Relationship of Invasiveness to Proliferating Activity and to Cytoskeletal Protein Production in Human Neuroepithelial Tumors Maintained in an Organ Culture System: Use of Human Cortex and Dura as Supporting Matrices

The proliferation and invasiveness of cultured human neuroepithelial tumors were studied. A human malignant astrocytic glioma cell line (U-251 MG) and a medulloblastoma cell line (D283 Med) were maintained for 3 weeks in an organ culture system using adult human brain cortex, dura mater, or Gelfoam sponge as growth matrices. The cells were labeled with bromodeoxyuridine (BrdU) at different time points, and immunohistochemistry was performed for BrdU, glial fibrillary acidic (GFA) protein (in U-251 MG), and neurofilament (NF) protein (in D283 Med). In the U251 MG line, the cells grew successfully in each matrix, forming a fibrillated solid area and a peripheral zone of invasion. The labeling index (LI) expressed as the percentage of BrdU-labeled cells and the percentage of GFA protein-positive cells in the two zones of the explants were analyzed. The LIs in all cultures were significantly higher in the peripheral than in the central zones. On the other hand, the percentage of GFA protein-positive cells in each matrix was greater in the central zone than in the periphery. The LI was inversely correlated with the percentage of GFA protein-positive cells over the areas counted in each growth matrix. GFA protein production in cells grown on cortex and on dura mater was significantly higher than that in cells grown on Gelfoam. In the D283 Med line, the cells formed an aggregated zone, with peripheral cells infiltrating the Gelfoam. This line showed poor growth on human cortex. Cells grown on the dura demonstrated an LI similar to that on Gelfoam, and cells often infiltrated the dura. The LI of these cells was higher in the peripheral than in the central zone of the explants, both on dura and on Gelfoam. The cells showed variable immunopositivity for each NF protein subunit. No apparent difference in the percentage of immunopositive cells for each NF protein subunit was detected between cells grown on dura and on Gelfoam; however, cells grown on dura often demonstrated neurite-like processes. The results indicate that an organ culture system using human brain cortex or dura mater as matrices for in vitro growth is a promising tool for the study of neuroglial differentiation and of the invasiveness of cultured human neuroepithelial tumors.