Impact of LSECs on liver fibrogenesis in congestive liver Young Award

Background and Aim: The detail mechanism of fibrosis in congestive liver remains unclear. We aimed to elucidate it focusing on liver sinusoidal endothelial cells (LSECs). Methods: Partial IVC ligation (pIVCL) was performed to induce congestive liver in mice. Single-cell RNA sequencing (scRNA-seq) was performed using livers from the mice with pIVCL and sham operation at 2 weeks after operation. In vitro experiments, TMNK-1 cells, human-liver endothelial cells, were subjected to mechanical cyclic stretch. Results: At 6 weeks after operation, centrilobular hemorrhagic necrosis, sinusoidal dilation and centrilobular and perisinusoidal fibrosis were observed in the pIVCL-treated mice with the increased expression of COL1A1, ACTA2 and TGFB1. scRNA-seq identified the heterogeneity of LSECs. CTGF was the most greatly upregulated gene in the whole LSEC population and more upregulated in zone 3 LSECs than zone 1 LSECs. CTGF was upregulated only in LSEC and hepatic stellate cell populations among all the identified clusters. By real-time PCR, CTGF expression in LSECs was significantly higher in the pIVCL-treated mice. In vitro experiments, CTGF expression in liver endothelial cells was upregulated by mechanical cyclic stretch. We generated tamoxifen-inducible vascular endothelial cell-specific CTGF knockout mice (Cdh5-CreERT2+ CTGF^fl/fl), followed by pIVCL. pIVCL-induced liver fibrosis was ameliorated by CTGF KO in endothelial cells. Conclusions: In congestive livers, mechanical stress upregulates CTGF expression in LSECs, which are responsible for the development of fibrosis.