The use of in vitro fertilization techniques to investigate the fertilizing ability of bovine sperm with proximal cytoplasmic droplets

An Update on Male Canine Infertility

Infertility in the dog is a common reason for presentation of stud dogs for assessment with veterinarians. This article aims to discuss and outline some of the tests that can be done to try to ascertain the underlying cause of abnormalities found in a semen assessment. Topics discussed are semen alkaline phosphatase measurement, retrograde ejaculation assessment, ultrasound of the male reproductive tract, semen culture, human chorionic gonadotropin response testing, dietary assessment for phytoestrogens, environmental impacts on spermatogenesis, testicular biopsy, supplements to improve semen quality and quantity, and when to expect an improvement in semen quality after starting treatment.

Germplasm cryopreservation in bulls: Effects of gonadal tissue type, cryoprotectant agent, and freezing-thawing rates on sperm quality parameters

Germplasm preservation is crucial for reproductive programs involving farm and endangered species. This study describes the effects of slow-uncontrolled cryopreservation protocols on bovine sperm associated with testicular or epididymal tissues. Samples from the testis or epididymis (cauda) were cut into ∼0.5 or 1 cm³ fragments and cryopreserved using Me2SO (Dimethyl Sulfoxide) or glycerol-based cryoprotectants. Sperm were collected from testicular or epididymal tissue before and after freezing-thawing (38 °C or 40 °C) and kept at room temperature (RT) or 4 °C during handling. The parameters studied were viability, membrane integrity (HOS), motility, acrosome integrity, chromatin, and morphology. Pre-freezing parameters were lower in testicular sperm than epididymal: HOS+ and DNA integrity (P < 0.05). Normal-% pre-freezing testicular sperm morphology was lower than epididymal (43.3 ± 1.8% vs. 65.3 ± 14.8%). All testicular RT-kept sperm parameters decreased post-freezing, except for acrosome integrity, which remained constant (P > 0.05). There were no differences in Me2SO-frozen tissue sizes (P > 0.05). All epididymal RT-kept sperm parameters dropped post-freezing except for the constant DNA integrity (P > 0.05). 4^oC-kept sperm were fitter than those at RT (P < 0.05). 4^oC-kept testicular sperm viability, DNA, and membrane integrities declined after 38 °C or 40 °C thawing (P < 0.05). Acrosome integrity and motility remained unchanged after freezing (P > 0.05). 4^oC-kept epididymal sperm acrosome integrity, motility, and HOS+% severely dropped post-thawing (P < 0.05). Viability and DNA integrity were unchanged (38 °C vs. 40 °C; P > 0.05). Overall, post-freezing sperm morphology was unaffected (P > 0.05), but Dag defect was significantly lower in testicular samples (P < 0.05). Whole-epididymis parameters were maintained up to 24h at 4 °C (P > 0.05). In conclusion, testis-epididymis freezing protocols should use small tissue pieces, Me2SO-based cryoprotectants, and 4°C-kept samples to reduce sperm damage.

Aniline blue test for sperm protamination-a valuable add-on to the bull breeding soundness evaluation

Bull breeding soundness evaluation (BBSE) is the most common procedure used to predict bull potential fertility. However, the use of traditional methods for semen evaluation can affect its reliability. The inclusion of additional advanced test in BBSE may increase its accuracy. This study aimed to investigate the correlation between the degree of sperm protamination and BBSE main parameters of scrotal circumference (SC), progressive motility (PM), morphologically normal sperm (NS), and different categories of morphological defects. In addition, to determine the correlation between the three methods used for protamine assessment, five Brangus bulls were subjected to the BBSE. Semen samples were collected via electro-ejaculation and evaluated using traditional methods. Three different methods were used to determine the degree of sperm protamination: aniline blue (AB) staining, chromomycin A3 staining with fluorescent microscope (CMA3-FLM), and CMA3 with flow cytometry (CMA3-FCM). Sperm protamine deficiency assessed using the three methods exhibited significant differences among bulls according to their classification by BBSE, and showed significant negative correlation with semen quality parameters of NS and PM. A significant positive correlation was found between AB positivity and morphological abnormalities. The three methods used for protamine assessment also revealed significant positive correlations. Among the three tests, AB staining was the cheapest and easiest test that offers an objective assessment method for sperm protamination. Hence, it can be concluded that the assessment of protamination using AB staining test might serve as an additional valuable parameter or a replacement whenever detail sperm motility and morphology analyses in conducting BBSE to predict bull fertility are not possible.

Compensability of an enhanced incidence of spermatozoa with cytoplasmic droplets in boar semen for use in artificial insemination: a single cell approach

This single cell study aimed to clarify whether an elevated incidence of sperm with a retained cytoplasmic droplet (CD) can be compensated by a higher sperm number in boar semen doses to maintain fertility. Cluster analysis of motile spermatozoa (ten boars) revealed that spermatozoa with a CD are underrepresented in the fast, linearly moving sperm cohort compared to morphologically normal sperm. Nonetheless, the response to the motility stimulator procaine was barely affected in spermatozoa with distal CD (Cramer's V = 0.14), but moderately affected in sperm with proximal CD (V = 0.28). Viability was lower in sperm with distal CD (p < 0.05) but not with proximal CD compared to normal sperm during 168 h storage of extended semen samples (n = 11) and subsequent thermic stress. Morphologically normal sperm from normospermic samples (n = 10) or samples with a high incidence (≥ 15%) of sperm with CD (n = 9) had similar motility patterns and responses to procaine. The origin of morphologically normal sperm had no effect on sperm viability (p > 0.05; n = 26). In conclusion, a moderately enhanced prevalence of sperm with CD seems to be compensable by an increase in sperm numbers in boar semen doses.

