Diseased muscles that lack dystrophin or laminin-alpha2 have altered compositions and proliferation of mononuclear cell populations.
BACKGROUND
Multiple types of mononucleate cells reside among the multinucleate myofibers in skeletal muscles and these mononucleate cells function in muscle maintenance and repair. How neuromuscular disease might affect different types of muscle mononucleate cells had not been determined. In this study, therefore, we examined how two neuromuscular diseases, dystrophin-deficiency and laminin-alpha2-deficiency, altered the proliferation and composition of different subsets of muscle-derived mononucleate cells.


METHODS
We used fluorescence-activated cell sorting combined with bromodeoxyuridine labeling to examine proliferation rates and compositions of mononuclear cells in diseased and healthy mouse skeletal muscle. We prepared mononucleate cells from muscles of mdx (dystrophin-deficient) or Lama2-/- (laminin-alpha2-deficient) mice and compared them to cells from healthy control muscles. We enumerated subsets of resident muscle cells based on Sca-1 and CD45 expression patterns and determined the proliferation of each cell subset in vivo by BrdU incorporation.


RESULTS
We found that the proliferation and composition of the mononucleate cells in dystrophin-deficient and laminin-alpha2-deficient diseased muscles are different than in healthy muscle. The mdx and Lama2-/- muscles showed similar significant increases in CD45+ cells compared to healthy muscle. Changes in proliferation, however, differed between the two diseases with proliferation increased in mdx and decreased in Lama2-/- muscles compared to healthy muscles. In particular, the most abundant Sca-1-/CD45- subset, which contains muscle precursor cells, had increased proliferation in mdx muscle but decreased proliferation in Lama2-/- muscles.


CONCLUSIONS
The similar increases in CD45+ cells, but opposite changes in proliferation of muscle precursor cells, may underlie aspects of the distinct pathologies in the two diseases.
Girgenrath
Mahasweta
M
Neuromuscular Biology & Disease Group, Boston Biomedical Research Institute, 64 Grove Street, Watertown MA 02472, USA. girgenrath@bbri.org
Kostek
Christine A
CA
Miller
Jeffrey Boone
JB
D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000950:Antigens, Ly / Q000378:metabolism; D001973:Bromodeoxyuridine; D002452:Cell Count; D049109:Cell Proliferation; D004195:Disease Models, Animal; D016189:Dystrophin / Q000172:deficiency*; D005434:Flow Cytometry / Q000379:methods; D005786:Gene Expression Regulation / Q000235:genetics; D007797:Laminin / Q000172:deficiency*; D017493:Leukocyte Common Antigens / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D018345:Mice, Knockout; D032342:Muscle Cells / Q000473:pathology*; D018482:Muscle, Skeletal; D009135:Muscular Diseases / Q000235:genetics / Q000473:pathology* / Q000503:physiopathology
D000950:Antigens, Ly; D016189:Dystrophin; D007797:Laminin; C074650:Ly6a protein, mouse; D008565:Membrane Proteins; C102645:laminin alpha 2; D017493:Leukocyte Common Antigens; D001973:Bromodeoxyuridine