A total of 7 experimentally induced nervous system tumors, which had been kept up by serial subcutaneous transplantation or by tissue culture, were studied in cultures with Gelfoam used as a substrate. Three of 7 tumors examined were MNU (methylnitrosourea) -induced rat nerve tumors, 1 was MC (methylcholanthrene) -induced mouse glioma and 3 were Ad-12 (Adenovirus type 12) -induced rat brain tumors.
Of 7 tumors 5 examples were maintained in vitro for more than one week and 3 of them were succesfully maintained for 30 to 60 days. The original tumors and the cultures were observed in light and electron microscopy, and studied by PAP immunoperoxidase method for GFA and S-100 proteins.
An experimental nerve tumor induced in rat by MNU was maintained in vitro up to 40 days. The original tumor was made up of fibroblast-like spindle-shaped cells and the ultrastructure was characterised by the presence of well-developed granular endoplasmic reticulums. After 33 days in vitro, the explants demonstrated numerous micropinocytotic vesicles, increase of microtubules, devolopment of incomplete basement membrane and occasional junctional apparatus, which were characteristic of perineurial sheath cells. The production of S-100 protein was detected in cultured cells.
An experimental glioma induced in mouse by MC was maintained on Gelfoam up to 65 days. The original tumor was composed of polygonal cells of undifferentiated appearance which stained positive for S-100 protein. After 22 days in vitro, the production of a large number of virus-like particles were seen by EM with some budding configuration. Those found in extracellular space, which measured 100-130mμ in diameter, containing an electron dense core, appeared to be of type C virus particle, whereas those in cisterns of granular endoplasmic reticulum were dougnut-shaped, and measured 80-90mμ in diameter, rasembling intracisternal type A virus particle. It seems that this observation represents an elevated indigenous virus activity in organ culture environment. An increase in number of cytoplasmic filaments measuring 4-9 mμ in diameter was demonstrated in some cultured cells after 30 to 55 days in vitro. It is considered that these filaments represent so-called “stress fibers” which are known to occur in a broad spectrum of cell types in older culures, since GFA protein remained negative throughout the period of cultivation.
Viable cultures up to 40 days were obtained from 1 of 3 Ad-12 induced rat brain tumors. Active penetration of undifferentiated tumor cells into the supporting matrix was able to be observed. Cellular differentiation toward glial or neuronal cell, however, was not evidenced by EM at any stage of cultivation.
The present findings indicate the Gelfoam organ culture method is of advantage for the study of experimental nervous system neoplasms, because it permits the reproduction of original in vivo tissue organization and cellular features, and because in some examples it favors morphological differentiation.
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