Effects of chronic unpredictable mild stress on ovarian reserve in female rats: Feasibility analysis of a rat model of premature ovarian failure

Comparison of the different animal modeling and therapy methods of premature ovarian failure in animal model

Incidence of premature ovarian failure (POF) is higher with the increase of the pace of life. The etiology of POF is very complex, which is closely related to genes, immune diseases, drugs, surgery, and psychological factors. Ideal animal models and evaluation indexes are essential for drug development and mechanism research. In our review, we firstly summarize the modeling methods of different POF animal models and compare their advantages and disadvantages. Recently, stem cells are widely studied for tumor treatment and tissue repair with low immunogenicity, high homing ability, high ability to divide and self-renew. Hence, we secondly reviewed recently published data on transplantation of stem cells in the POF animal model and analyzed the possible mechanism of their function. With the further insights of immunological and gene therapy, the combination of stem cells with other therapies should be actively explored to promote the treatment of POF in the future. Our article may provide guidance and insight for POF animal model selection and new drug development.

Chaigui granule exerts anti-depressant effects by regulating the synthesis of Estradiol and the downstream of CYP19A1-E2-ERKs signaling pathway in CUMS-induced depressed rats

Background: There is a significant gender difference in the prevalence of depression. Recent studies have shown that estrogen plays a crucial role in depression. Therefore, studying the specific mechanism of estrogen's role in depression can provide new ideas to address the treatment of depression. Chaigui granule has been shown to have exact antidepressant efficacy, and the contents of saikosaponin (a, b1, b2, d) and paeoniflorin in Chaigui granule are about 0.737% and 0.641%, respectively. Some studies have found that they can improve depression-induced decrease in testosterone (T) levels (∼36.99% decrease compared to control). However, whether Chaigui granule can exert antidepressant efficacy by regulating estrogen is still unclear. This study aimed to elucidate the regulation of estrogen levels by Chaigui granule and the underlying mechanism of its anti-depressant effect. Methods: Eighty-four male Sprague-Dawley (SD) rats were modeled using a chronic unpredictable mild stress (CUMS) procedure. The administration method was traditional oral gavage administration, and behavioral indicators were used to evaluate the anti-depressant effect of Chaigui granule. Enzyme-linked immunosorbent assay (ELISA) was adopted to assess the modulating impact of Chaigui granule on sex hormones. Then, reverse transcription-quantitative PCR (RT-qPCR), and Western blot (WB) techniques were employed to detect extracellular regulated protein kinases (ERK) signaling-related molecules downstream of estradiol in the hippocampus tissue. Results: The administration of Chaigui granule significantly alleviated the desperate behavior of CUMS-induced depressed rats. According to the results, we found that Chaigui granule could upregulate the level of estradiol (E2) in the serum (∼46.56% increase compared to model) and hippocampus (∼26.03% increase compared to model) of CUMS rats and increase the levels of CYP19A1 gene and protein, which was the key enzyme regulating the synthesis of T into E2 in the hippocampus. Chaigui granule was also found to have a significant back-regulatory effect on the gene and protein levels of ERβ, ERK1, and ERK2. Conclusion: Chaigui granule can increase the synthesis of E2 in the hippocampus of CUMS-induced depressed rats and further exert antidepressant effects by activating the CYP19A1-E2-ERKs signaling pathway.

Chronic unpredictable mild stress-induced mouse ovarian insufficiency by interrupting lipid homeostasis in the ovary

Ovarian insufficiency results from a number of disorders, and a certain causal relationship between psychological stress and ovarian insufficiency has been reported, but the underlying mechanism remains unclear. In our study, C57BL/6J female mice were subjected to chronic unpredictable mild stress (CUMS), and depression-like mice were selected and identified according to the behavioral tests. The defective ovarian follicle development, low 17 β-estradiol (E₂), and anti-Mullerian hormone (AMH) levels, which were consistent with the clinical characteristics of ovarian insufficiency, indicated that depression-like mice may be used to assess the effects of psychological stress on female reproductive function. To investigate a possible mechanism, lipid homeostasis of the ovary was detected by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis, and the decreased abundance of cholesteryl ester (CE 24:4) was supported to be associated with the downregulated E₂. Moreover, granulosa cells did undergo more apoptosis in response to psychological stress, which was caused by downregulated Bcl2 and Bcl2/Bax in granulosa cells. Additionally, the disorder of cell death and growth-related pathways in depression-like mouse ovaries was confirmed by RNA-seq analysis. Taken together, this study will provide a better understanding of the female reproductive problem under psychological stress.

