Abstract: Objective To investigate the proliferation potential of the basal stem cells in intralobar pulmonary sequestration syndrome (ILS) for revealing the pathogenesis of ILS. Methods In this study, lung tissue samples were collected from healthy control subjects (n=4) and abnormal lung lobes of ILS patients (n=4). The pathological changes were compared by HE staining between the two groups. The proportion of goblet cells was compared by PAS staining between the two groups. The expression and secretion of MUC5AC and MUC5B were compared by immunofluorescence staining and realtime PCR between the two groups. The distribution of ciliated cells and the proliferation of basal cells were compared by immunofluorescence staining between the two groups. Results The abnormal lobe of ILS group was filled with inflammatory cells, and the airway epithelium was disrupted. The airway goblet cells of ILS were obviously hyperplastic. The mucin proteins of MUC5AC and MUC5B were hypersecretion in the abnormal lobe of ILS patients. KRT5-positive basal stem cells proliferated only slightly in ILS patients, although there was no significant difference in KRT5 expression between two groups. Conclusion These data suggest that the pathogenesis of ILS may be associated with defects in basal stem cell function. Restoring airway integrity by targeting epithelial regeneration can be a future non-surgical treatment for patients with ILS.

Key words: cell proliferation, mucins, infection, intralobar pulmonary sequestration, basal stem cell