Low-dose metronomic delivery of cyclophosphamide is less detrimental to granulosa cell viability, ovarian function, and fertility than maximum tolerated dose delivery in the mouse

Ovarian microenvironment: challenges and opportunities in protecting against chemotherapy-associated ovarian damage

BACKGROUND

Chemotherapy-associated ovarian damage (CAOD) is one of the most feared short- and long-term side effects of anticancer treatment in premenopausal women. Accumulating detailed data show that different chemotherapy regimens can lead to disturbance of ovarian hormone levels, reduced or lost fertility, and an increased risk of early menopause. Previous studies have often focused on the direct effects of chemotherapeutic drugs on ovarian follicles, such as direct DNA damage-mediated apoptotic death and primordial follicle burnout. Emerging evidence has revealed an imbalance in the ovarian microenvironment during chemotherapy. The ovarian microenvironment provides nutritional support and transportation of signals that stimulate the growth and development of follicles, ovulation, and corpus luteum formation. The close interaction between the ovarian microenvironment and follicles can determine ovarian function. Therefore, designing novel and precise strategies to manipulate the ovarian microenvironment may be a new strategy to protect ovarian function during chemotherapy.

OBJECTIVE AND RATIONALE

This review details the changes that occur in the ovarian microenvironment during chemotherapy and emphasizes the importance of developing new therapeutics that protect ovarian function by targeting the ovarian microenvironment during chemotherapy.

SEARCH METHODS

A comprehensive review of the literature was performed by searching PubMed up to April 2024. Search terms included 'ovarian microenvironment' (ovarian extracellular matrix, ovarian stromal cells, ovarian interstitial, ovarian blood vessels, ovarian lymphatic vessels, ovarian macrophages, ovarian lymphocytes, ovarian immune cytokines, ovarian oxidative stress, ovarian reactive oxygen species, ovarian senescence cells, ovarian senescence-associated secretory phenotypes, ovarian oogonial stem cells, ovarian stem cells), terms related to ovarian function (reproductive health, fertility, infertility, fecundity, ovarian reserve, ovarian function, menopause, decreased ovarian reserve, premature ovarian insufficiency/failure), and terms related to chemotherapy (cyclophosphamide, lfosfamide, chlormethine, chlorambucil, busulfan, melphalan, procarbazine, cisplatin, doxorubicin, carboplatin, taxane, paclitaxel, docetaxel, 5-fluorouraci, vincristine, methotrexate, dactinomycin, bleomycin, mercaptopurine).

OUTCOMES

The ovarian microenvironment shows great changes during chemotherapy, inducing extracellular matrix deposition and stromal fibrosis, angiogenesis disorders, immune microenvironment disturbance, oxidative stress imbalances, ovarian stem cell exhaustion, and cell senescence, thereby lowering the quantity and quality of ovarian follicles. Several methods targeting the ovarian microenvironment have been adopted to prevent and treat CAOD, such as stem cell therapy and the use of free radical scavengers, senolytherapies, immunomodulators, and proangiogenic factors.

WIDER IMPLICATIONS

Ovarian function is determined by its 'seeds' (follicles) and 'soil' (ovarian microenvironment). The ovarian microenvironment has been reported to play a vital role in CAOD and targeting the ovarian microenvironment may present potential therapeutic approaches for CAOD. However, the relation between the ovarian microenvironment, its regulatory networks, and CAOD needs to be further studied. A better understanding of these issues could be helpful in explaining the pathogenesis of CAOD and creating innovative strategies for counteracting the effects exerted on ovarian function. Our aim is that this narrative review of CAOD will stimulate more research in this important field.

REGISTRATION NUMBER

Not applicable.

The Role of Cellular Senescence in Cyclophosphamide-Induced Primary Ovarian Insufficiency

Young female cancer patients can develop chemotherapy-induced primary ovarian insufficiency (POI). Cyclophosphamide (Cy) is one of the most widely used chemotherapies and has the highest risk of damaging the ovaries. Recent studies elucidated the pivotal roles of cellular senescence, which is characterized by permanent cell growth arrest, in the pathologies of various diseases. Moreover, several promising senolytics, including dasatinib and quercetin (DQ), which remove senescent cells, are being developed. In the present study, we investigated whether cellular senescence is involved in Cy-induced POI and whether DQ treatment rescues Cy-induced ovarian damage. Expression of the cellular senescence markers p16, p21, p53, and γH2AX was upregulated in granulosa cells of POI mice and in human granulosa cells treated with Cy, which was abrogated by DQ treatment. The administration of Cy decreased the numbers of primordial and primary follicles, with a concomitant increase in the ratio of growing to dormant follicles, which was partially rescued by DQ. Moreover, DQ treatment significantly improved the response to ovulation induction and fertility in POI mice by extending reproductive life. Thus, cellular senescence plays critical roles in Cy-induced POI, and targeting senescent cells with senolytics, such as DQ, might be a promising strategy to protect against Cy-induced ovarian damage.

