Transcriptomic signatures for human male infertility.

Introduction: Male infertility is a common, complex disorder. A better understanding of pathogenesis and etiology is needed for timely diagnosis and treatment. The aim of this study, therefore, was to identify genes involved in the pathogenesis of idiopathic male infertility based on data from transcriptomic level supported with data from genomic level. Materials and methods: First, we performed whole gene expression analysis in 20 testis biopsy samples of patients with severely impaired (10) and normal spermatogenesis (10). Further, we have performed systematic review of comparable male infertility studies and overlapped the most significantly expressed genes identified in our study with the most differentially expressed genes from selected studies. Gene Ontology analysis and KEGG functional enrichment have been performed with Enrichr analysis tool. Additionally, we have overlapped these genes with the genes where rare variants have been identified previously. Results: In 10 patients with severely impaired spermatogenesis and 10 controls, we identified more than 1,800 differentially expressed genes (p < 0.001). With the systematic review of three previously performed microarray studies that have met inclusion criteria we identified 257 overlapped differentialy expressed genes (144 downregulated and 113 upregulated). Intersection of genes from transcriptomic studies with genes with identified rare variants revealed a total of 7 genes linked with male infertility phenotype (CYP11A1, CYP17A1, RSPH3, TSGA10, AKAP4, CCIN, NDNF). Conclusion: Our comprehensive study highlighted the role of four genes in pathogenesis of male infertility and provided supporting evidence for three promising candidate genes which dysfunction may result in a male infertility disorder.

De novo mutations in idiopathic male infertility-A pilot study.

STUDY QUESTION: Are de novo mutations in the human genome associated with male infertility? SUMMARY ANSWER: We identified de novo mutations in five candidate genes: SEMA5A, NEURL4, BRD2, CD1D, and CD63. WHAT IS KNOWN ALREADY: Epidemiological and genetic studies have consistently indicated contribution of genetic factors to the etiology of male infertility, suggesting that more than 1500 genes are involved in spermatogenesis. STUDY DESIGN, SIZE, DURATION: First, we searched for de novo mutations in patients with idiopathic azoospermia with whole-exome sequencing (WES). To evaluate the potential functional impact of de novo identified mutations, we analyzed their expression differences on independent testis samples with normal and impaired spermatogenesis. In the next step, we tested additional group of azoospermic patients for mutations in identified genes with de novo mutations. In addition to the analysis of de novo mutations in patients with idiopathic azoospermia, we considered other models of inheritance and searched for candidate genes harboring rare maternally inherited variants and biallelic autosomal and X-chromosome hemizygous variants. PARTICIPANTS/MATERIALS, SETTING, METHODS: We performed WES in 13 infertile males with idiopathic azoospermia and their parents. Potential functional impact of de novo identified mutations was evaluated by global gene expression profiling on 20 independent testis samples. To replicate the results, we performed WES in further 16 independent azoospermic males, which were screened for the variants in the same genes. Library preparation was performed with Nextera Coding Exome Capture Kit (Illumina), with subsequent sequencing on Illumina HiSeq 2500 platform. MAIN RESULTS AND THE ROLE OF CHANCE: We identified 11 de novo mutations in 10 genes of which 5 were considered potentially associated with azoospermia: SEMA5A, NEURL4, BRD2, CD1D, and CD63. All candidate genes showed significant differential expression in testis samples composed of patients with severely impaired and normal spermatogenesis. Additionally, we identified rare, potentially pathogenic mutations in the genes previously implicated in male infertility-a maternally inherited heterozygous frameshift variant in FKBPL gene and inframe deletion in UPF2 gene, homozygous frameshift variant in CLCA4 gene, and a heterozygous missense variant NR0B1 gene, which represent promising candidates for further clinical implication. LIMITATIONS OF THE STUDY, REASONS FOR CAUTION: We provided limited functional support for involvement of de novo identified genes in pathogenesis of male infertility, based on expression analysis. Additionally, the sample size was limited. WIDER IMPLICATIONS OF THE FINDINGS: We provide support that de novo mutations might contribute to male infertility and propose five genes as potentially implicated in its pathogenesis.

Magnetic-activated cell sorting of non-apoptotic spermatozoa improves the quality of embryos according to female age: a prospective sibling oocyte study.

