INCREASED PLATELET MITOCHONDRIAL FUNCTION CORRELATES WITH CLOT STRENGTH IN A RODENT FRACTURE MODEL

Abstract

Abstract Background Thromboelastographic measures of clot strength increase early after injury, portending higher risks for thromboembolic complications during recovery. Understanding the specific role of platelets is challenging due to a lack of clinically relevant measures of platelet function. Platelet mitochondrial respirometry may provide insight to global platelet function, but has not yet been correlated with functional coagulation studies. Methods Wistar rats underwent anesthesia and either immediate sacrifice for baseline values [n = 6] or (1) bilateral hindlimb orthopedic injury [n = 12], versus (2) sham anesthesia [n = 12] with terminal phlebotomy/hepatectomy after 24 hours. High resolution respirometry was used to measure basal respiration, mitochondrial leak, maximal oxidative phosphorylation, and Complex IV activity in intact platelets; Complex-I and Complex-II driven respiration was measured in isolated liver mitochondria. Results were normalized to platelet number and protein mass, respectively. Citrated native thromboelastography (TEG) was performed in triplicate. Results Citrated native TEG maximal amplitude (MA) was significantly higher (81.0 ± 3.0 vs. 73.3 ± 3.5 mm, p < 0.001) in trauma compared to sham rats 24 hours after injury. Intact platelets from injured rats had higher basal oxygen consumption (17.7 ± 2.5 vs. 15.1 ± 3.2 pmol/s*108 cells, p = 0.045), with similar trends in mitochondrial leak rate (p = 0.19) when compared to sham animals. Overall, platelet basal respiration significantly correlated with TEG-MA (r = 0.44, p = 0.034). As a control for sex-dependent systemic mitochondrial differences, females displayed higher liver mitochondria Complex-I driven respiration (895.6 ± 123.7 vs. 622.1 ± 48.7 mmol e-/min/mg protein, p = 0.02); as a control for systemic mitochondrial effects of injury, no liver mitochondrial respiration differences were seen. Conclusions Platelet mitochondrial basal respiration is increased after injury and correlates with clot strength in this rodent hindlimb fracture model. Several mitochondrial-targeted therapeutics exist in common use that are underexplored but hold promise as potential antithrombotic adjuncts that can be sensitively evaluated in this preclinical model.