Post-Bac Student Gladstone Institutes SAN FRANCISCO, California, United States
Abstract: Spinal interneurons (SpINs) are being increasingly recognized for their neuroplastic potential after spinal cord injury (SCI). Transplantation of SpIN progenitors after SCI has demonstrated their ability to spontaneously survive and integrate with injured networks, contributing to improved functional outcome. The extent of this connectivity, however, can be variable, and there is a need for strategies capable of enhancing connectivity. Building off principles of “Hebbian” plasticity, we hypothesize that neural stimulation can be used to drive synaptic integration and connectivity. Here we used an optogenetic human induced pluripotent stem cell (hiPSC) line to differentiate into SpINs and measured the effects of light and electrical stimulation on neurotrophin production, neurite outgrowth and synaptic connectivity. Over a four week period, blue light stimulation (2ms pulses, 20Hz, every 4 days) resulted in an increase in brain-derived neurotrophin production as well as neurite outgrowth, compared to unstimulated and wildtype controls. Optogenetic stimulation of SpINs also resulted in increased overall neural activity and network synchronicity, as measured by multielectrode arrays (MEA). Electrical stimulation (500mV, 5 times, every 180s) over a four-week period revealed enhanced neuronal activity when compared to unstimulated controls (700% increase in activity in stimulated versus unstimulated 240% increase), and network activity increased by 1400% in stimulated compared to unstimulated controls. Patch clamp experiments revealed that light stimulation not only depolarized and evoked firing potentials in these SpINs, but also accelerated the emergence of rebound bursting and network activity when compared to unstimulated SpINs. Future work will focus on unbiasedly characterizing the molecular changes that result from neural stimulation using single cell RNA sequencing and functional in vitro and in vivo assays.
