How a Nobel-Prize Winner Fought Her Family, Nazis, and Bombs to Change our Understanding of Cells Forever
When Rita Levi-Montalcini decided to become a scientist, she was determined that nothing would stand in her way. And from the beginning, that determination was put to the test. Before Levi-Montalcini became a Nobel Prize-winning neurobiologist, the first to discover and isolate a crucial chemical called Neural Growth Factor (NGF), she would have to battle both the sexism within her own family as well as the racism and fascism that was slowly engulfing her country
Levi-Montalcini was born to two loving parents in Turin, Italy at the turn of the 20th century. She and her twin sister, Paola, were the youngest of the family's four children, and Levi-Montalcini described her childhood as "filled with love and reciprocal devotion." But while her parents were loving, supportive and "highly cultured," her father refused to let his three daughters engage in any schooling beyond the basics. "He loved us and had a great respect for women," she later explained, "but he believed that a professional career would interfere with the duties of a wife and mother."
At age 20, Levi-Montalcini had finally had enough. "I realized that I could not possibly adjust to a feminine role as conceived by my father," she is quoted as saying, and asked his permission to finish high school and pursue a career in medicine. When her father reluctantly agreed, Levi-Montalcini was ecstatic: In just under a year, she managed to catch up on her mathematics, graduate high school, and enroll in medical school in Turin.
By 1936, Levi-Montalcini had graduated medical school at the top of her class and decided to stay on at the University of Turin as a research assistant for histologist and human anatomy professor Guiseppe Levi. Levi-Montalcini started studying nerve cells and nerve fibers – the tiny, slender tendrils that are threaded throughout our nerves and that determine what information each nerve can transmit. But it wasn't long before another enormous obstacle to her scientific career reared its head.
Science Under a Fascist Regime
Two years into her research assistant position, Levi-Montalcini was fired, along with every other "non-Aryan Italian" who held an academic or professional career, thanks to a series of antisemitic laws passed by Italy's then-leader Benito Mussolini. Forced out of her academic position, Levi-Montalcini went to Belgium for a fellowship at a neurological institute in Brussels – but then was forced back to Turin when the German army invaded.
Levi-Montalcini decided to keep researching. She and Guiseppe Levi built a makeshift lab in Levi-Montalcini's apartment, borrowing chicken eggs from local farmers and using sewing needles to dissect them. By dissecting the chicken embryos from her bedroom laboratory, she was able to see how nerve fibers formed and died. The two continued this research until they were interrupted again – this time, by British air raids. Levi-Montalcini fled to a country cottage to continue her research, and then two years later was forced into hiding when the German army invaded Italy. Levi-Montalcini and her family assumed different identities and lived with non-Jewish friends in Florence to survive the Holocaust. Despite all of this, Levi-Montalcini continued her work, dissecting chicken embryos from her hiding place until the end of the war.
"The discovery of NGF really changed the world in which we live, because now we knew that cells talk to other cells, and that they use soluble factors. It was hugely important."
A Post-War Discovery
Several years after the war, when Levi-Montalcini was once again working at the University of Turin, a German embryologist named Viktor Hamburger invited her to Washington University in St. Louis. Hamburger was impressed by Levi-Montalcini's research with her chicken embryos, and secured an opportunity for her to continue her work in America. The invitation would "change the course of my life," Levi-Montalcini would later recall.
During her fellowship, Montalcini grew tumors in mice and then transferred them to chick embryos in order to see how it would affect the chickens. To her surprise, she noticed that introducing the tumor samples would cause nerve fibers to grow rapidly. From this, Levi-Montalcini discovered and was able to isolate a protein that she determined was able to cause this rapid growth. She later named this Nerve Growth Factor, or NGF.
From there, Levi-Montalcini and her team launched new experiments to test NGF, injecting it and repressing it to see the effect it had in a test subject's body. When the team injected NGF into embryonic mice, they observed nerve growth, as well as the mouse pups developing faster – their eyes opening earlier and their teeth coming in sooner – than the untreated group. When the team purified the NGF extract, however, it had no effect, leading the team to believe that something else in the crude extract of NGF was influencing the growth of the newborn mice. Stanley Cohen, Levi-Montalcini's colleague, identified another growth factor called EGF – epidermal growth factor – that caused the mouse pups' eyes and teeth to grow so quickly.
