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Published on: February 23, 2015
Expression profile and role of EphrinA1 ligand after spinal cord injury
Luz C Arocho1, Johnny D Figueroa, Aranza I Torrado
1Physiology Department, University of Puerto Rico School of Medicine, P.O. Box 365067, San Juan, PR 00936-5067, USA.
Abstract:
Spinal cord injury (SCI) triggers the re-expression of inhibitory molecules present in early stages of development, contributing to prevention of axonal regeneration. Upregulation of EphA receptor tyrosine kinases after injury suggest their involvement in the nervous system's response to damage. However, the expression profile of their ephrinA ligands after SCI is unclear. In this study, we determined the expression of ephrinA ligands after contusive SCI. Adult Sprague-Dawley female rats were injured using the MASCIS impactor device at the T10 vertebrae, and levels of ephrinA mRNA and protein determined at different time points. Identification of the cell phenotype expressing the ephrin ligand and colocalization with Eph receptors was performed with immunohistochemistry and confocal microscopy. Behavioral studies were made, after blocking ephrinA1 expression with antisense (AS) oligonucleotides, to assess hindlimb locomotor activity. Real-time PCR demonstrated basal mRNA levels of ephrin (A1, A2, A3, and A5) in the adult spinal cord. Interestingly, ephrinA1 was the only ligand whose mRNA levels were significantly altered after SCI. Although ephrinA1 mRNA levels increased after 2 weeks and remain elevated, we did not observe this pattern at the protein level as revealed by western blot analysis. Immunohistochemical studies showed ephrinA1 expression in reactive astrocytes, axons, and neurons and also their colocalization with EphA4 and A7 receptors. Behavioral studies revealed worsening of locomotor activity when ephrinA1 expression was reduced. This study suggests that ephrinA1 ligands play a role in the pathophysiology of SCI.
Insights
Spinal cord injury (SCI) increases ephrinA1 mRNA, but not protein, in rats. Reduced ephrinA1 worsens hindlimb function, suggesting its role in SCI pathophysiology.
Area of Science:
- Neuroscience
- Regenerative Medicine
- Molecular Biology
Background:
- Spinal cord injury (SCI) involves re-expression of developmental inhibitory molecules, hindering axonal regeneration.
- EphA receptors are upregulated post-SCI, indicating a role in neural damage response.
- The expression of ephrinA ligands after SCI remains largely uncharacterized.
Purpose of the Study:
- To investigate the expression profile of ephrinA ligands following contusive SCI.
- To identify cell types expressing ephrinA ligands and their colocalization with Eph receptors.
- To evaluate the functional role of ephrinA1 in locomotor recovery after SCI.
Main Methods:
- Contusive SCI induced in adult female rats using the MASCIS impactor.
- Quantification of ephrinA mRNA and protein levels at various time points post-injury.
- Immunohistochemistry and confocal microscopy for cell phenotyping and receptor colocalization.
- Behavioral assessments of hindlimb locomotor activity following ephrinA1 blockade with antisense oligonucleotides.
Main Results:
- Basal mRNA expression of ephrinA1, A2, A3, and A5 detected in the adult spinal cord.
- EphrinA1 mRNA levels significantly increased 2 weeks post-SCI and remained elevated.
- No corresponding increase in ephrinA1 protein levels observed post-SCI.
- EphrinA1 expressed in reactive astrocytes, axons, and neurons, colocalizing with EphA4 and EphA7 receptors.
- Reduction in ephrinA1 expression led to worsened hindlimb locomotor activity.
Conclusions:
- EphrinA1 is the primary ephrinA ligand affected at the mRNA level after SCI.
- The study suggests a role for ephrinA1 ligands in the pathophysiology of spinal cord injury.
- EphrinA1 may influence neural repair and functional recovery following SCI.
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