Inhibiting cell proliferation during formation of the glial scar: effects on axon regeneration in the CNS
Section snippets
General procedures and animal care
All animal work was carried out in accordance with the UK Animals (Scientific Procedures) Act (1986); all efforts were made to minimise the number of animals used, and their suffering. Adult male Sprague–Dawley rats (200–260 g; n=76) were anaesthetized for 5 min with 5% halothane and 2 L/min O2 prior to surgery. Each animal was positioned into a stereotactic frame where anaesthesia was maintained at 1–2% halothane during surgery (with 0.6 L/min O2 and N2O); the incisor bar was set 2.3 mm below
Results
Groups of animals were examined after five different treatments (see Table 1):
- 1.
pre-lesion saline: animals received a continuous subarachnoid infusion of saline for 7 days, prior to transection of the MFB/nigrostriatal tract;
- 2.
pre-lesion araC: animals received a continuous subarachnoid infusion of araC for 7 days (after Doetsch et al., 1999), prior to MFB transection;
- 3.
lesion only: MFB transection without infusion;
- 4.
post-lesion saline: MFB transection immediately followed by infusion of saline for 7
Injury response of OP cells
As in previous studies Levine, 1994, Ong and Levine, 1999, Bu et al., 2001, McTigue et al., 2001, Jones et al., 2002, Tang et al., 2003 we have shown a substantial increase in the number of NG2+ OP cells around CNS lesions, and a large increase in the intensity of NG2 staining on those cells. Expression of NG2 on cells with the morphology of inflammatory cells or astrocytes was not observed in this study (see also below).
Our first experiment was to infuse the antimitotic, araC, over the surface
Conclusions
Infusion of the antimitotic, araC, over the lesion site for 7 days immediately following a unilateral lesion of the nigrostriatal tract significantly reduced the number of OP cells able to participate in the scar formation. The number of CD11b+ microglia around the lesion was also considerably reduced but GFAP+ astrocytes were not affected. The findings imply that the OP cell population was increased around the lesion by intensive local proliferation whilst the astrocyte population was mainly
Acknowledgements
This work was funded by grants from the Medical Research Council, the International Spinal Research Trust, the Wellcome Trust and Internationales Forschungsinstitut für Paraplegiologie (Zurich). The monoclonal antibody to NG2 was generously donated by Joel Levine, and the polyclonal antibody to GAP43 was a gift from Graham Wilkin.
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Present address: The Miami Project to Cure Paralysis, Miami, FL 33101, USA.