Levi-Montalcini continued to experiment with NGF for the next several decades at Washington University, illuminating how NGF works in our body. When Levi-Montalcini injected newborn mice with an antiserum for NGF, for example, her team found that it "almost completely deprived the animals of a sympathetic nervous system." Other experiments done by Levi-Montalcini and her colleagues helped show the role that NGF plays in other important biological processes, such as the regulation of our immune system and ovulation.
"The discovery of NGF really changed the world in which we live, because now we knew that cells talk to other cells, and that they use soluble factors. It was hugely important," said Bill Mobley, Chair of the Department of Neurosciences at the University of California, San Diego School of Medicine.
Her Lasting Legacy
After years of setbacks, Levi-Montalcini's groundbreaking work was recognized in 1986, when she was awarded the Nobel Prize in Medicine for her discovery of NGF (Cohen, her colleague who discovered EGF, shared the prize). Researchers continue to study NGF even to this day, and the continued research has been able to increase our understanding of diseases like HIV and Alzheimer's.
Levi-Montalcini never stopped researching either: In January 2012, at the age of 102, Levi-Montalcini published her last research paper in the journal PNAS, making her the oldest member of the National Academy of Science to do so. Before she died in December 2012, she encouraged other scientists who would suffer setbacks in their careers to keep pursuing their passions. "Don't fear the difficult moments," Levi-Montalcini is quoted as saying. "The best comes from them."
Three Big Biotech Ideas to Watch in 2020—And Beyond
1. Happening Now: Body-on-a-Chip Technology Is Enabling Safer Drug Trials and Better Cancer Research
Researchers have increasingly used the technology known as "lab-on-a-chip" or "organ-on-a-chip" to test the effects of pharmaceuticals, toxins, and chemicals on humans. Rather than testing on animals, which raises ethical concerns and can sometimes be inaccurate, and human-based clinical trials, which can be expensive and difficult to iterate, scientists turn to tiny, micro-engineered chips—about the size of a thumb drive.
It's possible that doctors could one day take individual cell samples and create personalized treatments, testing out any medications on the chip.
The chips are lined with living samples of human cells, which mimic the physiology and mechanical forces experienced by cells inside the human body, down to blood flow and breathing motions; the functions of organs ranging from kidneys and lungs to skin, eyes, and the blood-brain barrier.
A more recent—and potentially even more useful—development takes organ-on-a-chip technology to the next level by integrating several chips into a "body-on-a-chip." Since human organs don't work in isolation, seeing how they all react—and interact—once a foreign element has been introduced can be crucial to understanding how a certain treatment will or won't perform. Dr. Shyni Varghese, a MEDx investigator at the Duke University School of Medicine, is one of the researchers working with these systems in order to gain a more nuanced understanding of how multiple different organs react to the same stimuli.
Her lab is working on "tumor-on-a-chip" models, which can not only show the progression and treatment of cancer, but also model how other organs would react to immunotherapy and other drugs. "The effect of drugs on different organs can be tested to identify potential side effects," Varghese says. In addition, these models can help the researchers figure out how cancers grow and spread, as well as how to effectively encourage immune cells to move in and attack a tumor.
One body-on-a-chip used by Dr. Varghese's lab tracks the interactions of five organs—brain, heart, liver, muscle, and bone.
As their research progresses, Varghese and her team are looking for ways to maintain the long-term function of the engineered organs. In addition, she notes that this kind of research is not just useful for generalized testing; "organ-on-chip technologies allow patient-specific analyses, which can be used towards a fundamental understanding of disease progression," Varghese says. It's possible that doctors could one day take individual cell samples and create personalized treatments, testing out any medications on the chip for safety, efficacy, and potential side effects before writing a prescription.
2. Happening Soon: Prime Editing Will Have the Power to "Find and Replace" Disease-Causing Genes
Biochemist David Liu made industry-wide news last fall when he and his lab at MIT's Broad Institute, led by Andrew Anzalone, published a paper on prime editing: a new, more focused technology for editing genes. Prime editing is a descendant of the CRISPR-Cas9 system that researchers have been working with for years, and a cousin to Liu's previous innovation—base editing, which can make a limited number of changes to a single DNA letter at a time.
By contrast, prime editing has the potential to make much larger insertions and deletions; it also doesn't require the tweaked cells to divide in order to write the changes into the DNA, which could make it especially suitable for central nervous system diseases, like Parkinson's.
