A functional endocannabinoid system in human induced pluripotent stem cell-derived cortical cultures

Abstract

The endocannabinoid system is an increasingly popular therapeutic target in many neurological conditions, due in large part to its ability to protect neurons from damage caused by hyperactivity and excitotoxicity. Despite recent interest in cannabinoid-based treatments, the unavailability of human brain tissue and species differences between humans and animal models present obstacles to drug development. Human induced pluripotent-derived stem cells (hiPSCs), which can be obtained less invasively from skin samples and then reprogrammed into neurons and glia, are one possible solution to this problem. However, it is not clear whether hiPSC-derived neurons actually have a working endocannabinoid system to study. In this thesis I characterize the endocannabinoid system in a commercially available line of hiPSC-derived cortical neuron/astrocyte cultures using calcium imaging and a fluorescent cannabinoid indicator expressed in live neurons. hiPSC-derived cultures produced and metabolized endocannabinoids in addition to responding to exogenously applied cannabinoids, indicating that they do indeed possess a fully functional endocannabinoid system. I also show that endocannabinoid synthesis evoked by a muscarinic receptor agonist in hiPSC-derived cortical cultures is not calcium-dependent, and that an inhibitor of endocannabinoid metabolism produces less receptor desensitization than a cannabinoid receptor agonist with prolonged exposure. These studies demonstrate that hiPSC-derived neuron/astrocyte cultures are a powerful new tool for investigating open questions about the regulation of the human endocannabinoid system.