Comparative proteomics analysis of human FFPE testicular tissues reveals new candidate biomarkers for distinction among azoospermia types and subtypes

Understanding molecular mechanisms that underpin azoospermia and discovery of biomarkers that could enable reliable, non-invasive diagnosis is highly needed. Using label-free data-independent LC-MS/MS acquisition coupled with ion mobility, we compared the FFPE testicular proteome of patients with obstructive (OA) and non-obstructive azoospermia (NOA) subtypes hypospermatogenesis (Hyp) and Sertoli cell-only syndrome (SCO). Out of 2044 proteins identified based on ≥2 peptides, 61 proteins had the power to quantitatively discriminate OA from NOA and 30 to quantitatively discriminate SCO from Hyp and OA. Among these, H1-6, RANBP1 and TKTL2 showed superior potential for quantitative discrimination among OA, Hyp and SCO. Integrin signaling pathway, adherens junction, planar cell polarity/convergent extension pathway and Dectin-1 mediated noncanonical NF-kB signaling were significantly associated with the proteins that could discriminate OA from NOA. Comparison with 2 transcriptome datasets revealed 278 and 55 co-differentially expressed proteins/genes with statistically significant positive correlation. Gene expression analysis by qPCR of 6 genes (H1-6, RANBP1, TKTL2, TKTL1, H2BC1, and ACTL7B) with the highest discriminatory power on protein level and the same regulation trend with transcriptomic datasets, confirmed proteomics results. In summary, our results suggest some underlying pathways in azoospermia and broaden the range of potential novel candidates for diagnosis. SIGNIFICANCE: Using a comparative proteomics approach on testicular tissue we have identified several pathways associated with azoospermia and a number of testis-specific and germ cell-specific proteins that have the potential to pinpoint the type of spermatogenesis failure. Furthermore, comparison with transcriptomics datasets based on genome-wide gene expression analyses of human testis specimens from azoospermia patients identified proteins that could discriminate between obstructive and non-obstructive azoospermia subtypes on both protein and mRNA levels. Up to our knowledge, this is the first integrated comparative analysis of proteomics and transcriptomics data from testicular tissues. We believe that the data from our study contributes significantly to increase the knowledge of molecular mechanisms of azoospermia and pave the way for new investigations in regards to non-invasive diagnosis.

Chronic Copper Exposure Induces Hypospermatogenesis in Mice by Increasing Apoptosis Without Affecting Testosterone Secretion

Chronic copper exposure impaired spermatogenesis in adult male mice. The aim of this study was to determine whether chronic copper exposure can induce apoptosis of testicular cell and hypospermatogenesis via disturbing testosterone synthesis in adult male mice. In the present study, sixty CD-1 male mice were randomly divided into four groups, and were continuously administered for 8 weeks by oral gavage with copper sulfate at a dose of 0, 25, 100, and 150 mg/kg/day, respectively. We determined the content of serum and testicular copper, testicular coefficient, testicular histopathology, sperm count and motility, the mRNA and protein levels of Caspase-3, Bax, and Bcl-2, Leydig cell count, testosterone content, testosterone synthetase, and testosterone synthesis-related genes. The results showed that the copper levels in serum increased in a dose-dependent manner, and the copper levels in testes were significantly related to serum copper levels. Male mice given copper sulfate 100 and 150 dosage groups showed significant decreased in sperm motility and sperm number as well as increased in testes damage, and there was no significant change in testicular coefficient in the four groups. The mRNA levels of Bcl-2 decreased and Caspase-3 increased in 150 dosage group, and Bax increased in two higher dosage groups. Meanwhile, Caspase-3 and Bax proteins increased in 150 dosage group, and Bcl-2 protein decreased in three copper treatment groups. Nevertheless, there were no differences on the levels of testosterone content and testosterone synthetase of 3β-HSD, 17β-HSD, 17α-Hyd, and 20α-Hyd, mRNA levels of Cyp11a1, Cyp17a1, and Star, and quantity of Leydig cells in four groups. Overall, these data showed that chronic copper exposure led to copper residues in the testes, and the doses of 100 and 150 mg/kg/day copper sulfate may induce hypospermatogenesis by increasing apoptosis without affecting testosterone secretion.

