Human Testicular Biopsies Research Articles

Levels of liver X receptors in testicular biopsies of patients with azoospermia

To determine whether the transcription factors liver X receptors (LXRs) and their downstream genes, which are involved in the regulation of several testicular functions in mouse models, are differentially expressed in testes of men with nonobstructive azoospermia (NOA) or obstructive azoospermia (OA). Prospective study. University hospital. Patients with various types of NOA (n=22) and with OA (n=5). Human testicular biopsies. Transcript levels were measured in testicular biopsies with the use of quantitative polymerase chain reaction. Correlations of LXR mRNA levels with the number of germ cells, the expression of proliferation and apoptosis markers, and the amount of intratesticular lipids and testosterone were evaluated. The localization of LXRα was analyzed by immunofluorescence. LXR mRNA levels were decreased by 49%-98% in NOA specimens and positively correlated with germ cell number. Accumulations of IDOL and SREBP1c (LXR targets involved in lipid homeostasis) were 1.8-2.1 times lower in NOA samples and mRNA levels of the SREBP1c target gene ELOVL6 were increased 1.9-2.4-fold. Interestingly, the amount of triglycerides and free fatty acids were higher in NOA testes (3.4-12.2-fold). LXRα was present in Leydig cells. Accumulations of LXR downstream genes encoding the steroidogenic proteins StAR and 3βHSD2 were higher in NOA testes (5.9-12.8-fold). Knowledge of changes in the transcript levels of LXRs and some of their downstream genes during altered spermatogenesis may help us to better understand the physiopathology of testicular failure in azoospermic patients.

Human Testicular Peritubular Cells Host Putative Stem Leydig Cells With Steroidogenic Capacity

We aim to examine the steroidogenic phenotype and the differentiation potential of human testicular peritubular cells (HTPCs) and to explore their possible relationship to the adult Leydig cell lineage. The cells of the adult Leydig cell lineage may reside in the peritubular compartment of the testis. This suggestion is supported by the facts that the rodent peritubular cells can be differentiated toward this lineage and that cAMP enhances their steroidogenic potential. Human testicular biopsies, and derived HTPCs, were analyzed by immunohistochemistry, RT-PCR, and Western blotting. After stimulation by forskolin or platelet-derived growth factor-BB, quantitative RT-PCR was used to compare the levels of mRNAs encoding proteins involved in steroidogenesis and steroid production was analyzed by liquid chromatography and tandem mass spectrometry. Immunohistochemical analysis revealed that the peritubular cells that form the outer part of the tubular wall express platelet derived growth factor receptor-α. Furthermore, the pluripotency markers (POU domain class 5 transcription factor 1, GATA-binding protein 4), stem Leydig cell markers (platelet derived growth factor receptor-A, leukemia inhibitory factor receptor), and mRNAs encoding proteins involved in steroidogenesis (nuclear receptor subfamily 5, group A, member 1; steroidogenic acute regulatory protein; CYP11A1; CYP17A1; 3β-hydroxysteroid dehydrogenase) were expressed by the HTPCs. Stimulation with forskolin increased the expression of the steroidogenic markers, which was accompanied by the production of pregnenolone and progesterone by HTPCs in vitro. Treatment with platelet-derived growth factor-BB induced expression of steroidogenic acute regulatory protein. Our results indicate that the tubular wall of the human testis is a reservoir for cells of the adult Leydig cell lineage and that the steroidogenic potential of these cells can be activated in culture.

Melatonin in testes of infertile men: evidence for anti‐proliferative and anti‐oxidant effects on local macrophage and mast cell populations

Melatonin acting through the hypothalamus and pituitary regulates testicular function. In addition, direct actions of melatonin at the testicular level have been recently suggested. We have described that melatonin inhibits androgen production in hamster Leydig cells via melatonin subtype 1a (mel1a) receptors and the local corticotrophin-releasing hormone (CRH) system. The initial events of the melatonin/CRH signalling pathway have also been established. Melatonin and all components of the melatonergic/CRH system were also detected in Leydig cells of infertile men. This study attempted to search for additional targets of melatonin in the human testis, and to investigate the effects of melatonin on proliferation and the oxidative state in these novel target cells. To this aim, evaluation of human testicular biopsies of patients suffering from hypospermatogenesis or Sertoli cell only syndrome and cell culture studies were performed. Melatonergic receptors were found in macrophages (MACs) and mast cells (MCs) of the human testis. In biopsies of patients suffering idiopathic infertility, melatonin testicular concentrations were negatively correlated with MAC number per mm(2) and TNFα, IL1β and COX2 expression, but positively correlated with the expression of the anti-oxidant enzymes SOD1, peroxiredoxin 1 and catalase. Melatonin inhibited proliferation and the expression of pro-inflammatory cytokines and cyclooxygenase 2 (COX2) in both the human non-testicular THP-1 MAC cell line and primary cell cultures of hamster testicular MACs. In the human HMC-1 MC line, melatonin increased the expression of anti-oxidant enzymes and decreased reactive oxygen species (ROS) generation. The results reveal new testicular targets of melatonin and describe anti-proliferative and anti-inflammatory effects of this hormone on testicular MACs. Furthermore, melatonin might provide protective effects against oxidative stress in testicular MCs.

