Abstract
The periosteum is the major source of cells involved in fracture healing. We sought to characterize progenitor cells and their contribution to bone fracture healing. The periosteum is highly enriched for progenitor cells, including Sca1+ cells, CFU-F and label-retaining cells compared to the endosteum and bone marrow. Using lineage tracing, we demonstrate that αSMA identifies long-term, slow-cycling, self-renewing osteochondroprogenitors in the adult periosteum that are functionally important for bone formation during fracture healing. In addition, Col2.3CreER-labeled osteoblast cells contribute around 10% of osteoblasts, but no chondrocytes in fracture calluses. Most periosteal osteochondroprogenitors following fracture, can be targeted by αSMACreER. Previously identified skeletal stem cell populations were common in periosteum, but contained high proportions of mature osteoblasts. We have demonstrated that the periosteum is highly enriched for skeletal progenitor cells and there is heterogeneity in the populations of cells that contribute to mature lineages during periosteal fracture healing.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Supported by: This work has been supported by Connecticut Stem Cell grant 14-SCA-UCHC-02, the Health Research Council of New Zealand Sir Charles Hercus Fellowship, and the American Society for Bone and Mineral Research Rising Star Award to B.G.M; Connecticut Regenerative Medicine Research Fund grant 16-RMB-UCHC-10 and NIH/NIAMS grants AR055607 and AR070813 to I.K.
Results have been reorganized and new data added: - New Figure 1 was previously Figure 3, with addition of diagrams to improve clarity of the experimental design. Some panels became Figure 8A-B. - New Figure 2 contains data previously presented in Figures 1A-B and 4. New data on CD200 expression has been added to Figure 2A. We have added panel D to figure supplement 2. - Additional novel data on single cell expression is presented in Figure 3 and supplements. - New Figure 4 was previously Figure 2. Additional annotation has been added to Supplement 1. Supplement 2 was previously part of Figure 4(H-K). - The majority of data in Figure 5 is new experimental data evaluating the Chan group's SSC and BCSP populations in adult animals. Similar data was presented in the old Figure 1C-E. - New data demonstrating self-renewal of αSMA-labeled progenitors following secondary fracture was added to Figure 6 that also contains data from the previous Figure 4F-G. - New Figure 7 has additional data as requested by the reviewers and is added to data presented as the old Figure 5. - New results on PDGFRα have been presented in Figure 8 that also contains the Col2.3CreER lineage tracing data that was previously in old Figure 3. - We have added the Key Resources Table and removed redundant information from the methods section.