Category: Regenerative Medicine

Tissue Regeneration might One Day Replace Root Canals

Photo by Tima Miroshnichenko on Pexels

Tissue regeneration might one day replace the pain and discomfort of a root canal for most people. ADA Forsyth scientists are testing a novel technology to treat endodontic diseases (diseases of the soft tissue or pulp of the teeth) more effectively. The technology may also even be applicable to other parts of the body, such as helping to regrow bones.

The study, published in The Journal of Dental Research, demonstrates regenerative properties of resolvins, specifically Resolvin E1 (RvE1), when applied to dental pulp. Resolvins are part of a greater class of Specialised Proresolving Mediators (SPMs). This class of molecule is naturally produced by the body and is exquisitely effective in the control of excess inflammation associated with disease.

“Pulpitis (inflammation of dental pulp) is a very common oral health disease that can become a serious health condition if not treated properly,” said Dr Thomas Van Dyke, Vice President at the Center for Clinical and Translational Research at ADA Forsyth, and a senior scientist leading the study.

“Root canal therapy (RCT) is effective, but it does have some problems since you are removing significant portions of dentin, and the tooth dries out leading to a greater risk of fracture down the road. Our goal is to come up with a method for regenerating the pulp, instead of filling the root canal with inert material.”

Inflammation of this tissue is usually caused by damage to the tooth through injury, cavities or cracking, and the resulting infection can quickly kill the pulp and cause secondary problems if not treated.

The study applied RvE1 to different levels of infected and damaged pulp to explore its regenerative and anti-inflammatory capacities.

There were two major findings. First, they showed RvE1 is very effective at promoting pulp regeneration when used in direct pulp-capping of vital or living pulp (replicating conditions of reversible pulpitis). They were also able to identify the specific mechanism supporting tissue regeneration.

Second, the scientists found that placing RvE1 on exposed and severely infected and necrotic pulp did not facilitate regeneration.

However, this treatment did effectively slow down the rate of infection and treat the inflammation, preventing the periapical lesions (abscesses) that typically occur with this type of infection.

Previous publications have shown that if the infected root canal is cleaned before RvE1 treatment, regeneration of the pulp does occur.

While this study focused on this technology in treating endodontic disease, the potential therapeutic impact is far reaching.

Dr Van Dyke explained, “because application of RvE1 to dental pulp promotes formation of the type of stem cells that can differentiate into dentin (tooth), bone, cartilage or fat, this technology has huge potential for the field of regenerative medicine beyond the tissues in the teeth. It could be used to grow bones in other parts of the body, for instance.”

Source: Forsyth Institute

Is Stem Cell Therapy for Knee Osteoarthritis Worthwhile?

Photo by Towfiqu barbhuiya:

Cell therapy has been explored as a new regenerative treatment for osteoarthritis, but the efficacy of stem cell transplantation from different sources for the treatment of knee osteoarthritis (KOA) remains controversial. A recent analysis of all relevant published studies indicates that stem cell transplantation from different sources is effective for treating knee osteoarthritis, the most prevalent chronic joint disease.

The review and meta-analysis, which is published in the Journal of Orthopaedic Research, included 16 studies involving 875 patients with knee osteoarthritis (441 in the stem cell transplantation group and 434 in the control group). Stem cell treatment was associated with significant reductions in patient-reported pain from the third month onwards. The most significant pain relief at different postoperative months came from fat-derived and umbilical cord–derived stem cells. A patient’s own fat-derived stem cells resulted in better pain alleviation compared with those from other donors. Also, a patient’s own fat-derived stem cells led to the most effective recovery of knee joint function.

“Stem cell transplantation proved safe and effective for knee osteoarthritis treatment,” the authors wrote. “Different sources stem cells have a good effect on alleviating knee joint pain, restoring knee joint function, and minimising patient trauma.”

