Tag Archives: types of stem cells

What are stem cells ?

I decided to start my blog, with some general introductory information about stem cells, in order to explain some terms that are important to better understand the articles that will follow on mesenchymal stem cells

What are stem cells?
The term “stem cells” refers to many different types of cells found in most complex organisms. Although there are many types of stem cells, they all share two certain attributes, which will be later explained. These two characteristics are:

  • Self – Renewal
  • Potency

What is the role of stem cells?
Stem cells have many roles, but generally we can say that they have three main roles. Their first role is to form and develop from zero all the different types of tissue and organs of an organism. In simple words the first cell that we are derived from, the zygote, is nothing but a powerful stem cell!

Their second role is to repair any damages induced due to external stimuli, for example an infection or a trauma.

Their third role is to replenish, in a constant basis, all the cells that die due to ageing. For instance, hematopoietic stem cells are responsible for creating daily millions of new blood cells that in return replace millions of blood cells that die on a daily basis.

What is self-renewal?
Self renewal is one of the two abilities stem cells have. It refers to their capacity to replicate themselves indefinitely, giving more and more identical stem cells.

What is potency?
Potency refers to the number of different somatic cells (e.g. a neuron or a osteoblast) that a stem cell can develop into. The higher the number the bigger the potency. So, in the example mentioned before (zygote), we can say that the zygote has the highest possible potency since it can virtually transform into all kinds of cells. We say that a zygote is a totipotent stem cell. Potency may have one of the following degreees:

  • Totipotent
  • Pluripotent
  • Multipotent
  • Oligopotent

As mentioned before totipotent stem cells, are stem cells with the capacity to transform into all different types of somatic cells

The same applies for pluripotent stem cells, the only cells they can’t differentiate into are the ones forming the placenta

Multipotent are stem cells that can give rise to many different types of cells, which all however belong to the same type of tissue. Mesenchymal stem cells, are such an example since they can only transform into the cells of the skeletal tissue.

Oligopotent stem cells can only give rise to a few types of specialized cells, again of the same tissue. An example of oligopotent stem cell are vascular stem cells that only transform into two types of cells: endothelial cells and smooth muscle cells.

Types of stem cells
Now that we have explained the various types of stem cells we can better explain some of the types of stem cells. Taking a stem cell’s potency under consideration we can categorize them into two large groups:

  • Embryonic Stem Cells
  • Adult Stem Cells

Totipotent and pluripotent stem cells belonging to the first category.
Multipotent and Oligopotent stem cells belong to the second category.

A colony of embryonic stem cells

A colony of embryonic stem cells

Subtypes of adult stem cells
There are many subtypes of adult stem cells, depending on the tissue the cells they differentiate into, belongs to. Here are some types of adult stem cells:

  • Mesenchymal stem cells, which develop into cells of the skeletal tissue
  • Hematopoietic stem cells, which develop into blood cells (e.g. platelets, red blood cells, T-cells, B-cells)
  • Neural stem cells, which differentiate into neurons and brain cells
  • Endothelial stem cells, which develop into the cells forming the endothelium
Picture of an isolated mesenchymal stem cells

Picture of an isolated mesenchymal stem cells

Induced pluripotent stem cells
These are stem cells that are lab-grown by scientists, and they don’t occur naturally. They  are created using normal somatic cells (e.g. from skin or urine) via a method called transfection. With this method these cells are reversed back to a stem cell like nature, usually with pluripotent capacity.

That’s all for now..Next post will be on mesenchymal stem cells

If you have any questions please leave a comment, I will gladfully answer it!

Sources used: Stem Cells Wikipedia Article