Human cardiosphere-derived 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

Abstract

Aims 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 induced pluripotent cells-derived cardiomyocytes has been demonstrated, the reported expression of ACE2 in cardiac stromal cells suggests that SARS-CoV-2 may determine cardiac injury by sustaining productive infection and increasing inflammation. Methods and Results We analyzed expression of ACE2 receptor in primary human cardiac stromal cells derived from cardiospheres, using proteomics and transcriptomics before exposing them to SARS-CoV-2 in vitro. Using conventional and high sensitivity PCR methods, we measured virus release in the cellular supernatants and monitored the intracellular viral bioprocessing. We performed high-resolution imaging to show the sites of intracellular viral production and demonstrated the presence of viral particles in the cells with electron microscopy. We finally used RT-qPCR assays to detect genes linked to innate immunity and fibrotic pathways coherently regulated in cells after exposure to the virus. Conclusions Our findings indicate that cardiac stromal cells are susceptible 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. Thus, SARS-CoV-2 infection of myocardial stromal cells could be involved in cardiac injury, and explain the high number of complications observed in severe cases of COVID-19. Translational Perspective In the present investigation, we provide evidence that human cardiac stromal cells, a major component of the non-contractile cellular fraction in the heart can be infected by SARS-CoV-2 in vitro, in direct relationship to the extent of ACE2 receptor expression. Our work also suggests that these cells, when exposed to the virus, can evolve toward inflammatory and fibrotic phenotypes independently of ACE2. In addition to describing a novel cellular target of SARS-CoV-2 in the human heart, our study generates new hypothesis on potential mechanisms underlying cardiac complications observed in COVID-19 patients.

The SARS-CoV-2 Spike protein disrupts human cardiac pericytes function through CD147 receptor-mediated signalling: a potential non-infective mechanism of COVID-19 microvascular disease

“…This difference may account for the noticeably lower virus infection of PCs. This observation is in line with recent reports showing that, in vitro , low ACE2 expression levels in myocardial stromal cells resulted in low susceptibility to viral infection [ 50 ], whilst mesenchymal stromal cells were not infected due to the lack of ACE2/TMPRSS2 [ 51 ]. Importantly, our data newly demonstrate that the CD147 receptor, and not ACE2, leads the S signalling in PCs.…”

Evidence for Biological Age Acceleration and Telomere Shortening in COVID-19 Survivors

“…ACE2 is a crucial component of the SARS-CoV-2 infection process. SARS-CoV-2 uses the ACE2 receptor to invade human alveolar epithelial cells and other cells, including cardiac fibroblasts [ 50 ]. In infected individuals, ACE2 is often down-regulated due to the infection [ 7 , 45 ].…”

Evidence for Biological Age Acceleration and Telomere Shortening in Covid19 Survivors

“…ACE2 is a crucial component of the SARS-CoV-2 infection process. SARS-CoV-2 uses the ACE2 receptor to invade human alveolar epithelial cells and other cells, including cardiac fibroblasts (53). In infected individuals, ACE2 is often down-regulated due to the infection (14)(48).…”