Ageing and the fusion sensitivity potential of human cells in culture: relation to tissue origin, donor age, and in vitro culture level and condition.

Cell fusion was induced by inactivated Sendai virus in different human diploid cell lines. These were derived from the kidney, lung or skin originating from embryos or adult donors and representing predominantly epithelioid cells (kidney) and fibroblastic cells (lung and skin). The fusion sensitivity (FS) potentials of these cell lines were determined and related to various aspects of cell ageing. In case of the fibroblastic lines, an inverse relation was demonstrated both to the culture age in vitro and to the donor age. The FS potential of embryonal fibroblasts decreased some 40-50% during the in vitro cultivation. In comparison to exponentially growing fibroblasts, the FS potentials were higher in cells in the stationary phase of growth. This was shown to correlate well with the fact that the life-span in calendar time also increased in cultures predominantly grown in the stationary phase. In the case of the kidney cells, the FS potentials were some 50% higher than those of fibroblasts. Since the cellular manifestation of the FS potential most likely primarily resides in the cell membrane-cytoskeleton structure, the results emphasize the importance of this system in relation to ageing.