Expression and Localization of Hypoxia-Inducible Factor-1 Subunits in the Adult Rat Epididymis1

Differential gene expression and hallmarks of stemness in epithelial cells of the developing rat epididymis

Epididymal development can be subdivided into three phases: undifferentiated, a period of differentiation, and expansion. The objectives of this study were (1) to assess gene expression profiles in epididymides, (2) predict signaling pathways, and (3) develop a novel 3D cell culture method to assess the regulation of epididymal development in vitro. Microarray analyses indicate that the largest changes in differential gene expression occurred between the 7- to 18-day period, in which 1452 genes were differentially expressed, while 671 differentially expressed genes were noted between days 18 and 28, and there were 560 differentially expressed genes between days 28 and 60. Multiple signaling pathways were predicted at different phases of development. Pathway associations indicated that in epididymides of 7- to 18-day old rats, there was a significant association of regulated genes implicated in stem cells, estrogens, thyroid hormones, and kidney development, while androgen- and estrogen-related pathways were enriched at other phases of development. Organoids were derived from CD49f + columnar cells from 7-day old rats, while no organoids developed from CD49f^- cells. Cells cultured in an epididymal basal cell organoid medium versus a commercial kidney differentiation medium supplemented with DHT revealed that irrespective of the culture medium, cells within differentiating organoids expressed p63, AQP9, and V-ATPase after 14 days of culture. The commercial kidney medium resulted in an increase in the number of organoids positive for p63, AQP9, and V-ATPase. Together, these data indicate that columnar cells represent an epididymal stem/progenitor cell population.

Explore the Effect of Asthma Regulating HIF-1 Pathway on Sperm Quality Based on Rat Model

This study is to verify the effect of asthma on sperm quality and explore its potential underlying mechanism. We randomly categorized the Sprague-Dawley (SD) rats into control (Group C) and asthma model (Group M) groups. Rats in the asthma model group were induced allergic asthma by intraperitoneal injection of ovalbumin solution. We evaluated the sperm motility and sperm concentration. The expression of the Interleukin-6 (IL6), phosphorylation-signal transducer and activator of transcription 3 (p-Stat3), and hypoxia-inducible factor-1α (HIF-1α) proteins and mRNAs in the testicular tissue was detected by western blotting and RT-qPCR. Compared with group C, sperm concentration and sperm motility in group M rats were significantly decreased (P < 0.05). Meanwhile, compared with group C, the expression levels of IL6, Stat3, and HIF-1α proteins and mRNAs in group M rats were significantly increased (P < 0.05). Asthma can regulate the HIF-1 signaling pathway, promoting the expression of IL6, Stat3, and HIF-1α protein and mRNAs, so as to promote sperm apoptosis and ultimately causing male infertility.

The hypoxic testicle: physiology and pathophysiology

Mammalian spermatogenesis is a complex biological process occurring in the seminiferous tubules in the testis. This process represents a delicate balance between cell proliferation, differentiation, and apoptosis. In most mammals, the testicles are kept in the scrotum 2 to 7°C below body core temperature, and the spermatogenic process proceeds with a blood and oxygen supply that is fairly independent of changes in other vascular beds in the body. Despite this apparently well-controlled local environment, pathologies such as varicocele or testicular torsion and environmental exposure to low oxygen (hypoxia) can result in changes in blood flow, nutrients, and oxygen supply along with an increased local temperature that may induce adverse effects on Leydig cell function and spermatogenesis. These conditions may lead to male subfertility or infertility. Our literature analyses and our own results suggest that conditions such as germ cell apoptosis and DNA damage are common features in hypoxia and varicocele and testicular torsion. Furthermore, oxidative damage seems to be present in these conditions during the initiation stages of germ cell damage and apoptosis. Other mechanisms like membrane-bound metalloproteinases and phospholipase A2 activation could also be part of the pathophysiological consequences of testicular hypoxia.

Why are epididymal tumours so rare?

Epididymal tumour incidence is at most 0.03% of all male cancers. It is an enigma why the human epididymis does not often succumb to cancer, when it expresses markers of stem and cancer cells, and constitutively expresses oncogenes, pro-proliferative and pro-angiogenic factors that allow tumour cells to escape immunosurveillance in cancer-prone tissues. The privileged position of the human epididymis in evading tumourigenicity is reflected in transgenic mouse models in which induction of tumours in other organs is not accompanied by epididymal neoplasia. The epididymis appears to: (i) prevent tumour initiation (it probably lacks stem cells and has strong anti-oxidative mechanisms, active tumour suppressors and inactive oncogene products); (ii) foster tumour monitoring and destruction (by strong immuno-surveillance and -eradication, and cellular senescence); (iii) avert proliferation and angiogenesis (with persistent tight junctions, the presence of anti-angiogenic factors and misplaced pro-angiogenic factors), which together (iv) promote dormancy and restrict dividing cells to hyperplasia. Epididymal cells may be rendered non-responsive to oncogenic stimuli by the constitutive expression of factors generally inducible in tumours, and resistant to the normal epididymal environment, which mimics that of a tumour niche promoting tumour growth. The threshold for tumour initiation may thus be higher in the epididymis than in other organs. Several anti-tumour mechanisms are those that maintain spermatozoa quiescent and immunologically silent, so the low incidence of cancer in the epididymis may be a consequence of its role in sperm maturation and storage. Understanding these mechanisms may throw light on cancer prevention and therapy in general.

