Lynn Julian Crisci, 40, is an actress, a singer-songwriter, and an ambassador for the U.S. Pain Foundation. She is also a Boston Marathon bombing survivor. Crisci has a genetic disorder called Ehlers-Danlos syndrome (EDS), which has magnified the impact of the traumatic brain injury she sustained as a result of the attack that occurred almost five years ago. Having EDS means that her brain tissue is weaker and more prone to injury.￼
"I would love to learn more about gene editing and the possibilities of using it to lessen the symptoms of EDS, or cure it completely."
"EDS is a genetic tissue disorder that forces the body to make defective collagen," Crisci told LeapsMag. Since collagen is the main component of connective tissue (bones, blood vessels, the gastrointestinal tract, skin, cartilage, etc.), and is the most abundant protein in mammals, EDS can affect virtually every part of the body. "This results in widespread joint pain, usually due to hypermobility, sometimes along with digestive issues such as inflammatory bowel disease, and prolapsed organs."
If life was difficult with Ehlers-Danlos syndrome alone, the addition of the brain injury has made Crisci's life feel unbearable at times. Amidst her week's back-to-back doctor's visits, Crisci said that she would "love to learn more about gene editing and the possibilities of using it to lessen the symptoms of Ehlers-Danlos syndrome, or cure it completely."
With all of the excitement these days around CRISPR, a precise and efficient way to edit DNA that has taken the world by storm, such treatments seem tantalizingly within reach. But is it fair to present the hope of such cures to those with life-limiting genetic disorders?
"From the experience that we've had from gene therapy — we're 20, almost 30 years past some of the initial gene therapy stuff — and there's still not a huge number of applications for it," said Scott Weissman, founder of Chicago Genetic Consultants, a company that provides genetic counseling services to patients. "Unfortunately, we have to wait and see if this is something that's truly viable, or if it's really just hype."
"I expect five years from now we'll look back and say, 'Wow, we were just scratching the surface.'"
Defining Our Terms
The terms "gene therapy" and "gene editing" are often used interchangeably, but not everyone agrees with this usage.
According to Editas Medicine, a leader in CRISPR technology, gene therapy involves the transfer of a new gene into a patient's cells to augment a defective gene, instead of using drugs or surgery to treat a condition. After a teenager's death in 1999 effectively shut down gene therapy research in the U.S., subsequent studies helped the field make a comeback, and the first such treatment for an inherited disease was approved by the FDA just a few weeks ago, for a rare form of vision loss. Called Luxturna, it is for treatment of patients with RPE65-mediated inherited retinal disease (IRD).
Since those with RPE65-mediated IRD typically become blind in childhood and have no pharmacologic treatment options, the FDA's approval of Luxturna is "a significant moment for patients," said Jeffrey Marrazzo, the chief executive officer of the company behind the product, Spark Therapeutics. Two other gene therapy treatments were also approved in the last five months, both for specific cancers.
Gene editing, on the other hand, refers to a group of technologies that enables scientists to precisely and directly change an organism's genes by adding, removing, or altering particular segments of DNA. Gene editing tools include Zinc Finger Nucleases (ZFNs), Transcription Activator-Like Effector Nucleases (TALENs), and CRISPR/Cas9. The first treatment using ZFNs happened in November in California, when a 44-year-old man with a metabolic ailment called Hunter syndrome was injected with gene editing tools. Results are not yet known.
Dr. David Valle, director of the Institute of Genetic Medicine at Johns Hopkins, said that gene therapy's "significant therapeutic misadventures" have actually been beneficial. They've helped us learn to "be rigorous in our thinking about what we can do and what we can't do with CRISPR" and other gene editing tools.
"It appears like we are really beginning to have, for the first time, some meaningful and good results from gene therapy — it's moving into the clinic now in a meaningful way," Valle said. "I expect five years from now we'll look back and say, 'Wow, we were just at this point in 2017 — we were just scratching the surface.'"
Over 2300 gene therapy clinical trials are planned, ongoing, or have been completed so far. As for gene editing, no treatments are commercially available anywhere in the world. The expectation, however, is that many treatments that are "currently in or soon to enter clinical trials will come up for approval in coming years," according to a November 2016 report by the American Society of Gene & Cell Therapy.