Comprehensive functional analysis reveals that acrosome integrity and viability are key variables distinguishing artificial insemination bulls of varying fertility

In vitro methods of assessing bull semen quality in artificial insemination (AI) centers are unable to consistently detect individuals of lower fertility, and attempts to reliably predict bull fertility are still ongoing. This highlights the need to identify robust biomarkers that can be readily measured in a practical setting and used to improve current predictions of bull fertility. In this study, we comprehensively analyzed a range of functional, morphological, and intracellular attributes in cryopreserved spermatozoa from a selected cohort of Holstein Friesian AI bulls classified as having either high or low fertility (n = 10 of each fertility phenotype; difference of 11.4% in adjusted pregnancy rate between groups). Here, spermatozoa were assessed for motility and kinematic parameters, morphology, acrosome integrity, plasma membrane lipid packing, viability (or membrane integrity), superoxide production, and DNA integrity. In addition, spermatozoa were used for in vitro fertilization to evaluate their capacity for fertilization and successful embryo development. The information collected from these assessments was then used to phenotypically profile the 2 groups of bulls of divergent fertility status as well as to develop a model to predict bull fertility. According to the results, acrosome integrity and viability were the only sperm attributes that were significantly different between high- and low-fertility bulls. Interestingly, although spermatozoa from low-fertility bulls, on average, had reduced viability and acrosome integrity, this response varied considerably from bull to bull. Principal component analysis revealed a sperm phenotypic profile that represented a high proportion of ejaculates from low-fertility bulls. This was constructed based on the collective influence of several sperm attributes, including the presence of cytoplasmic droplets and superoxide production. Finally, using the combined results as a basis for modeling, we developed a linear model that was able to explain 47% of the variation in bull field fertility in addition to a logistic predictive model that had a 90% chance of distinguishing between fertility groups. Taken together, we conclude that viability and acrosome integrity could serve as fertility biomarkers in the field and, when used alongside other sperm attributes, may be useful in detecting low-fertility bulls. However, the variable nature of low-fertility bulls suggests that additional, in-depth characterization of spermatozoa at a molecular level is required to further understand the etiology of low fertility in dairy bulls.

The Role of Sperm Morphology Standards in the Laboratory Assessment of Bull Fertility in Australia

The lack of standardization in the laboratory assessment of semen questions the reliability of semen analysis, and makes meaningful interpretation of these evaluations impossible. We herein describe a standardization program for morphology assessment currently in place in Australia and outline the methods used, both for the categorization of the abnormalities, including newly described abnormalities, and those that permit standardized microscopic assessment between laboratories.

Seminal plasma Alters surface Glycoprofile of dromedary camel cryopreserved epididymal spermatozoa

The high viscosity of Camelidae semen continues to present a major impediment for its application in assisted reproduction technology. The exposure of epididymal spermatozoa (ES) to seminal plasma (SP) may provide an approach to enhance the development of assisted reproductive techniques in these important domestic species. Since the sperm glycocalyx plays a key role in reproduction we aimed to evaluate whether SP exposure modifies the surface glycosylation patterns of cryopreserved dromedary ES. Epididymal sperm was collected through retrograde flushing of the cauda epididymidis that were obtained from orchidectomized mature dromedary bulls. The collected samples were then cryopreserved after dilution with a tris citrate clarified egg yolk extender, with and without the supplementation of 15% SP. Post-thaw carbohydrate surface profiles of both control and SP-treated spermatozoa were analyzed using 15 fluorescent lectins. Morpho-functional properties were also investigated via computer assisted sperm analysis. Lectin-binding analysis of the glycocalyx in control sperm revealed the presence of (1) N-glycans terminating with lactosamine (Con A, PHA-L, and RCA₁₂₀), in both acrosomal and tail regions. Whilst (2) α2,3-/α2,6-linked sialic acids (MALII, SNA), and O-linked glycans terminating with a single N-acetylgalactosamine residue (Tn antigen) (HPA, SBA) along with galactoseβ1,3N-acetylgalactosamine (T antigen) (PNA) were observed in the acrosomal cap. The expression of both N-acetylglucosamine (sWGA and GSA II) and terminalαgalactose (GSA I-B₄) residues was also noted in the acrosomal cap region of control sperm. Compared with controls, SP treated samples displayed: 1) the appearance of bisected di-triantennary complex-type N-glycans (PHA-E), terminating with lactosamine, as well as an increase of O-glycans terminating with Tn and T antigens in both the acrosomal and tail regions; 2) an increase in glycans containing α2,6-linked sialic acid, N-acetylglucosamine, and αgalactose in the tail region. The cytoplasmic droplets of both control and seminal plasma-treated sperm bound Con A, PHA-E, PHA-L, RCA₁₂₀, HPA, PNA, sWGA, GSA I-B₄, and GSA II. These results indicate that SP treatment affects the glycan composition of the dromedary camel ES glycocalyx. More comprehensive studies are required in order to evaluate the fertilization capacity of SP-treated ES in order to facilitate its application in dromedary camel assisted reproduction technology.

