By Dr. Harold Rex Greene
For over a decade, controversy has surrounded proposals to use human embryos to treat diseases such as Parkinson's and Alzheimer's. Scientists have publicly spoken about the "promise" of embryonic stem cells to cure diseases. That "promise" is based on the oft-repeated statement that human embryonic stem cells (often described as "master cells" or "blank cells") possess the unique ability to form all cell types in the human body.
In California we're facing an initiative to amend the state constitution and create a constitutional "right" to perform stem cell research. Under the terms of Proposition 71 - - The California Stem Cell Research and Cures Initiative - - the state would issue $3 billion in general obligation bonds to fund research that destroys human embryos that are "left over" from IVF, and embryos specially created for the purpose by cloning.
Many in the research community are enthusiastic supporters. While proponents pretend that the measure actually bans the use of funds for human cloning, in fact it merely constrains "human reproductive cloning" by not funding it. So-called "therapeutic cloning" would be made a constitutional right. It would not be banned, but would actually receive priority funding because it is not eligible for federal funds.
Both techniques produce cloned human embryos. With the latter, however, there is no intention to allow the birth of a human being.
This article will focus on the faulty science behind embryonic stem cell research which denies the astonishing complexity of embryonic development.
Many scientists have succumbed to a logical fallacy, based on a naive and simple-minded theory. From the obvious fact that embryonic cells eventually develop into all of the tissues in the body, they conclude that they can remove these cells and make them rebuild damaged, diseased organs in other people's bodies. To describe this exercise in science fiction they have hijacked the term "regenerative medicine."
But their belief is utterly without what scientists call proof of concept, that is, animal studies that confirm their theory. On the contrary, animal studies have gone on for nearly 20 years and proved quite disappointing.
To understand why requires a brief overview of the incredibly complicated messaging system that makes embryonic cells usually go where they need to go and do what they're supposed to do.
During the first eight weeks the embryo changes from a single-celled zygote to a fully formed fetus. The study of embryology demonstrates an amazing choreography, like a symphony with millions of musicians in constant motion, adding more and more players, who change instruments yet never miss a beat.
A variety of signals direct cells to grow, migrate, differentiate, and spontaneously die. Some cells serve only as temporary placeholders while others take up permanent residence at their target organ. Some of the messages that determine embryonic development are intrinsic - - locked in the genetic code. Some are extrinsic - - physical, chemical, and electrical messages between adjacent cells jostling for position.
Much of our genetic code is dedicated to embryonic development and shuts down once a fetus has formed. The reactivation of these genes in the wrong time and place can be disastrous. Mutations in a single cell, allowing such reactivation, can result in malignancies.
Cloning illustrates this complexity. In cloning, the nucleus of a human ovum (egg) is removed and replaced with the nucleus from a body cell. The theory is that the surrounding cytoplasm will "reprogram" the replacement nucleus to revert to its former embryonic functions.
However, most of the time this fails because the transferred nucleus has already been programmed to serve its adult function. This role is by no means simple. For example, as a cheek cell it must constantly replace the lining of the mouth, maintaining a perfect balance of cell growth and death.
It is nothing short of hubris to believe that we can rip embryonic cells out of their normal context in the embryo, inject them into a "host" body, and expect them to perform perfectly every time.
On occasion, a cloned animal embryo develops that can be implanted in a uterus and grown to term. Sometimes bizarre monsters develop that kill the host mother. But a few cloned animals do make it to term - - most, if not all, carrying severe defects. If that same cloned embryo is destroyed for stem cells instead, those stem cells will carry severe defects - - defects that arise from short-circuiting normal development and activating a human being's genetic code all at once.
Cells obtained from blastocysts (one-week-old embryos) created in IVF fare little better. The tissue cultures into which these cells are placed lack the features of the embryonic environment which had orchestrated the development of the cells. Wrenched out of this setting, the cells spontaneously differentiate into precursors of adult tissues: kidneys, hearts, nerves, or, worst of all, tumors. No one would dare inject them into a person. Hence, more and more embryonic stem "lines" will be needed just for basic research.
In short, scientists have failed to demonstrate that they can remove cells from their rightful place in a human embryo and make them perform according to their wishes. There is strong evidence suggesting that we will never be able to do this.
The fallacy of embryonic stem cell research collapses on closer examination. For example, in a patient with Lou Gehrig's disease (amyotrophic lateral sclerosis
or ALS), an immune reaction destroys the nerves in the brain and spinal cord that control muscles. Such a patient could receive embryonic nerve cells that would supposedly replace the dead nerves.
To create genetically matched stem cells, proponents propose to create cloned embryos, which, in theory, would not be rejected. But there are numerous problems.
As recent experiments in South Korea demonstrate, to create cloned embryos, dozens of eggs (if not hundreds more) will be needed, no doubt purchased from women who've undergone super-ovulation. From those eggs a few embryos will successfully develop via nuclear transfer (cloning), which means that identical twins will be created for the purpose of salvaging body parts.
The patient then receives many cloned embryonic cells, virtually all of which most likely have significant genetic defects. Remember, if a single cell misfires, the result of the experiment could be an artificial cancer. Moreover, if the cells miraculously fail to degenerate into cancer cells, other problems remain.
Lou Gehrig's disease has a rapid course, but it takes nerves years to grow back. Meanwhile the disease is still attacking the nervous system and the injected cells. In other words, before this approach could hope to replace the nerves lost in ALS, we would first have to correct the problem that makes the body attack its own nerve cells in the first place.
Why engage in this Faustian bargain of destroying human life for the benefit of others? The truth is that biotech entrepreneurs and ambitious scientists hope to profit from mass-produced cellular therapies at taxpayers' expense. To bolster their feeble theory they make vastly exaggerated claims and cite heart-rending testimonials in lieu of scientific proof.
Sadly, all this is unnecessary. Adult stem cells (including cord blood) already are a 30-year success story. They've gone through natural embryonic development in the patient's own body, and have preserved the ability to self-renew and proliferate as needed.
Recent experiments have even shown that transplanted adult bone marrow stem cells integrate quite nicely into other organs and tissues (heart and brain, for example). They are simply "switching jobs."
The embryonic stem cell entrepreneurs know their venture is extremely speculative. What they don't realize is that they are actually building the equivalent of a 21st century Titanic.
The fact remains that embryonic cells are likely to perform their natural role only in the context of the intact, developing embryo, not as so many harvested crops. Our public resources should be directed towards the development of therapies that have a chance to succeed and carry no moral baggage - - adult and cord-blood stem cells.
Dr. Harold Rex Greene is medical director of the Dorothy E. Schneider Cancer Center in San Mateo, California, clinical professor at USC-Keck School of Medicine, and consultant to the Council on Ethical Affairs of the California Medical Association.