Academic Review 2024

66 ST EDWARD’S, OXFORD

Adult stem cells INTRODUCTION TO ADULT STEM CELLS

application. Due to these new advancements, hematopoietic stem cell transplantation is now one of the only definitive cures currently accessible for patients suffering from thalassemia and sickle cell anaemia. However, the application of human stem cell therapies is limited by the lack of a matched donor for most patients and a high risk of graft rejection due to some of the chemicals used (Fan, He, & al, 2015). A successful example of treatment was when scientists were able to remove adult stem cells from the bone marrow of a patient suffering with sickle cell disease, where they were able to locate the gene that caused the disease in the stem cell. Using CRISPR/Cas9, researchers were able to edit the HBB gene which is responsible for the disease. The new recombinant stem cell was then implanted back into the patient that it had been taken from. The cells then divided to create new cells that did not possess the HBB gene. In this instance the use of adult stem cells rather than embryonic stem cells was more beneficial as the stem cells came from the patient’s body meaning there was a lower percentage chance of rejection. This treatment also does not carry many serious ethical implications as the research benefited the patient and no lives were harmed in the process. NEGATIVES OF ADULT STEM CELL USE Some people argue that adult stem cells do not hold as much importance in the world of science as embryonic or induced pluripotent stem cells. This viewpoint is held as adult stem cells have a determined cell type, meaning that without induced pluripotent reprogramming, adult stem cells have a predetermined cell type. This is due to the fact that unlike embryonic stem cells, adult stem cells are multipotent progenitor cells possessing limited differentiation potential or are unipotent, capable of generating only a single specific cell type. Adult stem cells are found in specialized vascular microenvironments, referred to as the stem cell niche. The niche provides intrinsic and extrinsic signals that regulate cell fate and renewal and may explain why adult stem cells, isolated from various tissues, behave differently (Hansen & Inselman, 2011). This means that stem cells cannot be universally used to treat all illnesses, but adult stem cells are cheaper to extract and carry less ethical burden. Another downside of adult stem cells is that they cannot be grown for long periods of

Adult stem cells and cord blood stem cells do not raise many ethical concerns and are widely used in research and clinical care. However, these cells do not possess the same pluripotent properties as embryonic stem cells. Adult stem cells are found in small numbers in most adult tissues, such as bone marrow or fat. Scientific interest in adult stem cells is centred around two main characteristics. The first is their ability to divide or self-renew indefinitely, and the second their ability to generate all the cell types of the organ from which they originate, potentially regenerating the entire organ from a few cells (Mahla, 2016). Adult stem cells are hailed for their remarkable plasticity, transdetermination and transdifferentiation abilities (He, Zhou, & al, 2022). These properties relate to how adult stem cell types present in one tissue or organ can turn into a cell type from another tissue or organ without going through a pluripotent cell state. Even though adult stem cells have these properties they can only switch in lineage in a stem or progenitor cell to a closely related cell type. However, emerging evidence suggests that adult stem cells may be able to differentiate into various other cell types. Adult stem cells can be harvested through a variety of methods, such as tissue fat extraction, bone marrow extraction and blood drawing. The most common way to harvest stem cells is blood drawing; it involves temporarily removing blood from the body, separating out the stem cells and then returning the blood to the body (Kooner, 2019). The harvesting does not risk the loss of any human life or the destruction of a blastocyst as happens in embryonic stem cell practices. This reduces the ethical issues of adult stem cell research; this is one of the reasons why adult stem cells are the most common type used in research labs. USES OF ADULT STEM CELLS An example of a highly successful use of adult stem cells is from the CRISPR/Cas9 research that has recently been conducted. Typically, the CRISPR/Cas9 system has been used in the genetic modification of pluripotent or multipotent stem cells, after which the cells are differentiated into specific cell species and used for functional analysis and even clinical transplantation. Recent advancement in CRISPR/ Cas9 technology has increased the knowledge and potentials of stem cell research and its therapeutic