Regeneration of deep burn wounds after transplantation of allogenic and autogenic fibroblast-like bone marrow mesenchymal stem cells and embryonic fibroblasts on burn surface was studied in 40 Wistar rats. Transplantation of allogenic and autogenic fibroblast-like bone marrow mesenchymal stem cells and transplantation of embryonic fibroblasts decreased cell infiltration of the wound and accelerated the formation of new vessels and granulation tissue in the wound in comparison with the control (burn wounds without cell transplantation). Regeneration processes were most active after transplantation of fibroblast-like bone marrow mesenchymal stem cells, in particular, autogenic cells, which was confirmed by more rapid decrease in burn surface area. Wound healing after transplantation of fibroblast-like bone marrow mesenchymal cells and embryonic fibroblasts was associated with long functioning of transplanted cells (as was shown by staining for beta-galactosidase, the cells were transfected with an adenovirus vector carrying the marker gene). It is hypothesized that more rapid regeneration of burn wounds after transplantation of fibroblast-like bone marrow mesenchymal stem cells was due to low differentiation of these cells in comparison with embryonic fibroblasts.

The aim of this study is to evaluate the blood level of anti‐heart antibodies (AHA) and its correlation with clinical outcomes in patients with severe and moderate coronavirus disease 2019 (COVID‐19). The study included 34 patients (23 males; mean age 60.2 ± 16.6 years) with COVID‐19 pneumonia. Besides standard medical examination, the AHA blood levels were observed, including antinuclear antibodies, antiendothelial cell antibodies, anti‐cardiomyocyte antibodies (AbC), anti‐smooth muscle antibodies (ASMA), and cardiac conducting tissue antibodies. Median hospital length of stay was 14 [13; 18] days. AHA levels were increased in 25 (73.5%) patients. Significant correlation (p < 0.05) of AHA levels with cardiovascular manifestations (r = 0.459) was found. AbC levels correlated with pneumonia severity (r = 0.472), respiratory failure (r = 0.387), need for invasive ventilation (r = 0.469), chest pain (r = 0.374), low QRS voltage (r = 0.415), and levels of C‐reactive protein (r = 0.360) and lactate dehydrogenase (r = 0.360). ASMA levels were found to correlate with atrial fibrillation (r = 0.414, p < 0.05). Antinuclear antibodies and AbC levels correlated with pericardial effusion (r = 0.721 and r = 0.745, respectively, p < 0.05). The lethality rate was 8.8%. AbC and ASMA levels correlated significantly with lethality (r = 0.363 and r = 0.426, respectively, p < 0.05) and were prognostically important. AHA can be considered as part of the systemic immune and inflammatory response in COVID‐19. Its possible role in the inflammatory heart disease requires further investigation.

We compared the effects of transplantation of fetal fibroblasts and fibroblast-like mesenchymal stem cells of the bone marrow on healing of deep burn wound in rats. It was found that transplantation of fetal fibroblasts and fibroblast-like mesenchymal stem cells on the burn surface reduces cell infiltration, promotes the formation of vessels and granulation tissue, which creates conditions for more rapid healing of the burn wounds.

The effect of cell transplantation into cryodamaged rat myocardium was studied on isolated hearts by increasing functional load to the left ventricle. Transplantation of allogeneic fetal cardiomyocytes improved the function of the left ventricle under conditions of considerably increased preload. Transplantation of autologous mesenchymal stem cells repaired left-ventricular function under conditions of increased pre- and afterload.

Aim    To study clinical features of myoendocarditis and its possible mechanisms, including persistence of SARS-Cov-2 in the myocardium, in the long-term period following COVID-19.Material and methods    This cohort, prospective study included 15 patients aged 47.8±13.4 years (8 men) with post-COVID myocarditis. The COVID-19 diagnosis was confirmed for all patients. Median time to seeking medical care after COVID-19 was 4 [3; 7] months. The diagnosis of myocarditis was confirmed by magnetic resonance imaging (MRI) of the heart (n=10) and by endomyocardial biopsy of the right ventricle (n=6). The virus was detected in the myocardium with PCR; immunohistochemical (IHC) study with antibody to SARS-Cov-2 was performed; anticardiac antibody level was measured; and echocardiography and Holter monitoring were performed. Hemodynamically significant coronary atherosclerosis was excluded for all patients older than 40 years.Results    All patients showed a clear connection between the emergence or exacerbation of cardiac symptoms and COVID-19. 11 patients did not have any signs of heart disease before COVID-19; 4 patients had previously had moderate arrhythmia or heart failure (HF) without myocarditis. Symptoms of myocarditis emerged at 1–5 months following COVID-19. MRI revealed typical late gadolinium accumulation, signs of hyperemia, and one case of edema. The level of anticardiac antibodies was increased 3-4 times in 73 % больных. Two major clinical variants of post-COVID myocarditis were observed. 1. Arrhythmic (n=6), with newly developed extrasystole or atrial fibrillation without systolic dysfunction. 2. Decompensated variant with systolic dysfunction and biventricular HF (n=9). Mean left ventricular ejection fraction was 34.1±7.8 %, and left ventricular end-diastolic dimension was 5.8±0.7 cm. In one case, myocarditis was associated with signs of IgG4‑negative aortitis. SARS-Cov-2 RNA was found in 5 of 6 biopsy samples of the myocardium. The longest duration of SARS-Cov-2 persistence in the myocardium was 9 months following COVID-19. By using antibody to the Spike antigen and nucleocapsid, SARS-Cov-2 was detected in cardiomyocytes, endothelium, and macrophages. Five patients were diagnosed with lymphocytic myocarditis; one with giant-cell myocarditis; three patients had signs of endocarditis (infectious, lymphocytic with mural thrombosis).Conclusion    Subacute/chronic post-COVID myocarditis with isolated arrhythmias or systolic dysfunction is characterized by long-term (up to 9 months) persistence of SARS-Cov-2 in the myocardium in combination with a high immune activity. Endocarditis can manifest either as infectious or as nonbacterial thromboendocarditis. A possibility of using corticosteroids and anticoagulants in the treatment of post-COVID myoendocarditis should be studied.