Crucially, the prime editing technique has a much higher efficiency rate than the older CRISPR system, and a much lower incidence of accidental insertions or deletions, which can make dangerous changes for a patient.
It also has a very broad potential range: according to Liu, 89% of the pathogenic mutations that have been collected in ClinVar (a public archive of human variations) could, in principle, be treated with prime editing—although he is careful to note that correcting a single genetic mutation may not be sufficient to fully treat a genetic disease.
Figuring out just how prime editing can be used most effectively and safely will be a long process, but it's already underway. The same day that Liu and his team posted their paper, they also made the basic prime editing constructs available for researchers around the world through Addgene, a plasmid repository, so that others in the scientific community can test out the technique for themselves. It might be years before human patients will see the results, and in the meantime, significant bioethical questions remain about the limits and sociological effects of such a powerful gene-editing tool. But in the long fight against genetic diseases, it's a huge step forward.
3. Happening When We Fund It: Focusing on Microbiome Health Could Help Us Tackle Social Inequality—And Vice Versa
The past decade has seen a growing awareness of the major role that the microbiome, the microbes present in our digestive tract, play in human health. Having a less-healthy microbiome is correlated with health risks like diabetes and depression, and interventions that target gut health, ranging from kombucha to fecal transplants, have cropped up with increasing frequency.
New research from the University of Maine's Dr. Suzanne Ishaq takes an even broader view, arguing that low-income and disadvantaged populations are less likely to have healthy, diverse gut bacteria, and that increasing access to beneficial microorganisms is an important juncture of social justice and public health.
"Basically, allowing people to lead healthy lives allows them to access and recruit microbes."
"Typically, having a more diverse bacterial community is associated with health, and having fewer different species is associated with illness and may leave you open to infection from bacteria that are good at exploiting opportunities," Ishaq says.
Having a healthy biome doesn't mean meeting one fixed ratio of gut bacteria, since different combinations of microbes can generate roughly similar results when they work in concert. Generally, "good" microbes are the ones that break down fiber and create the byproducts that we use for energy, or ones like lactic acid bacteria that work to make microbials and keep other bacteria in check. The microbial universe in your gut is chaotic, Ishaq says. "Microbes in your gut interact with each other, with you, with your food, or maybe they don't interact at all and pass right through you." Overall, it's tricky to name specific microbial communities that will make or break someone's health.
There are important corollaries between environment and biome health, though, which Ishaq points out: Living in urban environments reduces microbial exposure, and losing the microorganisms that humans typically source from soil and plants can reduce our adaptive immunity and ability to fight off conditions like allergies and asthma. Access to green space within cities can counteract those effects, but in the U.S. that access varies along income, education, and racial lines. Likewise, lower-income communities are more likely to live in food deserts or areas where the cheapest, most convenient food options are monotonous and low in fiber, further reducing microbial diversity.
Ishaq also suggests other areas that would benefit from further study, like the correlation between paid family leave, breastfeeding, and gut microbiota. There are technical and ethical challenges to direct experimentation with human populations—but that's not what Ishaq sees as the main impediment to future research.
"The biggest roadblock is money, and the solution is also money," she says. "Basically, allowing people to lead healthy lives allows them to access and recruit microbes."
That means investment in things we already understand to improve public health, like better education and healthcare, green space, and nutritious food. It also means funding ambitious, interdisciplinary research that will investigate the connections between urban infrastructure, housing policy, social equity, and the millions of microbes keeping us company day in and day out.
Scientists Just Started Testing a New Class of Drugs to Slow--and Even Reverse--Aging
Imagine reversing the processes of aging. It's an age-old quest, and now a study from the Mayo Clinic may be the first ray of light in the dawn of that new era.
The immune system can handle a certain amount of senescence, but that capacity declines with age.
The small preliminary report, just nine patients, primarily looked at the safety and tolerability of the compounds used. But it also showed that a new class of small molecules called senolytics, which has proven to reverse markers of aging in animal studies, can work in humans.
Aging is a relentless assault of chronic diseases including Alzheimer's, cardiovascular disease, diabetes, and frailty. Developing one chronic condition strongly predicts the rapid onset of another. They pile on top of each other and impede the body's ability to respond to the next challenge.
