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Induction of Eph B3 after spinal cord injury
J D Miranda1, L A White, A E Marcillo
1Department of Neurological Surgery, University of Miami School of Medicine, 1600 Northwest 10th Avenue, R-48, Miami, Florida 33136, USA.
Abstract:
Spinal cord injury (SCI) in adult rats initiates a cascade of events producing a nonpermissive environment for axonal regeneration. This nonfavorable environment could be due to the expression of repulsive factors. The Eph receptor protein tyrosine kinases and their respective ligands (ephrins) are families of molecules that play a major role in axonal pathfinding and target recognition during central nervous system (CNS) development. Their mechanism of action is mediated by repellent forces between receptor and ligand. The possible role that these molecules play after CNS trauma is unknown. We hypothesized that an increase in the expression of Eph proteins and/or ephrins may be one of the molecular cues that restrict axonal regeneration after SCI. Rats received a contusive SCI at T10 and in situ hybridization studies 7 days posttrauma demonstrated: (i) a marked up-regulation of Eph B3 mRNA in cells located in the white matter at the lesion epicenter, but not rostral or caudal to the injury site, and (ii) an increase in Eph B3 mRNA in neurons in the ventral horn and intermediate zone of the gray matter, rostral and caudal to the lesion. Immunohistochemical analyses localizing Eph B3 protein were consistent with the mRNA results. Colocalization studies performed in injured animals demonstrated increased Eph B3 expression in white matter astrocytes and motor neurons of the gray matter. These results suggest that Eph B3 may contribute to the unfavorable environment for axonal regeneration after SCI.
Insights
Spinal cord injury (SCI) in adult rats may involve increased Eph B3 expression. This protein tyrosine kinase may create a nonpermissive environment, hindering axonal regeneration after central nervous system trauma.
Area of Science:
- Neuroscience
- Molecular Biology
- Regenerative Medicine
Background:
- Spinal cord injury (SCI) creates a challenging environment for nerve regeneration.
- Repulsive molecular cues are suspected contributors to this nonpermissive environment.
- Eph receptor tyrosine kinases and ephrins are known for their role in axonal guidance during development.
Purpose of the Study:
- To investigate the role of Eph proteins and ephrins in restricting axonal regeneration after SCI.
- To test the hypothesis that increased Eph/ephrin expression contributes to the post-SCI environment.
Main Methods:
- Adult rats underwent a T10 contusive SCI.
- In situ hybridization was used to analyze Eph B3 mRNA expression 7 days post-injury.
- Immunohistochemistry and colocalization studies identified Eph B3 protein expression in specific cell types.
Main Results:
- A significant upregulation of Eph B3 mRNA was observed in white matter at the lesion epicenter.
- Eph B3 mRNA also increased in gray matter neurons, both rostral and caudal to the injury.
- Immunohistochemistry confirmed increased Eph B3 protein in white matter astrocytes and gray matter motor neurons.
Conclusions:
- Eph B3 expression is markedly increased in specific cell populations after SCI in rats.
- These findings suggest Eph B3 may be a molecular factor contributing to the inhibitory environment for axonal regeneration post-SCI.