Multiscale 3-dimensional pathology findings of COVID-19 diseased lung using high-resolution cleared tissue microscopy

Guang Li; Sharon E. Fox; Brian Summa; Carola Wenk; Aibek Akmatbekov; Jack L. Harbert; Richard S. Vander Heide; J. Quincy Brown

The value of 3D imaging in this context is that it allows for much finer sampling of the tissue compared to traditional 2D slide-based histology, which may provide additional information or context that can support standard histology. In our case, by being able to digitally search and select any arbitrary section from mm 3 volumes of the tissue, and to render volumes of interest in 3D, we were able to confirm findings that may have been difficult on single 2D sections due to unlucky sampling, and to visualize the true extent of cytopathic viral changes and damage to the lung from COVID-19. Notably, we were able to confirm the finding of activated mature megakaryocytes in the small vessels of the lung by inspection of their large, multiple, lobular nuclei conforming to the shape of the vessel in 3 dimensions. Additionally, 3D inspection of cells that appeared to be large multinucleated cells on 2D slices, enabled more accurate determination of a cell cluster. Three-dimensional imaging also revealed the massive extent of small vessel thrombosis in the lung. While small deposits of fibrin may be associated with diffuse alveolar damage more generally, 3D imaging allowed us to visualize the pathologic extent of fibrin deposition and clot formation with inflammatory cell attachment, which was far more extensive than revealed in 2D alone, providing additional strong support for the independent role of pulmonary microangiopathy in the pathogenesis of COVID-19 apart from diffuse alveolar damage.