Apoptosis and autophagy of follicular granulosa cells play an important regulatory role in the process of ovarian follicular atresia in animals. Recent studies have shown that ferroptosis and pyroptosis are also involved in the process of ovarian follicular atresia. Ferroptosis is a form of cell death caused by iron-dependent lipid peroxidation and reactive oxygen species (ROS) accumulation. Studies have confirmed that autophagy- and apoptosis-mediated follicular atresia also have typical characteristics of ferroptosis. Pyroptosis is a pro-inflammatory cell death dependent on Gasdermin protein, which can regulate ovarian reproductive performance by regulating follicular granulosa cells. This article reviews the roles and mechanisms of several types of programmed cell death independently or interactively regulating follicular atresia, in order to expand the theoretical research on follicular atresia mechanism and provide the theoretical reference for the mechanism of programmed cell death-induced follicular atresia.
Female ; Animals ; Follicular Atresia ; Apoptosis ; Cell Death ; Ferroptosis ; Pyroptosis

Extracellular vesicles (EVs) are membrane-bound particles actively released by cells. In prokaryotes and eukaryotes, EVs are effective bridges for communication between cells. EVs carry biological macromolecules, including proteins, lipids and nucleic acid, which affects different physiological functions of parent cells and recipient cells. Among them, the microRNA carried by EVs is the most reported and plays an important role in physiological function of organisms. During the development of follicles, only a few follicles can fully develop and ovulate, whereas most of them undergo atresia at different stages of development. In the whole process of follicular development, the changes at each stage and the regulation mechanism of follicular atresia are not completely understood. In this paper, we introduced the types, characteristics, isolation methods and uses of EVs, and emphasized how microRNA carried by EVs in follicular fluid regulated follicular atresia from the aspects of different cytokines and hormones. Additionally, the application prospect of microRNA carried by EVs in follicular fluid in reproductive regulation and reproductive disease diagnosis was discussed. This paper is significant for studying the regulation of follicular development and the effective utilization of oocytes.
Animals ; Extracellular Vesicles/metabolism* ; Female ; Follicular Atresia ; Follicular Fluid ; MicroRNAs/metabolism* ; Oocytes

Hormesis is the generally-favorable biological responses to low exposures to toxins and other stressors. Radiation hormesis is the theory that ionizing radiation is benign at low levels of exposure, and that doses at the level of natural background radiation can be beneficial. The purpose of this study is to reveal the hormetic effect of low-dose radiation of ionizing radiation on the ovarian follicles of 4-week old female mice. Mice were grouped into control group, 2 cGy irradiated group, 2 cGy and 2 Gy irradiated group (2 cGY pre-exposure group), and 2 Gy irradited group. Mice were sacrificed by cervical dislocation 24 hours after irradiation, removed ovaries, fixed in neutral formaldehyde solution for 24 hours, embedded with paraffin, stained with hematoxylin and eosin and TUNEL immunohistochemically, and observed light microscopically the atretic follicles and normal follicles in various follicular developmental stages. In this experiment, the ratrio of atretic follicles to entire follicles in an ovary increased significantly in 2 Gyirradiated group compared with 2 cGY pre-exposure group, and the ratio of normal follicles to the entire follicles in an ovary in all the developmental stages were increased significantly in the 2 cGY pre-exposure group compared with 2 Gy-irradiated group. These results mean that low-dose radiation pre-exposure can induce the hormetic effect in the developing ovarian follicle.
Animals ; Background Radiation ; Dislocations ; Eosine Yellowish-(YS) ; Female ; Follicular Atresia ; Formaldehyde ; Hematoxylin ; Hormesis ; Humans ; In Situ Nick-End Labeling ; Mice ; Ovarian Follicle* ; Ovary ; Paraffin ; Radiation, Ionizing ; Rats*

