Figure 1: Expression of prostatic epithelial marker and phenotype at 4 and 8 days following tissue recombination. Neonatal spermatogonial stem cells (SSCs) isolated from 6-day-old green fluorescent protein (GFP+) mice were recombined with 16 days fetal wild-type urogenital sinus mesenchyme and grafted under the renal capsule of syngeneic nude male hosts for 4 ( a ) or 8 ( b and c ) days. Tissue recombinants expressed Nkx 3.1 (red staining), a prostatic epithelial marker, after 4 days of renal grafting ( a ). Tissue recombinants formed histologically identifiable prostatic ducts by 8 days ( b ), and the epithelium in the tissue recombinants was of SSC origin, as shown by GFP immunostaining ( b ) and the higher power view of these ducts in ( c ). The scale bars in the lower right corner of all photos = 10 μm. S: stroma; E: epithelium.