The creation and characterization of induced pluripotent stem cells (iPS cells) has been an important component of recent stem cell research. Since Fall 2007 there has been rapid progress with regarding iPS cells. But this new form of pluripotent cells is qualitatively and quantitatively different from embryonic stem cells (ESCs). It is critically important to continue ESC research, even if iPS cells prove to be able to develop into tissues suitable for therapy and transplantation. Sources of ESCs are a contentious and critical issue.

Many are opposed to the creation of embryos for research purposes. Embryos are destroyed in the process of obtaining ESCs, and such research is vehemently opposed by those who believe that destruction of embryos is murder. There are many counter-arguments to this claim. For example, human sexual reproduction normally involves the loss of anywhere from 40 to 70% of early-stage embryos. In other words, embryos are destroyed consistently as a natural part of human reproduction. Some embryos fail to implant in the uterus, others implant but fail to thrive, and others may be rejected (i.e., killed) by the mother’s body. Opponents of stem cell research do not also advocate the cessation of human sexual reproduction, so their position on embryo “murder” may have logical inconsistencies.

We live in a pluralistic society and need to respect the morals and ethics of various minority viewpoints. So we may choose not to create embryos for research. Another likely source of embryos is the vast numbers of embryos remaining after in vitro fertilization (IVF) procedures. More than 100,000 IVF procedures are performed annually in the United States. Typically more embryos are created than are implanted in the potential mother’s uterus.

The leftover embryos are frozen for possible later use by the couple, donated for use by another couple, or destroyed. These so-called “spare” embryos could be useful in many aspects of stem cell (SC) research. The validity of an ethical distinction between use of embryos created specifically for research purposes and spare embryos originally created for IVF procedures has been debated for more than a decade.

Many U.S. Senators, including those who oppose abortion, are in favor of using spare embryos for SC research. In 2001 Senators Arlen Specter, Strom Thurmond, Olympia Snowe, Kay Bailey Hutchinson, and Orrin Hatch sent a letter to President George W. Bush urging him to “support legislation which would remove the existing ban on the use of Federal funds to derive stem cells from embryos”. The Senators were specifically urging the use of the “many excess embryos created for the purpose of in vitro fertilization” for SC research. [Congressional Record, S9118, September 5, 2001]

New National Institute of Health (NIH) guidelines, effective July 7, 2009, approve Federal NIH funding for research using embryos “that were created using in vitro fertilization for reproductive purposes and were no longer needed for this purpose”. [National Institute of Health Guidelines on Human Stem Cell Research - http://stemcells.nih.gov/policy/2009guidelines.htm, accessed 1-6-10.

President Obama’s administration has enabled ESC research to begin moving forward. In addition to ongoing moral and ethical issues, many scientific issues persist. For example, spare embryos have been frozen for varying periods of time. They may contain genetic defects that made them unsuitable for implantation. Most importantly, tissues derived from spare embryos will not be an immunologically match for the potential recipient. Graft-versus-host reactions are a key consideration. Immunosuppressive drugs would still be necessary for such therapies and transplants. Research on embryos created from host tissues remains a necessity.

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