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Rodríguez H, Arriaza C, Sarabia L, Espinoza-Navarro O. Anatomical and physiological adaptation of the scrotal artery with muscular reinforcement in the middle layer and connective reinforcement of the adventitia. Microsc Res Tech 2024; 87:403-407. [PMID: 37877624 DOI: 10.1002/jemt.24440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 09/25/2023] [Accepted: 10/05/2023] [Indexed: 10/26/2023]
Abstract
The histology of blood vessels shows they are structured in three layers or tunics: tunica intima, which includes the internal limiting lamina with high elastin content; tunica media of smooth muscles fibers of circular disposition, which includes the external limiting lamina; and tunica adventitia of connective tissue. The vascular system is essential in regulating body temperature, especially in the scrotum and testis. This study aimed to analyze the histology of the scrotal arteries and their possible relationship to testicular temperature homeostasis. This study used scrotal samples from human adults, anonymized and obtained from the University of Chile's teaching bank. The control group corresponds to an arteriole of muscle tissue. The results show that the middle layer of the scrotal artery is made up of smooth muscle fibers distributed in two layers: a longitudinal inner sublayer and a circular outer sublayer, different from the findings in muscle tissue arteries, with a single, circularly arranged muscle layer. This arrangement could be related to testicular temperature homeostasis by reducing the temperature of the testis and seminiferous tubules. The results described in this work suggest that these anatomical adaptations may be very significant in the face of the constant increase in global temperature. Further and better research is required to understand the mechanisms of thermoregulation in human reproduction and the histological particularities of the tissues that form the scrotum. RESEARCH HIGHLIGHTS: The human scrotal artery has a histological composition adapted for regulation of testicular temperature. The muscular double middle layer of the scrotal artery retains intravascular temperature.
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Affiliation(s)
- Héctor Rodríguez
- Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Facultad de Medicina, Universidad de Atacama, Copiapó, Chile
| | - Camilo Arriaza
- Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Luis Sarabia
- Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Omar Espinoza-Navarro
- Departamento de Biología, Facultad de Ciencias, Universidad de Tarapacá, Arica, Chile
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2
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Ben Moula A, Moussafir Z, Hamidallah N, El Amiri B. Heat stress and ram semen production and preservation: Exploring impacts and effective strategies. J Therm Biol 2024; 119:103794. [PMID: 38330855 DOI: 10.1016/j.jtherbio.2024.103794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 01/12/2024] [Accepted: 01/12/2024] [Indexed: 02/10/2024]
Abstract
As global warming persists, heat stress (HS) continues to affect animals, particularly those raised in extensive systems such as sheep. As a result, there is a growing body of research investigating the physiological and biological consequences of HS on these animals. Recent studies have specifically examined the effects of climate change, global warming, and HS on gametes. Heat stress has been shown to affect ram semen production, resulting in decreased sperm quality and volume in both fresh and stored samples. This is attributed to the effect of heat on hormone production in the testicles, which is critical for successful spermatogenesis. Such effects can have significant consequences on the fertility of female sheep, which could affect the farmers' revenue. Therefore, farmers and researchers are utilizing various strategies and laboratory techniques to mitigate these negative effects. This review aims to comprehensively evaluate the impact of HS on ram semen production and conservation and analyze the different mitigation strategies at various levels, including management and nutritional interventions. The findings of this review will serve as a critical foundation for the development of targeted interventions and sustainable practices in sheep farming, ensuring resilient and profitable operations in the face of ongoing global climate challenges.
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Affiliation(s)
- Anass Ben Moula
- Department of Life Sciences, Polydisciplinary Faculty of Larache, Abdelmalek Essaadi University, 745 BP, 92004, Larache, Morocco.
| | - Zineb Moussafir
- Faculty of Science and Technology, Errachidia, Moulay Ismail University, Meknes, Morocco
| | - Naima Hamidallah
- Faculty of Science and Technology, Hassan 1 University, BP 577, 26000, Settat, Morocco
| | - Bouchra El Amiri
- INRA-Regional Center for Agronomic Research of Settat, BP589, Settat, Morocco; African Sustainable Agriculture Research Institute (ASARI), Mohammed VI Polytechnic University (UM6P), 70000, Laayoune, Morocco
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Shahat AM, Thundathil JC, Kastelic JP. Melatonin improves post-thaw sperm quality after mild testicular heat stress in rams. Reprod Domest Anim 2023; 58:423-430. [PMID: 36510757 DOI: 10.1111/rda.14302] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Revised: 11/30/2022] [Accepted: 12/01/2022] [Indexed: 12/15/2022]
Abstract
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.
