Characterization of the semen quality of postpuberal boars with spontaneous unilateral abdominal cryptorchidism on the right side

Testicular heat stress, a historical perspective and two postulates for why male germ cells are heat sensitive

Herein, we compare the different experimental regimes used to induce testicular heat stress and summarise their impact on sperm production and male fertility. Irrespective of the protocol used, scrotal heat stress causes loss of sperm production. This is first seen 1-2 weeks post heat stress, peaking 4-5 weeks thereafter. The higher the temperature, or the longer the duration of heat, the more pronounced germ cell loss becomes, within extreme cases this leads to azoospermia. The second, and often underappreciated impact of testicular hyperthermia is the production of poor-quality spermatozoa. Typically, those cells that survive hyperthermia develop into morphologically abnormal and poorly motile spermatozoa. While both apoptotic and non-apoptotic pathways are known to contribute to hyperthermic germ cell loss, the mechanisms leading to formation of poor-quality sperm remain unclear. Mechanistically, it is unlikely that testicular hyperthermia affects messenger RNA (mRNA) abundance, as a comparison of four different mammalian studies shows no consistent single gene changes. Using available evidence, we propose two novel models to explain how testicular hyperthermia impairs sperm formation. Our first model suggests aberrant alternative splicing, while the second model proposes a loss of RNA repression. Importantly, neither model requires consistent changes in RNA species.

Proteomic profiles of unilateral cryptorchidism in pigs at different ages using MALDI-TOF mass spectrometry and in-gel digestion coupled with mass spectrometry (GeLC-MS/MS) approaches

Background

Cryptorchidism is a condition that occurs when one or both testes fail to descend into the scrotum. It is a common congenital disorder, causing economic loss in pig production. However, there have been only limited studies of differential protein expression profiles in undescended testes (UDTs) in the abdomen and descended testes (DTs) in cryptorchid pigs, especially at the peptidome and proteome levels. The present study aimed to analyze the peptidome of UDTs and DTs in unilateral cryptorchid pigs aged 1–2, 6, 15 and 20 weeks and in normal testes of healthy pigs aged 1–2 and 12 weeks, using peptide mass fingerprinting and three-dimensional principal component analysis (3D-PCA) with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and to identify potential protein candidates, using in-gel digestion coupled with mass spectrometry (GeLC-MS/MS). Western blot analysis was used to verify protein expression. Protein sequence was affirmed by liquid chromatography–tandem mass spectrometry.

Results

A PCA plot showed a discrete cluster for each sample group. Peptide mass fingerprints (PMFs) demonstrated unique peptide fragments in UDTs at different ages. A number of markedly expressed proteins from GeLC-MS/MS were identified, including the multifunctional tumor necrosis factor receptor superfamily member 18 (TNFRSF18), in DTs at 1–2 and 6 weeks and in UDTs at 15 and 20 weeks of age. Using western blot analysis, high expression of TNFRSF18 was observed in the UDTs at 15 weeks. Using the STITCH database, this protein was found to be related to apoptosis, corresponding to the previous report in the UDTs at the same age.

Conclusions

The present study revealed the specific PMFs and clusters for porcine cryptorchidism, and a novel protein, TNFRSF18, associated with the disease mechanism. These results could provide further insights into the pathogenesis of the disease.

Alteration of androgen receptor expression, apoptosis and cell proliferation in cryptorchid suckling, nursery and growing-finishing pigs

Cryptorchidism, a condition of one or two undescended testicles, is a common congenital disease in pigs, causing loss in the pig industry. One of the major factors affecting testicular descent is the androgen receptor (AR), which binds to androgen and then regulates the expression of androgen-responsive genes in the inguinoscrotal phase of testicular descent. AR expression has been reported to regulate apoptosis in testicular stem cells. The present study aimed to immunohistochemically examine AR and Ki-67 protein expression and apoptosis detection in unilateral undescended testicles (UDT) and descended testicles in cryptorchid pigs (DT) of suckling (aged 1-2 weeks), nursery (aged 6 weeks) and growing-finishing pigs (aged 12, 15 and 20 weeks) and in normal testicles (NT) at 1-2 and 12 weeks of age. At 1-2 weeks, decreased expression of AR was observed in UDT and DT compared with NT and was lower than that at 6-20 weeks. The expression of Ki-67, a marker of cell proliferation, in UDT and DT at 12 weeks was lower than that in NT at the same age. In addition, Ki-67 expression in UDT at 6 and 12 weeks was lower than that in UDT at 1-2 and 15-20 weeks. More testicular apoptosis was revealed in UDT at 1-2 weeks than in DT and NT at the same age. At 15-20 weeks, more apoptosis was detected in UDT than in DT. Positive correlation of AR expression in DT at 6 and 12 weeks was also noted, in addition to the association of the expression of AR and Ki-67 in NT at 12 weeks. Taken together, this study unveiled the low expression of AR and high apoptosis detection in UDT, whereas low expression of AR and low apoptosis detection were noted in DT in suckling piglets. Diminished cell proliferation was shown in UDT at 6-12 weeks, whereas high apoptosis was observed in UDT at 15-20 weeks. High expression of AR was shown only in nursery pigs. Distinct expression of AR in DT and NT at 1-2 and 12 weeks indicated that both conditions were not interchangeable.

