Mark Humayun, MD, PhD, was recently featured on Trailblazers, an original podcast hosted by former CNN chairman and CEO Walter Isaacson. The Trailblazers podcast features leaders across society who have shaken up their fields, innovated in ways many would think impossible and charged forward to pioneer changes that excite the way our world operates. Isaacson, who has written best-selling books on innovators ranging from Leonardo da Vinci to Steve Jobs, sat with Humayun to discuss his career as a world-renown ophthalmologist and inventor. The episode highlights the challenges and victories Humayun has encountered along his journey to reverse blindness and restore a glimmer of hope to vision loss patients living in complete darkness.
Isaacson opens the podcast episode, entitled “Eyesight: Vision’s Visionaries,” with the story of Humayun succeeding in his first attempt to use electrodes to stimulate vision during eye surgery. He recounts the miraculous moment in 1992 when Humayun confirmed that his patient, blind for 50 years, was able to see a small but encouraging flicker of light while lying on the operating table. That light, which his patient described as looking like “a candle far off in the distance on a dark night,” marked a turning point in Humayun’s career and a monumental step forward in the field of vision science.
Almost three decades later, Humayun continues to pioneer groundbreaking advancements in ophthalmology and vision restoration. Humayun is widely recognized for his invention of the world’s first artificial retina, which has restored partial vision to hundreds of patients who were previously completely blind. Humayun and his team continue working to surmount the challenges of recreating one of our most sophisticated senses using a network of electrodes, and their current studies are focused on increasing clarity and adding color vision to their artificial sight system. But perhaps the truest measure of Humayun’s success as a trailblazer lies in the most basic and human experiences his patients have regained thanks to their implants: patients often share stories of watching fireworks on the Fourth of July, appreciating the lights on a Christmas tree, or experiencing the joy of playing with their young grandchildren thanks to the gift of sight their implants have given them.
“Everyone said, ‘This cannot happen,’” Humayun explains on Trailblazers, referring to the many obstacles that complicate creating a bionic eye implant, such as the delicacy of the human retina and the challenge of developing an electrode array capable of creating signals that the human brain can discern as meaningful images. “This was actually science fiction,” Humayun surmises, “and we made it science reality.”
To listen to the full podcast episode, click here.
Mark Humayun, MD, PhD, was included in a recent analysis out of Stanford University highlighting the world’s leading scientists across 22 fields of research and 176 sub-fields. Within the category of “ophthalmology & optometry,” Humayun ranks among the top 0.2% of his peers.
A recent Stanford study ranked Mark Humayun, MD, PhD, as one of the world’s top scientists. (Image credit: Jill Greenberg)
The rankings were calculated based on metrics such as the number of times a scientist’s research has been cited throughout the individual’s career. The analysis also accounted for each person’s h-index score, which attempts to quantify the scientist’s research productivity balanced with the impact that the research has made on the scientific field.
Humayun, a vitreoretinal surgeon and prolific inventor of biomedical devices, is widely known for developing the world’s first artificial retina. In 2016, Humayun received the National Medal of Technology and Innovation from President Barack Obama for developing the Argus II retinal prosthesis, which restores partial vision to patients with total retinal blindness.
Some of Humayun’s other accolades include election to both the National Academy of Medicine (NAM) and National Academy of Engineering (NAE), the 2020 Medal for Innovations in Healthcare Technology from the Institute of Electrical and Electronics Engineers (IEEE), “Inventor of the Year” from R&D Magazine in 2005, and distinction as one of the top 1% of ophthalmologists in U.S. News & World Report.
Humayun currently serves as director of the USC Dr. Allen and Charlotte Ginsburg Institute for Biomedical Therapeutics and co-director of the USC Roski Eye Institute. He also holds the titles of University Professor and Cornelius J. Pings Chair in Biomedical Sciences at USC.
