PAI-1-regulated miR-21 defines a novel age-associated fibrogenic pathway in muscular dystrophy

• Published in: The Journal of cell biology Vol. 196; no. 1; pp. 163 - 175
• Main Authors: Ardite, Esther, Perdiguero, Eusebio, Vidal, Berta, Gutarra, Susana, Serrano, Antonio L, Muñoz-Cánoves, Pura
• Format: Journal Article
• Language: English
• Published: United States Rockefeller University Press 09-01-2012; The Rockefeller University Press
• Subjects: Adolescent; Age Factors; Animals; Cell Proliferation; Cellular biology; Child; Collagen - metabolism; Female; Fibrosis - genetics; Gene expression; Genetics; Homeostasis; Humans; Male; Mice; Mice, Knockout; MicroRNAs - physiology; Muscular Dystrophies - genetics; Musculoskeletal system; Proto-Oncogene Proteins c-akt - metabolism; Rodents; Serpin E2 - genetics; Serpin E2 - metabolism; Serpin E2 - physiology; Signal Transduction; Transforming Growth Factor beta - metabolism; Transforming Growth Factor beta - physiology
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.201105013

Disruption of skeletal muscle homeostasis by substitution with fibrotic tissue constitutes the principal cause of death in Duchenne muscular dystrophy (DMD) patients, yet the implicated fibrogenic mechanisms remain poorly understood. This study identifies the extracellular PAI-1/urokinase-type plasminogen activator (uPA) balance as an important regulator of microribonucleic acid (miR)-21 biogenesis, controlling age-associated muscle fibrosis and dystrophy progression. Genetic loss of PAI-1 in mdx dystrophic mice anticipated muscle fibrosis through these sequential mechanisms: the alteration of collagen metabolism by uPA-mediated proteolytic processing of transforming growth factor (TGF)-β in muscle fibroblasts and the activation of miR-21 expression, which inhibited phosphatase and tensin homologue and enhanced AKT signaling, thus endowing TGF-β with a remarkable cell proliferation-promoting potential. Age-associated fibrogenesis and muscle deterioration in mdx mice, as well as exacerbated dystrophy in young PAI-1(-/-) mdx mice, could be reversed by miR-21 or uPA-selective interference, whereas forced miR-21 overexpression aggravated disease severity. The PAI-1-miR-21 fibrogenic axis also appeared dysregulated in muscle of DMD patients, providing a basis for effectively targeting fibrosis and muscular dystrophies in currently untreatable individuals.