Source: Wiley

Vitamin B12 Plays a Key Role in Cellular Reprogramming and Tissue Regeneration

Photo by National Cancer Institute on Unsplash

Vitamin B12 is a well-known micronutrient that has long been acknowledged for its essential role in maintaining nerve function, supporting red blood cell production, and facilitating DNA synthesis, all vital processes for overall health. Researchers have now discovered that vitamin B12 also plays a pivotal role in cellular reprogramming and tissue regeneration. The findings have been published in the journal Nature Metabolism.

The research was focused on an experimental process known as cellular reprogramming which is thought to mimic the early phases of tissue repair. The IRB team found that cellular reprogramming in mice consumes large amounts of vitamin B12. Indeed, the depletion of vitamin B12 becomes a limiting factor that delays and impairs some aspects of the reprogramming process. Considering the abundance of vitamin B12 in the normal diet of mice, the investigators were surprised to observe that the simple supplementation of vitamin B12 significantly enhanced the efficiency of reprogramming.

Therapeutic potential in ulcerative colitis

The researchers validated their findings in a model of ulcerative colitis, demonstrating that the intestinal cells initiating repair undergo a process similar to cellular reprogramming and also benefit from vitamin B12 supplementation. Patients with intestinal bowel disease could potentially benefit from vitamin B12 supplementation.

“Our research uncovers a critical role of vitamin B12 in cellular reprogramming and tissue repair. These findings hold promise for regenerative medicine, with the potential to benefit patients through an improved nutrition,” says lead researcher Dr Manuel Serrano at IRB.

Understanding the role of vitamin B12 in cellular reprogramming

In this study, the researchers delved into the metabolic requirements of cellular reprogramming and found that vitamin B12 is a limiting factor for a particular branch of metabolism involved in a reaction known as methylation. Precisely, the DNA of the cells initiating reprogramming or tissue repair require very high levels of this methylation reaction and therefore of vitamin B12. The researchers discovered that vitamin B12 insufficiency during reprogramming or tissue repair resulted in significant epigenetic changes, leading to errors in the function of multiple genes.

“Supplementation with vitamin B12 corrected this imbalance, resulting in enhanced gene function fidelity and overall improved reprogramming efficiency,” confirms Dr. Marta Kovatcheva, first author of the study and a postdoctoral researcher in the same laboratory. Dr. Kovatcheva will open a new laboratory in 2024 at the Istituto Fondazione di Oncologia Molecolare ETS (IFOM) in Milan, Italy, which will be focused on the study of partially reprogrammed cells in vivo.

Separate study links vitamin B12 to lower inflammation

The group led by Dr. Serrano has recently published another study, in collaboration with the laboratory of Dr. Rosa Lamuela-Raventós at the University of Barcelona (UB), and Dr. Ramon Estruch at the Hospital Clínic of Barcelona, in which they concluded that people with higher levels of vitamin B12 in blood had lower levels of inflammatory markers (IL-6 and CRP). The researchers also observed a similar relationship in aged mice. These observations suggest that vitamin B12 exerts anti-inflammatory action by reducing these markers in the body and they provide valuable insights into the potential health benefits of vitamin B12.

Source: Institute for Research in Biomedicine (IRB Barcelona)

Are Stem Cell Therapies Really Superior for Knee Osteoarthritis?

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In a study published in Nature Medicine, investigators explored the mesenchymal stem cells’ potential as a game-changing treatment option for knee osteoarthritis. This type of treatment seeks to regenerate damaged tissue, treating the problem directly instead of seeking only to relieve symptoms. However, the availability of robust data from well-designed randomised controlled trials has been limited, particularly in comparison to the gold-standard of treatment for knee osteoarthritis (OA), corticosteroid injections (CSI).

Characterised by extensive damage to joints and debilitating pain, knee OA affects millions of people worldwide is the most common cause of chronic knee pain and has long posed a substantial clinical and economic burden.

