The Role Of Insulin-like Growth Factor 1 In Regulating Goblet Cell Metaplasia In Bronchial Asthma

Background:Bronchial asthma(hereinafter referred to as asthma)is a heterogeneous disease characterized by chronic airway inflammation,affecting approximately 1-18% of the population in different countries.According to the report of the National Asthma Research Cooperation Group of China,the direct cost of hospitalization for acute asthma attacks in 2013-2014 was 11,603 RMB per person per episode.Asthma is mainly characterized by wheezing,shortness of breath,chest tightness and/or coughing,accompanied by varying degrees of expiratory airflow limitation,with airway immune cell infiltration,airway remodeling,airway hyperresponsiveness and increased mucus secretion as pathological features.The airway epithelium is the first barrier against environmental stimuli.Epithelial cell injury is a common feature of all asthma phenotypes and is correlated with disease severity.It can act as a physical barrier against environmental stimuli by producing antimicrobial peptides or antiproteases.Mucous secretion is derived from goblet cells in the epithelium.Under normal physiological conditions,mucins have multiple functions such as regulating cell proliferation,inflammation,immune response,intercellular adhesion,and promoting symbiotic interactions between microbiota and epithelial cells.Impaired airway epithelial barrier function and increased mucous secretion may promote colonization of respiratory pathogens,and abnormal expression of mucins leads to airflow obstruction and airway hyperresponsiveness,which promote the development and progression of asthma.The severity of mucus plugging is closely related to lung function level and irreversible airway obstruction,which reduces the effectiveness of bronchodilators or inhaled/systemic steroids.The insulin-like growth factor family(IGFs)plays an important role in metabolism and linear growth,and promotes the development of various diseases such as cancer,cardiovascular disease,and inflammatory lung disease through bidirectional interactions with the immune system.Insulin-like growth factor 1(IGF1)is an endocrine factor that plays an important role in cell proliferation,apoptosis,and differentiation processes,and can interact with various inflammatory mediators.Recent literature has reported that IGF1 can induce airway inflammation,airway hyperresponsiveness,subepithelial fibrosis,and airway smooth muscle proliferation.However,there has been no study on the role of IGF1 in mucus secretion,so we hypothesize that IGF1 may promote high mucus secretion in asthma airways by promoting goblet cell differentiation from ciliated cells,exacerbating goblet cell metaplasia in asthma airway epithelium.Objective:This study aims to explore the role of IGF1 in the development of asthma by using a multi-level approach that combines clinical samples,animal models,and asthma cells.Starting from clinical observations,we will investigate the mechanism of IGF1 in the metaplasia of asthmatic epithelial cells,providing a theoretical basis for further research.Methods:Sputum and airway mucosal samples were collected from patients with asthma and chronic cough(control group).Enzyme-linked immunosorbent assay(ELISA)was used to detect the expression level of IGF1 protein in induced sputum supernatant.Immunofluorescence(IF)was used to detect the expression of IGF1 in airway mucosa.Clinical indicators such as blood routine and pulmonary function were collected for statistical analysis.The IGF1 expression in the lungs of OVA induced asthmatic mice was detected.An OVA-induced asthmatic mouse model was constructed and recombinant mouse IGF1 protein/anti-mouse IGF1 antibody/normal goat Ig G were used for intervention to observe mouse airway resistance,inflammatory cell classification and counting in bronchoalveolar lavage fluid(BALF),degree of lung inflammatory cell infiltration,expression level of IGF1 binding protein,and goblet cell hyperplasia in the airway epithelium.An air-liquid interface(ALI)system was established using primary human bronchial epithelial cells(HBECs)in vitro to simulate asthma.Recombinant human IGF1 protein was used to stimulate HBECs,and immunofluorescence was used to detect goblet cell metaplasia.Results:1.The expression levels of IGF1 in induced sputum and airway mucosa were higher in asthma patients than in patients with chronic cough,and the expression level of IGF1 in induced sputum was positively correlated with the proportion of eosinophils in asthma patients.The m RNA and protein expression levels of IGF1 in lung tissue were higher in OVA-induced asthma mice than in the control group.2.Compared with the OVA group,the OVA+rm IGF1 group of mice had higher airway resistance,total BALF cell count,and proportion of eosinophils.Lung tissue HE staining showed more inflammatory cell infiltration around the airways and blood vessels,and PAS staining showed a large amount of mucus and goblet cell hyperplasia.The levels of IL-4,IL-5,and IL-13 in BALF were higher in the OVA+rm IGF1 group than in the OVA group.In the OVA+anti-IGF1 group,airway resistance,inflammatory cell count,and eosinophil count in BALF were lower than in the OVA group.HE and PAS staining showed significant improvement in the inflammation cell infiltration and airway epithelial goblet cell hyperplasia around the airways and blood vessels,and the levels of IL-4,IL-5,and IL-13 in BALF were downregulated.There was no statistically significant difference in the above indicators between the OVA+Ig G group and the OVA group.3.After IGF1 intervention,compared with the control group,PAS staining showed an increase in goblet cells and mucus in the air-liquid interface-cultured human bronchial epithelial cells.Immunofluorescence showed that the expression of MUC5 AC and CC10 was upregulated in the IGF1 group,and MUC5 AC was coexpressed with CC10,while there was no co-expression between MUC5 AC and P63.Conclusions:There are differences in the expression of IGF1 in sputum,airway mucosa,BALF and lung tissue of asthmatic patients and controls,and the expression level of IGF1 in human sputum is positively correlated with the proportion of eosinophils in sputum.Exogenous rm IGF1 can exacerbate airway hyperresponsiveness,airway inflammation,goblet cell metaplasia,and Th2-type inflammation in asthmatic mice.IGF1 may promote the differentiation of HBECs into columnar cells and then into goblet cells.