Figure 3.

In vitro and in vivo functional assessment of WT and Cd34^−/− MPCs. (A) Representative images showing WT and Cd34^−/− differentiated MPCs forming multinucleated myotubes (MyHC, green; Hoechst, blue). Scale bar=65 μm. (B) Fusion index (percent of total nuclei found in myotubes) for WT and Cd34^−/− myotubes. Error bars represent ± SEM for n=3 mice with 15 random fields of view per animal. (C) Schematic of the transplant experiment. (D) Direct enumeration and comparison of WT LacZ⁺ donor-derived myofibers used as internal standards in transplantation experiments. Bar graphs displaying the relative amount of LacZ⁺ fibers injected with WT/GFP⁺ or Cd34^−/−/GFP⁺ MPCs. Error bars represent ± SEM for n=3 mice. (E) Representative image showing engraftment of WT/GFP⁺ and Cd34^−/−/GFP⁺ MPCs 3 weeks following injection into non-damaged WT recipients (GFP, green; Laminin, red). Scale bar=95 μm. (F) Quantification of engraftment. GFP⁺ donor-derived myofibers were counted and normalized to the number of LacZ⁺ donor fibers. Ratios were then normalized to WT controls. Error bars represent ± SEM for n=3–5. (G) MPCs from WT and Cd34^−/− mice on a Myf5^LacZ background were sorted, cytospun, and stained for LacZ to assess β-galactosidase activity. Representative images displaying LacZ⁺ cells in both groups are shown. Scale bar=50 μm. (H) Frequency of LacZ⁺ cells in WT and Cd34^−/− sorted MPCs. Error bars represent ± SEM for n=3 mice.