In spite of advances in diagnosis, medications, and short-term pain management solutions, the elusive goal of a disease-modifying OA drug has remained out of reach. In recent years though, the use of stem cell therapy has gained traction as a promising alternative to surgery and for improving patients’ quality of life.  

The initial findings of this study describe a first-of-its-kind randomized clinical trial to identify the most effective source of cellular injections for knee OA. The research team compared three types of cellular preparations, including autologous bone marrow aspirate concentrate (BMAC), autologous stromal vascular fraction (SVF), and allogenic human umbilical cord tissue MSCs (UCT) against CSI. The primary outcome measures were the visual analogue scale (VAS) and the Knee Injury and Osteoarthritis Outcome Score (KOOS) for pain from baseline to one year. The question driving the research was whether cell therapies could outperform corticosteroids in the treatment of knee osteoarthritis at the one-year mark.

While the findings showed each group had a measurable improvement in pain and function, there was no significant advantage to using any of the tested cell products compared to the gold standard anti-inflammatory corticosteroid treatment at the 12-month follow-up regarding the change in VAS pain score from baseline. Similarly, the analysis of the KOOS pain score produced consistent results, with no significant differences between groups at the 12-month mark in the change in score from baseline.

“The study demonstrated no superiority of any cell therapy over corticosteroids in reducing pain intensity over the course of a year,” says Scott D. Boden, MD, director of the Emory Orthopaedics and Spine Center, and a senior author on the study. “While there is much enthusiasm about the regenerative capacity of stem cells, the findings call into question the comparative effectiveness of various injections for knee osteoarthritis and underscores the importance of a personalised approach in selecting the right treatment for each patient’s unique needs.”

The study’s extensive reach also extended to evaluating the safety of these procedures measuring every adverse reaction, ranging from mild joint discomfort and swelling to unrelated hospitalisations. Importantly, the study found no study-related serious adverse events or symptomatic knee infections across any of the treatment groups at any point during the follow-up.

According to Dr Boden, future papers from the ongoing analysis of our data will determine if certain subgroups of patients might preferentially benefit from one of these treatments more than another. The findings offer an important step forward in answering key questions about the comparative effectiveness of certain OA treatment options, but more in-depth analysis using MRIs and cellular analysis of each injectate will continue to help inform standards of care.

Source: Emory University

New Injectable Tissue Prosthesis Plugs and Regenerates Large Wounds

Researchers at the Institute of Basic Science (IBS) in South Korea have developed a novel approach to healing muscle injury by employing an ‘injectable tissue prosthesis’ in the form of conductive hydrogels and combining it with a robot-assisted rehabilitation system. They describe their research in a recent publication in the journal Nature.

A large wound such as a shark bite, with the loss of muscle and nerve in the wound cavity, results in a complete loss of motor/sensor function in the leg. If left untreated, such severe muscle damage would result in permanent loss of function and disability.

Traditional rehabilitation methods for these kinds of muscle injuries have long sought an efficient closed-loop gait rehabilitation system that merges lightweight exoskeletons and wearable/implantable devices. Such assistive prosthetic system is required to aid the patients through the process of recovering sensory and motor functions linked to nerve and muscle damage.

Unfortunately, the mechanical properties and rigid nature of existing electronic materials render them incompatible with soft tissues. This leads to friction and potential inflammation, stalling patient rehabilitation.

To overcome these limitations, the IBS researchers turned to a material commonly used as a wrinkle-smoothing filler, called hyaluronic acid. Using this substance, an injectable hydrogel was developed for ’tissue prostheses’, which can temporarily fill the gap of the missing muscle/nerve tissues while it regenerates. The injectable nature of this material gives it a significant advantage over traditional bioelectronic devices, which are unsuitable for narrow, deep, or small areas, and necessitate invasive surgeries.

