Inhibition of Rho kinase (ROCK) increases neurite outgrowth on chondroitin sulphate proteoglycan in vitro and axonal regeneration in the adult optic nerve in vivo

Inhibitory molecules derived from CNS myelin and glial scar tissue are major causes for insufficient functional regeneration in the mammalian CNS. A multitude of these molecules signal through the Rho/Rho kinase (ROCK) pathway. We evaluated three inhibitors of ROCK, Y- 27632, Fasudil (HA-1077), and Dimethylfasudil (H-1152), in models of neurite outgrowth in vitro. We show, that all three ROCK inhibitors partially restore neurite outgrowth of Ntera-2 neurons on the inhibitory chondroitin sulphate proteoglycan substrate. In the rat optic nerve crush model Y-27632 dose-dependently increased regeneration of retinal ganglion cell axons in vivo. Application of Dimethylfasudil showed a trend towards increased axonal regeneration in an intermediate concentration. We demonstrate that inhibition of ROCK can be an effective therapeutic approach to increase regeneration of CNS neurons. The selection of a suitable inhibitor with a broad therapeutic window, however, is crucial in order to minimize unwanted side effects and to avoid deleterious effects on nerve fiber growth.