Fig. 2. Deletion of PDGFRβ^fl/fl in progenitor cells improves fracture healing.

Deleting of PDGFRβ in αSMA osteoprogenitors was induced by injecting tamoxifen on the day of femur fracture and 2 DPF. a Representative safranin O images of Cre⁻ and Cre⁺ fractured femurs 7 DPF. Increased callus size with increased cartilage area is present in Cre⁺ animals. Safranin O staining sections were analyzed on 7 and 12 DPF and von Kossa staining on 12 DPF. ImageJ was used to evaluate callus, cartilage and mineralized area. Cre⁻ n = 7, Cre⁺ n = 10 for day 7, and Cre⁻ n = 9, Cre⁺ n = 11 for day 12. Scale bar 1 mm. b PDGFRβ deletion in αSMA osteoprogenitors leads to changes in callus bone mass (Cre⁻ n = 6, Cre⁺ n = 10) and (c) stiffness 21 DPF (Cre⁻ n = 6, Cre⁺ n = 8). At 42 DPF there are no differences in structural or biomechanical femur properties (Cre⁻ n = 5, Cre⁺ n = 5). d Oc.S/BS and N.Oc/B.Pm are increased 21 DPF in Cre⁺ healing femurs (Cre⁻ n = 8, Cre⁺ n = 17). Values are expressed as mean ± s.e.m. *p < 0.05, **p < 0.01 ***p < 0.001. Statistical test: an unpaired two-tailed Students t-test. Oc.S/BS osteoclast surface per bone surface, N.Oc/B.Pm osteoclast number per bone perimeter.