A comparative study of the phenotype with kainic acid-induced seizure in DBA/2 mice from three different sources

High-Throughput Screening Assay for Detecting Drug-Induced Changes in Synchronized Neuronal Oscillations and Potential Seizure Risk Based on Ca2+ Fluorescence Measurements in Human Induced Pluripotent Stem Cell (hiPSC)-Derived Neuronal 2D and 3D Cultures

Drug-induced seizure liability is a significant safety issue and the basis for attrition in drug development. Occurrence in late development results in increased costs, human risk, and delayed market availability of novel therapeutics. Therefore, there is an urgent need for biologically relevant, in vitro high-throughput screening assays (HTS) to predict potential risks for drug-induced seizure early in drug discovery. We investigated drug-induced changes in neural Ca²⁺ oscillations, using fluorescent dyes as a potential indicator of seizure risk, in hiPSC-derived neurons co-cultured with human primary astrocytes in both 2D and 3D forms. The dynamics of synchronized neuronal calcium oscillations were measured with an FDSS kinetics reader. Drug responses in synchronized Ca²⁺ oscillations were recorded in both 2D and 3D hiPSC-derived neuron/primary astrocyte co-cultures using positive controls (4-aminopyridine and kainic acid) and negative control (acetaminophen). Subsequently, blinded tests were carried out for 25 drugs with known clinical seizure incidence. Positive predictive value (accuracy) based on significant changes in the peak number of Ca²⁺ oscillations among 25 reference drugs was 91% in 2D vs. 45% in 3D hiPSC-neuron/primary astrocyte co-cultures. These data suggest that drugs that alter neuronal activity and may have potential risk for seizures can be identified with high accuracy using an HTS approach using the measurements of Ca²⁺ oscillations in hiPSC-derived neurons co-cultured with primary astrocytes in 2D.

Non-invasive In Vivo Brain Astrogenesis and Astrogliosis Quantification Using a Far-red E2-Crimson Transgenic Reporter Mouse

Despite the adaptation of major clinical imaging modalities for small animals, optical bioluminescence imaging technology is the main approach readily reporting gene activity. Yet, in vivo bioluminescence monitoring requires the administration and diffusion of a substrate to the tissues of interest, resulting in experimental variability, high reagent cost, long acquisition time, and stress to the animal. In our study, we avoid such issues upon generating a new transgenic mouse (GFAP-E2crimson) expressing the far-red fluorescent protein E2-crimson under the control of the glial fibrillary acidic protein (GFAP) promoter. Using microscopy, we validated the selective expression of the reporter in the astrocyte cell population and by non-invasive in vivo fluorescence imaging its detection through the scalps and skulls of live animals. In addition, we performed a longitudinal study validating by in vivo imaging that the E2-crimson fluorescence signal is up-regulated, in pups during astrogenesis and in adult mice during astrogliosis upon kainic acid administration. Furthermore, upon crossing GFAP-E2crimson transgenic with 5XFAD Alzheimer's disease mice model, we were able to quantify the chronic inflammation triggered by amyloid deposit and aging over 18 months. As many diseases and conditions can trigger neuroinflammation, we believe that the GFAP-E2crimson reporter mice model delivers tremendous value for the non-invasive quantification of astrogliosis responses in living animals.