The contribution of RNA-binding motif (RBM) antibody to the histopathologic evaluation of testicular biopsies from infertile men

Fluorescence- and magnetic-activated cell sorting strategies to isolate and enrich human spermatogonial stem cells

OBJECTIVE

To determine the molecular characteristics of human spermatogonia and optimize methods to enrich spermatogonial stem cells (SSCs).

DESIGN

Laboratory study using human tissues.

SETTING

Research institute.

PATIENT(S)

Healthy adult human testicular tissue.

INTERVENTION(S)

Human testicular tissue was fixed or digested with enzymes to produce a cell suspension. Human testis cells were fractionated by fluorescence-activated cell sorting (FACS) and magnetic-activated cell sorting (MACS).

MAIN OUTCOME MEASURE(S)

Immunostaining for selected markers, human-to-nude mouse xenotransplantation assay.

RESULT(S)

Immunohistochemistry costaining revealed the relative expression patterns of SALL4, UTF1, ZBTB16, UCHL1, and ENO2 in human undifferentiated spermatogonia as well as the extent of overlap with the differentiation marker KIT. Whole mount analyses revealed that human undifferentiated spermatogonia (UCHL1+) were typically arranged in clones of one to four cells whereas differentiated spermatogonia (KIT+) were typically arranged in clones of eight or more cells. The ratio of undifferentiated-to-differentiated spermatogonia is greater in humans than in rodents. The SSC colonizing activity was enriched in the THY1dim and ITGA6+ fractions of human testes sorted by FACS. ITGA6 was effective for sorting human SSCs by MACS; THY1 and EPCAM were not.

CONCLUSION(S)

Human spermatogonial differentiation correlates with increased clone size and onset of KIT expression, similar to rodents. The undifferentiated-to-differentiated developmental dynamics in human spermatogonia is different than rodents. THY1, ITGA6, and EPCAM can be used to enrich human SSC colonizing activity by FACS, but only ITGA6 is amenable to high throughput sorting by MACS.

AZF gene expression analysis in peripheral leukocytes and testicular cells from idiopathic infertility

The aim of this study was to assess the frequency of AZF microdeletions in peripheral leukocytes and testicular cells in Chinese men with idiopathic infertility. Expression in testicular cells was also determined. In this study, we screened 62 idiopathic infertile patients, in whom karyotype, sperm count and hormonal parameters were evaluated. Genomic DNA was extracted from the peripheral leukocytes. Molecular analysis was performed by two multiplex polymerase chain reactions (PCR) using a set of eight sequence tagged sites (STS) from 3 different regions of the Y chromosome. Total cellular RNA was extracted from the testicular tissue using a Trizol-method. Reverse Transcription (RT) reactions were performed to synthesize cDNA. Amplification of DFFRY, RBM and DAZ genes was performed to analyze their expression in testicular cells. In this cohort, we found 12 submicroscopic deletions (12/62, 19.4%). Nine patients (9/33, 27.2%) were detected in the azoospermic group and three (3/29, 10.3%) in the severe oligozoospermic group. RT-PCR analysis from testicular cells gave normal amplifications for SRY and DFFRY mRNA in 62 idiopathic patients; two patients were negative for RBM expression; no RBM and DAZ were detected for a case; 12 patients had no expression in the AZFc region involving the DAZ gene. Of 12 cases, three patients with normal PCR analysis of DAZ gene on genomic DNA showed no RT-PCR amplification for DAZ mRNA. The use of RT-PCR of specific spermatid expressed genes in conjunction with examining microdeletions using peripheral leukocytes is suggested to avoid the transmission of the Y chromosomal microdeletions from a father to a son via testicular sperm aspiration (TESE), intracytoplasmic sperm injection (JCSI).

