A Brief History of Stem Cells

A recent scientific report marks a landmark in stem cell research. Scientists writing in the journal Development described their successful creation of induced pluripotent stem cells from skin cells. The mouse-derived skin cells Epi-stem cells (as in epidermal) have the ability to continually divide, but are specialized to create only skin.

This in itself is not new, but the researchers were able to complete their experiments without the use of viruses. Until now, viral vectors have been the only method  capable of inserting the necessary pluripotency inducing genes into animal cells. Because the viruses are made up of foreign DNA, their use adds a level of uncertainty to the potential therapeutic use of induced stem cells.

Nobody wants to see potentially deadly effects occur as the result of the foreign DNA — being foreign it is uncertain what kind of things could happen. So, getting rid of the viruses is essential if we are going to see induced stem cells move beyond the realm of the theoretical and into application.

This is a big step. Next we will have to see the methodology repeated in primates and then in humans. And, from there we will have to wait and see if the virus-free induced human stem cells of the future are really capable of becoming any type of tissue. There is a lot of work still to be done, but I wouldn’t be surprised if we don’t see the required evidence appearing in the news within the next year.

It was just 2006 when Japanese researchers used viruses to induce the first pluripotent stem cells from mouse cells. It took another year for them to reduce the errors present in the methodology, and get induced stem cells that could produce viable chimeras.

In November of 2007,  the first human induced pluripotent stem cells were created. The teams working on the problem felt that the use of viruses was still too dangerous as the viral DNA often led to the development of tumors.

Late in 2008, the news broke that induced pluripotent stem cells had been created with an adenovirus instead of a retrovirus, and later with the use of a plasmid. Neither of these new vectors are known to integrate foreign DNA into the target genome.

In December of 2008, skin cells from primates were induced to become pluripotent stem cells capable of becoming a number of different cell types. And, just two weeks ago researchers reported inducing human skin cells into pluripotent stem cells.

The most recent study uses a piece of DNA called a transposon to insert the critical DNA for creating pluripotent stem cells into target regions of the genome. This is an exciting development since the transposon used can be species specific, and take us far away from the use of foreign viral bits.

I’m excited to see where the future of this research will take us.

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