Ameliorative effect of recombinant human lactoferrin on the premature ovarian failure in rats after cyclophosphamide treatments

This study investigated the effect of recombinant human lactoferrin (rhLF) on the premature ovarian failure (POF) of rats. After cyclophosphamide treatments, the POF rats were divided into the following groups: normal control group (NC), low-dose group (LD), medium-dose group (MD) and high-dose group (HD) of rhLF. After drug administrations, the ovarian indexes and hormonal levels were detected. After follicle number count, the proliferation and apoptosis were analyzed with the expressions of genes related with oogenesis, reactive oxygen species (ROS) production and apoptosis detected, followed by the calculation of oxidative stress and protein expressions. After 4-hydroperoxy cyclophosphamide (4-HC) treatments, the effect of rhLF on the proliferation, ROS production and gene expressions of primary rat granulosa cells (GCs) cultured in vitro were detected. After mating, the fertilities of POF rats were recorded. The result showed that the rhLF administrations up-regulated the ovarian index with the number of developing follicles increased and the decreases of hormonal levels conferred. The Ki-67 intensities of the MD and HD groups were up-regulated with the Tunnel intensities decreased. The rhLF treatments significantly promoted the expression of oogenesis, antioxidant and anti-apoptosis related genes. The expression of Bax and Caspase 3 were decreased with the expression of Bcl-2 up-regulated after rhLF administrations. The in vitro treatments of rhLF effectively conferred the toxicity of 4-HC on primary rat GCs. The fertility assessment showed the rhLF treatments up-regulated the offspring’s’ folliculogenesis, which confirmed the ameliorative role of rhLF on the POF damages via the inhibition of ROS production in GCs.

The protective effects of pretreatment with resveratrol in cyclophosphamide-induced rat ovarian granulosa cell injury: In vitro study

Cyclophosphamide (Cy), a chemotherapeutic agent, is widely used to treat tumoursand is also associated with premature ovarian insufficiency. 4-Hydroperoxycyclophosphamide (4-HC), an active metabolite of Cy, was used for in vitro experiments. Granulosa cells (GCs) are crucial for maintaining follicle development and are also used in reproductive toxicity research in vitro. Resveratrol (Res), a polyphenolic compound, exhibits multiple effects in cells and animal models. To date, whether Res pretreatment has a protective effect on GCs induced by Cy remains unclear. This was an in vitro study, and primary cultures of rat GCs were used. Rat GCs were treated with 4-HC alone, Res + 4-HC or Res + 4-HC + EX527, and GCs survival rates, oxidative stress levels, apoptosis rates and related Sirt1 pathway proteins were evaluated. We demonstrated that 4-HC caused GC damage by increasing oxidative stress, autophagy and apoptosis. Res pretreatment improved 4-HC-induced GC damage by increasing Sirt1 expression, reducing oxidative stress levels and decreasing Beclin1, LC3B, Bax and Caspase-3 levels. Importantly, the addition of EX527, which is a selective inhibitor of Sirt1, reversed the protective effect of Res pretreatment, indicating that Sirt1 may be an important mediator of the protective effect of Res. Taken together, we demonstrated that Res may be a potential drug to improve fertility preservation for patients undergoing chemotherapy.

Transcriptome analysis reveals that cyclophosphamide induces premature ovarian failure by blocking cholesterol biosynthesis pathway

AIMS

The present study aimed to investigate the effects of cyclophosphamide (Cytoxan, CTX) on premature ovarian failure (POF) in mice and its regulatory mechanisms by transcriptome analysis.

MAIN METHODS

Female C57BL/6 mice were treated with a single intraperitoneal injection of 70 mg/kg CTX. Serum levels of estradiol (E₂) and follicle stimulating hormone (FSH) were measured by enzyme-linked immunosorbent assay (ELISA), and follicular structure differences were observed by hematoxylin and eosin (H&E) staining. The main mechanism of POF was investigated by RNA-seq data, protein-protein interaction (PPI) networks and qPCR analysis.

KEY FINDINGS

The serum levels of E₂ were significantly decreased and those of FSH were significantly increased compared to the control group. The ovarian weights of the mice in the CTX group were reduced, and abnormal follicular structures were also observed in the CTX group. The RNA-seq data show that the downregulated genes were related to the cholesterol biosynthesis pathway. The PPI network and qPCR analyses further confirm that the PPAR signaling pathway and the ovarian infertility genes were also involved in blocking the cholesterol biosynthesis pathway. The differences were statistically significant.

SIGNIFICANCE

Our results indicate that CTX may exert its anti-tumor effects by inactivating the cholesterol biosynthesis pathway, and simultaneously reducing the supply of estrogen precursor materials, ultimately leading to the occurrence of POF. Our data provided a preliminary theoretical basis for resolving the clinical toxicity and side effects of CTX.