Interleukin-7-based identification of liver lymphatic endothelial cells reveals their unique structural features
Yilin Yang,
Jain Jeong,
Tingting Su,
Sanchuan Lai,
Pengpeng Zhang,
Rolando Garcia-Milian,
Morven Graham,
Xinran Liu,
Matthew J. McConnell,
Teruo Utsumi,
Joao Pereira,
Yasuko Iwakiri
Affiliations
Yilin Yang
Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, New Haven, CT, USA
Jain Jeong
Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, New Haven, CT, USA
Tingting Su
Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, New Haven, CT, USA; Department of Gastroenterology, First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
Sanchuan Lai
Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, New Haven, CT, USA; Department of Gastroenterology, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
Pengpeng Zhang
Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, New Haven, CT, USA; The Transplantation Center of the Third Xiangya Hospital, Central South University, Changsha, China
Rolando Garcia-Milian
Bioinformatics Support Hub, Cushing/Whitney Medical Library, Yale University School of Medicine, New Haven, CT 06510, USA
Morven Graham
Center for Cellular and Molecular Imaging, Yale University School of Medicine, New Haven, CT, USA
Xinran Liu
Center for Cellular and Molecular Imaging, Yale University School of Medicine, New Haven, CT, USA
Matthew J. McConnell
Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, New Haven, CT, USA
Teruo Utsumi
Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, New Haven, CT, USA
Joao Pereira
Department of Immunobiology and Yale Stem Cell Center, Yale University School of Medicine, New Haven, CT, USA
Yasuko Iwakiri
Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, New Haven, CT, USA; Corresponding author. Address: Section of Digestive Diseases, Department of Internal Medicine, Yale University School of Medicine, TAC S223B, 333 Cedar Street, New Haven, CT 06520, USA. Tel.: +1-203-785-6204; Fax: +1-203-785-7273.
Background & Aims: The lymphatic system plays crucial roles in maintaining fluid balance and immune regulation. Studying the liver lymphatics has been considered challenging, as common lymphatic endothelial cell (LyEC) markers are expressed by other liver cells. Additionally, isolation of sufficient numbers of LyECs has been challenging because of their extremely low abundance (<0.01% of entire liver cell population) in a normal liver. Methods: Potential LyEC markers was identified using our published single-cell RNA sequencing (scRNA-seq) dataset (GSE147581) in mouse livers. Interleukin-7 (IL7) promoter-driven green fluorescent protein knock-in heterozygous mice were used for the validation of IL7 expression in LyECs in the liver, for the development of liver LyEC isolation protocol, and generating liver ischemia/reperfusion (I/R) injury. Scanning electron microscopy was used for the structural analysis of LyECs. Changes in LyEC phenotypes in livers of mice with I/R were determined by RNA-seq analysis. Results: Through scRNA-seq analysis, we have identified IL7 as an exclusive marker for liver LyECs, with no overlap with other liver cell types. Based on IL7 expression in liver LyECs, we have established an LyEC isolation method and observed distinct cell surface structures of LyECs with fenestrae and cellular pores (ranging from 100 to 400 nm in diameter). Furthermore, we identified LyEC genes that undergo alterations during I/R liver injuries. Conclusions: This study not only identified IL7 as an exclusively expressed gene in liver LyECs, but also enhanced our understanding of LyEC structures and demonstrated transcriptomic changes in injured livers. Impact and implications: Understanding the lymphatic system in the liver is challenging because of the absence of specific markers for liver LyEC. This study has identified IL7 as a reliable marker for LyECs, enabling the development of an effective method for their isolation, elucidating their unique cell surface structure, and identifying LyEC genes that undergo changes during liver damage. The development of IL7 antibodies for detecting it in human liver specimens will further advance our understanding of the liver lymphatic system in the future.