Effect of Single Layer Centrifugation Porcicoll (70%, 80% and 90%) or supplementation with reduced glutathione, seminal plasma and bovine serum albumin on frozen-thawed boar sperm

Selecting the optimal sperm population is essential for success with reproductive techniques. Porcicoll (formerly Androcoll-P) is a colloid formulation for selection of high-quality boar spermatozoa by single layer centrifugation (SLC). To date, most studies have been carried out with fresh semen and large volumes. We carried out 2 experiments to test the use of Porcicoll for thawed boar semen in small volumes. In Experiment 1, cryopreserved semen doses were thawed, split in 200-μL aliquots and layered on 1mL of Porcicoll 70%, 80% or 90%, or buffer without colloid. We assessed sperm recovery (the proportion of the loading dose that appeared in the pellet, %), and the physiology of the selected spermatozoa (flow cytometry: Viability, apoptotic changes, capacitation, mitochondrial activity, intracellular reactive oxygen species). The most suitable proportion was Porcicoll 80%, allowing acceptable sperm recovery (16.9±4.2%, compared to 70% (35.4%±3.0, p<0.001) and 90% (8.2%±3.0, P=0.001), and improved quality (mitochondrial activity: Porcicoll 80%: 77.7±1% vs Control: 60.3±0.7%, P<0.05). In Experiment 2, we compared 3 supplements to Porcicoll 80%: 500mM reduced glutathione (GSH), 20% seminal plasma (SP) and 0.5% bovine serum albumin (BSA). Supplementation with GSH or BSA did not cause relevant changes relative to Control. In contrast, SP induced membrane and acrosomal changes resembling capacitation, which might preclude its use in some applications, and decreased recovery (5.5%±1.9 vs. 24.3%±1.2 Control; P<0.001). However, it could be useful prior to other applications such as in vitro fertilisation. Overall, Porcicoll is an effective colloid for isolating a high-quality population from thawed boar sperm, 80% being a balanced option for good recovery and high quality. Supplements could be useful depending on the proposed use of the spermatozoa.

Boar management and semen handling factors affect the quality of boar extended semen

Artificial insemination (AI) is the preferred method for reproduction in the majority of the intensive pig production systems Worldwide. To this end, fresh extended ready-to-use semen doses are either purchased from AI-centres or produced by boars kept on-farm. For profitable semen production, it is necessary to obtain a maximum amount of high quality semen from each boar. This paper reviews current knowledge on factors that may affect semen quality by influencing the boar or the semen during processing. Genetic markers could be used for early detection of boars with the highest fertility potential. Genetic selection for fast growth might jeopardize semen quality. Early detection of boars no longer fit for semen production might be possible by ultrasonography of the testes. Seasonal variation in sperm quality could be associated with changes in photoperiod and heat stress during summer. Comfortable housing, with appropiate bedding material to avoid locomotion problems is essential. In some areas, cooling systems may be necessary to avoid heat stress. The sperm quality can be manipulated by feeding strategies aiming, for instance, to increase sperm resistance to oxidative stress and extend storage duration. High collection frequency will negatively influence sperm quality. Also, if collection is not hygienically performed it will result in bacterial contamination of the semen doses. The concern over bacterial contamination has risen not only because of its negative effect on semen quality but also due to the detection of antimicrobial resistance in isolates from extended semen. Moreover, bacterial and viral pathogens must be monitored because they affect semen production and quality and constitute a risk of herd infection. During processing, boar sperm are submitted to many stress factors that can cause oxidative stress and capacitation-like changes potentially reducing their fertility potential. Dilution rate or dilution temperature affects the quality of the semen doses. Some packaging might preserve semen better than others and some plastic components might be toxic for sperm. Standard operation procedures and quality assurance systems in AI centres are needed.

