hUMSC-derived exosomes alleviate follicular interstitial cell autophagy by let-7a-5p/AMPK/mTOR axis in POI rats

Abstract

Background  One major factor contributing to infertility in women of childbearing age is premature ovarian insufficiency (POI). Exosomes produced from human umbilical cord mesenchymal stem cells (hUMSC-Exos) have drawn a lot of attention lately as a potential treatment for ovarian dysfunction brought on by POI. However, its therapeutic mechanism is still unclear and needs further exploration. Methods  POI model was established by intraperitoneal injection of cyclophosphamide (CTX) in female Wistar rats. These POI rats were treated with hUMSC-Exos for one week. In addition to in vivo experiments, in vitro POI models were also established. In vitro experiments, theca interstitial cells (TICs) treated with CTX were exposed to normal as well as let-7a-5p inhibitory hUMSC-Exos. The ovary structure, morphology, endocrine function, and reproductive ability of POI rats were observed by H&E staining and ELISA. Western blot, immunofluorescence staining (IF), and quantitative real-time polymerase chain reaction (qRT-PCR) were used to evaluate the autophagy-related indexes in ovary and TICs of POI rats in each group. Results  CTX induced abnormalities of ovarian morphology, structure, endocrine, and reproductive function in rats, and accompanied by autophagy of TICs. Notably, hUMSC-Exos diminishes ovarian structural and functional damage in POI rats and TICs autophagy via targeting the AMPK/mTOR pathway. Furthermore, downregulating let-7a-5p in hUMSC-Exos weakened their ability to prevent TICs autophagy. Conclusions  Overall, the findings suggested that hUMSC-Exos improves ovarian function in POI rats by inhibiting TICs autophagy via the let-7a-5p/AMPK/mTOR pathway. Our study provided further evidence that POI patients can benefit from hUMSC-Exos-mediated therapy.

1. Introduction

Premature ovarian insufficiency (POI) is a disorder that causes ovarian malfunction. Symptoms of this disease include infrequent or missing menstruation, infertility, and menopause [1]. Recently, research has revealed that damage to theca interstitial cells (TICs) is a major cause of POI [2, 3]. Mesenchymal stem cells (MSCs) have attracted a lot of attention as a potential treatment for POI. Our most recent work also discovered that human umbilical cord mesenchymal stem cells (hUMSCs) regulate TICs autophagy and restore ovarian function [4]. However, the exact process by which hUMSCs regulate TICs requires additional investigation.

POI, a major cause of infertility in women of reproductive age, is defined by a reduction in serum estradiol (E2) and anti-Mullerian hormone (AMH) levels and an increase in gonadotropin levels [5]. Research has demonstrated that chemotherapy drugs such as cyclophosphamide (CTX) disrupt immune regulation, cell viability, promote inflammation, and lead to ovarian microenvironment imbalance, ultimately inducing POI [6, 7]. Furthermore, investigations have found that POI is also accompanied by ovarian tissue fibrosis, oxidative stress, and cell death [8, 9]. Recently, Dou et al. determined that granulosa cells (GCs) autophagy triggered by the Phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/Mammalian target of rapamycin (mTOR) signaling pathway is a plausible biological mechanism for causing POI [10]. Autophagy is the process by which cells digest and recycle proteins and organelles to maintain intracellular balance [11]. In general, autophagy protects cells, nevertheless, interruption of autophagy pathways or excessive autophagic flux usually results in cell death [12]. Our latest research has also revealed that TICs, the important cells that control follicular development, are particularly susceptible to autophagy dysregulation in POI, highlighting their role as a therapeutic target.