The Parkes Lecture. Heat and the testis

Polymorphism in IGFALS gene and its association with scrotal circumference in Hu lambs

Scrotal circumference is an important reproductive index of breeding rams, which has a high genetic correlation with ejaculation volume and semen quality. In this study, the scrotal circumference of 1353 male Hu sheep at different stages of development was measured and descriptive statistical analysis was performed. The results showed that the coefficient of variation of scrotal circumference at each stage was greater than 10%, and its heritability were moderately to high, ranging from 0.318 to 0.719. We used PCR amplification and Sanger sequencing to scan the polymorphisms of the IGFALS gene, and performed association analysis with the circumference of the scrotum at different stages. We identified a synonymous mutation g.918 G > C in exon 1 of the IGFALS gene, and this mutation was significantly associated with scrotal circumference at 100, 120, 140, 160 and 180 days (p < 0.05). Therefore, IGFALS gene polymorphism can be used as a molecular marker affecting scrotal circumference of Hu sheep, which can provide a reference for future molecular marker-assisted selection of scrotal circumference in sheep.

Synergistic protective effects of 3,4-dihydroxyphenylglycol and hydroxytyrosol in male rats against induced heat stress-induced reproduction damage

Testicular heat stress disrupts spermiogenesis and damages testicular tissue. The study aims to assess 3,4-dihydroxyphenylglycol (DHPG) and hydroxytyrosol (HT) from olive oil as antioxidants to reduce heat-induced testicular damage. Seven groups of 35 male rats were used. Group I got normal saline. Group 2 had HS (43 °C for 20 min/day) and normal saline for 60 days. Groups 3-7 had HS and DHPG/HT doses (0.5 mg/kg DHPG, 1 mg/kg DHPG, 5 mg/kg HT, 0.5 mg/kg DHPG + 5 mg/kg HT, and 1 mg/kg DHPG + 5 mg/kg HT). The evaluation included tests on testicular tissue, sperm quality, oxidative status, gene activity, and fertility after 60 days. After DHPG and HT treatment, sperm motility, viability, and plasma membrane functionality, as well as levels of total antioxidant capacity (TAC), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT), and Bcl-2 gene expression, and in vivo fertility indexes increased. Meanwhile, abnormal morphology and DNA damage decreased, along with levels of glutathione (GSH), nitric oxide (NO), and malondialdehyde (MDA), and Bax, caspase-3, and caspase-9 gene expression, compared to the HS group. The study found that DHPG and HT have a more substantial synergistic effect when used together, improving reproductive health.

Effect of quercetin and mirtazapine on spermatogenesis and testis structure in phenylhydrazine-induced hemolytic anemia mice: An experimental study

Anemia poses a significant healthcare challenge across different socioeconomic groups and can result in reproductive system damage through the generation of free radicals and lipid peroxidation. This study examines the protective effects of quercetin (QUE) and mirtazapine (MIR) against the reproductive damage caused by phenylhydrazine (PHZ) in mice. Fifty NMRI mice, aged 8-10 weeks with an average weight of 27.0 ± 2.0 g, were randomly divided into five groups. The control group (Group 1) received oral administration of 10 mL/kg/day of normal saline. Group 2 (PHZ group) received an initial intraperitoneal dose of 8 mg/100 g body weight of PHZ, followed by subsequent doses of 6 mg/100 g every 48 h. Group 3 received PHZ along with oral QUE at a dosage of 50 mg/kg/day. Group 4 received PHZ along with oral MIR at a dosage of 30 mg/kg/day. Group 5 received PHZ along with oral QUE at a dosage of 50 mg/kg/day and MIR at a dosage of 30 mg/kg/day. The treatment duration was 35 days. Sperm samples were collected from the caudal region of the epididymis post-euthanasia to assess the total mean sperm count, sperm viability, motility, DNA damage, and morphology. Testicular tissue was employed to quantify total antioxidant capacity (TAC), superoxide dismutase (SOD), glutathione peroxidase (GPx), and malondialdehyde (MDA) concentrations, while serum levels of testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were analyzed. Additionally, various aspects, including testicular histopathology, oxidative enzyme levels, gene expression related to apoptosis and antiapoptotic pathways, and in vivo fertility index, were evaluated after 35 days. The QUE, MIR, and QUE + MIR groups showed less abnormal morphology and DNA damage, as well as better total and progressive sperm motility, motility characteristics, viability, and plasma membrane function compared to the PHZ group. QUE, MIR, and QUE + MIR administration increased TAC, SOD, and GPx activities in testicular tissue, while reducing MDA levels compared to the PHZ group. Furthermore, QUE, MIR, and QUE + MIR significantly reduced Bax, and caspase-3 expression levels, and increased Bcl-2 expression levels, compared to the PHZ group. Mice treated with QUE, MIR, and QUE + MIR exhibited an increased in vivo fertility index and plasma sex hormone levels compared to the PHZ group. These results show that QUE, MIR, and QUE + MIR might be able to improve the fertility index, boost the testicular antioxidant defense system, and control the death of germ cells. This could mean that they could be used to treat mice with PHZ-induced testicular damage.

Comparative expression and localization of visfatin, chemerin, and chemerin receptor proteins in a heat-stressed mouse testis

The adipokines, visfatin, chemerin, and its receptor are expressed in the testis. It has also been shown that heat-stress alters the secretion and expression of other adipokines. Testicular heat-stress is now well known to cause the impairment in the testis. It has also been documented that heat-stress changes the expression of genes and proteins in the testis. To the best of our knowledge, the expression and localization of visfatin chemerin and its receptor have not been investigated in the heat-stressed testis. Therefore, the present study has investigated the expression and localization of these proteins in the heat-stressed testis. The expression of visfatin and chemerin and receptor exhibits a differential repossess against the heat stress. Visfatin expression was up-regulated while chemerin and chemerin receptor was down-regulated in the heat-stressed testis as shown by western blot analysis. The immunolocalization of visfatin and chemerin showed increased abundance in the seminiferous tubules of heat-stressed mice testis. Furthermore, abundance of visfatin, chemerin, and its receptor showed a decrease in abundance in the Leydig cells of heat-stressed testis. The decreased abundance of these proteins in the Leydig cells coincides with decreased 3β-HSD immunostaining along with decreased testosterone levels. These results suggest that heat-stress might decrease testosterone secretion by modulating visfatin and chemerin in the Leydig cells. The increased abundance of visfatin and chemerin in the primary spermatocytes, round spermatid, and multinucleated germ cells also coincides with increased immunostaining of active caspase-3. Moreover, expression of Bcl-2 was down-regulated, and expression of active caspase-3 and HSP70 were up-regulated along with increased oxidative stress in the heat-stressed testis, suggesting stimulated apoptosis. In conclusion, our results showed that visfatin, chemerin, and its receptor are differentially expressed in the testis under heat-stress and within the testis also it might differentially regulate testosterone biosynthesis in the Leydig cells and apoptosis in the seminiferous tubules.

Ameliorative effects of omega-3 and omega-6 on spermatogenesis, testicular antioxidant status and in vivo fertility index in heat-stressed rats

The current study aimed to investigate the use of omega-6 (ω6) or omega-3 (ω3) in reducing heat-induced damage to the testicles. This is due to the known detrimental effects of heat and the potential protective properties of ω6 and ω3. In the study, 48 male rats were divided into eight groups, each containing 6 rats. Group I (control) received normal saline. Group 2 was exposed to high temperatures (43 °C for 20 min/day) and also received normal saline for 60 days. Groups 3-7 underwent identical HS conditions and received varying doses of ω6 or ω3 (0.5 mg/kg DHPG, 1 mg/kg DHPG, 5 mg/kg HT, 0.5 mg/kg DHPG + 5 mg/kg HT, and 1 mg/kg DHPG + 5 mg/kg HT), respectively. After 60 days, various tests were conducted on the testicular tissue, sperm quality, oxidative status, gene activity, and in vivo fertility indexes to evaluate the effects of the treatments. Treatment with ω6 and ω3 could reduce abnormal morphology and DNA damage while increasing total and progressive motility, characteristics motility, viability, and plasma membrane functional impairment compared with HS-exposed groups. Antioxidant status levels in testicular tissue were improved after administration of ω6 and ω3. Furthermore, after receiving ω6 and ω3, there were significantly lower expression levels of P53 and Caspase-3 and significantly higher expression levels of Bcl-2 compared to the HS-exposed group. Furthermore, the results showed that administration of ω6 and ω3 to rats exposed to HS could increase their in vivo fertility indexes compared to the group not exposed to HS. According to our data, all doses of ω6 and ω3 (particularly doses of ω6-1.25 and ω3-300) can improve the testicular damage, testicular antioxidant defense mechanism, regulate germ cell apoptosis, and increase in vivo fertility indexes.

Use of thermography in the long-term evaluation of scrotal surface temperature and its impact on seminal quality in stallions

Scrotal surface thermography is a non-invasive method for assessing testicular thermoregulation in stallions; however, few studies have explored the application of this technique concerning the thermal physiology of equine reproductive systems. This study aimed to evaluate the consistency of testicular thermoregulation in stallions over a year using thermography to measure the scrotal surface temperature (SST). Moreover, we assessed the best region for measuring the surface body temperature compared with the SST. Ten light-breed stallions were used in the experiment. Thermographic images of the scrotal and body surfaces (neck and abdomen) were captured. Fresh, cooled and frozen-thawed semen samples were evaluated to verify the impact of thermoregulation on semen quality. Testicular thermoregulation was maintained throughout the year in stallions amidst changes in the external temperature, as evidenced by the weak correlation between the SST and ambient temperature. A lower correlation was observed between the environmental temperature and body surface temperature (BTS) obtained from the abdomen (BTS-A; R = .4772; p < .0001) than with that obtained from the neck (BTS-N; R = .7259; p < .0001). Moreover, both BTS-A and SST were simultaneously captured in a single image. The consistent quality of the fresh, cooled and frozen semen suggests efficient thermoregulation in stallions throughout the year.

