Impact of uteroplacental insufficiency on ovarian follicular pool in the rat

Associations between birthweight and preterm birth and the ages at menarche and menopause

BACKGROUND

Women who reach menarche and menopause at earlier ages have been shown to be at increased risk for numerous conditions including cardiovascular disease, cancer, depression, and obesity; however, risk factors for earlier ages of menarche and menopause are not fully understood. Therefore, we aimed to perform a retrospective investigation of the associations between a personal birthweight and/or being born preterm and the age of and menarche and menopause and related events in the Women's Health Initiative, a large, racially and ethnically diverse cohort of postmenopausal women.

METHODS

At study entry, women reported their birthweight by category (< 6 lbs., 6-7 lbs. 15 oz, 8-9 lbs. 15 oz, or ≥ 10 lbs.) and preterm birth status (4 or more weeks premature). Ages at events related to menarche and menopause were also self-reported. Linear regression and logistic regression models were used to estimate unadjusted and adjusted effect estimates (β) and odds ratios (OR), respectively (n ≤ 86,857). Individuals born preterm were excluded from all birthweight analyses.

RESULTS

After adjustments, individuals born weighing < 6lbs. were more likely to reach natural menopause at an earlier age (adjusted β=-0.361, SE = 0.09, P = < 0.001) and have a shorter reproductive window (adjusted β = -0.287, SE = 0.10, p < 0.004) compared to individuals weighing 6-7 lbs. 15 oz. Individuals born preterm were also more likely to reach natural menopause at an earlier age (adjusted β=-0.506, SE = 0.16, P = 0.001) and have a shorter reproductive window (adjusted β = -0.418, SE = 0.17, p < 0.006).

CONCLUSIONS

These findings raise concerns that, as more preterm and low birthweight individuals survive to adulthood, the prevalence of earlier-onset menarche and menopause may increase. Clinical counseling and interventions aimed at reducing the incidence of preterm and low birthweight births, as well as intensification of lifestyle modifications to reduce CVD risk among women with these early-life risk factors, should be prioritized.

Beyond defence: Immune architects of ovarian health and disease

Throughout the individual's reproductive period of life the ovary undergoes continues changes, including cyclic processes of cell death, tissue regeneration, proliferation, and vascularization. Tissue-resident leucocytes particularly macrophages, play a crucial role in shaping ovarian function and maintaining homeostasis. Macrophages crucially promote angiogenesis in the follicles and corpora lutea, thereby supporting steroidogenesis. Recent research on macrophage origins and early tissue seeding has unveiled significant insights into their role in early organogenesis, e.g. in the testis. Here, we review evidence about the prenatal ovarian seeding of leucocytes, primarily macrophages with angiogenic profiles, and its connection to gametogenesis. In the prenatal ovary, germ cells proliferate, form cysts, and undergo changes that, following waves of apoptosis, give rice to the oocytes contained in primordial follicles. These follicles constitute the ovarian reserve that lasts throughout the female's reproductive life. Simultaneously, yolk-sac-derived primitive macrophages colonizing the early ovary are gradually replaced or outnumbered by monocyte-derived fetal macrophages. However, the cues indicating how macrophage colonization and follicle assembly are related are elusive. Macrophages may contribute to organogenesis by promoting early vasculogenesis. Whether macrophages contribute to ovarian lymphangiogenesis or innervation is still unknown. Ovarian organogenesis and gametogenesis are vulnerable to prenatal insults, potentially programming dysfunction in later life, as observed in polycystic ovary syndrome. Experimental and, more sparsely, epidemiological evidence suggest that adverse stimuli during pregnancy can program defective folliculogenesis or a diminished follicle reserve in the offspring. While the ovary is highly sensitive to inflammation, the involvement of local immune responses in programming ovarian health and disease remains to be thoroughly investigated.