Intratesticular testosterone is increased in men with Klinefelter syndrome and may not be released into the bloodstream owing to altered testicular vascularization - a preliminary report

Klinefelter syndrome (KS, 47,XXY) is associated with low serum testosterone (T), long thought to arise from disturbed steroidogenesis in Leydig cells. However, intratesticular testosterone (ITT) concentrations were recently found to be normal in a KS mouse model(41,XXY*). So far, nothing was known about ITT concentrations in human patients with KS. Therefore, ITT, sex hormone-binding globulin (SHBG) and histological parameters were measured in human testicular biopsies of 11 KS patients, 30 azoospermic patients with Sertoli-cell-only syndrome and nine men with normal spermatogenesis as controls. ITT concentrations showed an overall pronounced excess over intratesticular SHBG in molar terms and were significantly increased in men with KS despite of reduced serum T levels. While the ratio of ITT/serum T was markedly increased in KS, the ITT/LH-ratio was comparable between all groups. After finding significantly increased ITT levels in men with KS, a finding even more striking than in the 41,XXY* KS mouse model, we set out to find a possible 'vascular' explanation for the lack of T release into the testicular blood stream. In testis biopsies from patients,reliable analysis of the vessels is, however, not possible because of the bias resulting from the dissection technique requiring avoidance of larger blood vessels to prevent bleeding. Consequently, the blood vessel constitution was evaluated in whole testis sections from adult male 41,XXY* and 40,XY*mice (n=5, each). Indeed, the blood vessel/testes surface ratio correcting for the smaller testes of XXY*mice was significantly lower in these mice compared with XY*controls. In conclusion, testicular T production does not seem to be impaired in men with KS. On the contrary, ITT concentrations are increased, but not because of increased SHBG activity. The data from the mouse model let us speculate that a reduced vascular bed might be involved in lower release of T into the blood stream.

Cryopreservation of human testicular diploid germ cell suspensions

For patients with threatened fertility, preservation of it is a major concern. Although promising results have been obtained in animal models using testicular germ cell suspensions, in humans, it is crucial to first develop an efficient method of cryopreservation to be able to apply to transplantation. Thus, four reliable and available cryopreservation techniques in any fertility centre were tested to cryopreserve an enriched fraction of diploid germ cells isolated from human testicular biopsies. The protocols were evaluated based on cell viability, and the results showed significant differences between the four methods. The semen and tissue cryopreservation methods appeared to be inadequate for diploid germ cell suspensions, and programmed slow freezing gave significantly lower results than open pulled straw vitrification; the latter was found to be the protocol that best preserved cell viability. The vitrification of isolated human diploid germ cells is innovative and constitutes valuable information for cryopreservation in cases of transplants or in vitro maturation.

Pathophysiology of varicocele in male infertility in the era of assisted reproductive technology

Varicocele is the most common and treatable cause of male infertility. Studies of a rat experimental left varicocele model and human testicular biopsy samples have shown the involvement of various factors in its pathophysiology. Among them, oxidative stress plays a major role in impairing spermatogenesis and sperm function. Therefore, in addition to palpation, scrotal ultrasonography and color Doppler ultrasound, evaluation of testicular oxidative stress (e.g. scrotal temperature is a surrogate parameter) is recommended to enable diagnosis and suitable treatment of varicocele. Varicocelectomy increases the fertilization, pregnancy and live birth rates, indicating improved sperm function; it is therefore important even in couples undergoing intracytoplasmic sperm injection. Routine sperm-function tests are warranted to monitor the sperm quality after varicocelectomy and consequent improvement in the outcomes of assisted reproductive technology. Furthermore, the indications of varicocelectomy in assisted reproductive technology should be widened.

