A major barrier to research on Parkinson's disease is inaccessibility of diseased tissue for study. One solution is to derive induced pluripotent stem cells from patients and differentiate them into neurons affected by disease. Triplication of SNCA, encoding α-synuclein, causes a fully penetrant, aggressive form of Parkinson's disease with dementia. α-Synuclein dysfunction is the critical pathogenic event in Parkinson's disease, multiple system atrophy and dementia with Lewy bodies. Here we produce multiple induced pluripotent stem cell lines from an SNCA triplication patient and an unaffected first-degree relative. When these cells are differentiated into midbrain dopaminergic neurons, those from the patient produce double the amount of α-synuclein protein as neurons from the unaffected relative, precisely recapitulating the cause of Parkinson's disease in these individuals. This model represents a new experimental system to identify compounds that reduce levels of α-synuclein, and to investigate the mechanistic basis of neurodegeneration caused by α-synuclein dysfunction.

Real-time monitoring of stem cells (SCs) differentiation will be critical to scale-up SC technologies, while label-free techniques will be desirable to quality-control SCs without precluding their therapeutic potential. We cultured adipose-derived stem cells (ADSCs) on top of multielectrode arrays and measured variations in the complex impedance Z* throughout induction of ADSCs toward osteoblasts and adipocytes. Z* was measured up to 17 d, every 180 s, over a 62.5-64kHz frequency range with an ECIS Zθ instrument. We found that osteogenesis and adipogenesis were characterized by distinct Z* time-courses. Significant differences were found (P = 0.007) as soon as 12 h post induction. An increase in the barrier resistance (Rb) up to 1.7 ohm·cm 2 was associated with early osteo-induction, whereas Rb peaked at 0.63 ohm·cm 2 for adipo-induced cells before falling to zero at t = 129 h. Dissimilarities in Z* throughout early induction (<24 h) were essentially attributed to variations in the cell-substrate parameter α. Four days after induction, cell membrane capacitance (Cm) of osteoinduced cells (Cm = 1.72 ± 0.10 μF/cm 2 ) was significantly different from that of adipo-induced cells (Cm = 2.25 ± 0.27 μF/cm 2 ), indicating that Cm could be used as an early marker of differentiation. Finally, we demonstrated long-term monitoring and measured a shift in the complex plane in the middle frequency range (1 kHz to 8 kHz) between early (t = 100 h) and late induction (t = 380 h). This study demonstrated that the osteoblast and adipocyte lineages have distinct dielectric properties and that such differences can be used to perform real-time label-free quantitative monitoring of adult stem cell differentiation with impedance sensing.noninvasive quantitative monitoring | bioimpedance S everal sources of stem cells are exploited and investigated for regenerative medicine, either to conduct in situ cell therapy or to facilitate drug discovery with in vitro stem cellbased disease models.Among them, adipose-derived stem cells (ADSCs) are adult stem cells isolated at high concentration from lipoaspirates (1, 2). They are a realistic autologous source for orthopedic and reconstructive surgery applications (3) and to develop patientspecific in vitro models for drug screening.A variety of biochemical assays are available to characterize stem cells at the molecular level. These assays have vastly contributed to improve our understanding of basic cell biology down to gene and protein expression. Paradoxically, most of these techniques are not able to characterize cells without precluding their therapeutic potential. Label-free noninvasive monitoring techniques are desirable to translate successfully basic stem cell technology to therapeutic applications. Without being able to fix, stain, lyse, or fluorescent-label the cells, few techniques remain available.Electric cell-substrate impedance sensing (ECIS) pioneered by Giaever and Keese (4-7) is a well established technique originally developed to assess barrier formation and cell motility (8-1...