Measuring male infertility: epidemiological aspects

Evidence suggests that human semen quality may have been deteriorating in recent years. Most of the evidence is retrospective, based on analysis of data sets collected for other purposes. Measures of male infertility are needed if we want to monitor the biological capacity for males to reproduce over time or between different populations. We also need these measures in analytical epidemiology if we want to identify risk indicators, risk factors, or even causes of an impaired male fecundity-that is, the male component in the biological ability to reproduce. The most direct evaluation of fecundity is to measure the time it takes to conceive. Since the time of conception may be missed in the case of an early abortion, time to get pregnant is often measured as the time it takes to obtain a conception that survives until a clinically recognized pregnancy or even a pregnancy that ends with a live born child occurs. A prolonged time required to produce pregnancy may therefore be due to a failure to conceive or a failure to maintain a pregnancy until clinical recognition. Studies that focus on quantitative changes in fecundity (that does not cause sterility) should in principle be possible in a pregnancy sample. The most important limitation in fertility studies is that the design requires equal persistency in trying to become pregnant and rather similar fertility desires and family planning methods in the groups to be compared. This design is probably achievable in exposure studies that make comparisons with reasonable comparable groups concerning social conditions and use of contraceptive methods.

Finasteride-associated male infertility

Finasteride is a potent and specific inhibitor of the 5alpha-reductase enzyme in men. Clinical studies have shown that finasteride 1mg/day is effective for promoting hair growth in men with male pattern hair loss. However, there is a concern about the use of finasteride, especially in young fertile patients, because of its action on testosterone metabolism. This paper describes 3 cases of young patients who had very poor seminal quality during finasteride treatment (1 mg/day), and their seminal quality greatly improved after cessation of finasteride treatment. Two of them presented with a left varicocele and the other was obese. We hypothesize that finasteride may not dramatically change the spermatogenesis process in healthy men, but in patients with conditions related to infertility, an amplification of the negative influence of finasteride could occur. Future studies should be done to clarify the extent of the effect of finasteride in patients fertility problems.

Effects of medical therapy, alcohol, smoking, and endocrine disruptors on male infertility

Infertility affects up to 15% of the sexually active population, and in 50% of cases, a male factor is involved, either as a primary problem or in combination with a problem in the female partner. Because many commonly encountered drugs and medications can have a detrimental effect on male fertility, the medical evaluation should include a discussion regarding the use of recreational and illicit drugs, medications, and other substances that may impair fertility. With the knowledge of which drugs and medications may be detrimental to fertility, it may be possible to modify medication regimens or convince a patient to modify habits to decrease adverse effects on fertility and improve the chances of achieving a successful pregnancy. Concern is growing that male sexual development and reproduction have changed for the worse over the past 30 to 50 years. Although some reports find no changes, others suggest that sperm counts appear to be decreasing and that the incidence of developmental abnormalities such as hypospadias and cryptorchidism appears to be increasing, as is the incidence of testicular cancer. These concerns center around the possibility that our environment is contaminated with chemicals - both natural and synthetic - that can interact with the endocrine system.

Genetic male infertility and mutation of CATSPER ion channels.

A clinically significant proportion of couples experience difficulty in conceiving a child. In about half of these cases male infertility is the cause and often genetic factors are involved. Despite advances in clinical diagnostics ∼50% of male infertility cases remain idiopathic. Based on this, further analysis of infertile males is required to identify new genetic factors involved in male infertility. This review focuses on cation channel of sperm (CATSPER)-related male infertility. It is based on PubMed literature searches using the keywords 'CATSPER', 'male infertility', 'male contraception', 'immunocontraception' and 'pharmacologic contraception' (publication dates from January 1979 to December 2009). Previously, contiguous gene deletions including the CATSPER2 gene implicated the sperm-specific CATSPER channel in syndromic male infertility (SMI). Recently, we identified insertion mutations of the CATSPER1 gene in families with recessively inherited nonsyndromic male infertility (NSMI). The CATSPER channel therefore represents a novel human male fertility factor. In this review we summarize the genetic and clinical data showing the role of CATSPER mutation in human forms of NSMI and SMI. In addition, we discuss clinical management and therapeutic options for these patients. Finally, we describe how the CATSPER channel could be used as a target for development of a male contraceptive.

