Single‐cell <scp>RNA</scp> sequencing of cystic fibrosis liver disease explants reveals endothelial complement activation

Abstract Background &amp; Aims Cystic fibrosis (CF) is considered a multisystemic disorder in which CF‐associated liver disease (CFLD) is the third most common cause of mortality. Currently, no effective treatment is available for CFLD because its pathophysiology is still unclear. Interestingly, CFLD exhibits identical vascular characteristics as non‐cirrhotic portal hypertension, recently classified as porto‐sinusoidal vascular disorders (PSVD). Methods Since endothelial cells (ECs) are an important component in PSVD, we performed single‐cell RNA sequencing (scRNA‐seq) on four explant livers from CFLD patients to identify differential endothelial characteristics which could contribute to the disease. We comprehensively characterized the endothelial compartment and compared it with publicly available scRNA‐seq datasets from cirrhotic and healthy livers. Key gene signatures were validated ex vivo on patient tissues. Results We found that ECs from CF liver explants are more closely related to healthy than cirrhotic patients. In CF patients we also discovered a distinct population of liver sinusoidal ECs—coined CF LSECs—upregulating genes involved in the complement cascade and coagulation. Finally, our immunostainings further validated the predominant periportal location of CF LSECs. Conclusions Our work showed novel aspects of human liver ECs at the single‐cell level thereby supporting endothelial involvement in CFLD, and reinforcing the hypothesis that ECs could be a driver of PSVD. Therefore, considering the vascular compartment in CF and CFLD may help developing new therapeutic approaches for these diseases.