Regenerative medicine has come a long way, baby
The field of regenerative medicine had a shaky start. In 2002, when news spread about the first cloned animal, Dolly the sheep, a raucous debate ensued. Scary headlines and organized opposition groups put pressure on government leaders, who responded by tightening restrictions on this type of research.
Fast forward to today, and regenerative medicine, which focuses on making unhealthy tissues and organs healthy again, is rewriting the code to healing many disorders, though it’s still young enough to be considered nascent. What started as one of the most controversial areas in medicine is now promising to transform it.
Progress in the lab has addressed previous concerns. Back in the early 2000s, some of the most fervent controversy centered around somatic cell nuclear transfer (SCNT), the process used by scientists to produce Dolly. There was fear that this technique could be used in humans, with possibly adverse effects, considering the many medical problems of the animals who had been cloned.
But today, scientists have discovered better approaches with fewer risks. Pioneers in the field are embracing new possibilities for cellular reprogramming, 3D organ printing, AI collaboration, and even growing organs in space. It could bring a new era of personalized medicine for longer, healthier lives - while potentially sparking new controversies.
Engineering tissues from amniotic fluids
Work in regenerative medicine seeks to reverse damage to organs and tissues by culling, modifying and replacing cells in the human body. Scientists in this field reach deep into the mechanisms of diseases and the breakdowns of cells, the little workhorses that perform all life-giving processes. If cells can’t do their jobs, they take whole organs and systems down with them. Regenerative medicine seeks to harness the power of healthy cells derived from stem cells to do the work that can literally restore patients to a state of health—by giving them healthy, functioning tissues and organs.
Modern-day regenerative medicine takes its origin from the 1998 isolation of human embryonic stem cells, first achieved by John Gearhart at Johns Hopkins University. Gearhart isolated the pluripotent cells that can differentiate into virtually every kind of cell in the human body. There was a raging controversy about the use of these cells in research because at that time they came exclusively from early-stage embryos or fetal tissue.
Back then, the highly controversial SCNT cells were the only way to produce genetically matched stem cells to treat patients. Since then, the picture has changed radically because other sources of highly versatile stem cells have been developed. Today, scientists can derive stem cells from amniotic fluid or reprogram patients’ skin cells back to an immature state, so they can differentiate into whatever types of cells the patient needs.
In the context of medical history, the field of regenerative medicine is progressing at a dizzying speed. But for those living with aggressive or chronic illnesses, it can seem that the wheels of medical progress grind slowly.
The ethical debate has been dialed back and, in the last few decades, the field has produced important innovations, spurring the development of whole new FDA processes and categories, says Anthony Atala, a bioengineer and director of the Wake Forest Institute for Regenerative Medicine. Atala and a large team of researchers have pioneered many of the first applications of 3D printed tissues and organs using cells developed from patients or those obtained from amniotic fluid or placentas.
His lab, considered to be the largest devoted to translational regenerative medicine, is currently working with 40 different engineered human tissues. Sixteen of them have been transplanted into patients. That includes skin, bladders, urethras, muscles, kidneys and vaginal organs, to name just a few.
These achievements are made possible by converging disciplines and technologies, such as cell therapies, bioengineering, gene editing, nanotechnology and 3D printing, to create living tissues and organs for human transplants. Atala is currently overseeing clinical trials to test the safety of tissues and organs engineered in the Wake Forest lab, a significant step toward FDA approval.
In the context of medical history, the field of regenerative medicine is progressing at a dizzying speed. But for those living with aggressive or chronic illnesses, it can seem that the wheels of medical progress grind slowly.
“It’s never fast enough,” Atala says. “We want to get new treatments into the clinic faster, but the reality is that you have to dot all your i’s and cross all your t’s—and rightly so, for the sake of patient safety. People want predictions, but you can never predict how much work it will take to go from conceptualization to utilization.”
As a surgeon, he also treats patients and is able to follow transplant recipients. “At the end of the day, the goal is to get these technologies into patients, and working with the patients is a very rewarding experience,” he says. Will the 3D printed organs ever outrun the shortage of donated organs? “That’s the hope,” Atala says, “but this technology won’t eliminate the need for them in our lifetime.”
New methods are out of this world
Jeanne Loring, another pioneer in the field and director of the Center for Regenerative Medicine at Scripps Research Institute in San Diego, says that investment in regenerative medicine is not only paying off, but is leading to truly personalized medicine, one of the holy grails of modern science.