The polymorphism L204F affects transport and membrane expression of the sodium-dependent organic anion transporter SOAT (SLC10A6)

Sodium-dependent organic anion transporter (SOAT) represents a membrane transporter specific for sulfated steroid hormones, which are supposed to participate in the regulation of reproductive processes. In man, SOAT shows predominant mRNA expression in the testis and here was localized to primary spermatocytes. SOAT mRNA expression is significantly downregulated in different disorders of spermatogenesis, including hypospermatogenesis. The resulting decline of SOAT-mediated transport of sulfated steroids may participate in the impairment of functional spermatogenesis. Apart from downregulation of SOAT mRNA expression, genetic polymorphisms affecting the transport function of SOAT may have the same negative effect on spermatogenesis. Therefore, in the present study we searched for functionally relevant SOAT polymorphisms, aiming to comparatively analyze their occurrence in patients with impaired spermatogenesis vs. patients with intact spermatogenesis. We found that the SOAT polymorphism L204F showed a significantly reduced transport function for DHEAS when expressed in HEK293 cells. Although the K_m value was identical with that of the SOAT wildtype, the V_max value dramatically declined for the SOAT-L204F variant (942.5 vs. 313.6pmol×mg protein^-1×min^-1). Although the same amount of total SOAT-L204F protein was detected in transfected HEK293 cells compared to the SOAT wildtype, plasma membrane expression was significantly reduced, which points to a plasma membrane sorting defect of the SOAT-L204F variant. Groups of 20 subjects with normal spermatogenesis and 26 subjects with hypospermatogenesis were genotyped for this polymorphism. Both groups showed nearly identical distributions of the SOAT-L204F polymorphism (∼10% heterozygous and ∼5% homozygous), indicating that this polymorphism seems not be causative for hypospermatogenesis.

Evaluation of FSH, LH and testosterone levels in different subgroups of infertile males

Gonadotropins (FSH, LH) and testosterone are the prime regulators of germ cell development. Abnormal spermatogenesis is often associated with altered serum gonadotropins and testosterone. FSH, LH and testosterone levels were estimated in 96 infertile men of whom 35 were azoospermic, 35 were oligozoospermic, 11 were with varicocele and 15 were with histopathological abnormalities like hypospermatogenesis, spermatid arrest and sertoli-cell only syndrome. Results showed statistically significant (p<0.05), increase in the mean FSH and LH levels in all the infertile males studied when compared with the fertile controls (n=35). However, there is no significant difference in the mean levels of testosterone between the infertile and fertile men.

Histopathological patterns of testicular biopsy in male infertility: A retrospective study from a tertiary care center in the western part of Saudi Arabia

OBJECTIVE

To identify and categorize various pathological changes seen in testicular biopsies of males with infertility and to compare the results with data from other local and international studies.

MATERIALS AND METHODS

All testicular biopsies from males with infertility received by the Pathology Department of King AbdulAziz University Hospital, Jeddah, in the period from January 2004 until May 2010 are reviewed and histopathologically classified into seven categories as follows : Normal spermatogenesis, hypospermatogenesis, germ cell maturation arrest (GCMA), Sertoli cell only syndrome, seminiferous tubule hyalinization, mixed and discordant patterns.

RESULTS

One hundred testicular biopsies were identified in the computerized records of the Department of Pathology of King AbdulAziz University Hospital in the studied period. The age ranged from 22 to 70 years with a mean age of 24.5 years. The histopathological patterns were as follows: 14 (14%) cases were reported as normal spermatogenesis;(29, 29%) cases as hypospermatogesis; and 12 (12%) cases were reported as GCMA, mostly at the level of primary spermatocytes. The Sertoli cell only syndrome and the seminiferous tubule hyalinization categories were each reported in 16 cases (16%). Nine cases (9%) showed a mixed pattern. Discordant pattern was seen in 5 (5%) cases.

CONCLUSION

Our study showed that hypospermatogenesis is the commonest pattern in testicular biopsies taken from males with infertility in our region. This study supports the recommendation of bilateral testicular biopsies when investigating male infertility.