The neonatal ketone body is important for primordial follicle pool formation and regulates ovarian ageing in mice

Adverse nutritional conditions during the perinatal stage are related to early menopause in adulthood;however,the underlying mechanism is still unclear.Herein,we revealed that colostrum-activated ketone body elevation during the postnatal stage regulated primordial follicle reservoir size and then affected ovarian ageing.We found that the expression of the ketogenesis rate-limiting enzyme 3-hydroxy-3-methylglutaryl-CoA synthase 2(Hmgcs2)was largely enhanced during primordial follicle pool formation after birth and might be activated in the ovaries by colostrum.Reactive oxygen species(ROS)elevation in the ovaries leads to follicle apoptosis to deplete damaged follicles,while Hmgcs2 deficiency enhances follicle apoptosis and thus decreases the size of the primordial follicle pool and leads to premature ovarian ageing(POA),which might be related to the activation of cellular endogenous antioxidant system.All these defects could be rescued by ketone body administration,which suppressed ROS-activated follicle apoptosis.Our results suggest that the internal metabolic homeostasis of newborn mice is critical for the primordial reservoir and that any intrauterine and perinatal undernutrition could result in POA.

Differentially Expressed Genes Associated with Primordial Follicle Formation and Transformation to Primary Follicles

Objective: Primordial follicle assembly and the transition from primordial follicle to primary follicle are critical processes in ovarian biology.These processes determine the size of the primordial follicle pool, which may limit the reproductive lifespan of a female. When the follicle pool is depleted, reproduction ceases and females enter menopause. In this study, we aimed to explore the role of differentially expressed genes(DEGs) in the processes of primordial follicle assembly and the transformation from primordial to primary follicle.Methods: The gene chip GSE9300 was downloaded from the Gene Expression Omnibus database. DEGs between ovaries on postnatal day0 and ovaries on postnatal day 4, as well as ovaries on postnatal day 4 and ovaries cultured for 7 days from postnatal day 0 were identified.Gene ontology(GO), pathway enrichment analysis, and protein-protein interaction network construction were performed.Results: In total, 99 upregulated genes and 123 downregulated genes were identified in the process of primordial follicle assembly, and 101 upregulated genes and 98 downregulated genes were identified in the process of transformation from primordial to primary follicle. The GO analysis showed that response to estradiol was associated with two of the processes of assembly and subsequent development of primordial follicle, but the genes involved in response to estradiol between the two processes were significantly different. Furthermore, the two groups of DEGs were all associated with metabolic pathways.Conclusions: DEGs may provide new insights into the exploration of mechanisms related to primordial follicle assembly and subsequent development.

RNA m6A dynamic modification mediated by nucleuslocalized FTO is involved in follicular reserve

In eukaryotic organisms,the most common internal modification of messenger RNA(m RNA)is N6-methyladenosine(m6A).This modification can be dynamically and reversibly controlled by specific enzymes known as m6A writers and erasers.The fat-mass and obesity-associated protein(FTO)catalyzes RNA demethylation and plays a critical role in various physiological and pathological processes.Our research identified dynamic alterations in both m6A and FTO during the assembly of primordial follicles,with an inverse relationship observed for m6A levels and nuclear-localized FTO expression.Application of Fto small interfering RNA(si RNA)altered the expression of genes related to cell proliferation,hormone regulation,and cell chemotaxis,and affected RNA alternative splicing.Overexpression of the full-length Fto gene led to changes in m6A levels,alternative splicing of Cdk5,cell proliferation,cell cycle progression,and proportion of primordial follicles.Conversely,overexpression of Fto lacking a nuclear localization signal(NLS)did not significantly alter m6A levels or primordial follicle assembly.These findings suggest that FTO,localized in the nucleus but not in the cytoplasm,regulates RNA m6A demethylation and plays a role in cell proliferation,cell cycle progression,and primordial follicle assembly.These results highlight the potential of m6A and its eraser FTO as possible biomarkers and therapeutic targets.