Testicular expression of heat SHOCK proteins 60, 70, and 90 in cryptorchid horses

Heat shock proteins are the most evolutionarily conserved protein families induced by stressors including hyperthermia. In the context of pathologies of the male reproductive tract, cryptorchidism is the most common genital defect that compromises the reproductive potential of the male because it induces an increase in intratesticular temperature. In equine species, cryptorchidism affects almost 9 % of newborns and few studies have been carried out on the molecular aspects of the retained testis. In this study, the expression pattern of HSP60, 70, and 90 in abdominal and inguinal testes, in their contralateral descended normally testes, and in testes of normal horses were investigated by Western blot and immunohistochemistry. The histomorphological investigation of retained and scrotal testes was also investigated. The seminiferous epithelium of the retained testes showed a vacuolized appearance and displayed a completely blocked spermatogenesis for lacking meiotic and spermiogenetic cells. On the contrary, the contralateral scrotal testes did not show morphological damage and the seminiferous epithelium displayed all phases of the spermatogenetic cycle as in the normal testes. The morphology of Leydig cells was not affected by the cryptorchid state. Western blot and immunohistochemistry evidenced that equine testis (both scrotal and retained) expresses the three investigated HSPs. More in detail, the Western blot evidenced that HSP70 is the more expressed chaperone and that together with HSP90 it is highly expressed in the retained gonad (P < 0.05). The immunohistochemistry revealed the presence of the three HSPs in the spermatogonia of normal and cryptorchid testes. Spermatogonia of retained testes showed the lowest expression of HSP60 and the highest expression of HSP90. Spermatocytes, spermatids of scrotal testes, and the Sertoli cells of retained and scrotal testes did not display HSP60 whereas expressed HSP70 and HSP90. These two proteins were also localized in the nucleus of the premeiotic cells. The Leydig cells displayed the three HSPs with the higher immunostaining of HSP70 and 90 in the cryptorchid testes. The results indicate that the heat stress condition occurring in the cryptorchid testis influences the expression of HSPs.

Characterization and enrichment of spermatogonial stem cells of common carp (Cyprinus carpio)

Spermatogenesis is a systematically organized process that ensures uninterrupted sperm production in which the spermatogonial stem cells (SSCs) play a crucial role. However, the existing absence of teleost-specific molecular markers for SSCs presents a notable challenge. Herein we characterized phenotypically the spermatogonial stem cells using specific molecular markers and transmission electron microscopy. Moreover, we also describe a simple method to suppress common carp spermatogenesis using the combination of Busulfan and thermo-chemical treatment, and finally, we isolate and enrich the undifferentiated spermatogonial fraction. Our results showed that C-kit, GFRα1, and POU2 proteins were expressed by germ cells, meanwhile, undifferentiated spermatogonial populations preferentially expressed GFRα1 and POU2. Moreover, the combination of high temperature (35 °C) and Busulfan (40 mg/kg/BW) effectively suppressed the spermatogenesis of common carp males. Additionally, the amh expression analysis showed differences between the control (26 °C) when compared to 35 °C with a single or two Busulfan doses, confirming that the testes were depleted by the association of Busulfan at high temperatures. In an attempt to isolate the undifferentiated spermatogonial fraction, we used the Percoll discontinuous density gradient. Thus, we successfully dissociated the carp whole testes in different cellular fractions; subsequently, we isolated and enriched the undifferentiated spermatogonial population. Therefore, our results suggest that probably both GFRα-1 and POU2 are highly conserved factors expressed in common carp germinative epithelium and that these molecules were well conserved along the evolutionary process. Furthermore, the enriched undifferentiated spermatogonial population developed here can be used in further germ cell transplantation experiments to preserve and propagate valued and endangered fish species.

The protective impact of curcumin, vitamin D and E along with manganese oxide and Iron (III) oxide nanoparticles in rats with scrotal hyperthermia: Role of apoptotic genes, miRNA and circRNA

BACKGROUND

Infertility is one of the major factors affecting most people around the world. Short-term exposure to high temperatures can cause hyperthermia, which is one of the causes of male infertility. The aim of this study was to investigate the protective effect of curcumin, vitamins D and E along with Iron (III) oxide nanoparticles (Fe2O3-NPs) and manganese oxide nanoparticles (MnO2-NPs) on semen parameters and its effect on miRNA21 and circRNA0001518 expression.

MATERIAL AND METHODS

In this study, the lower part of the rat was exposed to 43 °C for 5 weeks every other day for 5 weeks. Then the animals were killed. Tissue samples were collected for sperm parameters analysis, and tissue samples were taken for evaluation of apoptosis levels in germ cells, and RNA extraction in order to examine the expression of Bax, Bcl-2, miRNA, and CircRNA genes.

RESULTS

The results of this study showed that administration of curcumin, vitamin D, and vitamin E with Fe2O3-NPs and MnO2-NPs can improve the parameters of semen, Bax gene expression, Bcl-2 as well as miRNA and CircRNA in rats with testicular hyperthermia. In addition, curcumin by reducing the toxicity of Fe2O3 nanoparticles was able to reduce its negative effects and also reduce apoptosis in germ cells. This decrease in apoptosis was attributed to decreased Bcl-2 gene expression and increased expression of Bax, miRNA-21, and circRNA0001518.

CONCLUSION

All the results of this study confirmed that Fe2O3-NPs and Mno2-NPs containing antioxidants or vitamins are useful in improving fertility in rats due to scrotal hyperthermia. Although Fe2O3-NPs and Mno2-NPs containing both antioxidants and vitamins had a greater effect on improving fertility and reducing the toxic effects of nanoparticles.

The role of the intrinsic pathway of apoptosis in human ejaculated sperm damage under a state of scrotal heat stress

PURPOSE

The study aimed to determine the associations among standard sperm characteristics and oxidative/apoptotic markers in ejaculated sperm of men exposed to prolonged scrotal hyperthermia of either environmental or clinical origin.

METHODS

The original study design included four research groups: professional drivers (n = 54), infertile men with varicocele (n = 78), infertile men not exposed to prolonged genital heat stress (n = 37), and fertile individuals serving as the control group (n = 29). Standard semen analysis was performed according to the 5th WHO laboratory manual. The following oxidative and apoptotic parameters of sperm were investigated: mitochondrial superoxide anion generation (MitoSOX Red dye), phosphatidylserine externalization (Annexin V binding assay), mitochondrial membrane potential (JC-1 dye), DNA fragmentation (TUNEL/PI assay), and membrane fluidity (merocyanine 540 dye).

RESULTS

All the studied groups presented a strong deterioration in routine sperm parameters and a strongly apoptotic phenotype in sperm, characterized by both decreased mitochondrial membrane potential and enhanced DNA fragmentation, regardless of the thermal insult. Significant induction of mitochondrial superoxide anion generation was noted only in the groups exposed to genital heat stress. A positive correlation between the production of superoxide anion in the mitochondrial chain and the level of DNA fragmentation in drivers was also noted.

CONCLUSION

Long-term exposure to scrotal hyperthermia in real-life situations is sufficient to reduce sperm quality in humans. The thermal stress directly induces the oxidative stress cascade in ejaculated sperm, affecting the plasma membrane fluidity, mitochondrial homeostasis, and sperm DNA integrity.

Seasonal heat stress compromises testicular thermoregulation and semen quality of Dorper rams raised in a desert climate

Dorper rams are widely distributed throughout the world under different climatic conditions, however, little is known about their reproductive performance in desert regions. Ten Dorper rams were individually housed and exposed to thermoneutrality for 35 d in spring (23.6 ± 5.6 °C, mean ± SD) and outdoor heat stress (HS) for 35 d in summer (33.6 ± 2.0 °C) to evaluate the effect of seasonal HS on physiological responses, testicular biometry, and seminal quality under desert climatic conditions. Rectal temperature, respiration rate and coat surface temperatures in different body regions were measured every 7 d (0600, 1200, and 1800 h); also, testicular biometry was registered at 0600 h. Semen was collected via an artificial vagina 3 d after physiological variables were measured and seminal traits were evaluated. Rectal temperature, respiration rate and coat surface temperatures were higher (P < 0.01) at each hour of measurement in summer compared to spring. Overall, scrotal length and circumference, as well as testicular volume were higher (P < 0.01) in summer than in spring. Compared to spring conditions, summer HS caused lower (P ≤ 0.05) sperm concentration and viability combined with a higher percentage of sperm abnormalities without affecting ejaculate volume. Both mass and sperm motility were similar between seasons in the first two sampling weeks, and then decreased (P ≤ 0.03) due to summer HS. In conclusion, Dorper rams developed testicle hyperthermia and, consequently, showed poor semen quality due to the high environmental temperatures prevailing in desert regions.

Stress Factors and Their Effects on Productivity in Sheep

Products obtained from sheep have an economically important place in the world. Their adaptability to different climatic conditions, their ease of care and feeding, their high utilization of poor pasture areas with low yield and quality, the ease of flock management, their high twinning rate, and their short intergenerational period are some of the advantages of sheep production. Sheep production has the ability to adapt better to environmental stress factors, as can be understood from the presence of sheep in different geographical regions at a global level. However, the changes in environmental conditions and production cause some negative results in animals. All these negative results expose animals to various stress factors (heat, cold, transport, treatment, nutritional, shearing, weaning, etc.). All stress factors that directly and indirectly affect sheep production ultimately lead to compromised performance, decreased productivity, increased mortality, and adverse effects on the immune system. In order to cope with the current stress parameters in animals and to achieve optimum production, a holistic approach is needed according to the environmental conditions and available resources. It is important to consider the factors involved in these responses in order to manage these processes correctly and to develop adequate strategies and improve sheep welfare. This review aimed to reveal the importance of some stress factors in sheep and their effects on sheep productivity.

Chronic exposure to warm temperature causes low sperm abundance and quality in Drosophila melanogaster

Temperature influences male fertility across organisms; however, how suboptimal temperatures affect adult spermatogenesis remains understudied. In a recent study on Drosophila melanogaster oogenesis, we observed a drastic reduction in the fertility of adult males exposed to warm temperature (29 °C). Here, we show that males become infertile at 29 °C because of low sperm abundance and quality. The low sperm abundance at 29 °C does not stem from reduced germline stem cell or spermatid numbers, as those numbers remain comparable between 29 °C and control 25 °C. Notably, males at cold 18 °C and 29 °C had similarly increased frequencies of spermatid elongation and individualization defects which, considering the high sperm abundance and male fertility measured at 18 °C, indicate that spermatogenesis has a high tolerance for elongation and individualization defects. Interestingly, the abundance of sperm at 29 °C decreases abruptly and with no evidence of apoptosis as they transition into the seminal vesicle near the end of spermatogenesis, pointing to sperm elimination through an unknown mechanism. Finally, sperm from males at 29 °C fertilize eggs less efficiently and do not support embryos past the first stage of embryogenesis, indicating that poor sperm quality is an additional cause of male infertility at 29 °C.

