Comprehensive Review of In Vitro Human Follicle Development for Fertility Restoration: Recent Achievements, Current Challenges, and Future Optimization Strategies

Evaluation of the effect of human testicular cell conditioned media on the in vitro development of follicles from cryopreserved human ovarian cortical pieces. A potential approach for fertility preservation for cancer patients

If in vitro culture conditions could be improved, in vitro growth of cryopreserved ovarian tissue and isolated follicles could become an alternative to ovarian tissue transplantation. This study evaluated two cryopreservation methods, slow cooling and vitrification, and two in vitro culture methods, to determine their effect on the in vitro growth of human ovarian follicles. After warming, the OT pieces (1 × 10 × 3 mm) were cultured in either routine culture medium (DMEM), or DMEM supplemented 50:50 with media previously used for human testicular cell culture (hTCCM) to serve as a source of growth factors. Several parameters were evaluated during culture including follicle recruitment, growth, morphology, diameter, hormone production, and gene expressions (PTEN, BMP-15, PDGF, GDF-9, and GAPDH). The follicular morphology and hormonal secretion were comparable for both cryopreservation methods and both culture methods (P > 0.05). Follicle recruitment was accelerated in the vitrified group, in the presence of hTCCM (P > 0.05). After 7 days of culture, the follicle diameter was greater in the slow/hTCCM compared to the vitrification DMEM group. Similarly only one gene expression profile, BMP-15, in the slow/hTCCM differed significantly from another treatment group (Vit DMEM). At the end of culture (over 21 days), three immature, low-quality oocytes were the achievement. In conclusion, a very quick and easy vitrification protocol gave comparable results to the slow cooling method. We also established that the laboriously prepared hTCCM supplement did not benefit the outcomes. Further work is needed before in vitro maturation of cryopreserved ovarian cortical pieces can be used clinically.

How to Preserve Fertility in Reproductive-Age Women with Cancer

Chemotherapy and radiotherapy, among other gonadotoxic treatments, can significantly affect ovarian reserve and function, potentially leading to premature ovarian insufficiency (POI) and sterility. With the increasing survival rates among young female cancer patients, fertility preservation (FP) has become an essential aspect of cancer care. The decision to pursue FP depends on various factors, including patient age, ovarian reserve, the type of treatment, and its gonadotoxic potential. Several FP strategies are available, including oocyte, embryo, and ovarian tissue cryopreservation. While oocyte and embryo cryopreservation are the gold standard techniques, ovarian tissue cryopreservation and in vitro maturation (IVM) present viable alternatives for patients who cannot undergo ovarian stimulation or for whom stimulation is contraindicated. Despite significant advances within the FP practice, challenges remain in ensuring timely FP counseling, equitable access to services, and optimizing long-term reproductive outcomes. Continued research is needed to refine existing FP techniques, explore innovative approaches, and address ethical considerations in FP decision-making. This review explores current FP options, their clinical applications, and future directions to improve reproductive outcomes in young women undergoing gonadotoxic treatments.

Future perspectives of fertility protection

Reproductive health is of major importance for individuals, for the society and for the health of future generations. This includes physical and medical dimensions as well as psychosocial and ethical ones. Whenever the possibility of starting a family is compromised, either due to an oncological cytotoxic treatment or due to transgender hormone medication with the aim to align their secondary sexual characteristics or other medical or social conditions, one key aspect of reproductive health is fertility protection. However, as a very young field in medicine, there are still many research questions that need to be clarified to provide the best possible treatment for affected people. These include the optimization and safety of cryopreservation processes of germ cells in women, men, transgender people, adolescents and children. Another focus is on psychological care as well as ethical, economic and legal issues. The establishment and development of the center for fertility protection Ulm (FePro-Ulm) will focus on a detailed molecular biological and (epi)genetic understanding of the underlying processes in ovarian tissue, oocytes and sperm to improve and develop new diagnostic and therapeutic approaches. The individual needs of affected people, their partners and families will be evaluated by an interdisciplinary approach. The collaborations within FePro-Ulm will develop preventative and helpful interventions for affected people. In addition, a better awareness of this important topic of reproductive health and fertility protection will be addressed by including participation representatives and strengthen public relation works.

