Comparison of cryosurvival and spermatogenesis efficiency of cryopreserved neonatal mouse testicular tissue between three vitrification protocols and controlled-rate freezing

A comparative analysis of vitrification and two slow freezing methods for gonocyte-containing neonatal calf testicular tissue and subsequent in vitro culture

The cryopreservation of neonatal testicular tissue containing gonocytes is crucial for preserving genetic diversity, advancing research, and developing reproductive technologies. In this study, we investigated three cryopreservation techniques, slow freezing (in which the rate of freezing was controlled or uncontrolled) and vitrification, using neonatal bovine testicular tissues containing gonocytes, followed by in vitro culture to evaluate cell functionality. Vitrification resulted in a significantly lower proportion (19.15 ± 1.82%) of seminiferous tubules with > 70% attachment to the basement membrane in comparison to both the controlled slow freezing group (47.89 ± 10.98%) and the uncontrolled slow freezing group (39.05 ± 4.15%) (P < 0.05). No significant differences were observed in the proportion of seminiferous tubules containing PGP9.5-positive germ cells when compared between the three methods. Comparable densities of germ cells per unit area were observed in the controlled/uncontrolled slow freezing groups and the vitrification group (7.89 ± 1.83, 7.75 ± 1.75, and 7.92 ± 1.23/104 µm2, respectively). In addition, the proportions of Sertoli cells (vimentin-positive) and proliferating cells (Ki67-positive) were similar across the three cryopreservation methods. There were no significant differences in cell membrane integrity and the expression of selected genes when compared between the three cryopreservation groups. Compared to fresh tissue, the uncontrolled slow freezing groups exhibited significantly higher levels of apoptosis (P < 0.05); there was no significant change in the controlled slow freezing and vitrification group. Notably, all in vitro cultures of testicular cells, from both fresh and freeze/thawed tissues, displayed the formation of germ cell colonies. Our data demonstrate that vitrification effectively preserves neonatal bovine testicular tissues containing gonocytes, safeguarding cell membrane integrity, promoting proliferation, and protecting against apoptosis. Collectively, these findings propose vitrification as a promising alternative cryopreservation method for immature testicular tissue (ITT) in clinical applications.

Recent Progress of Induced Spermatogenesis In Vitro

Sperm, a crucial gamete for reproduction in sexual reproduction, is generated through the proliferation, differentiation, and morphological transformations of spermatogonial stem cells within the specialized microenvironment of the testes. Replicating this environment artificially presents challenges. However, interdisciplinary advancements in physics, materials science, and cell engineering have facilitated the utilization of innovative materials, technologies, and structures for inducing in vitro sperm production. This article offers a comprehensive overview of research progress on inducing in vitro sperm production by categorizing techniques into two major systems based on matrix-based and non-matrix-based approaches, respectively. Detailed discussions are provided for both types of technology systems through comparisons of their similarities and differences, as well as research advancements. The aim is to provide researchers in this field with a comprehensive panoramic view while presenting our own perspectives and prospects.

Cryopreservation and Culture of Testicular Tissues: An Essential Tool for Biodiversity Preservation

Systematic cryo-banking of reproductive tissues could enhance reproductive management and ensure sustainability of rare mammalian genotypes. Testicular tissues contain a vast number of germ cells, including at early stages (spermatogonia and spermatocytes), that can potentially develop into viable spermatozoa after grafting or culture in vitro, and the resulting sperm cells then can be used for assisted reproductive techniques. The objective of this review was to describe current advances, limitations, and perspectives related to the use of testicular tissue preservation as a strategy for the conservation of male fertility. Testes can be obtained from mature or prepubertal individuals, immediately postmortem or by orchiectomy, but testicular biopsies could also be an alternative to collect samples from living individuals. Testicular fragments can be then cryopreserved by using slow or ultra-rapid freezing, or even vitrification methods. The composition of cryopreservation media can vary according to species-specific characteristics, especially regarding the cryoprotectant type and concentration. Finally, spermatozoa have been usually obtained after xenografting of testicular fragments into severely immunodeficient mice, while this method still has to be optimized after in vitro culture conditions.