Morphometry of GFA and vimentin positive astrocytes in grafted and lesioned cortex cerebri

The presence and morphology of GFA- and vimentin-positive astrocytes were studied immunohistochemically in rats using smear preparations of single intraocular grafts of the cortex cerebri anlage and of cortex pieces grafted to eyes containing a previously grafted piece of the locus coeruleus area. Similarly, astrocytes were studied in lesioned cortex cerebri in situ. A high number of GFA and vimentin-positive cells were found in smears of both types of cortex grafts as well as in smears of the lesioned cortex cerebri in situ. In contrast, only a limited number of GFA-positive astrocytes were seen in smears of normal cortex. Using computerized image analysis, the two-dimensional cell area and cell perimeter were found to be significantly increased in individual GFA-positive astrocytes in both types of intraocular cortex grafts as well as in the lesioned cortex when compared to GFA-positive astrocytes in normal cortex cerebri. GFA-positive cells in smears of cortex grafts from locus coeruleus-cortex combinations had significantly smaller cell area and cell perimeter values compared to similar cells from single cortex grafts. A similar, although less pronounced difference was observed between vimentin-positive cells from the same type of grafts. This suggests that the presence of the mature locus coeruleus graft in some as yet unknown way influences the development of the adjacent cortex graft towards a more normal astrocytic maturation. An additional finding was the large size difference between GFA- and vimentin-positive cells in the intraocular grafts. Since most evidence indicates that vimentin-positive cells are also GFA-positive, this may indicate that the two intermediate filament systems have a partially different distribution within individual astrocytes. It is concluded that computerized image analysis of smears processed for immunohistochemistry with antisera against GFA and vimentin is a useful technique for studies of astrocyte morphology in normal as well as experimentally perturbed CNS tissue. Cortex tissue that develops in contact with a locus coeruleus graft in the eye chamber show a significantly lesser degree of gliosis than cortex tissue developing in isolation in the eye.