Isolation of mesenchymal stem-like cells in meningioma specimens.

Cells resembling bone marrow mesenchymal stem cells (BM-MSCs) have been isolated from glioma specimens; however, little is known about the existence of mesenchymal stem-like cells (MSLCs) in meningioma. Here, we hypothesized that cells similar to BM-MSCs exist in meningioma specimens and sought to investigate whether these putative meningioma stroma MSLCs (MS-MSLCs) could be isolated. To this end, we cultured fresh meningioma specimens using the same protocols as used previously to isolate BM-MSC. Cultured cells were analyzed for surface markers associated with BM-MSCs by fluorescence-activated cell sorting (FACS) and candidate cells were exposed to mesenchymal differentiation conditions. Possible locations of MS-MSLCs were determined by immunohistochemical analysis of sections of meningioma specimens. Spindle-shaped and, adherent cells similar to BM-MSCs were isolated in 2 of 20 meningioma specimens. FACS analysis showed that the surface markers of MS-MSLCs were similar to those of BM-MSCs and the chosen cells demonstrated an ability to differentiate into osteogenic, adipogenic and chondrogenic cells. The tumorigenicity of MS-MSLCs was tested by injection of these cells into the brain of athymic nude mice; no tumors were subsequently discovered. Immunohistochemical analyses indicated that CD105+ cells were closely associated with endothelial cells and pericytes in meningioma specimens. Our results established for the first time that cells similar to BM-MSCs exist in meningioma specimens. These cells, termed MS-MSLCs, could be one component of the meningioma cellular microenvironment.