A better enzyme to help regenerate the spinal cord

Illustration of human spine

Georgia Tech and Emory researchers have developed an improved version of an enzyme that disintegrates scar tissue formed when the central nervous system (CNS) is damaged. By digesting tissue that blocks regrowth of damaged nerves, the improved enzyme—and a new system for delivering it—could help speed recovery from serious injury to the CNS.

The enzyme, chrondroitinase ABC (chABC), must be supplied to the damaged area for at least two weeks following an injury to fully degrade scar tissue. It also must be infused repeatedly because it functions poorly at body temperature. The researchers were able to eliminate the thermal sensitivity of chABC and to develop a delivery system that allowed the enzyme to remain active for weeks without using implanted catheters and pumps. They published their results in the November 2 issue of Proceedings of the National Academy of Sciences

"These results bring us a step closer to repairing spinal cord injuries, which requires multiple steps including minimizing the extent of secondary injury, bridging the lesion, and stimulating nerve growth," says Ravi Bellamkonda, a biomedical engineer at Georgia Tech and Emory University. 

At body temperature, chABC enzyme loses half of its enzymatic activity within one hour and its remaining functionaity within five days. To stabilize it, Bellamkonda and Emory cell biologist Robert McKeon mixed it with the sugar trehalose. The enzyme's activity then remained stabilized at internal body temperature for up to four weeks.

The researchers then used a lipid microtube-hydrogel scaffold system to provide sustained delivery of the enzyme for two weeks. This delivery system also allowed the enzyme to diffuse deeper into the tissue than did catheter delivery.

In animal studies, the enzyme's ability to digest the scar was retained for two weeks post-injury, and the scar remained significantly degraded for at least six weeks. 

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winter cover 2010