Alzheimer's disease

Skin cells bypass embryo cell obstacles

UC DAVIS (US) — Stem cells from a patient’s own skin may be effective in treating a variety of health conditions and at the same time would avoid the controversy of using stem cells from human embryos.

Questions about the immunological safety of induced pluripotent stem cells (iPSCs) should not be viewed as a roadblock in advancing research into their use, according to a new study published in the journal Cell Stem Cell.

“iPSCs offer the potential to treat many diseases as an alternative or adjuvant therapy to drugs or surgery,” says Paul Knoepfler, associate professor of cell biology and human anatomy at University of California, Davis.


“Problems that have been identified with their use likely can be overcome, allowing iPSCs to jump from the laboratory dish to patients who could benefit from them.”

iPSCs were first produced in 2006 from mouse cells and in 2007 from human cells and have many of the same regenerative properties as human embryonic stem cells, but are derived in a lab from adult cells, such as skin cells, by inducing or forcing them to express specific genes that are normally dormant.

In theory, a person’s skin cells could be induced to make neurons that produce the neurotransmitter dopamine, for example, and be delivered to brain regions where it is lacking in patients with Parkinson’s disease. Similarly, cells could be induced to regenerate heart muscle and blood vessels after a heart attack, or neurons following a spinal cord injury.

Problems of rejection due to immunological differences between the donor (the embryo) and the patient would be eliminated, because the iPSCs would be derived from each individual patient.

A recent study using iPSCs in mice found that tissue rejection may, in fact, occur in some cases, but Knoepfler believes that particular study was conducted in the context of tumors, which tend to be highly immunogenic and not be applicable for human use.

Another concern with using either iPSCs or embryonic stem cells is that cells with the ability to turn into many different cell types may grow out of control, producing cancerous tumors. Those studies involved implanting large numbers of undifferentiated stem cells into mice that were treated with immunosuppressant drugs to reject transplants, making the conditions ideal for cancers to arise, Knoepfler says.

That scenario is unlikely to be applicable when treating humans for actual diseases. In such cases, the stem cells would be induced to have a specific function, and the body’s natural immune defenses would be present.

The “pluripotent” nature of stem cells, which potentially allow their use to repair almost any tissue, is only beginning to be harnessed for human therapies. Stem cell therapy has already been successfully used for years to treat leukemia and related bone and blood cancers and the use of iPSCs could vastly increase the spectrum of disease that might be treated with stem cells, without the safety and ethical concerns inherent in using embryonic stem cells, Knoepfler says.

“Future studies of iPSCs should increasingly focus on issues most relevant to the eventual clinical use of the cells, offering the fastest pathway to treating patients with this potentially powerful therapeutic tool.”

Funding was provided by a grant from the California Institute for Regenerative Medicine.

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