Low levels of apoptotic-like changes in fresh and cryopreserved feline spermatozoa collected from the urethra and epididymis

Cushioned and high-speed centrifugation improve sperm recovery rate but affect the quality of fresh and cryopreserved feline spermatozoa

The development of endoscopic transcervical catheterization (ETC) in the queen increases the interest in handling fresh and cryopreserved feline semen. The ETC requires a small volume of the insemination dose with a high concentration, not easily reached with the actual frozen technique in this species. Centrifugation is widely used to concentrate spermatozoa for several purposes, but this process is detrimental to spermatozoa. This study verified the effects of conventional and cushioned centrifugation on fresh and cryopreserved feline spermatozoa. To this, semen was collected from 20 toms, grouped in seven pools and diluted. After dilution, the pools were divided into two aliquots, the first used for centrifugation on fresh semen, and the second, after freezing, on cryopreserved semen. Centrifugation regimens were: conventional at 500×g, conventional at 1000×g, and cushioned (iodixanol) at 1000×g. The sperm recovery rate was calculated for the three centrifugation regimens, and sperm kinematics, membrane and acrosome integrity, and plasma membrane stability on viable spermatozoa were assessed as endpoints. The data reported in this study showed that the centrifugation at 500×g resulted in negligible effects on both fresh and cryopreserved spermatozoa, but the lower recovery rate (62.4 ± 3.1 % and 60.2 ± 1.6 %, respectively) underlines the loss of a large proportion of spermatozoa, unfavourable in a species with small total sperm ejaculated. On the other hand, the centrifugation at 1000×g improved the recovery rate (86.9 ± 4.3 % and 89.8 ± 2.4 % in fresh and cryopreserved samples, respectively), but was more deleterious for feline spermatozoa, especially in cryopreserved samples (i.e. total motility of 40.7 ± 5.4 % compared with 57.2 ± 9.8 % in cryopreserved uncentrifuged samples, P < 0.05), resulting in artificial insemination doses of lower quality. The recovery rate in cushioned centrifugation appeared less efficient, likely due to the small volume of feline samples, which makes difficult the separation of sperm pellet and cushioned fluid. Interestingly, in cryopreserved samples centrifuged at 1000×g the number of viable spermatozoa with membrane destabilization (31.3 ± 3.2 %) was greater than uncentrifuged (4.1 ± 0.7 %, P < 0.05) and those centrifuged at 500×g (9.8 ± 1.3 %, P < 0.05), suggesting modifications induced by the cryopreservation amplifies centrifugation sublethal damage on feline spermatozoa. Cushioned centrifugation on cryopreserved samples showed kinematics similar to uncentrifuged samples, but higher viable spermatozoa with membrane destabilization (37.4 ± 3.4 % vs 4.1 ± 0.7 %; P < 0.05). In felines, g-force is crucial for sperm recovery rate during centrifugation, with better results at 1000×g; on the other hand, greater g-forces could have a significant impact on the quality of feline insemination dose, especially in cryopreserved samples.

Postmortem Collection of Gametes for the Conservation of Endangered Mammals: A Review of the Current State-of-the-Art

The collection of gametes from recently deceased domestic and wildlife mammals has been well documented in the literature. Through the utilization of gametes recovered postmortem, scientists have successfully produced embryos in 10 different wildlife species, while in 2 of those, offspring have also been born. Thus, the collection of gametes from recently deceased animals represents a valuable opportunity to increase genetic resource banks, obviating the requirement for invasive procedures. Despite the development of several protocols for gamete collection, the refinement of these techniques and the establishment of species-specific protocols are still required, taking into account both the limitations and the opportunities. In the case of wildlife, the optimization of such protocols is impeded by the scarcity of available animals, many of which have a high genetic value that must be protected rather than utilized for research purposes. Therefore, optimizing protocols for wildlife species by using domestic species as a model is crucial. In this review, we focused on the current advancements in the collection, preservation, and utilization of gametes, postmortem, in selected species belonging to Equidae, Bovidae, and Felidae, both domestic and wildlife.

Desiccated cat spermatozoa retain DNA integrity and developmental potential after prolonged storage and shipping at non-cryogenic temperatures

PURPOSE

To evaluate the DNA integrity and developmental potential of microwave-dehydrated cat spermatozoa after storage at - 20 °C for different time periods and/or overnight shipping on dry ice.

METHODS

Epididymal spermatozoa from domestic cats were microwave-dehydrated on coverslips after trehalose exposure. Dried samples were either assessed immediately, stored for various duration at - 20 °C, or shipped internationally on dry ice before continued storage. Dry-stored spermatozoa were rehydrated before assessing DNA integrity (TUNEL assays) or developmental potential (injection into in vitro matured oocytes followed by in vitro embryo culture for up to 7 days).