On November 20th, 2020, the USC Dr. Allen and Charlotte Ginsburg Institute for Biomedical Therapeutics awarded its inaugural Mordechai “Mort” Arditti Award for Excellence to Alejandra Gonzalez-Calle, PhD, a postdoctoral researcher working to develop vision science innovations at the USC Ginsburg Institute.
Dr. Alejandra Gonzalez-Calle, the inaugural recipient of the Mordechai “Mort” Arditti Award for Excellence
Gonzalez-Calle grew up in Medellín, Colombia, and earned a BS in biomedical engineering at La Escuela de Ingenieria de Antioquia. As an undergraduate student, she planned to dedicate her career to developing affordable prosthetic limbs. After an accident that caused her to lose vision in her right eye, however, she redirected her energy toward advancing the field of vision science.
In 2009, Gonzalez-Calle reached out to Mark Humayun, MD, PhD, with the hope that she could pursue a research internship at his team’s USC lab. Humayun and his colleagues had an impressive record of churning out engineering-based solutions to address the biological anomalies causing vision loss, and Gonzalez-Calle aspired to join the ranks of this innovative team. That internship ultimately blossomed into over a decade and counting of collaboratively pioneering interdisciplinary, translational approaches to address some of the most confounding challenges in vision science. During that time, Gonzalez-Calle received one of the USC Viterbi School of Engineering’s highest research awards to support her pursuit of a master’s degree in biomedical engineering, and she later went on to earn a PhD in biomedical engineering in 2017.
Some of Gonzalez-Calle’s most meaningful experiences working with the USC Ginsburg Institute team include fine-tuning the Argus II retinal prosthesis to restore eyesight to patients suffering from complete retinal blindness and contributing to the development of a novel stem cell-based retinal implant for patients with AMD. Recently, she worked with a multidisciplinary team that was able to demonstrate, for the first time, that noninvasive electrical stimulation could be used to slow retinal degeneration in pre-clinical models.
Throughout the years spent working on these remarkable feats in biomedical engineering, Gonzalez-Calle has remained continuously inspired by seeing how the projects to which she has contributed can tangibly enhance patients’ lives. “Being able to see our projects evolve from the basic research stage to the point where they are implanted in patients, and then ultimately seeing how much of a difference these interventions can make in patients’ lives, is what makes me so passionate about what I’m doing,” Gonzalez-Calle says.
Receiving the inaugural Mordechai Arditti Award for Excellence carries special meaning for Gonzalez-Calle due to the fact that the late Arditti was an important mentor of hers throughout her training. Arditti, an electrical engineer by training, often contributed to and enhanced Gonzalez-Calle’s projects by helping to build circuits and essential electrical components of the biomedical devices on which Gonzalez-Calle worked. “He was such a special person for all of us,” Gonzalez-Calle remembers. “Besides being a mentor, he was also a friend to all the PhD students. I’m very grateful to receive this award and to feel like it’s coming from him, even though he’s not here with us anymore.”
Vitreoretinal surgeons Amir Kashani, MD, PhD (left) and Mark Humayun, MD, PhD (right) pioneered a new surgical procedure to treat dry age-related macular degeneration.
Dry age-related macular degeneration (dry AMD) poses a significant clinical challenge. It is one of the leading causes of progressive blindness, robbing millions of people over the age of 65 of their central vision, and it often hinders patients’ abilities to read books, drive and discern the faces of their loved ones. Although vitamin-based supplements may slow progression, no treatments currently exist.
A team of physicians and scientists at the USC Dr. Allen and Charlotte Ginsburg Institute for Biomedical Therapeutics (Ginsburg Institute) saw in this situation an opportunity to innovate and pioneer a novel treatment approach for dry AMD patients. Theirs has been a feat of scientific and surgical prowess, and over a decade of their diligence and ingenuity has resulted in what may become the first FDA-approved treatment to transform the prospects of regaining vision for millions of patients.
