Endocrine Abstracts

Background: The reserve pool of primordial follicles (PMF) is finely regulated by molecules implicated in follicular growth or PMF survival. Anti-Müllerian Hormone (AMH), produced by granulosa cells of growing follicles, is known for its inhibitory role in the initiation of PMF growth. We observed in a recent in vivo study that injection of AMH into mice seemed to induce an activation of autophagy, a cytoplasmic lysosomal-dependent degradation system, which is important for starvation adaptation and cellular quality control. Furthermore, we observed an activation of the transcription factor FOXO3a by AMH, which is also known to regulate autophagy. Many studies highlighted the key role of autophagy in the ovary at different stages of folliculogenesis and particularly in PMF survival. The objective of our study was to understand how AMH stimulates autophagy and in particular what is the role of the transcription factor FOXO3a which is involved in the maintenance of PMF in quiescence but also in the regulation of autophagy.

Methods: We used an in vitro approach on organotypic cultures of prepubertal mouse ovaries, treated or not with AMH. Autophagy was monitored by immunofluorescence and western-blot analysis of LC3, a specific marker of autophagosomes. The phosphorylation status of FOXO3a was analyzed by Western blot. The expression of genes involved in autophagy was quantified by RT-qPCR.

Results: We showed that autophagosome biosynthesis and autophagic flux are increased in AMH-treated ovaries. AMH also induces a FOXO3a dephosphorylation which is translocated to the nucleus where it exerts its transcriptional activity. We observed that the transcription of FOXO3a target genes involved in autophagy (Atg16l1, Gabarapl2, Wipi2, Atg2a, Ulk1, Zfyve1, Atg5) is significantly increased in AMH treated ovaries.

Discussion: This in vitro approach shows that AMH is able to stimulate autophagy in mouse ovaries by increasing the expression of a number of FOXO3a target genes involved in this process. This is a completely new role for this hormone which protects the pool of primordial follicles by inhibiting their growth but also by inducing autophagy to allow them to survive.