Expression of CD13 and CD26 on extracellular vesicles in canine seminal plasma: preliminary results

Canine seminal plasma is a complex fluid containing proteins, peptides, enzymes, hormones as well as extracellular vesicles that are involved in many physiological and pathological processes including reproduction. We examined the expression of the extracellular vesicles surface antigens Aminopeptidase-N (CD13) and Dipeptidyl peptidase IV (CD26) by flow cytometry. For this study, third fraction of the ejaculate, from fertile adult male German Shepherd dogs, was manually collected twice, two days apart. FACS analyses revealed that CD13 and CD26 are co-expressed on the 69.3 ± 3.7% of extracellular vesicles and only a 2.0 ± 0.5% of extracellular vesicles express CD26 alone. On the other hand, 28.6 ± 3.6% of seminal EVs express CD13 alone. Our results agree with the hypothesis that CD26 needs to be co-expressed with other signal-transducing molecules, while CD13, can perform functions independently of the presence or co-expression of CD26. The results obtained in normal fertile dogs could represent physiological expression of these enzymes. Therefore, it would be interesting to carry out further studies to evaluate the expression of CD13 and CD26 on extracellular vesicles as biomarker for prostate pathological condition in dogs.

Assisted reproduction for felid species conservation-Sperm competences at risk

Cryobanking of gametes in combination with artificial insemination is an essential option to support conservation programmes for endangered and threatened species. About two-thirds of the felid species are classified as 'near threatened', 'vulnerable' or 'endangered' (www.cites.org), and mostly, epididymal sperm are collected from euthanized or castrated male felids and cryopreserved. However, epididymal compared with ejaculated and cryopreserved compared with fresh sperm have a limited potential to fertilize if vaginal non-surgical insemination is applied in feline species. Missing or highly diluted seminal fluid in epididymal and cryopreserved sperm, as well as a potential interference of extender ingredients with the natural interactive properties of sperm in the female genital tract is discussed as potential drawback which hampers a proper sperm transit and fertilization besides the limited longevity of cryopreserved feline sperm. Individual components in seminal fluid as well as cryoextenders may adversely alter sperm properties and have a different impact on fertility and preservation success. The identification and investigation of beneficial as well as detrimental components is a precondition to deduce options for improving the process of cryopreservation in felids, particularly, if only epididymal sperm are available.

Addition of different concentrations of prostasome-like vesicles at neutral or slightly alkaline pH decreases canine sperm motility

Prostasome-like vesicles (PV) are components of the canine prostatic fluid during ejaculation and despite some enzymatic activities have been identified recently, their functions in the reproductive events in this species are still poorly understood. In this study, we evaluated at neutral or slightly alkaline pH, the effects of different concentrations of purified PV on sperm cell motility characteristics and the impact on the short- and long-term preservation of preserved semen maintained at room temperature. Two different experiments were performed. In the first experiment, purified PV were added at increasing concentration (1.25, 2.5, 5, 10, and 20 μL equivalent to 1, 2, 4, 8, and 16 μg of protein, respectively) to aliquots of 100 μL of preserved semen maintained at 22 °C at the following time points: 0, 30, 60, 120, 240, and 480 min. Computer-assisted sperm motility characteristics and pH were assessed three times at each time points, for each sample and for every concentrations. In the second experiment, the purified PV were added with the same methods as described above but only at time 0. Sperm motility characteristics and pH were assessed over the time. This study showed how the addition of purified PV to preserved semen affects negatively (p < 0.05) at neutral and alkaline pH, both total and progressive motility in a concentration depending manner. Furthermore, prostasome addition was demonstrated to change the quality of sperm movement which may represent a mechanism facilitating sperm cells attachment to the uterine epithelium and facilitating energy preservation before fertilization.