Spinal cord injury (SCI) inflicts trauma to the cells and tissues of the central nervous system and causes a severe and debilitating condition in the individual. Following SCI, limited regeneration of injured neurons results in permanent disability characterized by some loss of sensation, paralysis and autonomic dysfunction. One reason that neurons fail to regenerate is their inability to traverse the glial scar that develops following SCI. This glial scar contains extra cellular matrix molecules including chondroitin sulfate proteoglycans (CSPGs). In vitro studies show that neurons fail to extend processes over CSPG coated surfaces, while in vivo data correlate failure of regeneration with areas of CSPG expression. Treatment with bacterial chondroitinase (Chase), an enzyme that digests CSPG arbohydrate chains, decreases the CSPG inhibition, both in vitro and in vivo. Chase was recently used to treat spinal cord lesions in a rodent model, resulting in enhanced functional recovery. Several obstacles exist in the development of a Chase-based SCI therapy, including the delivery of a large protein to the central nervous system and the use of an enzyme with a short half-life in solution at body temperature.
The aim of this study is to develop a sustained release (SR) formulation of a Chase therapy that can be delivered locally to the site of injury and demonstrate its effectiveness at digesting CSPGs in the rat spinal cord. To accomplish these goals are a repertoire of Chase enzymes will be cloned, expressed and purified. These enzymes will then be tested in vitro in several existing sustained release formulations. These sustained release Chase formulations will then be place in the sub-dural space of rat spinal cords to assess their ability to digest CSPGs in vivo. These studies will provide justification for a Phase II study examining the therapeutic effects of sustained release formulation of chondroitinase in an animal model of spinal cord injury.