Notch pathway is required for protection against heat stress in spermatogonial stem cells in medaka

Gamete production is a fundamental process for reproduction; however, exposure to stress, such as increased environmental temperature, can decrease or even interrupt this process, affecting fertility. Thus, the survival of spermatogonial stem cells (SSCs) is crucial for the recovery of spermatogenesis upon stressful situations. Here, we show that the Notch pathway is implicated in such survival, by protecting the SSCs against thermal stress. First, we corroborated the impairment of spermatogenesis under heat stress in medaka, observing an arrest in metaphase I at 10 days of heat treatment, an increase in the number of spermatocytes, and downregulation of ndrg1b and sycp3. In addition, at 30 days of treatment, an interruption of spermatogenesis was observed with a strong loss of spermatocytes and spermatids. Then, the exposure of adult males to thermal stress condition induced apoptosis mainly in spermatogenic and supporting somatic cells, with the exception of the germinal region, where SSCs are located. Concomitantly, the Notch pathway-related genes were upregulated, including the ligands (dll4, jag1-2) and receptors (notch1a-3). Moreover, during thermal stress presenilin enhancer-2 (pen-2), the catalytic subunit of γ-secretase complex of the Notch pathway was restricted to the germinal region of the medaka testis, observed in somatic cells surrounding type A spermatogonia (SGa). The importance of Notch pathway was further supported by an ex vivo approach, in which the inhibition of this pathway activity induced a loss of SSCs. Overall, this study supports the importance of Notch pathways for the protection of SSCs under chronic thermal stress.

Effect of Acute Melatonin Injection on Metabolomic and Testicular Artery Hemodynamic Changes and Circulating Hormones in Shiba Goats under Sub-Tropical Environmental Conditions

The beneficial effects of melatonin were investigated to mitigate various detrimental effects and toxicity on reproductive performance. The present study aimed, for the first time, to explore the effect of intravenous melatonin injection on testicular artery hemodynamics (TH) and metabolomic changes, reproductive hormones in heat-stressed bucks. Ten bucks were randomly split into two groups (five each): (1) the melatonin group, treated with a single intravenous dose of melatonin solution containing 10 mg melatonin each, and (2) the control group, which was treated with 10 mL of the vehicle without melatonin. Changes in the TH at the level of the supra testicular artery (STA) were assessed by triplex ultrasonography just before (0 h) and at 0.5, 2, 7, 24, and 168 h after melatonin or vehicle administration. Doppler velocity parameters of peak systolic velocity (PSV; cm/s), end-diastolic velocity (EDV; cm/s), and time average maximum velocity (TAMAX; cm/s) were measured. Doppler indices (resistive index; RI and pulsatility index; PI), systole/diastole (S/D) ratio and total arterial blood flow volume (TABFV; ml/minute) were measured. Peripheral concentrations of FSH, LH, inhibin, melatonin, testosterone (T), estradiol (E2), and cortisol were measured just before injection (0 h) and at 0.5, 2, 7, and 24 h and daily up to day 7 post administration in both groups. Results revealed reductions in the RI values and increases in the TABFV in the melatonin group compared to the control one, especially 2 h after administration. Significant increases in concentrations of FSH, T, E2, and melatonin and decreases in cortisol and inhibin in the melatonin group compared to the control one. Plasma metabolomic analysis at 2 h indicated the up-regulation of L-glutamine, L-arginine, sorbitol, D-glucose, ascorbic acid, and ornithine and the down-regulation of D-xylose, D-arabitol, ribitol, and oleic acid in the melatonin versus the control group. In conclusion, acute administration of melatonin (10 mg IV) enhanced testicular artery blood flow and plasma reproductive hormones in the Shiba goat under heat-stress circumstances.

5-Aminolevulinic acid combined with ferrous iron ameliorates scrotal heat stress-induced spermatogenic damage by enhancing HO-1 expression

OBJECTIVE

To explore whether 5-Aminolevulinic acid combined with ferrous iron (5-ALA/Fe²⁺) could protect testicular tissues damage of mice subjected to heat stress (HS) and provide its underlying mechanisms.

METHODS

5-ALA/Fe²⁺ was administered intragastrically to mice for 10 days, then exposed to a scrotal heat stress at 43°C for 20 min on third day. Testes were harvested for morphologic and histopathological examination, oxidative stress, apoptosis, heme oxygenase-1 (HO-1) and inflammation detection. The mitogen-activated protein kinases (MAPK) signaling pathway in testis and CD4⁺FoxP3⁺regulatory T (Treg) cells in spleen were also investigated.

RESULTS

Compared to control group, the testis weight decreased and histological damage severed in HS group. Besides, HS also increased the oxidative stress, apoptosis and inflammation in testis. However, these indicators were ameliorated after 5-ALA/Fe²⁺ treatment but deteriorated after receiving ZnPPIX. The expression of HO-1 was increased both in HS group and 5-ALA/Fe²⁺ group. The protein expression levels of MAPK proteins were activated by HS and inhibited by 5-ALA/Fe²⁺. The CD4⁺FoxP3⁺ Treg generation was reduced by HS and increased by 5-ALA/Fe²⁺.

CONCLUSION

In this study, we have demonstrated that 5-ALA/Fe²⁺ ameliorated the spermatogenic damage induced by scrotal heat stress via up-regulating the expression of HO-1 and inhibiting MAPK mediated oxidative stress and apoptosis and inducing CD4⁺Foxp3⁺ Tregs to inhibit the inflammation induced by HS in mice.

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.

Melatonin improves post-thaw sperm quality after mild testicular heat stress in rams

The objective was to determine effects of slow-release melatonin on post-thaw sperm quality in rams exposed to mild testicular heat stress (HS; scrotal neck insulation). Twelve yearling Dorset rams were randomly and equally allocated to receive either 36 mg melatonin in 1 ml corn oil or 1 ml corn oil injected subcutaneously (SQ); 15 day later, all rams had HS for 96 h (start of HS = start of Week 0). Semen was collected before HS and once weekly from Weeks 1 to 7, extended in Steridyl CSS One Step, held at 5°C for ~3 h, loaded into 0.5 ml straws, held 5 cm above liquid nitrogen for 10 min and then plunged. Computer assisted semen analysis (CASA) was conducted on frozen-thawed sperm. There were group and week effects for total and progressive motility (p < .001), plus group and week effects and group*week interactions (p < .001) for post-thaw total abnormalities, acrosome integrity, post-thaw sperm DNA fragmentation index (DFI) and high mitochondrial membrane potential (HMMP). Post-thaw sperm total and progressive motility, acrosome integrity and HMMP were higher (p < .05) in melatonin versus control groups from Weeks 1 to 7, and the melatonin group reached baseline level (pre-heat stress) at Week 7 (75.79 ± 0.96, 65.48 ± 1.51, 75.00 ± 0.89 and 67.00 ± 1.06, respectively; mean ± SEM). Conversely, post-thaw sperm total abnormalities and DFI were lower (p < .05) in melatonin versus control, and both reached baseline at Week 7 in the melatonin group (26.00 ± 0.57 and 5.66 ± 0.17, respectively). Coiled tails, distal midpiece reflexes, distal cytoplasmic droplets, ruffled acrosomes, bowed midpieces, pyriform heads and knobbed acrosomes were the most common abnormalities in both groups, with lower percentages in melatonin-treated rams. Results supported our hypothesis that HS reduces post-thaw sperm quality, and that melatonin lessens those reductions, manifested by significantly better total and progressive motility, acrosome integrity and HMMP, and fewer sperm total abnormalities and DFI.

Effects of a single dose of long-acting FSH on testicular blood flow, testicular echotexture, and circulating testosterone, estradiol, and nitric oxide in rams during the non-breeding season

The present study investigated the effect of a single administration of long-acting follicle simulation hormone (FSH) on testicular blood perfusion as measured by pulsed-wave Doppler ultrasonography, testicular echotexture, and circulating testosterone (T), estradiol (E2), and nitric oxide (NO) in the plasma of rams in the non-breeding season. Twelve Ossimi rams were subjected to either a single administration of long-acting FSH subcutaneously (FSH group; n = 6) or the vehicle (control group; n = 6). Assessment of testicular hemodynamics at the level of the supratesticular artery was performed just before administration (0 h), and at 4, 24, 48, 72, 96, and 168 h after FSH or the vehicle administrations. Testicular volume (TV), and echotexture of testicular parenchyma including pixel intensity and heterogeneity were derived by the computer analysis software. Concentrations of T, E2, and NO were measured using commercial kits. Results revealed significant decreases (P ˂ 0.05) in the values of Doppler indices (resistive index: RI and pulsatility index: PI), especially at 48 h after administration of FSH (RI: 0.42 ± 0.02, PI: 0.56 ± 0.04) compared to their values in the control group (RI: 0.54 ± 0.03, PI: 0.77 ± 0.04). FSH administration induced significant decreases (P ˂ 0.05) in the pixel intensity of testicular parenchyma. Testicular volume and T concentrations were not significantly changed (P ˃ 0.05). Concentrations of E2 increased significantly (P ˂ 0.05) at 48 h and 72 h after FSH administration. (30.07 ± 5.23 pg/ml, 29.93 ± 1.44 pg/ml, respectively) compared to their values before FSH administration (14.63 ± 1.37 pg/ml). Concentrations of NO increased significantly (P ˂ 0.05) in the FSH group between 4 h to 48 h compared to the values in the control one. In conclusion, a single administration of long-acting FSH enhanced testicular blood perfusion as measured by pulsed Doppler ultrasonography in rams during the non-breeding season. Concurrently, significant increases in the concentrations of E2 and NO were found.

