Evaluation of an alternative heterotopic transplantation model for ovarian tissue to test pharmaceuticals improvements for fertility restoration

Ovarian tissue cryopreservation and transplantation as a natural means to delay menopause

Ovarian tissue cryopreservation and transplantation (OTCT) offers hope for preserving fertility and endocrine functions in patients undergoing gonadotoxic treatments. Advancements in techniques for the procedure have transformed OTCT from an experimental procedure into a viable option. There is a growing interest in utilizing OTCT to delay menopause and alleviate associated health issues. Menopausal transition affects women globally, leading to symptoms and long- term health risks. OTCT has the potential to restore endocrine functions, reducing menopause-related symptoms while mitigating health consequences such as osteoporosis and cardiovascular diseases. Although the use of OTCT for delaying menopause is not clinically proven, the discussion around shows potential for future utilization. In essence, the remarkable advancements in OTCT have bestowed upon us the ability to safeguard fertility and sustain the delicate endocrine functions of the ovaries. However, it is the tantalizing prospect of utilizing this technique to postpone menopause and alleviate its associated symptoms that truly captivates the imagination. Further research is imperative to substantiate the clinical efficacy of OTCT; nonetheless, its potential in menopausal therapy is both promising and warrants comprehensive exploration. This review highlights advancements and the feasibility of OTCT to postpone menopause as an alternative approach to currently used conventional menopause therapy methods.

Heterotopic ovarian allotransplantation in a caprine model: Effects of implant site on morphological parameters

This study aimed to investigate a new implantation site (intra-auricular subcutaneous - IA) compared to intramuscular (IM) in the cervical portion (cervical splenius muscle) of the neck for ovarian transplantation in goats. Morphological aspects of the implant, follicular activation and morphology, and type I and III collagen deposits of the transplanted tissue were evaluated. Four fragments of the ovarian cortex were allotransplanted at the IA and IM sites in all goat recipients and recovered 7 (IA-7; IM-7) or 15 (IA-15; IM-15) days later and submitted to histological analysis. Two fragments/animal were separated for the fresh control (FC) group. There was a higher percentage of normal and developing primordial follicles at the IA-7 site (P < 0.05) compared to the other treatments, with similar values to the fresh control. Type I and III collagen fibers differed between the groups (P < 0.05), showing a considerable decrease in type I collagen fibers at the IA-7 site compared to the FC. However, the IM-7 and IA-15 sites showed higher values of type I collagen fibers, showing similarity to the FC. Therefore, we conclude that the IA site in goats is an effective site for ovarian tissue transplantation, as it is easily accessible, low invasive and has presented satisfactory rates of morphology and follicular activation.

Melatonin and ovarian tissue transplantation: Current frontiers in research

The progress achieved in anticancer therapy in recent years has been paralleled by an increase in the survival of women with cancer globally. Nonetheless, the gonadotoxic impact of anticancer drugs has led to ovarian failure in treated women. While there are documented cases of successful ovarian tissue transplants resulting in restored fertility and childbirth, challenges persist, including suboptimal functional recovery and limited graft lifespan. Melatonin, an inert hormone primarily secreted by the mammalian pineal gland, exhibits diverse physiological functions, including antioxidative, anti-inflammatory, anti-apoptotic, and angiogenesis-regulating properties. Consequently, researchers have explored melatonin as a modulator to enhance graft function recovery in ovarian transplantation experiments, yielding promising outcomes. This review examines the relevant literature, consolidating findings that underscore the positive effects of melatonin in safeguarding the morphology and structure of transplanted ovarian tissues, facilitating graft function recovery, and extending lifespan. The amassed evidence supports the consideration of melatonin as a prospective protective agent for human ovarian tissue transplantation in the future.

Effects of different subcutaneous sites on heterotopic autotransplantation of canine ovarian tissue

Ovarian tissue transplantation makes it possible to restore fertility; however, the success of this technique depends on the transplant region used. Therefore, this study aimed to evaluate the effect of two subcutaneous regions on canine ovarian transplantation, pinna (Pi) and neck (Ne), for 7 and 15 days. Ovaries collected by ovariosalpingohysterectomy were fragmented using a punch device. Fresh fragments were fixed, and the others were immediately grafted onto the animal itself in the Pi and Ne regions for 7 and 15 days. Recovered fragments were evaluated for histology (morphology, development and stromal density), picrosirius (collagen fibers), and immunohistochemistry (fibrosis and cell proliferation). The results showed that follicular normality rates were lower in Pi-7 (78%) vs. control (90%) and Pi-15 (86%), similar in Ne-7 (92%) and superior in Ne-15 (97%) compared to the control, with the effect of the region Ne (94%) superior (P < 0.05) to Pi (82%). Stromal density reduced in both regions vs. control but was similar within 15 days. Fragments from both regions showed higher fibronectin labeling and deposition of type I and lower type III collagen fibers (P < 0.05) vs. control. Proliferation rates in Ne-7 were higher (P < 0.05) than in control, and Pi-15 was higher (P < 0.05) than Ne-15. In conclusion, the pinna may be a region with greater potential than the neck after a 15-day autotransplantation of canine ovarian tissue.

