Immobilization of chondroitinase ABCI on chitosan beads to improve axonal regrowth in CSPG-enriched astrocyte culture

Abstract

After nerve injury, scar tissue enriched in chondroitin sulfate proteoglycans (CSPGs) is often formed to contain the lesion but is restrictive to axonal regrowth. Chondroitinase ABCI (ChABCI) has been exploited to cleave CS moieties of the PGs and thus to enhance prospects of axonal regrowth through the lesion. ChABCI activity decay in vivo has however hindered application of the enzyme in nerve regeneration. We attempted to address this by immobilization of recombinant ChABCI on a selected matrix. Chitosan was chosen because it is non-toxic, biocompatible and tunable in rate of biodegradation. We prepared chitosan beads (73.89μm±28.59) that precluded phagocytosis by inflammatory cells. ChABCI that was cross-linked to the chitosan beads under specified conditions demonstrated CS-cleaving activity both in biochemical assay and in astrocyte cultures that had been activated to secrete CSPGs. Factors that contribute to activity decay as thermal instability and susceptibility to end product inhibition are assessed. Axonal regrowth on activated astrocyte cultures was improved by co-treatment with ChABC I and ChABC II.