CXCL12 and Duchenne muscular dystrophy: In DMD subjects, fibroblast clusters Fb 1, 2, and 4 were expanded (Supplementary Fig. 22), and Fb 1 and Fb 2 expressed high levels of CXCL12, which encodes a chemokine known to recruit macrophages and T cells to muscle and is required for muscle regeneration45,46 (Supplementary Data 10).