Expression of inhibitor proteins that control primordial follicle reserve decreases in cryopreserved ovaries after autotransplantation

Recombinant anti-Mullerian hormone treatment attenuates primordial follicle loss after ovarian cryopreservation and transplantation

PURPOSE

The foremost drawback of ovarian tissue cryopreservation and re-transplantation (OTCT) technique is the rapid loss of the primordial follicle (PF) pool. In recent studies, we have demonstrated that post-transplantation burnout of the PFs occurs due to the altered expression of the activatory and inhibitory proteins that control PF reserve, and rapamycin prevented it.

METHODS

Here, we investigated whether anti-Mullerian hormone administration in the bilateral oophorectomy and transplantation group and internal AMH in the unilateral oophorectomy and transplantation group protect follicle reserve by regulating the expression of the molecules that control follicle growth after OTCT in mice.

RESULTS

After 14 days of OTCT, PF reserve is significantly reduced in both unilateral oophorectomy and transplantation and bilateral oophorectomy and transplantation groups, while anti-Mullerian hormone treatment attenuates PF loss after bilateral oophorectomy and transplantation. The expression of KitL, Bmp-15, and p27 decreased after unilateral oophorectomy and transplantation and bilateral oophorectomy and transplantation, yet recombinant anti-Mullerian hormone treatment did not restore the expression of these proteins in the BLO-T group.

CONCLUSION

Exogenous recombinant anti-Mullerian hormone administration in the BLO-T group preserved the expressions of Tsc1 and Gdf-9 in PF and p-s6k and Gdf-9 in growing follicles after OTCT. Nonetheless, recombinant anti-Mullerian hormone administration did not affect granulosa cell proliferation and death rates in the growing follicles. These findings suggest a novel hormonal replacement strategy for fertility preservation by restoring anti-Mullerian hormone to regulate Tsc1 and p-s6k, thereby linking this hormone with the mTOR pathway and Gdf-9 signaling.

Pharmacological inhibition of the PI3K/PTEN/Akt and mTOR signalling pathways limits follicle activation induced by ovarian cryopreservation and in vitro culture

BACKGROUND

Cryopreservation and transplantation of ovarian tissue (OTCTP) represent a promising fertility preservation technique for prepubertal patients or for patients requiring urgent oncological management. However, a major obstacle of this technique is follicle loss due to, among others, accelerated recruitment of primordial follicles during the transplantation process, leading to follicular reserve loss in the graft and thereby potentially reducing its lifespan. This study aimed to assess how cryopreservation itself impacts follicle activation.

RESULTS

Western blot analysis of the PI3K/PTEN/Akt and mTOR signalling pathways showed that they were activated in mature or juvenile slow-frozen murine ovaries compared to control fresh ovaries. The use of pharmacological inhibitors of follicle signalling pathways during the cryopreservation process decreased cryopreservation-induced follicle recruitment. The second aim of this study was to use in vitro organotypic culture of cryopreserved ovaries and to test pharmacological inhibitors of the PI3K/PTEN/Akt and mTOR pathways. In vitro organotypic culture-induced activation of the PI3K/PTEN/Akt pathway is counteracted by cryopreservation with rapamycin and in vitro culture in the presence of LY294002. These results were confirmed by follicle density quantifications. Indeed, follicle development is affected by in vitro organotypic culture, and PI3K/PTEN/Akt and mTOR pharmacological inhibitors preserve primordial follicle reserve.

CONCLUSIONS

Our findings support the hypothesis that inhibitors of mTOR and PI3K might be an attractive tool to delay primordial follicle activation induced by cryopreservation and culture, thus preserving the ovarian reserve while retaining follicles in a functionally integrated state.

The protective effects of rapamycin pretreatment on ovarian damage during ovarian tissue cryopreservation and transplantation

Ovarian tissue cryopreservation and transplantation (OCT) has been sufficiently proven effective and feasible to preserve fertility for women especially for prepubertal girls suffering from cancer with radiotherapy and chemotherapy. However, grafts' survival, significant follicle loss and a delay of revascularization during OCT still need to be resolved no matter what kind of cryopreserved method being used. Different from previous reports about additives treatment on recipient after ovarian transplantation, we here report a new vitrification protocol with pretreatment of rapamycin, an inhibitor of the mTOR signaling pathway. The rapamycin treatment has been shown to inhibit the activation of mTOR signaling pathway in fresh thawed ovaries or in ovaries shortly grafted in the recipient mice. Further study revealed increased percentage of primordial follicles and reduced apoptosis after 5 days of transplantation. Long-term follow up of ovarian development demonstrated the increase of ovarian survival rates in rapamycin treated ovaries after 2 weeks of transplantation. Although follicular development showed a slight delay with more secondary and early antral follicles found in rapamycin treated ovaries, follicular development was not blocked as manifested by the ovarian morphology after 5 weeks of transplantation. Taken together, the pretreatment of rapamycin before vitrification is a good method for clinical application with its effectiveness on preserving follicle reserve and promoting ovarian survival during the process of OCT.

