Therapies based on stem cells rely heavily on our ability to coax these blank-cellular-slates into taking on specific forms. Stem cells are exciting as possible sources of medicinal therapy because they have the potential to become any type of cell in the body, but in order for their utility to be realized, we must be able to reliably effect their fates. The process of turning a stem cell into a specific cell type is called, logically, differentiation. With the exception of the immune system, the brain has more cell-types than any other organ, not to mention some of the most differentiated (exotic or distinct) types. Thus, many scientists are busily engaged in the activity of deducing molecular algorithms for deterministic control of their cellular end-state.
One disease where there seems to be a clear connection between cell-type-specific disfunction and pathology is Parkinson’s Disease. In this debilitating condition, the afflicted progressively loose motor function due to a lack of stimulation of their motor corticies (the area responsible for directing movement in the human brain) by dopaminergic neurons found in the amygdala (another brain region associated with emotion and reward). Further, it appears to be the case that the reason for this lack of stimulation is simply a lack of production of dopamine by these dopaminergic amygdalar neurons. The cell-type specificity of the disease makes it an an excellent candidate for treatment by replacing the existing hypoactive neurons with newly differentiated stem cell versions of their kind, which should have normal dopamine production abilities.
A recent paper appearing in the journal Brain reports the results of a study in which the researchers have achieved just such a therapeutic cell-type replacement in rats with a “model” of human Parkinson’s disease (ref. 1). They report that motor function was restored by this approach, and further that the longevity of the differentiated cells was related to their restorative efficacy. Further examples of work like this promise to revolutionize the treatment of a host of diseases.
1. Sanchez-Pernaute R, Lee H, Patterson M, Reske-Nielsen C, Yoshizaki T, Sonntag KC, Studer L, Isacson O. (2008) Parthenogenetic dopamine neurons from primate embryonic stem cells restore function in experimental Parkinson’s disease. Brain.