Muscle homeostasis is disrupted in burned adults

Severe burn leads to substantial skeletal muscle wasting that is associated with adverse outcomes and protracted recovery. The purpose of our study was to investigate muscle tissue homeostasis in response to severe burn. Muscle biopsies from the right m. lateralis were obtained from 10 adult burn patients at the time of their first operation. Patients were grouped by burn size (total body surface area of <30% vs ≥30%). Muscle fiber size and factors of cell death and muscle regeneration were examined. Muscle cell cross-sectional area was significantly smaller in the large-burn group (2174.3 ± 183.8 µm² vs 3687.0 ± 527.2 µm², P = .04). The expression of ubiquitin E3 ligase MuRF1 and cell death downstream effector caspace 3 was increased in the large-burn group (P < .05). No significant difference was seen between groups in expression of the myogenic factors Pax7, MyoD, or myogenin. Interestingly, Pax7 and proliferating cell nuclear antigen (PCNA) expression in muscle tissue were significantly correlated to injury severity only in the smaller-burn group (P < .05). In conclusion, muscle atrophy after burn is driven by apoptotic activation without an equal response of satellite cell activation, differentiation, and fusion.