Figure 1. Rat stem Leydig cells (rSLCs) can transdifferentiate into prostatic epithelium (PE).

After 5 weeks of growth in vivo, GFP⁺-urogenital sinus mesenchyme (UGM) + rSLCs tissue recombinants developed into structures histologically resembling prostate and consisted of tubular structures lined by simple cuboidal epithelium supported by fibromuscular stroma (A, D, G, J, M, P). Critically, in GFP⁺-UGM + rSLCs grafts, the cuboidal epithelium (PE) was GFP⁻, while the stroma (S) was GFP⁺ (A, G), indicating that the epithelium was of rSLC origin. This contrasts with control GFP⁻-UGM + GFP⁺-urogenital sinus epithelium (UGE) tissue recombinants (B, E, H, K, N, Q) and host prostate (C, F, I, L, O, R), where GFP expression occurs only in epithelium (B, H) but not the stroma, or is seen in neither epithelium or stroma (C, I), respectively. In addition, the presumptive prostatic epithelium of rSLC origin robustly expressed a prostate epithelial-specific marker, NKX3.1 (J) that was also seen in GFP⁻-UGM + GFP⁺-UGE tissue recombinants (K) and host prostate (L). In the epithelium of GFP⁺-UGM + rSLCs grafts, dorsolateral prostate secretory protein (DLP) production was seen in the epithelium and lumens of the ducts (M), while androgen receptor (AR) was expressed in all cells of these grafts (P). Both the secretory protein (DLP) expression and AR expression in these grafts was identical to control GFP⁻-UGM + GFP⁺-UGE tissue recombinants (N, Q) and host prostate (O, R). Magnification bars in all panels are 50 µm. GFP, green fluorescent protein; DAPI, 4′,6-diamidino-2-phenylindole.