The ovarian germinal reserve and apoptosis-related proteins in the infant and adolescent human ovary

Abstract

BackgroundNormal pubertal ovary displays all stages of follicular development and a biased BAX/BCL2 protein ratio in favor of pro-apoptotic BAX protein comparable to the adult ovary. However, adolescents suffering malignant extra-gonadal disease show a limited follicle development after cytotoxic drug treatment and a reduced capacity of in vitro follicle growth. We evaluated the expression of pro- and anti-apoptotic members of the BCL2 gene family, the FAS/FAS-L proteins from the extrinsic apoptosis pathway, the germ-cell-specific marker VASA, the pluripotency marker OCT3/4, and markers of early and late apoptosis in the ovary of pubertal patients with malignant extra-gonadal disease, which received or not pre-surgery chemotherapy, entering a cryopreservation program.ResultsOvarian biopsies from 12 adolescent girls were screened for follicle count and expression of VASA, OCT3/4, BAX, BCL2, MCL1L and S, cleaved-BID, FAS/FAS-L and CASPASE 3 through immunohistochemistry, western blot and RT-PCR. All stages of folliculogenesis, from primordial to antral follicle, were present in all 12 patients analyzed. VASA and most of the screened apoptosis-related genes showed a pattern of immune-expression comparable to that previously reported. OCT3/4 showed a cytoplasmic localization in the great majority of the primordial follicles; however, in some cases the localization was nuclear. In addition, OCT3/4B showed a significant reduction compared to OCT3/4A. Unexpectedly, BCL2 was detected at all stages of folliculogenesis, associated to the Balbiani’s body in the primordial follicles, regardless of whether patients had or had not received chemotherapy, ruling out the possibility that its expression is a protective response to chemotherapy.ConclusionsThese findings reveal new information on the morphological status of the follicular reserve and the expression of apoptosis-related genes in histologically normal adolescent ovary from patients undergoing extragonadal cancer. The unexpected expression of apoptosis-inhibiting BCL2 protein, both in patients that had or had not received chemotherapy, opens a new avenue for thorough investigations. Moreover, the nuclear localization of OCT3/4 protein in primordial follicle-enclosed oocytes suggests a possible increased activity of ovarian stem cells in response to chemotherapy and/or extragonadal cancer. This new information can be essential for a better managing of in vitro culture of follicles that can be removed by filtration from preserved ovarian tissue, especially in girls that entered a cryopreservation program.

Pathways coordinating oocyte attrition and abundance during mammalian ovarian reserve establishment

“…This study was expanded upon by Omari et al (2015), who observed these same effects in vivo as a result of germ cell‐specific depletion of MCL1. Intriguingly, expression of BCL2 and BAX proteins has been observed during adolescent human folliculogenesis as well, though their functions in this context remain unclear (Albamonte, Albamonte, Bou‐Khair, Zuccardi, & Vitullo, 2019; Albamonte, Albamonte, Stella, Zuccardi, & Vitullo, 2013). These data highlight that many BCL2‐family members may exert their functions during specific developmental windows despite their more ubiquitous expression, emphasizing that it may be the net balance of all family members expressed during a particular developmental process that regulates cell survival outcome.…”

Follicular development and the expression of BAX and vascular endothelial growth factor in transplanted ovaries in uni- and bilateral ovariectomized mice: An experimental study

“…BAX as a proapoptotic protein is expressed in both granulosa cells and oocytes. It is an important regulator of follicular growth and atresia, which plays a central role in ovarian cell death by the intrinsic pathway of apoptosis (17,18). A higher incidence of apoptosis was shown within grafted ovarian tissue (19)(20)(21)(22); however, a well-preserved ovarian follicles with a low proportion of cell death in grafted tissue was demonstrated by others (23).…”

“…Apoptosis cell death plays a fundamental role in follicular atresia. It takes place by two intrinsic and extrinsic pathways, and several pro-and antiapoptotic proteins involve in these pathways (17). BAX as a proapoptotic protein is expressed in both granulosa cells and oocytes.…”

Meiotic Cohesin and Variants Associated With Human Reproductive Aging and Disease

“…The number of primordial germ cells, or oogonia, peaks at approximately 6–7 million during mid-gestation, followed by progressive atresia with approximately 1–2 million oocytes present at birth ( Motta et al, 1997 ; Pereda et al, 2006 ; Mamsen et al, 2012 ). By puberty, there is estimated to be 300,000–500,000 oocytes remaining, and approximately 25,000 at age 37 years ( Forabosco and Sforza, 2007 ; Albamonte et al, 2019 ). Menopause occurs when the number of remaining oocytes falls below a critical threshold of about 1000, regardless of age ( American College of Obstetricians and Gynecologists Committee on Gynecologic Practice and Practice Committee, 2014 ).…”