Research

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Scott R. Whittemore, Ph.D.

Richard L. Benton, Ph.D.

Scott Myers, Ph.D.

Sujata Saraswat, Ph.D.


Toros Dincman

Nicholas Kuypers

 

 

Scott R. Whittemore

The general research focus of my laboratory is to utilize molecular and cellular biological techniques to address repair in spinal cord injury (SCI). These studies are usually initiated in vitro and successful approaches then taken into whole animal experiments. When designing strategies to facilitate functional restoration in SCI, three issues need to be considered: 1) replacement of lost neurons, 2) remyelination of de-myelinated and/or regenerating axons, and 3) inducing axotomized descending motor and ascending sensory axons to regenerate. We are utilizing multiple strategies to examine all three issues.

Neuronal replacement requires transplantation of exogenous neurons, as CNS neurons do not regenerate. Similarly, injury-induced de-myelination is secondary to a loss of intrinsic oligodendrocytes. Our approach to re-myelination is to transplant oligodendrocyte precursors into the demyelinated area. We are using CNS-derived stem cells as a source for both neurons and oligodendrocytes. Ongoing experiments in vitro are using retroviral vectors to infect the undifferentiated precursor cells with transcription factors that direct either neuronal or oligodendrocytic differentiation. Additionally, we isolate neuronal-restricted and glial-restricted populations of precursor cells. These cells are then engrafted into specific SCI models that deplete functionally discrete populations of neurons or endogenous oligodendrocytes in specific ventral motor pathways. We utilize a battery of behavioral and electrophysiological analyses to both characterize the initial deficits and determine the degree to which functional recovery is observed.

Our attempts to engender axotomized supraspinal, propriospinal, and sensory axons to regenerate takes a two-fold approach. We again use undifferentiated stem cells and genetically engineer them to express specific neurotrophic factors and/or cell surface molecules that facilitate regeneration by providing trophic support or a permissive substrate for regeneration. In these studies, we induce the stem cells towards an astrocytic phenotype in vivo, as early differentiating astrocytes are permissive for axonal outgrowth. Concomitant with the engraftment of these cells into the injured spinal cord, we use adenoviral or lentiviral vectors to deliver specific neurotrophic molecules at specific times post-injury to the cell bodies in the brainstem and/or into the spinal cord caudal to the injury site. This should enhance the regenerative capacity of the axotomized neurons and coax the regenerating fibers to leave the graft and enter the distal cord, respectively. In the second approach, we are characterizing in the injured spinal cord and brain the expression of the eph family of receptor tyrosine kinases and their ligands the ephrins. These molecules mediate repulsive interactions between cells that express receptor and ligand. We hypothesize that the expression of ephs and ephrins in the injured spinal cord may contribute to the non-permissive environment for regeneration. We have devised a number of reagents that can block the function of these molecules and are examining their effects on regeneration of specific ascending and descending fiber populations.

We recognize that no single strategy will be by itself effective in eliciting optimal regeneration in SCI. Our ultimate goal is to combine those individual strategies of ours and our colleagues here in the Department of Neurological Surgery that are effective to design interventive approaches that will result in functionally significant improvements after SCI

 

Richard Benton

My general research interests focus on the development of novel therapeutic strategies for the treatment of spinal cord injury (SCI). Working in collaboration with the faculty in the Kentucky Spinal Cord Injury Research Center (KSCIRC, www.kscirc.org), we continue to develop stem cell-based therapies facilitating neuronal replacement, spinal regeneration, and ex vivo gene therapy. More specifically, our recent efforts have been focused on better understanding vascular mechanisms of spinal cord injury.


Following traumatic SCI, the delicate microvascular network of the spinal cord is damaged and exhibits hyperacute pathology including petichial hemorrhage, leakiness, and endothelial cell death. Interestingly, the spinal microvasculature undergoes a second phase of dysfunction, which begins 3-7 days following the initial traumatic insult. Little is known about this second wave of microvascular pathology but it appears to be largely regulated by various cellular and molecular secondary injury cascades and ultimately results in further vascular destabilization and dysfunction, which contributes to the secondary loss of spinal tissue. Thus, we are actively advancing research focused on characterizing the anatomy and physiology of spinal vessels in the evolving injury epicenter, developing intravital tracing techniques to identify both normal and pathologic spinal microvessels, and identify novel molecular regulators of vascular pathology following SCI. Our ultimate goal is the development of vascular-focused therapeutic strategies, both stem cell-based and small molecule-centric, which will both stabilize degenerating microvessels and promote the growth of functional microvascular networks. We feel this is a promising area of research that will one day lead to functional recovery following SCI.

 

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