Development Of BO Mice Model And Prospective Study Of Post Infectious BO In Children

Part?: Development of BO Mice ModelBronchiolitis obliterans(BO) is a rare, but highly debilitative and fatal syndrome associated with a series of severe lower airway disorders. It is characterized clinically by cough, wheeze, and exertional dyspnea, and pathologically by small airway narrowing and/or complete obliteration resulting from inflammatory infiltration and fibrosis of bronchiolar walls and contiguous tissues. In another word, BO could be a final outcome from severe lower respiratory tract insults, such as infection, transplantation, toxic fume inhalation, drugs(eg. penicillamine), connective tissue diseases, hypersensitivity pneumonitis, and even inflammatory bowel disease. However, the pathogenesis of BO is complicated and not entirely understood until now, and there is no specific therapy towards BO. An appropriate animal model of BO may aid research into its pathogenesis. Several transplant animal models have previously been developed, including the orthotopic lung and tracheal transplantation in large animals and heterotopic transplantation of a trachea in variable sites(such as subcutaneous pocket, intraomental, and intrapulmonary). Transplant models provide insights into the immune pathogenesis of BO, but may not capture critical mechanisms involved in BO caused by other conditions. Thus, establishment of an appropriate non-transplant BO animal model is of great importance.Nitric acid(NA) is a corrosive acid and a strong oxidizing agent. Mild concentration of NA burns tissues and induce local inflammation. In previous studies, intratracheal administration of NA to rabbits, hamsters and rats can induce BO lesion. The most common mammal used in animal model setting up is mice. There are many advantages of mice accepted by scientists, such as ease of maintenance and handling, short life-span, high reproductive rate, large amount of available commercial antibodies, and ease of genetic modification. Analysis of the mouse genome indicates that virtually all mouse genes have human homologs, thus any alterations in normal mice or in the established genetically engineered knockout mouse could imply the corresponding health or disorder in humans. Therefore, a mice BO model will greater contribute to the study of pathogenesis and therapy. We thus developed a BO mice model by NA aerosol inhalation in the first part of our study. 6-8 week old BABL/c mice were exposed to 10% NA aerosol through a nebulizer for 3 hours, and controls were exposed to distilled water instead. Symptoms and airway resistance were recorded dynamically. The histological changes, airway inflammatory infiltrates, and the levels of matrix metalloproteinase-2(MMP-2), MMP-9, tissue inhibitor of metalloproteinase-1(TIMP-1), 8-isoprostane and myeloperoxidase(MPO) in lung tissue and bronchoalveolar lavage fluids(BLAF) were determined by ELISA on day 3, 7, 14, 28 and 56 after the aerosol nebulization.In the experimental group, the mice exhibited distinct labored breathing immediately after 10% NA aerosol exposure, accompanied with a rapid weight reduction, reduced physical activity, and rusty and rough fur. The Penh and RL were increased significantly, and the MV, PIF, PEF and Cdyn were decreased when detected the mice lung function. These symptoms exacerbated in the first week after NA exposure. The overall mortality rate was 18.7% in total. After one week, the condition of surviving mice improved gradually and returned to normal 2-3 weeks later. We also investigated the airway inflammatory infiltration, and found the total number of each kind of inflammatory cells in model group mouse BALF was considerably higher than that of control mice in the first week after nebulization. Typical BO lesions were observed in NA nebulized mice characterized histologically by initial necrotizing bronchiolitis and final airway fibrosis at day 28 after the aerosol nebulization. Expression of MMP-2, MMP-9, TIMP-1, 8-isoprostane and MPO were significantly elevated in NA nebulized mice in different time frame.In conclusion, we developed an easy and reproducible murine BO model by NA aerosol inhalation. This model successfully mimics the histological characteristics of BO in human. In addition, we described the clinical manifestations, features of inflammation infiltrates, airway resistance, and the variation in several important mediators observed during BO progression. Based on the advantages of mice, this model provides a widespread application for research into BO. Part?: Prospective Study of Post Infectious BO in ChildrenIn children, BO are most commonly induced by infection, and named post infectious BO(PIBO). Adenovirus is the most common etiologic agent, others include respiratory syncytial virus, measles, and mycoplasma pneumoniae, etc. PIBO mainly presents with repeated cough, wheezing, exertional dyspnea, and lung crackles. High-resolution computed tomography(HRCT) usually demonstrates mosaic perfusion, bronchial wall thickening, and air trapping. Lung function is characterized by severe and fixed obstruction, with little or no response to bronchodilator. There is no specific therapy aimed at this irreversible small airway disease until now. Empiric therapy includes oral azithromycin, corticosteroid, and bronchodilator when accompanied with acute infection. However, controversy exists all the time. In order to recognize the clinical features and evaluate the effectiveness of present therapy, we prospectively studied the clinical characteristics, HRCT findings, pulmonary function changes and the reaction of therapy of 42 children diagnosed with PIBO at the First Hospital of Jilin University in northern China between January, 2011 and December, 2015. We found that adenovirus and mycoplasma pneumoniae induced severe lower airway infection was probably the risk factor of PIBO in mainland China. The majority were male and from rural area. Based on the typical history, HRCT and lung function findings, a clinical diagnosis can be made promptly. In a short-term follow-up, lung function seems to be more useful in assessing the patients' condition. Oral azithromycin + oral corticosteroid + inhaled steroid seem to be curative of PIBO.