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. Author manuscript; available in PMC: 2017 Mar 1.
Published in final edited form as: Bone. 2015 Dec 22;84:69–77. doi: 10.1016/j.bone.2015.12.010

Figure 4. Contribution of endogenous αSMA and Pax7 labeled muscle cells to heterotopic ossification.

Figure 4

(A) Heterotopic ossification was induced by intramuscular injection of BMP2, with cell labeling initiated at different time points by tamoxifen (Tmx) injection(s). Cell contribution was evaluated histologically after 11 days. (B) αSMA-labeled cells contribute to multiple lineages within the ossicle. tdTomato expression is evident in osteoblasts (C), indicated by co-expression of Col2.3GFP (arrowheads), and chondrocytes (D), indicated by toluidine blue staining and morphology (D'). Fibrous tissue is also labeled. (E) Pax7 labeled cells contribute to muscle, but not heterotopic bone or cartilage tissue. Both images are from animals that received tamoxifen on the day of BMP2 injection. Quantification of the contribution of labeled cells to (F) osteoblasts and (G) chondrocytes in heterotopic bone indicates that αSMACreERT2 labels a significant proportion of bone lineage cells, while Pax7 labels very few. The days on the x-axis indicate the timing of tamoxifen administration in relation to BMP2 administration (Day 0). The n values on (F) represent the number of ossicles analyzed (1 ossicle/mouse) in each group, and also apply to (G). Scale bars represent 100μm (B, E) or 50μm (C, D). Abbreviations: ch, chondrocytes; f, fibrous tissue; m, muscle; ob, osteoblasts.