Stem cell technology

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Stem cells have capacity to differentiate into any type of cells i.e. they are unspecialized cells. These can divide number of times and can be used in different therapies for variety of disorders and injuries such as Parkinson disease, severe burns, damage to the spinal cord and a number of other human diseases.
 
Two type of stem cells
  • Embryonic stem cells – derived from the inner mass of mammalian embryo at a very early stage of development, when it is just a hollow ball of  dividing cells called blastocyst.
    - The embryonic stem cells at early stage are totipotent (give rise to any cell type of the adult organism).
    - The embryos from which stem cells are harvested are generally developed through in vitro fertilization (fertilized outside human body) so that ethical concerns are met.
  • Adult Stem Cells – Present in adult human body.
     - They form part of some tissues like the epidermis of the skin, the lining of the small intestine and the bone marrow which undergoes continuous cellular change.
APPLICATIONS OF STEM CELLS
  • cell based therapies.
  • Helpful for cancer treatment (bone marrow stem cell)
  • Use in early clinical trials in Parkinson’s diseases ( foetal stem cells)
  • With the help of stem cells artificial organs are created, example liver, heart, pancreas.
Classification of stem cells based on their dividing capacity:
1. PLURIPOTENT STEM CELLS
  • can divide into various different cell types except for totipotent stem cells and cells of placenta.
  • develope about four days after the fertilization.
2. TOTIPOTENT STEM CELLS
  • capacity to differentiate into any cell type including placenta (which nourishes the embryo ).
  • develop in first few divisions of the fertilization.
3. MULTIPOTENT STEM CELLS
  • descendents of pluripotent stem cells and antecedents of specialized cells in particular tissues.
  • Example : Hematopoietic stem cells ( found in the bone marrow ; give rise to all type of cells found in blood- including red blood cells, white blood cells and the platelets), Neural stem cells- which can differentiate into nerve cells.
Sources of Stem Cells

Embryonic Stem (ES) cells
  1. Derived from human embryos that are few days old
  2. Have the potential to become almost any type of cell.
  3. Difficult to manipulate
  4. Ethically contentious as the embryo is destroyed in the process
Foetal Stem Cells
  1. Derived from aborted human foetuses
  2. Have the potential to become many of the cell types
  3. Ethically contentious and limited availability
Cord blood and placental stem cells
  1. Derived from umbilical cord blood and placentas
  2. Already used in a variety of therapies
  3. Easily extractable
  4. Can currently only from a limited number of cell types
  5. Available in low concentrations
Adult stem cells
  1. Found in all humans
  2. Already in use for some therapies
  3. Sometimes difficult to access
  4. Can currently form a limited number of cell types
Practice Questions
Q1
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