Implications of Nonphysiological Ovarian Primordial Follicle Activation for Fertility Preservation

In recent years, ovarian tissue cryopreservation has rapidly developed as a successful method for preserving the fertility of girls and young women with cancer or benign conditions requiring gonadotoxic therapy, and is now becoming widely recognized as an effective alternative to oocyte and embryo freezing when not feasible. Primordial follicles are the most abundant population of follicles in the ovary, and their relatively quiescent metabolism makes them more resistant to cryoinjury. This dormant pool represents a key target for fertility preservation strategies as a resource for generating high-quality oocytes. However, development of mature, competent oocytes derived from primordial follicles is challenging, particularly in larger mammals. One of the main barriers is the substantial knowledge gap regarding the regulation of the balance between dormancy and activation of primordial follicles to initiate their growing phase. In addition, experimental and clinical factors also affect dormant follicle demise, while the mechanisms involved remain largely to be elucidated. Moreover, most of our basic knowledge of these processes comes from rodent studies and should be extrapolated to humans with caution, considering the differences between species in the reproductive field. Overcoming these obstacles is essential to improving both the quantity and the quality of mature oocytes available for further fertilization, and may have valuable biological and clinical applications, especially in fertility preservation procedures. This review provides an update on current knowledge of mammalian primordial follicle activation under both physiological and nonphysiological conditions, and discusses implications for fertility preservation and priorities for future research.

Altered expression of activator proteins that control follicle reserve after ovarian tissue cryopreservation/transplantation and primordial follicle loss prevention by rapamycin

PURPOSE

We investigated whether expression of activator proteins that control follicle reserve and growth change after ovarian tissue vitrification and re-transplantation. Moreover, we assessed whether inhibition of mTOR signaling pathway by rapamycin would protect primordial follicle reserve after ovarian tissue freezing/thawing and re-transplantation.

METHODS

Fresh control, frozen/thawed, fresh-transplanted, frozen/thawed and transplanted, rapamycin/control, rapamycin fresh-transplanted, and rapamycin frozen-thawed and transplanted groups were established in rats. After freezing and thawing process, two ovaries were transplanted into the back muscle of the same rat. After 2 weeks, grafts were harvested, fixed, and embedded into paraffin block. Normal and atretic primordial/growing follicle count was performed in all groups. Ovarian tissues were evaluated for the dynamic expressions of Gdf-9, Bmp-15, KitL, Lif, Fgf-2, and p-s6K using immunohistochemistry, and H-score analyses were done.

RESULTS

Primordial follicle reserve reduced almost 50% after ovarian tissue re-transplantation. Expression of Gdf-9 and Lif increased significantly in primordial and growing follicles in frozen-thawed, fresh-transplanted, and frozen/thawed and transplanted groups, whereas expression of Bmp-15, KitL, and Fgf-2 decreased in primordial follicles. Freezing and thawing of ovarian tissue solely significantly increased p-s6K expression in primordial follicles, and on the other hand, suppression of mTORC1 pathway using rapamycin preserved the primordial follicle pool.

CONCLUSION

Altered expressions of activator proteins that regulate primordial follicle reserve and growth may lead to primordial follicle loss and rapamycin treatment can protect ovarian reserve after ovarian tissue cryopreservation/transplantation.

Hypothermic machine perfusion after static cold storage improves ovarian function in rat ovarian tissue transplantation

OBJECTIVE

This study was performed to investigate the effect of hypothermic machine perfusion (HMP) after cold storage (CS) on ovarian transplantation.

METHODS

Rats aged 8-10 weeks were used as the donors and recipients for allotransplantation. Eighteen donor rats were divided into three groups: the fresh control (n = 6), cold storage (CS; n = 6), and hypothermic machine perfusion (HMP; n = 6) groups. The preservation solution contained Dulbecco's modified Eagle's medium/Ham's F-12 (1:1, v/v), 10% fetal bovine serum, 10 μg/ml insulin, 10 μg/ml transferrin, and 50 mIU/ml follicle-stimulating hormone (FSH). The donor ovaries in the CS and HMP groups were excised and then respectively subjected to 4 h of CS and 2 h of CS combined with 2 h of HMP at 4 °C, and then transplanted beneath the recipient's left renal capsule. At 7 days after transplantation, the ovaries were removed and blood samples were obtained for histological analysis, immunohistochemistry for CD31 and Ki67, and serum anti-Mullerian hormone (AMH) level estimation.

RESULTS

The HMP group showed significant increases in serum AMH and CD31-positive areas when compared to these values in the CS group (P < 0.05). However, no differences were noted in the total number of follicles or the Ki67-positive areas among the three groups.

CONCLUSION

Hypothermic machine perfusion after static cold storage is more effective than static CS alone for the short-term preservation of whole ovaries during transport. Whole ovary transplantation with vascular pedicle is our future research direction. Graphical Abstract The black rectangle in the figure shows the place where ligation and disconnection are required, the black dotted line shows the place where vascular forceps are used to clamp, and the black circle shows the place where the cannula is inserted This diagram was made for reviewers to understand more intuitively how my hypothermia mechanical perfusion model was built. Organs obtained in this way can be used for subsequent perfusion and whole ovarian transplantation.

