Abstract 20095: Role of Mirnas in Heme Oxygenase-1 Mediated Impairment of Myoblast Differentiation
Heme oxygenase-1 (HO-1) is a cytoprotective enzyme, whose overexpression has been suggested to improve cell survival in cell-based therapies. Our aim was to check the effect of HO-1 on myoblast differentiation. We found that formation of myotubes was inhibited in satellite cells isolated from HO-1-deficient mice, as evidenced by cell morphology and reduced expression of myogenin, MyoD, and muscle-specific micro-RNAs (myomirs). Accordingly, ∼10-fold upregulation of HO-1 activity in C2C12-GFP-Luc myoblast line overexpressing HO-1, improved cell proliferation and survival, while inhibited differentiation, as indicated by reduced myotube formation, and downregulation of creatine phosphokinase, MyoD, myogenin, and myosin (Fig. 1A). These effects were fully reversed by pharmacological (tin protoporphyrin) or genetic (siRNA) HO-1 inhibition. Accordingly, effects of HO-1 overexpression were mimicked by HO-1 inducer (cobalt protoporphyrin) or HO-1 products (iron ions or CO). After injection to murine gastrocnemius muscle the number of control C2C12 myoblasts remained stable for 3 weeks and, as proved by immunohistochemical staining for GFP, they contributed to formation of muscle fibers. In contrast, HO-1 overexpressing cells proliferated continuously, and formed big, hyperplastic, undifferentiated tumors (Fig. 1B). HO-1 upregulation reduced total pool of cellular pre-miRNAs and miRNAs, and downregulated miRNA processing proteins, Lin28 and DGCR8. Specifically, it inhibited the myomirs, miR-1, −133a, −133b, and −206, and augmented the production of SDF-1. Effects of HO-1 were mocked by treatment of cells with SDF-1 protein and reversed by overexpression of miR133a, −133b or −206. In conclusion, HO-1 inhibits differentiation of myoblasts in a SDF-1 and myomir-dependent manner. Thus, although HO-1 increases the cell survival, its influence on myoblast differentiation can be a drawback in potential therapeutic application of HO-1 overexpression.
- © 2010 by American Heart Association, Inc.