20 Years of iPSC Discovery: A Celebration and Vision for the Future

Human iPSC-derived midbrain organoids are emerging as physiologically relevant 3D models to study dopaminergic development, maturation, and dysfunction in Parkinson’s disease (PD) and related synucleinopathies. Disease-relevant phenotypes may arise as gradual changes in excitability, network dynamics, and signal propagation before overt neurodegeneration, requiring electrophysiological workflows that combine throughput, longitudinal stability, and high spatial resolution. Here, in collaboration with STEMCELL Technologies, we established a reproducible, multiscale functional profiling workflow for commercially available human iPSC-derived midbrain organoids using HD-MEAs. Organoids were plated at ~77 days onto MaxTwo HD-MEA 24-Well Plates (26'400 electrodes/well) and monitored for ~1 month. ActivityScan Assay recordings revealed progressive increases in spontaneous firing rate, spike amplitude, and active area, consistent with neuronal maturation and improved tissue-electrode coupling. Network recordings detected synchronized high frequency bursting at early timepoints that became increasingly robust and organized over maturation, with higher burst cadence and greater neuronal recruitment. Pharmacological challenge with 4-AP and TTX produced rapid, reproducible bidirectional modulation of activity, confirming assay responsiveness. Finally, AxonTracking enabled label-free mapping of somato-axon propagation at the organoid-electrode interface, providing subcellular-resolution phenotyping complementary to network-level metrics. Together, these results establish a scalable, non-invasive HD-MEA workflow for longitudinal, multiscale functional phenotyping of human iPSC-derived midbrain organoids, supporting assay development, pharmacological testing, and disease-relevant phenotyping in human 3D iPSC-derived models.

Human iPSC-derived neuronal models provide disease-relevant platforms for studying neurodegenerative disorders such as frontotemporal dementia (FTD), while overcoming key limitations of conventional approaches. Compared with animal models, they better reflect human biology and provide scalable access to relevant cell types in a controlled setting not possible with patient CNS tissue. However, heterogeneous disorders such as FTD require robust human models combined with quantitative, longitudinal readouts across multiple biological scales. Here, in collaboration with FUJIFILM Cellular Dynamics, we describe a longitudinal workflow using high-density microelectrode arrays (HD-MEAs) to profile an iPSC-based FTD model at network, cellular, and subcellular levels. We co-cultured iCell Induced Excitatory Neurons with iCell Astrocytes 2.0 and compared an Apparently Healthy Normal (AHN) control line with an isogenic FTD model carrying a heterozygous GRN loss-of-function mutation (R493X). Using the MaxTwo 24-Well Plate HD-MEA system, with 26,400 electrodes per well, spontaneous activity was monitored from DIV 6–50. MaxLab Live ActivityScan and Network assays revealed hyperexcitability in GRN cultures, with elevated firing rates by DIV 15 (p < 0.01) and altered synchrony, including more frequent, higher-amplitude network bursts, shorter inter-burst intervals from DIV 25, and >2-fold prolonged burst durations by DIV 50 (p <0.001) relative to AHN controls. AxonTracking was used to reconstruct action potential propagation along axonal arbors. Despite increased excitability, GRN neurons showed reduced axonal branching and shorter neurites, indicating a structure–function mismatch in which hyperexcitability may partially compensate for impaired axonal function. These findings establish MaxWell HD-MEA technology as a scalable, sensitive multiscale platform for functional phenotyping of FTD-relevant neuronal dysfunction, for disease modelling and screening.