The goal of this CIRM early translational grant is to develop a model for “Parkinson’s disease (PD) in a culture dish” using patient-specific induced pluripotent stem cell lines (iPS). The underlying idea is to utilize these lines as an experimental pre-clinical model to study disease mechanisms unique to PD that could lay the foundation for drug discovery.
Over the last year, we have expanded our patient skin cell bank to 61 cell lines and the iPS cell bank to 51 well-characterized pluripotent stem cell lines from PD patients and healthy controls individuals. We have improved current protocols of neuronal differentiation from patient-derived iPS lines into dopamine producing neurons and can show consistency and reproducibility of making midbrain dopamine expressing nerve cells. This has been now published in Mak et al. 2012. Furthermore, we also develop new protocols to also derive other neuronal subtypes and glia, which are the support cells in the brain, to build co-culture systems. These co-cultures might represent closer the physiological conditions in the brain.
In our first publication (Nguyen et al. 2011), we describe for the first time differences in iPS-derived neurons from a PD patient with a common causative mutation in the LRRK2 gene. These patient cells are more susceptible for cellular toxins leading ultimately to more cell degeneration and cell death. In a second publication Byers et al. 2011, we describe similar findings for a different mutation in the alpha-synuclein gene where the normal protein is overexpressed due to a triplication of the gene locus.
We are also investigating a common disease mechanism implicated in PD, which is mitochondrial dysfunction. In skin cells of a patient we were able to find profound deficits of mitochondrial function compared to control lines and we are now in the process of confirming these results in neural precursors and mature dopamine neurons.
We are expanding the assay development to other disease-related mechanisms such as deficits in outgrowth of neuronal projections and protein aggregation.
Overall, through this program we have developed an invaluable resource of patient-derived cell lines that will be crucial for understanding disease mechanisms and drug discovery. We also showed proof that these cell lines can indeed recapitulates important aspects of disease and are therefore valuable assets as research tools.