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

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.

Replication of SARS-CoV-2 in Adipose Tissue Determines Organ and Systemic Lipid Metabolism in Hamsters and Humans (preprint)

Obesity increases the risk for poor outcome in patients with coronavirus disease-19 (COVID-19). However, the role of adipose tissue for viral propagation and potential metabolic implications are not understood. We detected SARS-CoV-2 in adipose tissue of overweight but not lean male COVID-19 patients. SARS-CoV-2 replicates to high titres in cultured mature adipocytes, a process depending on lipid accumulation and mobilization. After intranasal inoculation, we observed high viral replication in fat depots of Golden Syrian hamsters, demonstrating dissemination from the respiratory tract and subsequent propagation in adipose tissue. Following induction of pro-inflammatory responses, expression of de novo lipogenesis enzymes was suppressed in adipose tissue. This specific down-regulation was reflected by lipidomic alterations in plasma of SARS-CoV-2 infected hamsters as well as in hospitalized COVID-19 patients. Overall, our study highlights that adipose tissue is an important site of SARS-CoV-2 replication, contributing to dysregulation of systemic lipid metabolism.Funding: This study was supported by a rapid response grant from the Federal Ministry of Health (BMG; ZMV I 1-2520COR501 to GG), by DFG grants SCHE522/4-1 (LS) and SFB1328, project- ID:335447727 (JH). As part of the National Network University Medicine (NUM) funded by the Federal Ministry of Education and Research (BMBF, Germany), this work was funded within the research consortium DEFEAT PANDEMIcs, grant number 01KX2021 (FH, PL, KP, BO).Declaration of Interests: The authors declare no competing interests.Ethics Approval Statement: The Ethics Committee of the Hamburg Chamber of Physicians reviewed and approved the studies (PV7311, 2020-10353-BO-ff, WF-051/20, WF-053/20). For the preparation of primary human white adipocytes, biopsies of subcutaneous and visceral adipose tissues were taken during bariatric surgery at the Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf. All participants signed an informed consent and the study was approved by the Ethics Committee of the Hamburg Chamber of Physicians (PV4889).