Astrocytic reactions in spinal gray matter following sciatic axotomy

Abstract

Astrocytic responses following unilateral sciatic nerve axotomy were examined in the spinal gray matter. Using an antiserum to glial fibrillary acidic protein (GFAP), immunoreactive astrocytes were studied in both dorsal and ventral gray matter at intervals from 2 days through 34 days post-axotomy. In all axotomized animals, increased numbers of strongly immunoreactive astrocytes were present in the gray matter ipsilateral to the surgery. Such astrocytes were absent from the contralateral intact side and from gray matter bilaterally in adjacent spinal segments not involved in formation of the sciatic nerve. These GFAP-positive astrocytes occurred not only in association with large motor neurons in the ventral gray matter but also in association with central processes of dorsal root ganglion neurons in the dorsal gray matter. The response was quite rapid, being discernible both dorsally and ventrally as early as the second post-operative day. This increased GFAP immunoreactivity persisted throughout the entire observation period, with the perikarya of large ventral motor neurons appearing to become surrounded or encapsulated by the immunoreactive processes. A further alteration noted at the longest post-operative intervals was the presence in the ventral gray matter of astrocytes appearing to be binucleate. The data obtained indicate that the astrocytic response is not related solely to reactions in motor neurons and, furthermore, the rapidity with which it develops in the dorsal gray matter suggests that its induction is not dependent upon transganglionic degeneration, which others have reported to occur weeks after peripheral nerve injury.

The Effect of Neonatal Nerve Injury on the Expression of Heat Shock Proteins in Developing Rat Motoneurones

“…However, there was a clear increase in the number of glial cells which stained for hsp70 within the injured ventral horn. It is well established that following neonatal nerve injury an extensive astrogliosis takes place in the spinal cord around the injured motor pool (Gilmore et al, 1990). In this study, there was a marked astrogliosis in the operated ventral horn, with a dramatic increase in the number of GFAP positive astrocytes around the injured motor pool.…”

Collateral Sprouting of Uninjured Primary Afferent A-Fibers into the Superficial Dorsal Horn of the Adult Rat Spinal Cord after Topical Capsaicin Treatment to the Sciatic Nerve

“…It is unlikely that vacant synaptic sites would be sufficient to induce growth in distant afferent terminals, but other changes secondary to terminal degeneration may be responsible. Gliosis and an increase in glial fibrillary acidic protein immunoreactivity in the superficial dorsal horn occur after peripheral nerve injury (Hajos et al, 1990) and involve astroglial cell hypertrophy (Gilmore et al, 1990) before morphological reorganization of afferent terminals (Svensson et al, 1993). Similarly, nerve injury results in a rise in the number of microglia in the dorsal horn (Svensson et al, 1993), and the function of these microglia may involve activities other than phagocytosis of degenerating terminals .…”

Metastasis-associated Mts1 (S100A4) protein is selectively expressed in white matter astrocytes and is up-regulated after peripheral nerve or dorsal root injury

“…Injury to the peripheral branches, e.g., by section of the sciatic nerve, induces degenerative as well as growth-associated changes (transganglionic changes) in the central terminals and axons of the injured neurons (Woolf et al, 1990(Woolf et al, , 1995Aldskogius et al, 1992). Concomitantly, microglial cells proliferate (Gehrmann et al, 1991;Eriksson et al, 1993;Persson et al, 1995) and express various inflammatory mediators (Liu et al, 1995), while astrocytes up-regulate the expression of their major intermediate filament, glial fibrillary acidic protein (GFAP; Gilmore et al, 1990), and GFAP mRNA (Eriksson et al, 1997) but do not proliferate (Liu and Kozlova, 1999). Injury to the central primary sensory process by section of the dorsal root results in complete disintegration (Wallerian degeneration) of the segment of the axon no longer in continuity with the parent cell body.…”