As a subject of research, an unusual degree of consensus appears to exist among scientists, politicians and the public about human embryos being deserving of special considerations. But what those special considerations should be is less clear. And this is where the subject becomes contentious and opinions diverge because, somewhat surprisingly, what really represents a human embryo has so far not been resolved.
"Prior to implantation, embryos must be given a different level of reverence than after implantation."
In 2002, Howard W. Jones Jr., widely considered the "father" of in vitro fertilization (IVF) in the U.S., argued in a widely acclaimed article titled "What is an embryo?" that a precondition for the definition of a human embryo was successful implantation. Only once implantation established a biological unit between embryo and mother, could a relatively small number of human cells be considered a human embryo.
Because he felt strongly that human embryos, indeed, deserve special considerations, and should receive those during IVF, he pointed out that, even inside a woman's body, most human embryos (in contrast to other species) never implant and, therefore, are never given a chance at human life. Consequently, he reasoned that prior to implantation, embryos must be given a different level of reverence than after implantation.
"One cannot help but wonder about the fog of misconceptions and misrepresentations that still surrounds what an embryo is."
This difference, he felt, should also be reflected in scientific language, proposing that embryos prior to implantation in daily IVF practice be called "pre-embryos," with the term "embryo" reserved for post-implantation-stage embryos. Then still unknown to Jones, recent research findings support this viewpoint, since genetic profiles of pre- and post-implantation stage embryos greatly differ.
In an analogy to nature, which in humans allows implantation of only a small minority of naturally generated pre-embryos, IVF centers around the world routinely discard large numbers of pre-embryos, judged inadequate for producing normal pregnancies. Jones' suggestion that only post-implantation embryos should be considered embryos deserving of special considerations, therefore, not only appears prescient and considerate of current IVF practices, but grounded in scientific reality. One, therefore, cannot help but wonder about the fog of misconceptions and misrepresentations that still surrounds what an embryo is.
"Much of the regulatory environment surrounding research on human embryos is guided by emotions rather than science and logical thinking."
In 1984, a British ethics committee issued the Warnock Report, which still today prohibits scientists worldwide from studying human embryos in a lab beyond 14 days from fertilization or past formation of the so-called primitive streak, whichever comes first. Well-meaning in its day, its intent was to apply special considerations to human pre-embryos by protecting them from the potential of "feeling pain," once the primitive streak arose on day-15 of development. Formation of the primitive streak signifies a process known as gastrulation, when a subset of cells from the inner cell mass of the pre-embryo are transformed into the three germ layers that comprise all tissues of the developing embryo: The ectoderm, which gives rise to the nervous system; the mesoderm, which gives rise to the circulatory system, muscle, and kidneys; and the endoderm which gives rise to the interior lining of the digestive and respiratory tracts, among other tissues.
That pre-embryos may feel pain at that stage of development was far-fetched in 1984; in view of what we have learned about early human embryology in the 33 years since, it remains untenable today. And, yet, scientists all over the world remain bound by the ethical constraints imposed by the Warnock Report.
A similar ethical paradox exists today for guidelines affecting huge numbers of so-called "abandoned" cryopreserved embryos, often stored ad infinitum in IVF centers all over the world. These are pre-embryos, whose "parents" are no longer responsive to queries from their IVF centers. Current U.S. guidelines allow the disposal of such pre-embryos but prohibit their use in research that may benefit mankind. One, however, wonders whether disposal of huge numbers of abandoned embryos is really more ethical than their use in potentially life-saving human research?
That much of the regulatory environment surrounding research on human embryos is, indeed, guided by emotions rather than science and logical thinking, is also demonstrated by recently expressed concern about so-called "artificial" or "synthetic" embryos. Though both of these terms suggest impending ability to create human embryos from synthetic building blocks, this is not what these terms are meant to describe (such abilities also are not on the horizon). They also do not describe abilities to create gametes (i.e., eggs and sperm) from somatic cells by reprogramming adult peripheral cells, which has already been successfully done in mice by Japanese investigators, leading to the creation of healthy embryos and births and three generations of healthy pubs. Such an approach is at least conceivable as an upcoming infertility treatment.
