Fig. 6

Double immunofluorescence staining for Luc/Nestin and Luc/Osteocalcin (DAPI for nucleuses). a In the Sys group, Luc⁺/Nestin⁺ cells (the red-yellow cells pointed out by red arrows), the systemically injected allogenic Luc-MSCs, had migrated to the fracture site. b In the Loc group, Luc⁺/Nestin⁺ cells (red arrows), the injected Luc-MSCs through local sites, remained at 5 weeks following the fracture. Luc⁺/Nestin⁻ cells (the green cells pointed out by white arrows in a, b) were observed, which meant that some injected Luc-MSCs had differentiated to other types of cells in both MSC injection groups. c, d Luciferase-positive cells were not observed in the PBS group (c) and the negative control (d), but Luc⁻/Nestin⁺ cells (white arrows in c), autogenetic MSCs, existed in the callus in the PBS control group. e, f Luc⁺/Osteocalcin⁺ cells (the red-yellow cells pointed out by red arrows) were observed both in the Sys group (e) and the Loc group (f), which meant that some injected Luc-MSCs had differentiated to osteoblasts. Luc⁺/Osteocalcin⁻ cells, the green cells (white arrows), were also found in MSC injection groups, which meant that some injected Luc cells remained at 5 weeks following the fracture. g, h Luciferase-positive cells were not observed in the PBS control group (g) and the negative control (h), but Luc⁻/Osteocalcin⁺ cells, autogenetic osteoblasts, were found in the callus. Scale bar: 20 μm. DAPI 4′,6-diamidino-2-phenylindole, Luc-MSC Luciferase labeled mesenchymal stem cell, MSC mesenchymal stem cell, PBS phosphate-buffered saline