PURPOSE: The main aim of our study was to evaluate the benefit of the use of non-apoptotic spermatozoa selected by magnetic-activated cell sorting (MACS) for ICSI procedures for couples in which the women had good prognoses and the male factor of infertility was teratozoospermia. METHODS: Twenty-six couples were treated with ICSI after MACS selection of non-apoptotic spermatozoa following a sibling oocyte approach. Half of the oocytes were microinjected with conventionally prepared spermatozoa, and the other half were microinjected with non-apoptotic, MACS-selected spermatozoa. To assess the influence of MACS selection of spermatozoa on the outcomes of the ICSI cycles, the fertilization, embryo quality, pregnancy, and delivery rates were evaluated and compared between the sibling oocyte groups. RESULTS: When subpopulations of couples according to female age were analyzed, a significant difference in quality of blastocyst was observed. More precisely, in a group that was treated with MACS-ICSI, a higher percentage of good quality blastocysts was found among women older than 30 years (75.0 vs. 33.3%; P = 0.028), while there was no difference among younger women. If all included couples were compared regardless of age, no significant difference was observed in the outcome of the ICSI/MACS-ICSI cycles in terms of oocytes and embryos. Additionally, after the ICSI and MACS-ICSI procedures, the morphologies of the prepared spermatozoa were compared. Results showed that the overall percentage of morphologically normal spermatozoa did not differ significantly between the ICSI and MACS-ICSI procedures. However, detailed analyses of the morphologically abnormal spermatozoa revealed significantly more spermatozoa with abnormal tails after MACS-ICSI procedure, which may be potential consequence of the selection procedure. Moreover, the trends towards less spermatozoa with abnormal heads and towards more spermatozoa with abnormal necks and midpieces after MACS-ICSI procedure were revealed, although the differences were not significant. CONCLUSIONS: Couples dealing with male infertility due to teratozoospermia can benefit from MACS selection of spermatozoa with higher percentage of good quality blastocysts but only when the woman is older than 30 years.

Adapted methods for scanning electron microscopy (SEM) in assessment of human sperm morphology.

Infertility is a widespread problem, and in some cases, the routine basic semen analysis is not sufficient to detect the cause of male infertility. The use of the scanning electron microscope (SEM) could provide a detailed insight into spermatozoa morphology, but it requires specific sample preparation techniques. The purpose of this study was to select, adjust, and optimize a method for the preparation of spermatozoa samples prior to SEM analysis, and to establish the protocol required for its use in clinical practice. We examined sperm samples of 50 men. The samples were fixed with modified iso-osmolar aldehyde solution followed by osmium post-fixation. In the first method, dehydration of the cells and subsequent critical point drying (CPD) were performed on a coverslip. In the second method, the samples were dehydrated in centrifuge tubes; hexamethyldisilazane (HMDS) was used as a drying agent instead of CPD, and the samples were air-dried. The third procedure was based on a membrane filter. The samples were dehydrated and dried with HMDS in a Gooch crucible, continuously, without centrifugation or redispersion of the sample. Our results showed that the fixation with modified iso-osmolar aldehyde solution followed by osmium post-fixation, and combined with dehydration and CPD on a coverslip, is the most convenient procedure for SEM sample preparation. In the case of small-size samples or low sperm concentration, dehydration and drying with HMDS on the membrane filter enabled the best reliability, repeatability, and comparability of the results. The presented procedures are suitable for routine use, and they can be applied to confirm as well as to correct a diagnosis.

Sperm DNA fragmentation and mitochondrial membrane potential combined are better for predicting natural conception than standard sperm parameters.

OBJECTIVE: To evaluate whether DNA fragmentation and/or mitochondrial membrane potential (MMP) predict natural conception better than standard sperm parameters. DESIGN: Prospective cross-sectional study. SETTING: University medical center. PATIENT(S): Eighty-five infertile and 51 fertile men. INTERVENTION(S): Assessment of sperm DNA fragmentation, MMP, and standard semen parameters over a 6- to 12-month observation period. MAIN OUTCOME MEASURE(S): Comparison between the results of DNA fragmentation, MMP, and standard sperm parameters alone or combined and achievement of natural conception. RESULT(S): Twenty-six of the 85 (31%) men from infertile couples conceived naturally. The median values of DNA fragmentation and MMP in the men who conceived within the observation period were similar to those in the fertile controls. Optimal threshold values of DNA fragmentation and MMP were 25% as determined by receiver operating characteristic analysis (area under the curve [AUC], 0.70; 95% confidence interval (CI) 0.58-0.82) and 62.5% (AUC, 0.68, 95% CI 0.56-0.80), respectively. The men in the infertile group with values of DNA fragmentation ≤25% and with MMP values ≥62.5% had significantly higher odds for conception (odds ratio [OR], 5.22; 95% CI 1.82-14.93] and OR, 4.67; 95% CI 1.74-12.5, respectively). Normal semen analysis alone had no predictive value for natural conception (OR, 1.84; 95% CI 0.67-5.07]). Both sperm function tests combined had significant odds for natural conception (OR, 8.24; 95% CI 2.91-23.33]), with a probability of 0.607 (60.7%) for both normal values and 0.158 (15.8%) for abnormal values. CONCLUSION(S): Sperm DNA fragmentation and MMP combined may be superior to standard semen parameters for the prediction of natural conception.

