The Regulation Of Alveolar Stem Cells By Oxidateive Stress In Idiopathic Pulmonary Fibrosis

Objective: The main function of the lung is the ventilation and gas exchange.The ventilation includes the inhalation and exhalation between the lung and the outside air.The gas exchange occurs between the alveolar surface and the blood vessels inside the lung tissue.In the adult lung,there are more than 40 types of cells.The lung epithelial cells cover the surface of the respiratory tract,and different parts of the respiratory tract have different types of epithelial cells.Type 1 alveolar epithelial cells?AT1?and type 2 alveolar epithelial cells?AT2?locates in alveolar space.Type 2 alveolar epithelial cells have multiple functions.First of all,they are capable of secreting a variety of alveolar surfactants.These alveolar surfactants can reduce alveolar surface tension and increase lung compliance.They also have antioxidant and antibacterial effects.In the course of lung tissue renewal and repair,type 2 alveolar epithelial cells can regenerate new type 2 alveolar epithelial cells,and they can also differentiate into type 1 alveolar epithelial cells.AT2 cells,therefore,are considered to be stem cells of alveolar epithelium.In idiopathic pulmonary fibrosis?IPF?,alveolar epithelium is demonstrated to be severely damaged.Howver,the underlying mechanism remains unexplored.In present study,we observed that oxidative stress occurs in lungs of bleomycin-induce injury.Hydrogen peroxide concentration increases in lung lavage.We later cultured AT2 in presence of H₂O₂ to examine the possible role of H₂O₂ in regultaiton of AT2 cells.We found that H₂O₂ decreases both proliferation and differentiation of AT2 cells.This preliminary data provide a piece of evidence to reveal pathological mechanism of alveolar epithelial damage occured in IPF.Method: 1.Establishment of BLM-induced mouse fibrosis model,H&E staining and masson staining to observe pathological changes of pulmonary fibrosis in mice.2.Determination of Hydrogen Peroxide in Mouse Bronchial Lavage Fluid After BLM Modeling.3.Using flow cytometry to extract AT2 cells,3D culture to observe the proliferation and differentiation of AT2 cells 4.In vitro 3D culture type 2 alveolar epithelial cells,the control group only added basic medium,the experimental group was added 1mM H₂O₂,analysis proliferation and differentiation of AT2 cells.RNA was extracted from the cells and real-time quantitative PCR?qRT-PCR?was used to determine the expression level of related genes.Result: 1.In BLM-induced mouse fibrosis model,alveolar epithelium was impaired and AT2 cell proliferation was significantly decreased.2.BLM-induced lung fibrosis in mice,the concentration of hydrogen peroxide in the mouse bronchial lavage fluid significantly increased.3.Hydrogen peroxide stimulated AT2 cells,resulting in decreased proliferation and differentiation of AT2 cell.Conclusion: Oxidative stress inhibits the proliferation and differentiation of AT2 cells in BLM-induced lung fibrosis in mice.The pathological mechanism of alveolar epithelial damage in patients with IPF was revealed from a perspective of regenerative medicine.