COMPLETE SPINAL CORD TRANSECTION TREATEDBY IMPLANTATION OF A REINFORCED SYNTHETIC HYDROGEL CHANNEL RESULTS IN SYRINGOMYELIA AND CAUDAL MIGRATION OF THE ROSTRAL STUMP

Abstract

OBJECTIVE Previously, we reported that synthetic poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (PHEMA-MMA) channels promoted regeneration of a small number of axons from brainstem motor nuclei yet provided limited functional recovery after complete spinal cord transection (SCT) at T8 in rats. However, we found that these modulus channels partially collapsed over time. Therefore, we synthesized coil-reinforced PHEMA or PHEMA-MMA channels with greater elastic moduli and introduced a new spinal fixation technique to prevent collapse. We also assessed axonal regeneration within the new channels containing a cocktail of autologous peripheral nerve grafts, fibrin matrix and acidic fibroblast growth factor. METHODS After SCT, rats were divided into 6 groups: Groups 1 and 2) had either a PHEMA or PHEMA-MMA reinforced channel implanted between the stumps of the transected spinal cord with the cocktail; Groups 3 and 4) had either an unfilled reinforced PHEMA or PHEMA-MMA channel similarly implanted; Group 5) had an SCT without channel implanted and Group 6) underwent the identical procedure to Group 1, but rats were sacrificed by 8 weeks for early histological assessment. Groups 1–5 were sacrificed at 18 weeks. RESULTS There was no channel collapse at any time. However, there was no improvement in axonal regeneration or functional recovery among Groups 1–4 because of the unexpected development of syringomyelia and caudal migration of the rostral stump. Functional recovery was better in Groups 1–4 compared to Group 5 (P < 0.05). CONCLUSION The use of channels to enhance regeneration of axons is promising; however, their design must be ameliorated to overcome these complications.