Immunolocalisation of aquaporins 3, 7, 9 and 10 in the epididymis of three wild ruminant species (Iberian ibex, mouflon and chamois) and sperm cryoresistance

ContextIn the epididymis, epithelial cells manage changes in the luminal environment for proper sperm maturation. Moreover, aquaglyceroporins, a subgroup of aquaporins (AQP), modulate the transport of water, glycerol and other small molecules in epithelial cells.AimsWe aim to characterise the lining epithelium, quantify its cell composition and immunolocalise the aquaglyceroporins AQP3, AQP7, AQP9 and AQP10 alongside the epididymal ductus of three wild ruminant species, and to determine if species-specific differences could be associated with cauda sperm cryoresistance variations.MethodsEpididymides from Iberian ibex (n = 5), mouflon (n = 5) and chamois (n = 6) were obtained. Cauda spermatozoa were collected and sperm parameters were analysed before and after freezing. Histology and immunohistochemistry of AQP3, 7, 9, 10 and T-CD3 were performed in the caput, corpus and cauda epididymal regions.Key resultsThis work first describes the lining epithelium in Iberian ibex, mouflon and chamois epididymis along the three anatomical regions, consisting of principal, basal, apical, clear and halo cells. However, the percentage of each cell type differed in ibex compared to mouflon and chamois. The positive T-CD3 immunolabeling of all the halo cells confirmed their T-lymphocyte nature. Aquaglyceroporin expression patterns were similar among species, except for differences in AQP7 and AQP10 immunolocalisation in ibex. Species-specific differences in epididymal sperm cryoresistance were confirmed.ConclusionsThe epididymal epithelium of the three wild ruminants differ in their relative number of cell types and AQP immunolocalisation, which ultimately appears to affect cauda epidydimal spermatozoa cryoresistance.ImplicationsOur study provides information on the relevance of the quantitative composition and AQP pattern expression in epididymal lining epithelium on sperm cryoresistance. This work describes the lining epithelium and expression patterns of aquaglyceroporins (AQP3, AQP7, AQP9 and AQP10) in the Iberian ibex, mouflon and chamois epididymis. Species-specific differences in cauda epididymal sperm cryoresistance were confirmed. Differences among the three wild ruminant epididymides in the relative number of epithelial cell types and the immunolocalisation of AQP7 and AQP10 appear to affect the cryoresistance of cauda epididymal spermatozoa. Photograph by Carlos Martinez-Caceres.