Unilateral cryptorchidism induces morphological changes of testes and hyperplasia of Sertoli cells in a dog

Cryptorchidism is one of the most common genital defects in dogs. This study investigated the effects of abdominal cryptorchidism on morphology, cell proliferation, and Sertoli cell condition in a dog with spontaneous unilateral cryptorchidism. Elective orchidectomy was performed on the abdominal right testis and the scrotal left testis. Significant reductions in numbers of spermatogonia, spermatocytes, and spermatids were observed in hematoxylin and eosin stained sections of the cryptorchid testis. The size of the epididymal duct was smaller than that of the control testis. Based on Ki67 immunohistochemistry, the proliferative activity of spermatogonia and spermatocytes was significantly decreased in the cryptorchid testis. However, proliferative activity was increased in the epididymal duct. Based on GATA-4 immunohistochemistry, Sertoli cells were relatively resistant to cryptorchidism, and the proliferative activity of Sertoli cells was markedly increased in the cryptorchid testis than in the control testis. These results suggest that spontaneous unilateral cryptorchidism causes morphological defects in spermatogonia and spermatocytes in the testis and changes the size of the efferent ductule of the epididymis. In addition, spontaneous unilateral cryptorchidism increases proliferative activity of Sertoli cells, which may be a predisposing factor for Sertoli cell cancer in cryptorchid testes.

Testosterone secretion and semen plasma enzyme activity in rams with genital pathology stimulated with GnRH

Testosterone secretion in response to GnRH stimulation and enzymatic activity of semen plasma was evaluated comparatively in rams with or without genital abnormality. Scrota, testes and epididymides of 128 rams between 1.5 and 6 years old from various breeds were examined clinically and ultrasonographically. Bilaterally cryptorchid rams (n = 2), and rams with focal testicular degeneration (n = 3) or unilateral sperm granuloma localized in the caput (n = 3) epididymis or the cauda epididymis (n = 3), diagnosed by either clinical or ultrasonographic examination, were selected for the further investigation of spermatologic parameters, testosterone secretion in response to GnRH stimulation, and enzymatic activity of semen plasma before histopathologic confirmation of lesions. Except for the cryptorchid rams, sperm parameters determined in ejaculates were similar to intact controls (n = 3). GnRH administration increased plasma testosterone levels significantly irrespective of the type of genital pathology (P < 0.01). The testosterone response calculated based on area under the curve following GnRH administration in rams having genital abnormality was not significantly different from the controls. Aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) activity in the semen plasma varied between rams, with the lowest mean values in the bilaterally cryptorchid group (P < 0.05). Spermatic granuloma localized either in the caput or cauda of the epididymis was associated with a significant reduction in the semen plasma AST activity compared to controls (P < 0.01). In conclusion, our results indicated that the ability of testicular tissue to secrete testosterone in response to GnRH stimulation in rams with bilateral cryptorchidism, focal testicular degeneration and unilateral sperm granuloma was similar to that of intact controls, and that reduced semen plasma AST activity may have a diagnostic value in the diagnosis of the epididymal obstruction in rams. Focal testicular degeneration did not influence AST, alkaline phosphatase (ALP) and LDH activity in semen plasma.

Morphological and histochemical characteristics of the lamina propria in scrotal and abdominal testes from postpubertal boars: correlation with the appearance of the seminiferous epithelium

This study was undertaken to investigate the morphological characteristics and lectin affinity of the testicular lamina propria in healthy boars and in unilateral and bilateral abdominal cryptorchid boars. The lamina propria of scrotal testes from healthy boars and unilateral cryptorchid boars was constituted by an innermost noncellular layer, the basal lamina, and by 2 layers of peritubular cells, each separated by a fibrous layer. The noncellular layers contained collagen fibres and glycoconjugates with abundant N-acetylgalactosamine, galactose, fucose, N-acetylglucosamine and neuraminic acid residues. The inner peritubular cell layer was composed of myoid cells, the outer layer of fibroblasts. In the abdominal testes of unilateral and bilateral cryptorchid boars, the lamina propria of nondegenerating and degenerating seminiferous tubules appeared thickened due to an increased content of collagen fibres and glycoconjugates. Glycoconjugates showed decreased amounts of fucose, neuraminic acid and galactose, and increased amounts of N-acetylglucosamine residues. The basal lamina formed infoldings toward the seminiferous epithelium and contained small cells. Both inner and outer peritubular cells were fibroblasts of immature appearance. In degenerated seminiferous tubules of bilateral cryptorchid boars, the lamina propria was composed of a thickened and collagenised basal lamina, without peritubular cells and with a low content of glycoconjugates. In scrotal testes, therefore, the lamina propria was implicated in tubular contractility and in mediating the communication and the substrate diffusion between seminiferous tubules and interstitial tissue. Cryptorchidism induced morphological and histochemical alterations in the lamina propria of abdominal testes, which may be linked to evidence from other studies of lack of tubular contractility and defective cell-cell communication and substrate diffusion. The severity of these anomalies correlated with the severity of Sertoli cell alterations.

