CELLULAR HETEROGENEITY AND SPERM MATURATION IN THE ALBINO RAT’S EPIDIDYMIS

Background:Although many studies have described the histology of the young and adult epididymis, in both humans and experimental animals very few have focused on how the epididymis is affected during aging. So the aim of this work is to study the histological and the ultrastructural changes in the albino rat epididymis at different ages and to evaluate how these changes affect sperm.Material and methodsThirty healthy male albino rats were utilized in this study. These animals were classified into three groups (10 animals each) according to their age group. Group 1: immature animals (2- 4 weeks). Group 2: adult (4- 6 months). Group 3: senile (1.5- 2 years). The animals will be anaesthetized by ether inhalation and the epididymis of each was dissected out, cut into small pieces and processed for light and electron microscope examination and morphometrical analysis. For light microscope examination, sections of 5µ were obtained and stained with H & E for studying the general histological structure of the epididymis, Mallory trichrome for demonstrating collagen fibers. Immunohistochemical techniques were applied to study T-lymphocytes morphology and distribution. For electron microscope examination, the epididymis was cut into small pieces, fixed in gluteraldehyde and osmium tetroxide and processed to obtain ultra thin sections (90 nm) that stained with uranyl acetate and lead citrate to be examined with transmission electron microscope. Semi thin sections were stained with toluidine-blue and examined with light microscope.Results :The epididymal tubules of immature animals showed small luminal diameter with no regional differences in epithelial height or luminal diameter and no spermatozoa intraluminal.In adult animals, the tubules exhibited increased luminal diameter with marked regional differences. The tubules of the initial segment had a very tall epithelium with long stereocilia, a small lumen with few spermatozoa and a thin muscle wall. These gradually changed from the initial segment to the cauda. The lining epithelium of epididymal tubules, in adult animals, consisted essentially of principal cells and basal cells. principal cells showed increase in the abundance of cytoplasmic organelles with long stereocilia and apical occluding junctions between adjacent cells that form the blood epididymis barrier. Lesser number of other cell types included clear cells (not present in the initial segment but found in the rest of the epididymis), narrow cells (mostly found in the initial segment), apical cells and halo cells or inter epithelial lymphocytes.In senile animals, epididymal tubules exhibited regional difference and were lined by the same cell types found in adult. Large vacuoles appeared, in senile animals that might occupy the space of many cells. Epithelial cells showed dramatic accumulation of polymorphic lysosomes and lipofuscin pigments. Thickening of the basement membrane was observedConclusion:The previous changes were seen when spermatogenesis was still active, raising the possibility of an intrinsic mechanism of aging. Furthermore, these results support that the impaired seminal quality found in aged animals and men is produced not only by the testes but also by the epididymis.