RESULTS

Percentages of dried-rehydrated spermatozoa with intact DNA was not significantly affected (P > 0.05) by desiccation and short-term storage (range, 78.9 to 80.0%) but decreased (P < 0.05) with storage over 5 months (range, 71.0 to 75.2%) compared to fresh controls (92.6 ± 2.2%). After oocyte injection with fresh or dried-rehydrated spermatozoa (regardless of storage time), percentages of activation, pronuclear formation, and embryo development were similar (P > 0.05). Importantly, spermatozoa shipped internationally also retained the ability to support embryo development up to the morula stage.

CONCLUSION

Results demonstrated the possibility to sustain DNA integrity and developmental potential of spermatozoa by dry-preservation, even after long-term storage and long-distance shipment at non-cryogenic temperatures. While further studies are warranted, present results demonstrate that dry preservation can be a reliable approach for simple and cost-effective sperm biobanking or shipment.

Quality of domestic cat semen collected by urethral catheterization after the use of different alpha 2-adrenergic agonists

OBJECTIVES

We compared the effects of two alpha (α)₂-adrenergic agonists on semen traits.

METHODS

In this study, 13 adult domestic cats were divided into two experimental groups, according to the chemical ejaculation protocol used: the first group received medetomidine hydrochloride (100 µg/kg) and ketamine (5000 µg/kg); the second group received dexmedetomidine hydrochloride (25 µg/kg) and ketamine (5000 µg/kg), both by the intramuscular route.

RESULTS

The animals responded positively (P >0.05) to chemical collection. Seminal parameters evaluated included volume, sperm vigor, total motility, progressive motility, sperm concentration, and the structural and functional integrity of the plasma membrane; sperm morphology values did not differ between groups (P >0.05).

CONCLUSIONS AND RELEVANCE

The results indicated that dexmedetomidine is a more viable and economical alternative to medetomidine in domestic cats submitted to semen collection by urethral catheterization. Semen collection by urethral catheterization after using α₂-adrenergic agonists is a recently developed technique in feline species that is considered to be quick and highly applicable to assisted reproduction programs in felids.

Influence of the type of semen and morphology of individual sperm cells on the results of ICSI in domestic cats

The aim of this study was to analyze the influence of the type of spermatozoa and of different sperm abnormalities on fertilization and embryo development after ICSI in cats. In Exp I, ICSI was performed using urethral or epididymal spermatozoa collected from 7 tomcats. In Exp. II, epididymal spermatozoa from 16 cats were used for ICSI and an epididymal spermatozoon exhibiting no abnormalities or one with an abnormality was microinjected into an oocyte. Exp. I was performed in 14 replicates and Exp. II was performed in 20 replicates. In both experiments the number of cleaved oocytes, the number of embryos at the morula stage and the number of embryos at the blastocyst stage were evaluated at 24 h, and at 6 and 7 days after ICSI, respectively, and compared between experimental groups. No statistically significant differences (P > 0.05) were observed, either for Exp. I or for Exp. II. The average cleavage rate was 60.2%, morula rate 62.3% and blastocyst rate 19.2% in Exp. I and 51.6%, 66.8% and 25.8% in Exp. II, respectively. The study confirmed that both urethral and epididymal spermatozoa can be used for in vitro fertilization in cats and proved the usefulness of the ICSI method in the case of teratozoospermic males. The study showed that even in severe cases, when almost no normal spermatozoa can be found in the semen, it is possible to obtain embryos using abnormal sperm cells with the same chance of success as for normal spermatozoa.

Evaluation of sperm head dimensions and chromatin integrity of epididymal sperm from domestic cats using the toluidine blue technique

When using assisted reproductive technologies, there is seldom an evaluation of DNA integrity during sperm analysis, which is an important variable for proper embryo development. The toluidine blue staining technique allows the simultaneous evaluation of sperm chromatin and sperm head dimensions. The objectives of this study were to evaluate the applicability of the toluidine blue staining method for analyzing DNA abnormalities in epididymal sperm (from the caput, corpus, and cauda) of cats and to investigate the correlations among DNA condensation, morphology, and sperm head dimensions. The DNA alteration indexes were obtained using the toluidine blue and acridine orange techniques, and comparisons of these indexes indicated there was a 65.4% (r = 0.654; P < 0.001) correlation. The sperm from the cauda had greater chromatin stability (97.9%) than the sperm from the epididymal head (92.1%; P = 0.0023). There, however, was no difference in chromatin stability between sperm obtained from the corpus and cauda regions, indicating that these sperm were already mature. The sperm head dimension was correlated with chromatin decondensation, and the sperm head size decreased as the sperm were transported through the three epididymal regions (P < 0.0001). In addition, the percentage of sperm that were deficient in chromatin condensation decreased as the sperm were transported through the epididymal caput, corpus and cauda (26.4, 15.7, and 3.4%, respectively; P < 0.0001). Thus, the sperm head size predicts the quality of chromatin condensation in sperm cells.