Electron microscopic observations on human glioblastomas and astrocytomas maintained in organ culture systems.

The fine structure of four glioblastomas and two cerebellar astrocytomas maintained in organ culture systems up to 137 days and 43 days, respectively, using either a three-dimensional sponge foam matrix technic or a Millipore filter platform technic, is described and compared. The cells of both tumor types showed increased astrocytic differentiation, characterized by a progressive increase in glial filaments associated with an increase in free ribosomes and granular endoplasmic reticulum. A progressive increase in basement membrane material, presumably originating from explanted endothelial cells or pericytes, was also found in both tumor types and was often associated with increased numbers of collagen fibrils. Astrocytic tumor cell processes frequently preserved their contact with this basement membrane material. Microvascular fenestrations or gaps in endothelial cells were not identified. These electron microscopic features appear to correspond to the early stages of perivascular sclerosis previously noted by light microscopy in gliomas maintained in organ culture systems and are presumably related to the progressive obliteration of the functional microvasculature.