Sustained delivery of thermostabilized chABC enhances axonal sprouting and functional recovery after spinal cord injury

• Published in: Proceedings of the National Academy of Sciences - PNAS 2010-02, Vol.107 (8), p.3340-3345
• Main Authors: Lee, Hyunjung, McKeon, Robert J, Bellamkonda, Ravi V
• Format: Article
• Language: English
• Subjects: Animals; Astrocytes; Axons; Axons - physiology; Biochemistry; Biological Sciences; Chondroitin ABC Lyase - administration & dosage; Chondroitin ABC Lyase - chemistry; Drug Delivery Systems; Enzyme Stability; Glycoproteins; Glycosaminoglycans; Hot Temperature; Lesions; Lipids; Male; Motor Activity - drug effects; Neurons; Physical trauma; Rats; Rats, Sprague-Dawley; Regeneration; Regenerative Medicine: Special Feature; Scaffolds; Scars; Spinal cord; Spinal cord injuries; Spinal Cord Injuries - drug therapy; Spinal Cord Injuries - physiopathology; Sprouting; Trehalose - chemistry
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0905437106

Chondroitin sulfate proteoglycans (CSPGs) are a major class of axon growth inhibitors that are up-regulated after spinal cord injury (SCI) and contribute to regenerative failure. Chondroitinase ABC (chABC) digests glycosaminoglycan chains on CSPGs and can thereby overcome CSPG-mediated inhibition. But chABC loses its enzymatic activity rapidly at 37 °C, necessitating the use of repeated injections or local infusions for a period of days to weeks. These infusion systems are invasive, infection-prone, and clinically problematic. To overcome this limitation, we have thermostabilized chABC and developed a system for its sustained local delivery in vivo, obviating the need for chronically implanted catheters and pumps. Thermostabilized chABC remained active at 37 °C in vitro for up to 4 weeks. CSPG levels remained low in vivo up to 6 weeks post-SCI when thermostabilized chABC was delivered by a hydrogel-microtube scaffold system. Axonal growth and functional recovery following the sustained local release of thermostabilized chABC versus a single treatment of unstabilized chABC demonstrated significant differences in CSPG digestion. Animals treated with thermostabilized chABC in combination with sustained neurotrophin-3 delivery showed significant improvement in locomotor function and enhanced growth of cholera toxin B subunit-positive sensory axons and sprouting of serotonergic fibers. Therefore, improving chABC thermostability facilitates minimally invasive, sustained, local delivery of chABC that is potentially effective in overcoming CSPG-mediated regenerative failure. Combination therapy with thermostabilized chABC with neurotrophic factors enhances axonal regrowth, sprouting, and functional recovery after SCI.