Molecular changes at the posterior horn of spinal cord resulting from spinal root avulsion

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The aim of this study was to demonstrate acute to subacute molecular episodes in the dorsal horn following root avulsion using immunohistochemical methods. Hsp27 was accumulated selectively in the injured substantia gelatinosa 24 hours after avulsion injury. The localization of Hsp27 in astrocytes within the substantia gelatinosa was confirmed by the double immunofluorescence and by immunoelectron microscopy for Hsp27. The pattern of Hsp27 expression subsequently changed from glial pattern to punctate pattern by 7 days. Immunoelectron microscopy revealed that the punctate pattern in the subacute stage corresponded to distal parts of the astrocytic processes. We conclude that Hsp27 is a useful marker for demonstrating dorsal horn lesions following avulsion. Next, we examined temporal molecular alterations from the CNS-PNS junction to the ruptured dorsal root after traction injury. At 28 days after dorsal rupture injury, GFAP-positive structures were identified showing rather straight lines from the centro-peripheral junction toward the peripheral stump in the ruptured dorsal root. Glial cell line-derived neurotrophic factor immunoreactivity had appeared showing a process-like profile on the ruptured dorsal root by 28 days, and it was closely related with GFAP-positive structures. We therefore conclude that the astrocytes show a unique ability to extend their processes toward the stump. This ability may provide a new medium for the study of axonal regeneration in future clinical experiments.