CRISPR Therapeutics of Cambridge, Massachusetts will begin a European gene editing trial this year, with the hopes of creating a treatment for beta thalassemia, an inherited blood disorder. The company will also request approval from the FDA to begin a clinical trial using CRISPR for sickle-cell disease. And Stanford University School of Medicine researchers are planning a similar CRISPR clinical trial for sickle-cell disease. They hope to begin their trial in 2019.
Jim Burns, the president and chief executive officer of Casebia Therapeutics, told Leapsmag that the company will start animal research this year using CRISPR to treat autoimmune diseases, hemophilia A, and retinal diseases. They expect to begin clinical research in humans in 2019 or 2020. [Disclosure: Casebia Therapeutics is a novel joint venture between CRISPR Therapeutics and Leapsmag's founder, Leaps by Bayer, though Leapsmag is editorially independent of Bayer.]
Efforts are well underway to take genome-targeted treatments from the scientist's bench to the patient's bedside.
The Technology Isn't There Yet
Unlike germline gene editing — when egg and sperm cell DNA is edited in an embryo — somatic cell gene editing in adults is not very controversial, because the edits are not heritable. Since somatic cells contribute to the various tissues of the body but not to eggs or sperm cells, changes made to somatic cells are limited to the treated individual.
The number one reason that gene therapy and gene editing treatments are not yet widely available to the adult population is that the technology is not advanced enough. But it's getting there. Efforts are well underway to take genome-targeted treatments from the scientist's bench to the patient's bedside — especially in the case of monogenic diseases.
Roughly 10,000 genetic illnesses are monogenic, meaning that they result from a disease-causing variant in a single gene. Some monogenic diseases that have gene editing treatments currently in development for use in clinical trials include cystic fibrosis, Huntington's disease, Tay-Sachs disease, and sickle cell anemia.
Marrazzo of Spark Therapeutics told LeapsMag that his company is working on gene therapies for monogenic diseases that affect the eye, like the retinal disease that Luxturna targets, as well as neurodegenerative and liver diseases.
But most illnesses are polygenic, meaning that they result from multiple gene mutations that have a combined influence on disease progression. Polygenic diseases, like high blood pressure and diabetes, would therefore be more challenging to treat with genome-targeted interventions. As a result, most research is currently focused on monogenic diseases.
"We don't really know how to target the gene editing to a specific organ in the body once it's fully developed and matured."
A major hurdle of gene editing is the risk of off-target effects. Editing the genome "can have unpredictable effects on gene expression and unintended effects on neighboring genes," wrote Morgan Maeder and Charles Gersbach in a March 2016 article in Molecular Therapy. One such unintended effect is the development of leukemia when a new gene unintentionally activates a cancer gene.
And since there are roughly 37 trillion cells in the adult human body, getting the gene editing machinery to enough cells or target tissues to create a lasting and significant change is a daunting task.
"We don't really know how to target the gene editing to a specific organ in the body once it's fully developed and matured," said Weissman, the genetic counseling expert. If you take an adult patient with known BRCA1 or BRCA2 mutations, for example, how do you then "get the [gene editing] system in the breast so that it accurately cuts out the mutation in every single breast cell that could potentially turn into breast cancer, or in every single ovarian cell that could turn into ovarian cancer? We don't know how to target it like that, and I think that's the biggest reason you're not seeing it more somatically at this point in time."
Approval and Access
Debra Mathews, assistant director for science programs for the Johns Hopkins Berman Institute of Bioethics, told LeapsMag that pre-existing regulatory frameworks surrounding gene therapy have been sufficient for addressing ethical and regulatory concerns surrounding gene editing. A bigger concern, she said, centers around access to future genome-targeted treatments.
"We know more about the genetics of Caucasian populations than other populations," Mathews explained, due to how genomic data is gathered. This "could lead to problems not just of financial but of biological access to new therapies." In other words, she said, "if you're of European ancestry, there may be a greater chance that there's a relevant genetically-targeted therapy for you than if you're of non-European ancestry."
Ensuring that genome-targeted treatments are accessible to all will require increased cooperation and data-sharing among key stakeholders around the world, as well as increased public engagement that is inclusive of a wide range of voices.
"It's important to be realistic in our predictions to the public."
The Coming Wave of Gene Editing Treatments
Ehlers-Danlos syndrome alone has 13 monogenic subtypes, each with its own genetic basis and set of clinical criteria. Though several of the gene mutations causing EDS subtypes have been identified, the genetic basis for the most common subtype that Lynn Julian Crisci has — hypermobile EDS — remains unknown. What this means, according to Valle, the doctor from Johns Hopkins, is that a gene therapy or gene editing approach "really cannot be contemplated because we don't know what we're trying to fix" yet. This is the case for many genetic illnesses.