Detection of calretinin expression in abnormal immature Sertoli cells in non-obstructive azoospermia

The current study identified for the first time calretinin expression in abnormal Sertoli cells of azoospermic men who underwent testicular biopsy for sperm recovery and application of the retrieved sperm by in vitro fertilization techniques. Testicular biopsies with various spermatogenic impairments were evaluated immunohistochemically for the expression of the calretinin calcium-binding protein and the marker for immaturity of Sertoli cells, cytokeratin-18 (CK-18). Distribution of the markers was assessed in testes demonstrating a histological phenotype of mixed atrophy, Sertoli cell-only, or normal spermatogenesis (obstructive-azoospermia) and in men carrying a deletion in the azoospermia factor region located on the Y chromosome. Calretinin-immunopositive immature Sertoli cells revealed by co-localization of both markers, calretinin and CK-18, were identified in the mixed atrophy group in seminiferous tubules demonstrating spermatogenic failure. Sertoli cells expressing both markers were rarely detected in all other groups. Leydig cells in all the assessed biopsies expressed calretinin and served as a built-in control for immunoreactivity. This pattern of calretinin-selective expression in immature Sertoli cells suggests a functional relationship between calretinin expression and the degree of Sertoli cell differentiation. Disorders of Sertoli cell differentiation as indicated by calretinin and/or CK-18 expression contribute to the multifactorial mechanisms underlying spermatogenic failure.

Post-transcriptional control in the male germ line

Post-transcriptional mechanisms play an important role in the biology of germ cells, where they control key developmental decisions in cell division, differentiation and death. Because these post-transcriptional controls are cell-type-specific, and often utilize germ-cell-specific RNA-binding proteins, they provide useful diagnostic markers for male infertility and testicular cancer. Investigation of the genetics of male infertility in men and model organisms suggests that disruption of post-transcriptional control mechanisms can cause specific germ cell pathologies, and these studies point to future possible therapeutic routes for restoring spermatogenesis.

Molecular markers for the assessment of postnatal male germ cell development in the mouse

BACKGROUND

A proliferation marker, proliferating cell nuclear antigen (PCNA), a Sertoli cell specific transcription factor, GATA-1 and the male germ cell specific, RNA binding motif (RBM), were used to identify different cellular populations during postnatal development of the mouse testis.

METHODS

Immunohistochemistry, RT-PCR and real-time quantitative RT-PCR (QRT-PCR) were used.

RESULTS

PCNA was expressed in pre-Sertoli and germ cells on the day of birth. Both pre-meiotic germ cells and spermatocytes expressed RBM throughout postnatal development. RBM-positive cell counts and QRT-PCR of RBM showed that average level of RBM per cell is highest in juvenile males between 14 and 21 days. From 42 days onward, there was a dramatic decrease in RBM expression in individual pre-meiotic and meiotic germ cells.

CONCLUSIONS

These markers were used to correlate cell proliferative capability, gene expression profile and anatomic location within the developing mouse testis. The majority of germ cells start active proliferation once they have migrated to the basement membrane or immediately before. RBM is more highly expressed during the first wave of spermatogenesis versus subsequent waves, suggesting that there may be a change in the activity of RBM.

Spermatogonial proliferation patterns in men with azoospermia of different etiologies

OBJECTIVE

To demonstrate the pattern(s) of spermatogonial proliferation in different spermatogenic disorders.

DESIGN

Retrospective case-control study. Teaching hospital.

PATIENT(S)

Azoospermic men who underwent testicular biopsy for sperm recovery and preparation for intracytoplasmic sperm injection.

INTERVENTION(S)

Testicular biopsy evaluation by quantitative immunohistochemistry for proliferating cell nuclear antigen (PCNA).

MAIN OUTCOME MEASURE(S)

The expression of PCNA in spermatogonia as an index of proliferating activity in testes with focal spermatogenesis, spermatocyte maturation arrest, or normal spermatogenesis.

RESULT(S)

In biopsies with focal spermatogenesis (11 men), there was a statistically significant reduction of PCNA-labeled spermatogonia in seminiferous tubules showing spermatocyte arrest compared with the expression in adjacent tubules with advanced spermatogenic stage or in normal spermatogenesis (obstructive azoospermia, six men). However, PCNA expression in tubules of the group with complete maturation arrest (six men) was significantly higher compared with the same spermatogenic defect-spermatocyte arrest-within focal spermatogenesis biopsies.

