Examination of more than 60 iPSCs lines developed from several types of cells revealed that this gene cluster was silenced in the vast majority of cell lines. While the gene-silenced iPSCs were able to generate many types of mouse tissues, their overall developmental potential was limited. In an assay that produces chimeric animals that incorporate cells from two different stem cells, mice produced from gene-silenced cells had very few tissues that originated from the iPSCs. However, in a few iPSC lines the gene cluster was normally activated, and in the most rigorous developmental assay, those iPSCs were as successful in producing live animals as embryonic stem cells have been. The authors believe this is the first report of animals being produced entirely from adult-derived iPSCs.

"The activation status of this imprinted cluster allowed us to prospectively identify iPSCs that have the full developmental potential of embryonic stem cells," says Matthias Stadtfeld, PhD, of the MGH-CRM and HSCI, a co-lead author of the report. "Identifying pluripotent cells of the highest quality is crucial to the development of therapeutic applications, so we can ensure that any transplanted cells function as well as normal cells. It's going to be important to see whether iPSCs derived from human patients have similar differences in gene expression and if they can be as good as embryonic stem cells - which continue to be the gold standard - in giving rise to the 220 functional cell types in the human body."

Hochedlinger adds, "Previous studies in mice have shown that embryonic stem cells derived from nuclear transfer - the technique used to clone animals - are indistinguishable from stem cells derived from fertilized embryos. Nuclear transfer is another way of reprogramming adult cells into embryonic-like cells, and comparing that approach with iPSC generation may yield important insights into ways of producing the safest and highest quality pluripotent cells for use in patients." Hochedlinger is an associate professor in the Harvard University Department of Stem Cell and Regenerative Medicine.

Source: Massachusetts General Hospital