Pulmonary Neuroendocrine Cells Regulate Gas Exchange Through Controlling Lung Fluid Balance

Limiting fluid in lung is critical for efficient gas exchange. Here we discovered a mechanism of neuropeptidergic control of lung fluid balance by pulmonary neuroendocrine cells (PNECs), potent sensors of chemical and mechanical cues. We studied the first animal model of neuroendocrine cell hyperplasia of infancy (NEHI), which faithfully recapitulated patient phenotypes including PNEC hyperplasia and impaired gas exchange. Double mutants showed that increased PNECs and excess PNEC products such as CGRP are responsible for poor gas exchange, acting through downregulating endothelial junctions, increasing vessel leakage and fluid accumulation. Endothelium-specific inactivation of CGRP receptor, or treatment with CGRP receptor antagonist reduced fluid and improved gas exchange. In lungs with acute respiratory distress syndrome (ARDS), including those caused by COVID-19, there was a striking increase of CGRP-expressing PNECs. These findings raise the possibility that increased neuropeptides would contribute to excess extravascular lung fluid and antagonizing their function may improve gas exchange. Overall design: Single-cell suspensions were prepared from 3 whole mouse lungs (gender mixed) for each indicated genotype. Live epithelial and endothelial cells were FACS-sorted and re-proportionated with 2:1 ratio before loading. Single-cell barcoded droplets were produced using 10X Single Cell 3' v3 chemistry following user guide provided by 10X Genomics. Libraries generated were sequenced using Illumina Novaseq instrument. Reads were aligned and gene level unique molecular identifier (UMI) counts were obtained using the Cell Ranger pipeline. Cell clustering and gene expression profile in different cell type and conditions are performed by Seurat (version 3.0) package.