Selection of the Male or Female Sex in Chronic Unpredictable Mild Stress-Induced Animal Models of Depression

Depression is a serious public health problem and an important factor leading to disease-related disability. Influenced by many factors, such as psychological, hormonal, and genetic factors, the incidence rate of depression in females is approximately two times that in males. However, in preclinical neuroscience research, the selection of the animals' sex for use in depression models has been controversial. At present, in most preclinical studies, the animals generally chosen in depression models have been male rodents rather than female rodents. It remains doubtful whether the data obtained from male animals can be generalized to female animals. The performance of female animals in preclinical studies of depression has been inconclusive. Based on a review of a large number of original studies in the PubMed database, it was found that although male rodents are more commonly used in the study of depression, the use of female animals also shows good modeling of depression and has its advantages. The influence of the animals' sex in the chronic unpredictable mild stress (CUMS) model needs further research.

Current Research on Complementary and Alternative Medicine in the Treatment of Premature Ovarian Failure: An Update Review

Complementary and alternative medicine (CAM) encompasses a wide range of different non-mainstream therapies that have been increasingly used for the treatment or adjunct treatment of various ailments, with premature ovarian failure (POF) being one of the most common conditions treated with CAM. This review updates the progress of CAM in the treatment of POF, and we focus specifically on reviewing the evidence for the efficacy and mechanisms of a range of CAM treatments in POF, including single herbal medicines and their active ingredients, compound Chinese medicines, acupuncture and moxibustion, psychotherapy, exercise, vitamins, massage, and dietary supplements. According to the literature, CAM is very helpful for improving POF symptoms, and we hope to provide some instructive suggestions for clinical treatment and experimental research in the future. However, more clinical trials are needed to prove the safety of CAM.

Impact of Chemical Endocrine Disruptors and Hormone Modulators on the Endocrine System

There is growing concern regarding the health and safety issues of endocrine-disrupting chemicals (EDCs). Long-term exposure to EDCs has alarming adverse health effects through both hormone-direct and hormone-indirect pathways. Non-chemical agents, including physical agents such as artificial light, radiation, temperature, and stress exposure, are currently poorly investigated, even though they can seriously affect the endocrine system, by modulation of hormonal action. Several mechanisms have been suggested to explain the interference of EDCs with hormonal activity. However, difficulty in quantifying the exposure, low standardization of studies, and the presence of confounding factors do not allow the establishment of a causal relationship between endocrine disorders and exposure to specific toxic agents. In this review, we focus on recent findings on the effects of EDCs and hormone system modulators on the endocrine system, including the thyroid, parathyroid glands, adrenal steroidogenesis, beta-cell function, and male and female reproductive function.

Chronic Stress Detrimentally Affects In Vivo Maturation in Rat Oocytes and Oocyte Viability at All Phases of the Estrous Cycle

Simple Summary

Recently, a significant relationship between stress and reproductive failure in women was reported; being one of the possible causes of infertility. The World Health Organization recognizes infertility as a global public health issue; therefore, the interest in understanding the main causes of this issue has increased over the last few decades. Thus, many studies have reported that stress can adversely alter the functionality of the hypothalamic-pituitary-gonadal axis; as well as being one of the reasons of subfertility in patients undergoing in vitro fertilization. Therefore, it can be assumed that stress is closely related to poor in vitro fertilization outcomes. In chronically stressed female rats, irregular estrous cyclicity, increased corticosterone levels, decreased oocyte viability, and increased percentage of abnormal oocytes were obtained in all estrous cycle phases, resulting in reduced oocyte maturation during proestrus. Oocyte maturation disturbed by chronic stress is a crucial factor by which chronic stress disrupts female reproduction.

Abstract

Background: Stress has been considered as one of the causes of decreased reproductive function in women. However, direct evidence of the effect of chronic stress on oocytes depending on estrous cycle phases is limited. Objective: The present study aimed to evaluate the impact of chronic stress on the viability, integrity, and maturation of rat oocytes depending on estrous cycle phases, specifically proestrus, estrus, and diestrus. Methods: For this purpose, adult female rats were stressed daily by cold water immersion (15 °C) for 30 consecutive days. Results: In chronically stressed female rats, irregular estrous cyclicity, increased corticosterone levels, decreased oocyte viability, and an increased percentage of abnormal oocytes were obtained in all the estrous cycle phases, resulting in reduced oocyte maturation during proestrus. Conclusion: Oocyte maturation disturbed by chronic stress is a crucial factor by which chronic stress disrupts female reproduction

Bone Marrow-Derived Mesenchymal Stem Cells Reverse Radiotherapy-Induced Premature Ovarian Failure: Emphasis on Signal Integration of TGF-β, Wnt/β-Catenin and Hippo Pathways

