Of Mice and Men…and Stem Cells

Stem cell research has been a major point of contention, for the right and wrong reasons, over the past decade.  The arguments both for and against the use of embryonic stem cells spring from the greatest quality of humanity — value for human life. The development of stem cells from sources other than embryos bodes well for a resolution between the two conflicting points of view on this heavily debated topic.

Stem cells, cells not differentiated into a particular role, represent a potentially powerful medical tool.  They are defined by the unique abilities to differentiate into multiple cell types and continually divide.  Somatic stem cells (also called adult stem cells) are found within most of an organism’s tissues throughout its life; however these cells are multipotent, only capable of forming a specific set of cell types.  Embryonic stem cells present a much more attractive option from a medical prospective because they are pluripotent, having the ability to become a wide range of cell types.

Problems arise from the fact that pluripotent stem cells are exclusively found in embryos.  Obtaining embryonic stem cells (ESC) requires the destruction of unused embryos from in vitro fertilization techniques (the idea that stem cell research depends on abortion is mistaken).  For some, the source of the cells represents a moral bridge that cannot be crossed, while others argue that science should do whatever it can to save lives.  Despite the benefit embryonic stem cells could offer medically, the moral controversy slowed and, eventually, stopped implementation of the technology.  The social and political climate compelled scientists to seek alternative sources of pluripotent cells.

Such a potential solution was developed in 2006 by a group of Japanese researchers who managed to coax mouse skin cells into becoming pluripotent stem cells.  The technique involved using a genetically reprogrammed retrovirus to force the skin cells to create several proteins that are characteristic of embryonic stem cells.  The inserted genes encoded transcription factors, such as Oct 3/4 and Sox family genes, which control what other genes are turned on or off.  The resulting cells, dubbed induced pluripotent stem cells (iPS), mirrored the morphology, growth rate and other general characteristics of embryonic stem cells.  The same strategy created human iPS in 2007, giving stem cell research a second chance.

However, not all researchers were convinced that iPS cells are truly pluripotent.  Embryonic stem cells are clearly capable of developing into all cell types, as evidenced by normal embryo development.  iPS cells may look and act like embryonic stem cells, but until it could be shown that an entire organism can develop from one, their pluripotency was debatable.  July 2009 started poorly for iPS proponents, with published research showing that there are slight differences in the genes expressed in induced pluripotent stem cells and embryonic stem cells.  However, later in the month, two teams of Chinese scientists established the pluripotency of iPS cells by using them to grow entire mice.

Both labs verified the cells could differentiate into any tissue or cell type by tricking them molecularly into growing as an embryo would.  The techniques involved were difficult and inefficient, requiring numerous tries before success was achieved.  This experimentation was done solely as a proof of the iPS potency, with all researchers involved voicing the immorality of using iPS cells for human reproduction. 

With the versatility of iPS cells confirmed and social controversy avoided, research using them should surge forward.  While there are no magic bullets in medicine, the applications of stem cells are close to limitless.  From mediating heart repair to helping scientists better understand cancer, stem cells have the power to become an essential tool in modern medicine.  While somatic stem cells provide numerous opportunities, access to pluripotent cells that don’t invite moral conflict will open the door to accessing the depth of that potential.

For more information:

Stem cell basics from NIH :

http://stemcells.nih.gov/info/basics/

Interactive tutorials from the University of Utah :

http://learn.genetics.utah.edu/content/tech/stemcells/