Aggregated eosinophils characterize airway mucus properties

Uncontrolled airway mucus is associated with diverse diseases. We hypothesized that the physical characteristics of infiltrating granulocytes themselves affect the clinical properties of mucus. Surgically obtained nasal mucus from patients with eosinophilic chronic rhinosinusitis (ECRS) and neutrophil-dominant non-eosinophilic chronic rhinosinusitis (non-ECRS) was assessed in terms of computed tomography (CT) density, viscosity, water content, wettability, and granulocyte-specific proteins. In an observational study, we found that nasal mucus from patients with ECRS had significantly higher CT density, viscosity, dry weight, and hydrophobicity than mucus from patients with non-ECRS. The levels of eosinophil-specific proteins in nasal mucus correlated with its physical properties. When isolated human eosinophils and neutrophils were stimulated to induce extracellular traps followed by aggregate formation, we found that cell aggregates showed physical and pathological findings that closely resembled mucus. Co-treatment with heparin (which slenderizes the structure of eosinophil extracellular traps) and DNase efficiently induced a reduction in the viscosity and hydrophobicity of both eosinophil aggregates and eosinophilic mucus. The present study highlights the pathogenesis of mucus stasis in infiltrated granulocyte aggregates from a new perspective. The combination of DNase and heparin might be a novel therapeutic modality against pathologic viscous eosinophilic mucus. One Sentence Summary Intraluminal accumulation and activation of eosinophils contribute to the clinical properties of airway mucus and may serve as a therapeutic target. ### Competing Interest Statement SU received grants and personal fees from AstraZeneca, GlaxoSmithKline, Sanofi, and grants from Novartis, VIB, and Maruho Co. Ltd. TY received honoraria from Mitsubishi Tanabe Pharma, Novartis, Sanofi, Taiho and Kyorin Pharma. IM received honoraria from AstraZeneca, Sanofi, Shionogi, Japan Blood Products, Takeda, and Meiji pharma. KA received honoraria from AstraZeneca, Boehringer Ingelheim Co., Ltd, GlaxoSmithKline plc., Novartis Pharma, and Sanofi. ### Funding Statement AstraZeneca Evidence Connect Externally Sponsored Research (SU) Charitable Trust Laboratory Medicine Research Foundation of Japan (SU) JSPS KAKENHI 15KK0329, 20K08794, 21K08434, and 21K07833 (SU) JSPS KAKENHI 17K09993 (MT) JSPS KAKENHI 17K17611 (YK). JSPS KAKENHI 22K08598 (IM) JSPS KAKENHI 17K11356, 25293348, and 20H03832 (TY) Research Grant on Allergic Disease and Immunology from the Japan Agency for Medical Research and Development JP22ek0410097 (KA) Conselho Nacional de Desenvolvimento Cientifico e Tecnologico 406019 and 309734 (RCNM) Fundacao de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG) (RCNM) ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: All experiments were approved by the Akita University institutional review board, protocol approval No. 994, 1965. Written informed consent was obtained from all participants in accordance with the principles laid out in the Declaration of Helsinki. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors