SDF-1β promotes BMSC-mediated new bone formation following direct tibial transplantation in irradiation-preconditioned animals. Representative combined DIC/fluorescence micrographs of the proximal tibia marrow space (coronal sections through the center of the diaphysis) 4 weeks post-transplantation. (A) Vehicle-transplanted (right) tibiae. (B) Tet-Off-SDF-1β (−Dox), (C) Tet-Off-SDF-1β (+Dox), and D) Tet-Off-EV BMSC-transplanted (left) tibiae at 1.32 × 107 cells/ml. A-D1,2) GFP-positive cells lining trabecular structures and embedded in the bone matrix (arrows) (A: adipocyte, M: marrow, T: trabecular bone, 20X, bar 20 μm, GFP = green, DAPI = blue, n = 5/Tet-Off-SDF-1β (−Dox); n = 5/Tet-Off-SDF-1β (+Dox); n = 10/Tet-Off-EV).