Induction of prostatic morphology and secretion in urothelium by seminal vesicle mesenchyme

Mesenchymal-epithelial interactions are essential for the development of the male reproductive tract. Tissue recombination experiments have been used to define the characteristics of these interactions. When mesenchyme, embryonic connective tissue, is recombined with epithelium from another organ an instructive induction may occur in which the developmental fate of the epithelium is altered. Instructive inductions are most common when the epithelium that is removed from the mesenchyme and the epithelium that is recombined with the mesenchyme are from the same germ layer. All of the mesenchyme of the male reproductive tract is of mesodermal origin. The epithelia of these organs are derived from either the mesodermal Wolffian duct epithelium or the endodermal urogenital sinus epithelium. Urogenital sinus mesenchyme can instructively induce bladder and urethral epithelium to form prostate (Donjacour, A. A. and Cunha, G. R. (1993) Endocrinol. 132, 2342-2350) and seminal vesicle mesenchyme can instructively induce epithelium from the ductus deferens and ureter (Cunha, G. R., Young, P., Higgins, S. J. and Cooke, P. S. (1991) Development 111, 145-158) to form seminal vesicle. To see whether inductive interactions could occur across germ layers in this system, seminal vesicle mesenchyme, normally associated with a mesodermal epithelium, was recombined with epithelium from neonatal or adult bladder or urethra, which are of endodermal origin. The resulting tissue recombinants were analyzed histologically and by immunocytochemistry and western blotting with antibodies to prostatic and seminal vesicle secretory proteins. Full prostatic differentiation was observed in tissue recombinants made with seminal vesicle mesenchyme plus either adult or neonatal bladder or urethral epithelium. These tissue recombinants made dorsolateral but not ventral prostatic secretory proteins. None of them developed into seminal vesicle. To examine whether epithelial androgen receptors were required for this process, seminal vesicle mesenchyme was recombined with urothelium from mice with the testicular feminization mutation. These mice lack functional androgen receptors. While these tissue recombinants grew, no prostatic proteins were detected. Seminal vesicle mesenchyme acted as a potent prostatic inducer, indicating that similar mesenchymal signals can induce prostatic and seminal vesicle development. Urogenital epithelia of both endodermal and mesodermal origin appeared to be able to respond to these inductive signals produced by the seminal vesicle mesenchyme; however, their responses differed depending on their germ layer of origin: mesodermal epithelium yielding seminal vesicle (Cunha, G. R., Young, P., Higgins, S. J. and Cooke, P. S. (1991) Development 111, 145-158) and endodermal epithelium yielding prostate.