Mechanobiology in the development and progression of non-alcoholic fatty liver disease: an updated review

Mechanobiology is a rapidly emerging field focused on the biological impact of physical forces at the molecular, cellular, and tissue level. Living cells perceive mechanical cues and transform them into biochemical signals through mechanotransduction. Mechanotransduction is a complex process that involves mechanosensors (which are located in the plasma membrane or within the cell) and mechanotransmission to the nucleus (which occurs either by physical connection between the mechanosensor and the nucleus or by mechanosignaling through biochemical pathways). Essential biological functions, including development, growth, motility, and metabolism, depend on the mechanoresponses generated by these events. Multiple lines of evidence indicate that disruption of mechanical homeostasis may contribute to the pathogenesis of non-alcoholic fatty liver disease (NAFLD), a highly prevalent metabolic disorder characterized by abnormal accumulation of lipid droplets in hepatocytes (steatosis) and often associated with inflammation and liver cell injury (steatohepatitis). While predicting individual predisposition to adverse outcomes in NAFLD remains a challenge, there is increasing evidence that steatosis and steatohepatitis trigger mechanoresponses that contribute to the early stages of pathogenesis in NAFLD and critically impact disease progression. Lipid accumulation and lipotoxicity modify liver viscoelasticity, alter the biomechanics of liver sinusoids, and initiate aberrant pathways of mechanotransduction in hepatocytes and non-parenchymal liver cells, such as sinusoidal endothelial cells and hepatic stellate cells. Interactions of these cells at mechanical interfaces with each other, with extracellular matrix, and with sinusoidal blood flow are profoundly altered by steatosis and steatohepatitis; such changes may promote a pro-angiogenic and pro-fibrotic milieu. A better understanding of liver mechanobiology may facilitate the identification of novel molecular and cellular targets in the management of NAFLD.