The effect of varicocele on semen quality in boars exposed to heat stress

Semen quality has a dramatic impact on reproductive efficiency in the swine industry, influencing both conception rate and litter size. The objective of this study was to assess whether the presence of varicocele hinders semen quality in both thermoneutral and heat stress (HS) conditions. At approximately 6 mo of age, ultrasonography was used to measure left and right pampiniform plexus area in order to detect varicocele in maternal line boars at the University of Nebraska-Lincoln. Between 10 and 12 mo of age, semen was collected from each boar (n = 28) twice weekly. Boars were collected under thermoneutral conditions, were then heat stressed for 7 d to exacerbate any semen quality issues, and semen was collected post-HS for 6 wk. Sperm characteristics were determined by computer-assisted semen analysis. The presence of varicocele had a significant effect on sperm concentration (P = 0.04) and trended toward significance for mean sperm head area (P = 0.06) throughout the duration of the study. An interaction existed between varicocele and collection time point at weeks 2-5 post-HS for distal droplet percentage, suggesting that boars with varicocele were possibly more susceptible to heat-stress-induced semen quality issues than boars without varicocele. Moreover, semen quality was reduced in boars with versus without varicocele under both thermoneutral and HS conditions. Therefore, detection of varicocele by ultrasound could represent a potential marker of fertility in young boars or as a component trait in selection indices for fertility.

Effect of breed, age, season and region on sperm morphology in 11,387 bulls submitted to breeding soundness evaluation in Australia

This study reports the distribution of sperm morphology defects by breed, age, season and region of 11,387 bulls in 500 herds in Australia and near Pacific Islands during annual BBSE. Bull location was divided into 4 broad climatic regions based upon temperature, vegetation and climatic risk. Taking into account the impact of age, season, region, and breed there were differences between breeds in both percent morphologically normal sperm and in some individual categories of sperm abnormality (P < 0.001). Independent of breed, season and region, proximal droplets were significantly increased in bulls less than 20 months of age. This is the first study to comprehensively collect data from this wide geographical area and compare sperm morphology profiles among the Bos indicus and Bos taurus breeds. The findings of this study will act as a guide for veterinary practitioners and cattle breeders in the proportion of bulls that can be expected to pass the PNS test, by breed, age and region, based on a robust data set.

Influence of distiller's dried grains with solubles on ram lamb growth and reproductive traits

The hypothesis of this experiment was that increasing the inclusion level of distiller's dried grains with solubles (DDGS) in the diets would decrease semen quality but have no negative effects on growth performance. Following the removal of DDGS from the diet, it was hypothesized that the ram lambs would recover and become reproductively sound, independent of treatment. To test this hypothesis, Suffolk and Hampshire ram lambs (n = 112) were allocated to 4 treatments (n = 4 pens per treatment; 7 rams per pen) in a completely randomized design. Dietary treatments were 60% corn, 25% oats, and 15% commercial lamb pellet (CON), 15% of the ration as DDGS substituted for corn (% DM basis; 15DDGS), 30% of the ration as DDGS substituted for corn (% DM basis; 30DDGS), and 45% of the ration as DDGS substituted for corn (% DM basis; 45DDGS). Lambs were fed for 112 d on their respective treatment, after which they were placed on the CON ration until day 168. Lambs were weighed on consecutive d at the beginning (days 0 and 1) and end (days 167 and 168) of the study. Scrotal circumference was measured on all lambs on days 84, 112, 140, and 168. Semen samples were collected on a subset of 64 rams (4 rams per pen) to evaluate semen quality on days 84, 112, 140, and 168. Blood samples were collected on the same subset of rams every 14 d throughout the study. A quadratic effect on BW on day 112 and overall BW (P = 0.03 and P = 0.005, respectively), ADG on day 112 and overall ADG (P = 0.02 and P = 0.02, respectively), DMI (P = 0.007) on day 112, and a cubic effect (P = 0.05) for overall G:F were observed. Overall and day 168 scrotal circumference had a quadratic (P = 0.05) response. A linear increase in spermatozoa concentration on day 168 was observed (P = 0.03) as DDGS concentration increased in the treatment diets, although rams in this stage of the study were no longer receiving DDGS. Overall, testosterone concentrations exhibited a linear decrease (P = 0.005) as DDGS increased in the diet. The linear increase (P = 0.04) on day 168 in morphologically normal sperm as DDGS increased in the diets indicated that all rams, regardless of treatment, would have passed a reproductive soundness exam. In the current study, no negative effects were observed in lamb feedlot or reproductive traits due to increasing DDGS in the diet, indicating that DDGS may be included at levels up to 45% of growing lamb diets.

