New insights into androgen-dependent Wolffian duct development

Abstract

In mammals, male and female fetal reproductive tracts are initially indistinguishable with Wolffian ducts (WD) and Mullerian ducts (MD) present in both sexes. Androgens play a vital role in masculinisation of the fetus, including WD rescue and development in males; however, the mechanisms that underlie this process are unknown. The aims of the current study therefore were to investigate the timing and mechanisms involved in androgen mediated WD development. The present study exposed pregnant rats to the androgen receptor antagonist, flutamide (50 or 100 mgkg⁻¹), Di(n-butyl) phthalate (DBP; 500 mgkg⁻¹) which reduces testicular testosterone production, and/or exogenous testosterone during specific time windows in fetal life in order to establish the key time windows for androgenregulated WD development and the possible mechanisms involved.These studies confirmed the vital role for androgens in WD development and highlighted their critical involvement in establishing the early patterning of WD development between el5.5-17.5, prior to any sign of morphological differentiation. At this stage, androgens receptors (AR) are only expressed in the stroma, not in the epithelium, thus androgens must regulate WD differentiation via stroma-epithelial interactions. Contrastingly, high levels of androgens were not required during morphological differentiation of the WD between el 9.5- 21.5 (when coiling occurs). Impaired androgen action during the correct window of development disrupted WD development as evidenced by reduced coiling of the future epididymis. This was likely due to a demonstrated reduction in cell proliferation in both stromal and epithelial compartments, impaired stromal differentiation, reduced epithelial cell height and ultimately epithelial degradation. These stromal abnormalities were noted prior to observing any obvious abnormalities in the epithelium, further highlighting regulation of the epithelium by the stroma. The mechanisms involved in this impaired WD development include interruption to the basement membrane and extracellular matrix, as evidenced by altered expression of some intermediate filaments. These were similar to the mechanisms noted in the regressing female WD but impaired androgen action did not induce apoptosis in the male WD, which was observed in the regressing WD in females. Maternal exposure to testosterone during gestation was able to rescue the female WD and even induce some degree of morphological differentiation, although this was to a lesser degree than that noted in the normal male.