Introduction: Cardiac fibrosis is the leading cause of myocardial dysfunction in patients with diabetes. Myofibroblast transformation is a key factor involved in fibrosis, and there is no effective treatment. We tested whether high glucose (HG) - induced myofibroblast transformation could be prevented by exosomes derived from mesenchymal stem cells (MSC).
Methods and Results: Fibroblasts were treated with either normal levels of glucose (NG, 5 mM) or high glucose (25 mM) for 48 hours. The expression of collagen I and α-SMC were used as markers for myofibroblast transformation. HG treatment led to increased mRNA expression of collagen I (2.3 fold) and α-SMC (2.5 fold), compared to fibroblasts treated with NG (p<0.05). The secreted collagen I protein levels were also increased in HG treated cells as determined by ELISA. In contrast, fibroblast proliferation (BrdU assay) and migration (wound scratch migratory assay) were not altered by HG. We used mannitol (25 mM) as osmotic control, which showed no effect on collagen I and α-SMC expression. To determine whether myofibroblast transformation can be prevented by exosome, MSC was prepared from bone marrow of 2-week old rats and exosome was isolated from MSC conditioned media by ultracentrifugation. MSC - derived exosome was examined by electron microscopy, and the expression of exosome marker CD63 was analyzed by Western blot and flow cytometry. Exosome treatment attenuated HG-induced myofibroblast transformation (reduced collagen I and α-SMC), accompanied by reduced expression of TGF-ß and pSmad2/3 (the key molecule of TGF-ß pathway) assessed by Western blot and immunostaining. Furthermore, exosome treatment did not alter cell proliferation (BrdU assay), cell survival (TUNEL assay) and migration (wound scratch migratory assay).
Conclusion: This study demonstrates that short term exposure of fibroblast to HG induces myofibroblast formation which was mediated by TGF-ß signaling pathway. Importantly, we showed that exosome treatment may be a novel therapeutic strategy to prevent HG-induced fibrosis.