2. Stem cells

• Stem cells


  • Undifferentiated cells
  • Can continuously divide
  • Can become specialised
• Differentiation


  Process by which stem cells become specialised
• Specialised cells which stem cells can differentiate into

  • Epithelial cells
  • Blood cells
  • Bone cells
  • Nerve cells
  • Immune cells
  • Sex cells
  • Muscle cells
• Totipotent stem cells


  • Can divide and produce any type of body cell
  • Can form extraembryonic cells which make up the placenta and umbilical cord
• Totipotent stem cells found in

  • Early mammalian embryos
  • Only available for a limited amount of time - first few divisions
• Pluripotent cells


  • Can divide in unlimited numbers and produce any type of cell
  • Apart from extraembryonic cells which make up the placenta and umbilical cord
• Pluripotent stem cells found in

  Embryos up to 16 days old
• How pluripotent stem cells can be used in treatment


  • Producing functional beta cells on the islets of Langerhans of type 1 diabetics
  • To regrow damaged cells in humans - e.g burnt cells
  • To replace nerve cells in individuals in Parkinson's disease
• • Some effective research into pluripotent stem cells but their effectiveness still remains an idea
  • Prospect of them is still intriguing to many researchers
• Multipotent cells


  Can differentiate into a limited number of cells
• Multipotent cells found in

  Mature adult mammals
• Multipotent cells in bone marrow

  Can differentiate into multiple types of blood cells
• Unipotent cells


  Can differentiate into only one type of cell
• Unipotent cells found in

  Mature adult mammals
• Cardiomyocytes


  • Heart muscle cells that make up the tissues of the heart
  • Thought to not be able to divide and replicate themselves in mammals
• Unipotent cells in cardiomyocytes


  • Allow for the regeneration of damaged heart tissue
  • Believed to be really slow and some myocytes never replaced in individuals lifestyle
  • Some believe the opposite - occurs more quickly and several times in a lifetime
• Embryos in the first few cell division

  Contain totipotent stem cells
• Embryos beyond this point

  Up to 16 days contain pluripotent stem cells and can differentiate into any type of cell
• Umbilical cord blood


  Contains multipotent stem cells which can differentiate into any type of cell
• Placenta


  Contain multipotent cells and can develop into limited number of cells
• Adult stem cells

  • Found in bone marrow
  • Can produce different cells to repair those within particular tissue or organs
• Induced pluripotent stem cells (iPS cells)


  • Produced from adult somatic cells (body cells)
  • Using appropriate transcriptional factors which can turn on and off certain genes
• Adult unipotent cells returned


  To state of pluripotency - express all the genes associated with pluripotent cells through the use of transcriptional factors which can turn on and off certain genes
• Benefits of iPS cells

  • Helps over come many of the ethical issues associated with the use of embryonic stem cells
  • No destruction of embryo and contain same properties as pluripotent cells
  • Also divided indefinitely and show self renewal properties - samples don't need to be continuously taken
• More research is required into how similar iPS cells actually are to pluripotent embryonic stem cells
• Evaluate the use of pluripotent stem cells

  • Because they can divide in unlimited numbers some research has found that they divide continuously to produce tumours
  • Therapeutic clones of patients must be made to be used. They have to be destroyed after use. Ethical concerns result sin debate as there’s arguments that there’s potential for life