Transmission electron microscopy analysis of the origin and incidence of sperm intranuclear cytoplasmic retention in fertile and teratozoospermia men

The human sperm nucleus contains cytoplasm. However, the origin and incidence of human sperm intranuclear cytoplasmic retention (INCR) remain unknown. The objectives of this study were to observe the morphological origin of INCR within the seminiferous epithelium and investigate the incidence of INCR in fertile and teratozoospermia men using transmission electron microscopy (TEM). By TEM, INCR initially appeared in elongating round spermatid nuclei and varied in size, number, shape, content, location and distribution within sperm nuclei. The teratozoospermia group (n = 16) demonstrated a higher incidence of INCR than did the fertile group (n = 16) (17.6 ± 5.2% vs. 9.7 ± 3.4%; p = 0.000). In the fertile group, no correlations were found between the incidence of INCR and abnormal sperm morphology, nuclear vacuole, acrosome integrity, motility or concentration (p > 0.05). However, the incidence of INCR exhibited a positive relationship with sperm abnormal morphology in the teratozoospermia group (r = 0.616, p = 0.011). These results demonstrate that INCR occurs in the early process of spermatogenesis and is an alteration found in the nucleus. Spermatozoa from teratozoospermia men contained more INCRs than those from fertile males. More attention should be paid to the possibility of spermatozoa containing INCR when using spermatozoa with abnormal head morphology for clinical or diagnostic purposes.

Morphological study of boar sperm during their passage through the female genital tract

Once deposited in the female tract, sperm face a series of challenges that must be overcome to ensure the presence of an adequate normal sperm population close to the site of fertilization. Our aim was to evaluate the influence of the uterine milieu on boar sperm morphology. In experiment 1, sperm morphology was evaluated in the backflow (60 min after insemination) and within the uterotubal junction (UTJ) (collected ~24 h after insemination) following intrauterine sperm deposition (n = 6) and compared with the morphology of the sperm in the insemination dose. In experiment 2, the influence of the uterine fluid (UF) on sperm morphological modifications was evaluated. For this purpose, ejaculated (n = 4) and epididymal (n = 4) sperm were in vitro incubated with or without UF for 2 and 24 h. In both experiments, sperm were classified as normal, having a cytoplasmic droplet (proximal or distal) or having tail defects. The results of experiment 1 pointed to an increase in morphologically abnormal sperm collected in the backflow (27.70%) and a reduction of the same in the UTJ (2.12%) compared with the insemination dose (17.75%) (P < 0.05). In experiment 2, incubation of ejaculated sperm with UF did not provoke any morphological modifications; however, when epididymal sperm were incubated with UF, a pronounced increase in the percentage of normal sperm was evident after 24 h compared with the initial dose (from 25.77% to 53.58%, P < 0.05), mainly due to distal cytoplasmatic droplet shedding (53.22 vs. 20.20%). In conclusion, almost all the sperm that colonize the UTJ had a normal morphology, with part of the abnormal sperm having been discarded in the backflow and part selected/modified on their way to the oviduct. UF seems to influence cytoplasmic distal droplet removal, as demonstrated previously in seminal plasma.

Left-sided grade 3 varicocele may affect the biological function of the epididymis

OBJECTIVE

Varicocele is present in approximately 30-40% of men evaluated for infertility and in 10-20% of the general male population, but the association between varicocele, compromised semen quality and male infertility remains unclear. This indicates that varicocele may impair spermatogenesis or in some other way mitigate sperm quality. Better understanding of criteria for the selection of men who will benefit from varicocele repair would improve the clinical management of men with impaired semen quality and varicocele.

MATERIAL AND METHODS

To further understand the effect of varicocele repair by embolization in men with grade 3 varicocele, 50 men referred for infertility with varicocele were evaluated before and after embolization.

RESULTS

There was a significant improvement in total sperm count (25.5 ± 4.7 million to 78 ± 11 million, p < 0.001) and sperm motility (slowly and rapidly progressive) (31.5 ± 2.9% to 45 ± 2.5%, p < 0.001) after spermatic vein embolization, comparing baseline to 3 month post-treatment follow-up data. Furthermore, alpha-glucosidase (specific epididymis-derived protein) increased from 61.7 ± 5.7 U to 84.7 ± 7.0 U (p < 0.05) and sperm droplets decreased from 14.2 ± 1.5% to 11.0 ± 1.0% (p < 0.05).

CONCLUSION

The results indicate improved epididymal function and suggest that left-sided grade 3 varicocele may affect the epididymis in addition to effects on the testis.

Proteomic analyses reveal a role of cytoplasmic droplets as an energy source during epididymal sperm maturation

A small portion of cytoplasm is generally retained as the cytoplasmic droplet (CD) on the flagellum of spermatozoa after spermiation in mice. CDs are believed to play a role in osmoadaptation by allowing water entrance or exit. However, many lines of evidence suggest that CDs may have roles beyond osmoregulation. To gain more insights, we purified CDs from murine epididymal spermatozoa and conducted proteomic analyses on proteins highly enriched in CDs. Among 105 proteins identified, 71 (68%) were enzymes involved in energy metabolism. We also found that sperm mitochondria underwent a reactivation process and glycolytic enzymes were further distributed and incorporated into different regions of the flagellum during epididymal sperm maturation. Both processes appeared to require CDs. Our data suggest that the CD represents a transient organelle that serves as an energy source essential for epididymal sperm maturation.

