SARS-CoV-2 infection in coronary vessels linked to cardiovascular complications

In a recent study published in the journal Nature Cardiovascular Research, researchers reported that the increased long-term risk of acute cardiovascular complications associated with coronavirus disease 2019 (COVID-19) is linked to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infecting coronary vessels and inducing the formation of plaques.

Background

The clinical presentations of COVID-19 have been widely varied, ranging from asymptomatic to acute respiratory distress, complications involving multiple organs, and even death.

One of the clinical complications of SARS-CoV-2 infections is ischemic cardiovascular events, including stroke and acute myocardial infarctions (AMI), which manifest when atherosclerotic plaques that are chronically inflamed get disrupted.

While strokes and AMIs have been observed in the case of several respiratory infections, such as those involving influenza virus, the risk of stroke is more than seven-fold higher for COVID-19 patients.

Furthermore, the cytokine storm involving an extreme inflammatory response often associated with severe COVID-19 cases is thought to increase the risk of stroke and AMIs. However, while the direct infection of lungs and other organs such as the brain, kidney, adipose tissue, gut, and myocardium by SARS-CoV-2 has been documented, whether the virus directly infects the coronary vasculature and its role in increasing the risk of stroke or AMIs remains poorly understood.

About the study

In the present study, the researchers used coronary autopsy specimens from patients with reverse transcription polymerase chain reaction (RT-PCR)-confirmed COVID-19 between May 2020 and 2021. The autopsy reports and medical health records provided relevant demographic data and medical history, including the cardiovascular risk factors and clinical characteristics.

Of the eight patients included in the study, three were diagnosed with acute myocardial ischemia during the hospitalization, one experienced a stroke, and the autopsy results of four patients revealed coronary stenosis. Coronary artery sections from autopsy samples were hematoxylin and eosin stained and classified as pathological intimal thickening with macrophage infiltration, fibrocalcific plaque, adaptive intimal thickening, and fibroatheroma by a cardiovascular pathologist. Immunohistochemical staining for CD68⁺ was also performed.

Ribonucleic acid (RNA) fluorescence in situ hybridization (RNA-FISH) was conducted to detect the viral RNA encoding the SARS-CoV-2 spike protein. Furthermore, the antisense strand of the spike protein gene was also probed to confirm the infection of the coronary vasculature by SARS-CoV-2 since the antisense strand is only produced when the virus replicates. The cellular localization of the viral RNA was established by identifying the macrophage infiltration of coronary vessels using CD68 probes.

Additionally, a neural network artificial intelligence-based method was used to classify the perivascular fat and coronary artery wall in each section, given the ability SARS-CoV-2 has to infect and accumulate viral RNA in adipose tissue.

Nuclear segmentation was also used to quantify the infiltration of the perivascular fat and coronary artery wall with RNAscope probes. Further RNAscope analyses using single-cell RNA sequencing (scRNAseq) datasets of mice and humans were used to detect the potential spread of SARS-CoV-2 to other cells, especially vascular smooth muscle cells.

Foam cells, which are macrophages laden with cholesterol and the accumulation of which is indicative of various stages of cardiovascular disease, were also investigated for SARS-CoV-2 infection, as were macrophages. These cells were also experimentally infected with a modified fluorescent reported virus carrying the isolate from SARS-CoV-2 USA WA1/2020 to understand whether the virus could infect plaque macrophages and foam cells.

Results

The findings reported that the viral RNA of SARS-CoV-2 was detected and found to replicate in the autopsy samples of coronary vasculature obtained from severe cases of COVID-19. Additionally, the virus showed a stronger tropism for plaque macrophages and arterial lesions than the perivascular fat surrounding the lesions, which also correlated to the levels of macrophage infiltration.

Furthermore, foam cells were more susceptible to getting infected with SARS-CoV-2 than the other macrophage types, and the infection was dependent on the neuropilin-1 receptor. The SARS-CoV-2 infection of human vascular carotid explants conducted ex-vivo also showed that the virus stimulated strong inflammatory responses in foam cells and macrophages that were pro-atherogenic. This is believed to exacerbate ischemic cardiovascular complications in severe COVID-19 cases.

However, the authors stated that given the small cohort size investigated in the study, which largely consisted of older patients with pre-existing cardiovascular complications, the results cannot be generalized to the younger, healthier populations. Furthermore, the findings were based on the strains in circulation in the early phases of the pandemic, and the replication of subsequent SARS-CoV-2 strains in the coronary vasculature cannot be confirmed based on these results.

Conclusions

Overall, the findings suggested that SARS-CoV-2 exhibited a tropism for foam cells and plaque macrophages over the surrounding perivascular fat in coronary vasculature.

Ex-vivo experiments also demonstrated that SARS-CoV-2 infections in macrophages and vascular explants induced strong inflammatory responses and increased cytokine secretion associated with cardiac events.

The results indicated that SARS-CoV-2 infections in the coronary vasculature induce plaque formation and increase the risk of cardiovascular complications.