Fig. 5. SP cells do not contribute to sub-cutaneous tracheal grafts. Analysis of sections of normal mouse trachea (A) by H&E staining show an intact epithelial layer. De-nuded mouse tracheas (B) show no presence of epithelial cells. (C) De-nuded tracheas instilled with 10⁵ primary epithelial cells developed an intact epithelial layer after sub-cutaneous grafting for 9 days. (D) Grafts that were seeded with 10⁵ C57Bl/6 tracheal epithelial cells and 2x10⁴ ROSA26 bone marrow SP cells showed re-epithelialisation of the trachea at 42 days post subcutaneous grafting. However, as shown by X-gal staining of the sub-cutaneous graft, the bone marrow SP cells did not contribute to the re-epithelialisation of the graft after 42 days as no blue ROSA26-derived cells were observed (E). Bar, 50 µM.