The Journal of Neuroscience, August 15, 2001, 21(16):6206-6213
Axonal Regeneration into Acellular Nerve Grafts Is Enhanced by
Degradation of Chondroitin Sulfate Proteoglycan
Craig A.
Krekoski1,
Debbie
Neubauer2,
Jian
Zuo1, and
David
Muir1, 2
1 Departments of Neuroscience and
2 Pediatrics (Division of Neurology), University of Florida
Brain Institute and College of Medicine, Gainesville, Florida
32610-0296
Although the peripheral nerve has the potential to regenerate after
injury, degenerative processes may be essential to promote axonal
growth into the denervated nerve. One hypothesis is that the nerve
contains growth inhibitors that must be neutralized after injury for
optimal regeneration. In the present study, we tested whether
degradation of chondroitin sulfate proteoglycan, a known inhibitor of
axon growth, enhances the growth-promoting properties of grafts
prepared from normal donor nerves. Excised segments of rat sciatic
nerve were made acellular by freeze-killing before treatment with
chondroitinase ABC. Chondroitinase-dependent neoepitope immunolabeling
showed that chondroitin sulfate proteoglycan was thoroughly degraded
throughout the treated nerve segments. In addition, neuronal
cryoculture assays revealed that the neurite-promoting activity of
acellular nerves was significantly increased by chondroitinase treatment. Control and chondroitinase-treated acellular nerves were
then used as interpositional grafts in a rat nerve injury model. Axonal
regeneration into the grafts was assessed 4 and 8 d after
implantation by growth-associated protein-43 immunolabeling. At
both time points, the number of axons regenerating into acellular grafts treated with chondroitinase was severalfold greater than in
control grafts. Growth into the chondroitinase-treated grafts was
pronounced after only 4 d, suggesting that the delay of axonal growth normally associated with acellular grafts was attenuated as
well. These findings indicate that chondroitinase treatment significantly enhanced the growth-promoting properties of freeze-killed donor nerve grafts. Combined with the low immunogenicity of acellular grafts, the ability to improve axonal penetration into interpositional grafts by preoperative treatment with chondroitinase may be a significant advancement for clinical nerve allografting.
Key words:
nerve regeneration; acellular nerve graft; chondroitinase; basal lamina; neurite inhibitor; Schwann cell
Copyright © 2001 Society for Neuroscience 0270-6474/01/21166206-08$05.00/0