Pathological post-mortem findings in lungs infected with SARS-CoV-2

Area of Science:

• Pathology
• Virology
• Pulmonology

Background:

• Italy experienced a high SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) mortality rate, particularly among males, the elderly, and those with comorbidities.
• Understanding the pathological mechanisms of SARS-CoV-2 is crucial for patient outcomes.

Purpose of the Study:

• To investigate the lung pathological and immunohistochemical findings in post-mortem autopsies of patients deceased from SARS-CoV-2 infection.
• To identify the expression of SARS-CoV-2 entry-related proteins (ACE2 and TMPRSS2) in lung tissues.

Main Methods:

• Post-mortem autopsies and lung tissue analysis of nine patients who died from SARS-CoV-2.
• Histological examination for diffuse alveolar damage (DAD) and vascular changes.
• Immunohistochemistry to detect viral RNA, ACE2, and TMPRSS2 expression.

Main Results:

• All patients exhibited histological changes of DAD in various stages, accompanied by significant vascular involvement, including micro-thrombi and organized thrombi.
• SARS-CoV-2 RNA was detected in lung tissues of all nine patients.
• ACE2 and TMPRSS2 were co-expressed in airway cells; ACE2 was found in endothelial cells and pneumocytes, while TMPRSS2 was expressed in pneumocytes within DAD areas.

Conclusions:

• SARS-CoV-2 infection causes diffuse alveolar damage and vascular thrombosis, contributing to mortality.
• The expression of ACE2 and TMPRSS2 in lung cells supports SARS-CoV-2 cellular entry.
• Histological findings are not entirely specific to SARS-CoV-2, and the cause of death is likely multifactorial.