Lectin affinity of the seminiferous epithelium in healthy and cryptorchid post-pubertal boars

The present study describes the sugar content of the seminiferous epithelium, using lectin histochemistry, in healthy boars and in boars with unilateral and bilateral abdominal cryptorchidism. In healthy boars the apical cytoplasm of Sertoli cells exhibited abundant glucosyl (Con A and WGA lectins), galactosyl (HPA, DBA, SBA and PNA lectins), and fucosyl (AAA lectin) residues. Spermatogonia and spermatocytes contained abundant glucosyl (Con A and WGA lectins) and fucosyl (AAA lectin) residues. In spermatids, galactosyl (SBA and PNA lectins) and glucosyl (Con A and WGA lectins) residues increased progressively throughout spermiogenesis, and fucosyl (AAA lectin) residues decreased. As compared with healthy boars, the scrotal testis of unilateral cryptorchid boars showed decreased amounts of fucosyl (AAA lectin) and galactosyl (HPA and DBA lectins) residues on the Sertoli cell apical cytoplasm; spermatocytes exhibited higher content of glucosyl (Con A lectin) residues and spermatids showed altered nature of glucosyl (Con A and WGA lectins) and galactosyl (SBA and PNA lectins) complexes. In abdominal testes of unilateral and bilateral cryptorchid boars, immature Sertoli cells and spermatogonia showed decreased fucosyl (AAA lectin), and increased glucosyl (Con A and WGA lectins) and galactosyl (SBA and PNA lectins) contents. These results suggest that the seminiferous epithelium of healthy boars has polarized activity with the apical compartment implicated in germ cell-Sertoli cell adhesion and interaction, in transport of ions, substrates and fluids, and in acrosomal differentiation. In scrotal testes, unilateral abdominal cryptorchidism could lead to defective germ cell-Sertoli cell adhesion, impaired acrosomal differentiation and increased ionic transport in the apical compartment of the seminiferous epithelium. Unilateral and bilateral cryptorchidism could induce increased ionic transport and membrane permeability in the seminiferous epithelium of abdominal testes.

Cytology of the interstitial tissue in scrotal and abdominal testes of post-puberal boars

The interstitial tissue of the testes from healthy boars, and unilateral and bilateral abdominal cryptorchid boars was examined by light and transmission electron microscopy. The left and right testes of healthy boars, and the left (scrotal) testis of unilateral cryptorchid boars had abundant mature Leydig cells, few fibroblasts and mast cells, scarce and small blood vessels, and little lymphatic areas. The right (abdominal) testis of unilateral cryptorchid boars contained abundant Leydig cells, fibroblasts and erythrocytes, scarce mast cells, and frequent blood vessels; Leydig cells exhibited either a mature but degenerative appearance or an immature appearance, and fibroblasts displayed immaturity signs. The interstitial tissue of the left (abdominal) testes of bilateral cryptorchid boars had small blood vessels surrounded by erythrocytes, lymphocytes, and few plasma cells, and abundant mature and immature Leydig cells, immature fibroblasts, and mast cells. Mature Leydig cells showed mid or advanced degeneration, and immature Leydig cells displayed either non-degenerative or degenerative patterns. The right (abdominal) testes of bilateral cryptorchid boars contained scarce immature Leydig cells in advanced degeneration, large fibrous and adipose areas, and blood vessels. These results indicated that unilateral abdominal cryptorchidism affect neither the structural nor the cytologic features of the interstitial tissue in scrotal testes. Unilateral and bilateral cryptorchidism induced abnormal differentiation of Leydig cells and fibroblasts leading to decreased steroid production and increased collagenization in abdominal testes.