Single-cell profiling reveals monocyte heterogeneity and association with liver fibrosis in patients with chronic HBV.

BACKGROUND: Chronic hepatitis B (CHB) infection results in persistent liver inflammation, which ultimately leads to liver fibrosis and increases the risk of cirrhosis. Recruitment of circulating monocytes to the liver is an essential aspect that exacerbates liver fibrosis; however, the mechanism underlying their dysregulation, which contributes to this progression, remains unclear. METHODS: Single-cell RNA sequencing was performed to characterize the landscape of circulating monocytes from patients with CHB and liver fibrosis (CHB group) and healthy controls (HC group). Conventional techniques were performed to validate the findings. RESULTS: Monocytes significantly expanded in the CHB group. The proto-oncogene LIM domain only 2 (LMO2) was highly expressed in monocytes from the CHB group, which may be associated with their expansion. In addition, we noticed that a classical monocyte subcluster surged in the CHB group and highly expressed platelet-related genes such as ITGA2B, which was identified as monocyte-platelet aggregates (MPA). The frequency of MPA was significantly higher in the CHB group, positively associated with platelet and white blood cell, and negatively associated with liver fibroscan and age, which indicates that MPA may play an important role in liver inflammation in the early liver fibrosis stage. Moreover, we found that MPA displays the enrichment of chemokine signaling-associated genes, such as C-C chemokine motif ligand 5 (CCL5), and showed an increased adhesion capacity to endothelial cells. After incubation with MPA cell supernatants, pro-inflammatory factors such as IL-8 and IL-1β were upregulated in LX-2 cells, which were reversed by the addition of anti-CCL5 antibodies. CONCLUSIONS: Our data suggest that enhanced LMO2 expression in circulating monocytes may be associated with their expansion, and an increased MPA subset may participate in liver fibrosis progression. These results provide valuable insights into the etiology of liver fibrosis in patients with CHB.