Stem Cells

• Stem cells are cells that have not undergone differentiation. A cell which has not yet become specialised is called undifferentiated.
• An embryo develops from a fertilised egg. Cells at the early stages in the development of the embryo are stem cells. If cells are removed from the embryo – called embryonic stem cells - they will differentiate into any cell type.
• Some stem cells remain in the bodies of adults – adult stem cells. Adult stem cells are found in limited numbers at certain locations in the body.
• Adult stem cells can be found in several regions of the body, including the:

  • brain
  • eyes
  • blood
  • heart
  • liver
  • bone marrow
  • skin
  • muscle
• Adult stem cells can differentiate into related cell types only, for example, bone marrow cells can differentiate into blood cells and cells of the immune system but not other cell types.
• Medical treatments with stem cells can help conditions such as diabetes and paralysis. An embryo can be produced with the same genes as the patient in a process called therapeutic cloning. These stem cells will not be rejected by the person receiving them, so they can be used for medical treatments. There are some risks using stem cells for medical treatments such as the transfer of viral infections. Some people also have ethical concerns or religious objections to their use.
• Cell division in plants occurs in regions called meristems.
• Cells of the meristem can differentiate to produce all types of plant cells at any time during the life of the plant.
• The main meristems are close to the tip of the shoot, and the tip of the root.
• Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.

  • Rare species can be cloned to protect from extinction.
  • Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.
• Stem cells have the potential to be transplanted into patients to treat medical conditions and disease as they can be divided into differenct cell types. Therefore, they could be used to replace cells that have been damaged or destroyed, eg:

  • In type 1 diabetes
  • In cases of multiple sclerosis, which can lead to paralysis
  • In cases of spinal cord or brain injury, that have led to paralysis

  The stem cells used could be: embryonic stem cells or adult stem cells.
• Adult stem cells will differentiate into a narrower range of cell types. Bone marrow transplants are an example of adult stem cell transplant. Bone marrow cells will differentiate into different types of blood cell. Bone marrow transplants are carried out:

  • In cases of blood cell cancer such as leukaemia and lymphoma
  • When blood cells have been destroyed by cancer treatment
• Embryonic stem cells can differentiate into a wider range of cell types, but are difficult to obtain and their use raises ethical challenges. The best source is the five-day-old embryo.