The Apelin Receptor APJ in Hematopoietic Stem Cells/Progenitor Cells in the Early Stage of Non-Alcoholic Steatohepatitis

BACKGROUND: Non-alcoholic steatohepatitis (NASH) is characterized by hepatic steatosis and inflammation with or without fibrosis. The apelin receptor (APJ) is related to angiotensin-like-receptor 1 (AGTRL1). The present study aimed to evaluate APJ as an indicator of the pathophysiology of early-stage NASH. METHODS: APJ expression was evaluated in six tissue samples with histologically proven early-stage NASH using immunohistochemistry (IHC) and immunoelectron microscopy (IEM). RESULTS: On IHC, in control liver tissue, APJ was mainly localized in the aortic artery, although APJ was detected only slightly in the sinusoids. In early NASH liver tissue, on IEM, APJ was observed mainly at the sites of sinusoidal lining cells around the central vein and periportal regions, and at arterial capillaries in the portal tract. With regard to endothelial cells (ECs), one sample showed a hematopoietic stem cell (HSC)/progenitor cell (HPC) partially wrapped with an EC. CONCLUSION: HSCs/HPCs expressing APJ may contribute to the angiogenesis of liver tissue in early-stage NASH.