Therapeutic time window for the application of chondroitinase ABC after spinal cord injury Guillermo García-Alías a , Rachel Lin a , Sonia F. Akrimi b , David Story a , Elizabeth J. Bradbury b , James W. Fawcett a, ⁎ a Centre for Brain Repair, Department of Clinical Neuroscience, University of Cambridge, Cambridge CB2 0PY, UK b Neurorestoration Group, Wolfson Centre for Age Related Diseases, King's College London, London SE11UL, UK Received 11 July 2007; revised 8 November 2007; accepted 8 November 2007 Available online 21 November 2007 Abstract Rats with a crush in the dorsal funiculi of the C4 segment of the spinal cord were treated with chondroitinase ABC delivered to the lateral ventricle, receiving 6 intraventricular injections on alternate days. In order to investigate the time window of efficacy of chondroitinase, treatment was begun at the time of injury or after a 2, 4 or 7 days delay. Behavioural testing over 6 weeks showed that acutely treated animals showed improved skilled forelimb reaching compared to penicillinase controls. Forelimb contact placing recovered in treated animals but not controls, and gait analysis showed recovery towards normal forelimb stride length in treated animals but not controls. Chondroitinase-treated animals showed greater axon regeneration than controls. The treatment effect on contact placing, stride length and axon regeneration was not dependent on the timing of the start of treatment, but in skilled paw reaching acutely treated animals recovered better function. The area of chondroitinase ABC digestion visualized by stub antibody staining included widespread digestion around the lateral ventricles and partial digestion of cervical spinal cord white matter, but not grey matter. © 2007 Published by Elsevier Inc. Keywords: Chondroitinase ABC; Corticospinal; Spinal cord injury; Regeneration; Plasticity; Proteoglycans; Reaching task; Forelimb Introduction Treatments for traumatic spinal cord injury (SCI) aim to promote axon regeneration across the injury site, or to promote plasticity following partial lesions. Encouraging results have been obtained in animal models with treatments that stimulate axon regeneration, plasticity or both. Digestion or blockade of inhibitory molecules, enhancement of neuronal growth cap- abilities and rehabilitative therapies have all improved the motor and sensory outcome of animals after spinal cord injury (Schwab et al., 2006; Edgerton et al., 2004; Bradbury et al., 2002; Li et al., 2004; Grimpe et al., 2005; Marklund et al., 2006; Massey et al., 2006; Houle et al., 2006; Tan et al., 2006; Galtrey and Fawcett, 2007b). In the majority of these experiments treatment has been initiated acutely after the injury, which will be impracticable in injured patients. Some treatments might be expected to be effective even when given some time after injury. Defining the therapeutic time window for these treatments is an important step towards their clinical application. Chondroitin sulphate proteoglycans (CSPGs) are potent axon growth inhibitors and a principal constituent of the extracellular matrix surrounding glial and neuronal cells (Carulli et al., 2006; Silver and Miller, 2004). They are upregulated after injury in the glial scar where they are the main inhibitory molecules (Asher et al., 2001; McKeon et al., 1991; Jones et al., 2002). They are also present in perineuronal nets, which are probably involved in restricting plasticity in the adult CNS (Carulli et al., 2006; Apostolova et al., 2006; Carulli et al., 2007). The inhibitory properties of the CSPGs depend substantially on the glycosca- minoglycan (GAG) chains, which can be digested by a number of bacterial enzymes. Digestion of CSPGs with chondroitinase ABC (chABC) (Hamai et al., 1997) promotes axon regeneration and plasticity with functional recovery after SCI and in other CNS pathologies (Bradbury et al., 2002; Massey et al., 2006; Davies et al., 1999; Pizzorusso et al., 2006; Caggiano et al., 2005; Houle et al., 2006; Galtrey et al., 2007). Available online at www.sciencedirect.com Experimental Neurology 210 (2008) 331 – 338 www.elsevier.com/locate/yexnr ⁎ Corresponding author. Fax: +44 1223 331174. E-mail address: jf108@cam.ac.uk (J.W. Fawcett). 0014-4886/$ - see front matter © 2007 Published by Elsevier Inc. doi:10.1016/j.expneurol.2007.11.002