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SARS-CoV-2, which causes the disease COVID-19, generally has a mild disease course in children. However, a severe post-infectious inflammatory process known as multisystem inflammatory syndrome in children has been observed in association with COVID-19. This inflammatory process is a result of an abnormal immune response with similar clinical features to Kawasaki disease. It is well established that multisystem inflammatory syndrome in children is associated with myocardial dysfunction, coronary artery dilation or aneurysms, and occasionally arrhythmias. The most common electrocardiographic abnormalities seen include premature atrial or ventricular ectopy, variable degrees of atrioventricular block, and QTc prolongation, and rarely, haemodynamically significant arrhythmias necessitating extracorporeal membrane oxygenation support. However, presentation with fever, hypotension, and relative bradycardia with a left axis idioventricular rhythm has not been previously reported. We present a case of a young adolescent with multisystem inflammatory syndrome in children with myocarditis and a profoundly inappropriate sinus node response to shock with complete resolution following intravenous immunoglobulin.

Electrospun 3-dimensional nanofibrous scaffolds share morphologic similarities to collagen fibrils, and promote favorable biologic responses of seeded cells. In this study, we have fabricated a 3-dimensional nanofibrous scaffold made of poly L-lactic acid, and examined its ability to support and maintain the adipogenic differentiation of human bone marrow-derived mesenchymal stem cells in vitro. After a 21-day incubation, oil red O staining of constructs treated with adipogenic supplements revealed positive adipose-like staining, compared with lack of staining in untreated cultures. Semi-quantitative RT-PCR analysis of human bone marrow-derived mesenchymal stem cells cultured in adipogenic medium revealed highly elevated levels of adipogenesis-associated genes (1797-fold for lipoprotein lipase, and 5.6-fold for peroxisome proliferator-activated receptor gamma). Immunofluorescence staining of cellular constructs in adipogenic culture media showed the presence of lipoprotein lipase vesicles, a characteristic feature of adipose tissue. These results suggest that the poly L-lactic acid-based nanofibrous scaffold is a promising candidate for adult stem cell-based engineering of adipose tissue.