Stem Cells and the Brain
January 22, 2008
Stem cells are probably one of the least understood (by the public), yet most fascinating, biological entities we have identified. Who of us hasn’t marveled at the ability of a newt to grow back its limbs after they are cut off, or of a starfish to be cut in half and regenerate to form two new starfish? Both organisms are able to do these seemingly miraculous things because of stem cells. So you can understand why some scientists are consumed with understanding and utilizing stem cells, in the hopes of slowing disease and even aging. Stem cells are special because they are versatile cells that can be prodded to develop into any type of adult cell, be it muscle, liver, nerve, etc. This makes them valuable not only for possible cell replacement therapies (for degenerative diseases like Parkinson’s), but also for the study of cell growth to learn more about the etiology of disease. If you are unfamiliar with stem cells and have a few hours to learn about them, there is a fantastic series of lectures available for free on the Howard Hughes Medical Institute’s interactive site, http://www.hhmi.org/biointeractive/lectures/.
Manipulating stem cells, however, is not easy and involves several dilemmas. A major one is: once you have one of these versatile cells, how do you get it to become what you want it to be? This is an area of continuing research, and in most cases involves finding a gene or set of genes responsible for directing the stem cell’s growth. This, once again, is not an easy task, as there are somewhere around 30,000 genes in a human cell (estimates vary).
Occasionally, however, there are successes. Dr. Edwin Monuki and colleagues at the University of California, Irvine, have identified a gene called Lhx2 that directs stem cells in early development to form the cerebral cortex. The cortex is responsible for higher-order functions in humans, such as reasoning, language, and vision. Degradation of or damage to the cortex can be very debilitating, as is seen in cases of Alzheimer’s disease or stroke. Thus, the discovery of a mechanism to turn stem cells into cortical cells has great potential to slow neurodegenerative disease or help patients recover from cerebrovascular accidents. Despite the political controversies, stem cells are one of the most promising tools we have for fighting disease and aging, although much more must be learned about them before they can fulfill our expectations. Discoveries like Dr. Monuki’s are edifying steps toward that goal.