Engagement of chymase-positive mast cells in myocardial damage associated with COVID-19

Acute myocardial injury is a frequent and severe complication of COVID-19, contributing to increased mortality. This study investigates the role of chymase-positive mast cells (MCs) in myocardial damage among patients who died from severe or critical COVID-19.

Cardiac tissue samples from 60 deceased patients were analyzed histologically and immunohistochemically to assess MC density, degranulation status, and associated fibrotic remodeling. Clinical and laboratory parameters, including troponin I levels and inflammatory markers were obtained during hospitalization period.

The findings revealed a low overall density of cardiac MCs, with a predominance of degranulated chymase-positive cells. These MCs were significantly correlated with indicators of severe COVID-19 progression, such as neutrophilic leukocytosis, elevated band neutrophils, monocytosis, and increased erythrocyte sedimentation rate. A strong association was also observed between chymase-positive MCs and elevated troponin I levels, the association between troponin I and degranulating chymase-positive MC density remained statistically significant after multivariable adjustment, supporting an independent link to myocardial injury. Additionally, increased MC presence coincided with extensive interstitial and perivascular fibrosis, marked by a predominance of type III collagen.

These results support the hypothesis that chymase-positive MCs contribute to myocardial inflammation and fibrosis in the context of COVID-19. Understanding their role may open avenues for targeted therapies aimed at mitigating cardiac complications in future coronavirus-related diseases.