Expression patterns of sex steroid receptors in developing mesonephros of the male mouse: three-dimensional analysis

Abstract

AbstractThe androgen pathway via androgen receptor (AR) has received the most attention for development of male reproductive tracts. The estrogen pathway through estrogen receptor (ESR1) is also a major contributor to rete testis and efferent duct formation, but the role of progesterone via progesterone receptor (PGR) has largely been overlooked. Expression patterns of these receptors in the mesonephric tubules (MTs) and Wolffian duct (WD), which differentiate into the efferent ductules and epididymis, respectively, remain unclear because of the difficulty in distinguishing each region of the tracts. This study investigated AR, ESR1, and PGR expressions in the murine mesonephros using three-dimensional (3-D) reconstruction. The receptors were localized in serial paraffin sections of the mouse testis and mesonephros by immunohistochemistry on embryonic days (E) 12.5, 15.5, and 18.5. Specific regions of the developing MTs and WD were determined by 3-D reconstruction using Amira software. AR was found first at the distal end (gonadal side) of MTs at E12.5, and the epithelial expression showed increasing strength from cranial to the caudal side. Epithelial expression of ESR1 was found in the cranial WD and MTs near the WD first at E15.5. PGR was weakly positive only in the MTs and cranial WD starting on E15.5 but negative in the distal end of the MTs. This 3-D analysis suggests that gonadal androgen acts first on the distal end of MTs but that estrogen is the first to influence MTs on the WD side, while potential PGR activity is delayed and limited to the epithelium.