Postnatal Cell Type- and Segment-Specific Localization of EGFR and Its Ligands (EGF, TGF-α, and AREG) in the Rat...

The epididymis is a specialized male reproductive organ that undergoes marked postnatal differentiation and segmental specialization to support sperm maturation, transport and storage. Previous studies have demonstrated the presence of epidermal growth factor receptor (EGFR) and epidermal growth factor (EGF) in the epididymis; however, their comparative postnatal localization, together with that of transforming growth factor-α (TGF-α) and amphiregulin (AREG), across specific epididymal segments and epithelial cell types has not been systematically characterized in the rat. This study investigated the postnatal histomorphological development and cell type- and segment-associated localization of EGFR, EGF, TGF-α and AREG in the epididymis of Wistar albino rats. Epididymal tissues were collected from neonatal (PND5), infantile (PND20), postpubertal (PND50) and adult (PND70) rats (n = 6 per group). Histomorphological development was evaluated using Crossmon's modified trichrome, periodic acid-Schiff (PAS) and toluidine blue staining, whereas immunolocalization was assessed semiquantitatively by immunohistochemistry. Histological examination revealed progressive epithelial differentiation and segment-specific morphological maturation during postnatal development. EGFR immunoreactivity was detected in basal cells, clear cells and periductal smooth muscle cells, with prominent staining in clear cells of the cauda epididymis in postpubertal and adult rats. Immunoreactivity for EGF and TGF-α was restricted to principal, apical and basal cells of the caput epididymis and was detected only during the postpubertal and adult stages. AREG immunoreactivity was observed in basal and clear cells as well as in periductal smooth muscle cells, without statistically significant developmental or segmental differences. Semiquantitative analysis demonstrated significant increases in EGF and TGF-α immunoreactivity in the caput epididymis during the postpubertal and adult stages (adjusted p = 0.043 for both), and immunoreactivity in the caput was significantly higher than that in the corpus and cauda segments (adjusted p = 0.01 for both). No statistically significant differences were detected in EGFR or AREG immunoreactivity. These findings reveal distinct postnatal cell type- and segment-associated localization patterns of EGFR and its ligands. The localization of EGFR and AREG in basal and clear cells, together with the caput-restricted distribution of EGF and TGF-α, provides a descriptive framework for future studies investigating their possible involvement in epididymal epithelial maturation and regional specialization.