Tracking of MSCs in vivo after transfection with a luciferase gene reporter vector pL-Luc-IH. Luciferase-positive cells were detected at 20× magnification in the spinal cord (A–E) and in the hypothalamus (F–J). Mice were injected with LUC-positive MSCs and sacrificed 24 and 48 h or 20 and 35 d after injection. Histology was performed on 5-µm sections with a mouse anti-luciferase antibody. DAPI (4’,6-diamidino-2-phenylindole) was used for cell nucleus detection. Upper panels show representative images of tissues collected 24 h (A, E), 48 h (B, F), 20 d (C, G) or 35 d (D, H) after injection. Quantification (E, J) was performed on a systematic random series of six sections per animal, every tenth coronal section (20 um), throughout the entire spinal cord and brain; data (means ± SEM) represent the number of positive cells/mm2. Eight MSC-treated mice were used. *p < 0.05 at least (ANOVA plus Bonferroni). Scale bar, 100 µm.