Abstract
Type II alveolar epithelial cells (ATIIs) show clonal proliferation upon alveolar injury. During physiological healing transdifferentiation (TD) into Type I alveolar epithelial cells (ATIs) follows. On the contrary, pathological healing comprises tissue remodelling and fibrosis in chronic diseases of the lung. We aimed to identify Wnt ligands and Frizzled (Fzd) receptors which are involved in ATII→ATI TD. To examine spontaneous in vitro TD, we cultured human primary ATII cells isolated from lobectomy patients with normal lung function (n=11) for 3 and 6 days and processed cells for an Affimetrix microarray. Data analysis showed that more than 30% of significant (p<0.01) gene expression changes involved the Wnt signalling pathway. We selected Wnt4, Wnt5a, Wnt7a ligands and Fzd1, 2, 4, 5 and 7 receptors for further analysis to confirm gene expression changes using real-time qPCR. To compare data from in vitro cultured cells to freshly isolated cells, we FACS-sorted ATII-like and ATI-like cells from enzymatically digested human lung tissue based on EpCAM and CD208 or T1a/PDPN expression, respectively (n=12). Our qPCR data indicate that Wnt4, Wnt5a, Wnt7a expression is significantly (p<0.05) lower and Fzd2 is significantly higher in ATII-like cells than in ATI-like cells. Understanding ATII→ATI TD is a priority in revealing the molecular background of alveolar epithelial repair. Our microarray data indicate that Wnt signalling is particularly active during this process. Identification the components of Wnt signalling involved in the transdifferentiation process is the first step to mark molecular targets of future therapies.
- © 2014 ERS