The mammalian epididymis is more than a highly convoluted tube divided into four regions: initial segment, caput, corpus and cauda. It is a highly segmented structure with each segment expressing its own and overlapping genes, proteins, and signal transduction pathways. Therefore, the epididymis may be viewed as a series of organs placed side by side. In this review we discuss the contributions of septa that divide the epididymis into segments and present hypotheses as to the mechanism by which septa form. The mechanisms of Wolffian duct segmentation are likened to the mechanisms of segmentation of the renal nephron and somites. The renal nephron may provide valuable clues as to how the Wolffian duct is patterned during development, whereas somitogenesis may provide clues as to the timing of the development of each segment. Emphasis is also placed upon how segments are differentially regulated, in support of the idea that the epididymis can be considered a series of multiple organs placed side by side. One region in particular, the initial segment, which consists of 2 or 4 segments in mice and rats, respectively, is unique with respect to its regulation and vascularity compared to other segments; loss of development of these segments leads to male infertility. Different ways of thinking about how the epididymis functions may provide new directions and ideas as to how sperm maturation takes place.

Arsenic impairs male reproductive functions. However, it is not clear whether different arsenic compounds similarly affect fertility. In this study, we compared the impact of sodium arsenite and arsenate on sperm quality and fertility. After 56 d exposure, male Wistar rats were mated and pregnant females were evaluated by fertility indexes. Clearly, exposure to 10 mg/L arsenite reduced daily sperm production via HO overproduction and germ cells loss. Animals from this group also showed a decrease in epididymal sperm counts and percentage of sperm with intact membranes. Moreover, they presented low fertility potential and high preimplantation loss. In contrast, 10 mg/L arsenate caused oxidative stress in testis, mineral imbalance in epididymis, and sperm membranes damage, with no effects on fertility. Both arsenic compounds at 0.01 mg/L altered reproductive parameters. We concluded that arsenite is more harmful than arsenate to sperm quality and male fertility, with negative influences in early pregnancy.

The main source of environmental arsenic exposure in most countries of the world is drinking water in which inorganic forms of arsenic predominate. The present study was aimed to test the impact of two different compounds of inorganic arsenic in histomorphometric and enzymatic parameters in the testes by oral exposition. Adult Wistar male rats were exposed to sodium arsenite and arsenate in drinking water, testing for each chemical form the concentrations of 0.01 and 10 mg/L per 56 days. The animals intoxicated with arsenic, mainly sodium arsenite, showed reduction in the percentage of seminiferous epithelium and in proportion and volume of Leydig cells. Moreover, there was an increase in the percentage of tunica propria, lumen, lymphatic space, blood vessels, and macrophages. The activity of superoxide dismutase (SOD) did not change among the groups. However, the activity of catalase (CAT) decreased in animals exposed to both arsenic compounds. In addition, the higher concentration of arsenic, mainly as sodium arsenite, caused vacuolization in the seminiferous epithelium. The body and testes weight as well as testosterone concentration remained unchanged among the groups. In conclusion, exposition to arsenic, mainly as sodium arsenite, caused alteration in histomorphometric parameters and antioxidant defense system in the testes.

The Wolffian duct, the proximal end of the mesonephric duct, undergoes non-branching morphogenesis to achieve an optimal length and size for sperm maturation. It is important to examine the mechanisms by which the developing mouse Wolffian duct elongates and coils for without proper morphogenesis, male infertility will result. Here we show that highly proliferative epithelial cells divide in a random orientation relative to the elongation axis in the developing Wolffian duct. Convergent extension (CE)-like of cell rearrangements is required for elongating the duct while maintaining a relatively unchanged duct diameter. The Wolffian duct epithelium is planar polarized, which is characterized by oriented cell elongation, oriented cell rearrangements, and polarized activity of regulatory light chain of myosin II. Conditional deletion of protein tyrosine kinase 7 (PTK7), a regulator of planar cell polarity (PCP), from mesoderm results in loss of the PCP characteristics in the Wolffian duct epithelium. Although loss of Ptk7 does not alter cell proliferation or division orientation, it affects CE and leads to the duct with significantly shortened length, increased diameter, and reduced coiling, which eventually results in loss of sperm motility, a key component of sperm maturation. In vitro experiments utilizing inhibitors of myosin II results in reduced elongation and coiling, similar to the phenotype of Ptk7 knockout. This data suggest that PTK7 signaling through myosin II regulates PCP, which in turn ensures CE-like of cell rearrangements to drive elongation and coiling of the Wolffian duct. Therefore, PTK7 is essential for Wolffian duct morphogenesis and male fertility.

Aluminum (Al) is the most widely distributed metal in the environment and is extensively used in human daily life without any known biological function. It is known that exposure to high concentrations of Al impacts negatively on serum testosterone levels, testicular histomorphometry, and sperm parameters; however, no information is available about the effects of low exposure levels on reproduction. International organizations have established the Al concentration tolerated in drinking water as 3.35 × 10 mg/kg. Therefore, we aimed to compare the effects of long-term exposure to low and high concentrations of Al on male reproductive functions, focusing on testis, epididymis, and sperm parameters. Adult Wistar rats were exposed to aluminum chloride (AlCl) at 6.7 × 10, 3.35 × 10, 10, and 40 mg/kg for 112 days by gavage. Al-exposed animals presented low values of testis and epididymis weight, and serum testosterone levels when compared to controls. The stereology of Leydig cells, epididymis histomorphometry, sperm motility, and structural integrity of sperm membranes changed depending on the Al concentration. In regard to epididymis histomorphometry, the initial segment and caput regions were more affected by Al exposure than distal regions. Otherwise, the histology of testis and epididymis did not alter after the Al exposure, as well as sperm morphology. In summary, we concluded that the consequences of Al exposure at low levels were as negative as high levels on reproductive parameters, suggesting adverse impact on male fertility.

Arsenic (As), in the form of trivalent arsenite or pentavalent arsenate, is a ubiquitous toxic compound naturally occurring in the environment. This study aimed to evaluate the impact of two different forms of inorganic As on reproductive parameters following oral exposure. Adult Wistar male rats were exposed to sodium arsenite or arsenate at concentrations of 0.01 mg/L or 10 mg/L for 56 d in drinking water. Sodium arsenite at both concentrations and sodium arsenate at 10 mg/L produced reduction in daily sperm production, in number of spermatids in the testis, and in sperm in the epididymal caput/corpus regions. Changes in epididymal morphometry were variable and region specific. Total and progressive sperm motility and sperm morphology did not differ markedly between controls and animals exposed to As. The body and reproductive organs weights, as well as testosterone concentration, remained unchanged among all groups. In conclusion, As exposure in drinking water over 56 d produced damage in male reproductive functions in adult rats, suggesting that fertility problems might occur. Therefore, additional studies need to be undertaken to investigate potential mechanisms underlying sodium arsenite- and arsenate-induced disturbances in fertility and reproductive performance.

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