An updated insight on testicular hemodynamics: Environmental, physiological, and technical perspectives in farm and companion animals

In all organs, control of blood flow is important but might be particularly critical for testicular functions. This is because of the very low oxygen concentration and high metabolic rate of the seminiferous tubules, the physiological temperature of the testis, and its location outside the abdominal cavity. Many factors affect the characteristics of TBF in farm and companion animals, such as environment (thermal and seasonal effects) and physiological (species, breeds, age, body weight, and sexual maturity). Thermal environment stress has detrimental effects on spermatogenesis and consequently has more serious impacts on both human and animal fertility. Numerous studies have been performed to assess TBF in different animal species including bulls, rams, bucks, alpacas, stallions, and dogs with varied results. Hence, assessment of TBF by Doppler ultrasonography is of great importance to estimate the effect of high environment temperature on testicular functions. Also, differences observed in the TBF may result from different technical aspects such as the identification of the segment of the testicular artery to be examined. In the current review, we focused on the imperative roles of TBF in various animal species. Besides, we discussed in detail various factors that could affect TBF. These factors can significantly modify the TBF and thus should be considered when establishing reference values in farm animals for better clinical diagnosis. The information provided in this review is valuable for researchers and veterinarians to help them a better understanding of testicular hemodynamics for the proper evaluation of breeding soundness examination in males.

Thermal male contraception: A study of users' motivation, experience, and satisfaction

PURPOSE

The aim of this study is to evaluate the motivations, experience, and acceptability of thermal male contraception (TMC) in male partners of couples requesting the use of TMC as the only couple contraceptive.

MATERIALS AND METHODS

To the 72 men of couples seeking male contraception and using TMC between 2011 and 2019, we suggested an anonymous online survey (93 questions) exploring population characteristics, contraceptive histories, motivations for choosing TMC, patient experience at the successive phases of use, relations with partner and environment, and satisfaction with this method.

RESULTS

Sixty-seven men agreed to participate (93% response rate); 63 responses were complete and were analyzed (94% participation rate). The main motivations for choosing TMC were "not using hormones" (n = 59/63, 94%) and using a method regarded as "natural" (n = 49/63, 78%). Most of the men surveyed (68%) adopted the method in less than 2 weeks. During the contraception use phase (n = 59 men), they described significantly improved sexual satisfaction, compared to that experienced with their previous contraceptive methods, and they reported high confidence (100% rather/totally confident partner) and support (88% rather/totally supporting partner) from their partner. Most men (n = 35/59, 59%) also reported improved self-esteem. The main negative point was discomfort, reported by 24% of the men. The overall satisfaction score of using this method was 3.78 ± 0.46/4, and 100% of the men reported that they would recommend the method to other men.

DISCUSSION AND CONCLUSION

Men using TMC successfully assumed the responsibility for and performed a daily task to provide couple contraception. This positive evaluation, together with the already published contraceptive efficacy and reversibility of TMC, should encourage the development of this method.

Cellular responses and microRNA profiling in bovine spermatozoa under heat shock

Sperm function is susceptible to adverse environmental conditions. It has been demonstrated that in vivo and in vitro exposure of bovine sperm to elevated temperature reduces sperm motility and fertilizing potential. However, the cascade of functional, cellular and molecular events triggered by elevated temperature in the mature sperm cell remains not fully understood. Therefore, the aim of this study was to determine the effect of heat shock on mature sperm cells. Frozen-thawed Holstein sperm were evaluated immediately after Percoll purification (0 h non-incubation control) or after incubation at 35°C, 38.5°C, and 41°C for 4 h. Heat shock reduced sperm motility after 3 - 4 h at 41°C while mitochondrial activity was reduced by 38.5 and 41°C when compared to the control. Heat shock also increased sperm reactive oxygen species production and caspase activity. Heat-shocked sperm had lower fertilizing ability, which led to diminished cleaved and blastocyst rates. Preimplantation embryo developmental kinetics was also slowed and reduced by sperm heat shock. The microRNA (miR) profiling identified >300 miRs in bovine sperm. Among these, three and seven miRs were exclusively identified in sperm cells exposed to 35 and 41°C, respectively.

Exogenous gonadotropin-releasing hormone counteracts the adverse effect of scrotal insulation on testicular functions in bucks

This study determined the effects of scrotal insulation on testicular functions in bucks and evaluated the impact of exogenous gonadotropin-releasing hormone (GnRH) administration before scrotal insulation on sperm production and testicular vascular dynamics. Twelve bucks were randomly divided into three groups: scrotal-insulated animals without GnRH treatment (INS), scrotal-insulated animals treated previously with GnRH (GnRH + INS), and animals without insulation as controls (CON). Doppler ultrasonography was used to evaluate testicular vascular changes, and semen samples were collected to assess seminal parameters. Testicular samples were collected from slaughtered bucks at the end of the experiment for histological investigations and immunohistochemical analysis for caspase 3 (apoptotic marker), and a vascular endothelial growth factor (VEGF; hypoxic marker) evaluation. Sperm motility drastically decreased (33%) in the INS group on day 8 compared with those in the GnRH + INS and CON groups (58% and 85%, respectively). Testicular blood flow significantly decreased for 3 and 2 weeks in the INS and GnRH + INS groups, respectively. The pulsatility index (PI) reached pretreatment values at 5 and 4 weeks after insulation in the INS and GnRH + INS groups, respectively. The resistance index (RI) values increased in both insulated groups for the first 2 weeks and decreased to control values 4 weeks after insulation. However, the maximum velocity (VP) started to increase reaching pretreatment values by the 5th and 3rd weeks after insulation in the INS and GnRH + INS groups, respectively. Histological investigations showed a marked reduction in lipid inclusions in Sertoli cells in the GnRH + INS group compared with those in the INS group. The distributions of both caspase 3 and VEGF decreased in the GnRH + INS group compared with those in the INS group. This study showed that the administration of a single dose of GnRH delayed the negative effects of scrotal insulation on different seminal traits and revealed the pivotal role of GnRH in compensating testicular insulation in bucks.

Thermoregulation of the bovine scrotum 2: simulated acute and chronic heat waves reduces the scrotal thermoregulatory capability of Wagyu bulls

The objective of this study was to investigate the effect of acute and chronic heat load events on scrotal temperature (ST), body temperature (BT) and bull behaviour, and to examine the interrelationship between these parameters; the underlying hypothesis was that adverse heat treatments delivered in a temperature controlled environment will lead to thermoregulatory dysfunction of the bull scrotum. Six sexually mature Wagyu bulls were used in this study with data loggers surgically implanted into the abdominal cavity and scrotum. Body temperate and ST were recorded at 30-min intervals for the duration of the study. There were two housing locations used throughout the study, outdoor pens and climate control rooms. The study was designed as a four-phase crossover design with two heat treatments: (1) a 5-day acute challenge, and (2) a 14-day chronic challenge. The study was also blocked by phase to control for systematic change between phases with a thermoneutral (TN) phase in outdoor pens between each heat challenge. Observations within the climate rooms were conducted at 1-h intervals and data on panting scores (PS), respiration rate (RR), posture (standing or lying) and general behaviours (feeding, drinking, ruminating) recorded. Ambient temperature (AT, °C) and relative humidity (RH, %) were obtained at 10-min intervals and used to calculate the temperature humidity index (THI). Multiple models were conducted using a linear mixed effects model that contained different permutations of date and time factors and interactions as well as inclusion of an autoregressive parameter. The strongest model based on Akaike's information criterion (AIC) was selected and further analysed. Ambient conditions during heat treatments were consistent with heat load and bulls showed typical physiological symptoms of the same. Maximum ST for acute and chronic treatments occurred once AT had exceeded 34 °C for at least 3 h (acute 35.59 °C at 1500 h; chronic 35.18 °C at 1400 h), whereas during TN conditions, maximum ST was at 2100 h. All phases showed variation in ST throughout the day. There were strong cross correlations between ST and RR during the heat treatments (acute r = 0.918, P < 0.0001; chronic r = 0.916, P < 0.0001), but not during TN (r = 0.411, P < 0.05). Our results confirmed that the ST of the bulls used in this study was not held at a constant temperature and that there was a possible connection between ST and RR. We have shown that during a period of heat load, the thermoregulatory mechanisms thought responsible for maintaining bovine ST appear to breakdown.

Synthetic leptin c-fragment peptide minimises heat-induced impairment of spermatogenesis in mice via Stat3 signalling

Mammalian spermatogenesis is a temperature-sensitive process, and an increase in testicular temperature impairs spermatogenesis. Leptin modulates testicular activity, but the effect of leptin or its synthetic analogue on heat-induced testicular impairment is unclear. We investigated the effects of synthetic leptin peptide (116-130 amides) on testicular activity in heat-stressed mice model. 15 adult mice (25.54 ± 1.43 g) were selected for the study. Ten mice were subjected to a single heat stress treatment (HS) at 43 °C for 15 min by submerging the lower half of the body in a thermostatic water bath. After heat treatment, mice were divided into two groups, the heat-stressed HS group (n = 5) and the second group as HSL, treated with leptin peptide (116-130 amide) for 14 days. The HS group showed a significant (p < 0.05) decline in the GSI (0.25 ± 0.018), Johnsenscore (4.5 ±.19), seminiferous tubule diameter (160.75 ± 10.18 μm), germinal epithelium height, (GEH) (37.5 ± 1.59 μm) compared to the CN (GSI-0.37 ± 0.015; Johnsen score-7.9 ± 0.20; GEH- 73.25 ± 1.29 μm; tubule diameter-230.25 ± 1.39 μm) and the HSL groups (GSI-0.38 ± 0.014; Johnsen' score-8.0 ± 0.32; GEH- 37.5 ± 1.59 μm; tubule diameter-160.75 ± 10.18 μm) groups. Heat treatment significantly (p < 0.05) increased the intra-testicular levels of leptin (HS-20.11 ± 2.1 pg/mg protein; CN-10.50 ± 0.17 pg/mg protein; HSL-12.99 ± 0.52 pg/mg protein) with a reduced level of pStat3, suggesting leptin resistance during testicular hyperthermia. Furthermore, heat treatment was associated with significantly (p < 0.05) decreased germ cell proliferation and reduced circulating testosterone levels (HS-2.69 ± 2.01 ng/mL; CN-7.69 ± 0.32 ng/mL; HSL-5.36 ± 0.73 ng/mL). However, the circulating androstenedione levels showed a significant (p < 0.05) increase in the HS group (0.75 ± 0.03 ng/mL) compared to the CN (0.51 ± 0.02 ng/mL) and HSL (0.57 ± 0.07 ng/mL) groups. Immunolocalisation of 3β-HSD showed moderate to faint staining in the Leydig cells in the HS group compared to the CN and HSL groups. Treatment with leptin peptide resulted in decrease in the intra-testicular leptin levels with increased phosphorylation of Stat3, suggesting improved leptin resistance, which was positively associated with increased germ cell proliferation, elevated testosterone levels, and improved testicular histoarchitecture. Testicular hyperthermia may cause leptin resistance and impaired leptin signalling, decreased testosterone biosynthesis and suppressed spermatogenesis, which could be a manifestation of leptin resistance. Treatment with leptin peptide improves leptin signalling and testicular activity in heat-stressed mice, but the underlying mechanism is still unclear.

