Fig. 2

PDGFRα reporter⁺ periosteal cells give rise to osteochondral cells within a fractured callus. a PDGFRα^mT/mG reporter animals (male, aged 2 mo) were administered TM, forelimb fracture was performed after 14 d, and an analysis was performed 1–30 d later. b Micro-CT 3D reconstructions at representative time points after fracture. c Representative tile scans of the whole forelimb at serial time points after fracture ranging from 0 to 30 d. The uninjured forelimb is shown for comparison. Nuclei, DAPI (4′,6-diamidino-2-phenylindole, blue). d Representative high-magnification images of PDGFRα reporter activity in the periosteum of unfractured or fractured bone (d 1–7). e High-magnification images of GFP⁺ cells in skeletal muscle adjacent to the fracture site (3 and 14 d). The dashed lines indicate the limit between the periosteum and muscle or bone. f Contribution of GFP⁺ cells in the cartilage of the fractured callus (7 and 14 d). g Contribution of GFP⁺ cells to new osteoblasts in the fractured callus (7–30 d). h Representative immunohistochemical staining of a PDGFRα^mT/mG fractured callus was performed 7 or 14 d after injury, including staining for aggrecan, osteocalcin (OCN), and CD31. i Percentages of mGFP⁺ chondrocytes/total chondrocytes and mGFP⁺ osteoblasts/total osteoblasts assessed at 7 and 14 d after injury. B bone, BM bone marrow, BV blood vessel, C cartilage, M skeletal muscle, PO periosteum. Scale bars: 500 μm (c) and 50 μm (d–h). n = 3 animals per group. The dot plots represent an individual animal, and the whisker plots indicate the mean and one-SD values. *P < 0.05, as assessed by two-tailed Student’s t tests