An introduction to iPSCs

Stem cells are cells that have the unique ability of differentiating into other types of cells in the human body. They can also self-renew by dividing to produce more stem cells. These cells are very valuable. Indeed, they provide specialised cells to the body and can replace them if they die.

Figure 1: Stem cells can differentiate into specialised cell or self-renew.
Image credit: Genome Research Limited

There are different categories of stem cells:

• totipotent stem cells: they only exist for 4–5 days after fertilisation of the egg, called the zygote. Totipotent cells can develop into literally any cell type found in the human body, from a neuron to a blood cell.
• embryonic stem cells (ES): they are derived from the inner cell mass of the blastocyst. ES cells are pluripotent, meaning they can only make the three primary germ layers: the ectoderm, endoderm and mesoderm.
• induced pluripotent stem cells (iPS/iPSCs): artificially created in the laboratory, iPSCs can differentiate just like ES cells. These are the main focus of this blog. Indeed, iPSCs are very promising in the field of regenerative medicine.
• and embryonic or adult tissue specific stem cells: these are multipotent, meaning they can only differentiate into a few cells types, and sometimes unipotent, meaning they can only produce a specific cell type.

What are induced pluripotent stem cells? Video credit: stemcellfoundation

As seen before, induced pluripotent stem cells (iPSCs) are laboratory created stem cells. They can be generated directly from adult cells like skin cells takes from a skin biopsy for instance. This technology was developed by the Japanese researcher Shinya Yamanaka and his lab group. Using four transcription factors (Oct4, Sox2, Lin28 and Nanog), they managed to completely reprogram skin fibroblasts into undifferentiated stem cells. The process only takes 2–3 weeks.

For his work, he won the 2012 Nobel Prize along with the English developmental biologist and stem cell pioneer, Sir John Gurdon, “for the discovery that mature cells can be reprogrammed to become pluripotent”.

A scheme of the generation of induced pluripotent stem cells. (Image credit: Wikipedia)

This incredible breakthrough changed the face of stem cell research. iPSCs can not only be used to study development and disease, but can also be used as a therapy.

iPSCs have strong advantages over embryonic stem cells. First of all, while using ES cells means that an embryo is destroyed, iPSCs are completely synthetic, and therefore don’t raise any ethical issues. Moreover, they are completely tolerated by the recipient since they come from the same person, so there is no risk of rejection.

When I saw the embryo, I suddenly realized there was such a small difference between it and my daughters. I thought, we can’t keep destroying embryos for our research. There must be another way.
– Shinya Yamanaka

Figure 2: iPS applications
Image credit: Functional Medical System

In conclusion, iPSCs cells have many potential applications, including in regenerative medicine, disease modelling, and drug discovery. See our next posts to read about some of them!