Ultrastructural analysis of brain tumors using collagen gel culture

In an attempt to investigate the tumor type-specific ultrastructure of cultured brain tumors, a collagen gel culture was utilized instead of the conventional monolayer culture. To avoid intermingling of the normal brain cells, tumors with a clear margin and a portion typical of invasive tumors were sampled. The tumors were minced, and small fragments were prepared and embedded in the collagen gel in an aseptic manner. Tumors were observed on a daily basis under a phase contrast microscope. When sprouting of the tumor cells from a tumor fragment was confirmed, the samples were fixed with 2.5% glutaraldehyde and then processed for electron microscopy. Ultrastructurally, meningioma has been shown to form a whorl-like structure. The cell processes have a complex interrelationship, but this phenomenon cannot be regarded as the so-called interdigitation. A basement membrane was formed surrounding the tumor cell processes facing the collagen gel in two ependymomas. Lipid droplets were contained in great numbers inside a chordoma cell. These findings suggest the usefulness of collagen gel culture in analyzing the tumor type-specific ultrastructure of cultured brain tumors, and possibly in studying cellular differentiation.