Macrophage-derived Wnt opposes Notch signaling to specify hepatic progenitor cell fate in chronic liver disease

During chronic injury a population of bipotent hepatic progenitor cells (HPCs) become activated to regenerate both cholangiocytes and hepatocytes. Here we show in human diseased liver and mouse models of the ductular reaction that Notch and Wnt signaling direct specification of HPCs via their interactions with activated myofibroblasts or macrophages. In particular, we found that during biliary regeneration, expression of Jagged 1 (a Notch ligand) by myofibroblasts promoted Notch signaling in HPCs and thus their biliary specification to cholangiocytes. Alternatively, during hepatocyte regeneration, macrophage engulfment of hepatocyte debris induced Wnt3a expression. This resulted in canonical Wnt signaling in nearby HPCs, thus maintaining expression of Numb (a cell fate determinant) within these cells and the promotion of their specification to hepatocytes. By these two pathways adult parenchymal regeneration during chronic liver injury is promoted

MICRONUTRIENT POLICY CHANGE IN SOUTH AFRICA: IMPLICATIONS FOR THE KALEIDOSCOPE MODEL FOR FOOD SECURITY POLICY CHANGE

This review of micronutrient policy processes in South Africa serves as a companion piece to two parallel studies in Malawi and Zambia. All three studies employ the Kaleidoscope Model of policy change to trace the causal forces leading to key micronutrient policy decisions in each of the three countries. After outlining the overall micronutrient policy process in South Africa, the study focuses on policy decisions regarding vitamin A supplementation, fortification with iodine, iron and multinutrient fortificant, and the reduction of sodium in foods