State of the Art in Fertility Preservation for Female Patients Prior to Oncologic Therapies

Quality of life improvement stands as one of the main goals of the medical sciences. Increasing cancer survival rates associated with better early detection and extended therapeutic options led to the specific modeling of patients’ choices, comprising aspects of reproductive life that correlated with the evolution of modern society, and requires better assessment. Of these, fertility preservation and ovarian function conservation for pre-menopause female oncologic patients pose a contemporary challenge due to procreation age advance in evolved societies and to the growing expectations regarding cancer treatment. Progress made in cell and tissue-freezing technologies brought hope and shed new light on the onco-fertility field. Additionally, crossing roads with general fertility and senescence studies proved highly beneficial due to the enlarged scope and better synergies and funding. We here strive to bring attention to this domain of care and to sensitize all medical specialties towards a more cohesive approach and to better communication among caregivers and patients.

Heterotopic ovarian allotransplantation in goats: Preantral follicle viability and tissue remodeling

An appropriate implantation site favors angiogenesis and avoids ovarian tissue damage after tissue grafting. The objective of this study was to evaluate the effects of intramuscular (IM) and subcutaneous (SC) sites for ovarian grafts in goats by evaluating follicular morphology and activation, preantral follicle and stromal cell densities, tissue DNA fragmentation, collagen types I and III depositions, and graft revascularizations. Ovarian cortical tissue was transplanted in IM or SC sites and recovered 7 or 15 days post-transplantation. There was a greater percentage of developing follicles and lesser follicular and stromal cell densities in all grafted tissues as compared to ovarian tissues of the control group. The stromal cell density and percentage of normal follicles were positively associated. At 15 days post-transplantation, tissues at the SC and IM sites had similar amounts of DNA fragmentation and type III collagen content. In contrast, tissues at the SC, as compared with IM site, had greater abundances of collagen type I. Furthermore, there was a positive association between collagen type I and percentage of morphologically normal follicles post-transplantation. In addition to a marked decrease in follicular density 15 days post-transplantation in ovarian grafts at the SC and IM sites, low percentages of normal follicles and follicular activation were observed similarly in both transplantation sites. There were also positive associations of stromal cell density and abundance of type I collagen fibers with the percentage of intact follicles in grafted ovarian tissues.

The effects of magnesium sulfate on cyclophosphamide-induced ovarian damage: Folliculogenesis

Cyclophosphamide (CYP) is one of the alkylating chemotherapeutic agents and its adverse effects on folliculogenesis in the ovary are well-known due to the previous scientific research on this topic. Magnesium has various effects in organisms, including catalytic functions on the activation and inhibition of many enzymes, and regulatory functions on cell proliferation, cell cycle, and differentiation. In this study, the effects of magnesium sulfate (MgSO₄) on CYP induced ovarian damage were investigated. Immature Wistar-Albino female rats of 28-days were treated with pregnant mare serum gonadotrophin (PMSG) to develop the first generation of preovulatory follicles. Rats of the experimental groups were then treated with either CYP (100 mg/kg, i.p) and MgSO₄ (270 mg/kg loading dose; 27 mg/kg maintenance doseX12, i.p) solely or in combination. Following in-vivo 5-bromo-2-deoxyuridine (BrdU) labeling, animals were sacrificed and ovaries were embedded in paraffin and Epon. In the ovaries, added to the evaluation of general morphology and follicle count; BrdU and TUNEL-labeling, cleaved caspase-3 and p27 (cyclin-dependent kinase inhibitor) staining was also performed immunohistochemically and an ultrastructural evaluation was performed by transmission electron microscopy (TEM). The number of primordial follicles were decreased and multilaminar primary and atretic follicles were increased in CYP group. After MgSO₄ treatment, while primordial follicle pool were elevated, the number of atretic follicles were decreased. Additionally, decreased BrdU-labeling, increased cleaved caspase 3 immunoreactivity and increased TUNEL labeling were observed in CYP group. In CYP treated animals, observations showed that while MgSO₄ administration caused no alterations in BrdU proliferation index and caspase-3 immunoreactivity, it significantly reduced the TUNEL labeling. It was also observed that, while p27 immunoreactivity significantly increased in the nuclei of granulosa and theca cells in the CYP group; MgSO₄ treatment significantly reduced these immunoreactivities. The ultrastructural observations showed frequent apoptotic profiles in granulosa and theca cells in both early and advanced stages of follicles in the CYP group and the MgSO₄ treatment before the CYP application led to ultrastructural alleviation of the apoptotic process. In conclusion, our data suggest that MgSO₄ may provide an option of pharmacologic treatment for fertility preservation owing to the beneficial effects of on chemotherapy-induced accelerated follicular apoptotic process, and the protection of the primordial follicle pool.