Sertoli-cell-specific knockout of connexin 43 leads to multiple alterations in testicular gene expression in prepubertal mice

SUMMARYA significant decline in human male reproductive function has been reported for the past 20 years but the molecular mechanisms remain poorly understood. However, recent studies showed that the gap junction protein connexin-43 (CX43; also known as GJA1) might be involved. CX43 is the predominant testicular connexin (CX) in most species, including in humans. Alterations of its expression are associated with different forms of spermatogenic disorders and infertility. Men with impaired spermatogenesis often exhibit a reduction or loss of CX43 expression in germ cells (GCs) and Sertoli cells (SCs). Adult male transgenic mice with a conditional knockout (KO) of the Gja1 gene [referred to here as connexin-43 (Cx43)] in SCs (SCCx43KO) show a comparable testicular phenotype to humans and are infertile. To detect possible signaling pathways and molecular mechanisms leading to the testicular phenotype in adult SCCx43KO mice and to their failure to initiate spermatogenesis, the testicular gene expression of 8-day-old SCCx43KO and wild-type (WT) mice was compared. Microarray analysis revealed that 658 genes were significantly regulated in testes of SCCx43KO mice. Of these genes, 135 were upregulated, whereas 523 genes were downregulated. For selected genes the results of the microarray analysis were confirmed using quantitative real-time PCR and immunostaining. The majority of the downregulated genes are GC-specific and are essential for mitotic and meiotic progression of spermatogenesis, including Stra8, Dazl and members of the DM (dsx and map-3) gene family. Other altered genes can be associated with transcription, metabolism, cell migration and cytoskeleton organization. Our data show that deletion of Cx43 in SCs leads to multiple alterations of gene expression in prepubertal mice and primarily affects GCs. The candidate genes could represent helpful markers for investigators exploring human testicular biopsies from patients showing corresponding spermatogenic deficiencies and for studying the molecular mechanisms of human male sterility.

Expression of Cytokeratin 10 Protein in the Human Testis Showing Normal and Abnormal Spermatogenesis

Background: CK10 is a heterotetramer of type I and two type II keratins. Aim: This study examines the expression pattern of cytokeratin 10 (CK10) in human testis. Materials and methods: CK10 protein expression was examined using immunofluorescense staining methods in 30 human testicular biopsy specimens (normal spermatogenesis, maturation arrest and Sertoli cell only syndrome, 10 cases each) obtained from patients undergoing investigations for infertility. Results: In the testis showing normal spermatogenesis, CK10 was expressed in the interstitium and in the seminiferous tubules. A strong cytoplasmic expression was seen in the Leydig cells, Sertoli cells, and spermatocytes. In testes showing spermatogenic arrest, weak CK10 protein expression was observed both in the interstitium and seminiferous tubules (some primary spermatocytes). In the testes showing Sertoli cell only syndrome, negligible CK10 staining was seen both in the seminiferous tubules and in the interstitial cells of Leydig. Conclusions: To the authors’ knowledge, this is the first study indicating CK10 expression in the human testis during normal and abnormal spermatogenesis. The varied expression of CK10 in testes showing abnormal spermatogenesis suggests its possible involvement in this process.

In vitro differentiation of haploid cells after spermatogonial co-culture with sertoli cells from adult human testes

In vitro differentiation of haploid cells after spermatogonial co-culture with sertoli cells from adult human testes

Brief Report: Evaluating the Potential of Putative Pluripotent Cells Derived from Human Testis

Human adult germline stem cells (haGSCs) were established from human testicular biopsies and were claimed to be pluripotent. Recently, the gene expression profile of haGSCs demonstrated that these cells presented with a fibroblast rather than a pluripotent identity. Nevertheless, haGSCs were reported to generate teratomas. In this report, we address this discrepancy. Instead of using haGSCs, which are no longer available for the stem cell community, we used a human testicular fibroblastic cell (hTFC) line that presents with a gene expression profile highly similar to that of haGSCs. Indeed, as shown by microarray analysis, the similarity between hTFCs and haGSCs is comparable to human embryonic stem cell (hESC) lines derived by different laboratories. We argue that the almost identical gene expression profile of hTFCs and haGSCs should result in a very similar if not identical differentiation potential. Strikingly, hTFCs were not able to generate teratomas after injection into nude mice. Instead, they formed a mesenchymal lesion that morphologically resembled the putative haGSC-derived teratomas reported previously. We conclude that haGSCs, which exhibit a profile similar to that of fibroblasts and could not generate teratomas, are not pluripotent. Future work will have to show if pluripotent cells can be derived from human testicular biopsies. Mouse work and certain testicular germ cell tumors indicate that this will be possible.