Thanks to its highly ’tissue-like’ properties, this hydrogel seamlessly interfaces with biological tissues and can be easily administered to hard-to-reach body areas without surgery. The reversible and irreversible crosslinks within the hydrogel adapt to high shear stress during injection, ensuring excellent mechanical stability. This hydrogel also incorporates gold nanoparticles, which gives it decent electrical properties. Its conductive nature allows for the effective transmission of electrophysiological signals between the two ends of injured tissues. In addition, the hydrogel is biodegradable, removing the need for additional surgery.

With mechanical properties akin to natural tissues, exceptional tissue adhesion, and injectable characteristics, researchers believe this material offers a novel approach to rehabilitation.

Next, the researchers put this novel idea to the test in rodent models. To simulate volumetric muscle loss injury, a large chunk of muscle has been removed from the hind legs of these animals. By injecting the hydrogel and implanting the two kinds of stretchable tissue-interfacing devices for electrical sensing and stimulation, the researchers were able to improve the gait in the ‘injured’ rodents. The hydrogel prosthetics were combined with robot assistance, guided by muscle electromyography signals. Together, the two helped enhance the animal’s gait without nerve stimulation. Furthermore, muscle tissue regeneration was effectively improved over the long term after the conductive hydrogel was used to fill muscle damage.

The injectable conductive hydrogel developed in this study excels in electrophysiological signal recording and stimulation performance, offering the potential to expand its applications. It presents a fresh approach to the field of bioelectronic devices and holds promise as a soft tissue prosthesis for rehabilitation support.

Emphasizing the significance of the research, Professor SHIN Mikyung notes, “We’ve created an injectable, mechanically tough, and electrically conductive soft tissue prosthesis ideal for addressing severe muscle damage requiring neuromusculoskeletal rehabilitation. The development of this injectable hydrogel, utilizing a novel cross-linking method, is a notable achievement. We believe it will be applicable not only in muscles and peripheral nerves but also in various organs like the brain and heart.”

Professor SON Donghee added, “In this study, the closed-loop gait rehabilitation system entailing tough injectable hydrogel and stretchable and self-healing sensors could significantly enhance the rehabilitation prospects for patients with neurological and musculoskeletal challenges. It could also play a vital role in precise diagnosis and treatment across various organs in the human body.”

The research team is currently pursuing further studies to develop new materials for nerve and muscle tissue regeneration that can be implanted in a minimally invasive manner. They are also exploring the potential for recovery in various tissue damages through the injection of the conductive hydrogel, eliminating the need for open surgery.

Source: Institute for Basic Science

3D-Printed Structures Hold Promise for Repair of Traumatic Brain Injuries

Researchers at the University of Oxford have produced an engineered tissue representing a simplified cerebral cortex by 3D printing human stem cells. The results, published in the journal Nature Communications, showed that, when implanted into mouse brain slices, the structures became integrated with the host tissue.

The breakthrough technique could lead to tailored repairs for brain injuries. The researchers demonstrated for the first time that neural cells can be 3D-printed to mimic the architecture of the cerebral cortex.

Brain injuries, including those caused by trauma, stroke and surgery for brain tumours, typically result in significant damage to the cerebral cortex. For example, each year, around 70 million people globally suffer from traumatic brain injury (TBI), with 5 million of these cases being severe or fatal. Currently, there are no effective treatments for severe brain injuries, leading to serious impacts on quality of life.

Tissue regenerative therapies, especially those in which patients are given implants derived from their own stem cells, could be a promising route to treat brain injuries in the future. Up to now, however, there has been no method to ensure that implanted stem cells mimic the architecture of the brain.

In this new study, the University of Oxford researchers fabricated a two-layered brain tissue by 3D printing human neural stem cells. When implanted into mouse brain slices, the cells showed convincing structural and functional integration with the host tissue.

Lead author Dr Yongcheng Jin (Department of Chemistry, University of Oxford) said: ‘This advance marks a significant step towards the fabrication of materials with the full structure and function of natural brain tissues. The work will provide a unique opportunity to explore the workings of the human cortex and, in the long term, it will offer hope to individuals who sustain brain injuries.’

