Establishment of an organ culture system to induce Sertoli cell differentiation from undifferentiated mouse gonads

Establishment of an organ culture system to maintain the structure of mouse Müllerian ducts during development

We previously showed that the anti-Müllerian hormone (AMH), infiltrating from the testis to the mesonephros reaches the cranial and middle regions of the Müllerian duct (MD) and induces their regression using an organ culture in mice. However, it is difficult to maintain structural integrity, such as the length and diameter and normal direction of elongation of the caudal region of the MD, in conventional organ culture systems. Therefore, the pathway of AMH to the caudal MD region remains uncharted. In this study, we established an organ culture method that can maintain the morphology of the caudal region of the MD. The gonad-mesonephros complex, metanephros, and urinary bladder of mouse fetuses at 12.5 dpc attached to the body trunk were cultured on agarose gels for 72 hr. The cultured caudal region of the mesonephros was elongated along the body trunk, and the course of the mesonephros was maintained in many individuals. In males, mesenchymal cells aggregated around the MD after culture. Moreover, the male MD diameter was significantly smaller than the female. Based on these results, it was concluded that the development of the MD was maintained in the present organ culture system. Using this culture system, AMH infiltration to the caudal region of the MD can be examined without the influence of AMH in the blood. This culture system is useful for clarifying the regression mechanism of the caudal region of the MD.

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

The 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 in the specific portion of the MTs near the MT-rete junction at E12.5, and the epithelial expression showed increasing strength from cranial to the caudal regions. 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. This 3-D analysis suggests that gonadal androgen acts first on the MTs near the MT-rete junction but that estrogen is the first to influence MTs near the WD, while potential PGR activity is delayed and limited to the epithelium.