The rat neuroblastoma B104 cell line, which originated in the central nervous system, was able to proliferate in the absence of serum in synthetic medium supplemented with insulin, transferrin, progesterone, selenium, and putrescine. When added individually, each supplement had little or no effect; however, in combination there was a marked synergistic effect on cell number. The cells attained the same saturation density in this medium as in medium with 10% fetal calf serum added. More extensive process formation was observed in the supplemented medium, and other differentiated properties were retained as well. Synthetic media generally require serum supplementation to support the proliferation or survival of cultured cells. The inclusion of serum, however, may significantly affect experimental reproducibility, because batch variations occur as a result of differences in donor age, sex, nutrition, and physiological state even in pooled serum samples. In addition, the complex undefined nature of serum is a complication when assessing the effect(s) of regulatory agents, such as hormones or neurotransmitters, on differentiated properties of nervous system cells in culture. This is particularly important for long-term studies, because if serum is deleted a substantial reduction of cell numbers, and in many cases complete cell death, may occur within hours or a few days.In order to circumvent these problems, several cell lines have been adapted to proliferate in serum-free media (1-4). How The B104 rat neuroblastoma, a cell line of central nervous system origin, exhibits many of the properties characteristic of differentiated neurons, such as generation of action potentials, synthesis of neurotransmitters, and presence of neurotransmitter receptors and the neuron-specific 14-3-2 protein (9, 10). Furthermore, B104 cells, like C1300 neuroblastoma cells (11, 12), respond to removal of serum by rapidly extending neurites, a phenomenon that has been correlated with the preceding neuronal properties (9).In this communication we report that B104 cells can proliferate in a serum-free synthetic medium supplemented with insulin, transferrin, progesterone, selenium, and putrescine (N2 medium). More extensive process formation is seen in N2 than in serum-supplemented medium, and other differentiated properties have been retained as well.
METHODS AND MATERIALSCell Culture. The rat neuroblastoma B104 cell line was obtained from D. Schubert of the Salk Institute, La Jolla, CA. Stock cultures were maintained in a 1:1 mixture of Ham's F12 medium and the Dulbecco-Vogt modification of Eagle's medium (DME) supplemented with 5% (vol/vol) horse serum; 2.5% (vol/vol) fetal calf serum; 1.2 g of NaHCO3 per liter; 15 mM Hepes buffer; and 40 mg of penicillin, 8 mg of ampicillin, and 90 mg of streptomycin per liter. Triple-distilled water was used to prepare media. Stock cultures were grown in flasks (Falcon Plastics 3013, 25-cm2 surface area) in 4 ml of medium in a humidified atmosphere of 5% C02/95% air at 370C and subcultured every ...