What are Stem Cells?

• Stem cells are special human cells that have the ability to develop into many different cell types. This can range from muscle cells to brain cells.
• In some cases, they also have the ability to repair damaged tissues.
• Researchers believe that stem cell-based therapies may one day be used to treat devastating ailments like paralysis and Alzheimer’s disease.

 Types of Stem Cells

• Stem cells are divided into two main forms: embryonic stem cells and adult (somatic) stem cells.

1. Embryonic stem cells:

• The embryonic stem cells used in research today come from unused embryos resulting from an in vitro fertilization procedure and that are donated to science.
• These embryonic stem cells are pluripotent, meaning that they can turn into more than one type of cell. 

2. Adult stem cells:

• There are two types of adult stem cells. One type comes from fully developed tissues, like the brain, skin, and bone marrow.
• There are only small numbers of stem cells in these tissues, and they are more likely to generate only certain types of cells (multipotent). For example, a stem cell derived from the liver will only generate more liver cells.
• The second type is induced pluripotent stem cells.
• These are adult stem cells that have been manipulated in a laboratory to take on the pluripotent characteristics of embryonic stem cells.

Applications

• The regenerative properties of stem cells make them extremely valuable in medicine. This is why stem cell treatments are also termed as regenerative medicine.
• For over 90 years now, hematopoietic stem cell transplantation has been used to treat people with conditions such as leukaemia and lymphoma. After chemotherapy or radiation therapy wrecks the patient’s healthy cells (along with the cancerous ones), a donor’s healthy bone marrow reintroduces functional stem cells to replicate inside of a patient and to produce additional normal blood cells.
• There are typically a very small number of adult stem cells in each tissue, and once removed from the body, their capacity to divide is limited. This is the fundamental limitation of stem cell therapies at the moment. 
• That is why, scientists have been focussed on manipulating adult stem cells to exhibit characteristics of pluripotent stem cells.