The role of cell adhesion molecules in ischemic epididymal injury

OBJECTIVE

The aim of this study was to investigate the role of adhesion molecules in epididymal injury induced by ischemia-reperfusion (I-R) in the rats.

STUDY DESIGN

About 20 male Sprague-Dawley rats were separated into two groups. A sham operation was performed in group 1 (control). In group 2 (I-R), following 6 h of unilateral spermatic cord torsion, 1-h detorsion of the testis was performed. Then, epididymides were removed to measure the tissue levels of malondialdehyde (MDA) and to make histological examination.

RESULTS

Malondialdehyde values increased in group 2. In group 2, the rats demonstrated significant disorganization of the epithelium and loss of microvilli in the epididymal tissue. No abnormal microscopic findings of the epididymis of the rats in the control group. The tenascin expression in the interstitial area of the epididymis was intense in group 2. Intercellular adhesion molecule-1 (ICAM-1) expression by intense brown staining was seen along the basement membrane in epididymal tissue from I-R group rats. The microvillus sites of the epithelia in I-R group were stained mildly by lectin.

CONCLUSION

The increased expression of adhesion molecules found in epididymal injury induced during of postischemic reperfusion may implicate importance of inflammatory infiltration.

The role of cell adhesion molecules in ischemic epididymal injury

OBJECTIVE

The aim of this study was to investigate the role of adhesion molecules in epididymal injury induced by I-R in the rats.

STUDY DESIGN

A total of 20 male Sprague-Dawley rats were separated into two groups. A sham operation was performed in group 1 (control). In group 2 (I-R), following 6 h of unilateral spermatic cord torsion, 1-h detorsion of the testis was performed. Then, epididymides were removed to measure the tissue levels of malondialdehyde (MDA) and to make histological examination.

RESULTS

MDA values increased in the group 2. In the group 2 rats demonstrated significant disorganization of the epithelium and loss of microvilli in the epididymal tissue. No abnormal microscopic findings of the epididymis of the rats in the control group. The tenascin expression in the interstitial area of the epididymis was intense in the group 2. ICAM-1 expression by intense brown staining was seen along the basement membrane in epididymal tissue from I to R group rats. The microvillus sites of the epithelia in I-R group were stained mildly by lectin.

CONCLUSION

The increased expression of adhesion molecules found in epididymal injury induced during postischemic reperfusion might implicate importance of inflammatory infiltration.

The hypoxic testis and post-meiotic expression of PAS domain proteins

Spermatogenesis in the seminiferous tubuli of the testis occurs under a high proliferation rate, suggesting considerable oxygen consumption. Because of the lack of blood vessels, the oxygen partial pressure in the lumen of the tubuli is very low. However, the consequences of these environmental conditions on spermatogenesis are unknown. The PAS domain is found in environmental protein sensors involved in the perception of oxygen partial pressure, light intensity, redox potentials, voltage and certain ligands. We previously identified two PAS proteins highly expressed in the testis: a novel isoform of the hypoxia-inducible factor (HIF)-1alpha and PASKIN, a PAS-Ser/Thr kinase related to bacterial oxygen sensing PAS-domain proteins.

A Dominant-Negative Isoform of Hypoxia-Inducible Factor-1α Specifically Expressed in Human Testis1

Spermatogenesis in the seminiferous tubuli of the testis occurs under a high proliferation rate, suggesting considerable oxygen consumption. Because of the lack of blood vessels, the oxygen partial pressure in the lumen of these tubuli is very low. We previously identified a testis isoform of the hypoxia-inducible factor (HIF)-1alpha in the mouse, termed mHIF-1alphaI.1. Here, we demonstrate that expression of mHIF-1alphaI.1 increases during puberty, further demonstrating its gene induction in postmeiotic germ cells. Using 5'-rapid amplification of cDNA ends, we identified a novel HIF-1alpha isoform in the human testis, called hHIF-1alphaTe. Like mHIF-1alphaI.1, hHIF-1alphaTe mRNA is derived from an alternative promoter-first exon combination, but with a different genomic organization and a different nucleotide sequence. Reverse transcription-polymerase chain reaction analysis confirmed that hHIF-1alphaTe is exclusively expressed in the testis. As determined by immunofluorescence of ejaculated sperm cells, HIF-1alpha protein is mainly localized in the postacrosomal head and in the midpiece of spermatozoa. Though overlapping with mitochondrial localization in human and mouse spermatozoa, neither hHIF-1alphaTe nor hHIF-1alpha associated with mitochondria. In contrast with the ubiquitously expressed HIF-1alpha protein and the mouse testis-specific mHIF-1alphaI.1 isoform, the hHIF-1alphaTe mRNA sequence predicts a protein with an N-terminal truncation of the DNA-binding domain. As shown by yeast two-hybrid assays, hHIF-1alphaTe still formed heterodimeric complexes with HIF-1beta. However, hHIF-1alphaTe was incapable of forming a DNA-binding HIF-1 complex. Overexpression of exogenous hHIF-1alphaTe resulted in the inhibition of the endogenous HIF-1 transcriptional activity, demonstrating that the testis-specific hHIF-1alphaTe isoform is a dominant-negative regulator of normal HIF-1 activity.