Fig. 1A–C.

Live donor isografts from R26A mice were transplanted into wild type β-gal negative mouse femurs. (A) H&E/alcian blue staining (original magnification at 4X) demonstrates live Rosa 26 isograft in a wild type donor produces robust endochondral and intramembranous bone formation at the cortical bone junction. Host side and graft side at the junctions are marked as * (host) and # (graft). (B) X-gal staining of adjacent sections demonstrates the majority of cartilage and bone overlying the donor graft stained positive for β-gal (blue), indicating donor origin. (C) Magnified images (20X) of the boxed region in B demonstrated nearly all the osteocytes (arrow) in newly formed bone overlying donor bone graft stained β-gal positive (blue), indicating donor origin. (A1–A5) Photomicrographs (original magnification 20X) of X-Gal-stained sections show the progression of donor periosteal progenitor cells (blue) through the endochondral bone formation from Day 1 to Day 10. (B1–B5) X-Gal (blue) and alkaline phosphatase (AP) (red) double staining demonstrate the differentiation of β-gal-positive cells from Day 1 to Day 10.