Inclusion Criteria:  Provision of signed and dated informed consent form Aged 45 to 70 years old (inclusive) at Screening Idiopathic Parkinson's disease patients who meet the diagnostic criteria of the "Movement Disorder Society Clinical Diagnostic Criteria for Parkinson's disease" With at least 5 years since the diagnosis of Parkinson's disease With responsiveness to levodopa or dopa agonist. This is defined as improvement between ''Off'' and ''On'' MDS-UPDRS by at least 33% of the Motor MDS-UPDRS Idiopathic Parkinson's disease of Stage 3 ~ 4 of modified Hoehn & Yahr staging during ''ON'' time Stable Parkinsonian medications for at least 2 months prior to the Screening Visit MRI not showing gross atrophy or any brain pathology other than PD Mini-Mental State Examination (MMSE) ≧ 24 With score of the Beck Depression Inventory (BDI-II) < 29 and Hamilton Rating Scale for Depression (HAM-D-17) < 25  Exclusion Criteria:  Atypical or secondary Parkinsonism With neurodegenerative disorders other than PD Unable to receive MRI or PET scanning With any concomitant disorder that would contraindicate coagulation, general anesthesia, or stereotactic neurosurgery Received any other investigational agent within 4 weeks prior to Screening History of intracranial surgeries or implantation of a device for Parkinson's disease 2 years prior to Screening Major surgery within the previous 6 months at Screening  Significant cardiovascular disease, including:  New York Heart Association (NYHA) class III or IV congestive heart failure Uncontrolled hypertension: Blood pressure >140/90 mmHg History of serious ventricular arrhythmia Malignancy within 2 years prior to Screening Any diagnosis of autoimmune disease or immune compromised state and requiring systemic steroid or immunosuppressive treatment Any other severe systemic disorder, including history of schizophrenia or other psychotic disorders, stroke, seizure, traumatic brain injury, or central nervous system infection, which judged by the investigator that entering the trial may be detrimental to the subject Psychiatric, addictive or any other disorder that compromises ability to give a truly informed consent and perform all study assessments  Positive in any of the following regulatory authority-licensed screening tests:  HIV antigen/antibody combo test Anti-HCV test Hepatitis B surface antigen (HBsAg) test Rapid plasma reagin (RPR) test HIV-1 nucleic acid test (NAT) HBV NAT HCV NAT  Any of the following hematologic abnormalities:  Hemoglobin < 9.0 g/dL, ANC < 1,500/μL Platelets < 100,000/μL  Any of the following serum biochemistry abnormalities:  Total bilirubin > 1.5 × ULN AST or ALT > 2.5 × ULN r-GT > 2.5 × ULN ALP > 2.5 × ULN serum albumin < 3.0 g/dL creatinine > 1.5 × ULN Female subject who is lactating or has positive serum or urine pregnancy test at Screening Visit  Female subject with childbearing potential or male subject with female spouse/partner with childbearing potential who refuses to adopt at least two forms of birth control (at least one of which must be a barrier method) from Screening until Final/Early Termination Visit. Acceptable forms include:  Established use of oral, injected or implanted hormonal methods of contraception Placement of an intrauterine device (IUD) or intrauterine system (IUS) Barrier methods of contraception: condom, or occlusive cap (diaphragm or cervical/vault caps) With any condition judged by the investigator that entering the trial may be detrimental to the subject