Mast cell tryptase stimulates production of decorin by human testicular peritubular cells: possible role of decorin in male infertility by interfering with growth factor signaling

Myofibroblastic, peritubular cells in the walls of seminiferous tubules produce low levels of the extracellular matrix (ECM) protein decorin (DCN), which has the ability to interfere with growth factor (GF) signaling. In men with impaired spermatogenesis, fibrotic remodeling of these walls and accumulation of tryptase-positive mast cells (MCs) occur. Human testicular biopsies with normal and focally impaired spermatogenesis (mixed atrophy) were subjected to immunohistochemistry and laser micro-dissection followed by RT-PCR. Primary human testicular peritubular cells (HTPCs), which originate from normal and fibrotically altered testes (HTPC-Fs), were studied by qRT-PCR, western blotting, enzyme-linked immunosorbent assay measurements and Ca(2+) imaging. Phosphorylation and viability/proliferation assays were performed. Immunohistochemistry revealed DCN deposits in the walls of tubules with impaired spermatogenesis. Mirroring the situation in vivo, HTPC-Fs secreted more DCN than HTPCs (P < 0.05). In contrast to HTPCs, HTPC-Fs also responded to the main MC product, tryptase, and to a tryptase receptor (PAR-2) agonist by further increased production of DCN (P < 0.05). Several GF receptors (GFRs) are expressed by HTPCs and HTPC-Fs. DCN acutely increased intracellular Ca(2+)-levels and phosphorylated epidermal GF (EGFR) within minutes. Platelet-derived GF (PDGF) and EGF induced strong mitogenic responses in HTPC/-Fs, actions that were blocked by DCN, suggesting that DCN in the ECM interferes with GF/GFRs signaling of peritubular cells of the human testis. The data indicate that the increase in testicular DCN found in male infertility is a consequence of actions of MC-derived tryptase. We propose that the increases in DCN may consequently imbalance the paracrine signaling pathways in human testis.

Mast cells in human testicular biopsies from patients with mixed atrophy: increased numbers, heterogeneity, and expression of cyclooxygenase 2 and prostaglandin D2 synthase

To determine intratesticular abundance and distribution of tryptase-positive mast cells (MCs) and to examine the expression of key enzymes of prostaglandin (PG) synthesis, cyclooxygenase 2 (COX2), and PGD2 synthase in the testes of men with mixed atrophy (MA) syndrome and in normal samples. Retrospective study. Academic research institute and andrology practice. Nineteen men. Testicular biopsies. Immunohistochemistry and evaluation of COX2 and tryptase-positive MCs, laser microdissection of immunoreactive cells followed by reverse transcriptase polymerase chain reaction for COX2 and PGDS-H mRNA, and transmission electron microscopy. In line with previous studies, few tryptase-positive MCs, but no COX2-positive cells, were observed in testes with normal spermatogenesis. In MA samples, the number of tryptase-positive MCs was significantly increased and the cells accumulated in the walls of the seminiferous tubules. In 11 of 13 MA samples, COX2 protein was detected. In 2 cases, Leydig cells were positive; however, in all 11 of 13 cases, COX2 was localized to MCs, coexpressing tryptase. The proportion of MCs coexpressing COX2 varied from 4% to 35%. Laser microdissection of tryptase/COX2-positive MCs followed by reverse transcriptase polymerase chain reaction revealed PGDS-H mRNA. Transmission electron microscopy identified typical MCs with abundant granules and another subtype with only a few granules, implying that MCs may differentiate in the testes. In patients with MA, testicular MC numbers and phenotypes change with respect to the ability to express COX2 and synthesize PGs. MCs and PGs have emerged as players in spermatogenic dysfunction.

