Sunday, November 13, 2011

Stuttering and Gene Therapies

Stem cell therapies are generally oriented toward the remediation of some chemical deficiency in a living organism.  For example, Parkinson’s victims are deficient with regard to the production of dopamine and Type 1 diabetics lack a capability for producing insulin.

The hope of stem cell therapy is that stem cells can be used to make cells producing the vital chemical that is lacking.  These cells can then be injected into the relevant organs and, as they took hold, the symptoms of the disease would disappear (hopefully permanently). 

 A recent study in the journal Nature (November 6, 2011), describes research in which stem cells derived from human embryos were used to treat Parkinson’s disease in rodents.  Previous approaches had failed because human derived dopamine cells did not perform efficiently when transplanted into animals; in addition, the transplantations triggered the growth of unwanted tumor-like structures.

In these past experiments, two specialized proteins, known as growth factors, were added to turn embryonic stem cells into dopamine-producing nerve cells.  But the recent  Nature study added a third substance that activated a crucial biological pathway in the embryonic cells, leading to human dopamine cells that functioned more effectively and that did not lead to tumor-like structures. 

What does this study have to do with stuttering?  In many cases, stuttering is a result of excessive dopaminergic activity in parts of the brain dealing with speech and its timing rather than some neurochemical deficiency.  So, at first glance, it may appear that stem cell therapies might not be relevant.

However, an insufficiency of GABAergic activity in these areas of the brain may be a contributing factor leading to the dopaminergic overactivity (see the blog post entitled “Stuttering and Neurotransmitters,“ August 25, 2010).  So if stem cells could be coaxed into generating GABA-producing cells, then, in principal a gene therapy approach to stuttering might be feasible.

The problems with gene therapies applied to stuttering are that there are essentially no animal models with which to test these therapies (perhaps the “stuttering mice?”) and that such intrusive treatments may not be deemed warranted for a “mild” malady such as stuttering.  At any rate, we should expect a relatively long time horizon before any such treatments become available.  And when they do, we might expect them to be a byproduct of therapies for the treatment of conditions such as schizophrenia.  

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