Smart Money Is on Adult Stem Cells, but Some Scientists Still Lust after Embryos
When adult stem cells do the job, why are some scientists tinkering with human embryos?
Stem cells have been a hot topic for nearly two decades now. Hopefully the terminology has become clear. Stem cells are cells that can grow into any tissue type. Embryonic stem cells (ES) are derived from fertilized embryos that, if implanted, would grow into an adult. Adult stem cells (AS) reside in different tissues of adults, where they can regenerate the cells of that particular tissue. Induced pluripotent stem cells (iPS) are tissue cells that have been reprogrammed into a stem-like state, where they can grow into most tissue types. Totipotent means able to differentiate into all tissue types; pluripotent means able to differentiate into most tissue types. The primary advantage of human adult and iPS stem cells is that they do not require killing a human embryo; therefore, they are ethically superior. But can they do as good a job as embryonic stem cells? These articles share recent developments.
First, we need to understand the “stem cell paradigm.” Science Magazine asks, “What is an adult stem cell?” As with many definitions in science, the boundaries are often fuzzy. The type specimen for a stem cell was the “hematopoietic stem cell” (HSC) living in bone marrow. It seemed almost magical that it could produce all the different blood cell types, and yet stay intact in a permanent state of self-renewal. Hans Clevers tries to insert evolution into the paradigm:
The HSC’s ability to “self-renew” as well as to proceed down hierarchical differentiation pathways involves a rigidly choreographed flow of events. The HSC paradigm currently serves as a template to interpret experimental observations on any other mammalian tissue. Yet, it is not obvious why evolution would have come up with the very same solution for the renewal of all tissues. Attempts to fit observations on solid tissues into the HSC hierarchy mold have led to confusing theories, terminologies, experimental approaches, and heated debates, many of which remain unresolved. Organs differ in size, architecture, and function, and are subject to markedly different biological and physical challenges. It therefore appears plausible that tissues, with their different regenerative demands, have evolved different ways to restore cell numbers.
This appears to be quibbling about definitions. If a cell can regenerate the cells of its tissue niche, then it should be called a stem cell, even if it differs from the stem cell of another niche. As for evolution, Clevers only tells us what seems “plausible” to him. Others may find it more plausible to suspect clever design, based on our uniform experience, when any “rigidly choreographed flow of events” is observed.
Adult and iPS Stem Cell News
iPS same as ES: Cambridge researchers “have found the strongest evidence to date that human pluripotent stem cells—cells that can give rise to all tissues of the body—will develop normally once transplanted into an embryo” (Medical Xpress). They appear virtually totipotent, in other words. As such, they are likely to be safe and effective.
Faster, better, cheaper: An easier way to produce stem cells from normal cells by putting the squeeze on them, PhysOrg claims. It sounds too good to be true; hopefully this will not turn out to be another STAP-like controversy (1/30/14).
Stem cells are now at the cutting edge of modern medicine. They can transform into a cells of different organs, offering new ways to treat a range of injuries and diseases from Parkinson’s to diabetes. But producing the right type of stem cells in a standardized manner is still a serious challenge. EPFL scientists have now developed a gel that boosts the ability of normal cells to revert into stem cells by simply “squeezing” them into shape. Published in Nature Materials, the new technique can also be easily scaled up to produce stem cells for various applications on an industrial scale.
iPS are compatible: One question was whether iPS cells would retain some epigenetic memory of their source, and thus be incompatible if implanted into someone else’s tissues. That concern has been alleviated by results found at the University of Helsinki, PhysOrg says. It’s the donor’s genotype that matters, not the source tissue it came from. Here are the key findings:
The results were unambiguous: several different indicators showed that the type of original cell made no difference when the stem cell was fully reprogrammed.
Says Professor Timo Otonkoski from the University of Helsinki: “It is obvious that pluripotent stem cells derived from different cell types are fully equal. These results are highly significant to biobanks, as this way one collection can feature different source cells, and previously stored living cell samples remain useful for iPS cell production.”
What was surprising was how different the iPS cells derived from different individuals were. The genotype of the donor obviously shapes the differentiation behaviour of the stem cell.
iPS produces pancreatic cells: Medical Xpress reports that iPS cells derived from human skin showed themselves capable of producing pancreatic cells that can secrete insulin. UCSF researchers also came up with a scalable, sustainable method to produce the cells. “Now we can generate virtually unlimited numbers of patient-matched insulin-producing pancreatic cells,” they said, bringing personalized cell therapy a step closer for patients with diabetes.
Skin cells into serotonin: Another victory for iPS cells took place at the University of Wisconsin-Madison, where researchers used reprogrammed skin cells create “a specialized nerve cell that makes serotonin, a signaling chemical with a broad role in the brain” (Medical Xpress). Serotonin is involved in “emotions, sleep, anxiety, depression, appetite, pulse and breathing.” One of the researchers expressed altruistic motives for the work. ” I don’t want to just make a publication in a scientific journal. I want our work to affect human health, to improve the human condition.”
Sacrificing Embryos for Science
Despite the successes outlined above, some researchers are intent on continuing to experiment with human embryos, even with the knowledge that doing so poses ethical challenges.
Pooled for use: A “study” by the University of Edinburgh concludes that “[embryonic] stem cells that have been specifically developed for use as clinical therapies are fit for use in patients,” according to Science Daily.
Eyes on the prize: Another Science Daily article reports that Johns Hopkins researchers have demonstrated that ES cells in a dish that can be transformed into retinal ganglion cells. They have not yet actually treated anyone with glaucoma and other optic nerve diseases; it’s “just the beginning,” they say.
Embryo editor: The BBC News reports on a Dr. Kathy Niakin who is making the case to edit human embryos with the new CRISPR/Cas9 gene editing tool (see 6/05/15). Nothing is said about the ethical problems with this procedure. For those who want to think about the implications, Dr. Albert Mohler had some strong words for this “Brave New World” slippery slope in his daily Briefing for January 15. Even more alarming, PhysOrg says Josiah Zayner is making gene editing kits to allow do-it-yourselfers to “play God at the kitchen table,” genetically modifying anything they want to tinker with.
We need to be aware of what the mad scientists are up to. When will science ever learn that what they can do does not necessarily correlate with what they should do? That was a huge debate in the 1940s with the development of atomic weapons. The new genetic arsenal has potential for tremendous good as well as terrible evil. Science can do is’s but not oughts. The oughts need to come from morally-informed, righteous thinkers. We’ve already seen the terrible outcomes of viewing human flesh as a commodity. Whenever a human entity, be it embryonic, old or disabled, is no longer considered a person, watch out.