Radiotherapy is an indispensable cancer treatment approach. However, it is associated with hazardous consequences on multiple organs characterized by insidious worsening severity over time. This study aimed to examine the potential therapeutic effects of bone marrow mesenchymal stem cells (BM-MSCs) in radiation-induced premature ovarian failure (POF). Exposing female rats to 3.2 Gy whole-body ϒ-rays successfully induced POF. One week later, a single intravenous injection of BM-MSCs (2*10⁶) cells was administered. BM-MSCs perfectly home to the damaged ovaries, enhanced ovarian follicle pool, and preserved the ovarian function manifested by restoring serum estradiol and follicle stimulating hormone levels, besides, rescuing the fertility outcomes of irradiated rats. These events have been associated with inhibiting ovarian apoptosis (Bax/Bcl2, caspase 3) and enhancing proliferation (PCNA). Interestingly, BM-MSCs reversed the inhibition of ovarian FOXO3 expression induced by radiation which resulted in increased primordial follicles stock. Moreover, BM-MSCs recovered the suppressed folliculogenesis process induced by radiation through upregulating FOXO1, GDF-9, and Fst genes expression accompanied by downregulating TGF-β which enhanced granulosa cells proliferation and secondary follicle development. Mechanistically, BM-MSCs miRNAs epigenetically upregulate Wnt/β-catenin and Hippo signaling pathways which are implicated in ovarian follicles growth and maturation. Therefore, BM-MSCs presented a ray of hope in the treatment of radiation-associated POF through genetic and epigenetic modulation of the integrated TGF-β, Wnt/β-catenin, and Hippo pathways which control apoptosis, proliferation, and differentiation of ovarian follicles.

Review of psychological stress on oocyte and early embryonic development in female mice

Psychological stress can cause adverse health effects in animals and humans. Accumulating evidence suggests that psychological stress in female mice is associated with ovarian developmental abnormalities accompanied by follicle and oocyte defects. Oocyte and early embryonic development are impaired in mice facing psychological stress, likely resulting from hormone signalling disorders, reactive oxygen species (ROS) accumulation and alterations in epigenetic modifications, which are primarily mediated by the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-ovarian (HPO) axes. The present evidence suggests that psychological stress is increasingly becoming the most common causative factor for female subfertility. Here, we review recent progress on the impact of psychological stress on female reproduction, particularly for oocyte and early embryonic development in female mice. This review highlights the connection between psychological stress and reproductive health and provides novel insight on human subfertility.

CUMS Promotes the Development of Premature Ovarian Insufficiency Mediated by Nerve Growth Factor and Its Receptor in Rats

This study aimed to investigate whether chronic unpredictable mild stress (CUMS) affects follicular development in ovaries through the nerve growth factor (NGF)/high affinity nerve growth factor receptor, the Tropomyosin-related kinase A (TrkA) receptor, mediated signaling pathway and to reveal the relationship between chronic stress and premature ovarian insufficiency (POI) development. In this experiment, a CUMS rat model was constructed. It was found that serum estradiol (E2), anti-Mullerian hormone (AMH), and gonadotropin-releasing hormone (GnRH) levels decreased, while follicle-stimulating hormone (FSH) levels increased. The expression of NGF, TrkA, p75, and FSHR in ovarian tissue decreased significantly. The expression levels of TrkA and p75 protein in ovarian stroma and small follicles were observed by an immunofluorescence assay. In addition, the numbers of small follicles were significantly reduced. The expression of TrkA, p75, and FSHR in CUMS ovarian tissue was upregulated by exogenous NGF in vitro. Furthermore, after treatment with NGF combined with FSH, E2 secretion in ovarian tissue culture supernatant of CUMS rats also increased significantly. Therefore, CUMS downregulates NGF and TrkA and promotes the occurrence of POI in rats. Exogenous NGF and FSH can upregulate the NGF receptor, E2, and AMH in vitro, and improve the rat ovarian function. Future studies may associate these results with female population.

Chaiyu-Dixian Formula Exerts Protective Effects on Ovarian Follicular Abnormal Development in Chronic Unpredictable Mild Stress (CUMS) Rat Model

Background

Chronic stress has been known to impair the female reproductive function, but the mechanism remains to be further investigated. Chaiyu-Dixian Formula (CYDXF) has been reported to regulate human endocrine disorders clinically. However, whether this formula can affect chronic stress-induced ovarian follicular development is not clear.

Aim of the study

To examine effects of CYDXF on follicular development and explore possible mech anisms in a chronic unpredictable mild stress (CUMS) model.

