[Establishment and evaluation of mouse models of septic myocardial injury]

Mouse models of sepsis-induced myocardial injury by intraperitoneal injection of lipopolysaccharide (LPS) was established in order to provide a reliable method for the research of pathogenesis of sepsis-induced myocardial injury.

According to the method of random number table, a total of 150 male C57BL/6 mice were divided into five groups: NC group, sham group, and LPS 10, 12, 15 mg/kg groups, with 30 in each group. Septic myocardial injury was induced by intraperitoneal injection LPS in mice; sham group was injected with equal 0.9% saline; while there was no treatment in mice of NC group. Fifteen of the 30 mice in each group were used to observe the general status of mice before and after LPS or saline injection. Twenty-four hours after LPS or saline injection, the left ventricular function was assessed by echocardiography, serum level of cardiac troponin (cTnI) was determined by enzyme linked immunosorbent assays (ELISA), and the cardiac histomorphology and ultrastructure were observed; the other 15 mice were used to monitor the 7-day mortality after LPS or saline injection.

The mice challenged to LPS displayed symptoms of sepsis, such as depression, ruffled fur, and diarrhea. Compared with NC group, left ventricular ejection fraction (LVEF), left ventricular fraction shortening (LVFS) were significantly decreased at 24 hours after LPS administration in LPS 10, 12, 15 mg/kg groups [LVEF: 0.459±0.044, 0.432±0.034, 0.348±0.064 vs. 0.588±0.019, LVFS: (22.36±2.60)%, (20.78±1.91)%, (16.27±3.31)% vs. (30.55±1.30)%, all P < 0.01], and cTnI levels were significantly increased (ng/L: 270.40±43.50, 281.14±41.79, 298.39±42.05 vs. 192.59±16.90, all P < 0.01). Myocardium injury was observed in three LPS groups, myocardial fibrosis, interstitial edema, erythrocyte leakage and infiltrating inflammatory cells were observed under light-microscope; ultrastructural changes disorderly arranged in cardiac muscle fibers, mitochondrial swelling and even partly missing mitochondria cristae were found under transmission electron microscope (TEM), and the higher of the dose, the more sever of the damage. There was no significant difference between sham group and NC group. The 7-day mortality in LPS 10, 12, 15 mg/kg groups were 33.3%, 53.3% and 86.7%, respectively, while no death in the NC group and sham group.

For establishing the mouse model of sepsis-induced myocardial injury, intraperitoneal injection with 12 mg/kg LPS is a preferable choice in our research.