Skeletal muscle regeneration is defective in Plg-deficient mice.

(A) Glycerol-induced injuries result in impaired skeletal muscle regeneration of Plg-deficient mice. Frozen sections of muscles from WT and Plg-deficient mice were stained with H/E after 2, 4, 7, 10, 30, and 50 days AI, as indicated. Contralateral control muscles were also stained with H/E (0 days AI). In WT mice, advanced regeneration is visible after 4 days, and regeneration is complete after 10 days. In Plg-deficient mice, a regeneration defect is already visible after 4 days AI but is most striking after 10 days. In WT mice, virtually no sign of the previous injury was detectable after 30 and 50 days, except for the centrally located myonuclei. Original magnifications × 400. (B) Persistence of MHCd-positive myofibers 10 days after glycerol injury in Plg-deficient mice. Cryostat frozen sections from WT and Plg-deficient mice were reacted with a monoclonal antibody against MHCd at 4 and 10 days AI, as indicated. Large numbers of MHCd-expressing myofibers are visible in regenerating muscle of Plg-deficient mice 4 and 10 days after intramuscular glycerol injection. In WT mice, MHCd-positive fibers are observed 4 days AI, whereas no MHCd-expression is detected 10 days AI. Original magnification × 400.