Review: What have we learned about the effects of heat stress on the pig industry?

Pig production faces seasonal fluctuations. The low farrowing rate of sows mated in summer, increased carcass fatness of progeny born to the sows mated in summer, and slower growth rate of finisher pigs in summer are three economically important impacts identified in the pig industry. The purpose of this review is to examine advances over the past decade in understanding the mechanisms underlying the three impacts associated with summer conditions, particularly heat stress (HS), and to provide possible amelioration strategies. For impact 1, summer mating results in low farrowing rates mainly caused by the high frequency of early pregnancy disruptions. The contributions of semen DNA damage, poor oocyte quality, local progesterone concentrations, and suboptimal embryonic oestrogen secretion are discussed, as these all may contribute to HS-mediated effects around conception. Despite this, it is still unclear what the underlying mechanisms might be and thus, there is currently a lack of commercially viable solutions. For impact 2, there have been recent advances in the understanding of gestational HS on both the sow and foetus, with gestational HS implicated in decreased foetal muscle fibre number, a greater proportion of lighter piglets, and increased carcass fatness at slaughter. So far, no effective strategies have been developed to mitigate the impacts associated with gestational HS on foetuses. For impact 3, the slowed growth rate of pigs during summer is one reason for the reduced carcass weights in summer. Studies have shown that the reduction in growth rates may be due to more than reductions in feed intake alone, and the impaired intestinal barrier function and inflammatory response may also play a role. In addition, it is consistently reported that HS attenuates fat mobilisation which can potentially exacerbate carcass fatness when carcass weight is increased. Novel feed additives have exhibited the potential to reduce the impacts of HS on intestinal barrier function in grower pigs. Collectively, based on these three impacts, the economic loss associated with HS can be estimated. A review of these impacts is warranted to better align the future research directions with the needs of the pig industry. Ultimately, a better understanding of the underlying mechanisms and continuous investments in developing commercially viable strategies to combat HS will benefit the pig industry.

Comparative genomics reveals molecular mechanisms underlying health and reproduction in cryptorchid mammals

BACKGROUND

Mammals have wide variations in testicular position, with scrotal testes in some species and ascrotal testes in others. Although cryptorchidism is hazardous to human health, some mammalian taxa are natural cryptorchids. However, the evolution of testicular position and the molecular mechanisms underlying the maintenance of health, including reproductive health, in ascrotal mammals are not clear.

RESULTS

In the present study, comparative genomics and evolutionary analyses revealed that genes associated with the extracellular matrix and muscle, contributing to the development of the gubernaculum, were involved in the evolution of testicular position in mammals. Moreover, genes related to testicular position were significantly associated with spermatogenesis and sperm fertility. These genes showed rapid evolution and the signature of positive selection, with specific substitutions in ascrotal mammals. Genes associated with testicular position were significantly enriched in functions and pathways related to cancer, DNA repair, DNA replication, and autophagy.

CONCLUSIONS

Our results revealed that alterations in gubernaculum development contributed to the evolution of testicular position in mammals and provided the first support for two hypotheses for variation in testicular position in mammals, the "cooling hypothesis", which proposes that the scrotum provides a cool environment for acutely heat-sensitive sperm and the "training hypothesis", which proposes that the scrotum develops the sperm by exposing them to an exterior environment. Further, we identified cancer resistance and DNA repair as potential protective mechanisms in natural cryptorchids. These findings provide general insights into cryptorchidism and have implications for health and infertility both in humans and domestic mammals.

Immunohistochemical insights into a hidden pathology: Canine cryptorchidism

Cryptorchidism is a common disorder in the canine population with some aspects still unclear. Although the bilateral condition is known to lead to fertility problems and predisposition to testicular cancer, the neoplastic risk for scrotal testis in unilateral cryptorchid dog is controversial. Therefore, the therapeutic approach to the canine unilateral cryptorchid is arbitrary so far. This study aimed to investigate precancerous testicular lesions, such as immaturity and atrophy, and compare them in scrotal and undescended testes using an in-depth diagnostic analysis based on immunophenotypic patterns. With this purpose, 26 adult male dogs of different ages and breeds, affected by unilateral or bilateral cryptorchidism were enrolled. After surgical removal, testes were examined immunohistochemically to assess their positivity for specific markers of the canine foetal/neonatal period, that is vimentin (VIM), cytokeratin (CK), desmin (DES), inhibin-α (INH), and anti-Müllerian hormone (AMH) in Sertoli cells, and placental alkaline phosphatase (PLAP) in germ cells. Except for the ubiquitous VIM, all the markers were more expressed in neoplastic gonads compared to healthy ones (P < 0.05). Similarly, testes detected with Sertoli cell-only tubules as well as with Sertoli cells hyperplasia showed higher expression than gonads without such alterations for CK, DES, AMH and PLAP, and for CK and DES, respectively (P < 0.05). The same trend was observed in undescended respect to scrotal testes even though their positivity was significant only for DES, INH and AMH (P < 0.05). Immunohistochemical positivity found in scrotal testes of unilateral cryptorchid dogs, even in absence of detectable anatomical abnormalities, was suggestive of precancerous lesions. Despite the limited sample size, this study could help to clarify the predisposition to neoplastic development in normally descended testes. These markers expression in adult life could allow identifying the early stages of the testicular carcinogenesis process besides suggesting a precautionary bilateral surgical approach in unilateral cryptorchid dogs.

Evaluation of patient compliance with the use of scrotal cooling devices

Objective

To evaluate the compliance of infertile men with the use of scrotal cooling devices. As a secondary objective, sperm parameters, deoxyribonucleic acid fragmentation, and hormone profiles were examined.

Design

This exploratory study on scrotal cooling provided scrotal cooling devices to men with primary infertility and abnormal semen parameters. Feedback on the devices after their use was gathered in the form of a questionnaire, and semen parameters were examined after device use.

Setting

Single center infertility clinic in Toronto, Ontario, Canada.

Patient(s)

Patients with primary infertility and abnormal semen parameters were prospectively evaluated before and after scrotal cooling.

Intervention(s)

One of two scrotal cooling devices (Underdog or Snowballs) was used, on the basis of patient preference.

Main Outcome Measure(s)

Questionnaires were completed by patients on compliance with device use and concerns about and recommendations for improving the cooling devices. Baseline deoxyribonucleic acid fragmentation index, sperm parameters, and hormones were measured at the initial visit (t = 0) and at subsequent visits (t = 4–12 weeks). Statistical comparison of values before and after scrotal cooling was performed.

Result(s)

Forty patients were enrolled in the study, and the questionnaire was completed by 65.0% (n = 26). Most respondents (76.9%) used scrotal cooling less than the recommended duration. Respondents believed that the devices were uncomfortable (31.5%), impeded work (21.0%), and lost cooling rapidly (14.3%). Significant increases in sperm motility and vitality (from 25.4 % to 29.0% and from 64.8% to 71.7%, respectively) were demonstrated after scrotal cooling.

Conclusion(s)

Most patients were not compliant with the recommended use of the scrotal cooling devices because of issues of comfort, convenience, and concealability. Further work on improving scrotal cooling devices is necessary to enhance their potential as a therapeutic tool for men with abnormal sperm parameters and infertility.

Scrotal subcutaneous temperature is increased by scrotal insulation or whole-body heating, but not by scrotal neck insulation; however, all three heat-stress models decrease sperm quality in bulls and rams

Ruminant testes are ~2-6 °C below body temperature; increased testicular temperature reduces sperm motility and morphology. Our objective was to serially monitor scrotal subcutaneous temperatures during testicular heat stress and relate those to sperm quality. Two experiments were conducted, with temperature sensors surgically implanted in scrotal subcutaneous tissues recording temperatures every 15 min and semen collected and evaluated weekly. After an initial control interval, testicular temperature was increased. In Experiment 1, in two Angus bulls, whole-scrotum insulation for 96 h increased scrotal subcutaneous temperatures by ~2.0-2.5 °C (P < 0.05). Total and progressive motility decreased (P < 0.05) and reached a nadir at Week 3 (~20 and 10%, respectively). Furthermore, morphologically normal sperm and acrosome integrity also decreased significantly, reaching nadirs at Weeks 3 (15%) and 4 (34%). In Experiment 2, 10 Dorset rams were allocated randomly into two equal groups and either: 1) exposed to 28 °C ambient temperature and 30-34% RH for 8 h/d for 4 d; or 2) subjected to scrotal neck insulation that was applied and removed at the same time as the start and completion, respectively, of heat exposures in the other rams. Scrotal subcutaneous temperatures (monitored in three rams per group) were increased in response to whole-body heating (~0.8 °C, P < 0.05), but not significantly changed by scrotal neck insulation. Decreases in sperm quality were generally similar between treatments, with the most profound changes evident 4 wk after heat stress, with ~10 percentage point reductions in both total and progressive motility and ~10 and 20 percentage point decreases in morphologically normal sperm in rams with whole-body heating versus scrotal neck insulation, respectively. In conclusion, scrotal subcutaneous temperature was significantly increased by scrotal insulation or whole-body heating, but not by scrotal neck insulation; however, all three heat-stress models decreased sperm motility and morphology in bulls and rams.

