Sperm maturation and conservation in felids
Sammanfattning: Many of the world's wild feline species are threatened by extinction. Gene banks are created with the aim of preserving their genetic materials. In case of unexpected death of the animals, epididymal sperm preservation can be used to avoid loss of genetic material. However, one requirement for the genetic preservation of endangered species is to preserve as much genetic material as possible. Therefore, the overall aim of this thesis is to investigate the possibility of preserving not only spermatozoa from cauda region, which is the usual site, but also from other regions of the epididymis. If these spermatozoa could be used in assisted reproductive technology such as in vitro fertilization in the future, the number of the spermatozoa that could be preserved from one individual will be increased. The ability of feline spermatozoa from caput, corpus and cauda regions of epididymis to undergo capacitation and acrosome reaction, which are required before spermatozoa are able to fertilize oocytes, were investigated. We found that epididymal spermatozoa from all regions are able to undergo capacitation and acrosome reaction in vitro. However, the majority of the spermatozoa from corpus and cauda are more mature than the caput spermatozoa. Therefore spermatozoa from corpus and cauda regions were cryopreserved. After thawing, spermatozoa from corpus and cauda epididymal regions showed a similar survival rate and the cryopreservation process did not affect the DNA stability of these spermatozoa. Three different techniques, sperm chromatin structure assay, acridine orange staining technique and sperm chromatin dispersion, were compared and DNA stability of spermatozoa from the corpus and cauda epididymis after freezing-thawing was evaluated. All these techniques can be used to evaluate DNA fragmentation of feline epididymal spermatozoa but give different DNA fragmentation index values. Frozen-thawed feline epididymal spermatozoa from both the corpus and cauda were able to fertilize homologous oocytes in vitro and the embryos could develop to blastocyst stage. In conclusion, this thesis reveals that feline epididymal spermatozoa from the corpus region have a similar capability as spermatozoa from the cauda in many respects. Preservation of spermatozoa from corpus together with cauda can increase the number of spermatozoa that we can preserve from one individual by approximately 40% and spermatozoa from corpus are therefore useful for assisted reproductive technologies in the future.
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