Efforts are ongoing in gene discovery by organizations such as the Baylor-Hopkins Center for Mendelian Genomics, of which Valle is the principal investigator. "Our objective," he said, "is to identify the genes and variants responsible" in monogenic disorders.
While Valle is optimistic about the coming wave of commercially available gene therapy and gene editing treatments, he also thinks that "it's important to be realistic in our predictions to the public." As eager as physicians are to offer cures to their patients, "we have to make sure that we're rigorous in our thinking and our ideas are well-buttressed with results."
Estimates vary for how long Crisci and others with genetic illnesses will have to wait for genome-targeted treatment options. Depending on the illness, viable gene editing treatments could hit the market within the next ten years. Though patients have already waited a long while, the revolutionary technology allowing us to fix nature's mistakes could make up for lost time and lost hope.
In December 1958, on a vacation with his wife in Kenya, a 28-year-old British tea broker named Robin Cavendish became suddenly ill. Neither he nor his wife Diana knew it at the time, but Robin's illness would change the course of medical history forever.
Robin was rushed to a nearby hospital in Kenya where the medical staff delivered the crushing news: Robin had contracted polio, and the paralysis creeping up his body was almost certainly permanent. The doctors placed Robin on a ventilator through a tracheotomy in his neck, as the paralysis from his polio infection had rendered him unable to breathe on his own – and going off the average life expectancy at the time, they gave him only three months to live. Robin and Diana (who was pregnant at the time with their first child, Jonathan) flew back to England so he could be admitted to a hospital. They mentally prepared to wait out Robin's final days.
But Robin did something unexpected when he returned to the UK – just one of many things that would astonish doctors over the next several years: He survived. Diana gave birth to Jonathan in February 1959 and continued to visit Robin regularly in the hospital with the baby. Despite doctors warning that he would soon succumb to his illness, Robin kept living.
After a year in the hospital, Diana suggested something radical: She wanted Robin to leave the hospital and live at home in South Oxfordshire for as long as he possibly could, with her as his nurse. At the time, this suggestion was unheard of. People like Robin who depended on machinery to keep them breathing had only ever lived inside hospital walls, as the prevailing belief was that the machinery needed to keep them alive was too complicated for laypeople to operate. But Diana and Robin were up for the challenges – and the risks. Because his ventilator ran on electricity, if the house were to unexpectedly lose power, Diana would either need to restore power quickly or hand-pump air into his lungs to keep him alive.
Robin's wheelchair was not only the first of its kind; it became the model for the respiratory wheelchairs that people still use today.
In an interview as an adult, Jonathan Cavendish reflected on his parents' decision to live outside the hospital on a ventilator: "My father's mantra was quality of life," he explained. "He could have stayed in the hospital, but he didn't think that was as good of a life as he could manage. He would rather be two minutes away from death and living a full life."
After a few years of living at home, however, Robin became tired of being confined to his bed. He longed to sit outside, to visit friends, to travel – but had no way of doing so without his ventilator. So together with his friend Teddy Hall, a professor and engineer at Oxford University, the two collaborated in 1962 to create an entirely new invention: a battery-operated wheelchair prototype with a ventilator built in. With this, Robin could now venture outside the house – and soon the Cavendish family became famous for taking vacations. It was something that, by all accounts, had never been done before by someone who was ventilator-dependent. Robin and Hall also designed a van so that the wheelchair could be plugged in and powered during travel. Jonathan Cavendish later recalled a particular family vacation that nearly ended in disaster when the van broke down outside of Barcelona, Spain:
"My poor old uncle [plugged] my father's chair into the wrong socket," Cavendish later recalled, causing the electricity to short. "There was fire and smoke, and both the van and the chair ground to a halt." Johnathan, who was eight or nine at the time, his mother, and his uncle took turns hand-pumping Robin's ventilator by the roadside for the next thirty-six hours, waiting for Professor Hall to arrive in town and repair the van. Rather than being panicked, the Cavendishes managed to turn the vigil into a party. Townspeople came to greet them, bringing food and music, and a local priest even stopped by to give his blessing.
