Normozoospermic versus teratozoospermic domestic cats: differential testicular volume, sperm morphometry, and subpopulation structure during epididymal maturation

A New Approach of Sperm Motility Subpopulation Structure in Donkey and Horse

This study aimed to characterize the sperm kinematic values with high frames per second, to define the subpopulation structure of a horse and a donkey and compare them. A total of 57 fresh semen ejaculates (26 Spanish and 16 Arabian horse breeds and 10 donkeys) were collected and subsequently analyzed for kinematic parameters using the Computer-aided sperm motility analysis ISAS®v1.2 system and using a Spermtrack® 10-μm depth counting chamber. Sequences were recorded at 250 frames per second, and eight kinematic parameters were automatically evaluated. All kinematic parameters showed significant differences between a donkey and a horse and between horse breeds. All ejaculates evaluated showed excellent semen motility characteristics, with significantly higher values for all kinematic parameters for donkeys compared with horses except for beat-cross frequency. Donkey sperm was faster and linear than the horse. Regarding horse breeds differences, the Spanish horse had higher average path velocity, curvilinear velocity, and beat-cross frequency compared with the Arabian horse. Spanish horse sperm was rapid, but Arab horse was more linear. The principal component analysis showed three sperm subpopulations in the ejaculate of donkeys and horses with a significantly different motility characteristic between them. The dominant subpopulation for both donkey and horse was for rapid, straight, and linear with a high beat sperm (38.2 and 41.7%, respectively), whereas the lowest subpopulation was for the slowest and non-linear sperms. This, plus slight differences in the distribution of these subpopulations between Arabian and Spanish horses, were found. In conclusion, higher frames permitted to have a new interpretation of motile subpopulations with species and breed differences. More so, future works on donkey and horse breed spermatozoa should take into account differences between breeds that may interfere and alter the real analysis performed.

Spermatogenic Activity and Sperm Traits in Post-Pubertal and Adult Tomcats (Felis catus): Implication of Intra-Male Variation in Sperm Size

Tomcats are considered to be adults at 1 year of age, although many reach sexual maturity at an earlier age. Nevertheless, we still know little about whether the spermatogenic activity and sperm quality of mature under one-year-old tomcats differ from those of tomcats that are over one-year-old. This study aims to evaluate the spermatogenic activity, sperm traits, and their relationships in mature tomcats at two different ages. Sixteen tomcats showing complete spermatogenesis and spermatozoa in their epididymal caudae were used and classified according to their age as post-pubertal (<1 year old) or adult (˃1 year old). Our results show that adult cats have higher epididymal sperm concentration and lower coefficient of variation in sperm head width and ellipticity than post-pubertal cats. However, they do not differ in their testicular and epididymal mass, spermatogenesis, and sperm traits such as motility, mitochondrial activity, morphology, morphometry, as well as plasma membrane, acrosome, and DNA integrity. Reduced intra-male variation of sperm head ellipticity is associated with higher testis mass, epididymis mass, and sperm concentration. Interestingly, low intra-male variation in sperm head size is associated with increased Sertoli cell function and reduced post-meiotic germ cell loss. These findings increase our knowledge about feline reproductive physiology and provide new insights into the functional significance of low intra-male variation in sperm size and shape in tomcats.

Sperm kinematic subpopulations of the American crocodile (Crocodylus acutus)

There has been very limited use of computer assisted semen analysis (CASA) to evaluate reptile sperm. The aim of this study was to examine sperm kinematic variables in American crocodile (Crocodylus acutus) semen samples and to assess whether sperm subpopulations could be characterized. Eight ejaculates (two ejaculates/male) from four sexually mature captive crocodiles were obtained. An ISAS®v1 CASA-Mot system, with an image acquisition rate of 50 Hz, and ISAS®D4C20 counting chambers were used for sperm analyses. The percentages of motile and progressively motile spermatozoa did not differ among animals (P > 0.05) but there was a significant animal effect with regards to kinematic variables (P < 0.05). Principal component (PC) analysis revealed that kinematic variables grouped into three components: PC1, related to velocity; PC2 to progressiveness and PC3 to oscillation. Subpopulation structure analysis identified four groups (P < 0.05), which represented, on average, 9.8%, 32.1%, 26.8%, and 31.3% of the total sperm population. Males differed in the proportion of sperm in each of the kinematic subpopulations. This new approach for the analysis of reptile sperm kinematic subpopulations, reflecting quantifiable parameters generated by CASA system technology, opens up possibilities for future assessments of crocodile sperm and will be useful in the future development of assisted reproduction for these species.

