Synaptic connectivity between host and neural progenitor cell-derived neurons after spinal cord injury

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 thirteen (E13)-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.
In acute spinal cord slices, grafted neurons exhibited spontaneous activity. Moreover, dorsal column stimulation evoked responses in grafted cells. In vivo imaging revealed spontaneous activity in both neurons and glia, as well as hindpaw pinch- and cold air puff-evoked responses. Activity patterns included both large-scale events and independent, single-neuron activity. We are currently optimizing methods for interrogating host-to-graft inputs through optogenetic techniques. We are also planning to probe the host response to graft output by stimulating graft axons and imaging host cells in the areas that they innervate. Additionally, using cell type-specific transgenic Cre lines to drive GCaMP expression in grafts, we will assess the activities of different graft cell types.

Authors: *S. L. CETO1, K. J. SEKIGUCHI3, A. NIMMERJAHN3, M. H. TUSZYNSKI2;
1Biomed. Sci., 2Neurosciences, Univ. of California – San Diego, La Jolla, CA; 3Waitt Advanced Biophotonics Ctr., Salk Inst. for Biol. Studies, La Jolla, CA
Disclosures: S.L. Ceto: None. K.J. Sekiguchi: None. A. Nimmerjahn: None. M.H. Tuszynski: None.

Grant Support
The Veterans Administration
Wings for Life
UCSD FISP
Nakajima Foundation

Society for Neuroscience LINK

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