Immunofluorescence Reveals Ubiquitination of Retained Distal Cytoplasmic Droplets on Ejaculated Porcine Spermatozoa

The purpose of the present study was twofold: 1) to determine if antibodies raised against ubiquitin would recognize antigens associated with the porcine cytoplasmic droplet (CD), and 2) to determine if the same antibody would identify ubiquitinated substrates on the surface of morphologically abnormal boar spermatozoa. Permeabilization with the detergent Triton X-100 (0.05%) showed virtually all CDs to be ubiquitin positive. Distal droplets (DDs) retained in situ on boar spermatozoa were readily labeled following Triton permeabilization, whereas DDs present on nonpermeabilized cells were not. Negative control preparations lacked the ubiquitin staining on the DD. The use of microtubes for fixation and incubation provided clearer images as well as better sperm cell distribution and density than an initial slide-mounted technique. Immunoblotting indicated that larger amounts of ubiquitinated proteins were present in extracts from sperm cells from an ejaculate with an abnormally high percentage of retained DDs (52% DDs) compared to a morphologically normal sample (6% DDs). The primary antibody recognized both mono-ubiquitin of bovine origin (8.5 kd) and human ubiquitin conjugate (35 kd), as demonstrated by Western blot. Preabsorption of the anti-ubiquitin antibody with purified bovine ubiquitin was successful in preventing diaminobenzidine staining of sperm extract from the high DD ejaculate. The presence of antigens recognized by anti-ubiquitin antibodies in the boar sperm CD, coupled with the possibility that superfluous ubiquitin species are detrimental to embryonic development by targeting critical paternally contributed zygotic organelles, raises concerns that retained DDs may be more detrimental to fertility than previously suspected.

Alleviation of reproductive toxicity of gossypol using selenium supplementation in rams

The objective of this study was to evaluate the reproductive toxicity of gossypol and the possible counteracting effect of selenium supplementation in rams. Twenty-five mature crossbred (Barki × Rahamni) rams were randomly divided into 5 equal groups. The first group served as a control (no gossypol in diet). The second and third groups received diets containing free gossypol of 9 and 14 mg·kg(-1) BW·d(-1)(low level and high level of gossypol), respectively. The fourth and fifth groups received the same diets given to the second and third groups, respectively, with an oral administration of 1 mg selenium (as sodium selenite) daily for each animal. Results showed reductions in ejaculate volume (P = 0.028), percentage of dead sperm (P = 0.003), total functional sperm fraction (P < 0.001), and blood serum concentration of testosterone (P < 0.001) in the presence of both levels of gossypol inclusion. Furthermore, high level of gossypol reduced forward motility (P < 0.001) and semen initial fructose concentration (P = 0.002) and increased abnormal-head sperm (P = 0.003) and blood serum concentration of triiodothyronine (P = 0.006). Regardless of selenium supplementation, increasing level of free gossypol in diet resulted in a significant decrease in the percentage of forward motility (P = 0.037) and significant increases in the mean values of sperm concentration (P < 0.001), total sperm output (P = 0.002), percentage of total abnormal sperm (P = 0.058), and abnormal-head sperm (P = 0.016). On the other hand, regardless of levels of gossypol inclusion, selenium supplementation resulted in significant increases in libido (P < 0.001), mean values of ejaculate volume (P < 0.001), percentage of forward motility (P = 0.019), total sperm output (P < 0.001), total functional sperm fraction (P < 0.001), semen initial fructose concentration (P = 0.031), and blood serum concentrations of both testosterone and triiodothyronine (P < 0.001). In conclusion, free gossypol in diet induced adverse effects on semen quality in rams, but selenium supplementation successfully counteracts most of the hazardous effects of gossypol on semen characteristics.

Impact of proximal cytoplasmic droplets on quality traits and in-vitro embryo production efficiency of cryopreserved bull spermatozoa

Background

Proximal cytoplasmic droplets (PCDs), a remnant of germ cell cytoplasm, are common non-specific morphological defects in bovine semen. This study evaluated the effect of higher percentages of PCDs on the quality of frozen-thawed bovine semen, embryo production and early embryo development.

Methods

Three ejaculates from each of five (group 1: PCD ≤ 1%, control) and eight adult Bos indicus bulls (group 2: PCD ≥ 24%) were analysed. Semen samples were examined for: post-thaw motility, vigour of movement, concentration, sperm morphology, slow thermoresistance test (STT), membrane integrity, acrosome status, mitochondrial function using fluorescent probes association (FITC-PSA, PI and JC-1) and sperm chromatin integrity using acridine orange assay. Two bulls from group 2, with 28.5% and 48.5% PCD, respectively, and three bulls from the control group, each with 0% PCD, were selected for IVF (in vitro fertilisation).

Results

Semen analyses revealed a significant correlation (P < 0.01) between increased rates of PCD and sperm quality traits. Nevertheless, no differences were observed in sperm motility and vigour either before or after the STT or in the percentage of intact acrosomes (analysed by differential interference contrast microscopy (DIC) after STT), but membrane integrity, acrosome status (evaluated with FITC-PSA staining method after thawing) and mitochondrial function were reduced, when compared with group 1 (P < 0.05). The higher incidence of PCD was positively correlated to chromatin damage, especially after three hours of incubation at 37°C. IVF showed similar results for bull C2 (group 1, control) and bull P2 (group 2, group with higher PCDs).

