CTX-injury and muscular dystrophy activate Lin- SP cells <i>in vivo</i> and alter their <i>in vitro</i> proliferation and morphology.

<p><b>A</b>: Histological comparison of tissue sections from wild type (WT), CTX-injured (CTX), and <i>mdx^5cv</i> (MDX) tibialis anterior muscle stained with Hematoxylin and Eosin. Wild type muscle shows closely apposed muscle fibers with peripherally located nuclei. CTX-injured muscle at 3 days post-injection has only a few degenerating myofibers surrounded by large numbers of mononuclear cells. Muscle from 8 week old <i>mdx^5cv</i> mice shows areas of active regeneration (white arrow), and areas of muscle degeneration with accumulations of inflammatory cells (green arrow). Scale bar = 50 μm. <b>B</b>: Comparison of the number of Lin-SP cells isolated by FACS per gram of muscle from wild type, CTX-injured and <i>mdx^5cv</i> mice. Asterisks indicate a significant difference (p<0.01, Student's t-test) from wild type muscle. <b>C</b>: Quantification of <i>in vitro</i> Lin- SP cell proliferation using the Alamar Blue vital dye assay. Asterisks indicate a significant difference (p<0.001, linear regression analysis) from wild type muscle. <b>C</b>: Phase pictures of wild type, CTX and <i>mdx^5cv</i> Lin- SP cells at days 3, 8 and 11 in culture showing differences in cell adhesion, proliferation and morphology. Scale bar = 50 μm.