Effects and mechanisms of intrauterine chronic hypoxia on ovarian reserve function of zygotic rats

Chronic intrauterine hypoxia (ICH) may lead to permanent alterations in the offspring's body structure, function, and metabolism through the "developmental programming" pathway, resulting in lasting changes in physiology and metabolism, as well as the onset of adult-onset diseases. The aim was to investigate intrauterine growth restriction caused by ICH and its effect on ovarian reserve function in female offspring at different developmental stages after birth. Healthy female Sprague-Dawley rats (n = 20) were pregnant by normal mating, and the rats in the ICH group were treated with chronic intrauterine hypoxia twice a day for 04 h00 each time from day 4 to 21 of gestation. After the first hypoxic treatment, four pregnant rats were randomly selected from the ICH and natural control groups for arterial blood gas analysis. In the ICH group, birth weight and body weight on the 5th day after birth were less than in the control group, the total number of follicles and the number of primordial follicles in the offspring of the ICH group were significantly reduced on postnatal days 5, 20, and 40 (p < 0.05). ICH decreases ovarian reserve function in female offspring rats and programmatically regulates the differential expression of ovarian miRNAs in female offspring rats.

Sex-dependent Effect of In-utero Exposure to Δ9-Tetrahydrocannabinol on Glucagon and Stathmin-2 in Adult Rat Offspring

OBJECTIVES

Administration of Δ⁹-tetrahydrocannabinol (Δ⁹-THC) to pregnant rats results in glucose intolerance, insulin resistance and reduced islet mass in female, but not male, offspring. The effects of Δ⁹-THC on other islet hormones is not known. One downstream target of the cannabinoid receptor, stathmin-2 (Stmn2), has recently been shown to suppress glucagon secretion, thereby suggesting Δ⁹-THC may also affect alpha-cell function. The aim of the present study was to determine the effects of in-utero Δ⁹-THC exposure on the profile of glucagon, insulin and Stmn2 in the rat offspring islet and serum.

METHODS

Pregnant Wistar rat dams were injected with Δ⁹-THC (3 mg/kg per day, intraperitoneally) or vehicle from gestational day 6 to birth. Offspring were euthanized at postnatal day 21 (PND21) or at 5 months (adult) to collect blood and pancreata.

RESULTS

At PND21, control and Δ⁹-THC-exposed offspring showed that Stmn2 had a strong colocalization with glucagon (Pearson's correlation coefficient ≥0.6), and a weak colocalization with insulin (Pearson's correlation coefficient <0.4) in both males and females, with no changes by either treatment or sex. In adult female offspring in the Δ⁹-THC group, intensity analysis indicated an increased insulin-to-glucagon (I/G; p<0.05) ratio and a decreased glucagon-to-Stmn2 (G/S; p<0.01) ratio, and no changes in these ratios in adult males. Furthermore, Δ⁹-THC did not alter fasting blood glucose and serum insulin levels in either male or female adult offspring. However, female Δ⁹-THC-exposed offspring exhibited an increased I/G ratio (p<0.05) and decreased G/S ratio in serum by adulthood (p<0.05).

CONCLUSION

Collectively, the reduced G/S ratio in both islet and serum in association with an increased serum I/G ratio has direct correlations with early glucose intolerance and insulin resistance observed exclusively in females' offspring in this prenatal cannabinoid model.

Association of In Utero Exposures With Risk of Early Natural Menopause

Suboptimal pregnancy conditions may affect ovarian development in the fetus and be associated with early natural menopause (ENM) for offspring. A total of 106,633 premenopausal participants in Nurses' Health Study II who provided data on their own prenatal characteristics, including diethylstilbestrol (DES) exposure, maternal cigarette smoking exposure, multiplicity, prematurity, and birth weight, were followed from 1989 to 2017. Cox regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations of in utero exposures with ENM. During 1.6 million person-years of follow-up, 2,579 participants experienced ENM. In multivariable models, women with prenatal DES exposure had higher risk of ENM compared with those without it (HR = 1.33, 95% CI: 1.06, 1.67). Increased risk of ENM was observed for those with low (<5.5 pounds (<2.5 kg)) versus normal (7.0-8.4 pounds (3.2-3.8 kg)) birth weight (HR = 1.21, 95% CI: 1.01, 1.45). Decreasing risk was observed per 1-pound (0.45-kg) increase in birth weight (HR = 0.93, 95% CI: 0.90, 0.97). Prenatal smoking exposure, being part of a multiple birth, and prematurity were not associated with ENM. In this large cohort study, lower birth weight and prenatal DES exposure were associated with higher risk of ENM. Our results support a need for future research to examine in utero exposures that may affect offspring reproductive health.

