Optimal concentration of mesenchymal stem cells for fracture healing in a rat model with long bone fracture

Figure 4 Assessment of histological scores for fracture healing at 6 wk post-fracture using hematoxylin and eosin staining (200 × magnification). A: The histological score was 5 in the groups injected with normal saline; B: The histological score was 5 in the groups injected with 2.5 × 10⁶ mesenchymal stem cells (MSCs); C: The histological score was 9 in the group injected with 5.0 × 10⁶ MSCs; D: The histological score was 10 in the group injected with 10.0 × 10⁶ MSCs. The black arrows indicate the fracture lines. c: Cartilage in the fracture area; wb: Woven bone; ib: Immature bone; mb: Mature bone.