A New Baltic Population-Specific Human Genetic Marker in the PMCA4 Gene.

OBJECTIVES: The PMCA gene family consists of 4 genes and at least 21 splice variants; among these, the Ca2+ ATPase 4 (PMCA4) gene encodes a plasma membrane protein abundantly expressed in several tissues, including the kidney, heart, and sperm. Knockout of PMCA4 causes infertility due to immotile sperm in mouse models. We therefore investigated variants in this gene for potential association with infertility in groups of Estonian (n = 191) and Latvian (n = 92) men with reduced sperm motility. METHODS: All exons, exon-intron boundaries, 5' and 3' untranslated regions, and the promoter region of the PMCA4 gene were analysed by direct sequencing for a group of Estonian infertile men. Genotyping of guanine and adenine alleles of rs147729934 was performed, using a custom-designed TaqMan® probe for a group of Latvian infertile men as well as additional groups from Latvia and several groups of people with proven ethnicity from the Baltic region. RESULTS: Although we did not identify any significant associations between variants in the gene and infertility, our results indicated that in all studied Latvian and Estonian groups the adenine allele of the variant rs147729934 was present at a higher frequency than expected. Analysis of additional samples indicated that the adenine allele of rs147729934 likely originated once in the modern-day Baltic or western Russia area, as the frequency of the minor adenine allele observed in this region is remarkably higher than that in the general European population. CONCLUSIONS: Our results revealed no significant difference in frequencies of genetic variants in PMCA4 gene between men with normal and those with reduced sperm motility. The adenine allele of the variant rs147729934 is potentially an informative tool for future population studies concerning ancient Baltic and Finno-Ugric history.

High HPV infection prevalence in men from infertile couples and lack of relationship between seminal HPV infection and sperm quality.

Human papillomaviruses (HPV) are the most frequently sexually transmitted viruses and etiological agents of several human cancers. Controversial results of the role of HPV in infertile population on sperm parameters have been published. The aim of this study was to estimate the type-specific prevalence of HPV DNA infection of the external genitalia and semen in 340 Slovenian men from infertile couples and to establish the relationship between seminal HPV DNA infection and abnormal sperm parameters. Self-taken swabs of the entire penile surface and semen samples were collected, and HPV detection and genotyping were performed. HPV DNA was detected in 37.12% of external genitalia and in 13.61% of semen samples with high HPV type concordance of both sampling sites. The most prevalent HPV types in the male external genitalia were HPV-CP6108 and HPV-84. The most prevalent HPV types in semen were HPV-53 and HPV-CP6108. The prevalence of HPV infection between normozoospermic men and men with abnormal sperm parameters did not differ significantly. Sperm quality did not differ significantly between men with seminal HPV infection and uninfected men. In conclusion, the men from infertile couples are equally susceptible to HPV infection regardless of their fertile potential; seminal HPV infection does not impair sperm quality.

Genetic variation in circadian rhythm genes CLOCK and ARNTL as risk factor for male infertility.

BACKGROUND: The circadian system has a major role in maintaining homeostasis and proper body functions including reproductive capacity. The aim of this study was to examine whether there is an association between genetic variability in the primary clock genes CLOCK and ARNTL and male infertility in humans. METHODOLOGY/PRINCIPAL FINDINGS: We performed a case-control study, where we searched for an association between polymorphisms of CLOCK and ARNTL genes and male infertility in 961 Slovenian and Serbian Caucasian men. The study group consisted of 517 patients with idiopathic infertility and a control group of 444 fertile men. A statistically significant difference was found in genotype distribution between the two groups in the CLOCK gene: rs11932595 (p = 6·10(-5), q = 4·10(-4), OR equaled 1.9 with 95% CI 1.4-2.7), rs6811520 (p = 2·10(-3), q = 8·10(-3), OR = 1.7 with 95% CI 1.2-2.2) and rs6850524 (p = 0.01, q = 0.02, OR = 1.4 with 95% CI 1.1-1.9). Further analyses of haplotypes were consistent with genotyping results. CONCLUSIONS/SIGNIFICANCE: We provide evidence that genetic variability in the CLOCK gene might be associated with male infertility warranting further confirmation and mechanistic investigations.

