Development of the human prostate

Abstract

This paper provides a detailed compilation of human prostatic development that includes human fetal prostatic gross anatomy, histology, and ontogeny of selected epithelial and mesenchymal differentiation markers and signaling molecules throughout the stages of human prostatic development: (a) pre-bud urogenital sinus (UGS), (b) emergence of solid prostatic epithelial buds from urogenital sinus epithelium (UGE), (c) bud elongation and branching, (d) canalization of the solid epithelial cords, (e) differentiation of luminal and basal epithelial cells, and (f) secretory cytodifferentiation. Additionally, we describe the use of xenografts to assess the actions of androgens and estrogens on human fetal prostatic development. In this regard, we report a new model of de novo DHT-induction of prostatic development from xenografts of human fetal female urethras, which emphasizes the utility of the xenograft approach for investigation of initiation of human prostatic development. These studies raise the possibility of molecular mechanistic studies on human prostatic development through the use of tissue recombinants composed of mutant mouse UGM combined with human fetal prostatic epithelium. Our compilation of human prostatic developmental processes is likely to advance our understanding of the pathogenesis of benign prostatic hyperplasia and prostate cancer as the neoformation of ductal-acinar architecture during normal development is shared during the pathogenesis of benign prostatic hyperplasia and prostate cancer.

Figure 1.

UGS epithelium from a fetal mouse on gestation day 15 after removal of the mesenchyme. Images were taken by scanning electron microscopy (SEM) at successive 90° rotations of the sample, starting with a lateral view (A). Dotted line in (A) indicates that portion of the UGS from which prostatic buds will emerge. Arrowheads show where the Mullerian ducts entered the UGS epithelium. From Lin et al (2003) with permission.

Figure 2.

Section of the urogenital sinus of a 16-day mouse embryo (pre-bud stage) showing urogenital sinus epithelium (UGE), dense urogenital sinus mesenchyme (UGM) and Wolffian ducts (WD). Prostatic buds have not yet developed.

Figure 3.

UGS epithelium from a wild-type fetal mouse on gestation day 18 after removal of the mesenchyme. Two lateral views (A and B), a view of ventral buds (C), and a view of anterior and dorsal buds (D) taken by SEM. Ventral buds (blue), dorsal buds (green), lateral buds (yellow), anterior buds (red), bladder neck (BN), and seminal vesicles (SV) are shown. Prostatic epithelial buds on the lateral surfaces of the UGS that are difficult to classify as either lateral or dorsal buds are tinted blue-green. From Lin et al (2003) with permission. Scale bar in (B) applies to all images.

Figure 4.

Wholemount images of human fetal prostates and bladders from 13 to 21 weeks. The prostate is the distinct bulge below the bladder (arrows). Pr=prostate.

Figure 5.

Drawings of adult human prostate. (A) Anterior wall of the urethra has been removed to visualize the verumontanum (green) as well as the posterior and lateral walls of the prostatic urethra. Note the distribution of openings of the prostatic ducts in the sulci (urethral recesses or furrows) lateral to the verumontanum as described previously (Timms, 1997). (B) Drawing of a transverse section through the verumontanum (highlighted in red) of an adult human prostate showing the prostatic utricle and ejaculatory ducts joining the prostatic urethra. The prostatic ducts emerge from the urethra in the recesses lateral to the verumontanum. Mucosal glands emerge from the ventral aspect of the urethra. Ejac. duct= ejaculatory duct.

Figure 6.

Sections of a pre-bud 9-week human fetal urogenital sinus (UGS) in the region of the verumontanum, which is a dorsal prominence projecting into the UGS. The Wolffian ducts (WD) flank the Mullerian-derived prostatic utricle, which opens into the UGS at/near the apex of the verumontanum. Sections are immunostained for Foxa1 (A), Pax2 (B), TP63 (C), and androgen receptor (AR) (D) as indicated. Scale bar applies to all images.

Figure 7.