OBJECTIVE: The purposes of the present study were to investigate the effect of gamma-radiation on the expression of inhibin-alpha proteins and genes for inhibin alpha, betaA, and betain the ovary. METHODS: Immature mice were whole-body gamma-irradiated with 25% of a lethal dose. At time 0, 3, 6, 12, and 24 hours after the irradiation,the ovaries were collected and used for immunohistochemistry for inhibin-alpha, and RT_PCR for inhibin-alpha, betaA, and betaB. RESULTS: The expression of the immunoreactive inhibins-alpha was maintained at 12 hours post-irradiation and reduced thereafter. The expression of inhibin-alpha mRNA was significantly increased with the time after the irradiation. However there were no significant changes in the expression of betaA and betaB mRNAs. CONCLUSION: It might be thought that inhibin acts as one of the regulatory factors in the gamma-radiation-induced follicular atresia in mice
Animals ; Female ; Follicular Atresia ; Immunohistochemistry ; Inhibins* ; Mice* ; Ovary* ; RNA, Messenger

OBJECTIVE: In the ovary apoptosis eliminates granulosa cells (GC) during follicle atresia. While we identified many cell death regulatory molecules not yet characterized in the ovary, of particular interest were members of the Bcl-2 family which contain only the Bcl-2 homology (BH)-3 domain. The objectives of this study was to investigate and compare the expression patterns of BH3-only Bcl-2 family members in various organs and evaluate their function in ovarian granulosa cells. METHODS: Total RNA was extracted from GC, ovaries, uteri, hearts (low rate of cell turnover) and livers (high rate of cell turnover) of prepubertal female mice. BH3-only Bcl-2 family members were cloned to make riboprobe. The expression patterns in the tissues evaluated by Northern blot analysis. Nix mRNA expression in ovarian granulosa cells after gonadotropin treatment also compared by Northern blot analysis. RESULTS: Bad, Bid, Bim, Bmf, Map-1 and Nix were expressed in granulosa cells. Nix was most abundantly expressed in GC. In contrast, Blk was expressed in the ovary, liver, heart and uterus, but not in GC. Bmf, a sensor or microfilament disassembly, was expressed in GC, ovary and uterus, with limited to no expression in non-reproductive tissues. Nix mRNA expression was not regulated by gonadotropin after 42 hour. CONCLUSION: These studies will help to complete a molecular blueprint of the regulatory network that controls GC death during follicular atresia. In addition, these data, which show a tissue/cell-selective profile of BH3-only expression, may also explain the known variation in the in vivo apoptotic response of different tissues/cells to generic stimuli that should be globally lethal.
Actin Cytoskeleton ; Animals ; Apoptosis ; Blotting, Northern ; Cell Death ; Clone Cells ; Female ; Follicular Atresia ; Gonadotropins* ; Granulosa Cells* ; Heart ; Humans ; Liver ; Mice* ; Ovary* ; RNA ; RNA, Messenger ; Uterus

OBJECTIVE: Ovarian follicular atresia is initiated from ovarian granulosa cell apoptosis and macrophages exert their effects directly and/or indirectly on follicular atresia by phagocytosis of apoptotic bodies and secretion of various cytokines. In spite of the abundant data on ovarian macrophages, the presence of these cells within the follicles (i.e., among granulosa cells) remains controversial and the elimination methods of apoptotic bodies of atretic follicles, and the time and methods of penetration of macrophages into the follicles are not known completely. The aim of the present study is to demonstrate the presence of macrophage within the ovary as related to follicular atresia and the process of elimination of apoptotic granulosa cells by light and electron microscopy. METHODS: Using rat ovaries, immunohistochemical studies with rat macrophage monoclonal antibody ED1 for macrophages, and light and transmission electron microscopic observations were performed. RESULTS: In the rat, follicular atresia was initiated by the granulosa cell apoptosis which occured randomly within the all granulosa layers. Macrophages were observed within normal follicles, in antrum, granulosa and theca cell layers of atretic follicels, in interstium and in corpus luteum. Ultrastructurally, apoptotic granulosa cells showed characteristics, pyknotic nucleus and apoptotic body formation. Apoptotic bodies were eliminated by intact neighboring granulosa cells and macrophages. Intact granulosa cells ingested apoptotic bodies transiently, soon after they fell into the apoptosis. Finally, apoptotic bodies and degenerating oocytes were phagocytosed by macrophages. Macrophages entered the ovarian follicle at the time of initiation of granulosa cell apoptosis, and migrated with the progression of apoptosis. By elimination of theca cells, macrophages contributed the completion of follicular atresia. CONCLUSION: This study demonstrates both intact neighboring granulosa cells and macrophages in the elimination of apoptotic bodies in atretic follicles of the rat ovary. Macrophages are present within normal follicles, in atretic follicles such as antrum, granulosa and theca cell layers and in corpus luteum but are in different appearances according to their location in ovary. A number of macrophages appearing in atretic follicles and in corpora lutea suggest a role for macrophages in follicular atresia and corpus luteum differentiation. The function of macrophage according to their location in follicular development should be further studied.
Animals ; Apoptosis ; Corpus Luteum ; Cytokines ; Female ; Follicular Atresia* ; Granulosa Cells ; Macrophages* ; Microscopy, Electron ; Oocytes ; Ovarian Follicle* ; Ovary ; Phagocytosis ; Rats* ; Theca Cells

