Abstract Rationale Mucociliary clearance (MCC) in the airway epithelium serves as a primary host defense mechanism that removes inhaled pathogens through coordinated ciliary motion. Obesity has been recognized as a major risk factor for severe viral respiratory infections, including coronavirus disease 2019 (COVID-19). However, the direct effects of obesity on airway ciliary function and MCC during SARS-CoV-2 infection remain poorly understood. This study aimed to elucidate how obesity alters airway ciliary function during SARS-CoV-2 infection. Methods K18-hACE2 transgenic mice were fed a 60% high-fat diet (HFD) for 14 weeks to establish an HFD-induced obese mouse model. Using murine tracheal tissue culture and in vitro SARS-CoV-2 (strain JPN/TY/WK-521) infection models, cilia-driven flow and ciliary beat frequency (CBF) were assessed in the airway epithelium to evaluate MCC. Viral RNA copy numbers were measured by one-step quantitative RT-PCR. Mitochondrial function in airway epithelial cells was analyzed by extracellular flux analysis (Seahorse XF) to measure basal and mitochondrial-derived ATP production. Ultrastructural morphology was examined by transmission electron microscopy (TEM) to assess mitochondrial localization and cristae structure. In addition, tracheal tissues from control mice were treated with or without antimycin A (a mitochondrial complex III inhibitor), and cilia-driven flow, CBF, and viral replication were analyzed. Results At 1 hour post-infection, viral RNA levels were comparable between the two groups; however, at 48 hours, obese mice exhibited significantly higher viral loads than control mice. Short-term SARS-CoV-2 infection increased both cilia-driven flow and CBF in control mice, but this response was abolished in obese mice. Basal cilia-driven flow and CBF were significantly lower in obese mice compared to control mice. Extracellular flux analysis revealed that total ATP production, particularly mitochondrial-derived ATP, was decreased in airway epithelial cells from obese mice compared with those of control mice. TEM demonstrated irregular mitochondrial distribution and poorly defined cristae beneath the ciliary basal bodies in obese epithelial cells. Antimycin A treatment decreased cilia-driven flow and CBF, and increased viral replication in control mice. Conclusions Obesity impairs basal airway ciliary function and diminishes MCC during SARS-CoV-2 infection. Reduced mitochondrial ATP production in obesity contributes to this dysfunction, leading to enhanced viral replication. This impairment may increase susceptibility to and severity of COVID-19 in obesity. This abstract is funded by: a grant-in-aid for scientific research C 25K11450 (to T.F.) from the Japan Society for the Promotion of Science (JSPS KAKENHI Grant Number JP 25K11450) and Japanese Respiratory Foundation Grant (to T.F.).
Yazawa et al. (Fri,) studied this question.