CD177+ Cells Produce Neutrophil Extracellular Traps That Promote Biliary Atresia.

Background & aims: We have previously reported on the potential pathogenic role of neutrophils in biliary atresia (BA). Herein, we aimed to delineate the role of CD177(+) neutrophils in the pathogenesis of BA. Methods: Immune cells from the livers of mice with rhesus rotavirus-induced BA were analysed. Single-cell RNA-sequencing was performed to specifically analyse Gr-1(+) (Ly6C/Ly6G(+)) cells in the liver. Gene expression profiles of CD177(+) cells were analysed using the Smart-Seq RNA-sequencing method, and the patho-genesis of BA was examined in Cd177(-/-) mice. Neutrophil extra-cellular trap (NET) inhibitors were used to determine the role of CD177+ cell-derived NETs in BA-associated bile duct damage, and a pilot clinical study evaluated the potential effects of N-acetylcysteine on NET release in BA. Results: Increased levels of Gr-1(+) cells were observed in the livers of mice with rhesus rotavirus-induced BA. RNA-sequencing analysis revealed that CD177(+) cells were the main population of Gr-1(+) cells and expressed elevated levels of both interferon -stimulated and neutrophil degranulation genes. Cd177(-/-) BALB/c mice exhibited delayed disease onset and reduced morbidity and mortality. High numbers of mitochondria were detected in CD177(+) cells derived from mice with BA; these cells were associated with increased levels of reactive oxygen species and increased NET formation, which induced the apoptosis of biliary epithelial cells in cocultures. In a pilot clinical study, the administration of N-acetylcysteine to patients with BA reduced CD177(+) cell numbers and reactive oxygen species levels, indicating a potential beneficial effect. Conclusions: Our data indicate that CD177(+) cells play an important role in the initiation of BA pathogenesis via NET formation. Lay summary: Neutrophils (a type of innate immune cell, i.e. an immune cell that doesn't target a specific antigen) are thought to play a role in the development of biliary atresia (a rare but potentially lethal condition of the bile ducts that occurs in infants). Herein, we found that neutrophils expressing a particular protein (CD177) played an important role in bile duct damage by releasing a special structure (NET) that can trap and kill pathogens but that can also cause severe tissue damage. A pilot study in patients with biliary atresia showed that inhibiting NETs could have a beneficial effect. (c) 2022 The Author(s). Published by Elsevier B.V. on behalf of European Association for the Study of the Liver. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).