Fig. 4: IL18-hUCMSC significantly ameliorated lung injury, fibrosis, and cell apoptosis at the cellular level.

A, B Mice lung tissue was harvested at 7 dpi and 14 dpi, and lung sections were stained with H&E (A). Scale bars, 100 μm. Quantification of lung injury in each group (lung injury score) was calculated by analyzing alveolar edema (0–4 score), inflammation (0–4 score), bleeding (0–4 score), and interstitial tissue (0–4 score) with a total 16 scores (B). C Mouse lungs were examined for changes in viral load by analyzing the M1 expression of viral gene at 7 dpi and 14 dpi. D, E Collagen deposition of lung sections was assessed by staining for Masson’s trichrome at 14 dpi (D). Scale bars, 100 μm. Collagen deposition was used as a surrogate of fibrosis and was reported as a percentage of the septal area (E). F, G The cell apoptosis in lung tissues was analyzed by flow cytometry, and 7AAD⁺ cells were regarded as apoptotic cells (F); the percentages of 7AAD⁺ cells in different groups were calculated at 7 dpi and 14 dpi (G). The arrows in A and D showed the major features and changes of IHC images in different groups. Data are shown as mean ± SEM. n = 3–10 in each group. *p < 0.05, **p < 0.01, ***p < 0.001.