Conclusion

Higher PCD levels influenced spermatozoa quality traits. IVF and embryo development data showed that cleavage, blastocyst formation and blastocyst hatching may have been influenced by the interaction of morphology traits and individual bull effects.

Impact of oxidative stress on male fertility - a review

Oxidative stress is a state related to increased cellular damage caused by oxygen and oxygen-derived free radicals known as reactive oxygen species (ROS). It is a serious condition, as ROS and their metabolites attack DNA, lipids and proteins, alter enzymatic systems and cell signalling pathways, producing irreparable alterations, cell death and necrosis. While small amounts of ROS have been shown to be required for several functions of spermatozoa, their excessive levels can negatively impact the quality of spermatozoa and impair their overall fertilising capacity. These questions have recently attracted the attention of the scientific community; however, research aimed at exploring the role of oxidative stress and antioxidants associated with male fertility is still at its initial stages. This review summarises the current facts available in this field and intends to stimulate interest in basic and clinical research, especially in the development of effective methods for the diagnosis and therapy of semen damage caused by oxidative stress.

Maturational changes in the survivability and fertility of fowl sperm during their passage through the male reproductive tract

The objective of this study was to examine whether domestic fowl (Gallus domesticus) sperm undergo maturation in their capacity for survival and fertilization in the male reproductive tract. Sperm collected from the testis, epididymis and the proximal, middle and distal vas deferens were simultaneously stored in vitro in minimum essential medium (MEM) at 39°C for 0, 3 and 6h, and at 4°C for 24 and 48h. Sperm membrane integrity was measured using the dual fluorescent stain SYBR-14/propidium iodide (PI). Aliquots of sperm from the various sites were subjected to artificial insemination (AI) into the uteri of hens to assess the duration of sperm survival in the oviduct and to determine the fertility status of the sperm. Testicular sperm exhibited a very low capacity to survive under in vitro liquid storage conditions, irrespective of the storage temperature used, and in the oviduct, and they had a low ability to fertilize the ovum. On the contrary, sperm from the distal vas deferens had a higher survival rate during in vitro storage periods, a longer life span in the oviduct, and high fertility. Survival and fertilizing capacity of the sperm recovered from the testes increased gradually (P<0.05) from the testes to the distal vas deferens. In conclusion, we suggest that fowl sperm may undergo functional maturation through a process of gradual changes in their survival and fertilization capacities during their passage through the successive parts of the male reproductive tract.

Characteristics of donkey spermatozoa along the length of the epididymis

In mammals, the epididymis has numerous interrelated functions including absorptive and secretory activity that affect luminal environment and cell membrane, and the maturation and storage of sperm. Spermatozoa acquire their motility and fertilizing ability during their passage through the epididymis and the motility of epididymal spermatozoa should be a balance between the maturation of flagellum and the inhibition of the flagellar machinery. In this study maturational change in sperm characteristics were evaluated in the epididymis of donkey. Spermatozoa collected from four portions of the epididymis (head, cranial corpus, caudal corpus, tail) were compared before and after ejaculation for viability, mitochondrial activity, kinetic parameters, and morphology. A significant increase in the mitochondrial activity along the epididymis was reported, suggesting a possible involvement in the motion mechanism. This should be corroborated by the significant correlation between mitochondrial activity and the total and progressive motility and the increase in velocities of spermatozoa recorded by computer-assisted sperm analysis. The percentage of most of the abnormal spermatozoa were similar in all tracts, with a great variability between jackasses. Only the bent midpiece percentage decreased significantly along epididymis. A significant increase in the percentage of distal cytoplasmic droplets (DCD), and a simultaneous decrease in the proximal cytoplasmic droplets (PCD), was found. The DCD fell down after ejaculation suggesting the late loss of the cytoplasmic residual (DCD) in the donkey, as hypothesized in the stallion. Because the prevalence of PCD were similar in both tail epididymal and ejaculated spermatozoa, a defect of the maturative process in the PCD sperm should be speculated.

The epididymis, cytoplasmic droplets and male fertility

The potential of spermatozoa to become motile during post-testicular maturation, and the relationship between the cytoplasmic droplet and fertilizing capacity are reviewed. Post-testicular maturation of spermatozoa involves the autonomous induction of motility, which can occur in vivo in testes with occluded excurrent ducts and in vitro in testicular explants, and artefactual changes in morphology that appear to occur in the testis in vitro. Both modifications may reflect time-dependent oxidation of disulphide bonds of head and tail proteins. Regulatory volume decrease (RVD), which counters sperm swelling at ejaculation, is discussed in relation to loss of cytoplasmic droplets and consequences for fertility. It is postulated that: (i) fertile males possess spermatozoa with sufficient osmolytes to drive RVD at ejaculation, permitting the droplet to round up and pinch off without membrane rupture; and (ii) infertile males possess spermatozoa with insufficient osmolytes so that RVD is inadequate, the droplet swells and the resulting flagellar angulation prevents droplet loss. Droplet retention at ejaculation is a harbinger of infertility caused by failure of the spermatozoon to negotiate the uterotubal junction or mucous and reach the egg. In this hypothesis, the epididymis regulates fertility indirectly by the extent of osmolyte provision to spermatozoa, which influences RVD and therefore droplet loss. Man is an exception, because ejaculated human spermatozoa retain their droplets. This may reflect their short midpiece, approximating head length, permitting a swollen droplet to extend along the entire midpiece; this not only obviates droplet migration and flagellar angulation but also hampers droplet loss.

