T1771 The Effects of Extracellular Matrices and Growth Factors On Hepatic Lineage Differentiation of Human Embryonic Stem Cells

Abstract

identified each with identical mutations throughout, and are thus clonal. 3D models of these cytochrome c oxidase deficient patches have shown that they have a definite pushing margin and appear to associate with portal tract regions. Patches can occupy large areas i.e. are present in serial sections at least 600μm deep into the tissue. These findings suggest that cells in the normal human liver proliferate as a unit from a common origin e.g. periportal hepatocytes or the biliary epithelium. In addition these clonal patches were shown to be synthetically and metabolically functional with a characteristic proliferative rate and did not express the pro-oncogenic marker α-fetoprotein, establishing that they are representative of the liver in its standard state. This study allows us to directly track stem cell clones and their progeny and highlights a highly clonal cell type within the liver, surpassing the levels of replication expected before senescence is reached. Future studies will look at identifying cytochrome c oxidase deficient patches that not only contain the founder mutation, but also subsequent mutations that have arisen while the patch has expanded, leading to the formation of a traceable phylogenetic tree that may allow a direction of growth to be attributed. Reference [1]. Taylor R.W., et al., Mitochondrial DNA mutations in human colonic crypt stem cells. J Clin Invest. 2003 Nov; 112(9): 1351-60. [2]. Greaves, L.C., et al., Mitochondrial DNA mutations are established in human colonic stem cells, and mutated clones expand by crypt fission. Proc Natl Acad Sci USA, 2006. 103(3): p. 714-9.