"Potentially, by targeting fundamental aging processes, it may be possible to delay or prevent or alleviate multiple age-related conditions and many diseases as a group, instead of one at a time," says James Kirkland, the Mayo Clinic physician who led the study and is a top researcher in the growing field of geroscience, the biology of aging.
Getting Rid of "Zombie" Cells
One element common to many of the diseases is senescence, a kind of limbo or zombie-like state where cells no longer divide or perform many regular functions, but they don't die. Senescence is thought to be beneficial in that it inhibits the cancerous proliferation of cells. But in aging, the senescent cells still produce molecules that create inflammation both locally and throughout the body. It is a cycle that feeds upon itself, slowly ratcheting down normal body function and health.
Disease and harmful stimuli like radiation to treat cancer can also generate senescence, which is why young cancer patients seem to experience earlier and more rapid aging. The immune system can handle a certain amount of senescence, but that capacity declines with age. There also appears to be a threshold effect, a tipping point where senescence becomes a dominant factor in aging.
Kirkland's team used an artificial intelligence approach called machine learning to look for cell signaling networks that keep senescent cells from dying. To date, researchers have identified at least eight such signaling networks, some of which seem to be unique to a particular type of cell or tissue, but others are shared or overlap.
Then a computer search identified molecules known to disrupt these signaling pathways "and allow cells that are fully senescent to kill themselves," he explains. The process is a bit like looking for the right weapons in a video game to wipe out lingering zombie cells. But instead of swords, guns, and grenades, the list of biological tools so far includes experimental molecules, approved drugs, and natural supplements.
Treatment
"We found early on that targeting single components of those networks will only kill a very small minority of senescent cells or senescent cell types," says Kirkland. "So instead of going after one drug-one target-one disease, we're going after networks with combinations of drugs or drugs that have multiple targets. And we're going after every age-related disease."
The FDA is grappling with guidance for researchers wanting to conduct clinical trials on something as broad as aging rather than a single disease.
The large number of potential senolytic (i.e. zombie-neutralizing) compounds they identified allowed Kirkland to be choosy, "purposefully selecting drugs where the side effects profile was good...and with short elimination half-lives." The hit and run approach meant they didn't have to worry about maintaining a steady state of drugs in the body for an extended period of time. Some of the compounds they selected need only a half hour exposure to trigger the dying process in senescent cells, which can then take several days.
Work in mice has already shown impressive results in reversing diabetes, weight gain, Alzheimer's, cardiovascular disease and other conditions using senolytic agents.
That led to Kirkland's pilot study in humans with diabetes-related kidney disease using a three-day regimen of dasatinib, a kinase inhibitor first approved in 2006 to treat some forms of blood cancer, and quercetin, a flavonoid found in many plants and sold as a food supplement.
The combination was safe and well tolerated; it reduced the number of senescent cells in the belly fat of patients and restored their normal function, according to results published in September in the journal EBioMedicine. This preliminary paper was based on 9 patients in an ongoing study of 30 patients.
Kirkland cautions that these are initial and incomplete findings looking primarily at safety issues, not effectiveness. There is still much to be learned about the use of senolytics, starting with proof that they actually provide clinical benefit, and against what chronic conditions. The drug combinations, doses, duration, and frequency, not to mention potential risks all must be worked out. Additional studies of other diseases are being developed.
What's Next
Ron Kohanski, a senior administrator at the NIH National Institute on Aging (NIA), says the field of senolytics is so new that there isn't even a consensus on how to identify a senescent cell, and the FDA is grappling with guidance for researchers wanting to conduct clinical trials on something as broad as aging rather than a single disease.
Intellectual property concerns may temper the pharmaceutical industry's interest in developing senolytics to treat chronic diseases of aging. It looks like many mix-and-match combinations are possible, and many of the potential molecules identified so far are found in nature or are drugs whose patents have or will soon expire. So the ability to set high prices for such future drugs, and hence the willingness to spend money on expensive clinical trials, may be limited.
Still, Kohanski believes the field can move forward quickly because it often will include products that are already widely used and have a known safety profile. And approaches like Kirkland's hit and run strategy will minimize potential exposure and risk.
He says the NIA is going to support a number of clinical trials using these new approaches. Pharmaceutical companies may feel that they can develop a unique part of a senolytic combination regimen that will justify their investment. And if they don't, countries with socialized medicine may take the lead in supporting such research with the goal of reducing the costs of treating aging patients.