Distinct Expression of Interleukin-1α, Interleukin-1β, and Interleukin-1 Receptor Antagonist in Testicular Tissues and Cells from Human Biopsies with Normal and Abnormal Histology

Cytokines are paracrine/autocrine growth factors known to affect testicular cell functions. The cellular origin and expression levels of interleukin-1 (IL-1) in human normal and pathological testicular biopsies are not yet clear. In the present study, we have investigated the levels and cellular origin of IL-1 family members [IL-1α, IL-β, and IL-1 receptor antagonist (IL-1ra)] in human testicular normal and abnormal biopsies with incomplete maturation arrest (IMA) or Sertoli only syndrome (SOS), using real-time polymerase chain reaction and immunohistochemical staining analysis. Our results show that the levels of IL-1α were higher in Leydig/interstitial cells of biopsies with IMA and SOS compared with normal. The levels of IL-1α in Sertoli cells of normal biopsies were higher than IMA and SOS. The mRNA levels of IL-1α were similar in all biopsies. IL-1β levels were higher in Leydig/interstitial cells of normal biopsies compared with Sertoli and germ cells. The levels of IL-1β were similar in testicular cells of all biopsies. However, the mRNA levels of IL-1β were significantly lower in SOS and IMA biopsies compared with normal. IL-1ra was expressed only in Leydig/interstitial cells, and their expression in normal biopsies was higher than in biopsies with IMA and SOS. The mRNA levels of IL-1ra were similar in all biopsies. Thus, it is possible to suggest the involvement of IL-1 system in the regulation of spermatogenesis and male infertility.

Proteomic analysis of testis biopsies in men treated with transient scrotal hyperthermia reveals the potential targets for contraceptive development

Mild testicular heating safely and reversibly suppresses spermatogenesis. In this study, we attempted to clarify the underlying molecular mechanism(s) involved in heat-induced spermatogenesis suppression in human testis. We conducted global proteomic analyses of human testicular biopsies before, and at 2 and 9 wk after heat treatment. Thirty-one and Twenty-six known proteins were identified with significant differential expression at 2 and 9 wk after heat treatment, respectively. These were used to characterize the cellular and molecular events in the testes when seminiferous epithelia became damaged (2 wk) and recovered (9 wk). At 2 wk post-treatment, the changed expression of a series of proteins could promote apoptosis or suppress proliferation and cell survival. At 9 wk post-treatment, the changed expression of proteins mainly promoted cell proliferation, differentiation and survival, but resisted cell apoptosis. Among those heat-regulated proteins, HNRNPH1 was selected for the further functional study. We found that HNRNPH1 was an anti-apoptosis protein that could regulate the expression of other heat-induced proteins. In conclusion, heat-induced reversible suppression of spermatogenesis occurred by modulating the expression of proteins related to proliferation, differentiation, apoptosis and cell survival pathways. These differentially expressed proteins were found to be key molecular targets affecting spermatogenesis after heat treatment.

Glial cell line-derived neurotrophic factor is constitutively produced by human testicular peritubular cells and may contribute to the spermatogonial stem cell niche in man

Testicular peritubular cells form an ill-characterized cellular compartment of the human testis, which forms a border with Sertoli cells and spermatogonial stem cells (SSCs). A recently developed culture method has identified parts of the secretory repertoire of human testicular peritubular cells (HTPCs), which includes nerve growth factor. Whether peritubular cells produce glial cell line-derived neurotrophic factor (GDNF) and may thus contribute to the stem cell niche is not known. We studied GDNF production in isolated peritubular cells from men with normal spermatogenesis (HTPCs) and impaired spermatogenesis and testicular fibrosis (HTPC-Fs). Human testicular biopsies and peritubular cells in culture were evaluated using immunohistochemistry, laser microdissection (LMD), RT-PCR and measurement of GDNF and cAMP by enzyme-linked immunosorbent assay. We also tested whether GDNF production is regulated by tumour necrosis factor-alpha (TNF-alpha) or tryptase, the products of mast cells or macrophages. Peritubular wall cells are in close proximity to cells expressing the GDNF family co-receptor-alpha1. GDNF mRNA was detected in LMD samples of the peritubular and tubular but not interstitial compartments. HTPCs and HTPC-Fs lack FSH- and LH-receptors but express receptors for TNF-alpha and tryptase. Importantly, peritubular cells express GDNF and constitutively released GDNF into the medium in comparably high amounts. TNF-alpha and tryptase had no effect on the secretion of GDNF by HTPCs or HTPC-Fs. Peritubular cells in testes of normal and sub-/infertile men produce GDNF and are likely constitutive contributors of the SSC niche in the human testis.

