Fig. 9. EPCs colonise foetal gut and have the potential to generate neurons and glia. (A,B) DiI-labelled pieces of foetal and postnatal NLBs were grafted into the wall of gut dissected from Ret^k-/k- E11.5 mouse embryos and maintained in organotypic culture. A large number of neurons and glial cells were detected in the grafted gut (B) but were absent from control mutant gut (A). Arrow in B points to the site of NLB grafting in the stomach (s). Processing of guts for immunostaining resulted in loss of DiI fluorescence. (C-I) 20-30 foetal EPCs were grafted into the wall of wild-type (D-F) or Ret^k/k- (H-I) guts which were subsequently cultured for 14 days. C and G are non-grafted control guts. At the end of the culture period, explant sections were immunostained for GFP (C-I) and TuJ1 (C-E,G-I) or GFAP (F). Large numbers of GFP+ cells were detected in the grafted guts (arrows in D and H) but were absent from control guts (C,G). GFP+ cells could be detected at relatively large distances from the site of injection suggesting a considerable migratory ability of grafted cells. Neuronal progeny of EPCs (GFP+/TuJ1+ cells) were detected in grafted wild-type and RET-deficient guts (arrows in E and I). However, GFP+/GFAP+ cells were detected only in wild-type guts (arrows in F). Note the virtual absence of endogenous TuJ1 signal from sections of Ret^k-/k- guts (G). (J-N) Postnatal EPCs were also introduced into wild-type (J-L) and Ret^k- homozygous (M-N) guts. Analysis of sections from grafted guts at the end of the culture period indicated that GFP+ cells increased in numbers and colonised relatively large segments of the grafted guts (arrows in J and M point to GFP+ cells). GFP+/TuJ1+ cells were detected in wild-type and RET-deficient gut (arrows in K and N). However, GFP+/GFAP+ cells were only detected in wild-type guts (arrow in L). Arrowheads in D, H and J show the site of EPC grafting. s, stomach; i, intestine.