Histopathological Evaluation of Pulmonary Arterial Remodeling in COVID-19

A positive-sense single-stranded RNA virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), caused the coronavirus disease 2019 (COVID-19) pandemic that devastated the world. While this is a respiratory virus, one feature of the SARS-CoV-2 infection was recognized to cause pathogenesis of other organs. Because the membrane fusion protein of SARS-CoV-2, the spike protein, binds to its major host cell receptor angiotensin-converting enzyme 2 (ACE2) that regulates a critical mediator of cardiovascular diseases, angiotensin II, COVID-19 is largely associated with vascular pathologies. In fact, we have previous reported that postmortem lung tissues collected from patients who died of COVID-19 exhibited thickened pulmonary vascular walls and reduced vascular lumen. The present study extended these findings by further characterizing the pulmonary vasculature of COVID-19 patients using larger sample sizes and providing mechanistic information through histological observations. The examination of 56 autopsy lung samples showed thickened vascular walls of small pulmonary arteries after 14 days of disease compared to H1N1 influenza patients who died before COVID- 19 pandemic started. Pulmonary vascular remodeling in COVID-19 patients was associated with hypertrophy of the smooth muscle layer, perivascular fibrosis, edema and lymphostasis, inflammatory infiltration, perivascular hemosiderosis and neoangiogenesis. We found a correlation between the duration of hospital stay and the thickness of the muscular layer of pulmonary arterial walls. These results further confirm that COVID-19 affects the pulmonary vasculature and warrants an evaluation of patients that survived COVID-19 for possible future development of pulmonary arterial hypertension.