Effects of Spinal Cord Injury Effects of Spinal Cord Injury on Motoneuron Morphologyon Motoneuron Morphology

Ashley DiamondAshley DiamondAshley.Diamond@asu.edu

School of Life Sciences

&

Center for Adaptive Neural Systems, Ira A. Fulton School of Engineering

Arizona State University

Tempe, AZ

Spinal Cord Injury Spinal Cord Injury Background Information:Background Information:

Most spinal cord injuries are classified Most spinal cord injuries are classified as spinal cord contusions as spinal cord contusions (Spinal Cord 2007)(Spinal Cord 2007)

The motoneuron somas (cell bodies) The motoneuron somas (cell bodies) become quite enlarged as a result of become quite enlarged as a result of the injury. the injury. (Bose et al. 2005)(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..Spinal Cord Injury Continued..

Passive exercise can rePassive exercise can regularize specific spinal reflexes in the absence of supraspinal control (Skinner et al. 1996). This would This would essentially prevent muscle atrophy by essentially prevent muscle atrophy by exciting motor pathways. exciting motor pathways.

Active exercise can be induced through Active exercise can be induced through electrical stimulation therapy, by implanting electrical stimulation therapy, by implanting electrodes into the motor points of muscles electrodes into the motor points of muscles involved in basic flexion and extension involved in basic flexion and extension needed for walking.needed for walking.

However, the effects of rehabilitative therapy However, the effects of rehabilitative therapy on motoneuron pool densities and on motoneuron pool densities and morphology can not be assessed without first morphology can not be assessed without first mapping the lumbar spinal cord before and mapping the lumbar spinal cord before and after injury. after injury.

Objective:Objective:

To reconstruct spinal cord morphology from To reconstruct spinal cord morphology from histological sections of the lumbar regions histological sections of the lumbar regions containing fluorescently labeled containing fluorescently labeled motoneurons of four muscles.motoneurons of four muscles.

Significance:Significance:

The reconstructions will provide a map of The reconstructions will provide a map of neuron pools and quantitative data for soma neuron pools and quantitative data for soma sizes so that the effects of Spinal Cord sizes so that the effects of Spinal Cord Injury on motoneuron morphology and pool Injury on motoneuron morphology and pool densities can be assessed in future densities can be assessed in future experiments.experiments.

Spinal Cord Injury ModelSpinal Cord Injury Model

SCI is mimicked by implementing a T-8 SCI is mimicked by implementing a T-8 dorsal contusion in a rodent. dorsal contusion in a rodent.

Muscles were injected with a fluorescent labeled Muscles were injected with a fluorescent labeled Choleratoxin beta sub unit (CTβ) and Alexfluor 594 Choleratoxin beta sub unit (CTβ) and Alexfluor 594

Red/Green in order to fluoresce corresponding Red/Green in order to fluoresce corresponding motoneuron poolsmotoneuron pools

Fairchild et al, 2007

Red: Tibialis Anterior, Illiacus Red: Tibialis Anterior, Illiacus Green: Gastrocnemius Medialis, Bicep FemoralisGreen: Gastrocnemius Medialis, Bicep Femoralis

Trace Spinal Cord SectionsTrace Spinal Cord Sections

Grey matter

Central canalWhite matter

Ventral Horn

Dorsal Horn

2.5x magnification of 40 micrometer thick section (Z-

axis)

1000 microns

Control Vs. Contused Spinal Cord Control Vs. Contused Spinal Cord ReconstructionReconstruction

Rostral side looking down

Rostral side looking down

White matter

Grey Matter

Caudal Rostral

Grey matter

White matter

Rostral

White matterCaudal

Grey Matter

Dorsal

Ventral

Dorsal

Ventral

Dorsal

Ventral

Normal Contused

NucleusPrimary Dendrites

Primary Dendrites

Cell body or soma

20x magnification of 40 micrometer thick sections of spinal cord

Fluorescent retrogradely labeled Fluorescent retrogradely labeled motoneuronsmotoneurons

Biceps FemoralisBiceps Femoralis Tibialis AnteriorTibialis Anterior

100 Microns

100 Microns

% location in the mediolateral axis =A*100/(A+B)

% location in the dorsoventral axis =C*100/(C+D)

Mapping Pool Locations Quantitative Mapping Pool Locations Quantitative DataData

Neuron 1Neuron 2

Neuron 3

Neuron 4

Neuron 1Neuron 2

Neuron 3

Neuron 4

Bicep Femoralis neuron pool

White Matter

Grey Matter

Caudal

RostralDorsal Ventral

Location of Motoneuron Pools in Location of Motoneuron Pools in Normal Rodent Lumbar Spinal CordNormal Rodent Lumbar Spinal Cord

