Progesterone receptors in the developing genital tubercle: implications to endocrine dysruptors hypothesis as the etiology of hypospadias

Abstract

Purpose In the fetal mice genital tubercles (GT), ontogenetic expression of progesterone receptor (PR) and effect of in utero estrogen and testosterone exposure on PR expression were investigated. Material and methods To evaluate ontogenetic PR expression, GTs from untreated fetuses or pups of gestational days (GD) 12, 14, 16, 18 and newborn were prepared for real-time reverse transcription polymerase chain reaction (RT-PCR) or immunohistochemistry. To evaluate estrogen and androgen effects, pregnant dams were gavaged once daily with corn oil, ethinyl estradiol (EE) or testosterone propionate (TP) from GD12 through 17. At GD-19, GTs of delivered fetuses were harvested for morphological examination to diagnose hypospadias and then pooled for RT-PCR. Results PR protein was first detected at GD-12 on both urethral plate and mesenchyme. At later stages, the staining intensity increased with a PR signal very prominent in the urethra. PR mRNA expression showed different increasing patterns in both sex until birth but no difference was noted between male and female GTs in terms of distribution and quantity of PR expression. In utero EE led to 8.2-fold, 9.7-fold and 5.2-fold increase of PR mRNA in females, males with or without hypospadias respectively. TP significantly decreased PR mRNA levels in both females and males. Conclusions This study provides in-vivo evidence that PRs are highly expressed in developing GTs with an increasing manner until birth implying that the GT is sensitive to the effects of estrogenic and progestogenic endocrine disruptors during fetal life. In addition to their opposing morphological effects, EE and TP lead to opposing effects on PR expression. These findings suggest that progesterone plays an important role in GT development, although the physiological role remains to unknown.