https://www.fertstert.org/article/S0015-0282(09)04050-3/pdf

The role of autophagy in follicular development and atresia in rat granulosa cells.

More than half of the primordial follicles that are formed by Day 6 of postnatal life in the mouse will be eliminated from the ovary by the time of puberty. Apoptosis, a form of programmed cell death, is one mechanism by which these follicles could be actively lost. To investigate whether apoptosis is responsible for the loss of primordial follicles, follicular atresia was examined during the prepubertal period, when follicles die and are cleared from the ovary at an extremely high rate. Four hallmarks of classical apoptosis were measured in follicles present in prepubertal ovaries. The primordial follicle cohort was not positively associated with nuclear condensation or cell shrinkage, activation of caspase 3, cleavage of poly(ADP ribose) polymerase 1 (PARP1), or fragmentation of DNA. These data are consistent with a nonapoptotic pathway that is responsible for small follicle death.

/pdf/prepubertal-primordial-follicle-loss-in-mice-is-not-due-to-149je9m8i8.pdf

Prepubertal Primordial Follicle Loss in Mice Is Not Due to Classical Apoptotic Pathways

The LOX-1 receptor, identified on endothelial cells, mediates the uptake of oxidized low-density lipoprotein (oxLDL). The oxLDL-dependent LOX-1 activation causes endothelial cell apoptosis. We here investigated the presence of LOX-1 in granulosa cells from patients under in vitro fertilization therapy. We were interested in the oxLDL-dependent LOX-1 receptor biology, in particular in the induction of apoptosis. In the human ovary, LOX-1 was localized in regressing antral follicles. In granulosa cell cultures, oxLDL-induced mRNA expression of LOX-1 in a time- and dose-dependent manner. The LOX-1 inhibitors (anti-LOX-1 antibody and kappa-carrageenan) abrogated the up-regulation of LOX-1. The oxLDL (100 microg/ml) treatment caused the autophagy form of programmed cell death: 1) reorganization of the actin cytoskeleton at the 6-h time point; 2) uptake of YO-PRO, a marker for the early step of programmed cell death, before propidium iodide staining to signify necrosis; 3) absence of apoptotic bodies and cleaved caspase-3; 4) abundant vacuole formation at the ultrastructural level; and 5) decrease of the autophagosome marker protein MAP LC3-I at the 6-h time point indicative of autophagosome formation. We conclude that follicular atresia is not under the exclusive control of apoptosis. The LOX-1-dependent autophagy represents an alternate form of programmed cell death. Obese women with high blood levels of oxLDL may display an increased rate of autophagic granulosa cell death.

Lectin-like oxidized low-density lipoprotein receptor-1-mediated autophagy in human granulosa cells as an alternative of programmed cell death.

Ovarian follicular atresia is mediated by heterophagy, autophagy, and apoptosis in Prochilodus argenteus and Leporinus taeniatus (Teleostei: Characiformes).

Autophagy is an important cellular process that serves as a companion pathway to the ubiquitin-proteasome system to degrade long-lived proteins and organelles to maintain cell homeostasis. Although initially characterized in yeast, autophagy is being realized as an important regulator of development and disease in mammals. Beclin1 (Becn1) is a putative tumor suppressor gene that has been shown to undergo a loss of heterozygosity in 40–75% of human breast, ovarian, and prostate cancers. Because Becn1 is a key regulator of autophagy, we sought to investigate its role in female reproduction by using a conditional knockout approach in mice. We find that pregnant females lacking Becn1 in the ovarian granulosa cell population have a defect in progesterone production and a subsequent preterm labor phenotype. Luteal cells in this model exhibit defective autophagy and a failure to accumulate lipid droplets needed for steroidogenesis. Collectively, we show that Becn1 provides essential functions in the ovary that are essential for mammalian reproduction.

https://www.pnas.org/content/pnas/111/40/E4194.full.pdf

Beclin-1 deficiency in the murine ovary results in the reduction of progesterone production to promote preterm labor.

The structure of follicular layer of growing and atretic follicles in the ovary of the domestic goose, was studied by electron microscopy In small follicles, the wall is lined with a narrow layer of tightly packed small, cuboidal cells separated from the thecal tissue by the basal lamina During growth, they transform into tall, columnar cells arranged in a single row The cells display several peculiar ultrastructural features First, annulate lamellae are commonly observed Second, cytoplasmic dense-cored granules accumulate in close association with fenestrated cisternae and networks of tubuli derived from the RER They consist of spheres and strands of amorphous substance of unknown origin Third, the cells contain many transosomes, a unique organelle of the avian follicle cell consisting of a dense plaque associated with ribosome-like particles The mature forms of transosomes are located at the tips of lateral and apical cell projections, while bodies thought to be their precursors, are found in the apical cytoplasm In follicles larger than 8 mm in diameter, most of the transosomes and their precursors have disappeared Follicular atresia occurs in all of the size-classes of follicles investigated A loss of transosomes (in follicles up to 8 mm in diameter) and an accumulation of lipid droplets are the first atretic events detectable by electron microscopy Morphologic features, including deep nuclear indentations, accumulation of lipid droplets frequently encireled by membrane whorls, dilation and disintegration of RER cisterns, swelling of mitochondria and accumulation of dense irregular masses of unknown origin in the cytoplasm, are taken as evidence for advanced degradation We conclude that necrosis is the dominant type of cell death of the follicular cells during atresia However, a small fraction of cells, characterized by dark condensed cytoplasm, seems to die by apoptosis

Victoria Forgó

Papers

The fine structure of the follicular cells in growing and atretic ovarian follicles of the domestic goose.