Testicular Tissue Vitrification: a Promising Strategy for Male Fertility Preservation

Solid Surface Vitrification Is Better than Slow Freezing for the Long-Term Preservation of Testicular Fragments from Prepubertal Collared Peccaries (Pecari tajacu Linnaeus, 1758)

The cryopreservation of male gonadal tissue is critical to conserve genetic material and use it later via assisted reproduction. This study aimed to evaluate cryopreservation methods (slow freezing, SF; solid surface vitrification, SSV) as well as the optimal concentrations of intracellular cryoprotectants during the SSV of testicular tissue from prepubertal collared peccaries. Five pairs of testes were dissected on different days into small fragments (3 mm3) and allocated to a non-cryopreserved, a control group or one of three treatment groups: SF; SSV 3 M (1.5 M dimethyl sulfoxide [DMSO] plus 1.5 M ethylene glycol [EG]); or SSV 6 M (3 M DMSO plus 3 M EG). After one week of storage in liquid nitrogen, tissue samples were warmed and evaluated in terms of histology, viability, proliferative capacity potential, and DNA integrity. The scores for histological integrity and cellular damage for SF (2.08 ± 0.05 and 2.33 ± 0.07, respectively) were similar to the results found in SSV 6 M (1.93 ± 0.04 and 2.30 ± 0.07; p > 0.05). However, these scores were better when compared to SSV 3 M (1.87 ± 0.05 and 2.08 ± 0.06; p < 0.05). The percentage of cellular viability was around 57% after all preservation treatments (p > 0.05), which was lower than in the control group (88.8 ± 1.9%; p < 0.05). The SSV 6 M treatment was better than the other treatments regarding the proliferative capacity potential of spermatogonia cells (3.52 ± 0.03) (p < 0.05), although it was lower than in the control group (4.00 ± 0.12) (p < 0.05). Additionally, SSV 6 M led to the same DNA integrity (97.0 ± 0.7%) as in the control group (99.4 ± 0.3%). These collective findings suggest that the combination of SSV with 6 M cryoprotectants is the most efficient for the cryopreservation of testes from prepubertal collared peccaries.

Testicular tissue cryopreservation and transplantation as a strategy for feline conservation: a review of research advances

As we humans continue our detrimental activities on the planet, the biodiversity loss is now seen as a big threat to entire ecosystem in which we all live. This issue becomes even more critical as we see a rapid increase in the number of animal species being listed as endangered, and a far greater rate of species extinction. We all know that felines play a crucial part in our ecosystems, it is therefore safe to argue that their conservation could play an important role in minimizing the biodiversity loss. Advanced reproductive biotechnologies including testicular tissue cryopreservation and transplantation are considered as effective tools for the conservation of animal species. As we have seen with the Giant Panda, these biotechnologies could offer new possibilities for the conservation of other endangered species including felines. Although previously a few wild feline spp. were conserved by this method, little is known about the factors influencing the efficiency of these methods. Therefore, if we are to maximize the conservation efforts, further optimization of these biotechnologies is required to achieve better conservation results. In this article, we present an overview of testicular tissue of felines and the factors influencing testicular tissue cryopreservation and testicular graft recovery in felines.

Xenotransplantation of Cryopreserved Calf Testicular Tissues

The cryopreservation of testicular tissues meets the demands for the germplasm preservation of humans and animals. Previously, we reported on the cryopreservation of bovine testicular tissues. To further evaluate the viability of these tissues, subcutaneous xenotransplantation of the frozen-thawed calf testicular tissues was performed with castrated nude mice as the recipients. After 28 days (D28), the survival and development of the grafts were examined. The grafts from 1-day-old (D1) calf testes were recovered and angiogenesis around the grafts was observed. Histologically, the seminiferous cords in the grafts were well maintained and capillaries in the interstitium were observed. Quantitative real-time PCR (qRT-PCR) analysis showed that the grafts expressed germline genes Gfrα-1, C-kit, and Sycp3 and somatic genes Sox9, Acta2, and Star. The expressions of C-kit, Sox9, Acta2, and Star were higher in 28D grafts than those in 1D and 30-day-old (30D) calf testicular controls. Together, we initially demonstrate that cryopreserved calf testicular tissues retain their viability and developmental capacity after xenotransplantation.

Hydrogel encapsulation facilitates a low-concentration cryoprotectant for cryopreservation of mouse testicular tissue

Cryopreserved testicular tissue offers a promising method to restore fertility in male infertility patients. Current protocols rely on high concentrations of penetrating cryoprotectants (pCPAs), such as dimethyl sulfoxide (DMSO), which necessitating complex washing procedures and posing risks of toxicity. Hydrogel encapsulation presents a non-toxic alternative for cellular cryopreservation. This study investigates the effects of various types, concentrations, and thicknesses of hydrogel encapsulation on the cryopreservation of mouse testicular tissue. Testicular tissues loaded with varying concentrations of DMSO were encapsulated in alginate or gelatin-methacryloyl (GelMA) hydrogels. We evaluated hydrogels as potential CPAs to reduce pCPA concentrations and determine optimal combinations for cryopreservation. Post-cryopreservation, tissues were cultured using organ culture methods to assess spermatogenesis progression. Cryomicroscopy and differential scanning calorimetry (DSC) were used to examine ice crystal formation, melting enthalpy, and non-freezing water content in different hydrogels during cooling. Results indicate that 3 % alginate or 5 % GelMA hydrogel with thin encapsulation optimally preserves mouse testicular tissue. Using 20 % DMSO in 5 % GelMA thin encapsulation showed comparable apoptosis rates, improved morphology, higher mitochondrial activity, and enhanced antioxidant capacity compared to conventional 30 % DMSO without encapsulation. This suggests that hydrogel encapsulation reduces pCPA concentration by 10 %, thereby mitigating toxic damage. Hydrogel encapsulation can reduce basement membrane shrinkage of testicular tissue during cryopreservation. Moreover, frozen tissues remained viable with preserved germ cells after being cultured for one week on alginate methacryloyl (AlgMA) hydrogel using the gas-liquid interphase method. Cryomicroscopy and DSC studies confirmed the hydrogel's ability to inhibit ice crystal growth. In conclusion, this study introduces novel strategies for male fertility preservation and advances cryopreservation technology for clinical applications in assisted reproduction.

