A light and electron microscopical study of the nervous tissue of mouse teratomas

Well-formed cerebellum and brainstem-like structures in a mature ovarian teratoma: Neuropathological observations

In the surgical case of a mature cystic teratoma of the ovary that arose in a 16-year-old girl, a large amount of well-differentiated and highly organized cerebellar tissue was found. Three layers of the cerebellar cortex were well formed, and synaptophysin-positive "glomeruli" were found in the granule cell layer. Some Purkinje cells exhibited focal expansion and a dysmorphic appearance of the dendrites. Adjacent to the cerebellar tissue, a large space lined by the ependymal layer and a club-shaped CNS tissue mass resembling the brainstem were found, and structures reminiscent of the midbrain tectum and pontine nuclei were distinguished within this mass. The CNS tissue was surrounded by the leptomeninges and a skull-like, bony shell. Structures consistent with the supra-tentorial CNS tissue were not found. This case represents an example of infra-tentorial CNS tissue that was well-differentiated and organized to an exceptionally high degree in an ovarian mature teratoma. Various degenerative changes have been documented in CNS tissue in ovarian teratomas, but the dendritic abnormalities of Purkinje cells seen in the present case are novel findings.

The ultrastructure of the nervous tissue in a benign teratoma

The ultrastructure of the nervous tissue in a benign ovarian teratoma is described. This tissue was organized into areas having both "meningeal" and "ependymal" surfaces, between which were found astrocytes, ependymal cells, neurones with synapses and microglia. These cells all had ultrastructural similarities to their normal counterparts in the nervous system. In addition, some signs of degenerative change--due possibly to the abnormal location of the nervous tissue--were observed. Oligodendrocytes and myelin were absent, possibly because of vascular insufficiency.

Microglia in teratomas

Using an ammoniacal silver nitrate stain, we have demonstrated typical microglial cells in three teratomas. Microglia appeared identical to their counterparts in the mature human brain, both resting and slightly hypertrophic types being present in differentiated nervous tissue, which also comprised astrocytes, neurones and ependyma. The implications of the presence of microglia with ectodermal derivatives in teratomas are discussed.

Neural differentiation in the OTT-6050 mouse teratoma. Production of a tumor fraction restricted to stem cells and neural cells after centrifugal elutriation

Dissociation and centrifugal elutriation procedures were applied to subcutaneous transplants of the OTT-6050 mouse teratoma line in order to enrich the neuroepithelial cells. One of the resultant cell fractions, designated IB-21, was then implanted beneath the renal capsule of syngeneic mice and rebanked every 3 to 6 weeks for a total of 58 passages over 5 years. Sequential passages resulted in a tumor restricted to stem cells and neural cells (neuroblasts and glial cells). The primitive neural cells lost the ability to form rosettes after the early transplants. Subcutaneous or intracerebral transplantation of these tumors evinced their capacity for further neuroepithelial differentiation, with the demonstration of astrocytes and occasional mature synapse-forming neurons. Conversion of the tumor to the ascitic form resulted in unorganized clusters of neoplastic cells in contrast to the highly structured embryoid bodies that are characteristic of the parent Ott-6050 line. The absence of non-neural cells in the IB-21 tumor fraction and its ability to demonstrate divergent neural differentiation suggest that a transplantable neural-determined cell population exists in the OTT-6050 mouse teratoma.

Formation of "neo-cortex" in a congenital human teratoma

A congenital human teratoma contained a neuroectodermal mass with architectonic features similar to those of the normal developing neo-cortex. Surrounding a central cavity, a germinal, an intermediate and a cortical zone were clearly distinguishable from innermost to outermost. Glial fibers coursed radially through the intermediate and cortical zones. In the "cortical plate" neuronal elements were oriented radially with an inside out gradient of differentiation. Mesothelial tissue covered the outer surfaces of the "cortex". Over limited sectors a gap in the integrity of the meso-glial barrier were associated with neuroglial ectopias. The following points are of neurobiologic importance: the information of the "miniature cerebral cortex" occurred in the absence of any influence of afferent subcortical fibers. The radial alignment of glial fibers between the germinal pseudostratified epithelium and the outer surface occurred only in sectors of the neuroectodermal mass where a "neo-cortex" was present, and may therefore have been a critical determinant in the formation of the "cortical plate". The integrity of the outer glial mesenchymal barrier may be necessary for the normal arrangement of cortical neurons.

Biochemical markers of the progress of differentiation in cloned teratocarcinoma cell lines

The progeny of single teratocarcinoma cells will give rise to several different cell types in vitro, and the latter were shown to be functionally differentiated by biochemical criteria. In all these studies, cloned lines of mouse teratocarcinoma cells were assayed during the course of differentiation for some biochemical products characteristic of the tissues formed. The carcinoembryonic protein, alpha-foetoprotein, was not synthesized by undifferentiated embryonal carcinoma (EC) cells, but was synthesized in increasing amounts during their differentiation to endoderm-type cells in suspension culture. alpha-Foetoprotein was shown to be a product of endoderm cells, but not all endoderm cells synthesized this protein. During the course of further differentiation when EC cells or aggregates were grown in tissue-culture dishes, other biochemical products appeared. In cultures containing predominantly nerve-type cells, there was a 30-fold increase in the specific activity of acetylcholinesterase, with concomitant appearance of the aldolase isoenzyme characteristic of mouse brain. In some cultures, a small amount of muscle-type cell formation was marked by the appearance of the MB isoenzyme of creatine phosphokinase. Generally, biochemical differentiation was immature.

Brain-associated cell surface antigens on neuroepithelial cells in a transplantable mouse teratoma

Mouse neonatal brain cell fractions enriched for surface membranes were used as immunogens to produce a heterologous immune serum. Following absorption to remove non-neural anti-mouse activity, this serum demonstrated by microcomplement fixation an anti-brain activity that was completely removed by absorption with neonatal mouse brain or with solid tumors of the mouse transplantable teratoma OTT-6050. Indirect immunofluorescence applied to living monolayer cultures of differentiating teratoma embryoid bodies showed the absorbed serum's reaction with neural cell surfaces only. In material studied with frozen sections, the absorbed serum recognized antigenic sites in all examined areas of both neonatal and adult mouse brain, and only within neuroepithelial cell populations of solid transplants of the teratoma.