Dose and Temporal Analysis of Vinclozolin-Induced Penile Abnormalities

Presentation Number: SAT 257
Date of Presentation: April 1st, 2017

Ciro Maurizio Amato* and Krista Mccoy
East Carolina University, Greenville, NC

Abstract

Hypospadias has increased 200% in the past 40 years, making it the second most common birth defect in the United States. Hypospadias occurs when the urethra exits ventrally along the penis, rather than the distal tip. Exposure to endocrine disrupting chemicals (EDCs) is strongly associated with hypospadias in humans, and is known to induce hypospadias in rodent models. Normal penis development is tightly controlled by endogenous androgens produced by the testes beginning at embryonic day 13.5. Disruption of androgen dependent signaling during this masculinization window alters several aspects of penile development and results in feminization of the external genitalia. Both humans and rodents exhibit a continuous range of hypospadias severity, but the mechanisms that drive this variation are not well known. To begin to understand the drivers of hypospadias severity, we must understand the developmental timeline for initiation of genital masculinization. Here we used vinclozolin (fungicide) as a model anti-androgenic EDC to answer these questions. To determine how dose and timing of androgen signaling antagonism affects hypospadias severity CD1 mice (N=48) were separated into 2 separate dosing groups. Mice exposed a longer dosing window received corn oil control (CO), 75, 100, 125, and 150 mg/kg of vinclozolin on embryonic days (E) 13.5-16.5. Mice exposed to the shorter dosing window received the same doses on E14.5-16.5. To test whether effects were due to the timing of exposure (e.g., adding E13.5) or total dose we also dosed with 200 or 50 mg/kg for the three or four day window respectively. This experimental design allowed us to evaluate the relative importance of the timing of antiandrogen exposure versus the total amount of antiandrogen exposure for altering hypospadias severity. On E 18.5 all pups were sacrificed and external genitalia were evaluated histologically. We find that timing of exposure increases genital feminization. Pups from the shorter dosing window had less severe hypospadias and urogenital feminization. This suggests that E 13.5 is a critical day and that early testosterone signaling is essential for normal genital masculinization in mice. We identify exposure regimens that future studies analyzing developmental and molecular mechanisms driving hypospadias severity can use to induce specific severities.

 

Nothing to Disclose: CMA, KM