"A team of biologists and engineers at the University of Michigan recently received media attention after creating organoids from embryonic stem cells that resembled human embryos."
What all of this noise is really about is the discovery that, as several Rockefeller University investigators recently noted, "Cells have an intrinsic ability to self-assemble and self-organize into complex and functional tissues and organs." Investigators have taken advantage of this ability by creating in the lab so-called "organoids" from accumulations of individual embryonic stem cells. They are defined by three characteristics: (i) they contain a variety of cell types and tissue layers, all typical for a given organ; (ii) these cells are organized similarly to their organization in a specific organ; and (iii) the organoid mimics functions of the organ.
Several other biologists from the Cincinnati Children Hospital Medical Center recently noted that in the last five years, quite a variety of human stem cell-derived organoids, including all three germ layers, have been generated by different research groups around the world, thereby establishing new human model systems that can be used outside the body, in a dish, to investigate otherwise difficult-to-approach organs. Interestingly, they can also be used to investigate early stages of human embryological development.
A team of biologists and engineers at the University of Michigan recently received media attention after creating organoids from embryonic stem cells that resembled human embryos and, therefore, were given the name "embroids." Though clearly not embryos (the only thing they had in common with human embryos were cell types), they were nevertheless awarded in at least one article the identity of "artificial embryos," which "no one knows how to handle." As Howard Jones so correctly noted, with the word embryo often comes undeserved reverence.
"Any association with the term "embryo" should be avoided; it is not only misleading and irresponsible but scientifically incorrect."
Artificial embryos, therefore, do not exist. Organoids that resemble embryos (i.e., "embroids"), while potentially very useful research objects in studies of early human embryonic cell organization and lineage development, are not embryos--not even pre-embryos. Special considerations for "artificial" or "synthetic" embryos, as recently advocated by some scientists, therefore, appear ethically undeserved. How misdirected and forced some of these efforts are is probably best demonstrated by a recent publication in which a group of Harvard University investigators proposed the term "synthetic human entities with embryo-like features" or SHEEFS" in place of "organoids." Preferably, however, in describing these laboratory-created entities, any association with the term "embryo" should be avoided. It is not only misleading and irresponsible but scientifically incorrect.
Clinical reproductive medicine and reproductive biology, for valid ethical reasons, but also because of myths, misperceptions and, sometimes, outright misrepresentations of facts for political reasons, are under more public scrutiny than most other science areas. Yet, at least in the realm of biomedical research, nothing appears more important than better understanding the first few days of human embryo development. A recent study involving genetic editing of human embryos, reported by British investigators in Nature, once again confirmed what biologist have known for some time: No animal model faithfully recapitulates most of human developmental origins. The most important secrets nature still has to tell us, will not be revealed through mouse or other animal studies. We will discover them only through the study of early-stage human embryos – and we, therefore, should not limit the use of lab-grown organoids to help further that research.
Understanding early human development "will not only greatly enhance the biological understanding of our species; but also will open groundbreaking new therapeutic options in all areas of medicine."
As Howard Jones intuitively noticed, words matter. Appropriate and uniformly accepted definitions and terms are not only essential for scientific communications but, within the context of human reproduction, often elicit strong emotional reactions, and are easily misappropriated by those opposed to most interventions into human reproduction.
Who does not recall the early days of IVF in the late 1970s, when even reputable news outlets raised the specter of Frankenstein monsters created through the IVF process? Millions of IVF births later, a Nobel Prize in Medicine and Physiology was in 2010 finally awarded to the biologist Robert Edwards who, together with the gynecologist Patrick Steptoe, reported the first live birth through IVF on July 25, 1978. Many more awards are still waiting for recipients who through the study of early human embryo development will discover how cell fate is determined and cells acquire highly specific functions; how rapid cell proliferation takes place and, when required, stops; why chromosomal abnormalities are so common in early stage embryos and what their function may be.
