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Organism Differentiation Level, Stem Cell Depletion and Aging - Short Aging Hypothesis
Posted on: October 18, 2004

Aging is a disease. Evolutionary aging became as a natural process. Nevertheless, there are still found some organisms that overcome aging process. Some of them are protozoa. Mainly all of their cells are stem cells capable to regenerate any part of the body. Mammals are similar organisms that differ in differentiated cell number, size, hormonal regulation etc. So, what could be the answer why so different organisms as protozoa are immortal and higher differentiation level organisms end their lives by dieing from age onset? Protozoa are characterized by very low number of differentiated cells. Not each but many of the cells in their body are totipotent or at least multipotent. This means that differentiation level here is the lowest ever seen in living multicellular species. Maybe because of this reason protozoa are theoretically immortal. What is the situation with higher organisms, i.e. mammals? They have some basic points with protozoa: stem cells, regeneration capacity of some but not all organs, expose strict hormonal regulation, nevertheless they are born, mature, age and dye. Is there any key to aging process shift to immortalization in higher organisms? Overall, this is possible to overcome aging process in higher mammals but at first, we should answer the question what is the main key and the role player in our aging bodies.

Fig. 1. Hypothesized organism aging process due to stem cell pool eradication.

Graph (Fig.1.) shows theoretical view of processes in aging body. Body differentiation degree rises during maturation process and basic protein regulatory factors consumption, by differentiated cells, increases. Because of this, stem cells are not supplied with enough factors required to maintain asymmetrical division as they are already consumed by differentiated cells. Organism posses the same need in stem cells. Symmetric division of stem cells begins by causing the ablation of default pool. As stem cells are consumed to maintain whole body healthy and normal the decrease of stem cell stock is case dependent, that is why people posses different numbers of stem cells at the same ages and they age differentially. At the time point when major part of stem cell pool is already consumed the latter part of stem cells could be kept in asymmetrical division. This could happen by relative increase of basic protein factors comparing to the number of stem cells left. At this time, point general number of consumers (stem cells) is relatively low. The amount of factors is quite enough to assure asymmetrical stem cell division. This is required, because critical stem cell pool should exist.

One of the evidence for this hypothesis could be bone marrow. What happens when stem cells are ameliorated from the bone marrow? Bone marrow is shifted with adipose tissue. In this way latter are protected from the expansion of new stem cells. In such a way organism protects itself from possible rejuvenation- stem cell expansion, what could be critical for evolution. Evolutionary laws of nature tell – elders must give their place to younger ones there is no need to give all the best to elderly. Differentially from nature laws we have social drive. Elder is smarter than younger one, and intellectual property overcome physical state. This is the drive of progress, social progress. Nature is not interested in.

Of course, it is quite daring to compare protozoa and mammals, but let's just make presumption that these organisms show some critical basic points for us to compare. This hypothesis is based only on stem cells and proteins, which are required for cell asymmetrical division ensure and their consumption by other cells. As we all know aging is a complex process, many other factors here are not mentioned and analyzed. This is just hypothesis connecting stem cells and proteins.

Adas Darinskas

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