Novel differences in gene expression and functional capabilities of myofibroblast populations in idiopathic pulmonary fibrosis

Sinead M Walsh, Julie C Worrell, Aurelie Fabre, Boris Hinz, Rosemary Kane, Michael P Keane

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial pneumonia that is characterized by excessive fibroproliferation. Key effector cells in IPF are myofibroblasts that are recruited from three potential sources: resident fibroblasts, fibrocytes and epithelial cells. We hypothesized that IPF myofibroblasts from different sources of origin displayed unique genetic profiles and distinct functional characteristics. Primary human pulmonary fibroblasts (normal and IPF), fibrocytes and epithelial cells were activated into myofibroblasts using the pro fibrotic factors TGF β and TNF α. The resulting myofibroblasts were characterized using cell proliferation, soluble collagen, ELISA and contractility assays, and human fibrosis PCR arrays. Genes of significance were validated in whole human lung and validated by immunohistochemistry on human lung sections. Fibroblast-derived myofibroblasts exhibited the highest expression increase in pro fibrotic genes, and genes involved in extracellular matrix remodelling and signal transduction. Functional studies demonstrated that myofibroblasts derived from fibrocytes expressed most soluble collagen and CCL18 but were least proliferative of all myofibroblast progeny. Activated IPF fibroblasts displayed highest contraction and highest levels of CCL2 production. This study has identified novel differences in both gene expression and functional characteristics in different myofibroblast populations. Further investigation into the myofibroblast phenotype may lead to potential therapeutic targets in the future field of IPF research.