Creatine phosphokinase in domestic cat epididymal spermatozoa

Insights into alternative cryoprotectants to freeze sperm of domestic cats

Globalization and habitat destruction pose a significant threat to wildlife felids. Even though conservation banks for genetic materials have been created, the sperm cryopreservation with minimal cell damage is still a great challenge. Thus, this study aimed to compare the effects of two commercial extenders with different concentrations of alternative cryoprotectants on thawed sperm quality of domestic cats. Five adult cats were anaesthetized (using a combination of 40 μg/kg medetomidine associated to 5 mg/kg ketamine), and the semen was collected by electroejaculation (electrical stimulation of 2-3 V). Semen samples were evaluated for sperm characteristics (kinetics, morphology, membrane integrity and morphometry). Subsequently, they were sorted into two aliquots and centrifuged. The aliquots were added to a commercial extender containing 3% glycerol and 2% methylformamide (extender I) or 2% glycerol and 3% methylformamide (extender II), frozen, thawed (37°C/30 s) and reevaluated. Comparatively, the sperm kinetics and membrane integrity of fresh semen were higher (p < .002) than frozen samples in extender I and II. Total and progressive motility were lowest in the thawed samples. However, the subjective analysis indicated high sperm motility, since the kinetics evaluation was impaired by the low cell number in the thawed samples. There were no differences in sperm morphology between the groups. In the sperm morphometric analysis, a significant difference (p = .04) was identified in the length of the intermediate piece in extender II samples compared with fresh and extender I. Thus, it can be concluded that although the concentrations tested did not maintain the kinetic parameters and membrane integrity of spermatozoa after thawing, the extender with a lower concentration of glycerol was less toxic for maintaining the midpiece length.

L-carnitine Supplemented Extender Improves Cryopreserved-thawed Cat Epididymal Sperm Motility

Cryopreservation of epididymal sperm is an effective technique to preserve genetic materials of domestic cats and wild felids when they unexpectedly die. However, this technique inevitably causes detrimental changes of cryopreserved-thawed spermatozoa, for example, by physical damage and excessive oxidative stress. L-carnitine is an antioxidant that has been used to improve sperm motility in humans and domestic animals. This study aimed to investigate the effects of L-carnitine on cat epididymal sperm quality following cryopreservation and thawing. After routine castration, cauda epididymides were collected from 60 cat testes. The epididymal spermatozoa from 3 cauda epididymides were pooled as 1 replicate. Spermatozoa samples (16 replicates) were examined for spermatozoa quality and then randomly divided into 4 groups: 0 mM L-carnitine (control), 12.5 mM, 25 mM and 50 mM L-carnitine. The sperm aliquots were then equilibrated and conventionally frozen. After thawing, sperm motility, plasma membrane integrity, DNA integrity and acrosome integrity were evaluated. The 25 mM L-carnitine significantly improved sperm motility compared with a control group (p<0.05), although this was not significantly different among other concentrations. In conclusion, supplementation of 25 mM L-carnitine in freezing extender improves cauda epididymal spermatozoa motility. The effects of L-carnitine on the levels of oxidative stress during freezing and thawing remains to be examined.

Artificial neural networks for the definition of kinetic subpopulations in electroejaculated and epididymal spermatozoa in the domestic cat

This study was designed for the identification of different sperm kinetic subpopulations in feline semen using artificial neural networks (ANNs) and for the evaluation of the effect of ejaculation on motility patterns of these subpopulations. Seven tomcats presented for routine orchiectomy were electroejaculated, and after 5 days, orchiectomized and epididymal tail sperms were collected. Sperm motility characteristics were evaluated using a computer-assisted sperm analyzer that provided individual kinetic characteristics of each spermatozoon. A total of 23 400 spermatozoa for electroejaculated and 9200 for epididymal tail samples were evaluated using a multivariate approach, comprising principal component analysis and ANN classification. The multivariate approach allowed the identification and characterization of three different and well-defined sperm subpopulations. There were significant differences before (epididymal tail spermatozoa) and after (electroejaculated sperm) ejaculation in sperm kinetic subpopulation characteristics. In both epididymal and ejaculated samples, the majority of subpopulation was characterized by high velocity and progressiveness; however, the electroejaculated samples showed significantly higher values, suggesting that the microenvironment of the epididymal tail could affect the sperm motility or, alternatively, seminal plasma could increase the kinetic characteristics of the spermatozoa, indicating that only after ejaculation, the spermatozoa express their motility potential. Nevertheless, further studies are required to clarify the functional significance of each kinetic subpopulation.