The Ginsburg Institute team, led by vitreoretinal surgeons Amir Kashani, MD, PhD, associate professor of ophthalmology at the Keck School of Medicine, and Mark Humayun, MD, PhD, director of the Ginsburg Institute and co-director of the USC Roski Eye Institute, developed a stem cell-based retinal implant and accompanying surgical procedure to help restore vision to dry AMD patients. Their innovative approach and insights from their phase 1/2a clinical trial are described in the latest print issue of the American Academy of Ophthalmology’s journal Ophthalmology Retina.
DESIGNING THE IMPLANT
The team accomplished a remarkable multi-part feat that required inventiveness at every turn, starting with designing the novel retinal implant. Dry AMD causes a single layer of cells in the retina called the retinal pigment epithelium (RPE) to deteriorate. The Ginsburg Institute team decided to utilize stem cells to grow RPE tissue in the lab, with the ultimate goal of implanting those cells in patients’ eyes to slow or reverse the damage. Other scientists had attempted to inject stem cell-derived RPE cells into the retina, but had trouble getting the cells to evenly disperse; the Ginsburg Institute scientists instead created a thin membrane made of parylene on which to grow the cells in a single, even layer. Once they had created this RPE layer, the next challenge was to successfully implant it in the eye.
“In practice, being able to get underneath the retina, which is only about a quarter of a millimeter thick, to physically replace the RPE cell layer is a challenging task,” explains Kashani, who is lead author of the publication. “Normally we don’t operate underneath the retina. It’s a place you generally try to avoid during surgery, so that has been a very novel, challenging aspect of delivering these stem cells.”
There are very few tools for performing surgery within the subretinal space. Most available tools were designed 30 to 40 years ago, are relatively bulky and are generally meant to remove scar tissue or other lesions rather than insert anything into the subretinal space. The Ginsburg Institute team decided that the most promising option was to start fresh and design a brand-new tool to fit their purpose.
ENGINEERING THE TOOL
This new tool had to fit a number of criteria: it needed to be made of completely non-toxic materials so as not to harm patients, its design had to be easily reproducible, and it had to be small enough—on a scale of millimeters—to perform minimally invasive surgery inside the eye but large enough to prevent crushing the tissue implant it was meant to deliver.
The surgeons worked with materials and design engineers at the Ginsburg Institute to create single-use forceps with an internal compartment to encapsulate the implant and a roller-style thumbwheel to deploy it. The implant itself is shaped much like a champagne bottle, and the forceps grab onto the narrow end. Rolling the implant into the device’s compartment causes it to fold into a curved shape, and the surgeon can ultimately release it to lay flat inside the eye.
PIONEERING THE SURGICAL TECHNIQUE
With the new instrument and implant came an entirely novel surgical approach. Kashani and Humayun needed to figure out how to create space for the implant in the location of geographic atrophy, which is what doctors call the area of tissue degeneration. To do so, the surgeons decided to create an artificial retinal detachment using a technique called bleb formation, in which a small pocket of space is formed under the retina. “Normally we treat retinal detachments, we don’t make them. In this particular case, we had to create a very well-controlled retinal detachment within an area of scar tissue that is very adherent to the surroundings,” says Kashani. “The challenge was to separate it without damaging the retina.”
In pre-clinical models, creating a bleb alone proved insufficient; the surgeons had to innovate again and ultimately used water pressure to dissect one cell layer from another in a process called targeted hydrodissection. To monitor progress during surgery and prevent complications, the team utilized an advanced imaging technique called optical coherence tomography (OCT) to visualize the dissection at the cellular level. “One part of our job was to make this a very doable surgery and I think we have achieved that with this study,” Kashani says.
“Without tools like OCT, it would be very difficult to visualize the damage we need to treat,” Kashani explains. He emphasizes that in addition to using OCT intraoperatively, he sees a promising role for the technology to be used in earlier-stage AMD patients to monitor the progression of their geographic atrophy. “It’s not a standard of practice to use OCT and other diagnostic methods to detect early and subtle disease changes, but that may prove to be really important for classifying disease and treating it in the future.”