Tumor necrosis factor alpha (TNFalpha) is an intraovarian cytokine that may play a role in ovarian development and function. Identification of ovarian TNFalpha receptors provides support for establishing a role of TNFalpha in ovarian development and function. TNFalpha exerts its effects by binding to either TNF receptor 1 or 2 (TNFR1 or TNFR2). When TNFalpha binds with TNFR2, expression of survival genes is up-regulated, resulting in proliferation of granulosa cells. In the present study, the authors identified the changes in localization of TNFalpha and the expression of TNFR2 in granulosa cells during follicular atresia in rat ovaries. In healthy follicles, intense signals for TNFalpha and TNFR2 were found in the outer surface of the granulosa layer, where many proliferating cells and no apoptotic cells were observed. In atretic follicles, decreased expression of TNFalpha and TNFR2 was observed in the granulosa layer, where many apoptotic cells were seen. These findings suggested that TNFalpha acts as a survival factor in granulosa cells during follicular atresia in rat ovaries.
Animals ; Apoptosis ; Female ; Follicular Atresia ; Granulosa Cells ; Immunohistochemistry* ; Ovarian Follicle ; Ovary ; Rats* ; Receptors, Tumor Necrosis Factor ; Receptors, Tumor Necrosis Factor, Type II* ; Tumor Necrosis Factor-alpha*

OBJECTIVE: It is well known that X-ray induces follicular atresia, but the exact mechanism of atresia is not still unveiled completely. In addition, the role of macrophage related with clean-up the dead granulosa cells and other functions within the ovarian follicle is emphasized recently. The aim of this study is to assess the radiation-induced morphological changes of ovarian follicles and follicular macrophages. METHODS: 8 Gy X-ray irradiated on the 3-week old rats (Sprague-Dawley strain), sacrificed at 6, 12, and 24 hours after irradiation, and performed morphological studies with light and transmission electron microscopy, TUNEL, and macrophage immunohistochemistry. RESULTS: Follicular atresia increased significantly (p<0.01) at 6 hours after X-irradiation, and it was decreased significantly (p<0.01) at 12 and 24 hours after irradiation. X-ray induced chromatin condensation in the nucleus and nuclear fragmentation of granulosa cells, which were the typical features of apoptosis. Apoptotic granulosa cells were phagocytosed by the neighboring normal granulosa cells and the macrophages. During atresia of follicles, radioresistant granulosa cells were found in some follicles, which showed similar features morphologically with the granulosa cells of normal follicles. Macrophages were found both within the antrum and at the follicular granulosa layer. CONCLUSION: X-radiation induced follicular atresia by means of granulosa cell apoptosis, and radioresistant granulosa cells which have similar features morphologically with the granulosa cells of normal follicles were observed in some follicles. And the macrophages which phagocytose the apoptotic granulosa cells were located within the follicular antrum and at the follicular granulosa layer.
Animals ; Apoptosis ; Chromatin ; Female ; Follicular Atresia* ; Granulosa Cells ; Immunohistochemistry ; In Situ Nick-End Labeling ; Macrophages* ; Microscopy, Electron, Transmission ; Ovarian Follicle ; Radiation, Ionizing ; Rats

