Rapamycin Prevents cyclophosphamide-induced Over-activation of Primordial Follicle pool through PI3K/Akt/mTOR Signaling Pathway in vivo

Abstract

BackgroundPrimordial follicular depletion has thought to be a common adverse effect of chemotherapy especially for female of reproductive age. The study aimed to evaluate the protective effect of rapamycin on the primordial follicles and its potential mechanism for patients receiving chemotherapy.Methods8-week old BALB/c female mice were randomly assigned into four groups (control; rapamycin; cyclophosphamide; and rapamycin combined with cyclophosphamide). Hematoxylin staining, immunohistochemical, TUNEL, western blotting and ELISA were employed to assess inter-group differences using Student’s t-test and Mann-Whitney test.ResultsCyclophosphamide depleted the follicular reserve and induced the phosphorylation of the key proteins of PI3K/Akt/mTOR pathway in mice in a dose-dependent manner. Co-treatment with rapamycin significantly reduced primordial follicle loss at all cyclophosphamide dose groups and prevent the follicle growth wave caused by cyclophosphamide treatment (P < 0.05). TUNEL staining showed that no apoptosis occured in the primordial follicles in all groups and fewer apoptosis in large growing follicles were observed in ovaries from rapamycin + cyclophosphamide group compared to that received cyclophosphamide alone. Serum anti-Müllerian hormone (AMH) was significantly reduced in cyclophosphamide alone group, in contrast to the normal level in rapamycin + cyclophosphamide group. Compared to p-Akt/Akt and p-mtor/mtor, p-rps6/rps6 was significantly decreased in rapamycin + cyclophosphamide group (P < 0.05), indicating that rapamycin attenuated the increased level of phosphorylation of rpS6 after cyclophosphamide treatment.ConclusionsRapamycin can prevent the primordial follicle activation induced by cyclophosphamide through PI3K/Akt/mTOR signaling pathway and thus plays a role in preserving the follicle pool. These results suggest that rapamycin may be an effective protection for ovarian function during chemotherapy, which means a new nonsurgical application for protection of ovarian reserve and prevention of POF.

AMH prevents primordial ovarian follicle loss and fertility alteration in cyclophosphamide‐treated mice

“…Currently, in the field of oncofertility, efforts are constantly made to improve existing fertility preservation techniques and to develop new strategies suitable for patients of whatever age and ovarian reserve status (43). Thus, several "fertoprotectant" molecules, such as rapamycin or melatonin, have been developed and studied to limit chemotherapyinduced ovarian damages in mice (18,19,30,44,45). However, these treatments are involved in cell-death mechanism or in ubiquitous signaling pathways, and they could therefore interfere with the efficacy of treatment or other physiologic mechanisms (19).…”

Suppression of ovarian follicle development by nano TiO2 is associated with TGF‐β‐mediated signaling pathways

“…Phosphatidylinositol 3 kinase (PI3K) is activated by growth factor receptor and G protein‐coupled receptor. In the signaling pathway, activated PI3K stimulates the activity of its downstream protein kinase B (AKT) . AKT regulates cell survival and apoptosis and inhibits the activity of transcription factors of the Forkhead family, thereby suppressing apoptosis, inducing cells to enter the proliferation cycle .…”

“…In the signaling pathway, activated PI3K stimulates the activity of its downstream protein kinase B (AKT). 32 AKT regulates cell survival and apoptosis 36 and inhibits the activity of transcription factors of the Forkhead family, thereby suppressing apoptosis, inducing cells to enter the proliferation cycle. 37 Activated PI3K/AKT may further stimulate the downstream molecule, mTOR, which, in turn, phosphorylates and activates its downstream molecule p70S6K, facilitating its participation in protein synthesis.…”

“…Transforming growth factor‐beta (TGF‐β) family members are clearly involved in regulation of ovarian function and follicular development . In particular, the TGF‐β pathway has been shown to regulate the development and apoptosis of primordial follicles through synergistic effects of PI3K/AKT/mT0R signaling and downstream regulation of the AKT/p70S6K‐rpS6/TSC/mTOR pathway, thus delaying POF …”

“…25 In particular, the TGF-β pathway has been shown to regulate the development and apoptosis of primordial follicles through synergistic effects of PI3K/AKT/mT0R signaling and downstream regulation of the AKT/p70S6K-rpS6/TSC/mTOR pathway, thus delaying POF. [26][27][28][29][30][31][32] We hypothesized that nano TiO 2 interferes with regulation of TGF-β-mediated signaling and expression of members of this pathway, contributing to disruption of ovarian follicle development. To examine this theory, female mice were exposed to different doses of nano TiO 2 (1.25, 2.5, and 5 mg/kg BW) for 60 consecutive days via gavage administration, and the number of primordial, primary, secondary, antral, and atretic follicles and corpus luteum in the ovary were counted under a microscope.…”