The cortical structure was made from human induced pluripotent stem cells (hiPSCs), which have the potential to produce the cell types found in most human tissues. A key advantage of using hiPSCs for tissue repair is that they can be easily derived from cells harvested from patients themselves, and therefore would not trigger an immune response.

The hiPSCs were differentiated into neural progenitor cells for two different layers of the cerebral cortex, by using specific combinations of growth factors and chemicals. The cells were then suspended in solution to generate two ‘bioinks’, which were then printed to produce a two-layered structure. In culture, the printed tissues maintained their layered cellular architecture for weeks, as indicated by the expression of layer-specific biomarkers.

When the printed tissues were implanted into mouse brain slices, they showed strong integration, as demonstrated by the projection of neural processes and the migration of neurons across the implant-host boundary. The implanted cells also showed signalling activity, which correlated with that of the host cells. This indicates that the human and mouse cells were communicating with each other, demonstrating functional as well as structural integration.

The researchers now intend to further refine the droplet printing technique to create complex multi-layered cerebral cortex tissues that more realistically mimic the human brain’s architecture. Besides their potential for repairing brain injuries, these engineered tissues might be used in drug evaluation, studies of brain development, and to improve our understanding of the basis of cognition.

The new advance builds on the team’s decade-long track record in inventing and patenting 3D printing technologies for synthetic tissues and cultured cells.

Senior author Dr Linna Zhou (Department of Chemistry, University of Oxford) said: “Our droplet printing technique provides a means to engineer living 3D tissues with desired architectures, which brings us closer to the creation of personalised implantation treatments for brain injury.”

Senior author Associate Professor Francis Szele (Department of Physiology, Anatomy and Genetics, University of Oxford) added: “The use of living brain slices creates a powerful platform for interrogating the utility of 3D printing in brain repair. It is a natural bridge between studying 3D printed cortical column development in vitro and their integration into brains in animal models of injury.”

Senior author Professor Zoltán Molnár (Department of Physiology, Anatomy and Genetics, University of Oxford) said: “Human brain development is a delicate and elaborate process with a complex choreography. It would be naïve to think that we can recreate the entire cellular progression in the laboratory. Nonetheless, our 3D printing project demonstrates substantial progress in controlling the fates and arrangements of human iPSCs to form the basic functional units of the cerebral cortex.”

Source: University of Oxford

Neuroscientists Regenerate Neurons in Mice with Spinal Cord Injury

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In a new study using mice, neuroscientists have uncovered a crucial component for restoring functional activity after spinal cord injury. In the study, published in Science, the researchers showed that re-growing specific neurons back to their natural target regions led to recovery, while random regrowth was not effective.

In a 2018 study in Naturethe team identified a treatment approach that triggers axons to regrow after spinal cord injury in rodents. But even as that approach successfully led to the regeneration of axons across severe spinal cord lesions, achieving functional recovery remained a significant challenge.

For the new study, the team of researchers from UCLA, the Swiss Federal Institute of Technology, and Harvard University aimed to determine whether directing the regeneration of axons from specific neuronal subpopulations to their natural target regions could lead to meaningful functional restoration after spinal cord injury in mice. They first used advanced genetic analysis to identify nerve cell groups that enable walking improvement after a partial spinal cord injury.

The researchers then found that merely regenerating axons from these nerve cells across the spinal cord lesion without specific guidance had no impact on functional recovery. However, when the strategy was refined to include using chemical signals to attract and guide the regeneration of these axons to their natural target region in the lumbar spinal cord, significant improvements in walking ability were observed in a mouse model of complete spinal cord injury.

“Our study provides crucial insights into the intricacies of axon regeneration and requirements for functional recovery after spinal cord injuries,” said Michael Sofroniew, MD, PhD, professor of neurobiology at the David Geffen School of Medicine at UCLA and a senior author of the new study. “It highlights the necessity of not only regenerating axons across lesions but also of actively guiding them to reach their natural target regions to achieve meaningful neurological restoration.”