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Affiliation(s)
- Abdallah M Shahat
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Theriogenology, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt
| | - Jacob C Thundathil
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada
| | - John P Kastelic
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada
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Samir H, ElSayed MI, Radwan F, Hedia M, Hendawy H, Hendawy AO, Elbadawy M, Watanabe G. An updated insight on testicular hemodynamics: Environmental, physiological, and technical perspectives in farm and companion animals. Vet Res Commun 2022; 47:323-345. [DOI: 10.1007/s11259-022-10022-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 10/13/2022] [Indexed: 11/19/2022]
Abstract
Abstract
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.
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Gao Y, Wang C, Wang K, He C, Hu K, Liang M. The effects and molecular mechanism of heat stress on spermatogenesis and the mitigation measures. Syst Biol Reprod Med 2022; 68:331-347. [PMID: 35722894 DOI: 10.1080/19396368.2022.2074325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Under normal conditions, to achieve optimal spermatogenesis, the temperature of the testes should be 2-6 °C lower than body temperature. Cryptorchidism is one of the common pathogenic factors of male infertility. The increase of testicular temperature in male cryptorchidism patients leads to the disorder of body regulation and balance, induces the oxidative stress response of germ cells, destroys the integrity of sperm DNA, yields morphologically abnormal sperm, and leads to excessive apoptosis of germ cells. These physiological changes in the body can reduce sperm fertility and lead to male infertility. This paper describes the factors causing testicular heat stress, including lifestyle and behavioral factors, occupational and environmental factors (external factors), and clinical factors caused by pathological conditions (internal factors). Studies have shown that wearing tight pants or an inappropriate posture when sitting for a long time in daily life, and an increase in ambient temperature caused by different seasons or in different areas, can cause an increase in testicular temperature, induces testicular oxidative stress response, and reduce male fertility. The occurrence of cryptorchidism causes pathological changes within the testis and sperm, such as increased germ cell apoptosis, DNA damage in sperm cells, changes in gene expression, increase in chromosome aneuploidy, and changes in Na+/K+-ATPase activity, etc. At the end of the article, we list some substances that can relieve oxidative stress in tissues, such as trigonelline, melatonin, R. apetalus, and angelica powder. These substances can protect testicular tissue and relieve the damage caused by excessive oxidative stress.
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Affiliation(s)
- Yuanyuan Gao
- School of Life Science, Bengbu Medical College, Bengbu, People's Republic of China
| | - Chen Wang
- School of Life Science, Bengbu Medical College, Bengbu, People's Republic of China
| | - Kaixian Wang
- School of Life Science, Bengbu Medical College, Bengbu, People's Republic of China
| | - Chaofan He
- School of Life Science, Bengbu Medical College, Bengbu, People's Republic of China
| | - Ke Hu
- School of Life Science, Bengbu Medical College, Bengbu, People's Republic of China
| | - Meng Liang
- School of Life Science, Bengbu Medical College, Bengbu, People's Republic of China
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Shahat AM, Thundathil JC, Kastelic JP. Melatonin improves testicular hemodynamics and sperm quality in rams subjected to mild testicular heat stress. Theriogenology 2022; 188:163-169. [DOI: 10.1016/j.theriogenology.2022.05.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 05/29/2022] [Accepted: 05/30/2022] [Indexed: 10/18/2022]
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Impact of Heat Stress on Bovine Sperm Quality and Competence. Animals (Basel) 2022; 12:ani12080975. [PMID: 35454222 PMCID: PMC9027525 DOI: 10.3390/ani12080975] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 03/28/2022] [Accepted: 04/07/2022] [Indexed: 02/04/2023] Open
Abstract
Global warming has negatively influenced animal production performance, in addition to animal well-being and welfare, consequently impairing the economic sustainability of the livestock industry. Heat stress impact on male fertility is complex and multifactorial, with the fertilizing ability of spermatozoa affected by several pathways. Among the most significative changes are the increase in and accumulation of reactive oxygen species (ROS) causing lipid peroxidation and motility impairment. The exposure of DNA during the cell division of spermatogenesis makes it vulnerable to both ROS and apoptotic enzymes, while the subsequent post-meiotic DNA condensation makes restoration impossible, harming later embryonic development. Mitochondria are also susceptible to the loss of membrane potential and electron leakage during oxidative phosphorylation, lowering their energy production capacity under heat stress. Although cells are equipped with defense mechanisms against heat stress, heat insults that are too intense lead to cell death. Heat shock proteins (HSP) belong to a thermostable and stress-induced protein family, which eliminate protein clusters and are essential to proteostasis under heat stress. This review focuses on effects of heat stress on sperm quality and on the mechanisms leading to defective sperm under heat stress.