Novel Proteomic Profiling of Epididymal Extracellular Vesicles in the Domestic Cat Reveals Proteins Related to Sequential Sperm Maturation with Differences Observed between Normospermic and Teratospermic Individuals

Extracellular vesicles (EVs) secreted by the epididymal epithelium transfer to spermatozoa key proteins that are essential in promoting motility and subsequent fertilization success. Using the domestic cat model, the objectives were to (1) characterize and compare protein content of EVs between segments of the epididymis, and (2) compare EV protein compositions between normo- and teratospermic individuals (producing >60% of abnormal spermatozoa). Epididymal EVs from adult cats were isolated and assessed via liquid chromatography tandem MS. Both male types shared 3008 proteins in total, with 98 and 20 EV proteins unique to normospermic and teratospermic males, respectively. Expression levels of several proteins changed between epididymal segments in both male types. Several proteins in both groups were related to sperm motility (e.g. hexokinase 1, adenylate kinase isoenzyme) and zona pellucida or oolemma binding (e.g. disintegrin and metalloproteinase domain proteins, zona binding proteins 1 and 2). Interestingly, seven cauda-derived EV proteins trended downward in teratospermic compared with normospermic males, which may relate to poor sperm quality. Collective results revealed, for the first time, EV proteins related to sequential sperm maturation with differences observed between normospermic and teratospermic individuals.

Sperm kinematics and subpopulational responses during the cryopreservation process in caprine ejaculates

Sperm cryopreservation in goats has been a challenge for many years due to the detrimental effects of seminal plasma enzymes produced by the bulbo-urethral glands which catalyse the hydrolysis of lecithins in egg yolk to fatty acids and lysolecithins which are deleterious to spermatozoa. This fact implies to carry out additional processing steps during sperm cryopreservation for seminal plasma removal triggering different sperm responses which may affect sperm functionality. The objective of the present study was to determine specific sperm subpopulation responses in different handling steps during the cryopreservation process by using functional sperm kinematic descriptors in caprine ejaculates. Buck ejaculates (n = 40) were analysed for sperm concentration, viability, morphology and acrosome integrity. Moreover, sperm motility was assessed using a computer-assisted sperm analysis (CASA) system after five different handling steps (fresh sperm, 1st washing, 2nd washing, cooling and frozen-thawed sperm) during a standard cryopreservation protocol for goat semen. The results were analysed using Principal Component Analysis (PCA) and multivariate clustering procedures to establish the relationship between the distribution of the subpopulations found and the functional sperm motility in each step. Except for the 1st and 4th steps, four sperm kinematic subpopulations were observed explaining more than 75% of the variance. Based on velocity and linearity parameters and the subpopulations disclosed, the kinematic response varies among processing steps modifying sperm movement trajectories in a subpopulation-specific and handling step-dependent manner (p < 0.001). The predominant motile subpopulation in freshly ejaculated buck sperm had very fast velocity characteristics and a non-linear trajectory (41.1%). Washing buck sperm twice altered the subpopulation structure as well as cooling which resulted in a dramatic reduction in sperm velocities (p < 0.01). Frozen-thawed spermatozoa showed similar characteristics to cooled sperm except there was a further increase in linearity with a large proportion of sperm attributed to new slow, linear cluster (32.5%). In conclusion, this study confirms the variability and heterogeneity of goat sperm kinematic patterns throughout the cryopreservation process and suggests that the predominant motility pattern (assayed in vitro via CASA) of high quality spermatozoa might be typified by high speed and a non-linear trajectory. The relationships among the number and distribution of sperm subpopulations and the different handling steps were particularlly relevant, specially after the cooling and the post-thawing steps, when effects derived from these critical handling steps were evident and altered drastically the sperm motion patterns.