Mesenchymal-epithelial interactions in the growth and development of the prostate.

Abstract

The ductal networks within the prostate originate from solid epithelial outgrowths (prostatic buds) that emerge from the endodermal urogenital sinus (UGS) immediately below the developing bladder and grow into the surroundings mesenchyme (loose undifferentiated fetal connective tissue). In the human fetus, the first epithelial buds arise from the prostatic urethra around the 10th week of gestation [1–5]. The ducts grow rapidly in length, arborize, and canalize. By 13 weeks there are approximately 70 primary ducts, some of which exhibit secretory cytodifferentiation [1, 3]. The prostatic buds arise from different parts of the prostatic urethra in five separate groups in humans [1]. This observation led Lowsley to originally propose the concept of prostatic lobes. In mouse fetuses, prostatic buds appear on the 17th day of gestation (vaginal plug = day zero), while in fetal rats they appear 1 to 2 days later [6]. In the mouse one to three main ducts per side emerge from the ventral aspect of the UGS, while about 20 to 25 ducts per side emerge from the dorsolateral aspect of the UGS [7]. These two groups of ducts will form the ventral and dorsolateral lobes, respectively. The coagulating gland or anterior prostate is derived from two large buds per side, which grow cranially into the mesenchyme associated with the seminal vesicle [8]. In rats and mice, branching of the prostatic ducts primarily occurs postnatally. Branching patterns are unique for each lobe of the prostate.