miRNA and Muscle Link
Also presenting at the upcoming conference in Germany will be Christian Thirion, Ph.D., CSO, Sirion Biotech. Dr. Thirion’s talk will focus on “Disregulated microRNAs—Novel Therapeutic Targets in Muscular Dystrophies.”
He notes that tumor necrosis factor alpha (TNF-α) is a prototypical inflammatory cytokine and a well-known mechanism for negating fusion in muscle cells. The injured muscles must be regenerated by myoblasts.
It is also well known that microRNAs are central regulators of muscle differentiation and that several cytokines might counter miRNA expression. In fact, Dr. Thirion points to 126 citations in the literature since 2005 linking miRNA and muscle.
Using a TaqMan low density array analysis, Dr. Thirion’s group found a number of miRNAs that were significantly upregulated and others that were significantly downregulated. When TNF-α was added, two key miRNAs in the previously upregulated group were downregulated. These were has-miR-133b and has-miR-206.
In addition TNF-a strongly upregulated miR-155, a microRNA linked to inflammation. When Agilent’s microarray analysis was substituted for TaqMan and TNF-α was added, all four downregulated miRNAs are muscle specific. Using the SC5 mouse cellular model, analysis confirmed that the effect of TNF-α is conserved on muscle-specific miRNAs across species.
From this work, the Sirion researchers concluded that TNF-α specifically acts on muscle-specific microRNA expression and that inhibition of muscle-specific microRNA expression is a potential disease mechanism in dystrophic muscle.
The group aims to further study the effects of cytokines/growth factors on microRNA expression, develop a functional analysis for regulated microRNAs, and intervene therapeutically on disregulated microRNA in muscle tissue to rescue non-fusion phenotype in vitro by microRNA over-expression. Finally, Dr. Thirion hopes to proceed to proof-of concept in an animal model for muscular dystrophy.