STROMAL DEVELOPMENT IN THE VENTRAL PROSTATE, ANTERIOR PROSTATE AND SEMINAL-VESICLE OF THE RAT

Tile prostate and seminal vesicle (SV) are androgen-dependent secretor y glands of the male genital tract. They produce the bulk of the semin al secret ions. The object of the present study was to examine and doc ument the ontogeny of stromal maturation in the rat anterior and ventr al prostate and SV. These organs have a loosely organized cellular mes enchyme during fetal development. During prostatic development the mes enchyme condensed to form smooth muscle sheaths immediately surroundin g the epithelium, with looser connective tissue between individual duc ts. In tile SV. a loose connective tissue layer called the lamina prop ria lies between the epithelium and developing muscle. Smooth muscle a lpha-actin, myosin, desmin, laminin, vinculin, vimentin and androgen r eceptor (AR) expression were examined by immunocytochemical methods du ring the pre- and post-natal developmental periods. The first marker t o be detected was vimentin, which was initially found throughout the m esenchyme. During development vimentin became mostly restricted to the interductal tissue of the prostate and the lamina propria of the SV. Smooth muscle markers were expressed in an orderly sequence in a proxi mal to distal manner along prostatic ducts, from the urethra towards t he tips. Expression of alpha-actin was followed by vinculin, myosin, d esmin, and laminin. These markers became localized to the developing s mooth muscle sheaths and were not expressed in the interductal tissue of the prostate or the lamina propria of the SV. Smooth muscle markers were expressed in an orderly sequence in a proximal to distal manner along prostatic ducts, from the urethra towards the tips. Expression o f a-actin was followed by vinculin, myosin, desmin, and laminin. These markers became localized to the developing smooth muscle sheaths and were not expressed in the interductal tissue of the prostate or the la mina propria of the SV. Organ culture experiments demonstrated that an drogens were required for the differentiation of smooth muscle sheaths . Castration of adult rats demonstrated that androgens were required t o maintain smooth muscle differentiation, In castrates, the stroma was relatively thicker but less dense than in intact animals. Following c astration; expression of the smooth muscle markers was lost sequential ly in the reverse order of their expression during development. In lon g-term castrates alpha-actin, vimentin and a small amount of vinculin were detected. AR were first detected in the urogenital sinus mesenchy me immediately surrounding the epithelium at 16 days of gestation. As development progressed expression of AR became more widespread, and po stnatally was found throughout the mesenchyme. As maturation of smooth muscle occurred, stromal expression of AR became localized to the mus cular sheath immediately surrounding the epithelium. In the prostate t he interductal connective tissue displayed very low levels of AR expre ssion. In the SV, AR were also observed in the lamina propria. In summ ary, stromal differentiation and dedifferentiation in the rat prostate and SV were found to be androgen-dependent processes with ordered seq uential ontogenic expression of specific markers.