Effects of Spinal Cord Injury on Motoneuron Morphology Ashley Diamond School of Life Sciences & Center for Adaptive Neural Systems, Ira A. Fulton School of Engineering Arizona State University Tempe, AZ

Spinal Cord Injury Background Information: Most spinal cord injuries are classified as spinal cord contusions (Spinal Cord 2007) Most spinal cord injuries are classified as spinal cord contusions (Spinal Cord 2007) The motoneuron somas (cell bodies) become quite enlarged as a result of the injury. (Bose et al. 2005) The motoneuron somas (cell bodies) become quite enlarged as a result of the injury. (Bose et al. 2005) Supraspinal control is impaired in Spinal Cord injury and muscle atrophy can occur. (Barbeau et al. 2002a; Dietz 1992)

Spinal Cord Injury Continued.. Passive exercise can re This would essentially prevent muscle atrophy by exciting motor pathways. Passive exercise can regularize specific spinal reflexes in the absence of supraspinal control (Skinner et al. 1996). This would essentially prevent muscle atrophy by exciting motor pathways. Active exercise can be induced through electrical stimulation therapy, by implanting electrodes into the motor points of muscles involved in basic flexion and extension needed for walking. Active exercise can be induced through electrical stimulation therapy, by implanting electrodes into the motor points of muscles involved in basic flexion and extension needed for walking. However, the effects of rehabilitative therapy on motoneuron pool densities and morphology can not be assessed without first mapping the lumbar spinal cord before and after injury. However, the effects of rehabilitative therapy on motoneuron pool densities and morphology can not be assessed without first mapping the lumbar spinal cord before and after injury.

Objective: To reconstruct spinal cord morphology from histological sections of the lumbar regions containing fluorescently labeled motoneurons of four muscles. Significance: The reconstructions will provide a map of neuron pools and quantitative data for soma sizes so that the effects of Spinal Cord Injury on motoneuron morphology and pool densities can be assessed in future experiments.

Spinal Cord Injury Model SCI is mimicked by implementing a T-8 dorsal contusion in a rodent.

Muscles were injected with a fluorescent labeled Choleratoxin beta sub unit (CTβ) and Alexfluor 594 Red/Green in order to fluoresce corresponding motoneuron pools Fairchild et al, 2007 Red: Tibialis Anterior, Illiacus Green: Gastrocnemius Medialis, Bicep Femoralis

Trace Spinal Cord Sections Grey matter Central canal White matter Ventral Horn Dorsal Horn 2.5x magnification of 40 micrometer thick section (Z-axis) 1000 microns

Control Vs. Contused Spinal Cord Reconstruction Rostral side looking down White matter Grey Matter Caudal Rostral Grey matter White matter Rostral White matter Caudal Grey Matter Dorsal Ventral Dorsal Ventral Dorsal Ventral Normal Contused

Nucleus Primary Dendrites Cell body or soma 20x magnification of 40 micrometer thick sections of spinal cord Fluorescent retrogradely labeled motoneurons Biceps Femoralis Tibialis Anterior 100 Microns

% location in the mediolateral axis =A*100/(A+B) % location in the dorsoventral axis =C*100/(C+D) Mapping Pool Locations Quantitative Data Neuron 1 Neuron 2 Neuron 3 Neuron 4 Neuron 1 Neuron 2 Neuron 3 Neuron 4

Bicep Femoralis neuron pool White Matter Grey Matter Caudal Rostral Dorsal Ventral Location of Motoneuron Pools in Normal Rodent Lumbar Spinal Cord

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Thank you! Ranu Jung, PhD Director, Center for Adaptive Neural Systems, ASU Director, Center for Adaptive Neural Systems, ASU James Lynskey, PhD, PT Center for Adaptive Neural Systems, ASU and AT Still University Center for Adaptive Neural Systems, ASU and AT Still University Alex Iarkov, PhD Center for Adaptive Neural Systems, ASU Seung-Jae Kim, PhD Center for Adaptive Neural Systems, ASU Mallika Fairchild Center for Adaptive Neural Systems & Harrington Dept. of Bioengineering, ASU Brian Hillen Center for Adaptive Neural Systems & Harrington Dept. of Bioengineering, ASU Funding: NASA Space Grant NASA Space Grant NIH NIH Center for Adaptive Neural Systems;IRA A. Fulton School of Engineering at ASU Center for Adaptive Neural Systems;IRA A. Fulton School of Engineering at ASU