Research progress of in vitro activation mechanism and clinical application of female ovarian tissue

The activation and development of primordial follicles is the key to the maturation of female gametes.Premature ovarian insufficiency(POI)patients are unable to complete the primordial follicle activation and development due to follicular dormancy and unbalanced developmental regulation in the body,leading to female infertility.Ovarian tissue in vitro activation(IVA)technology has become a new way to solve the problem of patients who cannot auto-activate primordial follicles to obtain their own mature oocytes.In IVA research,signaling pathways such as PI3K/PTEN/Akt and Hippo have become the focus of current research.This review will describe the relevant research progress and clinical application of the IVA mechanism,and provide a reference for clinical research on ovarian tissue culture and activation in vitro.

SP1 governs primordial folliculogenesis by regulating pregranulosa cell development in mice

Establishment of the primordial follicle(PF)pool is pivotal for the female reproductive lifespan;however,the mechanism of primordial folliculogenesis is poorly understood.Here,the transcription factor SP1 was shown to be essential for PF formation in mice.Our results showed that SP1 is present in both oocytes and somatic cells during PF formation in the ovary.Knockdown of Sp1 expression,especially in pregranulosa cells,significantly suppressed nest breakdown,oocyte apoptosis,and PF formation,suggesting that SP1 expressed by somatic cells functions in the process of primordial folliculogenesis.We further demonstrated that SP1 governs the recruitment and maintenance of Forkhead box L2-positive(FOXL2^+)pregranulosa cells using an Lgr5-EGFP-IRES-CreER^T2(Lgr5-KI)reporter mouse model and a FOXL2^+ cell-specific knockdown model.At the molecular level,SP1 functioned mainly through manipulation of NOTCH2 expression by binding directly to the promoter of the Notch2 gene.Finally,consistent with the critical role of granulosa cells in follicle survival in vitro,massive loss of oocytes in SP1 knockdown ovaries was evidenced before puberty after the ovaries were tranSP1anted under the renal capsules.Conclusively,our results reveal that SP1 controls the establishment of the ovarian reserve by regulating pregranulosa cell development in the mammalian ovary.

In Vitro Growth of Human Ovarian Follicles for Fertility Preservation

Young female cancer survival rates significantly increased due to the great progress of cancer therapy.In fact,cryostorage and transplantation of ovarian tissue have already resulted in the birth of healthy babies.Follicle in vitro growth(IVG)has the great potential of restoring fertility by achieving functional oocytes from the most immature stages to maturation.This is suitable for a wide range of patients,from pubertal to perimenopause women.Notable achievements have been achieved in human follicle IVG in the past decade.Mature oocytes have been successfully collected from long-term sequential follicle IVG.However,it is still a major challenge to establish a stable and efficient follicle IVG system able to generate mature and competent oocytes.Hereby,we review the approaches being taken so far using ovarian tissue to support follicle growth at different stages in vitro.

The programmed death of fetal oocytes and the correlated surveillance mechanisms

Gamete production is essential for mammalian reproduction.In the ovaries,the primordial follicle,which is the basic reproductive unit,is formed either perinatally or during the second pregnancy stage in humans.However,some oocytes die before the establishment of the primordial follicle pool.Consequently,it is essential to uncover how the size of the primordial follicle pool is determined and how the programmed cell death of oocytes is performed under potential surveillance.According to recent studies,the fate of oocytes in the fetal ovary seems to be determined by different protective strategies through the timely control of apoptosis or autophagy.In this review,we discuss at least three oocyte-derived protective biomarkers,glycogen synthase kinase 3 beta,X-linked inhibitor of apoptosis,and Lysine-specific demethylase 1(also known as KDM1A),responsible for surveilling the developmental quality of fetal oocytes to coordinate primordial follicle formation in the fetal ovary.This review contributes to a better understanding of the secrets of the female reproductive reserve under physiological conditions.