Relationship between fat embolism and endothelial glycocalyx

Fat embolism (FE) is acknowledged as one of the significant causes of sudden death following traumatic injury. To clarify the relevance of vascular endothelial glycocalyx (EGC) damage and FE, temporal changes in the mRNA levels of inflammatory cytokines associated with EGC components were investigated in an experimental fat embolization rat model. Nine-week-old rats were used as FE models through triolein injection (TO) and femoral fracture (FX), and physiological saline was administered to the control group. RT-qPCR and fat staining were performed. The target genes were Il6, Il10, Tnf, Elane, Sdc1, Sdcbp, Vcan, Hyal1, Fn1, and CD14. Notably, FE was detected in 100% and 5.6% of the TO and FX groups, respectively, using fat staining. Bimodal peaks in the mRNA expression levels of Sdc1, Tnf, Elane, IL6, and IL10 were observed 4 and 20 h after treatment in both groups. In the TO group, mRNA expression peaked at 4 h and then declined to the lowest level at 16 h. The incidence of fat emboli due to trauma was consistent with that reported in previous studies. Bimodal mRNA peaks may correspond to FE progression, in which physical obstructions are followed by biochemical reactions. The fluctuation in Sdc1 expression suggests that the initial peak resulted from physical EGC damage. The subsequent peak could be because of EGC damage caused by the secretion of inflammatory cytokines induced by oleic acid from lipid droplet decomposition. These results suggest that EGC disorders caused by lipid droplets may induce lung damage during FE.