The impact and potential etiology of teratospermia in the domestic cat and its wild relatives

Teratospermia (production of >60% morphologically abnormal sperm/ejaculate) is relatively common among various species in the family Felidae, which is comprised of 37 species. Over two decades of research in this area have produced a significant understanding of the phenotypic expression, its impacts on sperm function and etiology. There is good evidence suggesting that a reduction in genetic diversity contributes to this phenomenon. Results to date demonstrate that spermatozoa from teratospermic donors are compromised in the ability to undergo capacitation and the acrosome reaction, penetrate the zona-pellucida, fertilize conspecific oocytes and survive cryopreservation. Recent studies also reveal abnormalities in chromatin integrity in sperm from teratospermic donors, which, interestingly, fails to impact fertilization or embryo development after intracytoplasmic sperm injection. Through planned inbreeding studies, we now have established that teratospermic cats also produce more spermatozoa by virtue of more sperm producing tissue, more germ cells per Sertoli cell and reduced germ cell loss during spermatogenesis. Overall, it now is clear that gain in sperm quantity is achieved at the expense of sperm quality, suggesting an extensive disruption of normal testicular function in teratospermic donors. Preliminary studies on testicular gene expression in teratospermic cats have also revealed abnormal expression patterns. These findings have markedly increased our understanding of testis biology in the teratospermic donor and reaffirm the value of cats, including wild species, as models for studying novel regulatory mechanisms controlling spermatogenesis and spermiogenesis.

Sperm maturation in the domestic cat

The epididymis is essential for sperm development and maturation, and, subsequently, the ability of spermatozoa to penetrate and fertilize the female gamete. Functional differences in segments of the long tubule are reflected by histological differences among epididymal regions. The feline epididymis can be divided into six different regions according to their histological differences. A marked increase in sperm concentration occurs between regions 2 and 3, indicating resorption of fluid in region 2, a concept supported by the histological characteristics of the epithelium. At the transition between regions 4 and 5, located between the caput and corpus epididymides, histological characteristics change from being that of a maturation function to being typical of a storage function. Migration of the cytoplasmic droplet and induction of motility occur in this same region. Proteins are secreted from epithelial cells in the feline epididymis by merocrine and apocrine secretion, although the functions of different feline epididymal proteins have not been determined. Hypotaurine, taurine and, probably, alkaline phosphatase are produced by the feline epididymis. During epididymal transit the percentage of immature, unviable and morphologically abnormal spermatozoa decreases, indicating the existence of a mechanism that removes abnormal spermatozoa. In contrast, the percentage of spermatozoa with abnormal tails increases slightly during epididymal transit. Most of the distal droplets present on spermatozoa in the cauda epididymis are lost at or after ejaculation. Additional knowledge of the feline epididymis should be beneficial for developing sperm preservation protocols and advance the prospects for effective male contraceptive methods.

Comparison between different markers for sperm quality in the cat: Diff-Quik as a simple optical technique to assess changes in the DNA of feline epididymal sperm

The majority of wild felids, as well as some domestic cats, have low sperm concentration in their ejaculates, and a high proportion of abnormal spermatozoa. We have employed several possible semen quality markers to further characterize cat epididymal sperm. Methods included possible apoptotic reporters, such as the annexin V assay to monitor exposure of phosphatidylserine (PS) on the outer leaflet of the plasma membrane, as well as cell integrity; and the TUNEL assay to quantify DNA breaks. Sperm surface ubiquitination, another putative marker of sperm quality, was also monitored. The annexin V assay revealed a high percentage of sperm with PS exposure, and the TUNEL assay pointed to high levels (13+/-12%) of sperm with DNA breaks. Correlations were found between apoptotic markers (but not ubiquitination) and semen parameters. In parallel to this analysis, cat sperm morphology was evaluated using the Diff-Quik optical stain, which has been used in human reproduction laboratories. Several types of abnormalities could be characterized with this method. Remarkably, head staining abnormalities detected using the Diff-Quik staining method were strongly correlated with, and could accurately predict, sperm DNA defects detected in the same sample using the TUNEL assay. We therefore suggest that sperm morphology analysis using Diff-Quik could be used in field conditions to assess sperm status, due to the simplicity of the procedure and the equipment involved.