CONCLUSION(S)

Different causes underlie the spermatogenic disorders reported in this study. In focal spermatogenesis, the disorder is associated with the presence of mitotic inactive spermatogonia. The detection of normal active spermatogonia in the spermatocyte arrest group indicates that the spermatogenic defect, which is accompanied by meiosis impairment, is not related to a malfunction of spermatogonial proliferation.

Reduced human germ cell-less (HGCL) expression in azoospermic men with severe germinal cell impairment

Germ cell-less (GCL) protein is a nuclear envelope protein highly conserved between the mammalian and Drosophila orthologues. In Drosophila, maternal GCL protein is required to establish the germ lineage during embryonic development. In mammals, it is suggested that the GCL function is mainly in spermatogenesis and that it might be related to the ability of mouse GCL to repress transcription. Using reverse transcriptase-polymerase chain reaction analyses, we investigated the role of human GCL (HGCL) in spermatogenesis by studying its expression in the testicular tissue of 67 azoospermic men with normal karyotype and no Y-chromosome microdeletion. Their testicular biopsy specimens underwent meticulous histological and cytological analysis as well as molecular analysis with various markers of spermatogenesis (RBM1, DAZ, and CDY1). The rate of X-Y and 18 chromosome bivalent formation during meiosis was additionally assessed in 22 of these biopsy specimens and correlated to HGCL expression. Expression of HGCL was affected in parallel with the severity of testicular impairment found. Defective sperm motility was associated with the absence of HGCL. Nevertheless, the absence of HGCL expression did not influence the normal process of chromosome bivalent formation in meiosis. Our results suggest that HGCL is not essential for the chromosomal events of meiosis but might be involved in later aspects of spermatogenesis.

Localization of the germ cell-specific protein, hnRNP G-T, in testicular biopsies of azoospermic men

The increasing interest in the application of in vitro fertilization techniques in human reproduction has led to a wide use of testicular biopsies to identify the presence of spermatogenic foci in testes of azoospermic men. Histopathologic evaluation of these testicular biopsies is required to determine the spermatogenic state with respect to fertility potential and to rule out preinvasive testicular lesions. Heterogeneous nuclear ribonucleoprotein G-T (hnRNP G-T) is a germ cell-specific protein expressed most prominently during meiosis. We studied the usefulness of hnRNP G-T antibody in the evaluation of these biopsies and reasoned that its germ cell-restricted expression pattern might provide a marker to improve accuracy of diagnosis. Testicular biopsies with various spermatogenic impairments were evaluated immunohistochemically for hnRNP G-T expression. In biopsies exhibiting normal spermatogenesis (obstructive azoospermia), hnRNP G-T was localized in meiotic pachytene spermatocytes and round spermatids. Immunostaining was barely detected when maturation was arrested at the spermatocyte level and not at all in cases of Sertoli cell-only syndrome. Biopsies with a mixed histologic phenotype and minute concentrations of spermatogenesis demonstrated strong immunostaining only in tubules with full spermatogenesis. This distribution pattern of hnRNP G-T enabled instant identification of spermatogenic foci. Thus, exploitation of the hnRNP G-T marker, which is expressed preferentially as meiosis proceeds, enhances sensitivity and accuracy of diagnosis in the histologic evaluation of testicular biopsies.

Morphometrical quantification of spermatogonial germ cells with the 57B anti-MAGE-A4 antibody in the evaluation of testicular biopsies for azoospermia