ReferencesReferences Barbeau H, Ladouceur M, Mirbagheri MM, and Kearney RE. The effect of Barbeau H, Ladouceur M, Mirbagheri MM, and Kearney RE. The effect of

locomotor training combined with functional electrical stimulation in locomotor training combined with functional electrical stimulation in chronic spinal cord injured subjects: walking and reflex studies. Brain chronic spinal cord injured subjects: walking and reflex studies. Brain Res Brain Res Rev 40: 274-291, 2002b.Res Brain Res Rev 40: 274-291, 2002b.

Bose P, Parmer R, Reier PJ, and Thompson FJ. Morphological changes of Bose P, Parmer R, Reier PJ, and Thompson FJ. Morphological changes of the soleus motoneuron pool in chronic midthoracic contused rats. the soleus motoneuron pool in chronic midthoracic contused rats. Neurology. 191: 13-23, 2005.Neurology. 191: 13-23, 2005.

Dietz V. Human neuronal control of automatic functional movements: Dietz V. Human neuronal control of automatic functional movements: interaction between central programs and afferent input. Physiology interaction between central programs and afferent input. Physiology Rev 72: 33-69, 1992.Rev 72: 33-69, 1992.

Fairchild, Mallika, M., J.W. Graham, A.V. Iarkov, D. Hagner; R. Jung. Fairchild, Mallika, M., J.W. Graham, A.V. Iarkov, D. Hagner; R. Jung. Characterization of motoneuron morphology in a complete and incomplete spinal cord injury in Rodent models. Program Number 76.4, 2007. Neuroscience Meeting Planner. San Diego, CA. Society of Neuroscience, 2007, Online (November 3rd- November 7th Poster Presentation)

Skinner RD, Houle JD, Reese NB, Berry CL, and Garcia-Rill E. Effects of Skinner RD, Houle JD, Reese NB, Berry CL, and Garcia-Rill E. Effects of exercise and fetal spinal cord implants on the H-reflex in chronically exercise and fetal spinal cord implants on the H-reflex in chronically spinalized adult rats. Brain Res 729: 127-131, 1996.spinalized adult rats. Brain Res 729: 127-131, 1996.

Spinal Cord Injury: Definition, Epidemiology, Pathophysiology. E-Spinal Cord Injury: Definition, Epidemiology, Pathophysiology. E-Medicine. 21 February 2007. Medicine. 21 February 2007. http://www.emedicine.com/pmr/topic182.htmhttp://www.emedicine.com/pmr/topic182.htm

Thota AK, Watson SC, Knapp E, Thompson B, and Jung R. Thota AK, Watson SC, Knapp E, Thompson B, and Jung R. Neuromechanical control of locomotion in the rat. J Neurotrauma 22: Neuromechanical control of locomotion in the rat. J Neurotrauma 22: 442-465, 2005 442-465, 2005

Thank you!Thank you!Ranu Jung, PhDRanu Jung, PhD Director, Center for Adaptive Neural Systems, ASUDirector, Center for Adaptive Neural Systems, ASU

James Lynskey, PhD, PTJames Lynskey, PhD, PT Center for Adaptive Neural Systems, ASU and AT Still Center for Adaptive Neural Systems, ASU and AT Still

UniversityUniversity

Alex Iarkov, PhDAlex Iarkov, PhDCenter for Adaptive Neural Systems, ASUCenter for Adaptive Neural Systems, ASU

Seung-Jae Kim, PhDSeung-Jae Kim, PhDCenter for Adaptive Neural Systems, ASUCenter for Adaptive Neural Systems, ASU

Mallika FairchildMallika FairchildCenter for Adaptive Neural Systems & Harrington Center for Adaptive Neural Systems & Harrington Dept. of Bioengineering, ASUDept. of Bioengineering, ASU

Brian HillenBrian HillenCenter for Adaptive Neural Systems & Harrington Center for Adaptive Neural Systems & Harrington Dept. of Bioengineering, ASUDept. of Bioengineering, ASU

Funding:Funding: NASA Space GrantNASA Space Grant NIH NIH Center for Adaptive Neural Systems;IRA A. Center for Adaptive Neural Systems;IRA A.

Fulton School of Engineering at ASUFulton School of Engineering at ASU