Epithelial-to-mesenchymal transition in fibrosis: Collagen type I expression is highly upregulated after EMT,but does not contribute to collagen deposition |
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Authors: | Nynke A Hosper Paul P van den Berg Saskia de Rond Eliane R Popa Martijn J Wilmer Rosalinde Masereeuw Ruud A Bank |
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Institution: | 1. Department of Pathology and Medical Biology, Medical Biology Section, University Medical Centre Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands;2. Department of Obstetrics and Gynecology, University Medical Centre Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands;3. Department of Pharmacology and Toxicology, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands |
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Abstract: | The hallmark of fibrosis is an accumulation of fibrillar collagens, especially of collagen type I. There is considerable debate whether in vivo type II epithelial-to-mesenchymal transition (EMT) is involved in organ fibrosis. Lineage tracing experiments by various groups show opposing data concerning the relative contribution of epithelial cells to the pool of myofibroblasts. We hypothesized that EMT-derived cells might directly contribute to collagen deposition. To study this, EMT was induced in human epithelial lung and renal cell lines in vitro by means of TGF-β1 stimulation, and we compared the collagen type I (COL1A1) expression levels of transdifferentiated cells with that of myofibroblasts obtained by TGF-β1 stimulation of human dermal and lung fibroblasts. COL1A1 expression levels of transdifferentiated epithelial cells appeared to be at least one to two orders of magnitude lower than that of myofibroblasts. This was confirmed at immunohistochemical level: in contrast to myofibroblasts, collagen type I deposition by EMT-derived cells was not or hardly detectable. We postulate that, even when type II EMT occurs in vivo, the direct contribution of EMT-derived cells to collagen accumulation is rather limited. |
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