Sections through the verumontanum of a 9-week pre-bud UGS immunostained for keratins 6 & 7 (A), keratins 8 & 15 (B) and keratin 19 (C). WD= Wolffian duct, UGS= urogenital sinus.

Figure 8.

(A) Section of the adult mouse prostate just cranial to the verumontanum. Dorsal to the prostatic urethra are the paired ducts of the seminal vesicles (SV duct) and the vas deferens (VD). Note the thick rhabdosphincter (double-headed arrows) surrounding the central structures. (B) A section of the adult mouse prostate at the level of the verumontanum, which projects into the prostatic urethra and at this level is tethered dorsally and ventrally to the wall of the prostatic urethra. The left side of the verumontanum displays the crescent-shaped seminal vesicle duct (SV duct) dorsal to the vas deferens (VD). On the right side of the verumontanum, these two ducts have joined to form an ejaculatory duct (EJD). Surrounding the prostatic urethra and internal to the rhabdosphincter is a circumferential layer of peri-urethra glands (not labeled).

Figure 9.

Three-dimensional reconstruction of mouse and human prostates. (A) Dorsal view of a newborn mouse urogenital sinus reconstruction showing the dorsal prostatic outgrowths (in green, arrow D) situated lateral to the prostatic utricle (white). The seminal vesicles (SV) and ejaculatory ducts have been removed from this reconstruction to clearly illustrate that the most cranial ducts from the elongated and paired anterior prostates (dark blue, AP), also known as the coagulating glands which lie adjacent to the mouse seminal vesicles. Also shown are a few of the lateral (yellow, arrow L) and ventral (light blue, arrow V) prostatic ducts. The prostatic utricle is the midline structure in white. (B) Dorsal view of a 13-week male human fetal prostate showing a similar paired pattern of prostatic ductal outgrowths from the UGS. The most cranial dorsal prostate outgrowths correspond to the equivalent anatomical location of the mouse coagulating glands. At these stages of ductal growth, the mouse and human prostate budding patterns demonstrate striking similarities. The human prostatic utricle is the midline structure in white, and also shown are the seminal vesicles (SV). (C) Lateral view of the same human UGS. Modified from (Timms, 2008) and (Timms and Hofkamp, 2011).

Figure 10.

Light sheet™ three-dimensional reconstruction of a 12-week human fetal prostate immunostained for E-cadherin (red, A-C) to display epithelium and S100 (D, green) to display neurons. Lateral views (A, B & D) and dorsal view (C). Boxed area in (A) is enlarged in (B) to show elongating and branching prostatic buds. (D) Shows the rich network of ganglion cells and neuronal processes that are associated with the developing human prostate. Ejd= ejaculatory ducts.

Figure 11.

Sections of human fetal prostates stained for Ki67 at the ages indicated showing solid prostatic epithelial buds/cords heavily labeled with Ki67 (arrowheads) and reduced Ki67 labeling in luminized ducts and in the urethra (Ur). Ejd= Ejaculatory ducts, Ur= Urethra, UGS= urogenital sinus.

Figure 12.

(A) Section of human fetal prostate at 14 weeks of gestation. The red dots indicate the proximal origin of a prostatic duct and the first branch point, respectively. The distance between these two points is ~250µm. (B) A thick (0.5mm) coronal section of a 17-week human fetal prostate photographed with transmitted light. Red dots are placed on 3 prostatic ducts depicting ductal length to the first branch point. In all three cases the distance is ~1000μιm. The thin white line above the scale bar in (B) is ~1000μιm.

Figure 13.

Sections of canalized human fetal prostatic ducts from 15- to 19-week fetuses exhibiting advanced differentiation immunostained as indicated. Scale bar applies to all images.

Figure 14.

Sections of human fetal prostatic ducts at or near the canalized-solid interface immunostained as indicated. In (E &F) note that AR is absent of solid epithelial cords, but present in canalized ducts. Double-headed arrows in emphasize differences between solid epithelial cords and canalized ducts.

Figure 15.

