title: Spontaneous regeneration of the corticospinal tract after transection in young rats: collagen type IV deposition and astrocytic scar in the lesion site are not the cause but the effect of failure of regeneration.
abstract: In young rats the corticospinal tract regenerated after a single transection of the spinal cord with a sharp blade, but regeneration failed if the transection was repeated to make a more traumatic injury. To identify cells and associated molecules that promote or impede regeneration, we compared expression of collagen type IV, glial fibrillary acidic protein (GFAP), and vimentin immunoreactivity (IR) at the lesion sites in combination with anterograde axonal tracing between animals with two types of transection. Axonal regeneration occurred as early as 18 hours after transection; regenerating axons penetrated vessel-like structures with collagen type IV-IR at the lesion site, while reactive astrocytes coexpressing GFAP- and vimentin-IR appeared in the lesioned white matter. In contrast, when regeneration failed astrocytes were absent near the lesion. By 7 days sheet-like structures with collagen type IV-IR and astrocytic scar appeared in the lesioned white matter and persisted until the end of the observation period (31 days). On the basis of their spatiotemporal appearance, collagen type IV-IR sheet-like structures and the astrocytic scar follow, rather than cause, the failure of regeneration. The major sign, and perhaps cause, of failure of axonal regeneration is likely the prolonged disappearance of astrocytes around the lesion site in the early postinjury period.
authors.affiliation: Department of Integrative Brain Science, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Iseda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishio
authors.forename: Saburo
authors.initials: S
authors.lastname: Kawaguchi
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kawasaki
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Wakisaka
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000473:pathology; D001369:Axons; D002921:Cicatrix / Q000209:etiology / Q000473:pathology; D024141:Collagen Type IV / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D009416:Nerve Regeneration; D011712:Pyramidal Tracts / Q000473:pathology / Q000503:physiopathology*; D051381:Rats; D013118:Spinal Cord Diseases / Q000209:etiology / Q000473:pathology; D013119:Spinal Cord Injuries; D014746:Vimentin / Q000378:metabolism
chemical_list: D024141:Collagen Type IV; D005904:Glial Fibrillary Acidic Protein; D014746:Vimentin