Two Diseases, One Hope: Fetal Neural Transplantation in the Treatment of Parkinson's and Huntington's Disease
Parkinson's Disease (PD) and Huntington's Disease (HD) are neurodegenerative diseases that are caused by malfunctions within the motor sector of the nervous system. These malfunctions, which are caused either by the surplus (as in HD) or absence (as in PD) of hormones, are a direct result of neural cell deterioration within the brain. PD and HD illustrate two very different behavioral patterns that are subsequently caused by two opposite and extreme biological abnormalities. Yet the common thread between the two conditions is that there are major mechanical predicaments arising between cellular connections within the brain. Thus, it is the occurrence of cell death that functions as a key link between these two very different diseases. And it is because of this commonality, that the most controversial experimental treatment for PD and HD, fetal transplant surgery, functions as a possible cure for both these diseases. (18). The cause of neurodegenerative diseases, like PD and HD, is basically a story of how abnormal chemical interactions result in motor problems. Generally speaking, the brain is the body's communication headquarters. It obtains a myriad of information from various parts of the sensory system and processes this information in an organized fashion. It then relays sensory input to different parts of the motor system. Such messages from the brain dictate specific muscular and behavioral patterns. (18).
Moreover, there are two particular areas of the brain that are specifically related to motor malfunctions: the substania nigra and the striatum (the caudate nucleus and the putamen). The cells of the nigra synapse with cells of the striatum, which serves as the controller of motor functions such as walking, balance, and muscular movement. Information from the nigra cells passes through the synapses with the aid of a specific hormone, dopamine, which is a significant chemical transmitter in the brain. Because the existence of dopamine is essential to the function of the substania nigra, it is also essential for the various muscular activities controlled by the striatum, such as walking, balance, etc. (16).
In Parkinson's Disease and Huntington's disease the nigra-striatum neural communication assemblage is severely hampered. PD results from a depletion in the amount of dopamine produced by the brain. At the onset of the disease, dopamine-secreting cells of the substania nigra, either because of genetic factors or environmental toxins, experience mass cell death. Thus, the nigra cells are unable to form synapses through which they secrete and relay dopamine to the striatum in a neural circuit within the basal ganglia (18).
HD, in contrast, is not a condition offset by the environment, as PD is thought to be. It is indeed a condition due to cell death in the brain (basal ganglia) but is caused by an abnormal gene...