Fig. 3

IF analysis of the distribution of LRCs and co-expression of SC markers in sagittal sections of postnatal day 5 (P5) mouse prostates. a A cartoon of a sagittal P5 section; bladder and urethra (indicated in yellow), stroma (light blue), sphincter (Sp; grey), vas deferens (VD) and ejaculatory duct (Ed) (both black), ejaculatory sinus (ES; orange), seminal vesicle (SV; brown), and the ventral prostate (VP; dark blue), dorso-lateral prostate (DLP; green), and anterior prostate (AP; red). b–d are composite images of serial sagittal HTX stained sections, where ducts draining from a specific lobe are indicated by the addition of a ‘d’ to the lobular abbreviation. Frozen sections were subjected to antibodies against Sca-1 (red) and CK14 (green) (e, f), CD133 (green) (g), TROP-2 (green) and BrdU (red) (h), Sca-1 (red) and BrdU (green) (i), CD44 (red) and BrdU (green) (j–l), c-kit (red) and BrdU (green) (m, o), c-kit (red) and Sca-1 (green) (n), and KRT-7 (red) and BrdU (green) (p). Sca-1 (e, f, i) and TROP-2 (h) were highly expressed in basal and luminal cells of ducts draining into the ES and urethra. The mesenchyme surrounding these proximal ducts was positive for CD133 expression (g). Sagittal sections clearly demonstrated that LRCs were more numerous and more strongly labeled in terminal draining ducts in or close to where the ES fuses with the urethra (h, j, k), whereas more distal structures contained fewer and less bright LRCs (h, k). The number and intensity of epithelial LRCs further abruptly decreased at the border of the Sp, where the ducts cross to enter the prostate lobes (i, p; arrows indicate luminal, whereas arrowheads indicates a basal location). At this border, many putative SC markers changed their distribution pattern in both epithelium and stroma, including Sca-1 (i, n), TROP-2 (h), CD44 (k), c-kit (n), and KRT-7 (p). Whereas Sca-1 (inset in (e) shows rare luminal Sca-1 expression of the VP from a serial section close to (e)), c-kit (n), and KRT-7 (p) expression was rare in distal epithelium of all lobes, we found TROP-2 to be more commonly expressed in the VP when compared to other lobes (h). CD133 was upregulated in the distal DLP (arrow, g) of P5 prostates, and whereas CD44 showed high expression in distal epithelium of the DLP (k) and AP (arrows and inset in k), CD44 was downregulated in distal luminal cells of the VP (k, l), but not in the basal cells (arrows, l). Additionally, VP ducts showed upregulation of CD44 in the basal cell layer (j, k) in P5 prostates. LRCs strongly reactive for BrdU in the prostate epithelium were found to express the putative SC markers TROP-2 (h), Sca-1 (i), CD44 (j–l), c-kit (m,o), and KRT-7 (p). Counterstaining was either HTX (IHC) or DAPI (IF). Scale bars = 25 μm (i, o, p), 50 μm (h, j, l –n), and 100 μm (e–g, k). b–e are composite images of several micrographs