Calcium imaging of synaptic connectivity between host and neural progenitor cell graft-derived neurons after spinal cord injury

Authors:
STEVEN L. CETO, K. SEKIGUCHI, A. NIMMERJAHN, M. H. TUSZYNSKI;

Steven Ceto,
Predoctoral Graduate Student

Lab Abstract:
Neural stem cells (NSCs) grafted into sites of spinal cord injury (SCI) may act as new electrophysiological relays between host neurons above and below the lesion. Host axons regenerate robustly into NSC grafts and form synapses; in turn, graft axons extend long distances into host white and gray matter caudal to the injury and form synapses. To investigate potential functionality of these new synaptic pathways, we performed calcium imaging and whole-cell patch clamp recordings in mice with NSC grafts after SCI. We placed T12 dorsal column lesions and acutely grafted embryonic day twelve (E12)-derived spinal cord neural progenitor cells (NPCs) expressing the calcium indicator GCaMP6f into the lesion site. From 6 to 8 weeks later, we imaged the activity of populations of neurons within NPC grafts in acute spinal cord slices, anesthetized, or awake behaving animals. After grafting NPCs into acute spinal cord injuries in mice, we imaged the simultaneous activity of populations of neurons within grafts both in vivo and in ex vivo slice preparations. We observed spontaneous activity in both neurons and glia, as well as hindpaw pinch- and cold air puff-evoked responses. Furthermore, optogenetic stimulation of corticospinal tract axons regenerating into grafts evoked robust responses throughout grafts. Activity patterns included large-scale events and independent, single-neuron activity. Spontaneous activity and stimulus-evoked responses were significantly enhanced by bath application of the potassium channel blocker 4-aminopyridine (4-AP). We are currently optimizing methods to interrogate graft-graft and graft-to-host connectivity. These studies will reveal the extent to which, at the cellular level, current NSC grafts are capable of forming functional neuronal relays across spinal cord injuries.

Grant Support
Wings for Life Individual Research Grant
Grant Support
UCSD Frontiers of Innovation Scholars Program
Grant Support
The Veterans Administration
Grant Support
Nakajima Foundation

Abstract Citation
*S. L. CETO1, K. SEKIGUCHI2, A. NIMMERJAHN3, M. H. TUSZYNSKI4;
1UCSD, LA Jolla, CA; 2Waitt Advanced Biophotonics Ctr., Salk Inst. for Biol. Sci., La Jolla, CA; 3Salk Inst. For Biol. Studies, La Jolla, CA; 4Univ. of California San Diego Dept. of Neurosciences, La Jolla, CA. Calcium imaging of synaptic connectivity between host and neural progenitor cell graft-derived neurons after spinal cord injury. Program No. 138.12. 2018 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience, 2018. Online.

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