The entering into the essence of biological aging begins with the
discovery of methods of cultivation epithelial and fibroblast cells of higher-
organism tissues, mainly of animal origin in the beginning (Carrel,
Burrows, 1911; Carrel, 1912). The obtained experimental data have
enabled A. Carrel to arrive at a conclusion that somatic cells do not
senescence in vitro and are able to unlimited reproducion (Carrel, 1912,
1913 a, b).
The interest in this problem still more increases after establishing the
limit to the number of divisions in normal (diploid) cells taken from human
tissues and developed in cell cultures (Swim, Parker, 1957; Hayflick,
Moorhead, 1961). In this respect great is the contribution of Leonard
Hayflick (1965), who for the first time makes an attempt to connect the
limited dividing ability of the cells from cell cultures (fibroblast) with the
process of aging.
In its review Hayflick (1989) notes that even in sequoias and bristlecone
pines in California and Nevada, with a life-span of several thousand years,
living cells can be found only in peripheral layer of the cambium and in the
needles not older than 30 years. The other cells are dead and continue to
exist due to the cambium, which is renovate constantly.
Of great importance are Hayflick’s findings leading to the conclusion that
cell cultures obtained from higher organisms (normal embryonic human cells)
have a limited replicative ability. They inevitably senescence and die after
approximately 50 doublings of the cell population, which he called
phenomenon of phase III. Besides, cells possess amazing “memory” and
they “remember” at which number of division have been stored even after
being kept for 27 years in liquid nitrogen (minus 180°C).
The above data raise an essential question: is it possible normal cells
of cell cultures, obtained from higher multicellular organisms and placed in
suitable conditions of development and division to avoid the aging and their
inevitable death? Or briefly speaking — can they avoid biological aging?
The answer of this question is closely related to the elucidation of
possibility such type of cells to be transformed into “immortal”, like the
independently existed unicellular organisms (bacteria, blue-green and
green microalgae, yeasts, etc.), which can reproduce without time limits, if
the conditions necessary for their existence are present.
Here, it is necessary to explain the meaning of “immortal”. This does
not mean that they exist several hundred or thousand years. On the
contrary, their life cycle is only several hours or days. The difference is that
they do not die, but from the mother cells through continuous division new
generations of daughter cells are obtained.
According to Hayflick at present there are thousands of “immortal” cell
lines. As well-known he has shown the L-cell line, isolated from mouse
tissues in 1940 and HeLa-line from human cells used in many laboratories
all over the world since 1951 up to now.