Association of prolactin-induced protein with preputial development of hypospadias.

OBJECTIVE

To investigate the molecular aetiology of hypospadias during a critical developmental period by identifying differentially regulated genes in the tissues of individuals with hypospadias and comparing these genes with similar genes in the tissues of control individuals.

MATERIALS AND

METHODS

Pregnant Sprague-Dawley rats were administered flutamide (7.5 mg) on gestational days 15-17 to produce hypospadiac pups. Dams were killed on gestational day 17, and the genital tubercles (GTs) of male pups were harvested. Gene expression of RNA isolated from the GTs was analysed using an oligonucleotide microarray containing 20,500 genes. The results of microarray analysis were confirmed using quantitative real-time PCR (qPCR). Protein expression levels were studied using Western blot analysis. The distribution of genes associated with GT development in rats was histologically examined. Prepuces harvested from patients with hypospadias and phimosis were immunohistochemically examined for gene distribution.

RESULTS

Of the 20, 500 genes, 23 annotated genes, including prolactin-induced protein (Pip), in the GTs of the hypospadiac rats were expressed at levels less than half of that of similar genes in the GTs of the control rats. Findings from qPCR and Western blot analysis revealed significantly lower Pip/PIP expression in the GTs of the hypospadiac rats than in those of the control rats. Immunohistochemical analysis revealed PIP expression in the prepuces of the GTs of the control and hypospadiac rats. PIP was expressed in the human prepuces of the patients with hypospadias and phimosis.

CONCLUSIONS

Pip/PIP, expressed at low levels in the GTs of hypospadiac rats, may be associated with preputial development. This model can be useful to elucidate the molecular mechanisms underlying penile and urethral development as well as preputial development. Further studies should provide detailed information regarding the molecular aetiology of hypospadias.