Human microphysiological model of dorsal root ganglion-spinal cord dorsal horn circuitry recapitulates opioid induced effects.

Microphysiological systems (MPSs) are engineered, in vitro platforms which have been established as viable alternatives to animal models for pre-clinical research with unique advantages over conventional model systems. Many MPSs utilize 3-dimensional (3D) tissue constructs that enable biomimetic cell-cell interactions, allow for extended culture periods, and provide the time necessary for the emergence of physical and physiological characteristics of more mature tissues. Here, we present a novel MPS using human induced pluripotent stem cell (hiPSC)-derived spinal cord dorsal horn (SCDH) spheroids co-cultured with hiPSC-derived dorsal root ganglion (DRG) sensory spheroids in a microengineered hydrogel system to create a "connectoid" model of afferent pain circuitry. SCDH spheroids were functionally innervated by peripheral sensory neurons, and prolonged maturation of hiPSC-derived SCDH neurons within the connectoid system enabled derivation of crucial late-born cell types unattainable using 2D differentiations. Furthermore, hiPSC-derived SCDH spheroids spontaneously generate rhythmic, complex, synaptically-driven electrophysiological waveforms that are disinhibited by morphine exposure, consistent with spinal mechanisms of opioid-induced pruritus and hypersensitivity.