Materials and Methods

Adult female rats were randomly divided into 5 groups control group, CUMS group (saline treatment), CUMS+Estradiol (E₂) (0.1 mg/kg) group, CUMS+CYDXF (2.73 g/kg) group, and CUMS+CYDXF (5.46 g/kg) group. Body weights and behavioral tests were documented. Serum hormone levels were determined by enzyme-linked immunosorbent assay (ELISA). Western blotting was used to detect the protein levels in the PI3K/Akt pathway and brain-derived neurotrophic factor (BDNF). The follicles were analyzed and classified according to their morphological characterization.

Results

CYDXF relieved depression-like behaviors and ameliorated the abnormality in rat estrous cycle within the rat model of CUMS. Moreover, CYDXF could regulate endocrine disorders, increase the proportion of antral follicles as well as decrease the proportion of follicular atresia, which suggested that CYDXF could alleviate abnormal follicular development and improve overall ovarian function. Furthermore, CYDXF also activated the BDNF-mediated PI3K/Akt signaling pathway.

Conclusions

CYDXF (at dose of both 2.73 and 5.46 g/kg) attenuated chronic stress-induced abnormal ovarian follicular development by relieving depression-like behaviors and improving ovarian function through partly the regulation of the BDNF-mediated PI3K/Akt pathway.

Optimization of food deprivation and sucrose preference test in SD rat model undergoing chronic unpredictable mild stress

BACKGROUND

The chronic unpredictable mild stress (CUMS) model has long been considered the best model for exploring the pathophysiological mechanisms underlying depression. However, there are no widely recognised standards for strategies for modeling and for behavioral testing. The present study aimed to optimize the protocols for food deprivation and the sucrose preference test (SPT) for the CUMS model.

METHODS

We first evaluated the effects of different long periods of food deprivation on the body weight of Sprague Dawley (SD) rats by testing food deprivation for 24 hours (8:00-8:00+), food deprivation for 12 hours during the daytime (8:00-20:00) and food deprivation for 12 hours at night (20:00-8:00+). Next, we established a SD rat CUMS model with 15 different stimulations, and used body weight measurement, SPT, forced swim test (FST), open field test (OFT) and Morris water maze (MWM) test to verify the success of the modeling. In the SPT, consumption of sucrose and pure water within 1 and 12 hours was measured.

RESULTS

Twelve hours of food deprivation during the daytime (8:00-20:00) had no effect on body weight, while 12 hours of food deprivation at night (20:00-8:00+) and 24 hours of food deprivation (8:00-8:00+) significantly reduced the mean body weight of the SD rats. When SPT was used to verify the successful establishment of the CUMS rat model, sucrose consumption measured within 12 hours was less variable than that measured within 1 hour.

CONCLUSIONS

Twelve hours of food deprivation in the daytime (8:00-20:00) may be considered a mild stimulus for the establishment of a CUMS rat model. Measuring sucrose consumption over 12 hours is recommended for SPT.

Umbilical Cord Mesenchymal Stem Cell Transplantation Prevents Chemotherapy-Induced Ovarian Failure via the NGF/TrkA Pathway in Rats

Chemotherapy leads to a loss of fertility and reproductive endocrine function, thereby increasing the risk of premature ovarian failure (POF). Studies have suggested that the transplantation of mesenchymal stem cells could inhibit apoptosis in ovarian granulosa cells and improve follicular development. In the present study, the effects of human umbilical cord mesenchymal stem cell (UCMSC) transplantation on ovarian function after ovarian damage caused by chemotherapy and the mechanism underlying these effects were investigated. POF model rats were obtained by the intraperitoneal injection of cyclophosphamide, and cultured UCMSCs were transplanted by tail vein injection. Serum estrogen, follicle-stimulating hormone, gonadotropin releasing hormone, and anti-Mullerian hormone levels were detected by ELISA. Folliculogenesis was evaluated by histopathological examination. The expression levels of nerve growth factor (NGF), high affinity nerve growth factor receptor (TrkA), follicle-stimulating hormone receptor (FSHR), and caspase-3 were evaluated by western blotting and RT-qPCR. The natural reproductive capacity was assessed by pregnant rate and numbers of embryos. The results indicated that UCMSC transplantation recovered disturbed hormone secretion and folliculogenesis in POF rats. NGF and TrkA levels increased, while FSHR and caspase-3 decreased. The pregnancy rate of POF rats was improved. Therefore, UCMSCs could reduce ovarian failure due to premature senescence caused by chemotherapy, and the NGF/TrkA signaling pathway was involved in the amelioration of POF.