Definition and Classification of Stem Cells:

What are Stem cells?

In simple terms, stem cells are cells that

have the ability to divide and create other cells like themselves, as well as divide and create cells more differentiated than themselves

Stem cell properties are :

• Ability to replicate themselves (make copies of themselves)

Potency : capacity to differentiate into specialized cell types and tissues

Based on potency stem cells can be divided into 5 major types:

– Totipotent Stem Cells (Omnipotent)

• Pluripotent
• Multipotent
• Oligopotent
• Unipotent
• Totipotent

Can differentiate into embryonic and extra embryonic stem cells

• Can develop into complete organism
• Produced from fusion of egg and sperm cell
• Comes from embryo 1 to 3 days old.

Pluripotent Stem Cell

• Descendants of totipotent stem cells
• Can form any cell type derived from germ cells
• Example : blastocytes(5-14 days old )
• Also called embryonic Stem Cells

Multipotent Stem Cells:

• Cell differentiated , but can form a number of new tissues
• Adult Stem Cells
• Example: fetal tissue, cord blood , adipose tissue, bone marrow

Oligopotent Stem Cells :

– Can differentiate into only a few types of cells

• examples: myeloid and Lymphoid Cells

Unipotential Stem Cells:

• Can only produce One cell type
• Example : Muscle Stem Cell
• Stem cells have potential to replace cell tissue that has been damaged or destroyed

  Types of Stem Cells:

  1.Embryonic Stem Cells
  2.Adult Stem Cells
  3.Induced Pluripotent Stem Cells

  Embryonic Stem Cells:
  Derived from the inner cell mass of blastocytes of preimplantation -stage embryos

  Need specific signals to differentiate to the desired cell types

  If simply injected directly they will differentiate into many different type of cells including creation of teratomas

  2nd problem transplant rejection

  Adult Stem Cells:

• Less controversial

No destruction of embryos

no risk of immune rejection since it comes from the recipient (autograft)
Induced Pluripotent Stem Cells:
– somatic cells produced in the lab and are reprogrammed genetically to an embryonic stem cell state

No immune rejection issues

In Summary Stem Cells are part of the regenerative medicine group of treatment modalities that will eventual change how medicine is practiced.
AUTHOR
Dr. Anteneh Roba