And this is apparently so even when the programming process is free of genetic factors.
"It appears to be a technical issue," says Su-Chun Zhang, professor in the University of Wisconsin-Madison School of Medicine and Public Health. "Technical things can usually be overcome. The key is determining what things are at play that make the induced cells different than embryonic stem cells."
A comparison of the ability of induced cells and embryonic cells to morph into the cells of the brain has found that induced cells are less predictable. There are kinks to be worked out before iPS cells can be used reliably in a stem cell therapy clinical setting,
Zhang's team found that induced cells differentiate into progenitor neural cells and further into the different kinds of functional neurons that make up the brain. However, that they do not faithfully mirror all the differentiation capabilities of embryonic cells suggests that there are unknown factors at play that may limit their use in terms of modeling disease in the laboratory, one of the most important potential early applications of stem cell technology. Such unknowns would also limit their use in clinical settings for such things as cell transplants.
Intriguingly, the new study suggests the presence or absence of the genes used to reprogram skin cells to become the blank slate pluripotent cells make no difference in terms of their capacity to differentiate. Some of the induced stem cell lines tested in the study were made using techniques that bypassed the use of genes that had been used to reprogram skin cells to become pluripotent stem cells.
Zhang explains that originally the thought was that the absence of exotic genetic factors would result in cells essentially identical to embryonic stem cells. "It is totally surprising that doesn't happen at all," Zhang added. "It tells us the techniques for generating induced pluripotent stem cells are still not optimal. There is room for improvement."
Despite their unpredictability, Zhang notes that induced stem cells can still be used to make pure populations of specific types of cells, making them useful for some applications such as testing potential new drugs for efficacy and toxicity. He also noted that the limitations identified by his group are technical issues likely to be resolved relatively quickly.
Adapted from the University of Wisconsin announcement.
Comments