Human cardiac stromal cells exposed to SARS-CoV-2 evolve into hyper-inflammatory/pro-fibrotic phenotype and produce infective viral particles depending on the levels of ACE2 receptor expression

Patients with severe respiratory syndrome caused by SARS-CoV-2 undergo cardiac complications due to hyper-inflammatory conditions. Although the presence of the virus has been detected in the myocardium of infected patients, and infection of cardiac cells may involve ACE2 receptor, the underlying molecular/cellular mechanisms are still uncharacterized. We analyzed expression of ACE2 receptor in primary human cardiac stromal cells using proteomic and transcriptomic methods before exposing them to SARS-CoV-2 in vitro. Using conventional and high sensitivity PCR methods, we measured virus production in the cellular supernatants and monitored the intracellular viral bioprocessing. We performed high-resolution imaging to show the sites of intracellular viral production. We finally used Q-RT-PCR assays to detect genes linked to innate immunity and fibrotic pathways coherently regulated in cells exposed to virus. Our findings indicate that human cardiac stromal cells have a susceptibility to SARS-CoV-2 infection and produce variable viral yields depending on the extent of cellular ACE2 receptor expression. Interestingly, these cells also evolved toward hyper-inflammatory/pro-fibrotic phenotypes independently of ACE2 levels, suggesting a dual cardiac damage mechanism that could account for the elevated numbers of cardiac complications in severe COVID-19 cases.

Evidence of SARS-CoV-2 transcriptional activity in cardiomyocytes of COVID-19 patients without clinical signs of cardiac involvement

BackgroundCardiovascular complication in patients affected by novel Coronavirus respiratory disease (COVID-19) are increasingly recognized. However, although a cardiac tropism of SARS-CoV-2 for inflammatory cells in autopsy heart samples of COVID-19 patients has been reported, the presence of the virus in cardiomyocytes has not been documented yet. MethodsWe investigated for SARS-CoV-2 presence in heart tissue autopsies of 6 consecutive COVID-19 patients deceased for respiratory failure showing no signs of cardiac involvement and with no history of heart disease. Cardiac autopsy samples were analysed by digital PCR, Western blot, immunohistochemistry, immunofluorescence, RNAScope, and transmission electron microscopy assays. ResultsThe presence of SARS-CoV-2 into cardiomyocytes was invariably detected. A variable pattern of cardiomyocytes injury was observed, spanning from the absence of cell death and subcellular alterations hallmarks to the intracellular oedema and sarcomere ruptures. In addition, we found active viral transcription in cardiomyocytes, by detecting both sense and antisense SARS-CoV-2 spike RNA. ConclusionsIn this analysis of autopsy cases, the presence of SARS-CoV-2 into cardiomyocytes, determining variable patterns of intracellular involvement, has been documented. All these findings suggest the need of a cardiologic surveillance even in survived COVID-19 patients not displaying a cardiac phenotype, in order to monitor potential long-term cardiac sequelae.