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Using stem to treat injuries, diseases

Dr Derrick Aarons

Sunday, October 14, 2018

EXCITEMENT has continued around the promise of stem cells to treat a wide range of injuries and diseases.

Stem cells are 'undifferentiated' cells of an organism that are capable of giving rise to indefinitely more of the same cell type, as well as differentiating into other types of cells that the body needs in its development.

Their excellent promise over the last two decades has meant guaranteed press coverage and probable approval for research to occur on stem cells. Importantly, stem cells are pluripotential in nature, meaning they have the ability to grow into any type of body tissue, such as muscles, nerves, bones, cartilage, brain, kidneys, and so on.

Stem cells may be obtained from embryos (embryonic stem cells) or from the umbilical cord at delivery. They may also be obtained from fat tissue in adults (adult stem cells). These cells are already being used in the treatment of certain diseases of the blood such as leukemia, as well as in multiple sclerosis and in degenerative problems in the bone and cartilage.

Regenerative medicine

Mesenchymal stem cells are examples of adult stem cells and are regarded as being 'multipotent', meaning they have multiple potential but are not as diverse in their abilities as 'pluripotential' stem cells, which have the ability to differentiate into any type of cell tissue within the body.

The mesenchymal adult stem cells are, therefore, regarded as having use in the possible regeneration of damaged body tissue; tissues such as bones, cartilage, fat, muscle, and tendons that normally give our bodies strength and structure.

These cells are also viewed as potentially having healing properties that can reverse damage to diseased organs, for example in arthritis and following organ transplantation.

The regenerative potential of mesenchymal stem cells have been studied since the late 1960s. In one of the earliest experiments, Alexander Friedenstein and research colleagues showed that transplanting bone marrow into a different site of the body led to bone formation, which indicated that at least some cells within the bone marrow are able to change into bone cells, even in locations where bone was not expected to grow.

Consequently, there is much hope that adult stem cells may be used to treat serious chronic diseases such as diabetes, colitis, arthritis, liver disease, kidney disease, heart disease, and chronic obstructive pulmonary disease.

In fact, there are more than 700 research clinical trials registered at clinicaltrials.gov in the USA, that are being conducted on mesenchymal stem cells.

Embryonic stem cells

On the other hand, research on or use of embryonic stem cells have invoked moral indignation in some people, as they regard the fertilised egg of a woman as a human being, and therefore deserving of special protection on moral and religious grounds.

As the fertilised egg multiplies and grows into an embryo at six to seven weeks, extracting stem cells from those embryos and leaving the remaining tissue to die would be akin to abortion, they claim.

However, some countries do not have this moral or religious perspective, and so it was not surprising to many that China announced recently that it had begun research on embryonic stem cells with the intention to treat Parkinson's disease and macular degeneration in the eye. Prior to this, China had implemented new stem cell regulations which allow research for such purposes in 2015.

The research seeks to test the efficacy of injecting embryonic stem cells into damaged areas of the brain and eyes. Parkinson's disease is characterised by the reduction of dopamine in the brain, a substance (neurotransmitter) needed to facilitate nerve impulse activity between brain cells.

So, in one research trial, the stem cells will be injected into the areas of the brain affected by Parkinson's disease in an attempt to regenerate dopamine-producing tissue.

In another research trial, the stem cells will be injected into the eyes of people with age-related macular degeneration. It is believed that the stem cells may be able to replace retinal cells damaged as a result of the degeneration of epithelial tissue. A central government committee in China, which included a stem cell scientist from the Beijing Institute of Transfusion Medicine, approved the research trial.

Unanswered questions

However, there are still many unanswered questions surrounding the use of stem cells. To what extent may they provide benefit without causing harm?

Mesenchymal adult stem cells have the potential to transform into cells that we do not want, such as scar-forming cells known as myofibroblasts. Scar formation can occur to such an extent that it affects normal organ functioning.

How many stem cells need to be injected in a person in order to produce the desired effects? How long will the cells stay around in the injured tissue to do the job?

Answers to questions such as these will be needed before we can safely use stem cells treatments. Until then, we should not use stem cells for treatment, but rather for research to find answers that will enable the safe use of stem cells as a modality of treatment.

 

Dr Derrick Aarons MD, PhD, is a Jamaican family physician and consultant bioethicist; a specialist in ethical issues in health care, research, and the life sciences; the health registrar and head of the health secretariat for the Turks & Caicos Islands, and a member of UNESCO's International Bioethics Committee.