Resistance exercise improves function and reduces the expression of inflammation and fibrosis genes in skeletal muscle of autoimmune myositis patients.

To better understand the beneficial effects of physical activity on autoimmune myositis, we carried out a resistance exercise (RE) training program in patients diagnosed with Polymyositis (PM) or Dermatomyositis (DM). In order to determine the molecular mechanisms underlying the effects of exercise, muscle biopsies were obtained and subjected to a genome‐wide analysis of gene expression. Eight patients underwent a whole body RE training program consisting of five different exercises, three times a week for seven weeks. Muscles biopsies were obtained from the vastus lateralis muscle before training and one week following the last exercise session. RNA was prepared for expression profiling using Affymetrix Human Genome U133 Plus 2 chips. Absolute expression values were calculated using MAS.5 and data analysis using Gene Spring. Statistical significance was determined at >1.5 fold and p<0.05. RE resulted in significant improvements in muscle strength (10 RM) in four muscle groups. Improvement in muscle performance were accompanied by a reduction in the expression of genes involved in inflammation (MHC‐1F, HMGB1, IRAK3, IL2R, IL10R), fibrosis (FGF1, TGFβ1R, LTBP1, CTGF, LOXL, Col IαI, Vα and XIV α1), and protein degradation (UBE2J1, UBE3A, UBR2 and Cathepsin C). We conclude that regular physical activity can improve muscle function in PM and DM patients likely due to a reduction in fibrosis and inflammation as reflected by the corresponding changes in gene expression.