Parkinson’s disease patient-derived induced pluripotent stem cells free of viral reprogramming factors

Induced pluripotent stem cells (iPSCs) derived from somatic cells of patients by viral vector-mediated factor transduction represent a powerful tool for biomedical research and may provide a source for cell replacement therapies. However, the proviruses encoding the reprogramming factors represent a major limitation of the current technology because even low vector expression may alter the differentiation potential of the iPSCs and induce malignant transformation. Here we show that fibroblasts from five patients with idiopathic Parkinson’s disease (PD) can be efficiently reprogrammed into hiPSCs and subsequently differentiated into dopaminergic neurons. Moreover, we derived PD specific hiPSCs free of reprogramming factors using Cre-recombinase excisable viruses. Upon factor deletion these cells maintain a pluripotent state and intact karyotype. Importantly, these factor-free hiPSCs show a global gene expression profile, which is more closely related to hESCs than to hiPSCs carrying the transgenes. Our results indicate that residual transgene expression in conventional virus-carrying hiPSCs can affect their molecular characteristics and that factor-free hiPSCs therefore represent a more suitable source of cells for modeling of human disease.