Gene trap mutation of murine outer dense fiber protein-2 gene can result in sperm tail abnormalities in mice with high percentage chimaerism

BACKGROUND

Outer dense fiber protein 2, Odf2, is a major component of the outer dense fibers, ODF, in the flagellum of spermatozoa. ODF are associated with microtubule doublets that form the axoneme. We recently demonstrated that tyrosine phosphorylation of Odf2 is important for sperm motility. In the course of a study of Odf2 using Odf2 mouse knockout lines we observed that males of a high percentage chimaerism, made using XL169 embryonic stem cells, were infertile, whereas mice of low-medium percentage chimaerism were fertile.

RESULTS

XL169 ES cells have a beta-geo gene trap cassette inserted in the Odf2 gene. To determine possible underlying mechanisms resulting in infertility we analyzed epididymal sperm and observed that >50% displayed bent tails. We next performed ultrastructural analyses on testis of high percentage XL169 chimaeric mice. This analysis showed that high percentage XL169 chimaeric mice produce elongating spermatids that miss one or more entire outer dense fibers in their midpiece and principal piece. In addition, we observed elongating spermatids that show thinning of outer dense fibers. No other obvious abnormalities or defects are present in elongating spermatids. Spermatozoa from the caput and cauda epididymis of XL169 mice of high percentage chimaerism show additional tail defects, including absence of one or more axonemal microtubule doublets and bent tails. Sperm with bent tails display abnormal motility.

CONCLUSIONS

Our results document the possible impact of loss of one Odf2 allele on sperm tail structure and function, resulting in a novel sperm tail phenotype.

High Resolution Light Microscopic Evaluation of Boar Semen Quality Sperm Cytoplasmic Droplet Retention in Relationship with Boar Fertility Parameters

The purpose of this study was to investigate the relationship between fertility and quantitative measures of boar semen quality, including various patterns of sperm cytoplasmic droplet (CD) retention, as determined by high power differential interference contrast (DIC) microscopy. A total of 116 ejaculates were collected from a nucleus herd of 18 Large White boars over an eight month period. Semen quality parameters were analyzed for each ejaculate by calculating the percentage of normal spermatozoa, spermatozoa possessing a CD in the proximal, distal, or distal midpiece reflex position, total spermatozoa with an attached cytoplasmic droplet, spermatozoa with non-CD related aberrations and total spermatozoa with abnormalities. Of the 116 ejaculates received, 71 ejaculates from 13 boars had corresponding fertility data from single-sire inseminations of multiparous sows. The fertility data included farrowing rate (FR) and total number born (TNB). The monthly FR encompassed one month before and one month after the date of semen collection. Detection of differences for fertility and semen quality parameters was performed by separating the boars into either an above-average or below-average group based on the mean FR (74.01 +/- 1.43%) or TNB (12.34 +/- 0.17) for the study. For FR, the boars in the below-average group had a significantly lower percentage of normal spermatozoa and significantly higher percentage of spermatozoa possessing distal CDs, total attached CDs and total abnormalities compared to the boars in the above-average group. Conversely, for TNB there were no significant differences between the above- and below-average groups for the semen quality parameters. These data suggest that the attached CD may negatively affect FR, but not TNB. The detection of relationships between the boar fertility parameters and the retention of the sperm CD after ejaculation, document the advantage of high power DIC microscopy in conventional semen evaluation.

Study of apoptosis-related markers in ram spermatozoa

Certain features of capacitated or frozen-thawed spermatozoa have been considered to be an apoptosis-like phenomenon, and, it has been suggested that the presence of apoptotic sperm in seminal doses could be one of the reasons for poor fertility. The objective of this study was to determine whether phosphatidylserine (PS) translocation, caspase activity and DNA fragmentation, which are considered to be apoptotic markers in somatic cells, occur in ram sperm. Fresh ejaculates and sperm samples in different physiological state (cold-shocked, in vitro capacitated and acrosome-reacted (AR)) were compared. Simultaneous staining with 6-carboxifluorescein diacetate (6-CFDA) and Annexin V-Cy3.18 (AnnV) revealed four different sperm subpopulations in ejaculates. The main subpopulation was composed of viable cells without PS exposure (CFDA+/AnnV-). A total of 40.8% of sperm showed inverted PS, with two levels of alteration: CFDA+/AnnV+ in midpiece ("type I AnnV+"), and in acrosome and midpiece ("type II AnnV+"). The fewest subpopulation contained non-viable cells showing Annexin labelling in the entire cell (CFDA-/AnnV+). Labeling of caspases-3 and -7 by immunocytochemistry revealing different sperm subtypes depending on their localization in apical, equatorial, post-acrosomal regions and tail. The results obtained by western-blot showed, for the first time to our knowledge, that caspase-like proteins are present in fresh ram semen as both inactive and active forms. The proportion of sperm with fragmented DNA [terminal transferase-mediated dUDP nick end-labeling (TUNEL)-positive] were found rarely (2.7+/-0.5%) in all fresh ejaculates involved in this study. The analysis of total activity of both caspases by a fluorometric method showed a decrease in vitro capacitated and acrosome-reacted samples as well as in cryoinjured samples. However, the percentage of TUNEL-positive sperm demonstrating DNA fragmentation was significantly increased after in vitro induced capacitation and acrosome reaction, as well as after cold-shock although this augment was not significant. PS exposure is not totally dependent on caspases in ram spermatozoa as the addition of a caspase inhibitor prevented the increase in PS inversion due to incubation in capacitating conditions but not to the ionophore-induced acrosome reaction or cold-shock.