Intracytoplasmic morphologically selected sperm injection improves development and quality of preimplantation embryos in teratozoospermia patients.

This prospective randomized study investigated whether intracytoplasmic sperm injection (ICSI) outcome can be improved with sperm preselection under ×6000 magnification and intracytoplasmic morphologically selected sperm injection (IMSI) in patients with teratozoospermia and characterized embryo development and quality regarding sperm morphology and presence of head vacuoles. Couples with isolated teratozoospermia were divided into two groups: IMSI group (n=52) and ICSI group (n=70) and fertilization, blastocyst and clinical pregnancy rates were compared. Oocytes from 30 randomly chosen patients from the IMSI group were injected with spermatozoa that had been previously classified under ×6000 magnification into four classes according to the number and size of vacuoles in the head and then cultured separately. Pronuclear morphology, embryo development and blastomere viability were estimated to investigate the influence of sperm morphology, especially vacuoles, on embryo developmental capacity. A significantly higher clinical pregnancy rate was achieved in the IMSI group compared with the ICSI group (48% versus 24%, P<0.05). Fertilization with spermatozoa without head vacuoles yielded higher number of morphologically normal zygotes, higher blastocyst rate and smaller proportion of arrested embryos than spermatozoa with vacuoles and other head defects. IMSI is a method of choice in patients with teratozoospermia.

Apoptotic sperm biomarkers and their correlation with conventional sperm parameters and male fertility potential.

PURPOSE: To investigate the relationship between sperm apoptotic biomarkers and patient clinical characteristics, conventional sperm parameters and fertility potential. MATERIAL AND METHODS: Sperm analysis, phospholipid asymmetry, mitochondrial membrane potential (MMP) and DNA denaturation were assessed in 142 males of infertile couples. Seventy-three couples were allocated to the natural conception group, and 55 couples underwent IVF or ICSI. RESULTS: DNA denaturation correlated positively with age and negatively with testicular volume (TV). MMP correlated negatively with BMI and FSH and positively with TV. Normal viable sperm correlated positively with TV and negatively with age, BMI and FSH. DNA denaturation was associated with a significantly lower natural pregnancy rate (OR 5.4, 95% CI:1.3-22, p = 0.011). CONCLUSION: Sperm apoptosis is related to male age, BMI, testicular volume and FSH. Among the apoptotic markers, only DNA denaturation has been found to predict natural pregnancy better than conventional sperm parameters.

The IMSI procedure improves poor embryo development in the same infertile couples with poor semen quality: a comparative prospective randomized study.

BACKGROUND: Sperm of poor quality can negatively affect embryo development to the blastocyst stage. The aim of this comparative prospective randomized study was to evaluate the role of an intracytoplasmic morphologically selected sperm injection (IMSI) in the same infertile couples included in the programme of intracytoplasmic sperm injection (ICSI) due to their indications of male infertility which had resulted in all arrested embryos following a prolonged 5-day culture in previous ICSI cycles. METHODS: Couples exhibiting poor semen quality and with all arrested embryos following a prolonged 5-day culture in previous ICSI cycles were divided into two groups: Group 1: IMSI group (n = 20) with IMSI performed in a current attempt and Group 2: ICSI group (n = 37) with a conventional ICSI procedure performed in a current attempt of in vitro fertilization. Fertilization rate, embryo development, implantation, pregnancy and abortion rates were compared between current IMSI and conventional ICSI procedures, and with previous ICSI attempts. RESULTS: The IMSI group was characterized by a higher number of blastocysts per cycle than the ICSI group (0.80 vs. 0.65) after a prolonged 5-day embryo culture. There was a significantly lower number of cycles with all arrested embryos and cycles with no embryo transfer in the IMSI group versus the ICSI group (0% vs. 27.0%, p = 0.048). After the transfer of embryos at the blastocyst or morula stage (on luteal day 5) a tendency toward higher implantation and pregnancy rates per cycle was achieved in the IMSI group compared to the ICSI group (17.1% vs. 6.8%; 25.0% vs. 8.1%, respectively), although not statistically significant. After IMSI, all pregnancies achieved by the blastocyst transfer were normally on-going, whereas after ICSI, two of three pregnancies ended in spontaneous abortion. After IMSI, two pregnancies were also achieved by the morula stage embryos, whereas after the conventional ICSI procedure, embryos at the morula stage did not implant. CONCLUSIONS: The IMSI procedure improved embryo development and the laboratory and clinical outcomes of sperm microinjection in the same infertile couples with male infertility and poor embryo development over the previous ICSI attempts.