Kashani adds that one of the most rewarding aspects of the entire clinical trial process has been working with his patients and witnessing their commitment to making this translation from research lab to clinical practice possible. “None of this is happening by magic. Patients are volunteering, and they’re taking a chance for the sake of advancing medicine and potentially helping countless other patients down the road. We always appreciate that effort and we thank the patients and their families, too.”
––
This phase 1/2a trial was supported in large part by a $3.73 million grant from the California Institute for Regenerative Medicine (CIRM). Other authors on the study include Jeremy Uang, BS, of the USC Roski Eye Institute, USC Ginsburg Institute for Biomedical Therapeutics and Department of Ophthalmology, Keck School of Medicine of USC; Melissa Mert, MS, of the Southern California Clinical and Translational Science Institute and USC Department of Preventive Medicine (Biostatistics); Firas Rahhal, MD, of the Retina-Vitreous Associates Medical Group; Clement Chan, MD, of the Southern California Desert Retina Consultants, Palm Desert; Robert L. Avery, MD, of the California Retinal Consultants, Santa Barbara; Pravin Dugel, MD of the Retinal Consultants of Arizona, Phoenix; Sanford Chen, MD, of Orange County Retina, Santa Ana; Jane Lebkowski, PhD, of Regenerative Patch Technologies LLC; Dennis O. Clegg, PhD, of the center for Stem Cell Biology and Engineering, University of California; and David R. Hinton, MD, of the Department of Pathology, Keck School of Medicine of USC.
The California Institute for Regenerative Medicine (CIRM) recently awarded $3.73 million to Mark Humayun, MD, PhD, who serves as director of the USC Dr. Allen and Charlotte Ginsburg Institute for Biomedical Therapeutics and co-director of the USC Roski Eye Institute. The grant is part of CIRM’s translational research program to propel California forward as a hub of regenerative medicine breakthroughs. The funding will support researchers at the USC Ginsburg Institute as they develop a new treatment for dry age-related macular degeneration (dry AMD) –– a disease that has historically been considered difficult to treat.
This injection is not a man-made drug, but is instead composed of molecules produced by healthy retinal cells cultured in the laboratory. The researchers have already demonstrated that an intraocular injection of these molecules stimulates healing and slows down retinal degeneration in pre-clinical studies. The team’s prestigious CIRM grant is intended to accelerate the project’s transition to the clinical trial stage, thanks to its potential to benefit society by filling an unmet medical need.
One innovation inspires another
Approximately two million Americans currently live with advanced forms of AMD, and more than seven million deal with early-stage symptoms of the disease. Of those cases, 85-90% are the dry form of AMD. The condition is characterized by the progressive deterioration of the macula, or the region of the retina responsible for the clearest, most focused vision in the center of one’s field of view. A single layer of cells under the macula called the retinal pigment epithelium (RPE) is responsible for nurturing the eye’s photoreceptor cells, which lie directly on top of the RPE and perceive light.
As dry AMD progresses, patients perceive a dark spot obscuring the center of their vision. (Image: National Eye Institute, National Institutes of Health)
As the macula deteriorates and RPE cells die off, the photoreceptor cells necessary for vision gradually follow suit. Soon, patients begin to perceive a dark spot in the center of their visual field that can interfere with anything from reading to recognizing the faces of loved ones. The disease robs patients of both their eyesight and a great deal of their autonomy.
With the help of a CIRM Disease Team grant, a team of USC Ginsburg Institute researchers recently used stem cells to develop a retinal implant composed of a single layer of RPE cells to replace the degenerating part of the macula. Humayun, working alongside Amir Kashani, MD, PhD, surgically placed implants in 15 patients’ retinas. Although the trial was only intended to assess the implant’s safety, the team observed early signs of therapeutic benefit and a few patients even regained some of their eyesight. That project is currently poised to enter a larger clinical trial phase with the goal of becoming the first ever FDA-approved treatment for late-stage dry AMD.