Robin had become a pioneer, showing the world that a person with severe disabilities could still have mobility, access, and a fuller quality of life than anyone had imagined. His mission, along with Hall's, then became gifting this independence to others like himself. Robin and Hall raised money – first from the Ernest Kleinwort Charitable Trust, and then from the British Department of Health – to fund more ventilator chairs, which were then manufactured by Hall's company, Littlemore Scientific Engineering, and given to fellow patients who wanted to live full lives at home. Robin and Hall used themselves as guinea pigs, testing out different models of the chairs and collaborating with scientists to create other devices for those with disabilities. One invention, called the Possum, allowed paraplegics to control things like the telephone and television set with just a nod of the head. Robin's wheelchair was not only the first of its kind; it became the model for the respiratory wheelchairs that people still use today.
Robin went on to enjoy a long and happy life with his family at their house in South Oxfordshire, surrounded by friends who would later attest to his "down-to-earth" personality, his sense of humor, and his "irresistible" charm. When he died peacefully at his home in 1994 at age 64, he was considered the world's oldest-living person who used a ventilator outside the hospital – breaking yet another barrier for what medical science thought was possible.
Sarah Watts is a health and science writer based in Chicago. Follow her on Twitter at @swattswrites.
In June 2012, Kirstie Ennis was six months into her second deployment to Afghanistan and recently promoted to sergeant. The helicopter gunner and seven others were three hours into a routine mission of combat resupplies and troop transport when their CH-53D helicopter went down hard.
Miraculously, all eight people onboard survived, but Ennis' injuries were many and severe. She had a torn rotator cuff, torn labrum, crushed cervical discs, facial fractures, deep lacerations and traumatic brain injury. Despite a severely fractured ankle, doctors managed to save her foot, for a while at least.
In November 2015, after three years of constant pain and too many surgeries to count, Ennis relented. She elected to undergo a lower leg amputation but only after she completed the 1,000-mile, 72-day Walking with the Wounded journey across the UK.
On Veteran's Day of that year, on the other side of the country, orthopedic surgeon Cato Laurencin announced a moonshot challenge he was setting out to achieve on behalf of wounded warriors like Ennis: the Hartford Engineering A Limb (HEAL) Project.
Laurencin, who is a University of Connecticut professor of chemical, materials and biomedical engineering, teamed up with experts in tissue bioengineering and regenerative medicine from Harvard, Columbia, UC Irvine and SASTRA University in India. Laurencin and his colleagues at the Connecticut Convergence Institute for Translation in Regenerative Engineering made a bold commitment to regenerate an entire limb within 15 years – by the year 2030.
Dr. Cato Laurencin pictured in his office at UConn.
Photo Credit: UConn
Regenerative Engineering -- A Whole New Field
Limb regeneration in humans has been a medical and scientific fascination for decades, with little to show for the effort. However, Laurencin believes that if we are to reach the next level of 21st century medical advances, this puzzle must be solved.
An estimated 185,000 people undergo upper or lower limb amputation every year. Despite the significant advances in electromechanical prosthetics, these individuals still lack the ability to perform complex functions such as sensation for tactile input, normal gait and movement feedback. As far as Laurencin is concerned, the only clinical answer that makes sense is to regenerate a whole functional limb.
Laurencin feels other regeneration efforts were hampered by their siloed research methods with chemists, surgeons, engineers all working separately. Success, he argues, requires a paradigm shift to a trans-disciplinary approach that brings together cutting-edge technologies from disparate fields such as biology, material sciences, physical, chemical and engineering sciences.
As the only surgeon ever inducted into the academies of Science, Medicine and Innovation, Laurencin is uniquely suited for the challenge. He is regarded as the founder of Regenerative Engineering, defined as the convergence of advanced materials sciences, stem cell sciences, physics, developmental biology and clinical translation for the regeneration of complex tissues and organ systems.
But none of this is achievable without early clinician participation across scientific fields to develop new technologies and a deeper understanding of how to harness the body's innate regenerative capabilities. "When I perform a surgical procedure or something is torn or needs to be repaired, I count on the body being involved in regenerating tissue," he says. "So, understanding how the body works to regenerate itself and harnessing that ability is an important factor for the regeneration process."
The Birth of the Vision
Laurencin's passion for regeneration began when he was a sports medicine fellow at Cornell University Medical Center in the early 1990s. There he saw a significant number of injuries to the anterior cruciate ligament (ACL), the major ligament that stabilizes the knee. He believed he could develop a better way to address those injuries using biomaterials to regenerate the ligament. He sketched out a preliminary drawing on a napkin one night over dinner. He has spent the next 30 years regenerating tissues, including the patented L-C ligament.
