High content screening miniaturization and single cell imaging of mature human feeder layer-free iPSC-derived neurons.

Human induced pluripotent stem cell (iPSC)-derived neurons are being increasingly used for high content imaging and screening. However, iPSC-derived neuronal differentiation and maturation is time-intensive, often requiring >8 weeks. Unfortunately, the differentiating and maturing iPSC-derived neuronal cultures also tend to migrate and coalesce into ganglion-like clusters making single-cell analysis challenging, especially in miniaturized formats. Using our defined extracellular matrix and low oxygen culturing conditions for the differentiation and maturation of human cortical neurons, we further modified neuronal progenitor cell seeding densities and feeder layer-free culturing conditions in miniaturized formats (i.e., 96 well) to decrease neuronal clustering, enhance single-cell identification and reduce edge effects usually observed after extended neuronal cell culture. Subsequent algorithm development refined capabilities to distinguish and identify single mature neurons, as identified by NeuN expression, from large cellular aggregates, which were excluded from image analysis. Incorporation of astrocyte conditioned medium during differentiation and maturation periods significantly increased the percentage (i.e., ∼10% to ∼30%) of mature neurons (i.e., NeuN+) detected at 4-weeks post-differentiation. Pilot, proof of concept studies using this optimized assay system yielded negligible edge effects and robust Z-factors in population-based as well as image-based neurotoxicity assay formats. Moreover, moxidectin, an FDA-approved drug with documented neurotoxic adverse effects, was identified as a hit using both screening formats. This miniaturized, feeder layer-free format and image analysis algorithm provides a foundational imaging and screening platform, which enables quantitative single-cell analysis of differentiated human neurons.