Those who will discover these and many other important answers, will not only greatly enhance the biological understanding of our species; but also will open groundbreaking new therapeutic options in all areas of medicine. Learning how to control cell proliferation, for example, will likely revolutionize cancer therapy; I started my research career in biology with a study published in 1980 of "common denominators of pregnancy and malignancy." If regulatory prohibitions are not allowed to interfere in rapidly progressing research opportunities involving organoids and pre-embryos, we will, finally, see the circle closing, with the most rewarding benefits for mankind ever achieved through biological research.
Editor's Note: Read a different viewpoint here written by one of the world's top experts on the ethics of stem cell research.
In November 2020, messenger RNA catapulted into the public consciousness when the first COVID-19 vaccines were authorized for emergency use. Around the same time, an equally groundbreaking yet relatively unheralded application of mRNA technology was taking place at a London hospital.
Over the past two decades, there's been increasing interest in harnessing mRNA — molecules present in all of our cells that act like digital tape recorders, copying instructions from DNA in the cell nucleus and carrying them to the protein-making structures — to create a whole new class of therapeutics.
Scientists realized that artificial mRNA, designed in the lab, could be used to instruct our cells to produce certain antibodies, turning our bodies into vaccine-making factories, or to recognize and attack tumors. More recently, researchers recognized that mRNA could also be used to make another groundbreaking technology far more accessible to more patients: gene editing. The gene-editing tool CRISPR has generated plenty of hype for its potential to cure inherited diseases. But delivering CRISPR to the body is complicated and costly.
"Most gene editing involves taking cells out of the patient, treating them and then giving them back, which is an extremely expensive process," explains Drew Weissman, professor of medicine at the University of Pennsylvania, who was involved in developing the mRNA technology behind the COVID-19 vaccines.
But last November, a Massachusetts-based biotech company called Intellia Therapeutics showed it was possible to use mRNA to make the CRISPR system inside the body, eliminating the need to extract cells out of the body and edit them in a lab. Just as mRNA can instruct our cells to produce antibodies against a viral infection, it can also teach them to produce the two molecular components that make up CRISPR — a guide molecule and a cutting protein — to snip out a problem gene.
"The pandemic has really shown that not only are mRNA approaches viable, they could in certain circumstances be vastly superior to more traditional technologies."
In Intellia's London-based clinical trial, the company applied this for the first time in a patient with a rare inherited liver disease known as hereditary transthyretin amyloidosis with polyneuropathy. The disease causes a toxic protein to build up in a person's organs and is typically fatal. In a company press release, Intellia's president and CEO John Leonard swiftly declared that its mRNA-based CRISPR therapy could usher in a "new era of potential genome editing cures."
Weissman predicts that turning CRISPR into an affordable therapy will become the next major frontier for mRNA over the coming decade. His lab is currently working on an mRNA-based CRISPR treatment for sickle cell disease. More than 300,000 babies are born with sickle cell every year, mainly in lower income nations.
"There is a FDA-approved cure, but it involves taking the bone marrow out of the person, and then giving it back which is prohibitively expensive," he says. It also requires a patient to have a matched bone marrow done. "We give an intravenous injection of mRNA lipid nanoparticles that target CRISPR to the bone marrow stem cells in the patient, which is easy, and much less expensive."
Meanwhile, the overwhelming success of the COVID-19 vaccines has focused attention on other ways of using mRNA to bolster the immune system against threats ranging from other infectious diseases to cancer.
The practicality of mRNA vaccines – relatively small quantities are required to induce an antibody response – coupled with their adaptable design, mean companies like Moderna are now targeting pathogens like Zika, chikungunya and cytomegalovirus, or CMV, which previously considered commercially unviable for vaccine developers. This is because outbreaks have been relatively sporadic, and these viruses mainly affect people in low-income nations who can't afford to pay premium prices for a vaccine. But mRNA technology means that jabs could be produced on a flexible basis, when required, at relatively low cost.
Other scientists suggest that mRNA could even provide a means of developing a universal influenza vaccine, a goal that's long been the Holy Grail for vaccinologists around the world.