The melanoma-associated antigen (MAGE) gene family of cancer-testis antigens is expressed in certain malignant neoplasms and the testis, but not in other healthy tissues. The aim of this study was to determine the usefulness of immunohistochemical staining with the 57B anti-MAGE-A4 mouse monoclonal antibody (MAb) in testicular biopsy specimens from patients with nonobstructive azoospermia and obstructive azoospermia (OA). Fifty-four cases of Sertoli cell only (SCO), 30 cases of spermatocytic arrest, 15 cases of hypospermatogenesis, and 10 testicular biopsy specimens with OA (normal spermatogenesis) were evaluated. Immunohistochemistry was performed using the 57B MAb, which primarily recognizes the MAGE-A4 antigen in paraffinized tissues. The cells were quantitated by a computerized image analysis system. Testicular biopsy specimens with normal spermatogenesis exhibited strong nuclear and cytoplasmic MAGE-A4 staining of spermatogonia and weak staining of spermatocytes, but not spermatids or Sertoli or Leydig cells. No staining was detected in SCO cases. In five cases of SCO with focal spermatogenesis, spermatogonial cells that were initially missed by hematoxylin and eosin staining were detected by MAGE-A4 immunohistochemistry. Immunostaining with the 57B MAb greatly enhanced identification of spermatogonia in cases of spermatocytic arrest and hypospermatogenesis. The number of MAGE-A4-positive spermatogonia was significantly decreased in hypospermatogenesis, as opposed to the OA group (12.1 +/- 4.3 and 30.3 +/- 10.0, respectively). The number of MAGE-A4-positive primary spermatocytes was significantly increased in early maturation arrest, as compared with the OA group (48.2 +/- 10.8 and 16.9 +/- 9.8, respectively). The 57B anti-MAGE-A4 MAb is a useful marker for the detection and quantitation of spermatogonial germ cells. It also facilitates automated image analysis and provides greater accuracy in the histopathologic evaluation of testicular biopsy specimens.

Double immunolabeling by the RBM and the PLAP markers for identifying intratubular (in situ) germ cell neoplasia of the testis

Identification of intratubular germ cell neoplasia (carcinoma in situ, CIS) of the testis is a diagnostic challenge, and markers are sorely needed to assist in accurately identifying the lesion. RNA-binding motif (RBM) protein, encoded by the Y chromosome, is expressed exclusively and consistently in differentiated male germ cells, while it is absent in neoplastic germ cells. Another immunohistochemical marker, placental alkaline phosphatase (PLAP), is commonly used for the detection of undifferentiated germ cells. The current study demonstrates that simultaneous use of the immunohistochemical markers, RBM and PLAP, by double immunolabeling enhances the accuracy of diagnosing CIS, a preinvasive testicular neoplasm.

Sertoli cell maturation in men with azoospermia of different etiologies

OBJECTIVE

To evaluate the involvement of Sertoli cell in different spermatogenic disorders.

DESIGN

Retrospective case-control study.

SETTING

Teaching hospital.

PATIENT(S)

Azoospermic men who underwent testicular biopsy for sperm recovery in preparation for intracytoplasmic sperm injection.

INTERVENTION(S)

Testicular biopsy evaluation by quantitative immunohistochemistry for the immature Sertoli cell markers anti-Müllerian hormone and cytokeratin 18 (CK-18).

MAIN OUTCOME MEASURE(S)

Relative area of immature Sertoli cells in testes with focal spermatogenesis, spermatocyte maturation arrest, or normal spermatogenesis.

RESULT(S)

The relative area occupied by immature Sertoli cells, as revealed by anti-Müllerian hormone and CK-18 expression, was highest in the 11 men with focal spermatogenesis. In the group representing normal spermatogenesis (obstructive azoospermia, 6 men) and in the group characterized by spermatocyte maturation arrest (6 men), the areas occupied by anti-Müllerian hormone- and CK-18-positive cells were minimal.

CONCLUSION(S)

Different etiologies underlie the spermatogenic disorders reported in this study. In focal spermatogenesis with high anti-Müllerian hormone and CK-18 expression, the spermatogenic impairment is associated with the presence of immature Sertoli cells. The detection of normal mature Sertoli cells in the spermatocyte maturation arrest group indicates that the spermatogenic defect that is accompanied by an impairment of meiosis is intrinsic to the germ line without affecting Sertoli cell differentiation.

Immunohistochemistry in the evaluation of spermatogenesis and Sertoli cell's maturation status

An increasing incidence of male infertility has been noted over the past few decades. This adds urgency to the need to develop immunohistochemical markers for better evaluation of testicular biopsies. We provide evidence that a histopathological evaluation performed according to morphological criteria and assisted by immunohistochemical staining on consecutive sections enhances the sensitivity and accuracy of the diagnosis based on testicular biopsies from infertile men.