Characteristic pattern of skeletal muscle remodelling in different mouse strains

Muscular injury associated with local inflammatory reaction frequently occurs in sports medicine, but the individual response and capacity of regeneration vary among subjects. Inflammatory cytokines are probably implicated in activation of repair mechanisms by specifically influencing tissue microenvironment. This work aimed to compare muscle tissue repair in different mouse lineages. We used C57BL/6 and BALB/c mice genetically predisposed to either Type1 or Type2 cytokine production. The role of Type1 cytokines was also investigated in C57IFN-γ (IFNγ-KO) and C57IL-12 (IL12-KO) knockout mice. Participation of T lymphocytes was assessed in athymic BALB/c nude (nu/nu) mice. Muscular lesion was induced with bupivacaine injection in the Triceps brachii muscle. BALB/c mice showed marked collagen deposition and increased TGF-β mRNA content, contrasting with mild fibrosis observed in C57BL/6 mice. C57-IFNγ-KO mice, exhibited pronounced fibrosis, but IL12-KO collagen deposition was similar to that of C57. Twenty-four hours after lesion, C57BL/6 and BALB/c(nu/nu) presented numerous regenerating myofibres and marked increase of metalloprotease-9 activity compared with BALB/c. These data support that skeletal muscle remodelling is greatly influenced by the genetic backgrounds, shedding light on the molecular mechanisms influencing differential muscular remodelling and tissue regeneration among individuals.