While testing the implants in pre-clinical models, the team made an intriguing observation: the implanted cells had a restorative effect not only in the exact location they were placed, but also on the surrounding retinal tissue.
The researchers attributed this phenomenon to something they call the paracrine effect: cells from the implant produce chemical messages that communicate with surrounding cells –– a process known to biologists as “paracrine signaling” –– which causes the degenerating native cells to behave more like the healthy, newly implanted ones.
USC Ginsburg Institute researchers are culturing healthy retinal cells and harnessing the biological factors they produce to create therapeutic injections and reverse the symptoms of dry AMD. (Image: Kabir Ahluwalia)
The researchers asked themselves a key question: if these biological factors alone could have a restorative effect on a degenerating retina, could the team create an injectable solution containing the factors to complement the implant as an early-stage intervention for dry AMD?
So far, the answer appears to be yes. Cells used in the implants are grown in the lab in a nutritious broth called the media, and as they grow, the molecular factors they produce are released into the media. By harvesting that factor-filled fluid and delivering it as an intraocular injection, the team has already seen success in dramatically slowing down the progression of retinal cell loss in pre-clinical models of retinal degeneration. The team’s long-term goal is to develop a therapeutic injection for early-stage patients to slow disease progression, while patients whose diseases have progressed to the point of blindness can receive implants.
Sights set on a future cure
Now that the researchers know this media holds promise as a therapeutic injection, the next step is to fully characterize its components. While the team has narrowed down the number of potentially therapeutic molecules in the media, no single constituent seems to have a strong effect on its own, meaning the factors may work together in a synergistic way to restore retinal function. Funding from the CIRM grant is meant to expedite the process of characterizing the media and creating a stable, reproducible therapeutic injection for eventual use in humans.
Kabir Ahluwalia, a doctoral student in the USC School of Pharmacy working on the project, explains that this research holds particular promise for those estimated seven million early-stage patients making up the majority of dry AMD cases. Early-stage AMD patients can currently benefit from specific nutritional supplements that slow down disease progression by about 25%, but many patients still need additional therapy. This novel injection of soluble growth factors could potentially serve as an ideal future treatment to prevent vision loss and provide renewed hope for these patients.
Dr. Mark Humayun from the USC Dr. Allen and Charlotte Ginsburg Institute for Biomedical Therapeutics was recently featured in Nature Outlook for his outstanding contributions to advance the treatment of blindness. The article highlighted a handful of the world’s top researchers tackling the problem of retinal degeneration, which is the leading cause of blindness in developed countries.
Image: Nature Outlook
Dr. Humayun’s Argus series implants were showcased amongst the most cutting-edge approaches to restoring eyesight for patients with some functional retinal cells still intact. The Argus II “bionic eye” consists of an electrode array that is implanted on the surface of the retina. The patient wears glasses equipped with a small video camera that transmits signals wirelessly to the implant. The electrodes stimulate the retina, which then communicates those signals to the brain. Over 300 patients have received the Argus II prosthesis and have regained their perception of light patterns, movement and basic shapes.
For patients who have completely lost functionality of the retina, Humayun and his colleagues at Second Sight have a different approach: sending signals from a camera directly to the brain.
The researchers have developed a chip, called Orion, which is surgically implanted on the outer surface of the very back of one’s brain. This region of the brain, called the visual cortex, is responsible for processing and interpreting information from the eyes. Like Argus II, Orion receives signals from a camera mounted on the patient’s glasses, and the brain can then convert those signals into visual information. So far, the chip has been successfully implanted in five patients with limited or no light perception. The trial is still its early stages, but the preliminary results look promising and Humayun hopes the chip will receive FDA approval in a few years.
To read the entire Nature Outlook article, click here.
