Ovarian tissue cryopreservation is gaining importance as a successful method to restore fertility to girls and young women at high risk of sterility. However, there are concerns regarding the safety of transplantation after ovarian tissue cryopreservation due to the high risk of reintroducing cancer cells and causing disease recurrence. In these cases, the development of culture systems that support oocyte development from the primordial follicle stage is required. Notable achievements have been reached in human follicle in vitro growth in the past decade. Currently, systems for the in vitro culture of ovarian tissue are based on two-dimensional substrates that do not support the survival of follicles or recapitulate the mechanical heterogenicity in the mammalian ovary. Recognition of the importance of special arrangements between cells has spurred research in three-dimensional culture systems, and the provision of a precise culture system that maximizes the diffusion of nutrients and gases through the follicles has raised interest in advanced biomimetic models. The current review critically examines various culture systems employed for the in vitro development of follicles, with a particular focus on solutions utilizing Organ-on-a-Chip (OOC) technology. The emphasis on OOC technology underscores its role as a promising avenue in ensuring the successful cultivation and maintenance of follicular structures during the culture period.

Childhood cancer incidence, especially in high-income countries, has led to a focus on preserving fertility in this vulnerable population. The common treatments, such as radiation and certain chemotherapeutic agents, though effective, pose a risk to fertility. For adult women, established techniques like embryo and egg freezing are standard, requiring ovarian stimulation. However, for prepubescent girls, ovarian tissue freezing has become the primary option, eliminating the need for hormonal preparation. This review describes the beginning, evolution, and current situation of the fertility preservation options for this young population. A total of 75 studies were included, covering the steps in the current fertility preservation protocols: (i) ovarian tissue extraction, (ii) the freezing method, and (iii) thawing and transplantation. Cryopreservation and the subsequent transplantation of ovarian tissue have resulted in successful fertility restoration, with over 200 recorded live births, including cases involving ovarian tissue cryopreserved from prepubescent girls. Despite promising results, challenges persist, such as follicular loss during transplantation, which is attributed to ischemic and oxidative damage. Optimizing ovarian tissue-freezing processes and exploring alternatives to transplantation, like in vitro systems for follicles to establish maturation, are essential to mitigating associated risks. Further research is required in fertility preservation techniques to enhance clinical outcomes in the future. Ovarian tissue cryopreservation appears to be a method with specific benefits, indications, and risks, which can be an important tool in terms of preserving fertility in younger women.

The in vitro maturation (IVM) of human oocytes represents a valuable assisted reproductive technology that bypasses the need for full ovarian stimulation, offering safer alternatives for patients with polycystic ovary syndrome (PCOS), resistant ovary syndrome, or those requiring fertility preservation before oncological treatment. Despite its potential, IVM efficiency remains lower than that of conventional in vitro fertilization (IVF) due to incomplete understanding of the molecular and metabolic mechanisms underpinning oocyte maturation. This review summarizes recent advances in IVM, including biphasic or simulated physiological oocyte maturation (SPOM) systems, optimization of culture media through hormones, growth factors, and antioxidants, and the influence of cumulus–oocyte communication on developmental competence. We also discuss the biochemical regulation of meiosis, metabolic interactions, and gene expression patterns associated with oocyte quality. Furthermore, we examine the translational and clinical applications of IVM in human fertility treatment, highlighting its efficacy in PCOS and oncofertility cases, and the limitations that persist in replicating in vivo conditions. Emerging technologies such as microfluidic and three-dimensional culture systems show promise in enhancing oocyte competence and embryo yield. Continued research into the molecular mechanisms governing oocyte maturation will be key to improving IVM outcomes and integrating this approach as a mainstream option in reproductive medicine.

To study innovative approaches to ovarian tissue cryopreservation, a critical issue for fertility preservation in pediatric cancer patients. Despite historical attempts, recent advances in cancer treatment have underscored the urgent need for more effective and reliable ovarian tissue cryopreservation methods. Our research aims to evaluate if decreasing the rigidity of stroma before cryopreservation by investigating pre-treatments with enzymes can enhance the quality of ovarian tissue post-thawing. Our research evaluated the use of five commonly used enzymes to disaggregate tissue (trypLE, collagenase, dispase, accutase and hyaluronidase) before freezing ovarian tissue to decrease rigidity and facilitate cryopreservation. Sheep ovaries, with high similarity to human ovaries, were used as an animal model. Tissue structure, cell proliferation, apoptosis and viability were assessed before and after thawing. Our findings showed that enzymatic treatment with trypLE before freezing offered immediate benefits post-thawing with the highest viability values and percentage of intact follicles. A decrease in viability was observed after thawing and culturing the samples. The pretreatment with accutase damaged the tissue severely with also the lowest viability values. Ki67-positive follicles and stromal cells were observed in fresh samples, but only trypLE and hyaluronidase maintained Ki67-positive antral follicles after 2 days culture. Besides, only trypLE maintained all follicles negative to caspase-3 after thawing, and 7 days after culture primordial follicles were apoptotic in all treatments apart from trypLE. our findings suggest that trypLE pretreatment could provide a beneficial approach for maintaining the functions and viability of cryopreserved ovaries after thawing. Further research is needed to fully understand their impact and optimize cryopreservation protocols in this important clinical context.