0)％,P<0.01。结论:人胎儿卵泡形成过程中卵细胞发生凋亡,由此导致生殖细胞大量丢失。

Aim:To investigate whether the ooeyte apoptosis exists and its relationship with the oocyte loss during human fetal folliculogenesis. Methods: Ovarian tissues from 13 fetuses(aged 20 - 38 weeks) were obtained after induction by insertion of water sac, including 7 fetuses of midpregnancy ( aged 20 - 28 weeks) and 6 fetuses of late pregnancy ( aged 29 -38 weeks). Electron microscope and TUNEL method were used to examine the occurrence of oocytes apoptosis during human fetal folliculogenesis. Results: Ultrualstructurally, a apoptotic process was found in some oocytes. Early degeneration was characterized by chromatin margination and condensation,and dilation of perinuclear space. Subsequently, cytoplasmic structures were also involved, including cytoplasmic vacuolization, formation of apoptosis body and autophagosomes, and loss of mitochondrial cristae. Additionally, mitochondrial number in early apoptotic oocyte was less than that in the normal. TUNNEL positive oocytes were also observed, and apoptotic index of oocytes of midpregnancy (9. 8±1.2)% was higher than that of late pregnancy (3.1±1.0)%, P < 0. 01. Conclusion: The oocyte apoptotosis occurs, and consequently it may cause germ cell loss during human fetal folliculogenesis.