A comparison between a new vitrification protocol and the slow freezing method in the cryopreservation of prepubertal testicular tissue

OBJECTIVE: This study aimed to compare a new vitrification protocol with reduced cryoprotectant exposure to the slow freezing method in the cryopreservation of prepubertal rat testicular tissue. METHODS: Five sexually immature male Wistar rats were submitted to bilateral orchiectomy. Tissue samples from each testicle were fragmented into small pieces and randomly assigned to three groups: Group A, fresh tissue (control); Group B, slow programmable freezing (SPF); and Group C (vitrification). Frozen/thawed, vitrified/warmed, and fresh testicular tissue were histologically compared. A pathologist blinded to the procedures assessed the morphology (cell differentiation, nuclei, and epithelium) of 10 seminiferous tubules from each testicle (100 tubules per Group). RESULTS: Sertoli and spermatogonial stem cells were easily differentiated, and the nucleoli were easily viewed in the tubules assessed in all three groups. Small alterations in tissue architecture were observed in the control group as a result of tissue handling. Moderate alterations of the epithelium with the formation of small gaps and cell detachment from the basement membrane were observed in 28% of the frozen and 9% of the vitrified tubules. Condensed nuclei involving a small proportion of cells were observed in six and three tubules of the frozen and vitrified group, respectively. Despite the alterations, 97% of the frozen and 99% of the vitrified tubules were considered well preserved. CONCLUSIONS: The findings indicate that the vitrification protocol tested in this study adequately preserved the morphological integrity of prepubertal testicular tissue in a rat model. Further studies are required to confirm testicular tissue function after grafting.