Advances in the mechanisms related to follicle loss after frozen-thawed ovarian tissue transplantation

Ovaries are important reproductive and endocrine organs in women. Ovarian tissue cryopreservation and transplantation technology can not only solve the fertility problems of patients, but also may improve female endocrine problems. This is particularly important for patients in urgent need of radiotherapy and chemotherapy, and for women with prepubertal malignant tumors. However, follicle loss after freeze-thawing is a key challenge for effective ovarian tissue transplantation and leads to poor transplant outcomes. Therefore, it is crucial to elucidate the mechanisms underlying follicle loss after transplantation. This paper reviews current research on the mechanisms of follicle loss after frozen-thawed ovarian tissue transplantation, including the activation, apoptosis, and pyroptosis mechanisms of primordialfollicles. Further, it highlights the requirement of more experimental studies for improving ovarian tissue transplantation methods.

The mTOR Inhibitor Rapamycin Counteracts Follicle Activation Induced by Ovarian Cryopreservation in Murine Transplantation Models

Background and Objectives: Ovarian tissue cryopreservation followed by autotransplantation (OTCTP) is currently the only fertility preservation option for prepubertal patients. Once in remission, the autotransplantation of frozen/thawed tissue is performed when patients want to conceive. A major issue of the procedure is follicular loss directly after grafting mainly due to follicle activation. To improve follicular survival during the OTCTP procedure, we inhibited the mTOR pathway involved in follicle activation using rapamycin, an mTOR inhibitor. Next, we compared two different in vivo models of transplantation: the recently described non-invasive heterotopic transplantation model between the skin layers of the ears, and the more conventional and invasive transplantation under the kidney capsule. Materials and Methods: To study the effects of adding rapamycin during cryopreservation, 4-week-old C57BL/6 mouse ovaries, either fresh, slow-frozen, or slow-frozen with rapamycin, were autotransplanted under the kidney capsule of mice and recovered three weeks later for immunohistochemical (IHC) analysis. To compare the ear with the kidney capsule transplantation model, fresh 4-week-old C57BL/6 mouse ovaries were autotransplanted to either site, followed by an injection of either LY294002, a PI3K inhibitor, vehicle control, or neither, and these were recovered three weeks later for IHC analysis. Results: Rapamycin counteracts cryopreservation-induced follicle proliferation, as well as AKT and mTOR pathway activation, in ovaries autotransplanted for three weeks under the kidney capsule of mice. Analyses of follicle proliferation, mTOR activation, and the effects of LY294002 treatment were similar in transplanted ovaries using either the ear or kidney capsule transplantation model. Conclusions: By adding rapamycin during the OTCTP procedure, we were able to transiently maintain primordial follicles in a quiescent state. This is a promising method for improving the longevity of the ovarian graft. Furthermore, both the ear and kidney capsule transplantation models were suitable for investigating follicle activation and proliferation and pharmacological strategies.

Medical Grade Honey as a Promising Treatment to Improve Ovarian Tissue Transplantation

Ovarian tissue cryopreservation is a female fertility preservation technique that presents major challenges for the maintenance of follicular viability after transplantation. The aim of this study was to evaluate and compare the application of L-Mesitran Soft®, a product containing 40% medical grade honey (MGH), with other strategies to improve ovarian grafts' viability. For this purpose, bovine ovarian tissue was vitrified, warmed and randomly assigned to culture groups: (1) control, (2) MGH 0.2% in vitro, (3) MGH in vivo (direct application in the xenotransplantation), (4) vascular endothelial growth factor (VEGF 50 ng/mL) and (5) vitamin D (100 Nm), during a 48 h period. A sixth group (6) of fragments was thawed on transplantation day and was not cultured. The tissue was xenotransplanted into immunodeficient (Rowett nude homozygous) ovariectomized rats. Grafts were analyzed 48 h after culture, and 7 and 28 days after transplantation. The tissue was subjected to histological and immunohistochemical analysis. Treatments using MGH showed the highest angiogenic and cell proliferation stimulation, with cellular apoptosis, within a healthy cellular turnover pathway. In conclusion, MGH should be considered as a potentially effective and less expensive strategy to improve ovarian tissue transplantation.