BIOLOGY: STEM CELLS

BIOLOGY: STEM CELLS

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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
  

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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

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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

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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
  

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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

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