Are Stem Cells Really Immortal Cells?

*Logical Biology* 6 (4): 71-75, 2006	MINI-REVIEW
http://logibio.com
© Truthfinding Cyberpress (http://im1.biz/tfcp)	STEM CELL IMMORTALITY

Are Stem Cells Really Immortal Cells?

Shi V. Liu

Eagle Institute of Molecular Medicine

Apex, NC 27502, USA

SVL@logibio.com

(Received 2006-08-15; accepted 2006-10-02; published 2006-10-07)

HIGHLIGHT

Stem cells are believed to be immortal. However, literature evaluation suggests this conventional wisdom may be wrong. In contrast, increasing scientific evidence and logical reasoning on objective observations suggest that stem cells are mortal, just like any other cells.

ABSTRACT

Stem cells have been described as immortal cells. However, careful literature analysis and logical reasoning have led to a conclusion that this conventional wisdom may be wrong. The root of this misconception on stem cell may be traced back to the fundamental ancestral mistakes in microbiology when microbiologists incorrectly miss-identified the mother cell still lives after its cell reproduction as a “daughter” cell. This misunderstanding of cell life can be reflected with the labeling of the continued existence of the mother stem cell as a “self-renewal” – formation of another “daughter” cell resembling its mother cell. Attaching observations on asymmetric cell division and the regular distribution of template DNA stand into one of the two cells formed from one cell to the so-called “immortal DNA stand” hypothesis is logically wrong and scientifically incorrect. Instead one should consider the retention of the template DNA strand within one cell as a strong argument for naming this cell as the mother cell and clearly distinguish it from the true daughter cell which receives a copied new strand of DNA. Under no circumstance this biotic reality implies any immortality for the DNA strand or the cell receiving this DNA strand. It is more likely the old template DNA strand is actually a most liable DNA strand due to its aging status. To conclusively prove whether the traditional view or the new concept is right scientific experiments based on truly single cell-level tracking or population study using bona fide chronological age-synchronized cells are necessary.

KEY WORDS

Stem cell, Immortality, Self-renewal, Cell death, Cell reproduction, Cell aging, Age synchronization, Mother-daughter relation

Stem cells are the hottest cells for biomedical research now. One great selling feature claimed for stem cells are their so-called “immortality”. Publications on “immortal stem cell” are so many that not only serious research articles are easy to be found in reputable scientific database (at least 167 titles were found in the PubMed searched on August 13, 2006) ^1-11 but also many popular books are printed out ^12-17. Entering “immortal stem cell” for a search in Google 436000 links were found. At the research conference on aging the overwhelming topics were not why organisms die but how some cells are immortal and can be used for extending the life span of organisms. Believe it or not, the magic medicine that scientists have found to confront aging and mortality is the “immortal” stem cells.

However, are stem cells really immortal?

First I must confess that I am not a stem cell researcher. However, I am not unfamiliar with stem cell research and the “immortality” claims on stem cell because I have stalked this area of research as a side spare time interest for over 15 years. As a microbiologist, I have also been dealing with another kind of the so-called “immortal” cells – unicellular microbes – for over two decades. What I have found is that even these long-believed “prototype” “immortal” cells are truly mortal ^18-20.

In comparing stem cell research with microbiological research, I have found the striking similarity in the logical fallacy and methodological mistakes between these separate but closely related scientific disciplines ^21-26. I also realized a key fact, despite so long and/or so intensive research in these fields ²⁷, no one has actually observed the complete life span of any cell (being it a microbe or a stem tissue cell) ²².

Then why microbiologists then and stem cell biologists now claim the immortality for their not well-studied cells? Well, if it is not for their lack of true knowledge on cells, it may be for the attraction of the commercialism because immortality sells and no one wishes to die.

However, science is about the truth reflecting reality, not just for fulfilling the human wishes. So placing stem cell “immortality” under the scrutiny of a scientific microscope, let’s examine what evidences there are for supporting such an unusual claim.

A major claim for the “immortality” feature of the stem cell is their capability of the so-called “self-renewal” ^28-30. However, this so-called stemness feature of stem cells may in fact be a misunderstanding of cell due to a fundamental mistake in cell biology that is actually inherited from the same mistakes occurred in the early stage of microbiology.

Microbiologists have long-believed and (at least most) still believe that one mother microbe divides into two daughter microbes ^{31, 32}. However, this conclusion is not only logically wrong but also scientifically incorrect ^{21, 22, 24, 25, 33-36}. The alternative view that one mother microbe reproduces another microbe while itself still alive ¹⁸ in fact not only fit diverse microbiological observations better but also conform with general biological principles that had been verified with direct observations on many forms of macrobial lives ^37-41.

With the same arguments against traditional microbiological mistakes it can be argued that the so-called “symmetric” cell division really does not occur in the sense of the genuine age difference existed between any paired cells formed from one cell ^{26, 34}. Stem cells, with their cardinal feature of capable of reproducing daughter cells with different features (due to a true sense cell differentiation), actually provided some perfect examples for supporting this chronological age difference.

Now the question is what evidences there are for making a convincing claim for the mother-daughter relationship between two cells formed from one cell?

It turn out evidences are already there in the literature.

First, it has been observed long-time ago that some cells (many of them are now recognized also as stem cells) have the capacity to retail some labels in their DNA strand ^42-51. These so-called “label-retaining cells” (LRC) demonstrated that the life span of cells can be longer than the length of a “cell cycle” (reproduction cycle). Thus, the equation of cell cycle with life cycle is deadly wrong as was the case in microbiology. From this understanding, it is also logical to say that the LRCs are actually the original mother cells, not any kind of “renewed” daughter cells with mother-like features.

Secondly, the so-called “immortal” DNA strand ⁵² in fact merely represents the template DNA strand which is retained by the mother cell after it has repeatedly reproduced daughter cells in successive rounds of reproductions. The regularity of retaining of template strand DNA in one cell and the distribution of copied DNA strand into another cell of the paired cells formed from one cell demonstrated that the paired cells are exactly mother cell (containing DNA formed on generation earlier) and daughter cell (receiving DNA formed in the new generation time) ^{53, 54}.

Many stem cell biologists ^2-4 claim that their cell immortality claim is backed by the DNA immortality hypothesis ⁵². However, my careful evaluation of the “immortality DNA” hypothesis revealed that the immortality claim for immortal DNA strand is first a logical confusion and then a scientific mistake. The regular segregation of DNA strands and, particularly, the invariable distribution (should be more precisely called retention) of template DNA strand in one “daughter” (should be the mother) cell has noting to do with the “immortality” of this DNA strand. In my view this so-called “immortal” DNA strand may be the most vulnerable DNA strand in the DNA family since it is the chronologically old DNA strands in the chronologically old cells.

To prove that my mortality claim for cell (not just stem cell but all types of cell) and its contained DNA are wrong or to prove that the immortality of cell (stem cell at least) are correct one should at least follow the whole life span of the cell. In this regard, I challenge cell biologists (which include stem cell biologists and microbiologists) to spent some time to do some real single-cell tracking experiments ³⁷. Alternatively, some population type cell studies can be performed with truly chronologically age-synchronized cells ^{19, 20, 25, 41}. A method and apparatus for obtaining bona fide age-synchronized cell population has been invented and patented for public use ²³.

With those kinds of truly scientific experiments I guess there would be no more debate on the immortality issue of cells because the facts would speak out by themselves.

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