Transverse sections of developing human prostate immunostained for smooth muscle α-actin. (A) is a section through the verumontanum of a 9-week pre-bud UGS in which sparse α-actin-positive cells (white arrowheads) are seen in ventral-lateral UGM, whereas α-actin-positive cells are abundant in the wall of the rectum. (B) is section of a human fetal prostate showing smooth muscle bundles in ventral UGM at 15 weeks of gestation. (C) is a section of a human fetal prostate at 19 weeks of gestation showing α-actin-positive smooth muscle around the periphery where solid epithelial cords are branching. WD= Wolffian duct, UGS= urogenital sinus, Ur= urethra, EJD=ejaculatory ducts.

Figure 16.

Sections of xenografts of right and left halves of a 14-week human fetal prostate grown for 4 weeks in castrated male athymic mice treated with a 20mg pellet of dihydrotestosterone (DHT) (A1 & A2) or androgen-deficient control (sham) (B1 & B2) immunostained for androgen receptor. A small number of solid buds were present at the time of grafting. In the DHT-treated specimen, note the large number of ducts, many of which are canalized (A1 & A2), while in the androgen-deficient control specimen few ducts are seen and few are canalized (B1 & B2). Note the presence of AR broadly in epithelial and stromal cells in the DHT-treated specimen (A1 & A2). In the androgen-deficient control AR is absent (AR-) in the stromal cells in close association with the epithelium but is present in peripheral stroma (AR+) (B1 & B2).

Figure 17.

Xenografts of right and left halves of a 14-week human fetal prostate grown for 4 weeks in castrated male athymic mice treated with a 20mg pellet of dihydrotestosterone (DHT) or untreated control (sham) as indicated. For TP63 and keratins 7, 8 and 19 the status of epithelial differentiation is advanced in DHT-treated specimens (Al-El)versus androgen-deficient control specimens (A2-E2). Patterning of α-actin-positive smooth muscle is also affected by DHT (El versus E2). S100-positive ganglia and nerve fibers were seen in both DHT-treated and control grafts (F1-F2). Scale bar in (D1 -D2) applies to (A-C).

Figure 18.

Xenografts of right and left halves of a 14-week human fetal prostate grown for 4 weeks in castrated male athymic mice treated with a 20mg pellet of dihydrotestosterone (DHT) or untreated control (sham) as indicated immunostained for NKX3.1. Solid epithelial cords and canalized ducts observed in androgen-deficient control specimens were devoid of NKX3.1 immunostaining (A), whereas canalized ducts (but not solid epithelial cords) of DHT-treated specimens expressed NKX3.1 (B).

Figure. 19.

(A) Bladder, ureters and urethra of a 13-weeks human female fetus. White lines depict the segment of the female urethra that was xenografted into DHT- treated and untreated castrated mouse hosts. (B) Section of a 15-week human fetal bladder neck prior to grafting.

Figure 20.

Xenograft of a 12-week human fetal female urethra grown for 8 weeks in a castrated DHT-treated host (A-C) immunostained for KRT19, KRT7 and TP63 as indicated. Xenografts of a 13-week human fetal female urethra grown for 8 weeks in a castrated DHT-treated host (D-F) immunostained for KRT19, KRT7 and TP63 as indicated. Arrows in (C)) depict pockets of TP63-negative epithelial cells in areas of incipient canalization.

Figure 21.

A 12-week human fetal female urethra grown for 8 weeks in a castrated DHT-treated host (A-C). Xenograft of a 13-week human fetal female urethra grown for 8 weeks in an untreated castrated host (D-F). (A, B, D, E) were immunostained for androgen receptor (AR). (C & F) were immunostained for NKX3.1. Arrows in (A) and (C) highlight solid epithelial cords, which are mostly devoid of AR (A) and NKX3.1 (C).

Figure 22.

A 12-week human fetal female urethra grown for 8 weeks in a castrated DHT-treated host immunostained for (A) prostatic acid phosphatase (PAP) and (B) prostatic specific antigen (PSA). PSA and PAP are expressed in ducts with lumina, but is reduced/absent in solid epithelial cords (arrowheads). Scale bar applies to both images.