Apoptosis of granulosa cells leads follicular atresia and macrophages have an important role during the apoptotic process. However, the propagation of apoptosis within the follicle, the ways of elimination of apoptotic bodies and degenerated oocyte, and the completion of follicular atresia are still controversial and unidentified clearly. Using adult porcine (Yorkshire-breed) ovary, in this morphological study, transmission electron microscopic observation and immunohistochemical study with pig macrophage monoclonal antibody 4E9 were performed. In light microscopy, the follicular atresia initiated with apoptosis of granulosa cells, followed by degeneration of oocyte and apoptosis of theca interna cells. Apoptosis occured in random fashion among the granulosa cells and propagated multidirectionally, and finally to the granulosa cells surrounding zona pellucida of degenerating oocyte. Pyknosis of granulosa cells was the first sign of apoptosis. In immunohistochemistry, macrophages were found only in the granulosa layer at the stage of beginning of apoptosis. With progression of apoptosis, they were proliferated greatly in number enough to eliminate all the apoptotic bodies, and found within the follicular antrum. In advanced stage of atresia, macrophages surrounded the zona pellucida of degenerating oocyte, and found also in the theca interna. In transmission electron microscopy, phagocytic granulosa cells maintained characteristic gap junctions with neighboring granulosa cells and contained several apoptotic bodies and lipid droplets within their cytoplasm. Macrophages kept many apoptotic bodies, vacuoles and autophagosomes in their cytoplasm. Apoptotic granulosa cells were ingested by intact granulosa cells and macrophages initially, but lately, all the apoptotic granulosa cells and degenerated oocyte were eliminated by macrophages. Ovarian follicular atresia completed with phagocytosis of apoptotic theca interna cells by macrophages, and the remnants of the atretic follicle became ovarian stroma. It is well known that macrophages may play an important role during follicular atresia, such as elimination of apoptotic granulosa cells, theca interna cells and degenerated oocytes, but, the valid action mechanisms of macrophages on the initiation of granulosa cell apoptosis and on the completion of atresia through the secretion of paracrine factors and autocrine factors still unclear.
Adult ; Apoptosis ; Cytoplasm ; Female ; Follicular Atresia* ; Gap Junctions ; Granulosa Cells ; Humans ; Immunohistochemistry ; Macrophages* ; Microscopy ; Microscopy, Electron, Transmission ; Oocytes ; Ovarian Follicle ; Ovary* ; Phagocytosis ; Theca Cells ; Vacuoles ; Zona Pellucida

OBJECTIVE: To investigate the expression of apoptosis related proteins and apoptotic cells on the human ovarian follicles. MATERIALS AND METHODS: Thirty five Formalin-fixed paraffin-embedded human ovarian tissue blocks were selected from the surgical pathology files of the department of pathology, College of Medicine, Yonsei University, for the period from 1996 to 1998. All specimen were from premenopausal women aged from 32~45. Ovarian tissues were collected from the patients performing hysterectomy for benign uterine diseases. Immunohistochemical staining was performed for the detection of DNA fragmented cell, Bcl-2, Bax, Fas and Fas-ligand. RESULTS: Bcl-2 and bax were not expressed on the surrounding cells and oocyte of the primary, primordial and preantral follicles. Fas and Fas-ligand (Fas-L) were not expressed on the surrounding cells on the primordial and primary follicles. But expressed on the surrounding granulosa cells and oocyte in the primordial and primary follicles. In the healthy follicles, Bcl-2 was expressed on the granulosa cells, however, Bax was not expressed. DNA fragmented cells were expressed on the inner granulosa cell layer of atretic follicles. CONCLUSION: Fas, Fas-ligand, and Bax may be responsible for the follicular atresia and Bcl-2 may be involved in the follicular survival in the human ovary.
Apoptosis* ; DNA ; Female ; Follicular Atresia ; Granulosa Cells ; Humans* ; Hysterectomy ; Oocytes ; Ovarian Follicle* ; Ovary ; Pathology ; Pathology, Surgical ; Uterine Diseases