A validated protocol to quantify severity of male urogenital feminization using the MOUSE (Mouse objective urethral severity evaluation)

Abstract

Background Congenital abnormalities vary in presentation, yet studies using model organisms tend to focus on occurrence rather than severity of the defect. Scoring severity of abnormalities in model systems allows explicit hypothesis testing during basic, translational, and reverse translational studies. We developed and validated a protocol to quantify severity of male urogenital feminization (hypospadias) in the mouse model. Hypospadias is one of the most common birth defects in the world. Methods To induce genital feminization, pregnant mice were exposed to different concentrations of the anti-androgen vinclozolin. Genitalia were photographed at gestational age 18.5. A dichotomous scoring system to evaluate genital feminization was developed, and validated against histological measurements of urethral length. A training protocol was developed for novice scorers, and criteria were defined to evaluate precision and accuracy of scores. Results Vinclozolin induced variation in hypospadias severity. Severity scores were tightly correlated with histologically determined urethral length and both techniques showed similar dose response relationships. Novice observers were trained to precisely and accurately score hypospadias severity. Conclusion This standardized scoring system advances the mouse as a model to study urogenital development, and will facilitate research on the mechanisms driving genital feminization in males, and aid translational hypospadias research.