Endothelial cells resistant to SARS-CoV-2 infection

Team of scientists from Imperial College London A series of In vitro A study to investigate the susceptibility of endothelial cells to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the causative agent of coronavirus disease in 2019 (COVID-19).

Studies show that endothelial cells are resistant to SARS-CoV-2 infection and that the vascular complications observed in COVID-19 patients may be caused by systemic proinflammatory mediators and other cellular factors. is showing. Research is currently bioRxiv* Preprint server.

It takes time to develop effective treatments and vaccines to control the ever-increasing trajectory of COVID-19. There are several potential vaccines in the pipeline, but it is still unclear if these vaccines can provide long-term protection. The drugs currently used to treat patients with COVID-19 are mostly reusable drugs known to target viral replication. Therefore, a correct understanding of the pathophysiology of the disease is important for developing treatments that specifically target SARS-CoV-2 and improve the disease outcome of patients infected with SARS-CoV-2.

Primarily, SARS-CoV-2 infection occurs in the respiratory epithelium, and the interaction of the viral spike protein with the angiotensin converting enzyme 2 (ACE2) receptor in the host cell causes viral invasion. There may also be alternative pathways for SARS-CoV-2 to enter host cells via transmembrane. Glycoprotein It is called Bashigin (BSG). Some recent evidence suggests that people with severe COVID-19 develop persistent cardiovascular complications such as coagulopathy and bleeding disorders even after recovery. This indicates that SARS-CoV-2 may affect the endothelium of blood vessels in addition to the respiratory epithelium.

The current study was conducted to thoroughly investigate the ability of SARS-CoV-2 to infect endothelial cells.

MRNA expression of ACE2, TMPRSS2, BSG, PPIA and PPIB in human nasal epithelial cells (NEC) and endothelial cells (aorta, microvessel and blood growth). Expression levels of the genes ACE2, TMPRSS2, BSG, PPIA and PPIB were obtained from the aorta (AoEC), microvessels (HMVEC) and blood growth (BOEC) endothelial cells and nasal epithelial cells (NEC). Data for each donor was normalized using housekeeper (18S and Gapdh) averages and analyzed using the comparative Ct method (2DDCt). Data show AoEC (n = 3 wells using cells from 3 separate donors), HMVEC (using cells from 2 donors n = 3 wells) nasal epithelium (using cells from 2 donors) ) Compared to mean +/- SEM multiple change shown as 3 separate donor and BOEC cells (n = 2 wells using cells from 2 separate donors).

Current research design

Scientists are a series In vitro Experiments with primary endothelial cell lines infected with either raw SARS-CoV-2 or a Pseudovirus Expresses viral spike proteins. They used three cell lines, including blood-growing endothelial cells, pulmonary microvascular endothelial cells, and aortic endothelial cells. They selected three cell lines as positive controls for comparison with endothelial cell findings, including nasal epithelial cells, primate kidney fibroblasts, and human kidney embryo cells.

Important findings

Scientists have observed that expression of ACE2 and TMPRSS2 (cell surface proteases required for viral invasion) is significantly lower in endothelial cells compared to nasal epithelial cells. However, they found equivalent expression of proteins in alternative viral entry pathways such as BSG, PPIA, and PPIB in endothelial and epithelial cells. These findings suggest that the ACE2-independent pathway (BSG pathway) may be involved in the invasion of SARS-CoV-2 into endothelial cells.

By incubating both endothelial cells and primate kidney fibroblasts with live SARS-CoV-2, they observed that the virus successfully invaded the fibroblasts and initiated replication. However, they were unable to detect SARS-CoV-2 infection in endothelial cells. To determine if the endothelial cells are resistant to SARS-CoV-2 infection at the entry or replication level of the virus, the cells were infected with a pseudovirus that expresses the spike protein. Similar to previous findings, they were unable to detect the invasion of SARS-CoV-2 into endothelial cells via spike proteins. These findings suggest that endothelial cells are insensitive to SARS-CoV-2 infection even at high levels of BSG expression.

To further validate the involvement of the ACE2 and BSG-mediated pathways in viral invasion, human renal embryonic cells that transiently express ACE2 or BSG were incubated with a spiky protein-expressing pseudovirus. As expected, they observed that only ACE2 expression, not BSG expression, promoted viral entry into cells.

Since active viral infections are associated with an pro-inflammatory cellular environment, scientists wondered if inflammatory mediators could promote the invasion of the virus into endothelial cells. To this end, they primed cells with interleukin-1β (IL-1β), a leukocyte pyrogen, and increased the production of other pro-inflammatory cytokines such as IL-6 and IL-8. However, even in this inflammatory environment, endothelial cells remained resistant to SARS-CoV-2 infection.

Given the high resistance of endothelial cells to SARS-CoV-2 infection, scientists have found that molecules released by nearby epithelial cells or systemic inflammatory mediators are the major source of COVID-19-related cardiovascular complications. I think it is the cause. The pro-inflammatory cellular environment created by SARS-CoV-2 infection may be responsible for the loss of barrier function, promoting viral invasion of blood vessels and infection of multiple organs through the bloodstream. To do.

*Important Notices

bioRxiv Publish preliminary scientific reports that should not be considered definitive as they have not been peer-reviewed, guide clinical practice / health-related behaviors, and should not be treated as established information.