Single-cell transcriptomic atlas of goat ovarian aging

Background The ovaries are one of the first organs that undergo degenerative changes earlier in the aging process,and ovarian aging is shown by a decrease in the number and quality of oocytes.However,little is known about the molecular mechanisms of female age-related fertility decline in different types of ovarian cells during aging,especially in goats.Therefore,the aim of this study was to reveal the mechanisms driving ovarian aging in goats at single-cell resolution.Results For the first time,we surveyed the single-cell transcriptomic landscape of over 27,000 ovarian cells from newborn,young and aging goats,and identified nine ovarian cell types with distinct gene-expression signatures.Functional enrichment analysis showed that ovarian cell types were involved in their own unique biological processes,such as Wnt beta-catenin signalling was enriched in germ cells,whereas ovarian steroidogenesis was enriched in granulosa cells(GCs).Further analysis showed that ovarian aging was linked to GCs-specific changes in the antioxidant system,oxidative phosphorylation,and apoptosis.Subsequently,we identified a series of dynamic genes,such as AMH,CRABP2,THBS1 and TIMP1,which determined the fate of GCs.Additionally,FOXO1,SOX4,and HIF1A were identified as significant regulons that instructed the differentiation of GCs in a distinct manner during ovarian aging.Conclusions This study revealed a comprehensive aging-associated transcriptomic atlas characterizing the cell typespecific mechanisms during ovarian aging at the single-cell level and offers new diagnostic biomarkers and potential therapeutic targets for age-related goat ovarian diseases.

Current understanding of ovarian aging

The reproductive system of human female exhibits a much faster rate of aging than other body systems.Ovarian aging is thought to be dominated by a gradual decreasing numbers of follicles,coinciding with diminished quality of oocytes.Menopause is the final step in the process of ovarian aging.This review focuses on the mechanisms underlying the ovarian aging involving a poor complement of follicles at birth and a high rate of attrition each month,as well as the alternated endocrine factors.We also discuss the possible causative factors that contribute to ovarian aging,e.g.,genetic factors,accumulation of irreparable damage of microenvironment,pathological effect and other factors.The appropriate and reliable methods to assess ovarian aging,such as quantification of follicles,endocrine measurement and genetic testing have also been discussed.Increased knowledge of the ovarian aging mechanisms may improve the prevention of premature ovarian failure.

Ovarian aging:mechanisms and intervention strategies

Ovarian reserve is essential for fertility and influences healthy aging in women.Advanced maternal age correlates with the progressive loss of both the quantity and quality of oocytes.The molecular mechanisms and various contributing factors underlying ovarian aging have been uncovered.In this review,we highlight some of critical factors that impact oocyte quantity and quality during aging.Germ cell and follicle reserve at birth de-termines reproductive lifespan and timing the menopause in female mammals.Accelerated diminishing ovarian reserve leads to premature ovarian aging or insufficiency.Poor oocyte quality with increasing age could result from chromosomal cohesion deterioration and misaligned chromosomes,telomere shortening,DNA damage and associated genetic mutations,oxidative stress,mitochondrial dysfunction and epigenetic alteration.We also discuss the intervention strategies to delay ovarian aging.Both the efficacy of senotherapies by antioxidants against reproductive aging and mitochondrial therapy are discussed.Functional oocytes and ovarioids could be rejuvenated from pluripotent stem cells or somatic cells.We propose directions for future interventions.As couples increasingly begin delaying parenthood in life worldwide,understanding the molecular mechanisms during female reproductive aging and potential intervention strategies could benefit women in making earlier choices about their reproductive health.

