Hamsters are a model for COVID-19 alveolar regeneration mechanisms: an opportunity to understand post-acute sequelae of SARS-CoV-2

A relevant number of coronavirus disease 2019 (COVID-19) survivors suffers from post-acute sequelae of severe acute respiratory syndrome coronavirus 2 (PASC). Current evidence suggests a dysregulated alveolar regeneration in COVID-19 as a possible explanation for respiratory PASC symptoms, a phenomenon which deserves further investigation in a suitable animal model. This study investigates morphological, phenotypical and transcriptomic features of alveolar regeneration in SARS-CoV-2 infected Syrian golden hamsters. We demonstrate that CK8+ alveolar differentiation intermediate (ADI) cells occur following SARS-CoV-2-induced diffuse alveolar damage. A subset of ADI cells shows nuclear accumulation of TP53 at 6- and 14-days post infection (dpi), indicating a prolonged arrest in the ADI state. Transcriptome data show the expression of gene signatures driving ADI cell senescence, epithelial-mesenchymal transition, and angiogenesis. Moreover, we show that multipotent CK14+ airway basal cell progenitors migrate out of terminal bronchioles, aiding alveolar regeneration. At 14 dpi, presence of ADI cells, peribronchiolar proliferates, M2-type macrophages, and sub-pleural fibrosis is observed, indicating incomplete alveolar restoration. The results demonstrate that the hamster model reliably phenocopies indicators of a dysregulated alveolar regeneration of COVID-19 patients. The results provide important information on a translational COVID-19 model, which is crucial for its application in future research addressing pathomechanisms of PASC and in testing of prophylactic and therapeutic approaches for this syndrome.