Kim J M, Boone D L, Auyeung A, Tsang B K
Department of Obstetrics & Gynecology, University of Ottawa, Ottawa Civic Hospital Loeb Research Institute, Ontario, Canada.
Biol Reprod. 1998 May;58(5):1170-6. doi: 10.1095/biolreprod58.5.1170.
Apoptosis of granulosa cells is the cellular mechanism of ovarian follicular atresia, and cytokines have been implicated as potential atretogenic factors. We therefore investigated the possible role of the cytokine Fas ligand (FasL) and its receptor Fas in apoptosis during ovarian follicular atresia induced by gonadotropin withdrawal. Immature rats pretreated with eCG were injected 24 h later with an antiserum generated against eCG (antibody group) or preimmune rabbit serum (control), and ovaries were removed 1 and 24 h after treatment. The eCG antiserum caused a dose-dependent inhibition of the significant increase in ovarian weight observed between 24 and 48 h after eCG treatment. In situ detection of fragmented DNA in histological sections identified cell death in atretic but not healthy small and medium-sized antral follicles of the antibody group. Cell death was distributed in a scattered pattern throughout the granulosa cell layer of small atretic follicles but was localized primarily in granulosa cells lining the antral cavity of atretic medium antral follicles. Immunohistochemistry of adjacent histological sections revealed intense positive immunostaining for Fas and FasL in granulosa cells of atretic small and medium antral follicles in a pattern coincidental to the localization of cell death. Intense FasL staining was evident in the theca cells of healthy small antral follicles. An increase in low molecular weight DNA (DNA "ladders") indicative of apoptosis was evident in granulosa cells of the antibody group. Western analysis demonstrated increased levels of both Fas and FasL in the granulosa cells of the antibody group. These results demonstrate that both Fas and FasL are present in ovarian granulosa cells and that FasL may be the signal that induces granulosa cell apoptosis during atresia at the penultimate stage of ovarian follicular development.
颗粒细胞凋亡是卵巢卵泡闭锁的细胞机制，细胞因子被认为是潜在的闭锁诱导因子。因此，我们研究了细胞因子Fas配体（FasL）及其受体Fas在促性腺激素撤退诱导的卵巢卵泡闭锁过程中凋亡中的可能作用。用eCG预处理的未成熟大鼠在24小时后注射抗eCG产生的抗血清（抗体组）或免疫前兔血清（对照组），并在处理后1小时和24小时取出卵巢。eCG抗血清导致eCG处理后24至48小时观察到的卵巢重量显著增加呈剂量依赖性抑制。组织学切片中DNA片段的原位检测确定抗体组闭锁的中小窦状卵泡中有细胞死亡，但健康卵泡中没有。细胞死亡以散在模式分布在小闭锁卵泡的颗粒细胞层中，但主要局限于闭锁的中窦状卵泡腔内衬的颗粒细胞中。相邻组织学切片的免疫组织化学显示，闭锁的中小窦状卵泡的颗粒细胞中Fas和FasL有强烈的阳性免疫染色，其模式与细胞死亡的定位一致。在健康的小窦状卵泡的卵泡膜细胞中可见强烈的FasL染色。抗体组颗粒细胞中明显出现了指示凋亡的低分子量DNA增加（DNA“梯形条带”）。蛋白质印迹分析表明抗体组颗粒细胞中Fas和FasL水平均升高。这些结果表明Fas和FasL均存在于卵巢颗粒细胞中，并且FasL可能是在卵巢卵泡发育倒数第二阶段闭锁期间诱导颗粒细胞凋亡的信号。
