Epithelial-mesenchymal transition and membrane microparticles: Potential implications for bronchiolitis obliterans syndrome after lung transplantation.

Long term survival post lung transplantation (LTx) is limited by the occurrence of bronchiolitis obliterans syndrome (BOS). One mechanism involved is the epithelial-mesenchymal transition (EMT). Membrane microparticles (MPs) are known to be involved in some respiratory diseases and in other organs allograft rejection episodes. We hypothesized that leukocyte-derived MPs likely contribute to EMT. To emphasize this physiological concept, our objectives were to: (1) confirm the presence of EMT on explanted lungs from patients who underwent a second LTx for BOS; 2) characterize circulating MPs in transplanted patients, with or without BOS; (3) evaluate in vitro the effect of monocyte-derived MPs in EMT of human bronchial epithelial cells. Our IHC analysis on explanted graft lungs revealed significant pathological signs of EMT with an inhomogeneous destruction of the bronchial epithelium, with decreased expression of the epithelial protein E-cadherin and increased expression of the mesenchymal protein Vimentin. The immunophenotyping of MPs demonstrated that the concentration of MPs carrying E-cadherin was lower in patients affected by BOS (p = .007). In vitro, monocyte-derived MPs produced with LPS were associated with decreased E-cadherin expression (p < .05) along with significant morphological and functional cell modifications. MPs may play a role in EMT onset in bronchial epithelium following LTx.