Loss of p73 contributes to COPD
Rationale: Multiciliated cell (MCC) loss/dysfunction is common in the small airways of patients with COPD but it is unclear if this contributes to COPD lung pathology. Objectives: To determine whether loss of MCCs causes a COPD-like phenotype in mice and explore a potential role for the transcription factor p73 in COPD. Methods: p73floxE7-E9 mice were crossed with Shh-Cre mice to generate mice lacking MCCs in the airway epithelium. The resulting p73?airway mice were analyzed using electron microscopy, flow cytometry, morphometry, forced oscillation technique, and single-cell RNA sequencing. Further, the effects of cigarette smoke on p73 transcript and protein expression were examined using in vitro and in vivo models and in studies including airway epithelium from smokers and COPD patients. Measurements and Main Results: Loss of functional p73 in the respiratory epithelium resulted in a near-complete absence of MCCs in p73?airway mice. In adulthood, these mice spontaneously developed neutrophilic inflammation and emphysema-like lung remodeling and had progressive loss of secretory cells. Exposure of normal airway epithelium cells to cigarette smoke rapidly and durably suppressed p73 expression in vitro and in vivo. Further, TP73 mRNA expression was reduced in the airways of current smokers (n=82) compared to former smokers (n=69) and p73-expressing MCCs were reduced in the small airways of COPD patients (n=11) compared non-COPD controls (n=12). Conclusions: Loss of functional p73 in murine airway epithelium results in the absence of MCCs and promotes COPD-like lung pathology. In smokers and patients with COPD, loss of p73 may contribute to MCC loss or dysfunction. Overall design: We used PARSE to perfom SPLiT-seq on the pooled lungs of six  2 month-old C57Bl6/J mice Shh.Cre+/Flox-p73 at E7-E9 (Cre_Pos), in addition to the pooled lungs of six 2 month-old C57Bl6/J mice Shh.Cre-/Flox-p73 that are littermates homozygous for the p73 flox E7-E9 allele(Cre_Neg). We used the Evercode WT kit to sequence a total of 20,000 cells pooled between the two conditions. The pooled cells were divided into 4 sublibraries.  In the Parse WT kit, the Cre_Pos sample corresponds to barcoding wells A1-B12 and the Cre_Neg sample corresponds to wells C1-D12.