How is Parkinson’s disease treated now and How could stem cells help?

How is Parkinson’s disease treated now?

Current treatments for Parkinson’s include the drug  It is converted into dopamine in the body, so it acts as a stand-in for the lost dopamine-producing neurons. Some other drugs act like dopamine to stimulate the nerve cells. Patients are also treated with occupational therapy, physiotherapy, healthy diet and exercise. Surgery, such as deep brain stimulation with implanted electrodes, is used to treat advanced symptoms.

These treatments relieve the symptoms of Parkinson's disease, but do not slow down or reverse the damage to nerve cells in the brain. Over time, the symptoms often get worse despite treatment. By the time patients are diagnosed with Parkinson’s they have often had the disease for years and have lost most of the critical nerve cells. Tests that detect Parkinson’s earlier may help, but scientists are searching for a way to replace the damaged cells.

How could stem cells help?

Although the underlying cause of Parkinson's disease is unknown, scientists do know which cells and areas of the brain are involved. Researchers are already using stem cells to grow dopamine-producing nerve cells in the lab so that they can study the disease. Because a single, well-defined type of cell is affected, it may also be possible to treat Parkinson’s by replacing the lost nerve cells with healthy new ones.

Replacing lost cells
Doctors and scientists think cell replacement therapy will work because of the results of transplantation studies done in the 1980s. Scientists took cells from the adrenal glands of four Parkinson’s patients and transplanted them into the patients’ brains. The adrenal glands sit on top of the kidneys and contain some cells that release dopamine and similar substances. After the transplants, there was some improvement in the patients’ condition, but it was only minor and did not last long. This was the first time dopamine-producing tissue had been transplanted into the human brain. In later experiments, researchers have transplanted dopamine-producing neurons from human fetuses into animals and human patients, with major improvements in some cases but only modest changes in others However, there were some side effects in one group of patients and in some cases the disease spread to the transplanted fetal cells more than a decade after surgery.

Scientists still hope that introducing young cells into the brain could delay the onset or progress of Parkinson’s disease, but not enough fetal tissue is available to treat the large numbers of Parkinson’s patients, and the use of foetuses also raises ethical questions. Stem cells could offer an alternative source of new cells for Parkinson’s patients:

·         Embryonic stem (ES) cells could be directed to make dopamine-producing neurons, which could be transplanted into patients. Dopamine-producing neurons have been made from both mouse and human embryonic stem cells in the laboratory.

·         Induced pluripotent stem (iPS) cells could be made from a patient’s adult skin cells in the lab, and then used to make dopamine-producing neurons. In 2010 scientists in the USA treated rats with neurons made from human skin cells using iPS techniques. The transplanted neurons improved symptoms of Parkinson's disease in the rats. However, mice and rats require fewer neurons than humans and it is not yet clear whether this approach would work in patients. More studies are also needed to make sure the cells are safe and would not cause tumours in the brain.

Current research

Stem cell treatments for Parkinson's are still in the early stages of development. Some of the most important recent advances include work on methods for making dopamine-producing neurons in the lab; research on how to improve the effectiveness of transplants and avoid side effects; and studies investigating how the disease works and how cells can help with the development of new drugs.