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; <i>p</i> > 0.05). However, these scores were better when compared to SSV 3 M (1.87 ± 0.05 and 2.08 ± 0.06; <i>p</i> < 0.05). The percentage of cellular viability was around 57% after all preservation treatments (<i>p</i> > 0.05), which was lower than in the control group (88.8 ± 1.9%; <i>p</i> < 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) (<i>p</i> < 0.05), although it was lower than in the control group (4.00 ± 0.12) (<i>p</i> < 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.