Sperm DNA fragmentation in a random sample of the Spanish boar livestock

A collection of 180 chilled boar semen samples, randomly chosen from stocks currently used for routine characterization of standard seminal quality, were studied for DNA fragmentation status using the sperm chromatin dispersion test and the DNA fragmentation index (DFI: percent of abnormal cell versus normal cells for DNA fragmentation) was determined. Values for sperm motility, acrosome status, coiled tails and abnormal head morphology, including presence and position of cytoplasmic droplets were also obtained. The DFI in the whole sample presented a wide range of variation with values oscillating between practically 0% and 47.95% and do not fit to a normal distribution. The most frequent classes (83.3%) presented a DFI lower than a 5%. Significant correlations between sperm DNA fragmentation and sperm motility, acrosome status, frequency of distal droplets, coiled tails and abnormal head morphology, were not observed. However, the presence of proximal cytoplasmic droplets showed a significant correlation with the level of DNA fragmentation observed in the ejaculated spermatozoa.

Infertility in a dog due to proximal cytoplasmic droplets in the ejaculate: investigation of the significance for sperm functionality in vitro

A 4-year-old Basque Shepherd male dog was presented for breeding soundness evaluation after the dog failed to impregnate the three bitches he had mated. Clinical examination showed no anomaly of the reproductive system. Semen evaluation showed normal sperm count (640 x 10(6)), 80% had progressively motile spermatozoa, and 96% had morphologically abnormal sperm of which 84% had proximal cytoplasmic droplet and 12% had proximal droplet plus other anomaly. A zona pellucida-binding assay, using canine oocytes derived from frozen-thawed ovaries, was performed in order to investigate the zona-binding ability of dog spermatozoa with proximal cytoplasmic droplets. For the zona pellucida-binding assay, ovaries were thawed and minced in phosphate-buffered saline + 0.4% bovine serum albumin, the oocytes recovered were divided into two groups of 35-40 oocytes to be, respectively, used with the infertile dog and with a control fertile dog. Spermatozoa were capacitated in Canine Capacitating Medium (CCM) at 38.5 degrees C and 5% CO(2) in air for 2 h before oocyte insemination. Groups of five to six oocytes placed in 45 microl droplets of CCM were incubated for 1 h. Afterwards, 5 microl of CCM containing 25,000 spermatozoa were added to each droplet and co-incubated for 2 h before fixation and evaluation of the complexes. After oocyte insemination, sperm motility and viability were evaluated: the sample from the infertile dog had 85% sperm motility with fast and linear progressive movement, and sperm viability of 92%. The sample from the control dog showed 40% sperm motility with fast and highly curvilinear and erratic movement, high degree of sperm agglutination and sperm viability of 32%. For the infertile dog the mean number of bound spermatozoa/oocyte was 0.33 whereas for the control dog it was 1.80. It was concluded that dog sperm with proximal cytoplasmic droplets seem to lack normal capacitating ability in vitro, and consequently, they may have reduced capacity to bind to the zona pellucida of canine oocytes.

Sperm Morphology in the Domestic Cat, and its Relation with Fertility: A Retrospective Study

Knowledge about normal ranges in semen quality and the association between sperm morphology and fertility in felids is limited. The aims of this retrospective study were to (1) define a normal spermiogram in cats; (2) evaluate possible effects of season, age and breed on sperm morphology; and (3) evaluate the relationship between sperm morphology and fertility. Semen samples collected by electroejaculation from 52 cats were evaluated for sperm morphology. The cats constituted two groups: a general population of cats (n = 48) and cats examined because of poor breeding records (n = 4). The general population was divided into household (n = 20), pedigree (n = 19) and colony cats (n = 9) and into three age classes, <12 months, 12-59 months and >or=60 months. The median percentage of normal spermatozoa in the general population was 44.0% (range 1.0-91.0%). Criteria were tentatively set for what was considered a normal spermiogram. The mean percentage of normal spermatozoa was higher during February to July than during August to January (p < 0.05). Pedigree cats had a lower mean percentage of normal spermatozoa than did household cats (p < 0.05). Age had no effect on the percentage of normal spermatozoa but was positively correlated with the percentage of proximal droplets. Of the cats with <40% normal spermatozoa (n = 19), all those with known breeding records (n = 11) had produced litters. The four cats examined because of poor breeding results had higher percentages of different sperm abnormalities than tentatively stipulated for the normal spermiogram. In two of these cats both sperm morphology and fertility changed over time.