UCLA researchers have found that embryonic stem cells and skin cells reprogrammed into embryonic-like cells have inherent molecular differences, demonstrating for the first time that the two cell types are clearly distinguishable from one another.The data from the study suggest that embryonic stem cells and the reprogrammed cells, known as induced pluripotent stem (iPS) cells, have overlapping but still distinct gene expression signatures.

"We need to keep in mind that iPS cells are not perfectly similar to embryonic stem cells," said Lowry, an assistant professor of molecular, cell and developmental biology.
"This suggested to us that there could be something biologically relevant causing the distinct differences to arise in multiple labs in different experiments," Lowry said.
"We can't explain this, but it appears something is different about iPS cells and embryonic stem cells," Lowry said.
"It will be important to further examine these cells lines in a careful and systematic manner, as has been done with other stem cell lines, if we are to understand the role they can play in clinical therapies and what effect the observed differences have on these cells," he said.