Regulation of urogenital smooth muscle patterning by testosterone and estrogen during prostatic induction

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Abstract
Background Smooth muscle (SM) has been proposed to play an important role in controlling prostate organogenesis by regulating signaling between inductive mesenchyme and developing epithelial prostatic buds. Methods We have examined the effects of testosterone and estrogen upon SM patterning in the embryonic rat urogenital tract (UGT) using in vitro organ cultures, immunohistochemistry, and Western blotting. Results We observed that testosterone elicited a sexually dimorphic difference in SM structure of embryonic UGTs, in cultures grown with testosterone. The addition of estrogen led to an increase in the rate of SM closure, in both males and females. To quantify the effects of steroids upon SM we used Western blotting of SM actin, which showed that estrogen stimulated SM content, while testosterone reduced SM content. Finally, we examined the expression of ERα, ERβ, PR, and SM actin under different hormonal treatments of UGTs grown in vitro. The expression patterns of ERα and ERβ were largely unchanged by hormonal treatment, while PR showed a much broader expression pattern in response to estradiol. Conclusions Our results indicate that testosterone can directly regulate SM patterning and content in the UGT, and that SM is sensitive to both androgens and estrogens.