A Novel Tauopathy 3D-Culture Model on a Biochip Figure 4. Impedimetric quantification of compound efficacy for tau-specific neurodegeneration attenuation and detection of toxic side effects. A. Scheme of impedimetric detection of tau-specific neurodegeneration by using our WT and K280q expressing SH-SY5Y 3D culture model. The induction of tau pathology by OA reduces the physiological impedance level (100% normalization for the untreated tau variants) in a tau mutant manner leading to the pathologic impedance level for WT and K280q tau. Based on this OA induced tau-specific impedance decrease, compounds can be analyzed for their ability to recover induced pathology. For quantitative comparison, all values are normalized to the pathological level of 25 nM OA treated cultures (PL set to 1.0). The Comparison of WT and K280q recovery values allow quantitative distinction of tau-specific effects (recovery level K280q . WT $1), common cellular recovery (recovery level WT $ K280q $1) and potential toxic side effects (recovery level #1). B. Impedimetric analysis of the reference compounds AR-A014418 and hymenialdisine (tau kinase inhibitors), 17-AAG (HSP-90 inhibitor) and methylene blue (aggregation inhibitor). The pathology recovery (x-fold change to the pathology level, PL) of a 24 h and 72 h treatment of spheroids with 25 nM OA and the reference compounds compared in comparison to cultures treated only with 25 nM OA. (n = 20 *p,0.05, **p,0.01, ***p,0.001). doi:10.1371/journal.pone.0049150.g004 Discussion Despite all efforts for development and establishment of especially tauopathy in vivo models [14], there is a high demand for comprehensive in vitro models. These have to fulfill the prerequisites to recapitulate the complex AD-related taupatholo- gical mechanism and the demands for standardization, availability and reproducibility. Especially in the field of API development, these demands could not be sufficiently fulfilled until today. In this context, we established a novel 3D tau pathology culture model. In combination with our sensitive impedance spectroscopy-based label-free monitoring system, it could bridge the gap between insufficient artificial 2D cell culture assays [17,31,33,34] and time- consuming and hardly up scalable in vivo models [14,35]. Using SH-SY5Y cells, we avoid restrictions of primary cells or even stem cell-derived neurons with regard to availability, reproducibility and time. To overcome limitations of monolayer culture based SH-SY5Y neurodegenerative model systems [17,31,36], we established a 3D culture system, in which we could essentially improve the neuronal characteristics of the cells by an extended autonomous differentiation simply replacing the common 2D culture by a 3D cell structure system without the need for any artificial differentiating agents. This is particularly important for the native and unaffected induction of tau pathological processes, since widely used artificial differentiating agents like staurosporine and retinoic acid that are necessary for 2D culture models perturb several pathways involved in AD-like pathology progression [29,37]. Overall, based on their three-dimensional cell organiza- PLOS ONE | www.plosone.org 7 November 2012 | Volume 7 | Issue 11 | e49150