This is because a patient’s own skin cells can be reprogrammed to become replacements for various malfunctioning cells causing incurable diseases, such as diabetes, heart disease, macular degeneration and Parkinson’s. If the cells are obtained from a source other than the patient, they can be rejected by the immune system. This means that patients need lifelong immunosuppression, which isn’t ideal. “With Covid,” says Loring, “I became acutely aware of the dangers of immunosuppression.” Using the patient’s own cells eliminates that problem.
Microgravity conditions make it easier for the cells to form three-dimensional structures, which could more easily lead to the growing of whole organs. In fact, Loring's own cells have been sent to the ISS for study.
Loring has a special interest in neurons, or brain cells that can be developed by manipulating cells found in the skin. She is looking to eventually treat Parkinson’s disease using them. The manipulated cells produce dopamine, the critical hormone or neurotransmitter lacking in the brains of patients. A company she founded plans to start a Phase I clinical trial using cell therapies for Parkinson’s soon, she says.
This is the culmination of many years of basic research on her part, some of it on her own cells. In 2007, Loring had her own cells reprogrammed, so there’s a cell line that carries her DNA. “They’re just like embryonic stem cells, but personal,” she said.
Loring has another special interest—sending immature cells into space to be studied at the International Space Station. There, microgravity conditions make it easier for the cells to form three-dimensional structures, which could more easily lead to the growing of whole organs. In fact, her own cells have been sent to the ISS for study. “My colleagues and I have completed four missions at the space station,” she says. “The last cells came down last August. They were my own cells reprogrammed into pluripotent cells in 2009. No one else can say that,” she adds.
Future controversies and tipping points
Although the original SCNT debate has calmed down, more controversies may arise, Loring thinks.
One of them could concern growing synthetic embryos. The embryos are ultimately derived from embryonic stem cells, and it’s not clear to what stage these embryos can or will be grown in an artificial uterus—another recent invention. The science, so far done only in animals, is still new and has not been widely publicized but, eventually, “People will notice the production of synthetic embryos and growing them in an artificial uterus,” Loring says. It’s likely to incite many of the same reactions as the use of embryonic stem cells.
Bernard Siegel, the founder and director of the Regenerative Medicine Foundation and executive director of the newly formed Healthspan Action Coalition (HSAC), believes that stem cell science is rapidly approaching tipping point and changing all of medical science. (For disclosure, I do consulting work for HSAC). Siegel says that regenerative medicine has become a new pillar of medicine that has recently been fast-tracked by new technology.
Artificial intelligence is speeding up discoveries and the convergence of key disciplines, as demonstrated in Atala’s lab, which is creating complex new medical products that replace the body’s natural parts. Just as importantly, those parts are genetically matched and pose no risk of rejection.
These new technologies must be regulated, which can be a challenge, Siegel notes. “Cell therapies represent a challenge to the existing regulatory structure, including payment, reimbursement and infrastructure issues that 20 years ago, didn’t exist.” Now the FDA and other agencies are faced with this revolution, and they’re just beginning to adapt.
Siegel cited the 2021 FDA Modernization Act as a major step. The Act allows drug developers to use alternatives to animal testing in investigating the safety and efficacy of new compounds, loosening the agency’s requirement for extensive animal testing before a new drug can move into clinical trials. The Act is a recognition of the profound effect that cultured human cells are having on research. Being able to test drugs using actual human cells promises to be far safer and more accurate in predicting how they will act in the human body, and could accelerate drug development.
Siegel, a longtime veteran and founding father of several health advocacy organizations, believes this work helped bring cell therapies to people sooner rather than later. His new focus, through the HSAC, is to leverage regenerative medicine into extending not just the lifespan but the worldwide human healthspan, the period of life lived with health and vigor. “When you look at the HSAC as a tree,” asks Siegel, “what are the roots of that tree? Stem cell science and the huge ecosystem it has created.” The study of human aging is another root to the tree that has potential to lengthen healthspans.
The revolutionary science underlying the extension of the healthspan needs to be available to the whole world, Siegel says. “We need to take all these roots and come up with a way to improve the life of all mankind,” he says. “Everyone should be able to take advantage of this promising new world.”
Like any life-threatening medical condition that affects children, food allergies can traumatize more than just the patient. My wife and I learned this one summer afternoon when our daughter was three years old.
Emergency room visits for anaphylaxis in children more than doubled from 2010 to 2016.
At an ice cream parlor, I gave Samantha a lick of my pistachio cone; within seconds, red blotches erupted on her skin, her lips began to swell, and she complained that her throat felt funny. We rushed her to the nearest emergency room, where a doctor injected her with epinephrine. Explaining that the reaction, known as anaphylaxis, could have been fatal if left unchecked, he advised us to have her tested for nut allergies—and to start carrying an injector of our own.
