Sep 6, 20237 min read

What are stem cells?

Stem cells are unspecialised cells that are found throughout the human body, they have the ability to divide by mitosis an infinite number of times and give rise to various specialised cells through differentiation.[1] Stem cells are undifferentiated, meaning they do not acquire a specific job or function; however, they do have the capacity to develop into any other form of cell in your body such as muscle cells, blood cells, nerve cells and many more, this potential is called potency.[2] Potency can be split into four main sections: totipotency, pluripotency, multipotency, and unipotency. Totipotent cells can differentiate into embryonic (any cell type found in an embryo), as well as extra-embryonic cells (cells that constitute the placenta), these cells are found in embryonic tissues such as a zygote.[3] This means that such cells can generate a fully functional living organism.[4] Pluripotent stem cells can self-renew and have the ability to form any cell type with the exception of extra-embryonic cells; they are ideal for use in cellular therapy and regenerative medicine due to their powerful capacity to differentiate into a broad variety of tissues.[5] Multipotent cells are adult cells that can regenerate (can divide an unlimited amount of times) and differentiate into cells types that are closely linked such as haematopoietic adult stem cells. Finally, unipotent stem cells are most limited, they can only differentiate into their own lineage, an example being muscle stem cells.[6] Stem cells divide by mitosis when exposed to the right bodily conditions. They are found mainly in embryos (embryonic stem cells), which can be made through therapeutic cloning. Somatic cell nuclear transfer is the creation of embryonic clones by the fusion of a diploid nucleus with an enucleated egg.[7] Nuclear reprogramming is another artificial method of stem cell creation, which works by instigating a change in the gene expression profile of a cell using oncogenic retroviruses and transgenes.[8] Umbilical cord blood or the baby’s placenta is also a source of stem cells, which can be frozen and stored.[9] And adult stem cells can be found in specific adult tissues such as bone marrow. Embryonic stem cells are pluripotent, allowing them to become any cells in the body, whilst adult stem cells are multipotent only having the ability to develop into certain types of tissue.

Scientists are researching ways in which stem cells can lead to the creation of personalised medicine.[10] For instance, regenerative medicine focuses on the creation of new specific tissue that can be used to replace parts of organs that are old or damaged. Stem cells’ ability to create specialised cells can be guided to create specific cells needed to repair and regenerate various tissues.[11] Embryonic stem cells which are either totipotent or pluripotent, give rise to every cell type in the fully formed body and therefore can be harvested and used for therapeutic treatment of disease. Totipotent cells can be collected during the first 3-4 days after fertilization, whilst pluripotent cells arise on day 5, such source of stem cells presents potential ethical issues.[12] Adult stem cells can also be harvested from donation sources such as bone marrow, peripheral stem cells, and umbilical cord blood, however they cannot be manipulated to produce all cell types, limiting their use.[13]Stem cells’ ability to differentiate, allows them to be potentially used in cardiovascular disease treatments, brain disease treatments, blood disease treatments and many others that would require specialised cells to be replaced.[14] Stem cells are also highly demanded in medicine, as observing them mature into various specialised cells, may allow researchers to increase their understanding of diseases, their conditioning and development.[15] Stem cells can be used to model diseases in a dish, therefore allowing scientists to gather knowledge about degenerative conditions for which there is currently no cure.[16] Furthermore, specific types of stem cells can be used to test drugs for safety and quality. They could be programmed into tissue-specific cells targeted by the drug, and therefore determine the efficiency, effectiveness, and the ability of the new drug.[17]

Stem cells can be used to treat Stargardt’s disease. Stargardt’s disease is an inherited form of juvenile muscular degeneration, which results in the protein in the retina malfunctioning, leading to a progressive loss of vision and potential blindness.[18] This disease is derived from a mutation of the ABCA4 gene, impairing energy transport in retinal photoreceptor cells and leading to their degeneration.[19] Stem cells have been researched to treat the disease. Dead cells in the retina can be replaced by stem cells, through an injection into the eye of retina cells derived from embryotic stem cells.[20] The trials for such treatment are still ongoing, however they were successful and haven’t presented any harmful effects yet. Stem cells can also be used in the treatment of leukaemia – a generalised term referring to a group of cancers that develop in the bone marrow.[21] Gene mutation causes the over-production of abnormal white blood cells, constituting the cancer. In order to treat the cancer and eradicate the mutated cells in the bone marrow, patients are treated with chemotherapy. During chemotherapy chemicals are inserted into the body which destroy all bone marrow cells, therefore in order to preserve hematopoietic stem cells, they are removed before treatment using a large needle.[22] The adult stem cells are frozen and stored, and later transplanted back using transfusion, to restore healthy bone marrow. Stem cells encourage the production of new bone marrow and restore the immune system.[23]

Although the use of stem cells has many advantages there are certain ethical disadvantages recognized. Embryonic stem cells are totipotent or pluripotent, their ability to differentiate into any cell increases the risk for tumours, and therefore can bring harm to the patients.[24] Furthermore, embryonic stem cells are collected from early day embryos, which presents ethical concerns with the creation of such embryos and their supposed “aliveness”. Some people can argue that stem cell research harvests unborn babies. Adult stem cells present collection difficulties. Such stem cells can be embedded deep in the tissue and consequently hard and painful to extract.[25] Moreover, the donors have to have a match in certain vitals such as blood type in order for the stem cells to be accepted by the patient’s immune system. For instance, UK allows the use of embryonic stem cells for research into stem cell therapy under strict laws and regulations. The research requires a license from the Human Fertilisation and Embryology Authority and must comply with the Code of Practice for the use of human stem cell lines, a requirement supported by MRC funding.[26] Research proposals must be approved by government agencies, and later stem cells can be registered and stored in the UK Stem Cell Bank.[27] The UK allows the use of stem cells as it fulfils the Human Fertilisation and Embryology Act 1990, which is “increasing knowledge about serious disease or other serious conditions”. [28]The UK believes that stem cell research is vital in the development of future medicine, and therefore can be conducted under meticulous regulations. On the other hand, the use of human embryo for stem cell research is illegal in Austria. Austria prohibits therapeutic and reproductive cloning and the use of human embryos and gametes for research.[29] Adult stem cells are prioritized for research. The reason embryonic stem cell research is prohibited, is because Austria focuses on the ethical issues concerned with collecting stem cells from embryos. Deriving stem cells from human embryo destroys the blastocyst, and there are concerns with the sourcing of the embryos.[30] There is also widespread controversy over the “destruction of innocent human life” for scientific research.

Overall, the research on stem cells is ever developing, however stem cells are presenting great promise for the future of medicine.

What are stem cells?

Recent Posts

Comments