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Induced pluripotent stem cells can be created from adult donor blood: What are the implications?
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Pluripotent stem cells have many advantages
The ability to produce pluripotent stem cells from adult stem cells overcomes some of the moral and ethical issues associated with harvesting cells from pre-implantation embryos. Being able to make patient-specific cells may overcome some of the problems associated with transplantation of foreign cells into patients. We only have a few approved human embryonic stem cells lines, and it’s difficult to make cell lines that are compatible for most people, so being able to do that on an individual basis may overcome some of those transplantation issues.
I think most people in the field would say that we need to continue studying both embryonic and induced pluripotent stem cells. Embryonic stem cells are considered the gold standard. The so-called induced pluripotent stem cells were first described by Dr. Shinya Yamanaka at Kyoto University, and so far they look good, but we’re in the early days of the field. What’s likely to happen is that, as with adult stem cells, some cell types might be good for treating one disease where as another cell type is appropriate for another disease.
Theoretically at least, induced pluripotent stem cells can avoid the problem of rejection. Because they are derived from the patient, potentially they wouldn’t be rejected in the way embryonic stem cell-derived cells might be rejected.
We can’t say definitively that embryonic stem cell-derived cells will be rejected because embryonic stem cells might not express the same histocompatibility antigens that trigger rejection the way some other cells do. Nevertheless, the big advantage pluripotent stem cells might have over embryonic stem cells is that because they could be derived from a patient they might not be rejected by the patient.
We might see a day when induced pluripotent stem cells replace embryonic stem cells. It will depend on the results of a lot of studies from a lot of different laboratories showing that adult-derived pluripotent stem cells are as good as those derived from embryos. I’m not sure that embryonic stem cells are necessarily better than induced pluripotent stem cells, but we know a lot more about them because we’ve been studying them in labs for a longer period of time. Only time will tell, but we shouldn’t abandon work on human embryonic stem cells because of induced pluripotent stem cells. We need to know more before we make that decision.
Peter J. Donovan, PhD, is Co-director of the Sue and Bill Gross Stem Cell Research Center and a Professor of Biological Chemistry and Developmental and Cell Biology at the University of California at Irvine.
Pluripotent stem cells are not the same as embryonic
The ability to make human pluripotent stem cells from somatic blood cells widens the repertoire of therapeutic possibilities. It’s particularly useful if we can have a patient just give a blood sample, which is practically easier to acquire, as opposed to skin or liver or brain samples, which are harder to get. Those require biopsies, the actual cutting and processing of tissue. In theory, the idea of just getting a sample of blood from a patient at a doctor’s office, then taking that sample and turning it into a stem cell that can make any part of the body is very appealing. It’s a great addition to the story of induced pluripotent stem cells.
The induced pluripotent stem cells (iPSC) are where the money is. Yamanaka first reported iPSC in 2006. Since then, many labs have reproduced the concept of taking a cell from any part of the body and turning it into a stem cell with genetically-defined embryonic factors. This is an amazing thing because it obviates the need to get these cells from the fertility clinic, which is really the issue of contention from many folks. Thus, the ability to make iPSC directly from a piece of tissue from a patient completely bypasses the derivation of human embryonic stem cells from fertility clinics. There is no real embryo involved in making iPSC; it’s a completely artificial process. It’s almost like magic.
Furthermore, these defined embryonic factors have much to teach us about human biology. The embryonic factors seem to control “rebooting the computer,” so to speak, of an adult cell in our body. For example, they can convert a skin cell back into a state similar to when we were embryonic stem cells of approximately 5 days old. You can take, then grow these cells and turn them into whatever you might need for tissue transplantation. The beauty of it is that it’s completely genetically identical to the person it came from.
Here’s the bad news. Pluripotent stem cells don’t behave exactly like the real thing. We don’t know if they can make cells exactly the same as the original. They are as of yet untested in their full potential, and some people worry they may be similar to a Xerox copy. Worse, the way these genetic factors were originally introduced into a skin cell — or a blood cell — can result in a propensity for them to eventually become cancerous. The factors are introduced using a virus, and the viruses can form malignant tumors that real stem cells do not.
People working in this field, including my lab and others, think this is but a technical caveat. We’re finding more efficient and safer ways to do this transformation without it being dangerous and with it being more faithful to the real thing. The bottom line is that until we can get these iPSC cells to work properly, we still need access to the real embryonic stem cells. They are the “control” for the experiment.
Elias T. Zambidis, MD, PhD, is an Assistant Professor of Pediatrics and Oncology with the Sidney Kimmel Comprehensive Cancer Center at the Johns Hopkins University School of Medicine in Baltimore.