Stem cell therapies and Alzheimer’s disease
function of stem cells and weigh up the benefits and risks of these potential therapies in comparison to treatments used today.
3.1: an introduction to stem cells
Stem cells are a type of cell that can differentiate into different cell types such as skin cells or red blood cells. In the bodies of children, adults, and the elderly, there are different types of stem cells. For example, the stem cells present in bone marrow are called hematopoietic stem cells, which are the mother cells of the cells in the blood. Other stem cells are found at various locations in the body, such as in organs that usually repair themselves very quickly, like the outer layers of the skin. 37 Today, there are successful stem cell treatments being used routinely by the NHS, such as bone marrow stem cell transplants for leukaemia and sickle cell anaemia. Stem cells can be harvested from blood, bone marrow, or from the umbilical cord and placenta of a new-born baby. After cancer cells have been destroyed, these stem cells are transplanted to the patient, and are regenerated into healthy red blood cells. 38 Embryonic stem cells (ES) are present in very young embryos and can differentiate into any type of cell. They can grow and proliferate rapidly, providing a limitless supply of samples to test. Moreover, they are pluripotent, meaning they have the potential to become any cell type in the body. The problem with these types of cells when looking for an AD treatment is that the patient’s immune system will recognise them as foreign if planted in the patient’s brain, as they are taken from an outside source. Moreover, there are moral concerns with using ES cells, due to the destroying of embryos that could potentially become a human life. For this reason, research on ES cells is currently very restricted. 39 The rest of the dissertation will not look at ES cells, but they are valuable to consider when looking at potential issues that may arise in a stem cell-based treatment. Very recently, there was the discovery of induced pluripotent stem (iPS) cells. These cells are derived from an adult mature cell that has regained the capacity to differentiate into any type of cell in the body. This is done through adding certain genes in the adult cell, to revert it back to its stem cell form. Patient specific cells are suitable for transplantation, avoid immune reactions, and can be produced without the need of human embryonic stem cells. 40 In 2009, scientists successfully generated retinal cells of the human eyes by reprogramming adult skin cells. This enabled detailed investigation of the embryonic development of retinal cells, and opened doors for novel therapies for eye diseases. Neural stem cells (NSCs) are the other type of stem cells that are valuable when looking for an AD treatment. Neural stem cells can be found in neurons in the hippocampus (instrumental in forming memories), olfactory bulbs (an area that processes smell), the septum (an area that processes movement), and the spinal cord. These have the potential to give rise to offspring cells that grow and differentiate into neurons and glial cells . 41 Neural stem cells can be isolated from various neural tissues
37 Luk et al. 2017 38 Stem cells and bone marrow transplants 2018. 39 Benefits and risks associated with the use of stem cells in medicine n.d. 40 Jebelli 2017a: 139-40. 41 Rugnetta 2008.
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