HMGB2 is important for liver regeneration through transient accumulation of lipid droplets in hepatocytes

Liver regeneration is an well orchestrated compensatory process that regulated by multiple factors. We recently reported the importance of chromatin protein, a high-mobility group box 2 (HMGB2) in mouse liver regeneration, however, it’s molecular mechanism is not yet understood. In this study, we aimed to study how HMGB2 regulates hepatocyte proliferation during liver regeneration. Wild-type (WT) and HMGB2-knockout (KO) mice were 70% partial hepatectomized (PHx), and liver tissues were analyzed by microarray, immunohistochemistry, qPCR and western blotting. In vivo experimental findings were confirmed by in vitro experiments using HMGB2 gene knockdown in combination with de novo lipogenesis model. In WT mouse, HMGB2-positive hepatocytes were co-localized with cell proliferation markers, whereas, hepatocyte proliferation was significantly decreased in HMGB2-KO mice. Oil red-O staining detected the transient accumulation of lipid droplets at 12-24 h in WT mouse livers, however, decreased amount of lipid droplets were found in HMGB2-KO mouse livers, and it was prolonged until 36 h. Microarray, immunohistochemistry and qPCR results were demonstrated that lipid metabolism related genes were significantly decreased in HMGB2-KO mouse livers. In vitro experiments demonstrated that decreased lipid droplets in HMGB2-knockdown cells correlated with decreased cell proliferation activity. HMGB2 is involved in the regulation of liver regeneration through transient accumulation of lipid droplets in hepatocytes. Microarray analysis was used to screen for genes that are related to HMGB2 expression. RNA was isolated from WT and HMGB2-KO mouse livers (n = 3 each), and cRNA was prepared. cRNA from each sample was hybridized to a pre-equilibrated Clariom S mouse microarray chip, which was then washed, stained, and scanned in an HP ChipScanner (Affymetrix Inc., Santa Clara, USA).