Immunohistochemical detectability of cerebrovascular utrophin depends on the condition of basal lamina

Disappearance of cerebrovascular laminin immunoreactivity as related to the maturation of astroglia in rat brain

The present paper provides novel findings on the temporo-spatial correlation of perivascular laminin immunoreactivity with the early postnatal astrocyte development. The cerebrovascular laminin immunoreactivity gradually disappears during development. The fusion of the glial and vascular basal laminae during development makes the laminin epitopes inaccessible for antibody molecules (Krum et al., 1991, Exp Neurol 111:151). The fusion is supposed to correlate with the maturation of the glio-vascular connections. Glial development was followed by immunostaining for GFAP (glial fibrillary acidic protein), S100 protein, glutamine synthetase as glial markers and for nestin to visualize the immature glial structures. Our investigation focused on the period from postnatal day (P)2 to P16, on the dorso-parietal pallium. In the wall of the telencephalon the laminin immunoreactivity disappeared between P5 and P10; in subcortical structures it persisted to P12 or even to P16. Its disappearance overlapped the period when GFAP-immunopositive astrocytes were taking the place of radial glia. Despite the parallel time courses, however, the spatial patterns of the two processes were just the opposite: disappearance of the laminin immunoreactivity progressed from the middle zone whereas the appearance of GFAP from the pial surface and the corpus callosum. Rather, the regression of the vascular laminin immunoreactivity followed the progression of the immunoreactivities of glutamine synthetase and S100 protein. Therefore, the regression really correlates with a 'maturation' of astrocytes which, however, affects other astrocyte functions rather than cytoskeleton.

Postmortem immunohistochemical alterations following cerebral lesions: A possible pathohistological importance of the β-dystroglycan immunoreactivity

The frequency of cerebrovascular injuries raises the importance of their immunohistological investigation in postmortem materials. Most injuries involve the impairment of the blood-brain barrier. The barrier is maintained by the glio-vascular connections which break up following injuries. Some immunohistochemical alterations may refer to the impairment of the gliovascular connections. Laminin and the components of the dystroglycan complex show characteristic immunohistochemical alterations following various experimental injuries (stab wound, cryogenic lesion, arterial occlusions): immunoreactivity of β-dystroglycan, α-dystrobrevin and aquaporin 4 disappeared while that of utrophin and laminin appeared along the vessels, whereas α-syntrophin visualized the reactive astrocytes but not the resting ones. The aims of the present study were to investigate whether these post-lesion alterations: (i) are reproducible with immersive fixation, which is used in postmortem histology; (ii) are resistant to a postmortem delay before fixation; and (iii) are to be attributed to a direct effect of the lesion, or are mediated by processes occurring only in the living brain. Three models were investigated: (i) following lesions, some brains were fixed by transcardial perfusion, others by immersion; (ii) following lesions, the animals were decapitated and stored at room temperature for 8 or 16 h before fixation; and (iii) the lesions were performed after decapitation. Cryogenic lesions were performed by applying a dry ice cooled copper rod to the brain surface of ketamine-xylazine anesthetized rats. The immunohistochemical reactions were performed on free-floating sections cut with vibratome. Both immunoperoxidase and immunofluorescence methods were used. The fixation method - perfusive or immersive - did not change the post-lesion phenomena investigated. The postmortem delay did not influence the β-dystroglycan immunoreactivity, that is its lack delineated the area of the lesion. However, in the case of the other substances, various lengths of postmortem delay rendered the immunohistochemistry uninterpretable. The results suggest β-dystroglycan immunostaining could be applied in the neuropathology to detect cerebrovascular impairments.