The endoderm is one of the three vital germ layers in triploblastic animals. It is formed from the epiblast during embryogenesis from cells that migrate toward the center of the developing gastrula. The endoderm provides the epithelial lining of both the digestive and respiratory tracts, and the cells that form the endoderm eventually differentiate to form the stomach, colon, intestines, liver, pancreas and gall bladder, as well as the lining of the trachea, bronchi and alveoli of the lungs.
Although endoderm development is currently less understood than ectoderm and mesoderm development, researchers have successfully generated endodermal cells from ES (embryonic stem) cells. Human PSCs (pluripotent stem cells) can also be differentiated into monolayer cultures of liver hepatocytes and pancreatic endocrine cells. While cells from these monolayer cultures have shown some therapeutic efficacy in animal models, the generation of three-dimensional organs that contain multiple cell types remains a challenge. In a recent publication by Spence et al. (Directed differentiation of human pluripotent stem cells into intestinal tissue in vitro, Nature 2011; 470(7332): 105–109), the authors described how they were able to generate intestinal “organoids” from human PSCs by using a series of growth factor manipulations to induce definitive endoderm formation, posterior endoderm patterning, hindgut specification and morphogenesis. The resulting three dimensional organoids contained villus-like structures and crypt-like proliferative zones. These organoid cultures also comprised a variety of cell types including intestinal stem cell markers, functional enterocytes, goblet cells, Paneth cells and enteroendocrine cells. These recent advances should pave the way for more studies using PSCs to study development and disease.
The future is stem cell research is highly dependent on the availability of reliable markers for endodermal stem cells. Antibodies against proteins expressed in various cell types including pancreatic islets, hepatocytes, intestinal cells and lung cells can be used as markers for the endodermal cell lineage to confirm the identities of various differentiated cell cultures and thereby further stem cell research.
Endoderm Stem Cell Markers: GATA4、beta Catenin、Cytokeratin 19、FOXA1