Figure 4

Attenuation of bleomycin-induced pulmonary fibrosis by prominin-1⁺ cells is stage-specific. Expanded prominin-1-positive cells were isolated using magnetic cell sorting and transplanted into recipient mice by intratracheal injection at different time points after bleomycin instillation. Lung sections were analyzed 21 days after bleomycin instillation by hematoxylin and eosin (H&E) for excessive non-parenchymal infiltrates and Masson's trichrome staining for collagen I deposition (blue). Control mice injected with bleomycin developed severe pulmonary fibrosis (A). Administration of prominin-1⁺ cells 2 hours after bleomycin treatment protected the mice from fibrosis (B). Mice receiving prominin-1⁺ cells 24 hours (C), 3 days (D), 7 days (E) or 14 days (F) after bleomycin challenge failed to protect from pulmonary fibrosis. Magnifications: x100. Microphotographs from one independent experiment are shown for each time point. For quantification see in Additional file 1, Figure S1.