The research study finds that fully differentiated cells are actually better for the purpose of cloning than adult stem cells. They worked with mice in this study, and one of the things to note about it was that they did a lot of within-study replication.
Surprisingly, the granulocytes were the most efficient donor cells for nuclear transfer among the different lineage cells, with 35 to 39 percent becoming a blastocyst, an early embryo consisting of about 100 to 150 cells, compared to 11 percent for the progenitor cells and only 4 percent for the stem cells. Only the granulocytes were able to produce two live cloned pups, although both died within a few hours of birth. As a control, the researchers performed nuclear transfer using embryonic stem cells; 49 percent developed to the blastocyst stage and 18 cloned pups were born.
This doesn’t look like any dramatic advance, but it does raise some questions about the efficiency of some methods that are currently used in cloning studies.