Association between male infertility and genetic variability at the PON1/2 and GSTM1/T1 gene loci.

Environmental xenobiotics such as organophosphate pesticides are known factors involved in male infertility. Paraoxanase (PON) and glutathione transferase (GST) are involved in biotransformation of organophosphate pesticides. Interindividual genetic variations in biotransformation enzyme activities can lead to differences in the susceptibility to male infertility. This case-control study investigated associations between polymorphisms in the PON and GST genes (PON1-55/192, PON2-311, GSTM1/T1) and infertility. The study group consisted of 187 infertile men (86 with non-obstructive azoospermia (NOA) and 101 with oligoasthenoteratozoospermia (OAT)), whereas the control group comprised of 194 fertile men. Statistically significant differences were found in PON1-55MM genotype (chi-squared=7.37; P=0.02) and PON1-55M allele (chi-squared=5.98; P=0.01) distribution between the infertile and fertile men. A separate analysis revealed that significant differences in genotype frequencies were limited to the OAT group (chi-squared=9.11, P=0.01). However, no significant differences in genotype frequencies of other tested polymorphisms (PON1-192, PON2-311, GSTM1/T1) and male infertility were observed. The PON1-55M allele might represent a risk factor for infertility susceptibility in Slovenian men. Further studies with a larger sample size are needed to confirm these findings.

Epididymovasostomy as the first-line treatment of obstructive azoospermia in young couples with normal spermatogenesis.

In the management of obstructive azoospermia (OA), microsurgery is often replaced by testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI). Testicular biopsy and microsurgical side-to-side epididymovasostomy were performed in 34 azoospermic men with OA mostly due to inflammation. Ductal system patency was recovered in 21 (63.6%) men and natural pregnancy achieved in 13 (38.2%) of couples. Using multiple logistic regression analysis, it was found that ductal system patency and pregnancy were influenced by male and female age and testicular histology. The chance of obtaining patency was three times higher when male age was <38 years and two times higher when normal spermatogenesis alone was found to be present compared with mixed lesions. The chance of achieving a pregnancy was three times higher when the female partner's age was <29 years or normal spermatogenesis alone was present. The pregnancy rates obtained after surgery were not statistically different from those obtained by TESE-ICSI, but when also considering multiple pregnancies, miscarriages and side effects, the results obtained with surgery are better than those obtained with TESE-ICSI.

Male and female factors that influence ICSI outcome in azoospermia or aspermia.

Factors that influenced the clinical results of 220 first-attempt intracytoplasmic sperm injection (ICSI) cycles with testicular spermatozoa were evaluated in 107 men with non-obstructive azoospermia, 72 with obstructive azoospermia and 41 with aspermia. Linear and logistic regression analysis showed that the fertilization rate depended positively on Johnsen score (P = 0.016) and on the type of ovarian stimulation: a higher fertilization rate was observed after ovarian stimulation with agonist and recombinant FSH than after stimulation with agonist and urinary menopausal gonadotrophin (P = 0.026). Embryo development to the blastocyst stage was predicted positively by the number of injected oocytes (P = 0.016) and negatively by male FSH concentration (P = 0.019). A higher proportion of blastocysts developed after the use of frozen-thawed spermatozoa in comparison to fresh spermatozoa (P = 0.034). Embryo development to the blastocyst stage influenced pregnancy (P = 0.002) and live birth outcomes (P = 0.005); live birth was also predicted by female age (P = 0.046). Embryo culture to day 5 in comparison to day 2 did not provide higher live birth rates. In azoospermia/aspermia, the ICSI outcome depends on both male factors (FSH, Johnsen score, sperm status and motility) and female factors (age, number of injected oocytes).

Leptin levels in infertile male patients are correlated with inhibin B, testosterone and SHBG but not with sperm characteristics.