Global status of research on fertility preservation in male patients with cancer: A bibliometric and visual analysis

Background

Recently, male fertility preservation before cancer treatment has become more prevalent. The research in this field has progressed over time, with some studies having a major impact and providing guidance for further research. However, the trends and hotspots of research on fertility preservation in male cancer patients may have changed; exploring them is essential for relevant research progress.

Design

We extracted relevant studies from the Web of Science Core Collection database, capturing information on the countries of study, affiliations, authors, keywords, as well as co-citations of references and journals. To identify publication trends, research strengths, key subjects, prominent topics, and emerging areas, we conducted a bibliometric analysis using CiteSpace.

Results

We included 3201 articles on fertility preservation in male cancer patients published over January 1999 to December 2023 were included. Although the relevant research growth rate was slow initially, the number of publications increased annually. Of all study countries, the United States, Germany, and Japan reported the earliest studies; the United States published the highest number of relevant studies. The US institutions remained at the forefront for all 25 years, and the US researcher Ashok Agarwal published the most articles. Literature co-citation analyses indicated a transformation in the study participants; they comprised a younger demographic (i.e., a large number of adolescent male patients underwent fertility preservation); moreover, fertility preservation techniques evolved from sperm cryopreservation to testicular tissue cryopreservation. Research on reproductive outcomes of sperm cryopreservation was the recent hotspot in male fertility preservation research, and the impact of immunotherapy and checkpoint inhibitors on male fertility requires further research.

Conclusions

Male fertility preservation will be a major future research focus, with closer connections and collaborations between countries and organizations. Our results present the historical data on the development of research on male fertility preservation in cancer patients, providing relevant insights for future research and development in this study area.

Bridging the Gap: Animal Models in Next-Generation Reproductive Technologies for Male Fertility Preservation

This review aims to explore advanced reproductive technologies for male fertility preservation, underscoring the essential role that animal models have played in shaping these techniques through historical contexts and into modern applications. Rising infertility concerns have become more prevalent in human populations recently. The surge in male fertility issues has prompted advanced reproductive technologies, with animal models playing a pivotal role in their evolution. Historically, animal models have aided our understanding in the field, from early reproductive basic research to developing techniques like artificial insemination, multiple ovulation, and in vitro fertilization. The contemporary landscape of male fertility preservation encompasses techniques such as sperm cryopreservation, testicular sperm extraction, and intracytoplasmic sperm injection, among others. The relevance of animal models will undoubtedly bridge the gap between traditional methods and revolutionary next-generation reproductive techniques, fortifying our collective efforts in enhancing male fertility preservation strategies. While we possess extensive knowledge about spermatogenesis and its regulation, largely thanks to insights from animal models that paved the way for human infertility treatments, a pressing need remains to further understand specific infertility issues unique to humans. The primary aim of this review is to provide a comprehensive analysis of how animal models have influenced the development and refinement of advanced reproductive technologies for male fertility preservation, and to assess their future potential in bridging the gap between current practices and cutting-edge fertility techniques, particularly in addressing unique human male factor infertility.

The impact of busulfan on the testicular structure in prepubertal rats: A histological, ultrastructural and immunohistochemical study

Busulfan is a widely used cancer chemotherapeutic agent. Temporary or permanent sterility in male patients is one of the most common side effects of this drug. The present study was performed to evaluate the changes in the microscopic structure of the testes of prepubertal rats, as well as the changes in PCNA and caspase-3 immune expression, at different durations after busulfan administration. The rats were 5 weeks old and were divided into two main groups. Control group and busulfan treated group. Busulfan treated group received a single dose of busulfan (40 mg/kg), then animals were subdivided to three subgroups; IIa, IIb, IIc which were sacrificed after four, ten and twenty weeks, respectively, from the beginning of the experiment. Light and electron microscopic studies were done. Serum testosterone level and relative testes weight were assessed. Immunohistochemical staining for anti-proliferating cell nuclear antigen (PCNA) and anti-caspase-3 antigen was also done. Morphometric and statistical studies were carried out. Group II revealed histological and ultrastructural degenerative changes including congested blood vessels and degenerated spermatogenic epithelium, Sertoli cells, and Leydig cells. These changes were more evident after 10 weeks of busulfan administration and were accompanied by absence of mature sperms in the lumen of seminiferous tubules. These changes were associated with a significant reduction in relative testes weight, testosterone level, germinal epithelial height and seminiferous tubule diameter. Moreover, PCNA and caspase-3 immune expression was significantly altered in busulfan treated group. Mild improvement in testicular structure was observed 20 weeks after busulfan treatment.