New Techniques for Producing Embryonic Stem Cells Without Destroying Embryos

It's groundbreaking science. Two different laboratories have published techniques for producing embryonic stem cells without destroying embryos in Nature science journal (not available online without subscription). One technique doesn't destroy embryos, but the other method does in a way.

While there has been some commendable work done in researching the possible applications of human adult stem cells for therapeutic use, the reality is that embryonic stem cells have more utility. The reason is their totipotency - their ability to differentiate and develop into a huge variety of cell types. In contrast, adult stem cells are committed - they develop into the type of cell in the tissue they are part of. So adult muscle stem cells will rebuild muscle tissue, adult blood cells will replenish the blood and so on. Adult stem cells thus are more limited in their application than embryonic stem cells, and harder to harvest and grow in culture. But to date harvesting or producing embryonic stem cells has meant the destruction of embryos - an unethical technique.

Now two techniques have been presented which claim to avoid the unwanted destruction of embryos in the production of embryonic stem cells. You can read about those techniques in these articles from New Scientist and Nature News.

The first technique, reported by Rudolf Jaenisch and Alexander Meissner of the Massachusetts Institute of Technology, is called ANT (altered nuclear transfer). Put simply, this is a variation of cloning - a donor cell is taken from a patient and has the nucleus removed. The nucleus is then transferred into a egg emptied of its own nucleus, and the egg develops into an embryo according to the blueprint of the patient's DNA. In the ANT technique a virus is introduced into the donor cell which blocks a gene essential for formation of placenta. So the ANT egg cannot implant in the womb. According to Jaenisch this removes the potential for the cell to become an embryo. But embryonic stem cells harvested from the "pseudo-embryo" that is grown can have the gene switched back on - by introducing an enzyme which destroys the virus. There are some obvious ethical problems here - as this technique would effectively be creating defective human embryos deliberately for the purpose of stem cell production. Put simply, an embryo is created but prevented from possible implantation in the uterus - so really it is the continued development of a human life which is deliberately thwarted. This is not a viable technique ethically as it is effectively creating a human embryo with a built in destruct mechanism.

The second technique, reported by Robert Lanza of Advanced Cell Technology in Worcester, Massachusetts, involves taking a single cell from an embryo without destroying it. The cell called a blastomere is taken from a morula, which is an embryo at a stage where it has a small number of cells. It's a technique similar to one used in IVF treatment when embryos are screend for genetic defects. Lanza's research was done with mouse morula at the 8-cell stage. One blastomere was removed, and the remaining 7-cell embryos were implanted in mice. The mice produced healthy offspring at the same rate as mice who were implanted with full 8-cell embryos.

The main disadvantage to Lanza's technique is that for human purposes the blastomeres would have to come from embryos from couples undergoing IVF. Technically, a blastomere can possibly be cultured to divide and form an embryo itself - so although no human embryos woud be destroyed in its harvesting, it could lead to the creation of embryos which are destroyed. Another issue raised is that the blastomere and resulting stem cells would not genetically match the patient receiving the cell transplant. I think that is a weaker argument. Previous research on Parkinsons disease has shown that fetal cells that did not genetically match patients were effective in remitting disease when transplanted into recipients. (Highly unethical but I mention it to make the argument against genetic matching). The most troublesome issue with Lanza's technique is the IVF connection. While it's true that the mice which received 7-cell embryos produced healthy offspring at the same rate as mice receiving 8-cell embryos, the actual normal birth number for the 7-cell embryo mice was 23 out of 47 implants - 50%. IVF is a technique dependent on the fact that some embryos will not be viable. And while the removal of a single blastomere does not change the rate of normal births in the embryos the blastomeres are removed from - it raises ethical questions about the source of the blastomeres. Removing a blastomere to produce embryonic stem cells doesn't destroy the embryo - but the embryo is part of a process in which it is not expected that all embryos will develop normally to term.

Lanza's research is promising, particularly when embryonic stem cells hold so much potential for the treatment of leukemias, neurological diseases, and other pathologies. Adult stem cell research has been hindered by the commitment of the cells to differentiate into specific types and the difficulty in finding the right cues to coax them into targeted differentiation outside of their normal pathway. But as promising as it appears, Lanza's technique is not entirely free of ethical inviability.

It is questionable as to whether or not either of these new techniques will get past the US Dickey Amendment which forbids federal funds being spent on experiments that endanger or destroy an embryo.

Hat Tip: Martin LaBar at Sun and Shield who has also discussed these techniques.