After an allergist confirmed Sam's vulnerability to tree nuts and peanuts, we figured that keeping her safe would be relatively simple. But food allergies often come in bunches. Over the next year, she wound up back in the ER after eating bread with sesame seeds at an Italian restaurant, and again after slurping buckwheat noodles at our neighborhood Japanese. She hated eggs, so we discovered that (less severe) allergy only when she vomited after eating a variety of products containing them.
In recent years, a growing number of families have had to grapple with such challenges. An estimated 32 million Americans have food allergies, or nearly 10 percent of the population—10 times the prevalence reported 35 years ago. The severity of symptoms seems to be increasing, too. According to a study released in January by Food Allergy Research & Education (FARE), a Virginia-based nonprofit, insurance claims for anaphylactic food reactions rose 377 percent in the U.S. from 2007 to 2016.
Because food allergies most commonly emerge in childhood, these trends are largely driven by the young. An insurance-industry study found that emergency room visits for anaphylaxis in children more than doubled from 2010 to 2016. Peanut allergies, once rare, tripled in kids between 1997 and 2008. "The first year, it was 1 in 250," says Scott Sicherer, chief of pediatric allergy and immunology at New York City's Mount Sinai Hospital, who led that study. "When we did the next round of research, in 2002, it was 1 in 125. I thought there must be a mistake. But by 2008, it was 1 in 70."
The forces behind these dire statistics—as well as similar numbers throughout the developed world—have yet to be positively identified. But the leading suspects are elements of our modern lifestyle that can throw the immune system out of whack, prompting potentially deadly overreactions to harmless proteins. Although parents can take a few steps that might lessen their children's risk, societal changes may be needed to brighten the larger epidemiological picture.
Meanwhile, scientists are racing to develop therapies that can induce patients' hyped-up immune defenses to chill. And lately, they've made some big strides toward that goal.
A Variety of Culprits
In the United States, about 90 percent of allergic reactions come from eight foods: milk, eggs, peanuts, tree nuts, soy, wheat, fish, and shellfish. The list varies from country to country, depending on dietary customs, but what the trigger foods all have in common is proteins that can survive breakdown in the stomach and enter the bloodstream more or less intact.
"When we were kids, we played in the dirt. Today, children tend to be on their screens, inside sealed buildings."
A food allergy results from a chain of biochemical misunderstandings. The first time the immune system encounters an allergen (as a protein that triggers an allergy is known), it mistakes the substance for a hostile invader—perhaps a parasite with a similar molecular profile. In response, it produces an antibody called immunoglobin E (IgE), which is designed to bind to a specific protein and flag it for attack. These antibodies circulate through the bloodstream and attach to immune-system foot soldiers known as mast cells and basophils, which congregate in the nose, throat, lungs, skin, and gastrointestinal tract.
The next time the person is exposed to the allergen, the IgE antibodies signal the warrior cells to blast the intruder with histamines and other chemical weapons. Tissues in the affected areas swell and leak fluid; blood pressure may fall. Depending on the strength of the reaction, collateral damage to the patient can range from unpleasant—itching, runny nose, nausea—to catastrophic.
This kind of immunological glitchiness runs in families. Genome-wide association studies have identified a dozen genes linked to allergies of all types, and twin studies suggest that about 80 percent of the risk of food allergies is heritable. But why one family member shows symptoms while another doesn't remains unknown. Nor can genetics explain why food allergy rates have skyrocketed in such a brief period. For that, we must turn to the environment.
First, it's important to note that rates of all allergies are rising—including skin and respiratory afflictions—though none as rapidly or with as much risk of anaphylaxis as those involving food. The takeoff was already underway in the late 1980s, when British epidemiologist David P. Strachan found that children in larger households had fewer instances of hay fever. The reason, he suggested, was that their immune systems were strengthened by exposure to their siblings' germs. Since then, other researchers have discerned more evidence for Strachan's "hygiene hypothesis": higher rates of allergy (as well as autoimmune disorders) in cities versus rural areas, in industrialized countries versus developing ones, in lab animals raised under sterile conditions versus those exposed to germs.
Fending off a variety of pathogens, experts theorize, helps train the immune system to better distinguish friend from foe, and to respond to threats in a more nuanced manner. In an era of increasing urbanization, shrinking family sizes, and more sheltered lifestyles, such conditioning may be harder to come by. "When we were kids, we played in the dirt," observes Cathryn R. Nagler, a professor and food allergy researcher at the University of Chicago. "Today, children tend to be on their screens, inside sealed buildings."