Isolation, culture and characteristics of epididymal epithelial cells from adult cats

A tissue-culture system in which cells retain defined ultrastructural and functional characteristics was established to provide a basis for functional investigations of the epididymal duct in the cat. A widely used culture protocol for rat epididymal epithelium was used as a starting point and subsequently modified. The cellular population of the cat's epididymal epithelium was isolated by successive collagenase and trypsin digestion. A high yield of isolated cells obtained with good viability, were cultured in DMEM/F12 medium supplemented with foetal bovine serum, in absence or in presence of additional dihydrotestosterone (1 nM). The plated primary cultures reached confluence within 5-8 days, producing a monolayer of cohesive cells. Samples taken after 6 days in culture were processed for transmission and scanning electron microscopies. Immunocytochemical staining was used to estimate the purity of the epithelial cell population in the monolayers. The cell cultures displayed several functional traits of in vivo epithelia, including [35S] hypotaurine and [35S] taurine production. These results demonstrate that primary cultures of epididymal epithelial cells isolated from sexually mature cats maintain several differentiated characteristics of the intact organ and therefore provide a valuable system for the study of epididymal epithelial cell functions, metabolic activities and their regulation in cats.

Identification, proteomic profiling, and origin of ram epididymal fluid exosome-like vesicles

Small membranous vesicles, between 25- and 75-nm diameter, were collected by high-speed centrifugation from the ram cauda epididymal fluid and were found to be normal constituents of this fluid and of the seminal plasma. The SDS-PAGE protein pattern of these vesicles was specific and very different from that of the caudal fluid, seminal plasma, sperm extract, and cytoplasmic droplets. After two-dimensional electrophoresis separation and mass spectrometry analysis, several proteins were identified and grouped into i) membrane-linked enzymes, such as dipeptidyl peptidase IV (DPP-IV), neprilysin (NEP), phosphodiesterase-I (E-NPP3), and protein G-beta; ii) vesicle-associated proteins, such as lactadherin (MFEG8-PAS6/7) and vacuolar ATPase; iii) several cytoskeleton-associated proteins, such as actin, ezrin and annexin; and iv) metabolic enzymes. The presence of some of these proteins as well as several different hydrophobic proteins secreted by the epididymis was further confirmed by immunoblotting. These markers showed that the majority of the vesicles originated from the cauda epididymal region. The physical and biochemical characteristics of these vesicles suggest they are the equivalent of the exosomes secreted by several cell types and epithelium. The main membrane-linked proteins of the vesicles were not retrieved in the extract from cauda or ejaculated sperm, suggesting that these vesicles did not fuse with sperm in vivo.

Postthaw Evaluation of In Vitro Function of Epididymal Spermatozoa from Four Species of Free-Ranging African Bovids1

An improved understanding of reproductive physiology in nondomestic bovids is necessary for the development of assisted reproductive technologies (ARTs) for use in the conservation of endangered bovids. In this study, epididymal spermatozoa were recovered from blesbok (Damaliscus dorcas phillipsi), African buffalo (Syncerus caffer), springbok (Antidorcas marsupialis), and black wildebeest (Connochaetes gnou) following organized culls in South Africa. Our objectives were 1) to characterize the quality of epididymal spermatozoa, 2) evaluate the effectiveness of a cryopreservation protocol, and 3) compare postthaw sperm longevity (motility, viability, and acrosomal integrity) and functionality in two culture media with two capacitation reagents (caffeine and heparin). Following recovery, spermatozoa were diluted in EQ extender, slow-cooled, and frozen in the presence of 5% glycerol. Thawed spermatozoa were separated on a Percoll gradient and diluted in fertilization media (SOF for fertilization [SOFfert]; 0.6% BSA, 0.0 mM glucose, 25.0 mM NaHCO(3)) or modified SOFfert (1.2% BSA, 1.5 mM glucose, 37.0 mM NaHCO(3)) and either heparin or caffeine, and incubated for 6 h. Spermatozoa from these species maintained an average of 64% initial motility after thawing. Incubation medium and capacitation reagent had species-specific effects on the motility, viability, and acrosomal integrity of spermatozoa, suggesting ART procedures need to be optimized for each species. Springbok spermatozoa were also shown to be competent for in vitro fertilization. Information from this study concerning sperm physiology in blesbok, African buffalo, springbok, and black wildebeest will be useful in the development of ART for the conservation of these and other species of bovids.