Immunohistological Profile of the Ras Homologous B Protein (RhoB) in Human Testes Showing Normal Spermatogenesis, Spermatogenic Arrest and Sertoli Cell Only Syndrome

Ras homologous B protein (RhoB) belongs to the Ras homologous subfamily which consists of low molecular weight (21kDa) GTP-binding proteins. Rho proteins are regulatory molecules associated with various kinases and as such they mediate changes in cell shape, contractility, motility and gene expression. To date, no data are available about the expression pattern of RhoB protein in the human testis showing normal and abnormal spermatogenesis. The present study addresses these issues. Human testicular biopsy specimens were obtained from patients suffering from post-testicular infertility (testis showing normal spermatogenesis, 10 cases) and testicular infertility (testis showing Sertoli cell only syndrome and spermatogenic arrest, 10 patients each). The expression of RhoB was examined using in situ immunofluorescent staining methods. In testes showing normal spermatogenesis, RhoB had a strong expression in the seminiferous epithelium (cytoplasm of Sertoli-cells, spermatogonia and spermatocytes) and in the interstitium (Leydig cells). RhoB expression was weak in the myofibroblasts and absent in the spermatids and sperms. In the testes showing abnormal spermatogenesis, RhoB expression was moderate in the seminiferous epithelium (cytoplasm of Sertoli cells, spermatogonia and spermatocytes) and was completely absent in the Leydig cells, myofibroblasts, spermatids and sperms. To the best of our knowledge, this study provides the first morphological indication that RhoB protein is expressed in human testis and its expression undergoes testicular infertility associated changes. These findings suggest the involvement of RhoB in the process of spermatogenesis in human and their possible therapeutic ramifications in testicular infertility are open for further investigations.

Identification and characterization of spermatogonial stem cells in human testicular biopsy samples

Identification and characterization of spermatogonial stem cells in human testicular biopsy samples

Sertoli cell nuclear changes in human testicular biopsies as revealed by three dimensional reconstruction.

Serial semithin sections of human testicular biopsy material were used for three-dimensional reconstruction in order to obtain information about Sertoli cell nuclei in normal and pathologically altered seminiferous epithelia. The three dimensional reconstruction program is based on the triangulation of image point series. It includes a calculation modus for determining surfaces and an approximation formula for the estimation of volumes. Nuclei from the following specimens were reconstructed and for each the volume (v), surface (s), and a quotient (v/s), which is regarded as a marker for the degree of membrane infoldings, were calculated as follows: (1) For normal spermatogenesis (stage 1, 2, 3, 5; n = 18) v = 409.7 +/- 33.0 microns 3, s = 429.6 +/- 40.5 microns 2, v/s = 0.96 +/- 0.05.(ABSTRACT TRUNCATED AT 250 WORDS)

Flow cytometric analysis of the maldescended testis.

Flow cytometric measurements of the cellular DNA contents of 16 testicular biopsies of 15 patients with maldescended testes were performed. 2 patients were children. 11 patients of pubescent or adult age had no haploid germ cells in the tissue of their maldescended testis. One patient with a testis mobilis had about a normal percentage of haploid germ cells. In one patient a malignant tumor was detected unexpectedly by an aneuploid stem line at 2.2 c. Flow cytometric analysis of human testicular biopsy material is an easy and a fast way to quantify the function of spermatogenesis and detect malignancies.

Heat shock protein 27 expression in the human testis showing normal and abnormal spermatogenesis

Heat shock proteins (HSPs) are molecular chaperones involved in protein folding, assembly and transport, and which play critical roles in the regulation of cell growth, survival and differentiation. We set out to test the hypothesis that HSP27 protein is expressed in the human testes and its expression varies with the state of spermatogenesis. HSP27 expression was examined in 30 human testicular biopsy specimens (normal spermatogenesis, maturation arrest and Sertoli cell only syndrome, 10 cases each) using immunofluorescent methods. The biopsies were obtained from patients undergoing investigations for infertility. The seminiferous epithelium of the human testes showing normal spermatogenesis had a cell type-specific expression of HSP27. HSP27 expression was strong in the cytoplasm of the Sertoli cells, spermatogonia, and Leydig cells. Alternatively, the expression was moderate in the spermatocytes, weak in the spermatids and absent in the spermatozoa. In testes showing maturation arrest, HSP27 expression was strong in the Sertoli cells, weak in the spermatogonia, and spermatocytes. It was absent in the spermatids and Leydig cells. In Sertoli cell only syndrome, HSP27 expression was strong in the Sertoli cells and absent in the Leydig cells. We report for the first time the expression patterns of HSP27 in the human testes and show differential expression during normal spermatogenesis, indicating a possible role in this process. The altered expression of this protein in testes showing abnormal spermatogenesis may be related to the pathogenesis of male infertility.