Figure 4. Measurement of collagen:elastin ratio.
The density of collagen and elastin fibers distribution in the lung
parenchyma was measured in COVID-19 positive and COVID-19 negative
patients. Adjacent lung sections stained with Masson’s trichrome and
orcein from (A, B) non-COVID-19 patient (A, collagen - black arrow) and
(B, elastin – black arrowhead). COVID-19 patient lungs displayed
widespread (C) collagen deposition, (D) complete loss of elastin. (E)
The collagen:elastin ratio was quantified using ImageJ analysis as
described in the methods. (F-H) Areas of fibrosing organizing pneumonia
also displayed (G) extensive loss of alveolar epithelium stained with
TTF-1 (yellow line), while undamaged areas show positive staining for
TTF-1 and elastin (red arrow). Scale bar=100 μm.