Carbon filaments direct the growth of postlesional plastic axons after spinal cord injury

The effect of implantation of carbon filaments and fetal tissues on the axo nal regeneration following contusion injury in a rat model was investigated by in situ immunofluorescence. Female Sprague-Dawley rats were subjected t o severe contusion injury to the spinal cord at T-9-T-10. All animals were divided into 5 groups (N = 5/group): normal controls, surgical controls, wi th carbon filament implants, with fetal tissue implants and with implants c onsisting of fetal tissue cocultured with carbon filaments. After a 10-week survival period, the astroglial response was assessed by immunoreactive gl ial fibrillary acidic protein and the neuro-axonal profile by immunoreactiv e phosphorylated and nonphosphorylated neurofilament proteins. The contusio n injury resulted in: (a) dramatically increased immunoreactivity of glial fibrillary acidic protein indicating injury-associated reactive astrogliosi s, (b) increase in immunoreactive phosphorylated neurofilament protein indi cating upregulated phosphorylation of neurofilament protein, (c) with no ch ange in the highly differentiated nonphosphorylated neurofilament protein w hich normally occur in the nonregenerating mature neurons. Implantation of fetal tissues alone following contusion injury did not show any appreciable change with regard to the immunoreactivities for the glial and neuronal ma rkers studied, compared to the injury controls. However, the implantation o f carbon filaments alone or together with fetal tissues directed the growth of glial fibrillary acidic protein-positive astroglia and phosphoneurofila ment-positive neurites along the carbon fibers, with no effect on nonphosph oneurofilament protein. In conclusion, implantation of carbon filaments app ears to be critical for facilitating the attachment of astroglia forming a substrate and scaffolding that can further support and direct the growth of postlesional plastic axons across the lesion. In addition, carbon filament prostheses in combination with fetal tissue implants provides an improved combinational approach to promote regrowth of injured neurons following inj ury. (C) 1999 Published by Elsevier Science Ltd on behalf of ISDN. All righ ts reserved.