The effect of Equex STM paste and sperm morphology on post-thaw survival of cat epididymal spermatozoa

Cryopreservation of epididymal spermatozoa is a potentially valuable tool for preserving genetic material from individuals of endangered species that die accidentally. Improvement of sperm-freezing protocols would increase the efficacy of gene banking from endangered felids, and the domestic cat can be used as a model for the wild felids. Addition of the detergent Equex STM paste to semen freezing extenders has been found to improve post-thaw survival and longevity of spermatozoa from various species but has never been tested for cat spermatozoa. Spermatozoa from cats with a high percentage of morphologically abnormal spermatozoa are more susceptible for cold injury and osmotic stress than spermatozoa from normozoospermic cats. Therefore, the aims of this study were to investigate: (a) if addition of Equex STM paste to a semen freezing extender would improve post-thaw sperm survival, and (b) if there is a relation between the percentage of morphologically normal spermatozoa and cryopreservation induced damage in cat epididymal spermatozoa. Spermatozoa harvested from epididymides of 10 male cats were frozen in a Tris egg yolk extender with or without the addition of Equex STM paste (0.5%, v/v). Sperm motility, membrane integrity and acrosomal status were evaluated immediately after harvesting, and at 0, 2, 4 and 6 h post-thaw. Sperm membrane integrity and acrosomal status were also evaluated after cooling to 4 degrees C, just before freezing. Cooling did not cause significant damage to the spermatozoa, whereas freezing damaged sperm membranes and acrosomes. Addition of Equex to the freezing extender had a significant positive effect on the percentage of intact acrosomes immediately after thawing (P > 0.05), but had a negative effect on the longevity of the spermatozoa; the percentages of membrane intact and motile spermatozoa being significantly lower in the presence of Equex than in the controls at 6h after thawing. The percentage of morphologically normal spermatozoa was not found to be correlated with either cryopreservation induced acrosome or plasma membrane damage, or with post-thaw motility (P > 0.05). The results clearly show that addition of Equex STM paste in the freezing extender protects the acrosomes of cat epididymal spermatozoa during the freezing--thawing process, but reduces the sperm longevity during in vitro incubation at 38 degrees C. Our results also indicate that the percentage of morphologically normal epididymal spermatozoa is not correlated with cryopreservation induced sperm damage using the described freezing protocol.

Quantity rather than quality in teratospermic males: a histomorphometric and flow cytometric evaluation of spermatogenesis in the domestic cat (Felis catus)

Teratozoospermia (ejaculation of <40% morphologically normal sperm) commonly occurs within the Felidae, including certain domestic cats, but the cellular and molecular mechanisms that give rise to this phenomenon remain unknown. This study quantified spermatogenesis to identify differential dysfunctions in teratospermic versus normospermic (>60% normal sperm/ejaculate) domestic cats. Sperm used were from electroejaculates and cauda epididymides. Testes from 10 normo- and 10 teratospermic males were obtained by castration and then evaluated by histomorphometry, flow cytometry, and testicular testosterone enzyme immunoassay. Some morphometric traits (tubular diameter, epithelium height, interstitial area, number of Leydig cells, and blood vessels per cross-section) as well as testicular testosterone concentrations were similar between groups, but testicular volume was greater in teratospermic males. Stage frequencies differed also between both cat populations, suggesting possible dysfunctions in spermiation. Quantification of cell populations in most frequent stages revealed more spermatogenic cells and fewer Sertoli cells per tubule cross-section as well as per tissue unit in teratospermic donors. Hence, the ratio of spermatogenic cells per Sertoli cell was elevated in the teratospermic cat. DNA flow cytometry confirmed higher total spermatogenic and meiotic transformations in teratospermic males. In summary, compared with normospermic counterparts, teratospermic cats have a higher sperm output achieved by more sperm-producing tissue, more germ cells per Sertoli cell, and reduced germ cell loss during spermatogenesis. Gains in sperm quantity are produced at the expense of sperm quality.