The mechanism of liver size control in mammals: a novel animal study

Abstract

The liver, the organ that metabolizes food and chemicals and delivers nutrients to body tissues, is essential to vertebrate life. The architecture of the liver is adequately designed such that its activity is precisely aligned with individual body requirements, neither over- nor underperforming. Thus, liver weight (W liver ) is correlated with body weight (W body ). In any vertebrate species, the ratio (R L/B ) of W liver to W body is relatively constant among adults with fully functional mature livers. Recently, we created a mouse (chimeric mouse) with a liver composed of xenogenic hepatocytes and showed that the mouse can be used as a novel experimental animal model to study the mechanism of R L/B optimization. Liver tissue is generated via two different processes, embryonic liver organogenesis and liver regeneration in adults, and R L/B is optimized in the course of these biological phenomena. Although liver organogenesis and regeneration have been abundantly studied and mice with chimeric liver have been characterized intensively, very few studies have investigated these biological processes in the mouse model with such chimerism in relation to the regulation of R L/B . In this article, we review these previous studies on liver embryogenesis, regeneration and liver-chimeric mice from a viewpoint of R L/B regulation to make it appeal that the chimeric mouse is a novel and useful animal model to investigate the R L/B optimization at the cellular and molecular levels.