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El-Sherbiny HR, El-Shalofy AS, Samir H. Exogenous L-carnitine Administration Ameliorates the Adverse Effects of Heat Stress on Testicular Hemodynamics, Echotexture, and Total Antioxidant Capacity in Rams. Front Vet Sci 2022; 9:860771. [PMID: 35464382 PMCID: PMC9019560 DOI: 10.3389/fvets.2022.860771] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Accepted: 03/03/2022] [Indexed: 12/23/2022] Open
Abstract
Heat stress (HS) diminishes the testicular antioxidant defense systems, which adversely affect the testicular blood perfusion. Improving the testicular hemodynamics during HS conditions is of a great impact on the whole reproductive performance in rams. This study aimed to evaluate the ameliorative effects of L-carnitine (LC) on the testicular blood flow and echotextures and also on the total antioxidants (TAC) and nitric oxide (NO) concentrations in the serum during HS conditions in rams. Testicular blood flow was evaluated through scanning of the supra-testicular artery (STA) spectral patterns through pulsed Doppler ultrasonography [peak systolic velocity (PSV), end-diastolic velocity (EDV), time average maximum velocity (TAMAX), resistive index (RI), and pulsatility index (PI)], while the echotexture assessment of testicular parenchyma was performed by a computerized software program. Moreover, TAC and NO concentrations were assayed colorimetrically using the spectrophotometer. There were significant decreases (P < 0.05) in values of PSV at 48 and 168 h (23.45 ± 0.39 and 23.37 ± 1.41 cm/s, respectively), and TAMAX at 1, 48, and 168 h (17.65 ± 0.95, 17.5 ± 0.13, and 16.9 ± 1.05 cm/s, respectively) after LC administration compared to just before administration (31.92 ± 1.13 and 21.58 ± 0.92 cm/s, respectively). Values of RI and PI of the examined STA significantly decreased, especially at 1 h for RI (0.45 ± 0.02) and 1 and 48 h for PI (0.66 ± 0.06 and 0.65 ± 0.05, respectively) after LC treatment to 0 h (0.55 ± 0.03 and 0.84 ± 0.06, respectively). The EDV values did not show any significant (P < 0.05) changes in all the experimental time points. There were significant (P < 0.05) increases in the values of pixel intensity of the testicular parenchyma, especially at 1 and 168 h (78.71 ± 2.50 and 88.56 ± 4.10, respectively) after LC administration, compared to just before administration (69.40 ± 4.75). Serum NO levels tend to increase after LC administration (P = 0.07) concerning just before administration. While TAC values showed significant gradual increase and reached the highest values at 168 h (2.75 ± 0.58 mM/l) after LC administration, compared to 0 h (1.12 ± 0.05 mM/l). In conclusion, exogenous LC administration ameliorates testicular hemodynamic disruptions, as measured by spectral Doppler ultrasonography, via augmentation of the rams' total antioxidant capacity under HS conditions.
