Update on COVID-19 and histophysiology of the male reproductive system / Actualización sobre COVID-19 e histofisiología del sistema reproductor masculino

RESUMEN: La reciente pandemia de la COVID-19 ha sacudido a la sociedad teniendo una importante repercusión en el campo de la salud y de la investigación. Dada su relevancia, se han llevado a cabo estudios sobre los efectos del SARS-CoV-2 en la fisiología humana. En concreto, sobre la posible presencia y transmisión del virus a través del sistema reproductor masculino y su posible efecto en el éxito reproductivo. Conocer si la presencia del virus altera los órganos responsables del desarrollo y maduración de las células de la serie espermatogénica podría revelarnos su implicación en la calidad seminal. Por ello, nos planteamos esta revisión, con el fin de analizar las principales evidencias científicas sobre los efectos del SARS-CoV-2 en la histofisiología del sistema reproductor masculino y sobre la capacidad fecundante de los espermatozoides.

SUMMARY: The recent COVID-19 pandemic has shaken up society, having a significant impact on the field of health and research. Given its relevance, studies have been performed on the effects of SARS-CoV-2 on human physiology. In particular, the possible presence and transmission of the virus through the male reproductive system could affect reproductive success. Knowing if the presence of the virus disrupts the organs responsible for the development and maturation of the cell lines involved in spermatogenesis could reveal its implications in sperm quality. For that reason, we proposed this review, in order to analyze the main scientific evidence on the effects of SARS-CoV-2 on the histophysiology of the male reproductive system and sperm fertilizing capacity.

Effect of COVID-19 on Male Reproductive System - A Systematic Review.

Background: Angiotensin-converting enzyme II (ACE2), a receptor for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) to enter host cells, is widely expressed in testes and prostate tissues. The testis and prostate produce semen. At present, there are contradictory reports about whether SARS-CoV-2 can exist in the semen of infected men. Objective: To provide a comprehensive overview of the topic of whether COVID-19 can impact on male reproductive system. Methods: We reviewed the relevant publications on the possible impact of Coronavirus Disease 2019 (COVID-19) on male reproductive system and summarized the latest and most important research results so far. Literature published in English from December 2019 to January 31, 2021 regarding the existence of SARS-CoV-2 in semen, testis, and prostatic fluid and the effects of COVID-19 on male reproductive were included. Results: We identified 28 related studies, only one of which reported the presence of SARS-CoV-2 in semen. The study found that the semen quality of patients with moderate infection was lower than that of patients with mild infection and healthy controls. The impaired semen quality may be related to fever and inflammation. Pathological analysis of the testis/epididymis showed that SARS-CoV-2 viral particles were positive in 10 testicular samples, and the spermatogenic function of the testis was impaired. All 94 expressed prostatic secretion (EPS) samples were negative for SARS-CoV-2 RNA. Conclusion: The likelihood of SARS-CoV-2 in the semen of COVID-19 patients is very small, and semen should rarely be regarded as a carrier of SARS-CoV-2 genetic material. However, COVID-19 may cause testicular spermatogenic dysfunction via immune or inflammatory reactions. Long-term follow-up is needed for COVID-19 male patients and fetuses conceived during the father's infection period.

The probable destructive mechanisms behind COVID-19 on male reproduction system and fertility.

PURPOSE: The present study aims to summarize the current understanding of probable mechanisms and claims of adverse effects of SARS-CoV-2 on male fertility potential. METHODS: Our search was including original articles, reviews, guidelines, letters to the editor, comments on guidelines, and editorials, regarding the male reproductive system. We used the words SARS-CoV-2, coronavirus, severe acute respiratory syndrome coronavirus 2, "2019 ncov," testis, sperm, male factor infertility, fertility treatment, semen, assisted reproductive technology (ART), sexual transmission, and ACE2. RESULTS: Data showed coronavirus affects men more than women because of more expression of 2019 nCoV receptors (ACE2 and TMPRSS2) in testicular cells. Also, "Bioinformatics Analysis" suggests that sperm production may be damaged, since "Pseudo Time Analysis" has shown disruption in spermatogenesis. "Gene Ontology" (GO) showed an increase in viral reproduction and a decrease in sperm production-related terms. Recently, SARS-COV-2 mRNA and protein were detected in the semen of patients that had recovered from SARS-CoV-2 infection. Therefore, the probable disruption of blood-testis barrier (BTB) in febrile diseases is suspected in the acute phase of the disease enabling viral entry into the testes. Not only is spermatogenesis disturbed, but also disturbs gonadotropin, androgens, and testosterone secretion during SARS-CoV-2 infection. No sexual transmission has been reported yet; however, detection of the virus in semen still makes the sexual transmission an open question. CONCLUSION: There is a concern that male fertility may be disturbed after the SARS-CoV-2 infection. Therefore, follow-up of the reproductive functions and male fertility may be necessary in recovered cases, especially in aged men.

The other side of COVID-19 pandemic: Effects on male fertility.

The outbreak of novel coronavirus disease 2019 (COVID-19) has become a major pandemic threat worldwide. According to the existing clinical data, this virus not only causes respiratory diseases and affects the lungs but also induces histopathological or functional changes in various organs like the testis and also the male genital tract. The renin-angiotensin system (RAS), also ACE 2 and TMPRSS2 play an important role in the cellular entry for SARS-CoV-2. Because the male genital system presents high ACE 2 expression, the importance of this pathway increases in COVID-19 cases. As the COVID-19 pandemic has affected the male genital system in direct or indirect ways and showed a negative impact on male reproduction, this paper focuses on the possible mechanisms underlying the damage caused by COVID-19 to the testis and also other components of the male genital tract.

