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

Abstract

A relevant number of coronavirus disease 2019 (COVID-19) survivors suffers from post-acute sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-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 morphologic and transcriptomic features of alveolar regeneration in SARS-CoV-2 infected Syrian golden hamsters. We demonstrate that CK8+ alveolar differentiation intermediate (ADI) cells accumulate following SARS-CoV-2-induced diffuse alveolar damage. A subset of ADI cells shows nuclear accumulation of p53 at 6- and 14-days post infection (dpi), indicating a prolonged block in the ADI state. Transcriptome data shows 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, persistence 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 study provides a suitable translational model for future research on the pathomechanims of PASC and testing of prophylactic and therapeutical approaches.

Evaluation of Nafamostat as Chemoprophylaxis for SARS-CoV-2 Infection in Hamsters

“…The findings are consistent with those reported in hamsters 4 days after wildtype SARS-CoV-2 infection [20]. In three animals there were changes consistent with early regenerative attempts, i.e., mild hyperplasia of type II pneumocytes/bronchiolar epithelial cells (Figure 6A); these have previously been reported to be present already at this timepoint [20,21]. All donors exhibited degeneration of respiratory epithelial cells and a variably intense neutrophil-dominated rhinitis, in which the detection of viral N-RNA and/or NP confirmed the infection.…”

“…With the nafamostat treatment, two thirds of the sentinel animals tested negative by all approaches at 4 dpi, and there was generally no viral antigen detected. However, several of these animals showed focal type II pneumocyte/bronchiolar epithelial cell hyperplasia, which is consistent with regenerative attempts after infection, as it can be seen as early as 3 days post infection in the hamster model of COVID-19 [20,21]. Some discrepancies were observed between the results of the different approaches to detect and quantify infection.…”

“…The remaining two sentinels in cage 9 (nafamostat-treated hamsters #11 and 12) did not exhibit histological changes, viral N-RNA or NP expression in the lungs and tested negative for live virus through the plaque assay, but were found to carry the virus in the nasal cavity, as shown by the detection of viral N-RNA. All other sentinel animals exhibited histological changes in the lung suggestive of prior infection [20,21], which is mainly represented by focal areas with leukocyte infiltrates, activated type II pneumocytes and minimal hyperplasia of type II pneumocytes/bronchiolar epithelial cells (nafamostat-treated hamsters #1-5, 7-9, and 13-15) (Figure 6C). Live virus was detected in the plaque assay of nafamostat-treated hamsters #1-5 and 7, but was undetectable in nafamostat-treated hamsters #8-15.…”

SARS-CoV-2 immunity in animal models

“…Despite viral clearance, both the olfactory bulb and olfactory epithelium exhibited myeloid and T-cell activation, proinflammatory cytokine production, and an interferon response [68]. Another hamster model study indicated that SARS-CoV-2 infection induced dysregulated alveolar regeneration and subpleural fibrosis [107].…”

MVA-ST Vaccination in an Aged-Hamster Model for COVID-19 Overcomes Age-Related Immune Dysfunction and Robustly Activates T Cells and Antibodies

“…Blood vessels as well as artifacts were subtracted from the total lung tissue as they were indicated as ROIs. Automated positive cell detection was used, as previously described [14], to quantify the immune-stained cells in the lung tissue. This was based on marker-specific thresholding parameters.…”