Induced Pluripotency — The Alternative?
Concerns surrounding the use of embryonic stem cells (ESCs) in research and medicine resulted in a huge effort focused on the development of an alternative type of stem cell that maintains the typical pluripotent characteristics, without the ethical burden. In 2006, researchers Yamanaka and Takahashi described the invention of a remarkable technique that produces stem cells by “reprogramming” somatic cells. The term “somatic” describes any cell of the body, such as a skin cell or a hair follicle cell; essentially any cell that has already begun the process of differentiation from a stem cell. These somatic cells could now be transformed back into stem cells. The revelation that these cells were reverted backwards in terms of their usual developmental progression into a stem cell was nothing short of a marvel. The stem cells produced using this method were termed “induced pluripotent stem cells”, or iPSCs for short. The name indicates that these cells have the highly sought after pluripotent capabilities (these were described in our first post), and that they are induced, i.e. they are led to this state through an active process.
The technique works because although all of the cells in our body (e.g. skin cells, brain cells, gut cells…) contain the same DNA and therefore the same genes, the set of genes that are “switched on” in each type of cell varies. The consequence of different combinations of genes being switched on or off is that there are many different types of cell, each with very specific characteristics. In fact this switching on and off of various combinations of genes is what enabled multicellular organisms such as us humans to evolve. Reprogramming somatic cells into iPSCs occurs as a result of overriding which genes are switched on in a cell, causing the cell to switch on (or express) genes that are specifically responsible for making a cell “be a stem cell”. In other words, if you actively switch on the stem cell genes that are sitting silently in a cells DNA, the cell becomes a stem cell.
In addition to the benefit of reduced ethical concern, iPSCs have many other advantages over the use of ESCs. One major bonus is that the somatic cell that is reprogrammed can be collected from anyone, regardless of age, gender, or disease state. This means that iPSCs can be produced from a huge range of people, including those with genetic diseases, and the resulting stem cells will hold all of the genetic information of that person. This is particularly useful when using stem cells in experiments to try and understand what exactly is going wrong in a diseased cell. Not only do iPSCs sidestep some of the ethical questions at the forefront of embryonic stem cell research, but they present a cell type that is undoubtedly one of the most important tools for research and medicine in recent years. As with ESCs, iPSCs are not perfect and there are limitations to their potential, but they have garnered huge global interest, and are quickly advancing as a regenerative therapy and research tool.