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Shahat AM, Thundathil JC, Kastelic JP. AMelatonin or arginine in semen extender mitigate reductions in quality of frozen-thawed sperm from heat-stressed rams. Anim Reprod Sci 2022; 238:106934. [DOI: 10.1016/j.anireprosci.2022.106934] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 01/11/2022] [Accepted: 01/21/2022] [Indexed: 12/16/2022]
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Verón GL, Tissera AD, Bello R, Estofan GM, Hernández M, Beltramone F, Molina RI, Vazquez-Levin MH. Association between meteorological variables and semen quality: a retrospective study. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2021; 65:1399-1414. [PMID: 33834291 DOI: 10.1007/s00484-021-02112-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 02/23/2021] [Accepted: 03/03/2021] [Indexed: 06/12/2023]
Abstract
Spermatogenesis is a temperature-dependent process, and high summer temperatures have been linked to lower sperm concentration and count. However, reports describing the association between other meteorological variables and semen quality are scarce. This study evaluated the association between semen quality and temperature, humidity, pressure, apparent temperature (AT), temperature-humidity index (THI), simplified wet-bulb global temperature (sWBGT), and sunshine duration. Semen samples were obtained at the Laboratorio de Andrología y Reproducción (LAR, Argentina), from men undergoing routine andrology examination (n=11657) and computer-assisted sperm analysis (n=4705) following WHO 2010 criteria. Meteorological variables readings were obtained from the Sistema Meteorológico Nacional. Sperm quality parameters were negatively affected in summer when compared to winter. Additionally, there was a significant decrease in sperm kinematics between winter and spring. Branch and bound variable selection followed by multiple regression analysis revealed a significant association between semen quality and meteorological variables. Specifically, changes in sunshine duration and humidity reinforced the prognosis of semen quality. Highest/lowest sunshine duration and humidity quantiles resulted in decreased sperm concentration, count, motility, vitality and membrane competence, nuclear maturity, and sperm kinematics associated to highest sunshine duration and lowest humidity. Findings from this report highlight the relevance of environmental studies for predicting alterations in male reproductive health associated to variations in meteorological variables, especially considering the current climate changes around the planet due to global warming and its consequences for human health.
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Affiliation(s)
- Gustavo Luis Verón
- Laboratorio de Estudios de Interacción Celular en Reproducción y Cáncer, Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (National Research Council of Argentina; CONICET)-Fundación IBYME (FIBYME), Vuelta de Obligado 2490, C1428ADN, Ciudad Autónoma de Buenos Aires, Argentina
| | | | - Ricardo Bello
- Departamento de Metodología, Estadística y Matemática, Universidad de Tres de Febrero, Sáenz Peña, Buenos Aires, Argentina
| | | | - Mariana Hernández
- Centro Integral de Ginecología, Obstetricia y Reproducción (CIGOR), Córdoba, Argentina
| | - Fernando Beltramone
- Centro Integral de Ginecología, Obstetricia y Reproducción (CIGOR), Córdoba, Argentina
| | | | - Mónica Hebe Vazquez-Levin
- Laboratorio de Estudios de Interacción Celular en Reproducción y Cáncer, Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (National Research Council of Argentina; CONICET)-Fundación IBYME (FIBYME), Vuelta de Obligado 2490, C1428ADN, Ciudad Autónoma de Buenos Aires, Argentina.
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Perry VEA. The Role of Sperm Morphology Standards in the Laboratory Assessment of Bull Fertility in Australia. Front Vet Sci 2021; 8:672058. [PMID: 34124227 PMCID: PMC8187580 DOI: 10.3389/fvets.2021.672058] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 04/22/2021] [Indexed: 11/13/2022] Open
Abstract
The lack of standardization in the laboratory assessment of semen questions the reliability of semen analysis, and makes meaningful interpretation of these evaluations impossible. We herein describe a standardization program for morphology assessment currently in place in Australia and outline the methods used, both for the categorization of the abnormalities, including newly described abnormalities, and those that permit standardized microscopic assessment between laboratories.
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Affiliation(s)
- V E A Perry
- Queensland Sperm Morphology Laboratory, Ruminant Reproduction Research Centre, Goondiwindi, QLD, Australia.,School of Veterinary Science, University of Queensland, Brisbane QLD, Australia.,Robinson Research Institute, University of Adelaide, Adelaide, SA, Australia
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Aldahhan RA, Stanton PG. Heat stress response of somatic cells in the testis. Mol Cell Endocrinol 2021; 527:111216. [PMID: 33639219 DOI: 10.1016/j.mce.2021.111216] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 11/30/2020] [Accepted: 02/15/2021] [Indexed: 02/06/2023]
Abstract
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.
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Affiliation(s)
- Rashid A Aldahhan
- Department of Anatomy, College of Medicine, Imam Abdulrahman Bin Faisal University, P.O. Box 2114, Dammam, 31541, Saudi Arabia.
| | - Peter G Stanton
- Centre for Reproductive Health, Hudson Institute of Medical Research, Clayton, Victoria, Australia; Department of Molecular and Translational Sciences, Monash University, Clayton, Victoria, Australia
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Amelioration of heat stress-induced damage to testes and sperm quality. Theriogenology 2020; 158:84-96. [PMID: 32947064 DOI: 10.1016/j.theriogenology.2020.08.034] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 08/26/2020] [Accepted: 08/28/2020] [Indexed: 12/19/2022]
Abstract
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).
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