Influence of different warming temperatures on the vitrified testicular fragments from pre-pubertal cat

Evaluation of Different Cryoprotectant Combinations in Testicular Vitrification in Dogs

Testicular vitrification requires the use of high concentrations of cryoprotectants, which can cause damage to samples due to their toxicity. The combination of these substances comes up as a way to mitigate this problem. Thus, the aim of this study was to evaluate three cryoprotectant combinations in the testicular vitrification of dogs. Ten testicular pairs from adult dogs were used, from which 12 fragments of each pair were obtained, distributed among the fresh control group (CTR) and the experimental groups according to the cryoprotectant combinations tested: dimethyl sulfoxide (DMSO)/ethylene glycol (EG), DMSO/glycerol (GLY), and EG/GLY. The fragments were vitrified using the solid surface vitrification method (SSV), at a final concentration of 5.6 mol/L of the combined cryoprotectants. Subsequently, they were warmed up and processed for histomorphological morphometric evaluations and determination of mitochondrial activity with Rhodamine 123. Considering the morphological evaluation, the DMSO/EG group showed results similar to CTR, with good scores for nuclear integrity and cell organisation in the seminiferous tubules (p > 0.05). In contrast, the EG/GLY group presented greater nuclear condensation. It was difficult to visualise and distinguish between spermatogonia and Sertoli cells (p < 0.05). The DMSO/GLY group also showed distinct levels between spermatogonia and Sertoli cells, as well as nuclear condensation, which statistically differed from CTR (p < 0.05). Also, it was observed a random distribution of the remaining cells in the seminiferous tubules of the EG/GLY and DMSO/GLY groups. The three tested groups showed basement membrane retraction and a reduction of approximately 11.6% in the average diameter of the seminiferous tubules (p < 0.05). Vitrification did not influence the mitochondrial activity of the samples, regardless of the combination of cryoprotectants used (p > 0.05). It was concluded that the DMSO/EG combination best contributed to the maintenance of the testicular histomorphological structure of dogs after vitrification.

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.

Influence of Three Combinations of Cryoprotectants and Two Warming Temperatures on Cellular Morphology, Morphometry and Mitochondrial Activity of Vitrified Canine Testicles

High concentrations of cryoprotectants required for testicular vitrification result in a toxic environment for cells. To mitigate this issue, a suitable alternative is to combine cryoprotectants. The temperature for warming a vitrified sample is also important to assure cell viability. Thus, the aim of this work was to evaluate how combining cryoprotectants (ethylene glycol-EG, glycerol-GLY, and dimethyl sulfoxide-DMSO) in pairs and using two warming temperatures (37°C and 50°C) influence cellular morphology, tubular morphometry, and mitochondrial activity after testicular vitrification of dogs. Testicular fragments from ten adult dogs were distributed among the fresh control group (CTR) and the experimental groups according to the combination of cryoprotectants and temperatures (EG/GLY37, EG/GLY50, DMSO/GLY37, DMSO/GLY50, DMSO/EG37 and DMSO/EG50). The fragments were vitrified in a final concentration of 5.6 mol/L (2.8 mol/L of each of the cryoprotectants combined two by two) and subsequently warmed up to 37°C/30 s or 50°C/5 s. Following this, they were processed for histomorphological, morphometric, and mitochondrial activity evaluations with Rhodamine 123. In the morphometric evaluation, all vitrified groups showed a significant reduction in tubular diameter (p < 0.05). All experimental groups showed greater basement membrane separation when related to the CTR (p < 0.05). DMSO/EG37 showed the greatest basement membrane separation when compared to all other groups (p < 0.05). Regarding membrane retraction, all vitrified groups, regardless of the warming temperature, had greater retraction when related to CTR (p < 0.05), except DMSO/GLY50, which did not differ from any group (p > 0.05). Regarding the distinction between spermatogonia and Sertoli cells, no groups warmed up to 50°C differed from the control, except DMSO/GLY37. For nuclear visualisation, none of the vitrified groups differed from the CTR (p > 0.05), except DMSO/GLY37 (p < 0.05), which showed better nuclear visualisation. For the nuclear condensation parameter, there were no significant differences among the groups (p > 0.05). Mitochondrial activity was reduced in all vitrified samples, regardless of the combination of cryoprotectants and warming temperature (p > 0.05). It was concluded that the association of DMSO/GLY50 presented better preservation of morphological aspects.

Effect of Different Vitrification Techniques on Viability and Apoptotic Index of Domestic Cat Testicular Tissue Cells

Vitrification is essential for successful tissue cryopreservation and biobanking in wild cats. This study aimed to compare different methods of vitrification (Ovarian Tissue Cryosystem-OTC, Straws-STW, and Solid Surface vitrification-SSV) for testicular fragment vitrification in tom cats. Testicular fragments were recovered from five adult tom cats and subjected to equilibrium vitrification using different cryovials and methods under the same conditions of vitrification solutions and cryoprotectants. The efficiencies of the methods were evaluated using histological analysis of spermatogonia and Sertoli cell nuclei, seminiferous tubular basement membrane detachment, and the gonadal epithelium shrinkage score scale. Cell viability was assessed using Hoechst PI and Terminal deoxynucleotidyl transferase nick end labeling (TUNEL) assay. The results showed that OTC is an effective vitrification method for maintaining the distinction between spermatogonia and Sertoli cells. OTC was similar to the control for basal membrane detachment parameters (p = 0.05). Epithelial shrinkage was low in the SSV group, which showed the highest percentage of viable cells among the vitrified groups (p = 0.0023). The OTC and SSV vitrification methods were statistically similar in terms of the percentage of TUNEL-positive cells (p = 0.05). Therefore, OTC and SSV provide favorable conditions for maintaining viable cat testicular tissue cells after vitrification.

Canine and Feline Testicular Preservation

Simple Summary

Testicular cryopreservation enables the maintenance of reproductive potential, the creation of germplasm banks and the transport of genetic material between different regions. This biotechnology represents the only possibility of preserving the fertility of prepubertal animals that have already died or that need to undergo gonadotoxic treatments. Despite advances in the use of cryopreserved testicular fragments, protocols that can be used in the clinical routine of dogs and cats have not yet been established. Due to the great importance of the topic, the objective of this review is to provide an overview of the subject, approaching the main works on testicular cryopreservation in dogs and cats.

Abstract

The increased interest in breeding dogs and cats and their use as models for other canids and felids demand research to improve reproductive techniques. Among them, testicular cryopreservation stands out. Testicular cryopreservation enables the maintenance of reproductive capacity and allows the establishment of germplasm banks for several species of commercial value or at risk of extinction. Furthermore, it enables the transport of genetic material among different regions. It is noteworthy that this biotechnology represents the only possibility of preserving the fertility of prepubertal animals that have died, so it has great importance in the propagation of the genetic material of animals. The spermatogonia present in the testes can be cultivated in vitro and the sperm obtained can be used in artificial reproduction programs. Although advances have been achieved with the use of testicular fragments to obtain viable and functional germ cells, the establishment of protocols that can be used in clinical routine have not been concluded yet. The testicular cryopreservation process can be carried out through techniques such as slow freezing, fast freezing and vitrification. However, the protocols used for the canine and feline species are still in the experimental phase. Given the importance of the topic, the aim of this review is to draw a profile of the subject approaching the main works on testicular cryopreservation in dogs and cats.