• Kenzo Uchida, Hisatoshi Baba, Yasuhisa Maezawa, and Chikara Kubota.
• Department of Orthopaedic Surgery, School of Medicine, Fukui Medical University, Matsuoka, Fukui, Japan.
• Spine. 2002 Mar 1;27(5):480-6.

Study DesignImmunohistochemical examination of the expression and localization of neurofilament (NF) proteins and growth-associated protein (GAP)-43 in spinal hyperostotic (twy/twy) mice with progressive compression of the cervical spinal cord.ObjectiveTo determine the biologic functions of NF proteins and GAP-43 in the mouse cervical spinal cord during chronic mechanical compression.Summary Of Background DataThe pathologic and repair process in the chronically compressed spinal cord are understood poorly. The present authors hypothesized that there existed an increased expression of NF proteins and GAP-43 in twy/twy mice during the lengthy period of spinal cord compression, which resembles compressive myelopathy.MethodsThe cervical spinal cords of 54 twy mice (aged 8 weeks [n = 18], 14 weeks [n = 18], and 20 weeks [n = 18]) and 18 control animals were examined histologically. Using appropriate antibodies, sections were also stained immunohistochemically for NF proteins and GAP-43.ResultsSeparation of the myelin sheath from the axon and axonal swelling with deformation were detected in the anterior and lateral funiculi of the spinalcords of 20-week-old twy/twy mice. No such changes were noted in 8-week-old twy mice. In twy/twy mice aged 8 and 14 weeks with mild-to-moderate compression, weak immunoreactivities (mainly in the white matter) for NF proteins and GAP-43 were noted; however, in 20-week-old twy/twy mice, these axons stained strongly positive and immunoreactive swollen axons were present. The relative area of GAP-43 immunoreactive axons gradually increased between 8 and 20 weeks in each column, particularly in the anterior and lateral funiculi in the contralateral side of compression.ConclusionsThe results showed that the expression of NF proteins and GAP-43 in the white matter increased proportionally with the magnitude of spinal cord compression, and indicated the possible involvement of GAP-43 in both axonal degeneration and repair processes in the chronically compressed spinal cord.

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