PERIVASCULAR EDEMA FLUID PATHWAY IN ASTROCYTIC TUMORS

Perivascular spaces are anatomical routes for the bulk flow drainage o f fluid from the gray matter to the subarachnoid space in normal rat b rain. Perivascular cells are the resident scavengers in perivascular s paces. Following focal brain damage, perivascular cells upregulate MHC Class II antigens associated with uptake of edema fluid. Similar cell s can be defined in damaged human brain. In the present investigation, the distribution of MHC Class II upregulated perivascular cells was m easured in 30 astrocytic tumors and adjacent edematous tissues by immu nocytochemistry using the following antibodies: HLA-DR (MHC Class II), PGM1 and MAC387 (macrophages). Perivascular cells were PGM1+/MAC387- and were located in perivascular spaces along blood vessels of all siz es. MHC Class II+ perivascular cells were distributed mainly in the tu mors but in some cases (4 of 10 in astrocytomas, 4 of 10 in anaplastic astrocytomas, and 7 of 10 in glioblastomas) they were also found in a djacent edematous brain. The extensive MHC Class II expression on peri vascular cells suggests that perivascular cells play a scavenging role in the perivascular spaces in human brain. The results of the present study indicate the similarity between perivascular spaces in human an d rat brains and emphasize the significance of perivascular spaces as anatomical routes for edema fluid drainage from human brain tissue.