Follicular fluid meiosis-activating sterol (FF-MAS) is a small molecule compound found in follicular fluid, named for its ability to induce oocyte resumption of meiosis. Granulosa cells (GCs) within the follicle are typically located in a hypoxic environment under physiologic conditions due to limited vascular distribution. Previous research suggests that hypoxia-induced cell cycle arrest and apoptosis in GCs may be crucial triggering factors in porcine follicular atresia. However, the impact of FF-MAS on GCs within follicles has not been explored so far. In this study, we uncovered a novel role of FF-MAS in facilitating GC survival under hypoxic conditions by inhibiting STAT4 expression. We found that STAT4 expression was upregulated in porcine GCs exposed to 1% O2. Both gain and loss of function assays confirmed that STAT4 was required for cell apoptosis under hypoxia conditions, and that the GC apoptosis caused by hypoxia was markedly attenuated following FF-MAS treatment through inhibition of STAT4 expression. Correlation analysis in vivo revealed that GC apoptosis was associated with increased STAT4 expression, while the FF-MAS content in follicular fluid was negatively correlated with STAT4 mRNA levels and cell apoptosis. These findings elucidate a novel role of FF-MAS-mediated protection of GCs by inhibiting STAT4 expression under hypoxia, which might contribute to the mechanistic understanding of follicular development.

中文翻译：

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FF-MAS 通过抑制 STAT4 表达防止缺氧诱导的猪卵巢颗粒细胞凋亡

卵泡液减数分裂激活甾醇（FF-MAS）是卵泡液中发现的一种小分子化合物，因其能够诱导卵母细胞恢复减数分裂而得名。由于血管分布有限，卵泡内的颗粒细胞 (GC) 在生理条件下通常位于缺氧环境中。先前的研究表明，缺氧诱导的GC细胞周期停滞和细胞凋亡可能是猪卵泡闭锁的关键触发因素。然而，迄今为止，FF-MAS 对卵泡内 GC 的影响尚未被探索。在这项研究中，我们发现了 FF-MAS 通过抑制 STAT4 表达来促进缺氧条件下 GC 存活的新作用。我们发现暴露于 1% O2 的猪 GC 中 STAT4 表达上调。功能获得和丧失实验均证实，缺氧条件下细胞凋亡需要STAT4，并且通过抑制STAT4表达，FF-MAS处理后缺氧引起的GC细胞凋亡明显减弱。体内相关性分析显示，GC凋亡与STAT4表达增加相关，而卵泡液中FF-MAS含量与STAT4 mRNA水平和细胞凋亡呈负相关。这些发现阐明了 FF-MAS 介导的在缺氧条件下通过抑制 STAT4 表达来保护 GC 的新作用，这可能有助于了解卵泡发育的机制。