The Dependence of the Embryonic Inductive Action of HeLa Cells on Their Growth Media Available to Purchase

HeLa cells which had been cultured in various growth media were used as implantation material in induction experiments, the object of which was to find out to what extent the inductive capacity of the cells is dependent on the media.

1. HeLa cells grown in untreated (‘active’) pooled human serum proved to be strong deuterencephalic-spinocaudal inductors. The inductive capacity was the same in cells grown in different pooled sera.

2. Heating of cells grown in active serum for 30 minutes at 56° C. did not influence their inductive capacity. By contrast, heating for 30 minutes at 65° C. completely destroyed the deuterencephalic and spinocaudal inductive effects, but subsequently the cells still induced archencephalic structures.

3. Continuous cultivation in serum heated at 56° C. almost completely destroyed the spinocaudal inductive effect of the cells. Simultaneously, the archencephalic effect was strengthened. Cultivation under the same conditions for a short time (3 days) caused a similar, though slighter, change. When some of the cells continuously grown in heat-inactivated serum were returned for 3 days to active serum, their inductive capacity was found to be almost the same as that of cells continuously grown in active serum.

4. Cultivation in serum heated for 30 minutes at 65°C. markedly weakened the spinocaudal inductive capacity of the cells, although the latter still grew normally. Even after cultivation for 14 days this weakening was clearly observable, and at the same time there was an increase in the number of archen-cephalic structures. After 28 days’ cultivation the cells exhibited the same inductive effect as cells continuously grown in serum inactivated at 56°C.

5. Cultivation in serum-free Parker’s 199 solution rapidly weakened the spinocaudal inductive capacity of the cells, but the latter were not capable of growing continuously in this solution.

6. The conclusion is drawn that, in accordance with the gradient theory previously advanced by the authors, the change in inductive capacity may be explained as a weakening of the mesodermalizing (M) principle in the cells, whilst the neuralizing (N) principle remains the same. A result of this change in the N/M balance would be that the spinocaudal action is weakened and the archencephalic effect is strengthened. At the same time the results show that the mesodermalizing action of the cells is dependent on external factors, whilst the neuralizing principle seems to be more stable. The results are compared with previous investigations on the changes in the inductive capacity of tissues caused by starvation, rapid growth, and malignancy.