Quantitative Assessment of Ischemic Pathology in Axons, Oligodendrocytes, and Neurons: Attenuation of Damage after Transient Ischemia

Abstract

Axons and oligodendrocytes are vulnerable to cerebral ischemia. The absence of quantitative methods for assessment of white matter pathology in ischemia has precluded in vivo evaluation of therapeutic interventions directed at axons and oligodendrocytes. The authors demonstrate here that the quantitative extent of white matter pathology was reduced by restoration of cerebral blood flow after 2 hours of middle cerebral artery occlusion. Focal ischemia was induced in anesthetized rats by intraluminal thread placement, either transiently (for 2 hours) or permanently. At 24 hours after induction of ischemia, axonal damage was determined by amyloid precursor protein (APP) immunohistochemistry, and the ischemic insult to oligodendrocytes was assessed by Tau-1 immunostaining in the same sections. In adjacent sections, ischemic damage to neuronal perikarya was defined histologically. The hemispheric extent of axonal damage was reduced by 70% in the transiently occluded animals from that in permanently occluded animals. The volumes of oligodendrocyte pathology and of neuronal perikaryal damage were reduced by 62% and 58%, respectively, in the transiently occluded animals. These results demonstrate that this methodologic approach for assessing ischemic damage in axons and oligodendrocytes can detect relative alterations in gray and white matter pathology with intervention strategies.

Ebselen Protects Both Gray and White Matter in a Rodent Model of Focal Cerebral Ischemia

“…21 However, more recently, methods for quantification of white matter damage have been developed. 16,17,22,28 With the use of APP accumulation to highlight axonal damage and Tau-1 staining for oligodendrocyte pathology, Valeriani et al 18 demonstrated that reperfusion of ischemic tissue salvaged axons and oligodendrocytes, in addition to neuronal perikarya from ischemic damage; Irving et al 22 demonstrated that a free radical scavenger but not an NMDA or AMPA antagonist could salvage oligodendrocytes; and Yam et al 17 reported the failure of the NMDA receptor antagonist MK-801 to influence axonal damage while producing a 30% reduction in gray matter damage compared with control. NMDA antagonists are targeted toward salvaging gray matter, the failure to protect against axonal damage most probably reflecting the lack of NMDA receptors in white matter.…”

“…Failure to ameliorate ischemic damage to white matter has been proposed to be one of the major factors, 14 and the importance of white matter damage as well as gray matter in experimental stroke is increasingly recognized. [15][16][17][18] The first aim of this study was to comprehensively assess the neuroprotective efficacy of delayed treatment with an improved, intravenous formulation of ebselen in an established model of experimental stroke. We used conventional histopathology to assess gray matter damage (perikarya), quantification of subcortical white matter damage (axons and oligodendrocytes), and scoring of neurological deficit.…”

Poly(ADP-ribose) polymerase inhibition protect neurons and the white matter and regulates the translocation of apoptosis-inducing factor in stroke

“…Immunohistochemical detection of APP (Alzheimer precursor protein) was conducted according to Valeriani and colleagues (11). Dewaxed sections were microwaved for 10 min in 10 mmol/l citric acid (pH 6.0), allowed to cool, and incubated in 3% H 2 O 2 in methanol for 30 min and then for 1 h in 50 mmol/l PBS (pH 7.2) containing 0.5% bovine serum albumin and 10% normal horse serum.…”

Oligodendrocytes and Ischemic Brain Injury

“…This method has the advantage that it can be combined with quantitative histology to determine neuronal damage, and with immunostaining to determine the amount of axonal damage, in adjacent sections. Rat brain diagrams of 4 (from a total of 8) selected coronal planes, with the areas containing tau-positive oligodendrocytes indicated by black shading, 22 h after either permanent or transient MCA occlusion in the rat (Valeriani et al, 2000). This method showed that the extent of oligodendrocyte pathology was significantly less after early reperfusion compared with permanent ischemia and that this was accompanied by less neuronal and axonal damage (Valeriani et al, 2000).…”

“…4). For example, in the study of Valeriani et al (2000), the volume of tissue containing tau-positive oligodendrocytes, in animals that had experienced early reperfusion of the tissue after 2 h of intraluminal-thread MCAO, was reduced compared with that in animals subjected to permanent artery occlusion. Early tissue reperfusion significantly reduced oligodendrocyte pathology in the cerebral cortex but reduced it to a much lesser degree in subcortical areas.…”