The progeny of the human pluripotent stem cells were compared to each other using their gene expression patterns, functionality and appearance. There was essentially little or no difference between them, Lowry said. Then the work began to compare them to equivalent cell types found in humans.
"One important reason to do this is to ensure that the cells we are creating in the Petri dish and potentially using for transplantation are truly analogous to the cells originally found in humans," said Michaela Patterson, first author of the study and a graduate student researcher. "Ideally, they should be a similar as possible."
What the team found was that while the progeny were alike, they bore striking differences from the same cells found in humans when analyzing their gene expression. A significant number of genes, about 100, were differentially expressed in the cell types made from pluripotent stem cells, Lowry said.
About half of those differentially expressed genes are normally thought to be strictly expressed in pluripotent stem cells, which have the potential to differentiate into any cell of the three germ layers. Those genes had not been turned off even after the cell had differentiated into either a neural progenitor cell, hepatocyte or a fibroblast, Patterson said.
"Previously, we assumed that all pluripotency genes get shut off right away, after the fetus begins developing," Patterson said. "We found that this is not the case, and in fact some of these genes remain expressed.
|Contact: Kim Irwin|
University of California - Los Angeles Health Sciences