The Effects of Heat Stress on the Ovary, Follicles and Oocytes: A Systematic Review.

Climate change is driving significant environmental changes with profound implications for human health, including fertility. While the detrimental effects of heat on spermatogenesis are well-documented, the impact of elevated temperatures on ovaries and female fertility remains less explored. This review systematically examines the literature on heat stress (HS) effects on mammalian ovaries, follicles, and oocytes.

Multinucleated giant cells are hallmarks of ovarian aging with unique immune and degradation-associated molecular signatures.

The ovary is one of the first organs to exhibit signs of aging, characterized by reduced tissue function, chronic inflammation, and fibrosis. Multinucleated giant cells (MNGCs), formed by macrophage fusion, typically occur in chronic immune pathologies, including infectious and non-infectious granulomas and the foreign body response , but are also observed in the aging ovary . The function and consequence of ovarian MNGCs remain unknown as their biological activity is highly context-dependent, and their large size has limited their isolation and analysis through technologies such as single-cell RNA sequencing.

Hallmarks of female reproductive aging in physiologic aging mice.

The female reproductive axis is one of the first organ systems to age, which has consequences for fertility and overall health. Here, we provide a comprehensive overview of the biological process of female reproductive aging across reproductive organs, tissues and cells based on research with widely used physiologic aging mouse models, and describe the mechanisms that underpin these phenotypes. Overall, aging is associated with dysregulation of the hypothalamic-pituitary-ovarian axis, perturbations of the ovarian stroma, reduced egg quantity and quality, and altered uterine morphology and function that contributes to reduced capacity for fertilization and impaired embryo development.

Classification of Human Ovarian Follicle Morphology: Recommendations of the NICHD-Sponsored Ovarian Nomenclature Workshop.

Objective: To develop a consensus on histologic human ovarian follicle staging nomenclature, provide guidelines for follicle density calculation, and assess changes due to fixation to enhance communication among clinicians and ovarian biology researchers in order to gain a deeper understanding of human fertility.

Methods: Beginning in March 2021, the Ovarian Nomenclature Workshop's Follicle Classification Working Subgroup was organized by the Pediatric and Adolescent Gynecology program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).

Results: The Follicle Working Subgroup recommends consolidation and expansion of the current classification systems to include six stages of normal preantral follicles, five stages of normal antral follicles, as well as categories of corpus lutea, abnormal preantral follicles, abnormal antral follicles, and other distinct follicle types.