In the present study, differences in leptin levels between different groups of male patients presenting with infertility problems and possible correlations between leptin levels and clinical, spermiological, histological and hormonal characteristics were examined. Two hundred and ten male partners from infertile couples were included in the study. Based on clinical examination, spermiogram and testicular histology results, patients were divided into four groups: 42 men with non-obstructive azoospermia, 15 men with obstructive azoospermia, 68 men with oligoasthenoteratozoospermia and 85 men with normozoospermia. Serum levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), inhibin B, testosterone, sex hormone binding globulin (SHBG) and leptin were measured. After adjustment for body mass index, there was a negative correlation between serum levels of leptin and inhibin B, total testosterone and SHBG (r = -0.189, p = 0.009, r = -0.250, p = 0.001 and r =-0.221, p = 0.003 respectively) but there was no correlation between leptin and classical sperm characteristics. Our results therefore demonstrate a link between leptin and testicular function, independently of FSH and LH, possibly involving testosterone and SHBG through a regulation of Leydig cell function.

Analysis of the hemochromatosis mutations C282Y and H63D in infertile men.

The aim of this study was to find out whether C282Y and H63D mutations in the hemochromatosis (HFE) gene are associated with male infertility and whether the prevalence of the HFE mutations is higher in a group of 262 infertile men in comparison to 200 fertile men. Because the C282Y and H63D HFE gene distributions in infertile men were not significantly different from fertile controls, our data suggest that the C282Y and H63D HFE gene mutations are not risk factors for male infertility and are not associated with clinical manifestations of male infertility.

Copy number of DAZ genes in infertile men.

The aim of the study was to define the relevance of deletions and duplications within the DAZ gene cluster to male factor infertility in a population of 90 infertile men and a control of 50 fertile men using real-time polymerase chain reaction (PCR). We conclude that partial deletions of the DAZ genes are associated with oligozoospermia but not with azoospermia; however, an increased number of DAZ genes does not seem to be a statistically significant risk factor for spermatogenic failure.

Intracytoplasmic sperm injection as a complement to gonadotrophin treatment in infertile men with hypogonadotrophic hypogonadism.

In this study we sought to determine whether intracytoplasmic sperm injection (ICSI) could improve the efficacy of treatment with gonadotrophins in gonadotrophin-deficient men in terms of pregnancy. A series of six adult men (aged 26-47 years) with hypogonadotrophic hypogonadism (HH) is reported: four men with prepubertal isolated idiopathic HH (IIHH) and two adult-onset HH, as part of hypopituitarism secondary to surgical treatment of a pituitary tumour. All were azoospermic. To restore spermatogenesis, all received hormonal treatment with intramuscular human menopausal gonadotrophins (HMG) and human chorionic gonadotrophin (HCG) for 2 to 23 months. High basal serum inhibin B was predictive of rapid and complete recovery of spermatogenesis. In the two adult-onset HH, a natural pregnancy was achieved within 3 months. The four men with IIHH underwent ICSI because of poor sperm quality. ICSI using fresh or frozen-thawed ejaculated spermatozoa was performed after 6-23 months of gonadotrophin treatment. ICSI provided good clinical results in terms of fertilization and embryo quality, and resulted in three pregnancies that ended in three term deliveries. In men with oligozoospermia related to prepubertal IIHH, ICSI shortens the hormonal treatment and enhances the chances of pregnancy.

Seminal elastase-inhibitor complex, a marker of genital tract inflammation, and negative IVF outcome measures: role for a silent inflammation?

There is no consensus on whether and how male genital tract inflammation affects sperm fertilizing potential. The aims of this prospective study were to evaluate the elastase-inhibitor complex in seminal plasma (s-EI) level, a marker of male genital tract inflammation, in men undergoing in vitro fertilization (IVF) having no clinical signs of inflammation, and its association with semen characteristics, and the predictive role of s-EI for the outcome of IVF in terms of fertilization, embryo development to the blastocyst stage and pregnancy. The study involved 104 male partners of infertile couples with normal spermiogram undergoing IVF. On the day of oocyte retrieval, spermiogram and s-EI assessment using homogeneous immunoassay were performed. The outcome of IVF according to the s-EI level was assessed in 85 cycles with two or more oocytes. In 67 cycles embryos were cultured to the blastocyst stage. Spearman's and Pearson's correlation tests, chi-square test, and multiple linear and logistic regression analyses were used for statistical evaluation. Increased s-EI level (> or =250 microg/L) was detected in semen of 32% of men, and in 24% of men without leucocytospermia. We found an association between the s-EI level and semen leucocytes (r = 0.49, p = 0.004) but not with classical sperm characteristics. No correlation between the s-EI level and fertilization was observed. Increased s-EI levels were associated with a poorer blastocyst development rate (p = 0.03) and a higher number of arrested embryos (p = 0.04). Extended embryo culture to the blastocyst stage shows a negative effect of clinically silent male genital tract inflammation on embryo developmental potential.