Testicular thermoregulation with respect to spermatogenesis and contraception

There has been some evidence that a short heating exposure of the testicles can lead to temporary sterility. However, little attention has been paid to analyzing the temperature/time pattern throughout the testicle and how metabolism and blood perfusion affect the temperature profile. We use the Penne bioheat equation that accounts for the elements of conduction, perfusion, and metabolism along with the COMSOL Finite Element Method for the analysis of this thermoregulation problem. Typically, the testicles were modeled as two uniform spheres and exposed to an increase in surface temperature of 42 °C for 30 min. We found that heat produced by tissue metabolism had a minor effect on the temperature pattern. However, blood flow from the core (at 37 °C) could prevent the region where the testicles touch each other from reaching the target temperature of 42 °C. Further, we found that for animals, as rodents and monkeys that are used for contraception studies, the temperature distribution on heating testicles is much more uniform than for humans. Thus, extrapolation results from animal models to humans should be done with caution.

Development of a putative adverse outcome pathway network for male rat reproductive tract abnormalities with specific considerations for the androgen sensitive window of development

Structured approaches like the adverse outcome pathway (AOP) framework offer great potential for depicting complex toxicological processes in a manner that can facilitate informed integration of mechanistic information in regulatory decisions. While this concept provides a structure for organizing evidence and facilitates consistency in evidence integration; the process, inputs, and manner in which AOPs and AOP networks are developed is still evolving. Following the OECD guiding principles of AOP development, we propose three AOPs for male reproductive tract abnormalities and derive a putative AOP network. The AOPs were developed using a fundamental understanding of the developmental biology of the organs of interest, paying close attention to the gestational timing of key events (KEs) to very specifically inform the domain of life stage applicability for the key event relationships (KERs). Chemical stressor data primarily from studies on low molecular weight phthalates (LMWPs) served to 'bound' the pathways of focus in this dynamic period of development and were integrated with the developmental biology data through an iterative process to define KEs and conclude on the extent of evidence in support of the KERs. The AOPs developed describe the linkage between 1) a decrease in Insl3 gene expression and cryptorchidism, 2) the sustained expression of Coup-tfII and hypospadias and 3) the sustained expression of Coup-tfII and altered Wolffian duct development/ epididymal agenesis. A putative AOP network linking AOP2 and AOP3 through decreased steroidogenic biosynthetic protein expression and converging of all AOPS at the population level impaired fertility adverse outcome is proposed. The network depiction specifies and displays the KEs aligned with their occurrence in gestational time. The pathways and network described herein are intended to catalyze collaborative initiatives for expansion into a larger network to enable effective data collection and inform alternative approaches for identifying stressors impacting this sensitive period of male reproductive tract development.

Heat stress response of somatic cells in the testis

The testis is a temperature-sensitive organ that needs to be maintained 2-7 °C below core body temperature to ensure the production of normal sperm. Failure to maintain testicular temperature in mammals impairs spermatogenesis and leads to low sperm counts, poor sperm motility and abnormal sperm morphology in the ejaculate. This review discusses the recent knowledge on the response of testicular somatic cells to heat stress and, specifically, regarding the relevant contributions of heat, germ cell depletion and inflammatory reactions on the functions of Sertoli and Leydig cells. It also outlines mechanisms of testicular thermoregulation, as well as the thermogenic factors that impact testicular function.

Review of the impact of heat stress on reproductive performance of sheep

Heat stress significantly impairs reproduction of sheep, and under current climatic conditions is a significant risk to the efficiency of the meat and wool production, with the impact increasing as global temperatures rise. Evidence from field studies and studies conducted using environmental chambers demonstrate the effects of hot temperatures (≥ 32 °C) on components of ewe fertility (oestrus, fertilisation, embryo survival and lambing) are most destructive when experienced from 5 d before until 5 d after oestrus. Temperature controlled studies also demonstrate that ram fertility, as measured by rates of fertilisation and embryo survival, is reduced when mating occurs during the period 14 to 50 d post-heating. However, the contribution of the ram to heat induced reductions in flock fertility is difficult to determine accurately. Based primarily on temperature controlled studies, it is clear that sustained exposure to high temperatures (≥ 32 °C) during pregnancy reduces lamb birthweight and will, therefore, decrease lamb survival under field conditions. It is concluded that both ewe and ram reproduction is affected by relatively modest levels of heat stress (≥ 32 °C) and this is a concern given that a significant proportion of the global sheep population experiences heat stress of this magnitude around mating and during pregnancy. Despite this, strategies to limit the impacts of the climate on the homeothermy, behaviour, resource use and reproduction of extensively grazed sheep are limited, and there is an urgency to improve knowledge and to develop husbandry practices to limit these impacts.

Scrotal thermoregulation and sequential sperm abnormalities in buffalo bulls (Bubalus bubalis) under short-term heat stress

Heat stress reduces the reproductive capacity of bulls raised in tropical climate. However, the reestablishment of scrotal thermoregulation and the dynamics of sperm defects emergence after stress are not completely known in buffaloes. Thus, the study aimed to evaluate the effect of short-term heat stress over scrotal thermoregulation and sperm attributes, relating them to spermatogenesis stages. Five buffalo bulls went through scrotal insulation during 48 h (from day 0 to day 2). Semen samples were collected every 7 days (from day -7 to day 49) and analyzed about the progressive motility, viability, and sperm morphology. Heat stress significantly destabilized scrotal thermoregulation (P < 0.001). Scrotal temperature was from 4.2 to 6.3 °C lower than the core body temperature, except on insulation days (P < 0.001), and returned to the basal condition five days after the removal of the stressing stimulus. More significant deleterious effects were observed in sperm morphology than in cell concentration, motility, and viability. The chronology of morphologic defects expression demonstrated tail defects (days 7-14), cytoplasmic droplets (days 14-28), and head defects (day 28), returning to pre-insulation condition 35 days after the thermal challenge. Thus, hyperthermia harmed more intensely spermatozoa in epididymal transit, elongated spermatids, and secondary spermatocytes. It is concluded that water buffalo bulls present a peculiar manifestation of sperm morphology after short-term stress, indicating an important difference related to the bovine species. Therefore, during the andrological evaluation of buffalo bulls, it is necessary to avoid the allometric extrapolation between these species.

Susceptibility of boar spermatozoa to heat stress using in vivo and in vitro experimental models

Induction of heat stress as an experimental procedure in animals is commonly used to examine heat-related impacts on sperm quality. This study aimed to develop potential heat stress models that could be used at any time of the year, to advance the study of seasonal infertility in the pig under controlled conditions. Heat stress was induced by either housing boars (n = 6) at 30 °C inside a hot room for 42 days (55-65% humidity; LD 12:12 h; in vivo), or by heating boar semen (n = 7) for 30 min at various temperatures (35.5, 38.8, 40, 42, 46, 50, 54 and 60 °C; in vitro). Sperm motility was then characterized by computer-assisted sperm analysis (CASA; IVOS version 10: Hamilton Thorne, USA), and DNA integrity was evaluated by terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) and flow cytometry. Our in vivo hot room model induced biologically meaningful levels of DNA damage in boar spermatozoa (10.1 ± 1.9 hot room vs. 6.7 ± 1.7% control; P > 0.05), although not statistically significant from controls. Moreover, sperm concentration and motility parameters did not differ between treatments (P > 0.05). Compared to the 38.8 °C control, our in vitro heat shock model significantly increased sperm DNA damage after incubation at 54 and 60 °C (3.0 ± 1.0, 2.9 ± 1.0, 1.2 ± 0.3, 2.5 ± 0.7, 9.0 ± 3.7, 16.2 ± 7.1, 14.2 ± 5.8 and 41.8 ± 18.6% respectively; P ≤ 0.05). However, these temperatures rendered sperm completely immotile or dead, with most motility parameters declining rapidly to zero above 40 or 42 °C. In conclusion, our results suggest that temperature combined with individual factors may contribute to a boar's overall susceptibility to heat stress. Refinement of these models particularly of the in vitro heat shock model could be further pursued to overcome environmental variability, reduce whole animal experiments and provide a putative diagnostic fertility screening tool to evaluate heat tolerance in the boar.

Reproductive parameters of Bos taurus and Bos indicus bulls during different seasons in tropical conditions: focus on an alternative approach to testicular assessments using ultrasonography

The aim of the present study was to evaluate the reproductive status of Bos taurus and Bos indicus bulls during different seasons when bulls were in a tropical environment focusing on systematic assessment of the testes using B-mode ultrasonography and ImageJ software to evaluate the testicular parenchymal tissues. The experimental design is a 2 × 2 factorial arrangement, with breed (Bos Taurus - Simmental; Bos indicus - Nellore) and season (summer; winter) as factors. Testicular ultrasonic evaluation and conventional semen analysis were performed. The Simmental bulls had more major sperm defects than Nellore bulls in the summer (P = 0.0001). Additionally, Simmental bulls had a greater percentage of major sperm defects during the summer than winter months P = 0.045). Furthermore, Nellore bulls had a greater testicular parenchyma echogenicity, with a greater grayscale, (caudal parenchyma, P = 0.0155; cranial parenchyma, P = 0.001) and mediastinum grayscale than Simmental bulls (Nellore = 52.32 ± 03.60; Simmental = 35.72 ± 03.67; P = 0.003). Simmental bulls also had a greater testicular lesion area (P = 0.0147). Results indicated there was susceptibility to heat stress when Simmental bulls were maintained in tropical regions. The results of the present study indicate there is an association between results when there was use of conventional andrological evaluation procedures and results from ultrasonic analysis using ImageJ software that allows for earlier identification of tissue aberrations that could lead to impaired semen quality and fertility.