Overexpression of the Matrix Metalloproteinase Matrilysin Results in Premature Mammary Gland Differentiation and Male Infertility

To examine the role of matrilysin (MAT), an epithelial cell-specific matrix metalloproteinase, in the normal development and function of reproductive tissues, we generated transgenic animals that overexpress MAT in several reproductive organs. Three distinct forms of human MAT (wild-type, active, and inactive) were placed under the control of the murine mammary tumor virus promoter/enhancer. Although wild-type, active, and inactive forms of the human MAT protein could be produced in an in vitro culture system, mutations of the MAT cDNA significantly decreased the efficiency with which the MAT protein was produced in vivo. Therefore, animals carrying the wild-type MAT transgene that expressed high levels of human MAT in vivo were further examined. Mammary glands from female transgenic animals were morphologically normal throughout mammary development, but displayed an increased ability to produce β-casein protein in virgin animals. In addition, beginning at approximately 8 mo of age, the testes of male transgenic animals became disorganized with apparent disintegration of interstitial tissue that normally surrounds the seminiferous tubules. The disruption of testis morphology was concurrent with the onset of infertility. These results suggest that overexpression of the matrix-degrading enzyme MAT alters the integrity of the extracellular matrix and thereby induces cellular differentiation and cellular destruction in a tissue-specific manner.

A novel functional role for apolipoprotein B in male infertility in heterozygous apolipoprotein B knockout mice.

Male infertility, affecting as many as 10% of the adult population, is an extremely prevalent disorder. In most cases, the cause of the condition is unknown, and genetic factors that might affect male fertility, other than some sequences on the Y chromosome, have not been identified. We report here that male mice heterozygous for a targeted mutation of the apolipoprotein B (apo B) gene exhibit severely compromised fertility. Sperm from these mice failed to fertilize eggs both in vivo and in vitro. However, these sperm were able to fertilize eggs once the zona pellucida was removed but displayed persistent abnormal binding to the egg after fertilization. In vitro fertilization-related and other experiments revealed reduced sperm motility, survival time, and sperm count also contributed to the infertility phenotype. Recognition of the infertility phenotype led to the identification of apo B mRNA in the testes and epididymides of normal mice, and these transcripts were substantially reduced in the affected animals. Moreover, when the genomic sequence encoding human apo B was introduced into these animals, normal fertility was restored. These findings suggest that this genetic locus may have an important impact on male fertility and identify a previously unrecognized function for apo B.

Targeted gene disruption of Hsp70-2 results in failed meiosis, germ cell apoptosis, and male infertility.

In addition to the five 70-kDa heat shock proteins (HSP70) common to germ cells and somatic tissues of mammals, spermatogenic cells synthesize HSP70-2 during meiosis. To determine if this unique stress protein has a critical role in meiosis, we used gene-targeting techniques to disrupt Hsp70-2 in mice. Male mice homozygous for the mutant allele (Hsp70-2 -/-) did not synthesize HSP70-2, lacked postmeiotic spermatids and mature sperm, and were infertile. However, neither meiosis nor fertility was affected in female Hsp70-2 -/- mice. We previously found that HSP70-2 is associated with synaptonemal complexes in the nucleus of meiotic spermatocytes from mice and hamsters. While synaptonemal complexes assembled in Hsp70-2 -/- spermatocytes, structural abnormalities became apparent in these cells by late prophase, and development rarely progressed to the meiotic divisions. Furthermore, analysis of nuclei and genomic DNA indicated that the failure of meiosis in Hsp70-2 -/- mice was coincident with a dramatic increase in spermatocyte apoptosis. These results suggest that HSP70-2 participates in synaptonemal complex function during meiosis in male germ cells and is linked to mechanisms that inhibit apoptosis.

