ABSTRACT
Answer: (c) Shapiro et al have shown androgen receptor expression in the stroma and luminal epithelium of the UGS of the developing human prostate as early as 7 weeks, while 5α-reductase expression is observed only in the prostatic stroma at 7 weeks and in the basal layer of the UGS epithelium at 9 weeks. 9 Regional 5α-reductase expression varies from 7 to 16 weeks, with increasing expression observed in a caudal to cranial direction at every gestational age. Diminished expression occurs after 18-20 weeks. The most posterolateral stroma and the ductal epithelium in the posterior prostatic lobe never express 5α-reductase. The lateral lobes show distal ductal epithelial expression, while the ducts emanating from above the ejaculatory ducts (EDs) express 5α-reductase in their proximal and distal ductal epithelium. These localization studies support the notion that DHT serves largely as a signal amplification for prostatic development and is directly associated with the distance the target tissue is from the testicular androgen source. 9,10
5. Whentissuerecombinationexperiments combine adult bladder epithelium (BLE) with male urogenital mesenchyme, the following structure forms:
(a) Vagina (b) Prostatic ducts (c) Seminal vesicle (d) Smooth muscle (e) Ejaculatory ducts
Answer: (b) Tissue recombinant experiments have been used to examine epithelial-mesenchymal interactions on the differentiation and
organization of prostatic SM. 11 combined adult prostatic epithelium (PRE) with UGM or seminal vesicle mesenchyme (SVM) or BLE with UGM or SVM. Prostatic ducts developed in all tissue recombinants when UGM was used with either epithelium. SM cells also organized into sheets resembling prostate. When SVM was combined with either epithelium, the prostatic ducts were surrounded by thick SM cells resembling seminal vesicle. The SM was unorganized in grafts of SVM or UGM. These experiments suggest that male UGM dictates spatial organization, but SM differentiation is induced by epithelium. Urothelium may also direct the organization of SM tissue, since urothelium is thought to be a potent inducer of SM differentiation. Cunha 12 has shown that the proximal segments of prostatic ducts near the urethra express urothelial membrane antigen and have associated thick layers of SM cells surrounding them. All of these tissue recombinant experiments show that interactions between the mesenchyme and epithelium are reciprocal.
