DEVELOPMENT AND VALIDATION OF A LIPOPOLYSACCHARIDE-INDUCED MYOCARDIAL INFLAMMATION MODEL IN MICE FOR PRECLINICAL RESEARCH ON STEM CELL-BASED THERAPY
Authors: Kyryk Vitalii , Ustymenko Alina , Klymenko Pavlo , Tsupykov Oleg 
Published: December 2024

One of the serious cardiovascular complications during the COVID-19 pandemic was myocardial inflammation, which often affected young patients but was particularly dangerous for the elderly. This condition, triggered by systemic inflammation in acute respiratory distress syndrome, contributed to the progression of heart failure. Due to the lack of effective treatment methods, this led to high mortality rates among affected patients. The lipopolysaccharide-induced model of myocardial injury can replicate the pathogenic myocardial changes characteristic of inflammation seen in COVID-19, providing a valuable tool for experimental studies of potential anti-inflammatory therapies, including stem cell treatments.
Objective. This study aimed to develop and validate a lipopolysaccharide-induced model of inflammatory myocardial injury to investigate the regenerative potential of stem cells in myocarditis of various origins.
Materials and methods. The study was conducted on female FVB «wild-type» mice aged 4–5 months. A single intraperitoneal injection of E. coli lipopolysaccharide was administered at doses of 1 mg/kg or 5 mg/kg to induce a systemic inflammatory response. Electrocardiographic assessments were performed before the injection and on days 7 and 14 post-injection. On these days, histological sections of the heart were prepared to analyze morphological markers of inflammatory myocardial injury, and immunohistochemical staining for the apoptosis marker CD95 was conducted.
Results. One week after the administration of lipopolysaccharide, electrocardiographic studies in mice revealed an increase in heart rate compared to baseline, with increases of 19.6 % and 13.2 % following the administration of lipopolysaccharide (LPS) at doses of 1 mg/kg and 5 mg/kg, respectively. This response indicates a compensatory reaction to the impairment of the heart’s contractile function due to myocardial injury. Additionally, signs of intraventricular conduction disturbances were observed, including R wave deformation and ventricular extrasystoles, which persisted in the group receiving LPS at a dose of 5 mg/kg after two weeks. Histological sections in both animal subgroups, one week after LPS administration, revealed cytoplasmic swelling and eosinophilia resulting from myofibril contraction, along with significant vascular congestion characterized by stasis and aggregation of erythrocytes. These changes were more pronounced in the group receiving the 5 mg/kg LPS dose. Two weeks after administration of LPS at a dose of 1 mg/kg, significantly less severe manifestations of myocardial injury were observed, indicating partial recovery due to endogenous repair mechanisms. In contrast, the group receiving the 5 mg/kg dose exhibited morphological signs of persistent inflammation in the heart tissue. Immunohistochemical analysis revealed the expression of the apoptosis marker CD95 in cells throughout the entire section of myocardium in mice with LPS-induced inflammation.
Conclusions. A model of lipopolysaccharide-induced inflammatory myocardial injury in mice has been developed and validated for investigating the regenerative potential of stem cells in inflammatory heart diseases. Electrophysiological and morphological studies indicate that a dose of 5 mg/kg of E. coli lipopolysaccharide is optimal for inducing more pronounced inflammatory changes in the myocardium of laboratory mice compared to a dose of 1 mg/kg.