"The mRNA technology allows you to pick out bits of the virus that you want to induce immunity to," says Michael Mulqueen, vice president of business development at eTheRNA, a Belgium-based biotech that's developing mRNA-based vaccines for malaria and HIV, as well as various forms of cancer. "This means you can get the immune system primed to the bits of the virus that don't vary so much between strains. So you could actually have a single vaccine that protects against a whole raft of different variants of the same virus, offering more universal coverage."
Before mRNA became synonymous with vaccines, its biggest potential was for cancer treatments. BioNTech, the German biotech company that collaborated with Pfizer to develop the first authorized COVID-19 vaccine, was initially founded to utilize mRNA for personalized cancer treatments, and the company remains interested in cancers ranging from melanoma to breast cancer.
One of the major hurdles in treating cancer has been the fact that tumors can look very different from one person to the next. It's why conventional approaches, such as chemotherapy or radiation, don't work for every patient. But weaponizing mRNA against cancer primes the immune cells with the tumor's specific genetic sequence, training the patient's body to attack their own unique type of cancer.
"It means you're able to think about personalizing cancer treatments down to specific subgroups of patients," says Mulqueen. "For example, eTheRNA are developing a renal cell carcinoma treatment which will be targeted at around 20% of these patients, who have specific tumor types. We're hoping to take that to human trials next year, but the challenge is trying to identify the right patients for the treatment at an early stage."
Repairing Damaged mRNA
While hopes are high that mRNA could usher in new cancer treatments and make CRISPR more accessible, a growing number of companies are also exploring an alternative to gene editing, known as RNA editing.
In genetic disorders, the mRNA in certain cells is impaired due to a rogue gene defect, and so the body ceases to produce a particular vital protein. Instead of permanently deleting the problem gene with CRISPR, the idea behind RNA editing is to inject small pieces of synthetic mRNA to repair the existing mRNA. Scientists think this approach will allow normal protein production to resume.
Over the past few years, this approach has gathered momentum, as some researchers have recognized that it holds certain key advantages over CRISPR. Companies from Belgium to Japan are now looking at RNA editing to treat all kinds of disorders, from Huntingdon's disease, to amyotrophic lateral sclerosis, or ALS, and certain types of cancer.
"With RNA editing, you don't need to make any changes to the DNA," explains Daniel de Boer, CEO of Dutch biotech ProQR, which is looking to treat rare genetic disorders that cause blindness. "Changes to the DNA are permanent, so if something goes wrong, that may not be desirable. With RNA editing, it's a temporary change, so we dose patients with our drugs once or twice a year."
Last month, ProQR reported a landmark case study, in which a patient with a rare form of blindness called Leber congenital amaurosis, which affects the retina at the back of the eye, recovered vision after three months of treatment.
"We have seen that this RNA therapy restores vision in people that were completely blind for a year or so," says de Boer. "They were able to see again, to read again. We think there are a large number of other genetic diseases we could go after with this technology. There are thousands of different mutations that can lead to blindness, and we think this technology can target approximately 25% of them."
Ultimately, there's likely to be a role for both RNA editing and CRISPR, depending on the disease. "I think CRISPR is ideally suited for illnesses where you would like to permanently correct a genetic defect," says Joshua Rosenthal of the Marine Biology Laboratory in Chicago. "Whereas RNA editing could be used to treat things like pain, where you might want to reset a neural circuit temporarily over a shorter period of time."
Much of this research has been accelerated by the COVID-19 pandemic, which has played a major role in bringing mRNA to the forefront of people's minds as a therapeutic.
"The pandemic has really shown that not only are mRNA approaches viable, they could in certain circumstances be vastly superior to more traditional technologies," says Mulqueen. "In the future, I would not be surprised if many of the top pharma products are mRNA derived."
"Making Sense of Science" is a monthly podcast that features interviews with leading medical and scientific experts about the latest developments and the big ethical and societal questions they raise. This episode is hosted by science and biotech journalist Emily Mullin, summer editor of the award-winning science outlet Leaps.org.