Macrophage infiltration and heme oxygenase-1 expression correlate with angiogenesis in human gliomas

Macrophages are key participants in angiogenesis. In this study an human br ain tumors, we first investigated whether macrophage infiltration is associ ated with angiogenesis and malignant histological appearance. Immunostainin g of macrophages and small vessels in resected glioma specimens indicated t hat numbers of infiltrating macrophages and small vessel density were highe r in glioblastomas than in astrocytomas or anaplastic astrocytomas. Macroph age infiltration was closely correlated with vascular density in human glio mas, Heme oxygenase-l (HO-1), which is the rate-limiting enzyme in heme cat abolism, was also associated with activated macrophages, Expression of mRNA encoding HO-I was correlated with macrophage infiltration and vascular den sity in human glioma samples. Infiltrating macrophages were positively stai ned with anti-HO-1 antibody by immunohistochemical analysis, and irt situ h ybridization for HO-I indicated that HO-1 was expressed in infiltrating mac rophages in gliomas, HO-I gene may be a useful marker for macrophage infilt ration as well as neovascularization in human gliomas.