Parkinson?s Disease (PD) is a degenerative disorder of the central nervous system, where a loss of dopaminergic cells occurs in a region called the substantia nigra. There are no current cures for the disease. The most widely prescribed therapy is levodopa, or L-Dopa. L-Dopa, given over an extended period of time has diminished clinical benefit and can result in serious side effects, such as abnormal involuntary movements (AIMs). Cell based delivery of dopa and/or dopamine has recently been evaluated as an alternative therapy. Unfortunately, some side effects have been reported. Some patients developed AIMs that may be related to the uncontrolled release of dopamine from the transplants. The ability to control the amount of dopamine produced by transplanted cells would be an effective way to try and eliminate AIMs. We are currently engineering cells to express tyrosine hydroxylase and/or dopa decarboxylase using a regulatable genetic construct. Using the tetracycline-off system we have engineered neuronal, astroglial, and oligodendrocytic cell lines. HPLC analysis has shown that dopa is produced in several cell lines engineered with TH. Additional engineering with DDC is expected to produce dopaminergic cells. Our goal is to identify a cell line that has high dopa and/or dopamine production and tight regulation and to transplant these cells into a rat model of PD plus established AIMs. The control of AIMs by controlled expression of the therapeutic molecule can then be investigated.