Physiological implications of COVID-19 in reproduction: angiotensin-converting enzyme 2 a key player.

The COVID-19 outbreak, caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), was first identified in China, and it has quickly become a global threat to public health due to its rapid rate of transmission and fatalities. Angiotensin-converting enzyme 2 (ACE2) has been identified as a receptor that mediates the entry of SARS-CoV-2 into human cells, as in the case of severe acute respiratory syndrome coronavirus (SARS-CoV). Several studies have reported that ACE2 expression is higher in Leydig, Sertoli and seminiferous ductal cells of males, as well as in ovarian follicle cells of females, suggesting possible potential pathogenicity of the coronavirus in the reproductive system. Higher ACE2 expression in the human placenta and reports of vertical transmission of SARS-CoV-2 among clinical cases have increased the relevance of further studies in this area. This review focuses on the interaction between SARS-CoV-2 and the ACE2 receptor and speculates on the mechanistic interplay in association with male and female reproductive physiology. In addition, based on the available literature, we discuss the alleged sex differences in terms of the infectivity of SARS-CoV-2, which is claimed greater among males, and further explore the physiological role of ACE2 and 17ß-oestradiol for the same.

Review of COVID-19 and male genital tract.

COVID-19 pandemic leads to health challenges globally, and its diverse aspects need to be uncovered. Multi-organ injuries have been reported by describing potential SARS-CoV-2 entrance routes: ACE2 and TMPRSS2. Since these cell surface receptors' expression has been disclosed within the male reproductive system, its susceptibility to being infected by SARS-CoV-2 has been summarised through this literature review. Expression of ACE2 and TMPRSS2 at RNA or protein level has been reported across various investigations indicates that the male genitalia potentially is vulnerable to SARS-CoV-2 infection. Presence of SARS-CoV-2 within semen samples and following direct viral damage, secondary inflammatory response causing orchitis or testicular discomfort and finally the amount of viral load leading testicular damage and immune response activation are among probable underlying mechanisms. Therefore, genital examination and laboratory tests should be considered to address the male reproductive tract complications and fertility issues.

COVID-19 Infection in the Human Reproductive Tract of Men and Nonpregnant Women.

SARS-CoV-2 is an enveloped non-segmented positive-sense RNA virus, classified as a beta coronavirus, responsible for the COVID-19 pandemic. Angiotensin-converting enzyme 2 (ACE2), reported as a SARS-CoV-2 receptor, is expressed in different human tissues (lung, intestine, and kidney) and in the testis, ovaries, uterus, and vagina. This suggests a potential risk to the human reproductive tract in COVID-19 patients. In addition, SARS-CoV-2 RNA has been detected in the blood, urine, facial/anal swabs, semen, and vaginal secretion, suggesting other potential means of transmission. However, little has been reported about SARS-CoV-2 infection in the male and nonpregnant female reproductive tracts, which may provide direct evidence on sexual transmission and fertility problems. Therefore, we focused this narrative review mainly on the distribution of ACE2 and SARS-CoV-2 positivity in the male and nonpregnant female reproductive tracts, providing an overview of the potential threat of COVID-19 to reproductive health and sexual transmission.

The impact of SARS-CoV-2 and COVID-19 on male reproduction and men's health.

Many couples initially deferred attempts at pregnancy or delayed fertility care due to concerns about coronavirus disease 2019 (COVID-19). One significant fear during the COVID-19 pandemic was the possibility of sexual transmission. Many couples have since resumed fertility care while accepting the various uncertainties associated with severe acute respiratory syndrome coronavirus 2, including the evolving knowledge related to male reproductive health. Significant research has been conducted exploring viral shedding, tropism, sexual transmission, the impact of male reproductive hormones, and possible implications to semen quality. However, to date, limited definitive evidence exists regarding many of these aspects, creating a challenging landscape for both patients and physicians to obtain and provide the best clinical care. This review provides a comprehensive assessment of the evolving literature concerning COVID-19 and male sexual and reproductive health, and guidance for patient counseling.

The hypothesis that SARS-CoV-2 affects male reproductive ability by regulating autophagy.

The outbreak of CoronaVirus Disease19 (COVID19) in December 2019 posed a serious threat to public safety, and its rapid spread caused a global health emergency. Clinical data show that in addition to respiratory system damage, some male patients with COVID-19 are also accompanied by abnormal renal function and even renal damage. As the main receptor of syndrome coronavirus 2 (SARS-CoV-2), angiotensin converting enzyme 2 (ACE2) is also found to be highly expressed not only in respiratory mucosa and alveolar epithelial cells, but also in renal tubule cells, testicular Leydig cells and seminiferous tubule cells. This suggests that SARS-CoV-2 has the possibility of infecting the male reproductive system, and the recent detection of SARS-CoV-2 in the patient's semen further confirms this theory. In previous studies, it has been found that ACE2 has the ability to regulate autophagy. Not only that, recent studies have also found that SARS-CoV-2 infection can also lead to a reduction in autophagy. All of these associate SARS-CoV-2 with autophagy. Furthermore, autophagy has been shown to have an effect on male reproduction in many studies. Based on these, we propose the hypothesis that SARS-CoV-2 affects male reproductive function by regulating autophagy. This hypothesis may provide a new idea for future treatment of COVID-19 male patients with reproductive function injury, and it can also prompt medical staff and patients to consciously check their reproductive function.