Ex vivo human airway epithelia modelling reveals specific alterations in lung and hematopoietic stem cell transplant recipients

Deterioration of lung function is a major cause of long-term morbidity after hematopoietic stem cell transplantation (HSCT) and lung transplantation (LT). In both settings, obliterative bronchiolitis represents the most common final pathway, with bronchiolitis obliterans syndrome (BOS), representing its clinical correlate. Understanding of the pathophysiological mechanisms leading to BOS is limited by restricted access to human lung tissue and the imperfect relevance of animal models. We hypothesize that transplantation procedures cause bronchial epithelial damage that promotes the development of BOS. To investigate this, we established ex vivo human airway epithelia (HAE) cultures from bronchial biopsies of HSCT and LT recipients, collected prior to the development of BOS, and compared them with non-transplant controls. HAE from HSCT recipients exhibited reduced tissue differentiation ability, associated with defect in mucociliary clearance and impaired barrier integrity, most markedly in one patient who subsequently developed BOS. In contrast, LT-derived HAE showed normal mucociliary clearance and barrier integrity but displayed increased mucin secretion. Donor and recipient-derived cells were detected in both paraffin-embedded biopsies and reconstructed HAE derived from transplant recipients, demonstrating epithelial chimerism. Our data highlight specific modifications of the airway epithelium after LT and HSCT that may represent a first trigger for subsequent BOS development.