But other factors may be driving the allergy epidemic as well. More time indoors, for example, means less exposure to sunlight, which can lead to a deficiency in vitamin D—a nutrient crucial to immune system regulation. The growing popularity of processed foods filled with refined fats and sugars may play a role, along with rising rates of obesity, by promoting tissue inflammation that could increase some people's risk of immunological mayhem. And the surge in allergies also correlates with several trends that may be altering the human microbiome, the community of microbes (including bacteria, viruses, and fungi, among others) that inhabits our guts, skin, and bodily orifices.
The microbiome connection may be particularly relevant to food allergies. In 2014, a team led by Nagler published a landmark study showing that Clostridia, a common class of gut bacteria, protects against these allergies. When the researchers fed peanut allergens to germ-free mice (born and raised in sterile conditions) and to mice treated with antibiotics as newborns (reducing their gut bacteria), the animals showed a strong immunological response. This sensitization could be reversed, however, by reintroducing Clostridia—but not another class of bacteria, Bacteroides—into the mice. Further experiments revealed that Clostridia caused immune cells to produce high levels of interleukin-22 (IL-22), a signaling molecule known to decrease the permeability of the intestinal lining.
"In simple terms," Nagler says, "what we found is that these bacteria prevent food allergens from gaining access to the blood in an intact form that elicits an allergic reaction."
A growing body of evidence suggests that our eating habits are throwing our gut microbiota off-balance, in part by depriving helpful species of the dietary fiber they feed on. Our increasing exposure to antibiotics and antimicrobial compounds may be harming our beneficial bugs as well. These depletions could affect kids from the moment they enter the world: Because babies are seeded with their mothers' microbiota as they pass through the birth canal, they may be inheriting a less diverse microbiome than did previous generations. And the rising rate of caesarian deliveries may be further depriving our children of the bugs they need.
On expert suggests two measures worth a try: increasing consumption of fiber, and reducing use of antimicrobial agents, from antibacterial cleaners to antibiotics.
So which culprit is most responsible for the food allergy upsurge? "The illnesses that we're measuring are complex," says Sicherer. "There are multiple genetic inputs, which interact with one another, and there are multiple environmental inputs, which interact with each other and with the genes. There's not one single thing that's causing this. It's a conglomeration."
What Parents Can Do
For anyone hoping to reduce their child's or their own odds of developing a food allergy (rates of adult onset are also increasing), the current state of science offers few guideposts. As with many other areas of health research, it's hard to know when the data is solid enough to warrant a particular course of action. A case in point: the American Academy of Pediatrics once recommended that children at risk of allergy to peanuts (as evidenced by family history, other food allergies, or eczema) wait to eat them until age three; now, the AAP advises those parents to start their babies at four months, citing epidemiological evidence that early exposure may prevent peanut allergies.
And it's all too easy for a layperson to draw mistaken conclusions from media coverage of such research—inferring, for instance, that taking commercially available probiotics might have a protective effect. Unfortunately, says Nagler, none of those products even contain the relevant kind of bacteria.
Although, as a research scientist, she refrains from giving medical advice, Nagler does suggest (based on a large body of academic literature) that two measures are worth a try: increasing consumption of fiber, and reducing use of antimicrobial agents, from antibacterial cleaners to antibiotics. Yet she acknowledges that it's not always possible to avoid the suspected risk factors for food allergies. Sometimes an antibiotic is a lifesaving necessity, for example—and it's tough to avoid exposure to such drugs altogether, due to their use in animal feed and their consequent presence in many foods and in the water supply. If these chemicals are contributing to the food allergy epidemic, protecting ourselves will require action from farmers, doctors, manufacturers, and policymakers.
My family's experience illustrates the limits of healthy lifestyle choices in mitigating allergy risk. My daughter and son were born without C-sections; both were breastfed as well, receiving maximum microbial seeding from their mother. As a family, we eat exemplary diets, and no one could describe our home as excessively clean. Yet one child can't taste nuts, sesame, or buckwheat without becoming dangerously ill. "You can do everything right and still have allergies," says Ian A. Myles, a staff clinician at the National Institute of Allergy and Infectious Diseases. "You can do everything wrong and not have allergies. The two groups overlap."
The Latest Science Shows Promise
But while preventing all food allergies is clearly unrealistic, researchers are making remarkable progress in developing better treatments—therapies that, instead of combating symptoms after they've started (like epinephrine or antihistamines), aim to make patients less sensitive to allergens in the first place. One promising approach is oral immunotherapy (OIT), in which patients consume small but slowly increasing amounts of an allergen, gradually reducing their sensitivity. A study published last year in the New England Journal of Medicine showed that an experimental OIT called AR101, consisting of a standardized peanut powder mixed into food, enabled 67 percent of participants to tolerate a dose equivalent to two peanut kernels—a potential lifesaver if they were accidentally exposed to the real thing.
