Learn about Stem Cells
You may not realise it but bone marrow transplants are really a transplant of stem cells!
So what is a stem cell?
Stem cells are the building blocks of the body. They are unspecialised cells that have not yet been assigned a job in the body, unlike for example, a red blood cell that functions by carrying oxygen through the blood stream.
Stem cells are very rare and unique cells and they make up only an extremely small proportion of the 300 trillion cells that make up the human body. They are special because they are used by the body to repair or replace cells that are damaged or destroyed.
Everyone has them!
Stem cells are very special cells that can get orders to change into many different kinds of cells such as muscle, blood (bone marrow), nervous tissue, bone, cartilage and skin cells. Not only can they produce different types of cells but they can also make copies of themselves (called self-renewal). However, there is some evidence that their renewal and capacity to repair tissues decreases with age.
What do they look like?
Scientists are pretty sure that stem cells are everywhere in your body, but they are not exactly sure what they look like. They know that stem cells carry certain markers on their cell surface that make them different from other cells in the body and these markers can be used to isolate them for use in research and in different kinds of therapy. Scientists are still learning how to control the growth and development potential of stem cells.
Why are researchers so interested?
Stem cells have three properties that distinguish them from other cell types and make them interesting to scientists: they are unspecialised; they are able to divide and produce copies of themselves; and they have the potential to produce other cell types. They are central to many research areas such as providing an ideal model to understand the development of organisms under healthy and disease conditions, the means to develop new families of drugs and new therapies such as regenerative medicine, improving bone marrow transplants, the treatment of cancer and the possibility of building new tissues outside the body.
‘The possibilities are endless’
Some cells can't repair themselves very well, like brain, nerve, some muscle and badly damaged kidney and liver cells. Scientists are working on ways to make cells reproduce or repair to help with diseases. This would offer great potential for the treatment of Alzheimer disease, spinal cord injuries or other nerve injuries, multiple sclerosis, muscular dystrophy, liver diseases and kidney failure, diabetes and Parkinson’s disease. The list of applications could go on and on. Current projects using stem cells include building human corneas (part of the eye that gives it the most optical power) and treating heart attacks by reprogramming stem cells from bone marrow and growing new skin for grafting.
Bone marrow transplants and stem cells
Bone marrow transplants are really a transplant of stem cells. In fact this procedure is now called a Haematopoietic Stem Cell Transplant (HSCT). Haematopoietic stem cells are the ‘parent cells’ from which all the cells of the immune system develop. Phagocytes arise from stem cells found in bone marrow; so replacing these using healthy stem cells can cure CGD.
Stem cells and gene therapy for CGD
In HSCT stem cells from a healthy person are used to transfer the ability to fight infections. In CGD gene therapy, the patient’s own stem cells are used but these are treated so that they express a healthy working copy of the gene defective in CGD. One could call them mini-gene stem cell transplants. Bone marrow cells are harvested; the parent stem cells isolated and these cells are then mixed together with the normal healthy gene spliced to a harmless virus (termed vector). The virus carrying the corrective gene then penetrates the patient's stem cells replacing the defective gene with the healthy gene. These corrected cells are then grown up in an incubator. Once sufficient numbers have been obtained the corrected cells are then re-injected into the patient's blood stream. Gradually they are absorbed back into the patient's blood marrow where they carry on their work of manufacturing blood cells - cells that are now capable of fighting infections. This approach is being used for many other genetic conditions.
There are different types of cell stems with varying potential
There are several different types of stem cells originating from different tissue sources.
Tissue stem cells
Tissue stem cells are found in some adult tissue and are used to replenish cells in the body, replacing those that naturally wear out. These cells are also referred to as adult stem cells. They are still at an early stage in development and retain the potential to turn into different types of cells of that tissue or organ. Scientists are investigating the possibility that tissue stem cells from one tissue might under the right circumstances give rise to cell types of another tissue. For example some stem cells found in bone marrow are able to mature into cells specific to bone, cartilage, fat, tendons, muscle and heart.
Human umbilical cord blood stem cells
Stem cells are also found in human umbilical cord blood. Doctors typically obtain cord blood from the placentas of volunteer donors after they give birth. Some parents are now choosing to bank cord blood in case of need for their children’s health. Human umbilical cord blood stem cells are being used to treat anaemias or cancers of the blood, such as leukaemias and lymphomas.
Stem cells from umbilical cord blood provide an alternative source of stem cells for transplantation procedures for CGD. However, one problem is that there may not be enough umbilical cord stem cells in any one sample to transplant an adult so sometimes stem cells from many donors needs to be pooled. The use of stem cells from this source has increased the chances of identifying an appropriate bone marrow donor.
Research suggests that human umbilical cord blood stem cells are "younger" stem cells than those from adult bone marrow. They are able to divide for longer times in cell cultures than most adult stem cells, and may give rise to different tissues. Their potential to form many different cell types is currently being explored.
Amniotic fluid stem cells
Recently American scientists have isolated cells from amniotic fluid that have stem cell characteristics. Although the findings have yet to be confirmed these cells were able to produce a number of cell types including bone, liver and nerve cells. These cells could represent a new potential source of stem cells for therapy.
Embryonic stem cells
Embryonic stem cells, the only cells that can evolve into any cells in the body are found in few day-old fertilised eggs. These have the greatest self-renewal and developmental potential. Scientists are working hard to understand the properties of these cells and to understand the mechanisms that regulate their differentiation into adult cell types. In addition, many researchers are using these cells to set up models to study early human development and also to provide genetic and cell-based therapies for disease.
Ethical debate
The use of some stem cells is a matter of debate. Research on human embryonic stem cells (ES cells), a tiny part of the overall research on stem cells, raises several ethical issues. They are addressed by national legislation worldwide. In the UK, unlike in many other countries, stem cells derived from human embryos and foetal tissues are not really party political issues. The production of new embryonic stem cell lines is legal and is governed under strict licensing procedures. The UK has the world’s first stem cell bank, which is leading an international initiative to characterise all the ES lines now available around the world.
IMPORTANT NOTE :
The information contained on this website is intended only as a guideline, not as a substitute for medical advice. Always consult your doctor if you or your child has any CGD symptoms or concerns.
© 2001-2007 The Chronic Granulomatous Disorder (CGD) Research
Trust
Registered Charity No. 1003425 email:cgd@cgdrt.co.uk
The CGD Research Trust is a member of the Association of Medical Research Charities (AMRC), the Genetic Interest Group (GiG) and an associate member of the International Patient Organisation of Primary Immunodeficiencies (IPOPI)
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