CS-GAG Mediated Inhibition of the Central Nervous System Regeneration
Hyun-Jung Lee
Injury to the central nervous system triggers an inflammatory response, which then activates astrocytes. Activated astrocytes produce chondroitin sulfate proteoglycans (CSPGs), molecules known to inhibit nerve regeneration. The mechanism by which these molecules inhibit regeneration is poorly understood. Some proteoglycans are inhibitory based on their protein portion, while others need the glycosylation (sugar portion) for inhibition to occur.
This project has three segments that deal specifically with trying to better understand inhibition by analyzing the glycosylated portion of proteoglycans.
1. Does the chemical structure of glycosaminoglycans (GAGs - glycosylated section of proteoglycans) change during injury as opposed to when proteoglycans are produced during development (Figure 1)?
Using fluorophore-assisted carbohydrate electrophoresis (FACE), a technology that is able to quantify different disaccharide populations in tissue, we are examining whether glycosaminoglycan character changes in response to central nervous system damage.
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Figure 1. Chondroitin sulfate proteoglycans are used during development so that neurons can find their correct terminal targets and chemically consist of protein and sugar (glycosaminoglycan) components. When injury occurs, proteoglycans are produced by activated astrocytes, and these astrocytes may produce proteoglycans that have different sugar structures. |
2. If the chemical structure does change, are these upregulated GAG moieties inhibitory to neurite extension?
Using agarose hydrogels and coupling chemistry, we are able to bind GAGs to the agarose backbound. Then introducing ganglia to the biomaterial, we are able to assess the degree by which GAGs are inhibitory to neurite outgrowth (Figure 2).
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Figure 2.In vitro assay that analyzes how neurons regenerate in various chondroitin suflate glycosaminoglycan environments. |
3. If certain GAGs are inhibitory to neurite extension, is there a method that one can use to mask these inhibitory GAGs to facilitate regeneration into the damaged central nervous system?
We are currently looking into the possibility of finding ligands that have an affinity for binding to glycosaminoglycan structures. If candidate ligands are found, then it may be possible to infuse these ligands into the damaged central nervous system to block chondroitin sulfate glycosaminoglycan mediated inhibition.