Characterization of the binding of skeletal muscle myosin to fibrin in trauma

BACKGROUND: The procoagulant phenotype of skeletal muscle myosin (SkM) includes the promotion of thrombin generation to form fibrin, and subsequent increased resistance of fibrin clots to fibrinolysis. The release of SkM into circulation following localized tissue injury is hypothesized to promote systemic hypercoagulation. Yet, in trauma patients and in animal models of tissue injury, an unexplained decrease in SkM levels has been observed. METHODS: Plasma samples were collected from orthopedic trauma patients at admission and 6 weeks later and from pigs subjected to experimentally extensive muscle injury. Plasma SkM and myoglobin levels were measured. The binding of SkM to fibrin was quantified in vitro using fluorescence imaging assays. Fibrinolysis was measured using turbidimetric assays and thromboelastography. RESULTS: SkM plasma levels in trauma patients were lower at admission compared to 6 weeks later, while plasma myoglobin levels were higher at admission than at 6 weeks. In the pig injury model, plasma SkM levels at 24 hours after injury were decreased, while myoglobin levels were increased. In vitro, SkM bound to fibrin, but not fibrinogen, with an apparent K d of 0.18 μM and was associated with a decrease in the level of SkM in solution. Fluorescence imaging of the fibrin clots confirmed the presence of SkM within fibrin clots, which increased the resistance of the fibrin clot to fibrinolysis. CONCLUSIONS: Direct binding of SkM to fibrin may explain the reduced circulating SkM levels observed after trauma and may help identify potential roles for SkM in trauma-associated coagulopathy. ( J Trauma Acute Care Surg . 2026;00:00-00. Copyright © 2026 Wolters Kluwer Health, Inc. All rights reserved.) LEVEL OF EVIDENCE: Prognostic; Level III.