Application of Rho Antagonist to Neuronal Cell Bodies Promotes Neurite Growth in Compartmented Cultures and Regeneration of Retinal Ganglion Cell Axons in the Optic Nerve of Adult Rats

Abstract

Inactivation of Rho promotes neurite growth on inhibitory substrates and axon regeneration in vivo.Here, we compared axon growth when neuronal cell bodies or injured axons were treated with a cell-permeable Rho antagonist (C3-07) in vitro and in vivo. In neurons plated in compartmented cultures, application of C3-07 to either cell bodies or distal axons promoted axonal growth on myelinassociated glycoprotein substrates. In vivo, an injection of C3-07 into the eye promoted regeneration of retinal ganglion cell (RGC) axons in the optic nerve after microcrush lesion. Delayed application of C3-07 promoted RGC growth across the lesion scar. Application of C3-07 completely prevented RGC cell death for 1 week after axotomy. To investigate the mechanism by which Rho inactivation promotes RGC growth, we studied slow axonal transport. Reduction in slow transport of cytoskeletal proteins was observed after axotomy, but inactivation of Rho did not increase slow axonal transport rates. Together, our results indicate that application of a Rho antagonist at the cell body is neuroprotective and overcomes growth inhibition but does not fully prime RGCs for active growth.

MICAL flavoprotein monooxygenases: Expression during neural development and following spinal cord injuries in the rat

“…The development of therapies to promote axonal regeneration will require overcoming these disparate inhibitory influences. Recent work suggests that intracellular signaling pathways which dictate axonal responsiveness to inhibitory proteins are tractable targets for overcoming the inhibitory nature of the injured CNS and encouraging functional regeneration (Bertrand et al, 2005;Cai et al, 1999;Dergham et al, 2002;Fournier et al, 2003;Lehmann et al, 1999;Lu et al, 2004;Neumann et al, 2002;Nikulina et al, 2004;Qiu et al, 2002;Sivasankaran et al, 2004). Unfortunately, our current understanding of the signaling pathways that mediate the effects of inhibitory proteins on regenerating and developing axons is still rudimentary.…”

Expression of a dominant-negative Rho-kinase promotes neurite outgrowth in a microenvironment mimicking injured central nervous system

“…Pharmacological inhibition of RhoA with C3 transferase or inhibition of ROCK with Y27632 has been shown to stimulate neurite growth on inhibitory substrates in vitro. Inhibition of RhoA or ROCK has also been found to promote regeneration of optic nerves and corticospinal axons in vivo [8,[12][13][14][15] . However, the clinical use of these antagonists may be limited by undesired side effects and pharmacokinetics.…”

A Phase I/IIa Clinical Trial of a Recombinant Rho Protein Antagonist in Acute Spinal Cord Injury

“…Previous studies have shown that the inactivation of RhoA (a member of the Rho family of proteins) using C3 transferase, or the inhibition of Rho kinase with the pharmacological inhibitor Y-27632, can promote axon outgrowth on inhibitory substrates in vitro and in vivo (Borisoff et al, 2003;Dergham et al, 2002, Lord-Fontaine et al, 2008. It has also been shown that the inactivation of RhoA with C3 transferase protects neurons from cell death after ischemia or trauma (Bertrand et al, 2007, Dubreuil et al, 2003.…”