Differentiation of GMP-grade human embryonic stem cells to midbrain dopaminergic neurons for transplantation

Parkinson's disease (PD) is an incurable and progressively degenerative condition. Although the symptoms are well managed at the early stages with medication, there is currently no treatment to halt or reverse the progress of PD. In the late 1980s and 1990s several PD patients received transplants of fetal midbrain tissue containing dopamine-producing neurons. A small fraction of patients showed tremendous benefit from such grafts. A multi-centre European clinical trial led by co-applicant Dr. Roger Barker, TRANSEURO, is underway to re-visit fetal midbrain transplants and systematically address all potential problems faced in the earlier clinical trials. These trials will be small due to the limiting amount of fetal tissue available. There will be a pressing need to resolve the critical issues of scaleable supply and quality of appropriate dopaminergic neurons for any future widespread use in the treatment of PD. Replacing fetal midbrain tissue with dopaminergic neurons differentiated from human embryonic stem cells (hESCs) is the most realistic solution to this cell source problem. Currently 5 different centres in the UK (Edinburgh, London, Manchester, Newcastle, and Sheffield) have established clinical-grade hESC lines, over 15 lines in total. This proposal will examine all UK clinical-grade hESC lines and compare them for their ability to make dopaminergic neurons. We will modify and optimise a novel method to transform hESCs to dopaminergic neurons from our collaborator Dr. Lorenz Studer (Sloan-Kettering, NYC). The best performing hESC line will be used for transplantation into two distinct rat models of PD. Graft survival, behavioural improvements, and absence of tumour formation will all be carefully assessed. The success of this project using hESC-derived dopaminergic neurons in pre-clinical rat models of PD will be a significant step towards the first-in-human clinical trials.

Transplantation of fetal midbrain tissue to treat Parkinson's disease (PD) has demonstrated proof-of-concept that some patients can benefit from such grafts. An international multi-centre Framework 7 European clinical trial, TRANSEURO, is underway to re-visit fetal midbrain transplants and systematically address all protocol and procedural issues with the earlier clinical trials. There is a pressing need to resolve the critical questions of scaleable supply and quality of appropriate Good Manufacturing Practice (GMP) grade dopaminergic cells for any future widespread use in the treatment of PD. Replacing fetal midbrain tissue with midbrain dopaminergic (mDA) neurons differentiated from human embryonic stem cells (hESCs) is the most realistic solution to the cell source problem. We will modify and optimise a novel method to differentiate hESCs to mDA neurons, which relies on a developmental protocol based on floor plate specification. GMP-grade hESCs from multiple sources throughout the UK will be quantitatively assessed for efficiency of mDA differentiation. The best performing hESC line will be used to establish procedures to produce GMP-capable mDA preparations for transplantation. All experiments will be performed with research-grade reagents that have a suitable GMP-grade equivalent available. The mDA neuronal populations will be transplanted into two nude rat models of PD (i) a 6-hydroxydopamine lesion model and (ii) an adeno-associated virus-alpha-synuclein model. Graft survival, behavioural improvements, and absence of tumour formation will be assessed. This collaborative proposal will bring together expertise in pluripotent stem cell differentiation, pre-clinical models of PD, and the UK 's clinical-grade hESCs, with the ultimate aim of moving to first-in-human clinical trials.

Parkinson's disease (PD) is an incurable neurodegenerative disorder that affects 120,000 people in the UK and 6-8 million people world-wide, and this number is expected to increase exponentially with the aging population. The total annual burden of PD in the UK for 2007 was estimated to be £3.3 billion (Findley LJ, 2007), and this economical burden increase substantially with the increase in incidence. This project proposes to establish the foundation to bring a cell-based therapy to the clinic for PD. In the best-case scenario, the impact on the quality of life for sufferers of PD and their carers would be enormous. Although, transplantation of hESC-derived dopaminergic neurons may not provide a true cure due to multiple neural cell types affected in PD, it may provide 15-20 years of drug-free and motor symptom-free relief. Furthermore, combining a transplantation therapy with a disease-modifying drug that prevents alpha-synuclein-mediated neuronal damage may provide a near-complete cure of this condition.
The upfront costs of a transplantation therapy may be large (on par with deep-brain stimulation), but if successful, there will be substantial savings in medication costs and other types of care, including palliative care. The economic savings to the NHS could be very significant indeed.

Findley LJ. The economic impact of Parkinson's disease. (2007) Parkinsonism Relat Disord. 13 Suppl:S8-S12.