Study NameReason Number One: Human StudiesReason Number Two: Comparison of Two Rat StudiesNeural Progenitor Cells Can Alleviate Many of the Symptoms Associated withParkinson’s DiseaseA position paper for those who suffer or know somebody who suffers from Parkinson’sdiseaseMax PettijohnSpring 2005A paper for a brochure found in a neural doctor’s clinicParkinson’s Disease (PD) is a neurological disorder that depletes vital, dopamine producing neurons from a portion of the brain called the subsantia nigra (figure 1) (Drucker-Colin, & Verdugo-Diaz, 2003). Dopamine is a chemical that functions as a neurotransmitter that allows smooth, coordinated muscle functions. A neurotransmitter can be thought of as mailman for the nervous system. These chemicals pass messages from nerve to nerve to allow communication. When dopamine levels are heavily reduced(due to PD) the body exhibits rigidity, muscle tremors, inadequate balance, and impaired coordination (Sherwood, 2004). In order to reverse the negative effects of low dopamine levels, scientists are working to find a way to replace the lost dopamine producing neurons. One way to replace these neurons is by transplanting living neuronal (having to do with the brain or nervous system) tissue, called neuronal progenitor cells (NPCs), directly into the substantia nigra. NPCs are cells that are not predisposed to become one specific cell type. Instead, they gain their specificity by mimicking the cells in their surroundings. Research has shown that when an NPC is injected into a portion of the brain, it begins to act like neighboring brain tissues. The basic idea behind NPC 1transplantation for PD is that the NPCs will proliferate (reproduce and grow) and take over the dopamine producing functions of the lost neurons. This, in theory, would alleviate the impaired motor control associated with PD.Figure 1-location of the substantia nigraEvery year approximately 50,000 Americans are diagnosed with PD (Hain, 1999).Roughly 3% of Americans over the age of 65 have PD and experts at the University of Maryland Medical Center estimate that that number will double to 6 % of the total US population in the next 30-40 years (Harvey, 2002). With the incidence of PD on the rise, we must further our research to seek out proper methods to treat this disease. Right now one possible method is using NPCs to regenerate the damaged substantia nigra via the means previously described. The issue at hand is that many studies conducting the effectiveness of NPC transplants on PD have disagreeing conclusions. Due to the relative newness of the NPC transplantation technique, it has yet to be confirmed whether NPCs have beneficial 2results towards those with PD. In order for a final conclusion to be made, many more research projects must be conducted. For now, we can compare and contrast the current studies to get ideas as to where the future of NPCs as a treatment for PD is headed.The issue of NPC transplantation reducing the irregular motor behavior caused byPD is unresolved because of the disagreeing results of several studies. On the one hand, with humans as test subjects, a 1987 study conducted by Mexican neurologist Mardrazo found that NPC tissue grafts into the substantia nigra reduced PD related rigidity substantially (Mardrazo et al. 1987). But in two similar studies conducted just prior to this study, negligible improvements in rigidity and motor behavior were seen (Backlund et al., 1985; Lindvall et al., 1987). The same disagreeing data has been found in studies using rats as models for humans with PD. One study testing the motor behavior of rats after NPC transplantation saw a drastic improvements in the rat’s ability to coordinate motor functions such as walking and running (Wang et al., 2004). While in a similar study, rat motor coordination depleted rapidly, showing that NPC injections were ineffective in delaying/reducing PD symptoms (Kwon et al., 2004). With the conflicting data sets found using both humans and rats as subjects, it becomes obvious that whether NPCs can be used to relieve PD is an unresolved issue (Figure 2).Study Name Population Studied ResultsMardrazo et al. Humans Decrease in overall rigidity3Backlund et al. Humans Negligible motor improvementsLindvall et al. Humans Negligible motor improvementsWang et al. Rats Increase in motor coordinationKwon et al. Rats Decrease in motor coordinationFigure 2- This table shows the contradicting data found in NPC transplantation studies conducted both on humans and on rats.When analyzing the results of recent studies, I am led to believe that NPC transplants can reduce the irregular motor control caused by PD. The field of NPC research is still in its growth phase, but with advances in medical techniques and equipment, it has a very promising future. Given the newness of NPC studies, we have yet to fully explore several variables that may help us find a cure for PD. For example, some studies have found that various origins of NPCs have an effect on test outcomes. We must realize that a deeper exploration of these different variables will lead us closer to a cure for PD. Also, by finding out how to treat PD, we are taking the first steps in learning how to address other neural degenerative disorders such as Huntington’s disease and Schizophrenia (Drucker-Colin, & Verdugo-Diaz, 2003). Though the future of NPC research may look bright, in its present state it is undeveloped. Most of the NPC testing to date has shown only short-term beneficial effects in alleviating spastic motor control. In most studies conducted on humans, the beneficial effects of the transplants appear only in the first or second year of treatment (Drucker-Colin, & Verdugo-Diaz, 2003). The short-lived benefits of NPC transplants canbe traced back to the survival of the NPCs. In some cases the recipient’s body rejects the 4NPC, while in others the NPC is accepted. It is hard to conclude that NPC transplants work because all bodies respond differently to them. There are three reasons why I argue that NPC transplantation is effective in reducing the symptomatic motor behavior associated with PD. First, most of the studies conducted on the effects of NPC transplants on humans after 1987 have proved to alleviate PD symptoms. In the earliest days of NPC transplant testing on humans, most studies found little or no positive reactions from the surgery. Primitive surgical techniques