Differential abundances of AQP3 and AQP5 in reproductive tissues from dogs with and without cryptorchidism

Distributions and expressions of Aquaporin-5 and 7 in the testes of developing male chicks

Aquaporins (AQPs) are integral membrane proteins that act as water channels for which a total of 13 orthologs of AQP genes in birds have been reported. Tissue expression and cellular or subcellular localization of AQPs have been poorly investigated in the male reproductive system of birds. We aimed to determine the distribution and localization of AQP5 and AQP7 proteins by immunocytochemistry in testicular tissues obtained from developing chicks (14, 21, 28, 35 and 42 days old). Totally 175 male chicks (Ross 308) were used in the study from which testicular tissue was removed, fixed in 10% formaldehyde solution, then embedded in paraffin blocks. Five μm sections were cut, mounted on poly-L-lysine slides, dried in an oven, then dehydrated using standard immunohistochemistry staining protocol. The sections were imaged with a Nikon Eclipse 50i trinocular light microscope. Immunohistochemical evaluation of the immune reactivity of AQP5 revealed a positive immune reaction in spermatocytes and interstitial areas of the testes in 14-day-old chicks. Testicular tissue AQP5 immune reactivity was observed in the tubule and the interstitial regions of 21-, 28-, 35- and 42-day-old chicks. AQP7 immune reactions were determined in the tubule and interstitial areas testes of developing chicks' testis tissue, with increasing positivity corresponding to older age. The expression of AQP5 and AQP7 appears to be species-specific due to differences in localization and expression in male chicks compared with studies of other mammals, which is likely to play an important role in regulating fluid and sperm volume. This research can serve as a base for future studies that will contribute to the understanding of the male genital system of AQPs.

CFTR modulates aquaporin-mediated glycerol permeability in mouse Sertoli cells

The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel that is crucial for fluid homeodynamics throughout the male reproductive tract. Previous evidence shed light on a potential molecular partnership between this channel and aquaporins (AQPs). Herein, we explore the role of CFTR on AQPs-mediated glycerol permeability in mouse Sertoli cells (mSCs). We were able to identify the expression of CFTR, AQP3, AQP7, and AQP9 in mSCs by RT-PCR, Western blot, and immunofluorescence techniques. Cells were then treated with CFTRinh-172, a specific CFTR inhibitor, and its glycerol permeability was evaluated by stopped-flow light scattering. We observed that CFTR inhibition decreased glycerol permeability in mSCs by 30.6% when compared to the control group. A DUOLINK proximity ligation assay was used to evaluate the endogenous protein-protein interactions between CFTR and the various aquaglyceroporins we identified. We positively detected that CFTR is in close proximity with AQP3, AQP7, and AQP9 and that, through a possible physical interaction, CFTR can modulate AQP-mediated glycerol permeability in mSCs. As glycerol is essential for the control of the blood-testis barrier and elevated concentration in testis results in the disruption of spermatogenesis, we suggest that the malfunction of CFTR and the consequent alteration in glycerol permeability is a potential link between male infertility and cystic fibrosis.

Differential Expressions of Aquaporin Subtypes in the Adult Mouse Testis

Many efforts have been made to study the expression of aquaporins (AQP) in the mammalian reproductive system, but there are not enough data available regarding their localized expression to fully understand their specific roles in male reproduction. The present study investigated the expression and localization patterns of different AQP subtypes in the adult mouse testes and testicular spermatozoa using an immunofluorescence assay. All the studied AQPs were expressed in the testes and revealed subtype-specific patterns in the intensity and localization depending on the cell types of the testes. AQP7 was the most abundant and intensive AQP subtype in the seminiferous tubules, expressing in Leydig cells and Sertoli cells as well as all stages of germ cells, especially the spermatids and testicular spermatozoa. The expression pattern of AQP3 was similar to that of AQP7, but with higher expression in the basal and lower adluminal compartments rather than the upper adluminalcompartment. AQP8 expression was limited to the spermatogonia and Leydig cells whereas AQP9 expression was exclusive to tails of the testicular spermatozoa and elongated spermatids. Taken together, the abundance and distribution of the AQPs across the different cell types in the testes indicating to their relavance in spermatogenesis, as well as in sperm maturation, transition, and function.