Akitoshi Hara1,2, Hiroki Kobayashi1,3, Naoya Asai1,4, Shigeyoshi Saito5, Takahiro Higuchi5, Katsuhiro Kato2, Takahiro Okumura2, Yasuko K Bando2, Mikito Takefuji2, Yasuyuki Mizutani1,6, Yuki Miyai1, Shoji Saito7, Shoichi Maruyama7, Keiko Maeda6, Noriyuki Ouchi2, Arata Nagasaka8, Takaki Miyata9, Shinji Mii1, Noriyuki Kioka10, Daniel L Worthley3, Toyoaki Murohara2, Masahide Takahashi1,4, Atsushi Enomoto1. 1. From the Department of Pathology (A.H., H.K., N.A., Y. Mizutani, Y. Miyai, S. Mii, M. Takahashi, A.E.), Nagoya University Graduate School of Medicine, Japan. 2. Department of Cardiology (A.H., K.K., T.O., Y.K.B., M. Takefuji, N.O., T. Murohara), Nagoya University Graduate School of Medicine, Japan. 3. School of Medicine, University of Adelaide and South Australian Health and Medical Research Institute, Adelaide (H.K., D.L.W.). 4. Division of Molecular Pathology, Center for Neurological Disease and Cancer (N.A., M. Takahashi), Nagoya University Graduate School of Medicine, Japan. 5. Department of Biomedical Imaging, National Cardiovascular and Cerebral Research Center, Osaka, Japan (Shigeyoshi Saito, T.H.). 6. Department of Gastroenterology and Hepatology (Y. Mizutani, K.M.), Nagoya University Graduate School of Medicine, Japan. 7. Department of Nephrology (Shoji Saito, S. Maruyama), Nagoya University Graduate School of Medicine, Japan. 8. Division of Anatomy, Department of Human Development and Fostering, Meikai University School of Dentistry, Saitama, Japan (A.N.). 9. Department of Anatomy and Cell Biology (T. Miyata), Nagoya University Graduate School of Medicine, Japan. 10. Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Japan (N.K.).
Abstract
RATIONALE: Myofibroblasts have roles in tissue repair following damage associated with ischemia, aging, and inflammation and also promote fibrosis and tissue stiffening, causing organ dysfunction. One source of myofibroblasts is mesenchymal stromal/stem cells that exist as resident fibroblasts in multiple tissues. We previously identified meflin (mesenchymal stromal cell- and fibroblast-expressing Linx paralogue), a glycosylphosphatidylinositol-anchored membrane protein, as a specific marker of mesenchymal stromal/stem cells and a regulator of their undifferentiated state. The roles of meflin in the development of heart disease, however, have not been investigated. OBJECTIVE: We examined the expression of meflin in the heart and its involvement in cardiac repair after ischemia, fibrosis, and the development of heart failure. METHODS AND RESULTS: We found that meflin has an inhibitory role in myofibroblast differentiation of cultured mesenchymal stromal/stem cells. Meflin expression was downregulated by stimulation with TGF (transforming growth factor)-β, substrate stiffness, hypoxia, and aging. Histological analysis revealed that meflin-positive fibroblastic cells and their lineage cells proliferated in the hearts after acute myocardial infarction and pressure-overload heart failure mouse models. Analysis of meflin knockout mice revealed that meflin is essential for the increase in the number of cells that highly express type I collagen in the heart walls after myocardial infarction induction. When subjected to pressure overload by transverse aortic constriction, meflin knockout mice developed marked cardiac interstitial fibrosis with defective compensation mechanisms. Analysis with atomic force microscopy and hemodynamic catheterization revealed that meflin knockout mice developed stiff failing hearts with diastolic dysfunction. Mechanistically, we found that meflin interacts with bone morphogenetic protein 7, an antifibrotic cytokine that counteracts the action of TGF-β and augments its intracellular signaling. CONCLUSIONS: These data suggested that meflin is involved in cardiac tissue repair after injury and has an inhibitory role in myofibroblast differentiation of cardiac fibroblastic cells and the development of cardiac fibrosis.
RATIONALE: Myofibroblasts have roles in tissue repair following damage associated with ischemia, aging, and inflammation and also promote fibrosis and tissue stiffening, causing organ dysfunction. One source of myofibroblasts is mesenchymal stromal/stem cells that exist as resident fibroblasts in multiple tissues. We previously identified meflin (mesenchymal stromal cell- and fibroblast-expressing Linx paralogue), a glycosylphosphatidylinositol-anchored membrane protein, as a specific marker of mesenchymal stromal/stem cells and a regulator of their undifferentiated state. The roles of meflin in the development of heart disease, however, have not been investigated. OBJECTIVE: We examined the expression of meflin in the heart and its involvement in cardiac repair after ischemia, fibrosis, and the development of heart failure. METHODS AND RESULTS: We found that meflin has an inhibitory role in myofibroblast differentiation of cultured mesenchymal stromal/stem cells. Meflin expression was downregulated by stimulation with TGF (transforming growth factor)-β, substrate stiffness, hypoxia, and aging. Histological analysis revealed that meflin-positive fibroblastic cells and their lineage cells proliferated in the hearts after acute myocardial infarction and pressure-overload heart failuremouse models. Analysis of meflin knockout mice revealed that meflin is essential for the increase in the number of cells that highly express type I collagen in the heart walls after myocardial infarction induction. When subjected to pressure overload by transverse aortic constriction, meflin knockout mice developed marked cardiac interstitial fibrosis with defective compensation mechanisms. Analysis with atomic force microscopy and hemodynamic catheterization revealed that meflin knockout mice developed stiff failing hearts with diastolic dysfunction. Mechanistically, we found that meflin interacts with bone morphogenetic protein 7, an antifibrotic cytokine that counteracts the action of TGF-β and augments its intracellular signaling. CONCLUSIONS: These data suggested that meflin is involved in cardiac tissue repair after injury and has an inhibitory role in myofibroblast differentiation of cardiac fibroblastic cells and the development of cardiac fibrosis.