Overview of stem cell research

Stem cell research is frequently in the news and the HD community is following closely to see if treatments will result. This could happen in several ways. An earlier update reported on the development of a line of stem cells with the Huntington's Disease gene. A new stem cell line for HD These cells are now being used to model the disease and new insights have been gained into targets for treatments. In addition, they are being used in high throughput assays to screen potential treatments.

Stem cells might be used in treating the disease. One possibility is to stimulate the brain's own production of stem cells. Dr. Steven Goldman and colleagues used a viral vector to introduce genes for factors BDNF and noggin into the brains of the R6/2 mice. New neurons were generated, motor performance improved, and survival time increased. (To read more follow these HD Lighthouse links: Goldman 2006  Goldman 2007)

Another possibility is that stem cells could be introduced into the brain with the hope that they would replace dead and dysfunctional cells. Stem cells might serve as a primary treatment or they might be used to restore brain cells lost in Huntington's disease following a treatment or combination of treatments that halt progression. If RNA interference is found to be safe and effective, for example, it might be followed by stem cell treatment for those in the later stages of the disease.

Animal research with stem cells has been promising.  A team of researchers in Korea and Sweden have effectively used induced pluripotent stem cells (iPSCs) derived from an HD patient with a 72 CAG count to treat a neurotoxin rat model of Huntington’s disease.  The treatment reversed symptoms and examination showed that the transplanted precursors appeared to have become GABAergic projection medium spiny neurons, the kind of cells needed.

Types of stem cells

One issue which is not yet clear is which type of stem cell would be most appropriate for treating a neurodegenerative disorder if researchers move forward with clinical trials of donor stem cell lines. Research demonstrating efficacy and safety will be critical and ethical and public policy considerations may have an influence as well.

Stem cells are undifferentiated cells, cells which have not yet developed into the specialized cells of the human body such as the neurons and glia of the brain or blood or skin cells. They can replicate indefinitely.

Embryonic stem cells are harvested from embryos in the earliest stage of development. Researchers use embryos that were created for in vitro fertilization but were not needed. They have the capacity to become any type of human cell.

Somatic stem cells are tissue specific. They are undifferentiated but can only develop into the cells needed in that area of the body. One example is fetal neural stem cells which are harvested from the brains of aborted fetuses. Adult stem cells are harvested from volunteers. For example, adult blood-forming stem cells have been harvested from the bone marrow of volunteers and transplanted to patients for decades.

In recent years, researchers have been able to reprogram adult cells to become stem cells again, essentially turning back the clock. The new induced pluripotent stem cell (iPS) technique involves the use of either certain types of skin cells called fibroblasts or certain types of bone marrow cells. The breakthrough technique involved transfecting the cells with four genes inserted into a viral vector. The four genes reprogram the cells to become stem cells with the potential to become any cell in the body. The technique rendered the cells unsuitable for donation. However, later advances have avoided that problem.

References

MIT, "Stem Cells without Side Effects." Technology Review September 25. 2008.
MIT link

National Institute of Health. "Stem Cell Basics." NIH link