Detection of testicular cancer in men presenting with infertility

PURPOSE: Infertility is one of the less common presenting features associated with testicular tumors. We evaluated the histologic and biochemical findings, and pregnancy outcome in patients presenting with infertility who were found to have testicular tumors. METHODS: Seven patients with infertility were found to have testicular cancer over a 15-year period. All patients had a testicular ultrasound evaluation. The indications for the ultrasound were testicular pain in 2 patients, suspicious palpable mass in 4, and to rule out the presence of germ cell neoplasia in a patient with carcinoma in situ detected on a previous biopsy. Physical exam, histological findings, hormonal levels, tumor markers, and pregnancy outcome results were recorded from the patients medical charts. RESULTS: Two men had elevated serum follicle stimulant hormone and luteinizing hormone levels, 1 of them had an abnormally low serum testosterone level. Tumor markers were normal in all patients. In 4 patients the tumor was on the right side and in 3 on the left. The histological diagnoses were seminoma (n = 5), Leydig cell tumor (n = 1), and carcinoma in situ (n = 1). Of the 7 patients, 5 underwent adjuvant radiation therapy. Two patients had sperm cryopreserved. Follow up on fertility status was available in 6 cases. One patient has established a pregnancy and 5 did not achieve a pregnancy after treatment for their cancer. CONCLUSIONS: Most of the men who have testicular cancer and male infertility have a seminona. Therefore, men who present with infertility should be thoroughly investigated to rule out such serious, concomitant diseases along with their infertility.

Germ cell-specific targeting of DICER or DGCR8 reveals a novel role for endo-siRNAs in the progression of mammalian spermatogenesis and male fertility.

Small non-coding RNAs act as critical regulators of gene expression and are essential for male germ cell development and spermatogenesis. Previously, we showed that germ cell-specific inactivation of Dicer1, an endonuclease essential for the biogenesis of micro-RNAs (miRNAs) and endogenous small interfering RNAs (endo-siRNAs), led to complete male infertility due to alterations in meiotic progression, increased spermatocyte apoptosis and defects in the maturation of spermatozoa. To dissect the distinct physiological roles of miRNAs and endo-siRNAs in spermatogenesis, we compared the testicular phenotype of mice with Dicer1 or Dgcr8 depletion in male germ cells. Dgcr8 mutant mice, which have a defective miRNA pathway while retaining an intact endo-siRNA pathway, were also infertile and displayed similar defects, although less severe, to Dicer1 mutant mice. These included cumulative defects in meiotic and haploid phases of spermatogenesis, resulting in oligo-, terato-, and azoospermia. In addition, we found by RNA sequencing of purified spermatocytes that inactivation of Dicer1 and the resulting absence of miRNAs affected the fine tuning of protein-coding gene expression by increasing low level gene expression. Overall, these results emphasize the essential role of miRNAs in the progression of spermatogenesis, but also indicate a role for endo-siRNAs in this process.

Could zinc prevent reproductive alterations caused by cigarette smoke in male rats?

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The effects of male age on sperm DNA damage in an infertile population

The objective was to investigate the influence of age on sperm DNA damage. Semen samples were collected from 508 men in an unselected group of couples attending infertility investigation and treatment. DNA fragmentation in spermatozoa was measured by TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick-end labelling (TUNEL) assay; at least 200 spermatozoa in randomly selected areas of microscope slides were evaluated using a fluorescent microscope and the percentage of TUNEL positive spermatozoa was determined. The number of cells with red fluorescence (TUNEL positive) was expressed as a percentage of the total sample [DNA fragmentation index (DFI)]. Age was treated as a continuous variable for regression and correlation analysis. The following male age groups were used: Group I: ≤35 years, Group II: 36-39 years, and Group III: ≥40 years. DFI was significantly lower in Group I than in Group II (P = 0.034) or III (P = 0.022). There was no difference in DFI between Groups II and III. In addition, regression analysis demonstrated a significant increase in sperm DFI with age (P = 0.02). TUNEL assay clearly demonstrates an increase in sperm DNA damage with age. © 2007 Published by Reproductive Healthcare Ltd.

The horse genome project - sequence based insights into male reproductive mechanisms

The growing knowledge on physiology, cell biology and biochemistry of the reproductive organs has provided many insights into molecular mechanisms that are required for successful reproduction. Research directed at the investigation of reproduction physiology in domestic animals was hampered in the past by a lack of species-specific genomic information. The genome sequences of dog, cattle and horse have become publicly available in 2005, 2006 and 2007 respectively. Although the gene content of mammalian genomes is generally very similar, genes involved in reproduction tend to be less conserved than the average mammalian gene. The availability of genome sequences provides a valuable resource to check whether any protein that may be known from human or mouse research is present in cattle and/or horse as well. Currently there are more than 200 genes known that are involved in the production of fertile sperm cells. Great progress has been made in the understanding of genetic aberrations that lead to male infertility. Additionally, the first genetic mechanisms are being discovered that contribute to the quantitative variation of fertility traits in fertile male animals. Here, I will review some selected aspects of genetic research in male fertility and offer some perspectives for the use of genomic sequence information.