Here, by using the atomic force microscope [15] as a well-established nanoindentation tool [16, 17], we demonstrated that the eGC of primary endothelial cells after incubation with sera derived from COVID-19 patients with mild and severe symptoms is significantly damaged, which could be prevented by administering the MR antagonist spironolactone. The gene discussed is NR3C2; the disease is COVID-19.