7.3

• Stem cells

  Undifferentiated cells which have the ability to differentiate into many different cell types
• Types of stem cells

  • Multipotent cells (can give rise to multiple types of cells)
  • Pluripotent cells (can give rise to many types of specialised cells, but not placental cells)
  • Totipotent cells (can give rise to all types of specialised cells, including placental cells)
• Sources of stem cells

  • Embryonic stem cells
  • Adult stem cells
  • Fused cells
• Induced Pluripotent Stem Cells (iPS cells) proces::

  1. Fibroblasts (connective tissue) taken from skin samples

  2. Viruses are used as vectors to introduce four genes for transcription factors

  3. These factors activate specific genes in adult cells to produce pluripotent cells

  4. Cells behave very similarly to embryonic stem cells - however, their effectiveness long-term is not known and cells show a tendency to become cancerous
• What is a strength of using Induced Pluripotent Stem Cells (iPS cells)

  Overcome ethical objections to the use of embryonic stem cells
• What are Induced Pluripotent Stem Cells?

  They are adult stem cells that have been reprogrammed to become pluripotent again
• How can embryonic stem cells be used in medicine?

  To treat a variety of diseases for example Parkinson’s, and replace damaged tissues

  In Parkinson’s it would be nerve cells
• Totipotent cells only occur for a limited time in mammalian zygote whereas other types of stem cells such as pluripotent, multipotent and unipotent cells are found in mature (somatic) mammals
• Ethical issues related to the use of stem cells

  • Ethical issues as embryos are killed in the process of stem cell extraction
  • Risk of infection when cells are transplanted
  • Cells could become cancerous