Because OIT itself can trigger troublesome reactions in some patients, however, it's not for everyone. Another experimental treatment, sublingual immunotherapy (SLIT) uses an allergen solution or dissolving tablet placed beneath the tongue; although its results are less robust than OIT's, it seems to generate milder side effects. Epicutaneous immunotherapy (EPIT) avoids the mouth entirely, using a technology similar to a nicotine patch to deliver allergens through the skin. Researchers are also exploring the use of medications known as biologics, aiming to speed up the action of immunotherapies by suppressing IgE or targeting other immune-system molecules.
These findings suggest that drugs based on microbial metabolites could help protect vulnerable individuals against a wide range of allergies.
One downside of the immunotherapy approach is that in most cases the allergen must be taken indefinitely to maintain desensitization. To provide a potentially permanent fix, scientists are working on vaccines that use DNA or peptides (protein fragments) from allergens to reset patients' immune systems.
Nagler is attacking the problem from a different angle—one that starts with the microbiome. In a recent study, a follow-up to her peanut-allergy investigation, she and her colleagues found that Clostridia bacteria protect mice against milk allergy as well; they also identified a particular species responsible, known as Anaerostipes caccae. The bugs, the team determined, produce a short-chain fatty acid called butyrate, which modulates many immune activities crucial to maintaining a well-sealed gut.
These findings suggest that drugs based on microbial metabolites could help protect vulnerable individuals against a wide range of allergies. Nagler has launched a company, ClostraBio, to develop biotherapeutics based on this notion; she expects its first product, using synthetic butyrate, to be ready for clinical trials within the next two years.
My daughter could well be a candidate for such a medication. Sam, now 15, is a vibrant, resilient kid who handles her allergies with confidence and humor. Thanks to vigilance and luck (on her part as well as her parents'), she hasn't had another food-related ER visit in more than a decade; she's never had to use her Epi-Pen. Still, she says, she would welcome the arrival of a pill that could reduce the danger. "I've learned how to watch out for myself," she says. "But it would be nice not to have to be so careful."
Imagine eating a slice of cake for breakfast. It's deliciously indulgent, but instead of your blood sugar spiking, your body processes all that sweetness as a healthy high-protein meal. It may sound like sci-fi, but this scenario is not necessarily far off.
"People with diabetes could especially benefit because sweet proteins don't trigger a need for insulin."
The Lowdown
An award-winning agtech startup called Amai is developing "sweet proteins," based on the molecular structure of naturally occuring exotic fruits. These new sugar substitutes could potentially replace artificial sweeteners and help people who are trying to curb their sugar intake. People with diabetes could especially benefit because sweet proteins don't trigger a need for insulin.
While there is a sweet protein currently on the market today called thaumatin, it's expensive, has a short shelf life, and is lacking in the taste department. But Amai's proteins taste 70 to 100 percent identical to the sweet ones found in nature. Once their molecular structure is designed through a sophisticated computing platform, they are made through fermentation, which is akin to brewing beer. These non-GMO proteins are over 10,000 times sweeter than sugar, which means much less needs to be produced and used.
Diseases like diabetes and heart disease, which are often linked to sugar overconsumption, have been on a major upswing over the last few decades, especially in the United States. According to the CDC, 100 million adults in the United States are now living with diabetes or prediabetes, which if not treated, often leads to type 2 diabetes within five years. By 2030, scientists predict cases of diabetes in the U.S. will increase by 54 percent. If sugar proteins like the type Amai is creating become widely available, these numbers could begin to decrease.
Next Up
Amai's sweet proteins are still in the research and development stage, but the Israeli startup is raising significant funding that should help expedite the process. They're also substantially upping their production ability by expanding their facilities.
Will consumers be comfortable ingesting a lab-designed food product?
And in March, the USDA and FDA announced plans to regulate cell-cultured foods, the category in which these sugar proteins would fall, so Amai researchers are hopeful they'll have an easier path to approval once their product is market ready.
Open Questions
All this progress may sound promising, but Amai still has a long way to go before the reality of healthy cake becomes tangible. Some questions to consider: Will consumers be comfortable ingesting a lab-designed food product? Will it taste enough like real sugar?
And if some products and brands begin to adopt it, will it ever overtake the real thing in popularity and make a dent in diseases like diabetes and obesity? Only time, more research, and a lot more money will tell, but in the meantime, feel free to daydream about eating entire pints of ice cream without needing to hit the gym.