Development and Differentiation of Epididymal Epithelial Cells in Korean Native Black Goat

Conditioned medium and secretome from epididymal epithelial cell cultures improve sperm kinetics and capacitation

Background and Aim

Sperm maturation occurs in the epididymis through interactions with existing molecules inside the lumen. However, the mechanism of epididymis molecular transfer is currently unclear. This study was aimed to determine the necessity of the epididymal epithelial cells (EECs) in the process of sperm maturation in terms of sperm kinetics and tyrosine phosphorylation.

Materials and Methods

A true experimental research design was used in this study. The medium tested was a primary culture of mice caput epididymal cells (cells and culture medium), conditioned medium (CM) (supernatant of EECs), and secretome (CM filtered at 0.22 μm). Sperm was cocultured in EEC culture, CM, and secretome for 1, 2, 3, or 4 h. The original culture medium was used as the control. Sperm kinetic analysis was performed after the indicated times using computer-assisted sperm analysis, and tyrosine phosphorylation was detected using the Western blot technique.

Results

A primary culture of caput EECs was successfully generated. The results showed increased sperm motility and progressive movement after 3 h of incubation (p < 0.05). There was a significant decrease in the average path velocity (VAP) values after 4 h of incubation (p < 0.05), but there was no significant change in the 1, 2, and 3 h incubation groups. The EEC culture-CM and secretome groups showed a significant increased progressivity and VAP percentage values compared with the control medium (p < 0.05). In terms of percentage motility, the culture and CM groups were significantly different from the control medium, but the secretome group was not.

Conclusion

The sperm kinetics of sperm cultured in CM, secretome, and EEC were significantly increased after 3 h of incubation, suggesting that CM and secretome can be used to replace EECs, especially when analyzing molecules secreted by the epididymal epithelium during sperm maturation. The results of this study highlight the potential of CM and secretome as therapy mediums for sperm kinetic abnormalities.

Differential expression and localization of tight junction proteins in the goat epididymis

The blood-epididymis barrier (BEB) forms a unique microenvironment that is crucial for the maturation, protection, transport, and storage of spermatozoa in the epididymis. To characterize the function of tight junctions (TJs), which are constitutive components of the BEB, we determined the expression and localization of TJ proteins such as zonula occludens (ZO)-1, 2, and 3, occludin, and claudin3 (Cldn3) during postnatal development in the goat epididymis. To assess the expression patterns of TJ proteins in immature (3 months of age) and mature (14 months of age) goat epididymides, two different experimental methods were used including immunofluorescence labeling and western blotting. We show that, ZO-1, 2, and 3, and occludin, were strictly expressed and localized to the TJs of the goat epididymis, whereas Cldn3 was present in basolateral membranes as well as TJs. All TJ proteins examined were more highly expressed in the immature epididymis compared to levels in mature tissue. In conclusion, our study indicates that at least five TJ proteins, namely ZO-1, ZO-2, ZO-3, occludin, and Cldn3, are present in TJs, and the expression strength and pattern of TJ proteins tend to be age dependent in the goat epididymis. Together, these data suggest that the distinct expression patterns of TJ proteins are essential for regulating components of the luminal contents in the epididymal epithelium and for forming adequate luminal conditions that are necessary for the maturation, protection, transport, and storage of spermatozoa in the goat epididymis.

Vacuolar H(+)-ATPase is not restricted to clear cells of the epididymal epithelium in cattle

Communication among epididymal epithelial cells creates the best luminal condition where spermatozoa mature, transport and are stored. Vacuolar ATPase (V-ATPase) and cytokeratin 5 (KRT5) have been used as signal indicators for clear and basal cells of the epididymal epithelium, respectively, in mice, rats, bats, and pigs; however, these two markers have not yet been described in the epididymis of bulls. Here, we examined the presence and distribution of the B1 subunit of V-ATPase (B1-VATPase) and KRT5 in the distinct regions of adult bovine epididymides, specifically, the caput, corpus, and cauda. Immunofluorescence staining and confocal microscopy showed that narrow shaped-clear cells were placed in the caput and corpus regions of the bovine epididymis; however, they were absent in the cauda epididymis. In addition, B1-VATPase was highly expressed in the cauda spermatozoa; however, it was rarely detected in the caput spermatozoa. On the other hand, KRT5-positive cells, basal cells, were maintained beneath the basal lamina and they had the traditional form with a dome-shaped morphology from the caput to cauda region of the bovine epididymis. The co-expression of B1-VATPase and KRT5 was confined to basal cells placed in the basal region of the epithelium. In summary, 1) clear cells were present with region-specific localization, 2) B1-VATPase was present in the corpus and cauda spermatozoa but absent in the caput, 3) co-expressed cells with B1-VATPase and KRT5 were present in the adult bovine epididymis, and 4) B1-VATPase was not a specific marker for clear cells in the bovine epididymis. Therefore, the perfect epididymal luminal condition created by the specific expression and localization patterns of B1-VATPase might be necessary to obtain fertilizing capacity of spermatozoa in the bovine epididymis.