Perinatal hypoxia leads to primordial follicle activation and premature depletion of ovarian reserve

BACKGROUND

The human ovary contains 6-million follicles during the 20th week of embryonic development and 1 million at birth. Girls born at small for gestational age weight demonstrate higher FSH levels during infancy, an earlier onset of puberty, and menarche. In light of these observations, we hypothesized that exposure to hypoxia at the early neonatal period might impact the primordial follicular pool and lead to premature depletion of ovarian reserve.

METHODS

Ovarian development in the rat model at days 1-5 postpartum reflects its human counterpart in the late perinatal period. We exposed newborn rat pups (n = 5) to controlled hypoxia, (5% oxygen/95% nitrogen) for 10 min three times daily for days 1-5 postpartum. On day 5, ovaries were harvested, H&E, Ki-67, and TUNEL staining were performed.

RESULTS

The percentage of primordial follicles out of total follicles in ovaries of pups exposed to hypoxia was lower compared to control (76 ± 8.2% and 90.33 ± 6.3% respectively, p < .05). Correspondingly the percentage of primary and secondary follicles was higher than in control. The mean stromal Ki67 staining score was significantly lower in the study group (1.67 ± 0.58 and 2.5 ± 0.55 respectively, p < .05). TUNEL staining demonstrated no difference in stromal apoptosis rates between both groups.

CONCLUSIONS

We provide evidence for the first time that perinatal hypoxia causes premature activation and growth initiation of dormant follicles. These changes were associated with decreased stromal cell proliferation, suggesting hypoxia-induced impairment of the support cell pool as a possible mechanism for accelerated follicular activation.

Gestational exposure to Δ9-THC impacts ovarian follicular dynamics and angiogenesis in adulthood in Wistar rats

With the legalization of marijuana (Cannabis sativa) and increasing use during pregnancy, it is important to understand its impact on exposed offspring. Specifically, the effects of Δ-9-tetrahydrocannabinol (Δ9-THC), the major psychoactive component of cannabis, on fetal ovarian development and long-term reproductive health are not fully understood. The aim of this study was to assess the effect of prenatal exposure to Δ9-THC on ovarian health in adult rat offspring. At 6 months of age, Δ9-THC-exposed offspring had accelerated folliculogenesis with apparent follicular development arrest, but no persistent effects on circulating steroid levels. Ovaries from Δ9-THC-exposed offspring had reduced blood vessel density in association with decreased expression of the pro-angiogenic factor VEGF and its receptor VEGFR-2, as well as an increase in the anti-angiogenic factor thrombospondin 1 (TSP-1). Collectively, these data suggest that exposure to Δ9-THC during pregnancy alters follicular dynamics during postnatal life, which may have long-lasting detrimental effects on female reproductive health.

Intraovarian vascular enhancement via stromal injection of platelet-derived growth factors: Exploring subsequent oocyte chromosomal status and in vitro fertilization outcomes

The inverse correlation between maternal age and pregnancy rate represents a major challenge for reproductive endocrinology. The high embryo ploidy error rate in failed in vitro fertilization (IVF) cycles reflects genetic misfires accumulated by older oocytes over time. Despite the application of different follicular recruitment protocols during IVF, gonadotropin modifications are generally futile in addressing such damage. Even when additional oocytes are retrieved, quality is frequently poor. Older oocytes with serious cytoplasmic and/or chromosomal errors are often harvested from poorly perfused follicles, and ovarian vascularity and follicular oxygenation impact embryonic chromosomal competency. Because stimulation regimens exert their effects briefly and immediately before ovulation, gonadotropins alone are an ineffective antidote to long-term hypoxic pathology. In contrast, the tissue repair properties (and particularly the angiogenic effects) of platelet-rich plasma (PRP) are well known, with applications in other clinical contexts. Injection of conventional PRP and/or its components (e.g., isolated platelet-derived growth factors as a cell-free substrate) into ovarian tissue prior to IVF has been reported to improve reproductive outcomes. Any derivative neovascularity may modulate oocyte competence by increasing cellular oxygenation and/or lowering concentrations of intraovarian reactive oxygen species. We propose a mechanism to support intrastromal angiogenesis, improved follicular perfusion, and, crucially, embryo ploidy rescue. This last effect may be explained by mRNA upregulation coordinated by PRP-associated molecular signaling, as in other tissue systems. Additionally, we outline an intraovarian injection technique for platelet-derived growth factors and present this method to help minimize reliance on donor oocytes and conventional hormone replacement therapy.