Dynamic patterns of USPIO enhancement can be observed in macrophages afterischemic brain damage

Cells of the mononuclear phagocytotic system (MPS) are often found near to or within ischemic tissue and can potentially aggravate cellular damage. He nce, visualization of those cells would allow demarcation of putatively aff ected from intact tissue. Experimental MR1 studies have shown that ultrasma ll particles of dextran-coated iron oxide (USPIO) are internalized into cel ls of the MPS. To test if this cell tagging method may be also applied to c erebral infarction, USPIOs were administered to Fisher rats 5.5 h after per manent occlusion of the middle cerebral artery (pMCAO). During the first 2 days USPIO were preferentially found in patches within the lesion and in su rrounding areas. On day 4, USPIOs expanded within the core of the lesion. O n day 7 they were found predominantly within the boundary area. Histologica l analysis showed large populations of macrophages containing iron particle s in the infarcted tissue. We conclude, therefore, that it is possible to m onitor MPS activity after focal cerebral ischemia using USPIOs. (C) 2001 Wi ley-Liss, Inc.