Abstract
Cell transplantation therapy provides a regenerative strategy for neural repair. We tested the hypothesis that selective excitation of transplanted induced pluripotent stem cell-derived neural progenitor cells (iPS-NPCs) could recapitulate an activity-enriched microenvironment that confers regenerative benefits for the treatment of stroke. Mouse iPS-NPCs were transduced with a novel optochemogenetics fusion protein, luminopsin 3 (LMO3), which consisted of a bioluminescent luciferase, Gaussia luciferase, and an opsin, Volvox Channelrhodopsin 1. These LMO3-iPS-NPCs can be activated by either photostimulation using light or by the luciferase substrate coelenterazine (CTZ). In vitro stimulations of LMO3-iPS-NPCs increased expression of synapsin-1, postsynaptic density 95, brain derived neurotrophic factor (BDNF), and stromal cell-derived factor 1 and promoted neurite outgrowth. After transplantation into the ischemic cortex of mice, LMO3-iPS-NPCs differentiated into mature neurons. Synapse formation between implanted and host neurons was identified using immunogold electron microscopy and patch-clamp recordings. Stimulation of transplanted cells with daily intranasal administration of CTZ enhanced axonal myelination, synaptic transmission, improved thalamocortical connectivity, and functional recovery. Patch-clamp and multielectrode array recordings in brain slices showed that CTZ or light stimulation facilitated synaptic transmission and induced neuroplasticity mimicking the LTP of EPSPs. Stroke mice received the combined LMO3-iPS-NPC/CTZ treatment, but not cell or CTZ alone, showed enhanced neural network connections in the peri-infarct region, promoted optimal functional recoveries after stroke in male and female, young and aged mice. Thus, excitation of transplanted cells via the noninvasive optochemogenetics treatment provides a novel integrative cell therapy with comprehensive regenerative benefits after stroke.
SIGNIFICANCE STATEMENT Neural network reconnection is critical for repairing damaged brain. Strategies that promote this repair are expected to improve functional outcomes. This study pioneers the generation and application of an optochemogenetics approach in stem cell transplantation therapy after stroke for optimal neural repair and functional recovery. Using induced pluripotent stem cell-derived neural progenitor cells (iPS-NPCs) expressing the novel optochemogenetic probe luminopsin (LMO3), and intranasally delivered luciferase substrate coelenterazine, we show enhanced regenerative properties of LMO3-iPS-NPCs in vitro and after transplantation into the ischemic brain of different genders and ages. The noninvasive repeated coelenterazine stimulation of transplanted cells is feasible for clinical applications. The synergetic effects of the combinatorial cell therapy may have significant impacts on regenerative approach for treatments of CNS injuries.
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