Evidence of the activation of unfolded protein response in granulosa and cumulus cells during follicular growth and maturation

卵泡的生长和成熟是由卵巢内因子调节的，尽管其机制尚不清楚。近年来，未折叠蛋白反应（UPR）在维持体内平衡中发挥着重要作用。在本研究中，为了检验颗粒细胞（GC）和积云细胞（CC）中的UPR是否参与卵泡生长和成熟过程，我们检测了卵泡生长过程中GC中UPR的存在以及CC中UPR表达与卵母细胞成熟的关系。在小鼠生长卵泡GC中，有X-box结合蛋白-1 （XBP1(S)）和热休克70kDa蛋白5 （HSPA5）剪接形式的uprr相关基因表达，其表达具有分期依赖性。此外，XBP1(S) mRNA在封闭人成熟卵母细胞的CC中表达量比封闭未成熟卵母细胞的CC高2倍。这些发现表明，在卵泡生长过程中，GC中UPR被激活，在卵泡生长和成熟中发挥作用。

Follicular growth and maturation are known to be regulated by intra-ovarian factors, although the mechanisms are still to be known. Recently, unfolded protain response (UPR) has been known to have essential roles in keeping homeostasis. In the present study, to test whether UPR in granulosa cells (GC) and cumulus cells (CC) is involved in the process of follicular growth and maturation, we examined the presence of UPR in GC during follicular growth and the association between UPR expression in CC and oocyte maturity. UPR-related genes, spliced form of X-box binding protein -1 (XBP1(S)) and heat shock 70kDa protein 5 (HSPA5), were expressed in mice GC of growing follicels, and their expression is stage-dependent. In addition, the expression levels of XBP1(S) mRNA in CC enclosing human mature oocytes were 2-fold higher than those in CC enclosing immature ooytes. These findings suggest that UPR is activated in GC during follicular growth, playing roles in follicular growth and maturation.