Stem cells

Stem cells are the type of cells that have the ability to continuously divide and differentiate into other, various types of cells

Properties of stem cells

• They are unspecialized cells

• They rapidly proliferate

• They can differentiate into different types of cells

• It can adopt newer identities and form various kinds of cells due to its plasticity

• Stem cells have the ability to repair, restore, and regenerate new stem cells
  

Kinds of stem cells

Totipotent

This form of stem cell can differentiate into any other cell type. A fertilized egg or zygote is an example.

Pluripotent

These cells can form any other type of cell besides placenta and embryo. Examples include embryonic stem cells.

Multipotent

Some cells of blastocyst (A day 5 embryo) have limited properties as to which cells they can differentiate into. They have the ability to develop into a specific type of cell within an organ. For example, a blood stem cell can form a white blood cell or a red blood cell.

Types of stem cells

1. Embryonic stem cells

2. Adult stem cells

Embryonic stem cells

• It is a totipotent cell

• The inner cell mass is pluripotent

• In an embryo, the outer cells are called the trophectoderm, which form the placenta. The inner cell mass divides to form the mesoderm, endoderm, and ectoderm, and eventually the rest of the cells that constitute our body

• These are derived from a growing 5-6 day old embryo, ie, 5-6 days post fertilization, when the embryo is ready to implant in the uterus
  

Adult stem cells

• These are undifferentiated cells found among specialised or different cells in a tissue or organ. They have a more restricted ability to produce different cell types and to self renew

• They are called so since they are developed after an embryo turns into a foetus and is no longer an embryonic stem cell

• Sources of the patient's own stem cells (autologous) are either from the patient's own body or from the cord blood

• Sources of stem cells from another donor (allogeneic) are primarily relatives or completely unrelated donors (unrelated-allogenic) and are extracted from the donor's body or cord blood

• Xenogenic stem cells are when the stem cells of a different species are transplanted

  Did you know?

  While most blood stem cells reside in the bone marrow, a small number are present in the bloodstream. They are called multipotent- peripheral blood stem cells and are used to treat leukaemia and other blood disorders

Question to ponder- What could the source of stem cells for medical therapies be?

• Tens of thousands of frozen embryos are routinely discarded once couples finish their treatment

• These surplus embryos can be used to produce stem cells via regulated rules and policies in the future