Changes in miRNA levels of sperm and small extracellular vesicles of seminal plasma are associated with transient scrotal heat stress in bulls

Scrotal heat stress affects spermatogenesis and impairs male fertility by increasing sperm morphological abnormalities, oxidative stress and DNA fragmentation. While sperm morpho-functional changes triggered by scrotal heat stress are well described, sperm molecular alterations remain unknown. Recently, spermatozoa were described as accumulating miRNAs during the last steps of spermatogenesis and through epididymis transit, mainly by communication with small extracellular vesicles (sEVs). Herein, the aim was to investigate the impact of scrotal heat stress in miRNAs profile of sperm, as well as, seminal plasma sEVs. Six Nelore bulls (Bos indicus) were divided into two groups: Control (CON; n = 3) and Scrotal Heat Stress (SHS; n = 3; scrotal heat stressed during 96 h by scrotal bags). The day that the scrotal bags were removed from SHS group was considered as D0 (Day zero). Seminal plasma sEVs were isolated from semen samples collected seven days after heat stress (D+7) to evaluate sEVs diameter, concentration, and 380 miRNA levels. Sperm morpho-functional features and profile of 380 miRNAs were evaluated from semen collected 21 days after heat stress (D+21). As a control, sEVs and sperm were analyzed seven days before heat stress (D-7). Only semen parameters that were not significantly different (P > 0.05) among bulls on D-7 were addressed on D+7 and D+21. While no alterations in diameter and concentration were detected in sEVs on D+7 between CON and SHS groups, three sEVs-miRNAs (miR-23b-5p, -489 and -1248) were down-regulated in SHS bulls compared to CON on D+7; other three (miR-126-5p, -656 and -1307) displayed a tendency (0.05 < P < 0.10) to be altered. Sperm oxidative stress was higher, and the level of 21 sperm miRNAs was altered (18 down-, 3 up-regulated) in SHS bulls compared to CON on D+21. Functional analysis indicated that target genes involved in transcription activation, as well as cell proliferation and differentiation were related to the 18 down-regulated sperm miRNAs (miR-9-5p, -15a, -18a, -20b, -30a-5p, -30b-5p, -30d, -30e-5p -34b, -34c, -106b, -126-5p, -146a, -191, -192, -200b, -335 and -449a). Thus, the scrotal heat stress probably impacted testicular and epididymis functions by reducing the levels of a substantial proportion of sEVs and sperm miRNAs. Our findings suggest that miR-126-5p was possibly trafficked between sEVs and sperm and provide new insights on the mechanism by which sperm acquire miRNAs in the last stages of spermatogenesis and sperm maturation in cattle.

Canine babesiosis - a disease rarely considered in the context of male infertility

Background

Little is known about the impact of babesiosis on semen quality and fertility in dogs.

Case presentation

Four cases of infertility in male dogs after infection with Babesia canis are described. In all dogs sperm quality was low. Two dogs were castrated pharmacologically or surgically. In two dogs fertility was restored after supplementation with selenium and Vitamin E. As possible causes of spermatogenesis disorders due to the treatment of infection with Babesia canis with imidocarb, fever and disturbed testicular microcirculation are discussed.

Conclusions

These cases indicate that if males have fertility problems, question about babesiosis infection in the past should be a permanent point in the clinical interview.

Pulse-wave Doppler pulsatility and resistive indexes of the testicular artery increase in canine testis with abnormal spermatogenesis

Pulse-wave Doppler (PWD) ultrasonography of the testicular artery was recently used to compare parameters in fertile and infertile males, or males with normal and abnormal semen quality, while no studies verified the concomitant histological feature of the testis. The experimental hypothesis of the present study was that the blood flow parameters measured by PWD at different levels of the testicular artery reflect sperm attributes evaluated on spermatozoa collected from the tail of the epididymis and testicular histological characteristics. Pulse-wave Doppler parameters were recorded on both testes from 16 dogs of unknown fertility. After routine castration, epididymal spermatozoa were collected and evaluated for sperm total and progressive motility, membrane integrity, and sperm morphology. Testes were submitted to histological and immunohistochemical evaluations to quantify microscopic attributes and connective tissue and vascular area extent, respectively. The findings showed that the increased PWD indexes were suggestive of testicular histological alteration since negative correlations were found between pulsatility index and resistive index, measured in the marginal testicular artery, and histological attributes such as the seminiferous epithelial thickness (R = -0.528, P = 0.016 and R = -0.554, P = 0.005, respectively) and the tubular area/total area ratio (R = -0.494, P = 0.024 and R = -0.563, P = 0.004, respectively). Some histological characteristics, such as tubular diameter, seminiferous epithelium thickness, and the tubular area/total area ratio of the testis are correlated with the percentage of primary abnormalities (R = -0.874, P = 0.001, and R = -0.847, P = 0.001, and R = - 0.865, P = 0.001, respectively). In testes with increased sperm primary abnormalities, higher pulsatility index was found compared with testes with normal spermatogenesis in supratesticular artery (1.07 ± 0.06 vs 0.82 ± 0.23, P < 0.05), marginal artery (0.73 ± 0.04 vs 0.61 ± 0.07, P < 0.05), and intratesticular artery (0.67 ± 0.03 vs 0.43 ± 0.1, P < 0.05). Similarly, the resistive index was found significantly higher in the same vessel tracts in testes with abnormal and normal spermatogenesis (0.62 ± 0.02, 0.53 ± 0.02, and 0.46 ± 0.02 vs 0.51 ± 0.06, 0.44 ± 0.04, and 0.32 ± 0.06, respectively; P < 0.05). Our data demonstrated for the first time the relationship between PWD indexes and the contextual testicular architecture, suggesting that the pulsatility and resistive indexes could be an effective tool in andrology. In light of different histological alterations in the testis, caution is warranted in the definition of thresholds for normal and abnormal testicular blood flow indexes.

Amelioration of heat stress-induced damage to testes and sperm quality

Heat stress (HS) occurs when temperatures exceed a physiological range, overwhelming compensatory mechanisms. Most mammalian testes are ∼4-5 °C cooler than core body temperature. Systemic HS or localized warming of the testes affects all types of testicular cells, although germ cells are more sensitive than either Sertoli or Leydig cells. Increased testicular temperature has deleterious effects on sperm motility, morphology and fertility, with effects related to extent and duration of the increase. The major consequence of HS on testis is destruction of germ cells by apoptosis, with pachytene spermatocytes, spermatids and epididymal sperm being the most susceptible. In addition to the involvement of various transcription factors, HS triggers production of reactive oxygen species (ROS), which cause apoptosis of germ cells and DNA damage. Effects of HS on testes can be placed in three categories: testicular cells, sperm quality, and ability of sperm to fertilize oocytes and support development. Various substances have been given to animals, or added to semen, in attempts to ameliorate heat stress-induced damage to testes and sperm. They have been divided into various groups according to their composition or activity, as follows: amino acids, antibiotics, antioxidant cocktails, enzyme inhibitors, hormones, minerals, naturally produced substances, phenolic compounds, traditional herbal medicines, and vitamins. Herein, we summarized those substances according to their actions to mitigate HS' three main mechanisms: oxidative stress, germ cell apoptosis, and sperm quality deterioration and testicular damage. The most promising approaches are to use substances that overcome these mechanisms, namely reducing testicular oxidative stress, reducing or preventing apoptosis and promoting recovery of testicular tissue and restoring sperm quality. Although some of these products have considerable promise, further studies are needed to clarify their ability to preserve or restore fertility following HS; these may include more advanced sperm analysis techniques, e.g. sperm epigenome or proteome, or direct assessment of fertilization and development, including in vitro fertilization or breeding data (either natural service or artificial insemination).

Influence of seasonal differences on semen quality and subsequent embryo development of Belgian Blue bulls

Belgian Blue bulls are more susceptible to high temperature and humidity index (THI) than most other cattle breeds. Here, we investigated whether high ambient temperature during summer affected semen quality and subsequent embryo development in Belgian Blue cattle. For this purpose, semen samples were collected from six healthy mature Belgian Blue bulls in March (Low THI group; THI between 30.6 and 56.4) and August 2016 (High THI group; maximum THI of 83.7 during meiotic and spermiogenic stages of spermatogenesis; 14–28 days prior to semen collection) respectively. Motility, morphology, acrosome integrity, chromatin condensation, viability, and reactive oxygen species production were assessed for frozen-thawed semen. Moreover, the efficiency of blastocyst production from the frozen-thawed semen samples of the two groups was determined in vitro. Blastocyst quality was determined by assessing inner cell mass ratio and apoptotic cell ratio. Fresh ejaculates showed a higher sperm concentration in low THI when compared to the high THI group (P ≤ 0.05), whereas semen volume, subjective motility, and total sperm output were not affected (P > 0.05). In frozen-thawed semen, total and progressive motility, viability, and straight-line velocity were lower in high THI compared to the low THI group (P < 0.05), while H₂O₂ concentration, aberrant chromatin condensation, and abnormal spermatozoa were higher in the high THI group (P < 0.05). Blastocyst rates were significantly higher when low THI samples were used (P < 0.05). Moreover, the total cell number and trophectoderm cells were significantly higher (P < 0.05) in blastocysts derived from low THI samples, whereas the apoptotic cell ratio was significantly higher (P < 0.01) in blastocysts derived from high THI spermatozoa. In summary, our data show that elevated ambient temperature and humidity during summer can decrease the quality of frozen-thawed spermatozoa in Belgian Blue bulls and also affect subsequent embryo development.

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Belgian Blue bulls are more susceptible to heat stress than most other cattle breeds.

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Heat stress negatively affected the quality of Belgian Blue bulls’ spermatozoa.

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Summer high ambient temperature increased H₂O₂ production in thawed spermatozoa.

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Summer heat exposure increased morphological abnormalities of bull spermatozoa.

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Embryo development was decreased after the bulls were exposed to summer heat stress.

Does the apoptosis pathway play a critical role in gonocyte transformation?

PURPOSE

Undescended Testes (UDT) are prevalent in 2%-5% of male infants and cause malignancy and infertility. During germ cell development, abnormal gonocytes usually undergo apoptosis. This process is believed to involve BAX (Bcl-2 Associated X) protein in clearing abnormal gonocytes which may fail in UDT, resulting in persisting gonocytes causing seminomas later in life. We aim to investigate the role of BAX in gonocyte apoptosis.

