Identification of the specific cell types expressing CFTR is required for precision medicine therapies for cystic fibrosis (CF). However, a full characterization of CFTR expression in normal human airway epithelia is missing.
To identify the cell types that contribute to CFTR expression and function within the proximal-distal axis of the normal human lung.
Single cell RNA-seq (scRNA-seq) was performed on freshly isolated human large and small airway epithelial cells. Single cell-based RNA in situ hybridization (scRNA-ISH) and quantitative RT-PCR (scqRT-PCR) were performed for validation. In vitro culture systems correlated CFTR function to cell types. Lentiviruses were used for cell-type specific transduction of wild-type CFTR in CF cells.
scRNA-seq identified secretory cells as dominating CFTR expression in normal human large and particularly small airway superficial epithelia, followed by basal cells. Ionocytes expressed the highest CFTR levels but were rare, while expression in ciliated cells was infrequent and low. scRNA-ISH, and scqRT-PCR confirmed the scRNA-seq findings. CF lungs exhibited distributions of CFTR and ionocytes similar to normal controls. CFTR-mediated Cl- secretion in culture tracked secretory cell, not ionocyte, densities. Further, the nucleotide-purinergic regulatory system that controls CFTR-mediated hydration was associated with secretory cells, and not ionocytes. Lentiviral transduction of wild-type CFTR produced CFTR-mediated Cl- secretion in CF airway secretory cells but not ciliated cells.
Secretory cells dominate CFTR expression and function in human airway superficial epithelia. CFTR therapies may need to restore CFTR function to multiple cell types, with a focus on secretory cells.