Does a reduction in stem cells mean possible earlier death?

Question

The basis of this question relies on my understanding of these 2 facts:

1) A person has a certain number of stem cells from birth 
2) Stem cells are the basis of all cells and are used to repair and replenish

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I read an article about stem cells being found in fat removed by lipsuction and that the trials that has been done on using these stem cells for repair elsewhere in the body.

My question is, if stem cells are used for repair in the body and you have a certain amount of them, if you "lose" some via liposuction, does this then mean you have less stem cells and therefore less chance of repair and could then theoretically die sooner?

It's more than likely my lack of knowledge on the subject but I would like to understand why.

Answer 1

Stem cells persist because they have the capacity to self-renew. At birth you will have a finite number of each stem cell type (e.g. hematopoietic stem cells that make blood, gut epithelium stem cells that make gut lining etc). The general picture is that as tissues require replenishment, a stem cell divides. One daughter cell starts to differentiate (and divide) into mature cells required by the tissue, whereas the other daughter cell retains stem cell function.

So a stem cell is typically defined as a cell with the capacity to: (i) self-renew and (ii) to give rise to one or more cell types in a tissue. A hematopoietic stem cell can give rise to T-cells, B-cells, neutrophils, red blood cells, platelets etc. The ability to self-renew means that, in general, stem cells don't 'run out' during a lifetime.

[ Its important to note that to define a cell as a stem cell, scientists use strange hybrid of: in vitro or animal assays + cell surface markers + location in the tissue + measures of 'having the capacity to make continued contribution to new cells'. So lets just say that stem cells are only ever as well defined as our choice of assays combined with the interpretation of those results. ]

I mention the challenge of defining stem cells because, in recent years as assays and technologies improved, cells such a oocytes (eggs) or adult neurons, which were once thought to be finite, have been shown to have be replaced/renewed, presumably by some 'stem cell like' cell(s).

As noted above, stem cells are usually involved in the replenishment of a particular tissue type. So liposuction, which will remove fat cells, should not affect the numbers of hematopoietic or neural stem cells and so on.

Any claim of clinical benefit of a 'stem cell treatment' using liposuction should be backed by clear data.

A longer answer would get into: (i) the concept of 'plasticity' where the classical view - a fixed pathway between a stem cell giving rise to one daughter cell that gives rise to mature cells and the other returns to a stem cell state - is open for debate, and (ii) the idea that since stem cell definitions are only as good as our assays, there may be potential plasticity even among stem cells that we cannot 'detect' yet.

Answer 2

Death is caused by a variety of factors, our ability to heal is among them. However, it is possible to die from causes other than a deficiency in healing ability. Most people in the world die from cardiovascular disease and cancer.

The role of stem cells in the heart is an area of intense investigation. Vascular clogging is a more likely cause of cardiovascular failure than a disease of the heart muscle itself. In the case of clogged vessels, no biological mechanism exists to heal clogged arteries. Stem cells are irrelevant here.

Stem cells are most applicable to cancer in the immune system for the recognition of cancer cells. A decrease in actively dividing immune stem cells would correlate with an increased progression of cancer. This is exactly what happens with people undergoing chemotherapy. Chemotherapy kills actively dividing cells, including stem cells in the immune system. This is why they often suffer increased infections. It is rare to die from an infectious disease today. Decreased immune response from chemotherapy is a manageable side effect of treating cancer.

If you recreationally took chemotherapy drugs, this would inhibit the activity of stem cells. Your body would rapidly accumulate genetic mutations and systemic damage resulting in eventual death. This is why people coming in contact with individuals on chemotherapy should be careful not to touch any surface contaminated with the drugs. This especially applies to pregnant woman, where the danger is primarily with the fetus. In development, stem cells are vital in organ formation, not healing.

In different circumstances, to different individuals, during different life stages, destroying or preserving stem cells may be therapeutic, or devastating.

Answer 3

Theoretically, yes. Although, to my knowledge it has not been proven. As far as I'm aware there is no known link between liposuction and leukemia, liposuction would most likely not remove enough stem cells to produce such an effect. I've been doing a lot of research into stem cells lately and from what I have found there have not been many, if any, in depth studies on the impact of stem cell removal as the implantation of stem cells is usually the main focus.