231 Decrease of Mitochondrial Fusion Protein MFN1 and Associated Myogenin Inhibition in Response to Severe Burn

Abstract Introduction Severe burn-induced muscle mass loss is primarily a result of protein degradation and insufficient myogenesis. Muscle precursor cells decrease and undergo increased apoptosis in response to burn. Mitochondrial dysfunction is a key factor in muscle atrophy after burn, and we recently found mitochondrial fusion protein Mfn1 was decreased in burn serum-stimulated myoblasts. The purpose of this study was to evaluate mitochondrial dynamics after burn. Methods Twenty-four adult male SD rats received a 40% TBSA. At 1, 3, and 7 days after burn, gastrocnemius was harvested for molecular analysis with Western blotting; 6 sham-burned rats served as controls. To identify the role of mitochondrial dynamics in muscle atrophy, we knocked out Mfn1 in murine myoblasts via a Crispr-Cas9 system with subsequent burn serum stimulation. Cells were extracted and analyzed with Western blotting. Results Mfn1 significantly decreased in vivo 3 days after burn which was associated with decreased myogenin expression (p< 0.05). Additionally, significant decreases in Opa1, an Mfn1 analogue, and desmin were reduced in KO cells after burn serum stimulation (p < 0.05); meanwhile, PCNA and Pax7 (markers of cell proliferation) were significantly increased (p < 0.035 and p