Save Those Teeth

Dentists usually discard wisdom teeth after they've been extracted -- but maybe they should start saving them; they just might be useful in make stem cells. Recently, a group of Japanese scientists made induced pluripotent stem cells (IPSCs) from the tooth pulp of extracted wisdom teeth. They used viruses to deliver stem cell factors to mesenchymal stromal cells isolated from the pulp of third molars. The resulting IPSCs were similar to embryonic stem cells.

In 2003, an NIH researcher, Sangtao Shi, extracted stem cells from his daughter's baby teeth. The stem cells grew in culture and could form bone when implanted into mice. Potentially, you could bank stem cells from your teeth for future use, but it would be an expensive process.

Maybe that's what the tooth fairy does with all those teeth?

Whether from embryos or adult tissues, stem cells are few. But many are needed for cell therapies. There have been ethical and political problems with using embryonic stem cells -- so if there were a way to get more stem cells from adults, it might be less controversial. Enter the IPSC.

Every cell in the body has the same genetic instructions. So what makes a heart cell different from a liver cell? The two cells express different sets of genes. Likewise, a stem cell turns on specific sets of genes to differentiate into another cell. So, is it possible to reprogram a differentiated cell so that it reverts back to a stem cell? In 2006, scientists did just that. They used a virus to deliver four stem cell factors into skin cells. The factors caused the differentiated stem cells to go into an embryonic-stem-cell-like state. The resulting cells, called induced pluripotent stem cells (IPSCs), shared many characteristics with human embryonic stem cells. The structures of IPSCs were similar, they expressed the same markers and genes, and they grew the same. And the researchers were able to grow the IPSCs into cell lines.

There are many more differentiated cells in the human body than stem cells, embryonic or adult. So, vast amounts of stem cells could be made from a patient's own differentiated cells, like skin cells. Making IPSCs does not involve embryos, so this would circumvent the ethical and political issues involved in stem cell research. However, making ISPSCs is a recent development, so scientists need to do more research before they can be used for therapies. First, we need to understand the "reprogramming" process better. And then we need to investigate whether IPSCs are just similar enough or are actually identical to embryonic stem cells. Current research is focused on these questions, but reprogramming cells to make IPSCs has great potential.

Now that you have a good idea of what stems cells are and how they work, let's see how they can be used to treat diseases.

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Induced Pluripotent Stem Cells (IPSCs) - HowStuffWorks