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BIOLOGY: STEM CELLS

BIOLOGY: STEM CELLS

Overview

Stem cells are cells that can renew themselves.
Stem cells renew themselves through mitotic cell division and can differentiate into a diverse range of specialised cell types
Stem cells are found in most multi-cellular organisms
There are two types of stem cells in mammals
Embryonic stem cells
Adult stem cells
Stem cells are mainly found in blood from the umbilical cord and the bone marrow
Due to their self-renewing nature, stem cells are very important for treatment of diseases



Importance of stem cells

For a cell to be characterised as a stem cell, it must exhibit the following properties
Self renewal: the ability to go through numerous cycles of cell division while maintaining the undifferentiated state
Potency: the capacity to differentiate into specialised cell types
In developing embryos, stem cells can differentiate into all of the specialised embryonic tissues
In adult organisms, stem cells act as a repair system for the body, replenishing specialised cells
Stem cells also maintain the normal turnover of regenerative organs such as blood, skin or tissues
Stem cells can be grown and transformed into specialised cells of various tissues such as muscles and nerves using cell culture
Stem cell treatment holds the potential of transforming human medicine, wherein stem cells introduce new cells into damaged tissue in order to treat a disease or injury
The ability of stem cells to self renew and differentiate offers the potential to replace diseased and damaged tissue without the risk of rejection or side effects


Current stem cell treatments

Currently, stem cell treatment is available to treat the side effects of chemotherapy on cancer patients, such as leukaemia or lymphoma
During chemotherapy most growing cells are killed by cytotoxic agents
These agents kill not only the leukaemia cells but also healthy haematopoietic stem cells in adjacent bone marrows.
Using stem cell therapy, healthy bone marrow stem cells are used to reintroduce healthy stem cells to replace those lost in the treatment



Potential stem cell treatments

Stem cells can be potentially used to treat a number of serious diseases. These include
Brain diseases such as Parkinson’s and Alzheimer’s
Cancers
Spinal cord injury
Heart damage
Haematopoiesis (blood cell formation)
Baldness, missing teeth
Blindness, deafness
Diabetes
Neural damage
Almost all these treatments are still in the research stage
In Jan 2009, the US Food and Drug Administration (FDA) gave clearance to Geron Corporation for the first clinical trials of an embryonic stem cell therapy on humans. The trial will evaluate the efficacy of the drug GRNOPC1 on patients with spinal cord injury



Important milestones in stem cell research

1963: Ernest McCullogh (Canada) and James Till (Canada) illustrate the presence of self renewing cells in the bone marrow
1968: Bone marrow transplant between two siblings successfully treats Severe Combined Immunodeficiency (SCID)
1978: haematopoietic stem cells discovered in human blood
1998: James Thomson (USA) derives the first human embryonic stem cell line
2001: Scientists at Advanced Cell Technology (USA) clone first early human embryos for the purpose of generating embryonic stem cells
2006: Scientists at Newcastle University (England) create first every artificial liver cells using umbilical cord blood cells
2008: Robert Lanza and colleagues at ACT create first human embryonic stem cells without destruction of the embryo