MATERIALS AND METHODS

BAXKO (BAX-knockout) mice were back-crossed to OG2 mice (Oct4-promoter driving enhanced green fluorescent protein-eGFP) to produce BAXOG2 mice. Testes (wildtype-BAX^+/+, heterozygous-BAX^+/- and homozygous-BAX^-/- mice, n = 6/group) on postnatal days 1, 3, 6, 9 were fixed and embedded in OCT for frozen sectioning. Sections were labeled with Anti-Müllerian Hormone (Sertoli cell marker), Mouse Vasa Homolog (germ cell marker) and DAPI (nucleus marker) and imaged using confocal microscopy. Oct4-GFP+ve germ cells, germ cells on/off the basement membrane and Sertoli cells were counted using ImageJ followed by data analysis with GraphPad.

RESULTS

BAX^-/-OG2 mice had significantly higher number of germ cells/tubule comparing to BAX^+/+OG2 on day 9. There were Oct4-GFP+ve gonocyte-like germ cells that persisted in the center of the tubules in BAX^-/-OG2 even after the completion of gonocyte transformation. This suggests that abnormal gonocytes in BAX^-/-OG2 mice failed to undergo apoptosis and are allowed to persist.

CONCLUSION

This study demonstrated that apoptosis is important in regulating germ cell migration and differentiation during gonocyte transformation in neonatal mice. In addition, inhibition of apoptosis results in persisting neonatal gonocytes which might become seminomas in patients with UDT.

Heat stress effects on bovine sperm cells: a chronological approach to early findings

Testicular heat stress affects sperm quality and fertility. However, the chronology of these effects is not yet fully understood. This study aimed to establish the early sequential effects of heat stress in bull sperm quality. Semen and blood samples of Nellore breed bulls were collected and distributed into control and testicular heat stress (scrotal bags/96 h) groups. Semen samples were evaluated for sperm motility, abnormalities, plasma membrane integrity, acrosomal membrane integrity, mitochondrial membrane potential, sperm lipid peroxidation, seminal plasma lipid peroxidation, and DNA fragmentation. Blood plasma was also evaluated for lipid peroxidation. An increase in sperm abnormalities was observed 7 days following heat stress. After 14 days, sperm lipid peroxidation increased and mitochondrial membrane function, sperm motility, and plasma membrane integrity decreased. Heat stress effects were still observed after 21 days following heat stress. An increase in sperm DNA fragmentation was observed as a late effect after 28 days. Thus, the initial effects of heat stress (i.e., increasing sperm abnormalities and lipid peroxidation) suggest the presence of oxidative stress in the semen that alters mitochondrial function, sperm motility, plasma membrane integrity, and belatedly, DNA fragmentation. Although sperm abnormalities persisted and increased over time, sperm lipid peroxidation, in turn, increased only until 21 days after heat stress. In this regard, these findings provide a greater understanding of the chronological effects of experimentally induced heat stress on bovine sperm, providing valuable insights about spermatogenesis during the first 28 days following heat stress.

High temperature-humidity index compromises sperm quality and fertility of Holstein bulls in temperate climates

Rising temperatures caused by climate change have adverse effects on cattle physiology, welfare, health, and reproduction. Heat stress in cows affects the oocyte and embryo directly through heat shock on cellular function. Fewer data are available on the effect of high temperatures on male fertility. Temperature-humidity index (THI) is a measure for assessing the risk of heat stress that combines the effects of temperature and humidity. The aim of this study was to determine the relationship between THI and fresh or frozen-thawed sperm quality of Holstein bulls kept in temperate climates. Bull sperm data of 29,170 ejaculates from 933 bulls collected at 3 Dutch artificial insemination centers between 2015 and 2018 were evaluated. The assessed variables included total sperm motility and morphology of fresh semen, and total sperm motility, morphology, and progressive motility of frozen semen 0 and 3 h after thawing. In addition, 56-d nonreturn rates were analyzed. The assessed effects were season and THI on the day of semen collection and during spermatogenesis (30 d before collection), bull, age of bull, year, and location. Bulls were divided into 2 categories according to their age: young (<36 mo) and older (>36 mo). Overall sperm quality of young bulls improved as age increased. No effect of THI on fresh sperm variables was observed in either young or older bulls. However, high THI at spermatogenesis negatively affected the cryotolerance of sperm cells. Sperm cells from young and older bulls showed a pronounced decrease (14-18%) of the assessed variables 3 h after thawing after the increase of THI during spermatogenesis in autumn. Remarkably, older bulls were more sensitive to THI at spermatogenesis compared with semen collection, showing up to a 3.8 times higher negative effect on frozen sperm quality. However, an elevated THI at semen collection produced a tendency toward decreased 56-d nonreturn rates as the age of the bull increased. Although this decrease was up to 4%, rising temperatures may still cause important economic losses in the future. For the first time, the present study confirmed that climate compromises not only sperm quality, but also dairy bull fertility.

Cryptorchidism, gonocyte development, and the risks of germ cell malignancy and infertility: A systematic review

BACKGROUND/AIM

Cryptorchidism, or undescended testis (UDT) occurs in 1%-4% of newborn males and leads to a risk of infertility and testicular malignancy. Recent research suggests that infertility and malignancy in UDT may be caused by abnormal development of the neonatal germ cells, or gonocytes, which normally transform into spermatogonial stem cells (SSC) or undergo apoptosis during minipuberty at 2-6 months in humans (2-6 days in mice). We aimed to identify the current knowledge on how UDT is linked to infertility and malignancy.

METHODS

Here we review the literature from 1995 to the present to assess the possible causes of infertility and malignancy in UDT, from both human studies and animal models.

RESULTS

Both the morphological steps and many of the genes involved in germ cell development are now characterized, but the factors involved in gonocyte transformation and apoptosis in both normal and cryptorchid testes are not fully identified. During minipuberty there is evidence for the hypothalamic-pituitary axis stimulating gonocyte transformation, but without known direct control by LH and androgen, although FSH may have a role. An arrested gonocyte maybe the origin of later malignancy at least in syndromic cryptorchid testes in humans, which is consistent with the recent finding that gonocytes are normally absent in a rodent model of congenital cryptorchidism, where malignancy has not been reported.

CONCLUSION

The results of this review strengthen the view that malignancy and infertility in men with previous UDT may be caused by abnormalities in germ cell development during minipuberty.

TYPE OF STUDY

Systematic review (secondary, filtered) LEVEL OF EVIDENCE: Level I.

Heat stress effects on sheep: Are hair sheep more heat resistant?

Climatic variables can trigger physiological, biochemical, haematological and hormonal alterations that influence the maintenance of homeothermy and can affect production and productivity in sheep. Different mechanisms are responsible for tolerance to heat stress (HS) including coat and skin colour, body size, fat distribution, physiological reactions and not just coat type (hair/wool). This review looks at physical, physiological, molecular and genetic aspects of heat tolerance in sheep and how they affect hair and wool sheep. We propose that it is the adaptation to hot environments and not the type of coat (wool/hair) itself that determines the capacity of the resistance of the animal to HS, due to modifications in essential pathways such as energy metabolism, physiological responses and body size. When studied in similar environments, commercial wool breeds tend to show higher heat stress, but hair breeds tend not to differ from wool breeds that are adapted to hot environments.

Phenotypic Responses to and Genetic Architecture of Sterility Following Exposure to Sub-Lethal Temperature During Development

Thermal tolerance range, based on temperatures that result in incapacitating effects, influences species’ distributions and has been used to predict species’ response to increasing temperature. Reproductive performance may also be negatively affected at less extreme temperatures, but such sublethal heat-induced sterility has been relatively ignored in studies addressing the potential effects of, and ability of species’ to respond to, predicted climate warming. The few studies examining the link between increased temperature and reproductive performance typically focus on adults, although effects can vary between life history stages. Here we assessed how sublethal heat stress during development impacted subsequent adult fertility and its plasticity, both of which can provide the raw material for evolutionary responses to increased temperature. We quantified phenotypic and genetic variation in fertility of Drosophila melanogaster reared at standardized densities in three temperatures (25, 27, and 29°C) from a set of lines of the Drosophila Genetic Reference Panel (DGRP). We found little phenotypic variation at the two lower temperatures with more variation at the highest temperature and for plasticity. Males were more affected than females. Despite reasonably large broad-sense heritabilities, a genome-wide association study found little evidence for additive genetic variance and no genetic variants were robustly linked with reproductive performance at specific temperatures or for phenotypic plasticity. We compared results on heat-induced male sterility with other DGRP results on relevant fitness traits measured after abiotic stress and found an association between male susceptibility to sterility and male lifespan reduction following oxidative stress. Our results suggest that sublethal stress during development has profound negative consequences on male adult reproduction, but despite phenotypic variation in a population for this response, there is limited evolutionary potential, either through adaptation to a specific developmental temperature or plasticity in response to developmental heat-induced sterility.

Effect of green tea extract (Camellia sinensis) on the spermatic parameters of Wistar rats submitted or not to testicular heat shock

The aim of this study was to evaluate the effect of green tea extract (GTE) on the spermatic parameters of Wistar rats, submitted or not to testicular heat shock (HS). For this, 48 animals were treated according to the experimental groups (G1: not exposed to HS and untreated; G2: exposed to HS and untreated; G3: not exposed to HS and treated with GTE; G4: exposed to HS and treated with GTE). Subgroups of rats were euthanized on days 15, 30, and 60 to recover the spermatozoa. The total motility (TM), vigor, spermatic morphology and concentration, mitochondrial membrane potential, plasma membrane integrity, and acrosome integrity (ACi) were analyzed. The TM was higher in G1 and G3 than in G2 and G4 on day 30, and higher in G4 on day 60. The overall means of TM and vigor were higher in G1 and G3 than in G2 and G4, as well as TM on day 60. For the morphology, G2 and G4 were lower than G1 and G3 on day 15, and G4 was lower than G1 and G3 on day 30. Moreover, in G1 and G3 morphology was higher on days 15 and 30, and in G4 it was lower on day 30, with the overall means being higher in G1 and G3 than in G2 and G4, as well as on days 15 and 60 compared to day 30. The overall mean of ACi, on day 30, was lower than on days 15 and 60 for all the groups. Therefore, HS is shown to be widely deleterious to the gametes, and the daily administration of 100 mg/kg green tea extract does not improve the spermatic parameters of Wistar rats, submitted or not to testicular HS, although it leads to better recovery of spermatic motility and morphology at 60 days.