Comparative effects of neonatal diethylstilbestrol on external genitalia development in adult males of two mouse strains with differential estrogen sensitivity

Abstract

The effect of neonatal exposure to diethylstilbestrol (DES), a potent synthetic estrogen, was examined to evaluate whether the CD-1 (estrogen insensitive, outbred) and C57 (estrogen sensitive, inbred) mouse strains differ in their response to estrogen disruption of male ExG differentiation. CD-1 and C57BL/6 litters were injected with sesame oil or DES (200 ng/g/5μl in sesame oil vehicle) every other day from birth to day 10. Animals were sacrificed at the following time points: birth, 5, 10 and 60 days postnatal. Neonatally DES-treated mice from both strains had many ExG abnormalities that included the following: (a) severe truncation of the prepuce and glans penis, (b) an abnormal urethral meatus, (c) ventral tethering of the penis, (d) reduced os penis length and glans width, (e) impaired differentiation of cartilage, (f) absence of urethral flaps, and (g) impaired differentiation of erectile bodies. Adverse effects of DES correlated with the expression of estrogen receptors within the affected tissues. While the effects of DES were similar in the more estrogen-sensitive C57BL/6 mice versus the less estrogen-sensitive CD-1 mice, the severity of DES effects was consistently greater in C57BL/6 mice. We suggest that many of the effects of DES, including the induction of hypospadias, are due to impaired growth and tissue fusion events during development.

Current understanding of hypospadias: relevance of animal models

“…evidence exists that hypospadias-inducing agents such as exogenous oestrogens or 'androgen blockers' not only affect the urethral meatus, but also profoundly affect the spatial patterning and differentiation of many of the internal penile structures in mice. 23,[26][27][28] such inferences are inconclusive in the rat because current knowledge of normal rat penile morphology is inadequate.…”

“…26,27 For example, the teratogenic effects of oestrogen on the urethral meatus can be seen in mice treated neonatally with diethylstilbestrol (Des) 10,26,27 (Figures 5d, e and h) as well as in arOM+ mice expressing both mouse and human aromatases (Figure 5f, g) in which there is a physiological elevation in oestrogens. 42 Hypospadias in rats and mice can be induced by a variety of agents, which for the most part fall into two categories: oestrogenic agents and androgen-blocking agents.…”

“…23,26,27 in a general sense these features of mouse hypospadias have direct counterparts in human hypospadias (Figures 2d-f ), and in both species involve malformation and malpositioning of the u rethral meatus. 20,26,27 Preputial hypospadias in humans, rats and mice is fundamentally a ventral defect in the prepuce (supplementary table 3). the human and mouse prepuce forms as a result of fusion of the preputial folds (urethral-preputial folds in the case of the mouse) (Figures 7 and 8).…”

“…28 Oestrogen-induced teratogenic effects on the mouse penis differ somewhat depending on whether exogenous oestrogens are administered prenatally or neonatally. 26,27 unfortunately, the term 'hypospadias' has been used uncritically in the murine literature to refer to a range of defects, and owing to the pervading image of human hypospadias, the term 'mouse hypospadias' typically conjures the idea of a urethral defect of comparable severity to human midshaft hypospadias, which has rarely, if ever been seen in mice. to ensure clarity, first the precise type of hypospadias must be specified: preputial hypospadias; meatal hypospadias (and abnormal urethral meatus); or midshaft hypospadias.…”

“…the failure of epithelial fusion events appears to be one of the morpho genetic mechanisms common to mouse and human urethral hypospadias. 1,26,27,35 thus, while species differences exist in regard to normal penile anatomy, development and development of hypospadias, abnormalities in penile pattern, namely position and morphology of the urethral meatus owing to perturbation of growth, epithelial fusion and other developmental events involving the urethral plate are the essential features of both human and rodent urethral hypospadias. 26,27,32 Mouse urethral hypospadias studies have utilized both pre natal and neonatal Des treatments, which elicit somewhat different malformations, but are both consistent with the designation, meatal hypospadias.…”