Age-related Changes in Humanin Expression in the Ovarian Tissue of Rat

Objective This study examined humanin expression in rat ovarian tissue,its cellular localization,and its correlation with rat age under physiological conditions.Methods A total of 40 Sprague-Dawley rats of various ages(2,12,30,and 60 days old and 1 year old)were grouped by age.Immunofluorescence and immunohistochemical techniques were used to observe humanin expression and cellular location in the ovarian tissues of rats from each age group.In addition,Western blotting and Real-time quantitative reverse transcription PCR(qRT-PCR)techniques were used to measure humanin expression level in the ovarian tissues of rats from each age group.Results The immunofluorescence and immunohistochemical results confirmed that humanin was expressed in rat ovarian tissues.In addition,cellular localization analysis showed that humanin was expressed in the cytoplasm of oocytes,interstitial cells,granulosa cells and theca cells in all levels of follicles after the primary follicles,and in the corpus luteum.The qRT-PCR results revealed that the level of humanin expression in the ovarian tissues of 12-day-old rats was non-significantly higher than that in the ovarian tissues of 2-day-old rats(P>0.05),whereas the levels of humanin expression in the ovarian tissues of 30-day-old,60-day-old,and 1-year-old rats were significantly lower than that in the ovarian tissues of 2-day-old rats(P<0.05).The Western blotting results demonstrated that the levels of humanin protein expression in the ovarian tissues of 60-day-old and 1-year-old rats were significantly lower than those of 2-day-old rats(P<0.01),whereas there was no significant difference in the level of humanin protein expression between the ovarian tissues of 12-day-old and 30-day-old rats.Conclusion This study confirmed that humanin is expressed in the cytoplasm of various cells in rat ovarian tissues.Moreover,the level of humanin expression was highest in the ovarian tissues of 12-day-old rats,and it subsequently decreased with age.The changes in the expression of humanin in the ovary of rats at different ages will lay the foundation for the role of humanin in ovarian aging.The effect of humanin on ovarian function is worthy of further study in the future.

Fecal microbiota transplantation from young donor mice improves ovarian function in aged mice

Advanced maternal age is characterized by declines in the quantity and quality of oocytes in the ovaries,and the aging process is accompanied by changes in gut microbiota composition.However,little is known about the relationship between gut microbiota and ovarian aging.By using fecal microbiota transplantation(FMT)to transplant material from young(5-week-old)into aged(42-week-old)mice,we find that the composition of gut microbiota in FMT-treated mice presents a“younger-like phenotype”and an increase of commensal bacteria,such as Bifidobacterium and Ruminococcaceae.Moreover,the FMT-treated mice show increased anti-inflammatory cytokine IL-4 and decreased pro-inflammatory cytokine IFN-γ.Fertility tests for assessing ovarian function reveal that the first litter size of female FMT-treated mice is significantly higher than that of the non-FMT group.Morphology analysis demonstrates a dramatic decrease in follicle atresia and apoptosis as well as an increase in cellular proliferation in the ovaries of the FMT-treated mice.Our results also show that FMT improves the immune microenvironment in aged ovaries,with decreased macrophages and macrophage-derived multinucleated giant cells(MNGCs).These results suggest that FMT from young donors could be a good choice for delaying ovarian aging.

Physiological roles of activins in the human ovary

Initially discovered in the pituitary as stimulators of follicle stimulating hormone,activins are homo-or heterodimers of inhibin subunits,which belong to the transforming growth factor-b superfamily.Subsequent studies have demonstrated that these growth factors play multifaceted roles in regulating various functions in multiple organs,including the ovary.The spatial and temporal expression of inhibin subunits(a,bA,bB,and bC),their cognate receptors,and activin-binding proteins(inhibins and follistatins)in the principal cells of growing follicles in human ovaries indicates that these activin isoforms are involved in ovarian biology.Information collected from animal studies and clinical samples suggests that these locally produced growth factors are crucial modulators of various ovarian functions,including primordial germ cell development,follicular growth and development,ovarian steroidogenesis,extracellular matrix remodeling,oocyte maturation,ovulation,and luteal function.Along with gonadotropins,intrafollicular activins exert synergistic and complementary effects on growing follicles to help them develop a mature,competent oocyte that is prepared for fertilization.Abnormal activin expression,an imbalanced activin/follistatin ratio,and the dysregulation of the activin signaling pathway have been observed in several ovarian pathologies,such as reproductive aging,polycystic ovary syndrome,and ovarian cancers.Recent advancements in our understanding of the molecular interactions and mechanisms that underlie activins and the development of related ovarian abnormalities have provided insights into disease pathogenesis and increased opportunities to achieve efficient and safe therapies.