As chair of Orthopaedic Surgery at the University of Virginia during the peak of the wars in Iraq and Afghanistan, Laurencin treated military personnel who survived because of improved helmets, body armor and battlefield medicine but were left with more devastating injuries, including traumatic brain injuries and limb loss.
"I was so honored to care for them and I so admired their steadfast courage that I became determined to do something big for them," says Laurencin.
When he tells people about his plans to regrow a limb, he gets a lot of eye rolls, which he finds amusing but not discouraging. Growing bone cells was relatively new when he was first focused on regenerating bone in 1987 at MIT; in 2007 he was well on his way to regenerating ligaments at UVA when many still doubted that ligaments could even be reconstructed. He and his team have already regenerated torn rotator cuff tendons and ACL ligaments using a nano-textured fabric seeded with stem cells.
Even as a finalist for the $4 million NIH Pioneer Award for high-risk/high-reward research, he faced a skeptical scientific audience in 2014. "They said, 'Well what do you plan to do?' I said 'I plan to regenerate a whole limb in people.' There was a lot of incredulousness. They stared at me and asked a lot of questions. About three days later, I received probably the best score I've ever gotten on an NIH grant."
In the Thick of the Science
Humans are born with regenerative abilities--two-year-olds have regrown fingertips--but lose that ability with age. Salamanders are the only vertebrates that can regenerate lost body parts as adults; axolotl, the rare Mexican salamander, can grow extra limbs.
The axolotl is important as a model organism because it is a four-footed vertebrate with a similar body plan to humans. Mapping the axolotl genome in 2018 enhanced scientists' genetic understanding of their evolution, development, and regeneration. Being easy to breed in captivity allowed the HEAL team to closely study these amphibians and discover a new cell type they believe may shed light on how to mimic the process in humans.
"Whenever limb regeneration takes place in the salamander, there is a huge amount of something called heparan sulfate around that area," explains Laurencin. "We thought, 'What if this heparan sulfate is the key ingredient to allowing regeneration to take place?' We found these groups of cells that were interspersed in tissues during the time of regeneration that seemed to have connections to each other that expressed this heparan sulfate."
Called GRID (Groups that are Regenerative, Interspersed and Dendritic), these cells were also recently discovered in mice. While GRID cells don't regenerate as well in mice as in salamanders, finding them in mammals was significant.
"If they're found in mice. we might be able to find these in humans in some form," Laurencin says. "We think maybe it will help us figure out regeneration or we can create cells that mimic what grid cells do and create an artificial grid cell."
What Comes Next?
Laurencin and his team have individually engineered and made every single tissue in the lower limb, including bone, cartilage, ligament, skin, nerve, blood vessels. Regenerating joints and joint tissue is the next big mile marker, which Laurencin sees as essential to regenerating a limb that functions and performs in the way he envisions.
"Using stem cells and amnion tissue, we can regenerate joints that are damaged, and have severe arthritis," he says. "We're making progress on all fronts, and making discoveries we believe are going to be helping people along the way."
That focus and advancement is vital to Ennis. After laboring over the decision to have her leg amputated below the knee, she contracted MRSA two weeks post-surgery. In less than a month, she went from a below-the-knee-amputee to a through-the-knee amputee to an above-the-knee amputee.
"A below-the-knee amputation is night-and-day from above-the-knee," she said. "You have to relearn everything. You're basically a toddler."
Kirstie Ennis pictured in July 2020.
Photo Credit: Ennis' Instagram
The clock is ticking on the timeline Laurencin set for himself. Nine years might seem like forever if you're doing time but it might appear fleeting when you're trying to create something that's never been done before. But Laurencin isn't worried. He's convinced time is on his side.
"Every week, I receive an email or a call from someone, maybe a mother whose child has lost a finger or I'm in communication with a disabled American veteran who wants to know how the progress is going. That energizes me to continue to work hard to try to create these sorts of solutions because we're talking about people and their lives."
He devotes about 60 hours a week to the project and the roughly 100 students, faculty and staff who make up the HEAL team at the Convergence Institute seem acutely aware of what's at stake and appear equally dedicated.
"We're in the thick of the science in terms of making this happen," says Laurencin. "We've moved from making the impossible possible to making the possible a reality. That's what science is all about."