A spotlight on factors influencing the in vitro folliculogenesis of isolated preantral follicles

Female fertility preservation via complete in vitro folliculogenesis is still chimerical. Due to many factors affecting the efficiency of isolation and culture of preantral follicles, the improvement of techniques geared to fertility preservation in higher mammals seems to be at an impasse. We need an objective view of the current stand to understand how to progress further. As such, a survey was conducted to analyze the relative distribution of studies performed in ten mammalian species on preantral follicle culture available on PubMed. Using the bovine as a reference model, we explore some factors influencing data variation that contribute to the difficulty in reproducing studies. While years of research have enabled the recapitulation of folliculogenesis from as modest as the early antral follicle stage ex vivo, in vitro preantral folliculogenesis remains elusive. Herein, we revisit the classical evidence that laid the foundations for understanding preantral folliculogenesis and review the length, breadth, and depth of information that the era of big data has currently levied. Moving forward, we recognize the urgency of synthesizing the multi-disciplinary approaches to mimic folliculogenesis in vitro to achieve a translational landscape of infertility at individual and large-scale conservation levels.

Exploring the Frontiers of Ovarian Tissue Cryopreservation: A Review

Objective: This paper serves as an up-to-date narrative review of the most effective methods and outcomes of ovarian tissue cryopreservation (OTC) with new data comparing this method to oocyte and embryo cryopreservation as well as its utility in restoration of endocrine function. Background: Data on OTC are becoming more available as more patients are achieving cancer remission and choosing to use their cryopreserved tissue to conceive or restore endocrine function. With OTC only recently becoming a non-experimental method of fertility preservation, it is important to evaluate, compare, and optimize current practices to improve live birth outcomes. Methods: A literature search of meta-analyses, systematic reviews, case series, retrospective studies, and randomized control trials was performed using the PubMed database with multiple search terms. Discussion: Current practices and outcomes of OTC remain heterogeneous, though they are becoming more streamlined with the emerging data on successful live births. Multiple aspects of OTC have been studied to optimize protocols, particularly methods of cryopreserving, in vitro maturation, and transplantation. In vitro follicle maturation is a novel application with emerging data on methods and outcomes. OTC is a versatile method not only for fertility preservation but also for hormone restoration as well. With wider usage of OTC, ethical dilemmas will need to be addressed. Conclusions: OTC can be used as fertility preservation for a variety of patients. Recent studies suggest it may be comparable to embryo cryopreservation, but with growing data on live births, comparative studies should continue to be performed. In vitro follicle maturation (IVFM) is a promising application of ovarian tissue harvesting. Data are lacking on cost-effectiveness, patient satisfaction, and morbidity associated with OTC.

Encapsulation of Bovine Primordial Follicles in Rigid Alginate Does Not Affect Growth Dynamics

The only fertility preservation and subsequent restoration option for many patients facing gonadotoxic treatments is ovarian tissue cryopreservation and transplantation. While this process is successful for some, there is significant room for improvement to extend the life of the transplant and to make it safe for patients that may have metastatic disease within their ovarian tissue. We need a deeper understanding of how the physical properties of the ovarian microenvironment may affect folliculogenesis to engineer an environment that supports isolated follicles and maintains primordial follicle quiescence. Bovine ovaries were used here as a monovulatory model of folliculogenesis to examine the effects of primordial follicle activation and growth under different physical conditions. We found that there were no differences in activation, growth or survival when primordial follicles were cultured in isolation or in situ (remaining in the tissue) under two significantly differently rigid alginate gels. To determine if the extra rigid environment did not affect activation in isolated follicles due to an immediate activation event, we used 5-ethynyl-2'-deoxyuridine (EdU) to track follicle activation during the isolation process. We identified EdU incorporation in granulosa cells after primordial follicles were isolated from the surrounding extracellular matrix (ECM). These findings support that isolation of primordial follicles from the ECM is an activating event and that the differentially rigid environments assessed here had no effect on follicle growth. Further work is needed to suppress activation in primordial follicles to maintain the ovarian reserve and extend the life of an ovarian tissue transplant.