Mammalian Hyaluronidase Induces Ovarian Granulosa Cell Apoptosis and Is Involved in Follicular Atresia

Abstract

During ovarian folliculogenesis, the vast majority of follicles will undergo atresia by apoptosis, allowing a few dominant follicles to mature. Mammalian hyaluronidases comprise a family of six to seven enzymes sharing the same catalytic domain responsible for hyaluronan hydrolysis. Interestingly, some of these enzymes have been shown to induce apoptosis. In the ovary, expression of three hyaluronidases (Hyal-1, Hyal-2, and Hyal-3) has been documented. However, their precise cellular localization and role in ovarian regulation have not yet been defined. We herein investigated the possible involvement of these enzymes in ovarian atresia. First, we established a mouse model for ovarian atresia (gonadotropin withdrawal by anti-equine chorionic gonadotropin treatment) and showed that the mRNA levels of Hyal-1, Hyal-2, and Hyal-3 were significantly increased in apoptotic granulosa cells as well as in atretic follicles. Second, using ovaries of normally cycling mice, we demonstrated the correlation of Hyal-1 mRNA and protein expression with cleavage of caspase-3. In addition, we showed that expression of all three hyaluronidases induced apoptosis in transfected granulosa cells. Significantly, the induction of apoptosis by hyaluronidases was independent of catalytic activity, because enzymatically inactive Hyal-1 mutant (D157A/E159A) was as efficient as the wild-type enzyme in apoptosis induction. The activation of the extrinsic apoptotic signaling pathway was involved in this induction, because increased levels of cleaved caspase-8, caspase-3, and poly-ADP-ribose polymerase (PARP) were observed upon hyaluronidase ectopic expression. Our present findings provide a better understanding of the role of hyaluronidases in ovarian functions, showing for the first time their involvement in follicular atresia.

Expression of Hyaluronan Synthase 1 and Distribution of Hyaluronan During Follicular Atresia in Pig Ovaries1

“…In mouse granulosa cells, all three enzymes were capable of inducing cell apoptosis; however, the enzymatic activity of hyaluroglucosaminidase may not be relevant to the induction of apoptosis. Indeed, enzymatically inactive mutant HYAL1 induced the same level of apoptosis as the wild-type enzyme in cultured granulosa cells [47]. In the present study, the HA concentration in the pFFs was increased significantly at stage III.…”

“…It has recently been reported that the expression of hyaluroglucosaminidase (Hyal; Hyal1, Hyal2, and Hyal3) was correlated to increased granulosa cell apoptosis and follicular atresia in mouse ovaries [47]. In mouse granulosa cells, all three enzymes were capable of inducing cell apoptosis; however, the enzymatic activity of hyaluroglucosaminidase may not be relevant to the induction of apoptosis.…”

Hyaluronan synthases (HAS1-3) and hyaluronidases (HYAL1-2) in the accumulation of hyaluronan in endometrioid endometrial carcinoma

“…Furthermore, the high molecular mass hyaluronan that occupies cell surface CD44 receptors maintains p-Akt and PI3K dependent signals that prevent cancer cell apoptosis, while hyaluronidase, and the oligosaccharides created by hyaluronidase, block these cell survival signals [36]. It has also been recently demonstrated that ectopic expression of all three different somatic hyaluronidases ( HYAL1, HYAL2 and HYAL3 ) induce granulosa cell apoptosis [37]. …”

L’atrésie folliculaire : ses facteurs régulateurs peuvent-ils être marqueurs de la qualité de l’ovocyte en AMP ?

“…Dans l'ovaire, trois hyaluronidases (Hyal-1, Hyal-2 et Hyal-3) sont exprimé es. Leurs niveaux en ARNm sont significativement augmenté s dans les cellules apoptotiques de la granulosa et, donc, dans les follicules atré tiques de souris [21]. Or, les traitements de stimulation utilisé s en AMP affectent la concentration d'acide hyaluronique dans le liquide folliculaire humain [22].…”