The inability of the spinal cord to regenerate has been attributed to the preponderance of molecules that inhibit axonal growth. Foundation studies support the contention that CSPG is a main inhibitory component in spinal cord tissue. However, findings also suggest that inhibitory CSPG may suppress the growth-promoting potential of normal adult peripheral nerve. Since nerve has an excellent capacity to regenerate, injury must evoke some mechanism by which the damaged nerve is converted from a suppressive environment to one that promotes axonal growth. If so, this conversion somehow fails to occur in damaged spinal cord. In vitro studies show that bacterial chondroitinase and human matrix metalloproteinase-2 (MMP-2) degrade and inactivate inhibitory CSPG present in neural tissues and that nerve and spinal cord tissues contain latent neurite-promoting activities that are revealed after treatment with these enzymes. Experiments in this proposal will test the following main hypotheses: a) enzymatic inactivation of CSPG enhances the neurite-promoting potentials of nerve and spinal cord; b) enzymatic inactivation of CSPG occurs during nerve degeneration; c) inactivation of CSPG during nerve degeneration is MMP-2-dependent and neuronal expression of MMP-2 provides a second, more discrete mechanism for negotiation of inhibited substrata and; d) contrasts in the regenerative capacity of nerve and spinal cord reflect differences in the inactivation of CSPG achieved during degeneration and by injured axons. Experiments that address these hypotheses are presented in five major Aims, all of which center on mechanisms to inactivate inhibitory CSPG and improve nervous system regeneration.
Aims 1 and 2 focus on the inactivation of CSPG in the peripheral nerve by chondroitinase and MMP-2, respectively.
Aims 3 and 4 focus on the actions of these enzymes in the spinal cord. The efficacy of enzyme applications and the neurite-promoting potential of treated nerve and spinal cord tissues will be assayed in vitro and their impact on axonal regeneration will be tested in several in vivo injury models.
Aim 5 will determine die expression of CSPG- inactivating enzymes in the nervous system to better understand the roles of these enzymes in the regenerative process. This information will advance our understanding of the regulation of axonal growth by inhibitory mechanisms and will be applied to devise means to improve axonal regeneration by enzymatic inactivation of CSPG. The main goal of this project is to prove that application of CSPG-degrading enzymes within injured tissues is an effective therapy to improve axonal regrowth and recovery of function throughout the nervous system.
| Graham, James B; Neubauer, Debbie; Xue, Qing-Shan et al. (2007) Chondroitinase applied to peripheral nerve repair averts retrograde axonal regeneration. Exp Neurol 203:185-95 |
| Neubauer, Debbie; Graham, James B; Muir, David (2007) Chondroitinase treatment increases the effective length of acellular nerve grafts. Exp Neurol 207:163-70 |
| Krekoski, Craig A; Neubauer, Debbie; Graham, James B et al. (2002) Metalloproteinase-dependent predegeneration in vitro enhances axonal regeneration within acellular peripheral nerve grafts. J Neurosci 22:10408-15 |
| Zuo, Jian; Neubauer, Debbie; Graham, James et al. (2002) Regeneration of axons after nerve transection repair is enhanced by degradation of chondroitin sulfate proteoglycan. Exp Neurol 176:221-8 |
| Krekoski, C A; Neubauer, D; Zuo, J et al. (2001) Axonal regeneration into acellular nerve grafts is enhanced by degradation of chondroitin sulfate proteoglycan. J Neurosci 21:6206-13 |