The authors say understanding that re-establishing the projections of specific neuronal subpopulations to their natural target regions holds significant promise for the development of therapies aimed at restoring neurological functions in larger animals and humans. However, the researchers also acknowledge the complexity of promoting regeneration over longer distances in non-rodents, necessitating strategies with intricate spatial and temporal features. Still, they conclude that applying the principles laid out in their work “will unlock the framework to achieve meaningful repair of the injured spinal cord and may expedite repair after other forms of central nervous system injury and disease.”

Source: University of California – Los Angeles Health Sciences

Microvascular Implants may Enable Faster Healing of Chronic Wounds

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Researchers in South Korea have achieved a ground-breaking milestone in tissue regeneration with a technology that utilises autologous blood to produce three-dimensional microvascular implants. These implants hold immense potential for various applications requiring vascular regeneration, including the treatment of chronic wounds in conditions such as diabetes, as well as the potential for scarless healing.

Led by Professor Joo H. Kang from the Department of Biomedical Engineering at UNIST, the team successfully developed a microfluidic system capable of processing blood into an artificial tissue scaffold. Unlike previous methods based on cell-laden hydrogel patches using fat tissues or platelet-rich plasma, this innovative approach enables the creation of robust microcapillary vessel networks within skin wounds. The utilisation of autologous whole blood ensures compatibility and promotes effective wound healing.

Creating optimal stiffness

The technology, described in Advanced Materials, leverages microfluidic shear stresses to align bundled fibrin fibres along the direction of blood flow streamlines while activating platelets. This alignment and activation process results in moderate stiffness within the microenvironment – optimal conditions for facilitating endothelial cell maturation and vascularisation. When applied as patches to rodent dorsal skin wounds, these implantable vascularided engineered thrombi (IVETs) demonstrated superior wound closure rates (96.08 ± 1.58%), increased epidermis thickness, enhanced collagen deposition, hair follicle regeneration, reduced neutrophil infiltration, and accelerated wound healing through improved microvascular circulation.

Chronic wounds pose significant challenges as they often fail to heal properly over time and can lead to complications associated with diabetes and vascular diseases. In severe cases, they may result in sepsis due to insufficient oxygen supply and nutrients caused by loss of blood vessels.

By harnessing the power of microfluidic technology, Professor Kang’s team transformed autologous blood into IVETs suitable for transplantation. These IVETs were implanted into full-thickness skin wounds in experimental mice, resulting in rapid and scarless recovery of the entire damaged area. The study demonstrated successful regeneration of blood vessels within the wound site, facilitated movement of immune cells crucial for wound healing, and accelerated overall recovery.

Furthermore, the team evaluated the efficacy of IVET transplantation by infecting the skin damage area with methicillin-resistant Staphylococcus aureus (MRSA). When artificial blood clots made from autologous blood were implanted into infected mice, quick vascular recovery was observed alongside enhanced migration of proteins and immune cells to combat bacterial infection. Additionally, collagen formation and hair follicle regeneration occurred without scarring.

These ground-breaking findings pave the way for advanced techniques in tissue engineering and wound healing using autologous blood-based implants. With further development and refinement, this technology holds tremendous potential to revolutionise treatment strategies for chronic wounds while contributing to advancements in regenerative medicine.

Source: Ulsan National Institute of Science and Technology (UNIST)

New Regeneration Drug for Spinal Cord Injury Passes Safety Check

Researchers in the UK have evaluated a potential drug for the treatment of spinal cord injury (SCI), which could potentially regrow damaged nerves, and found it to be safe and tolerable. The results of their Phase 1 clinical trial were published in British Journal of Clinical Pharmacology and evaluated the KCL-286 drug, which activates retinoic acid receptor beta (RARb) in the spine to promote recovery.

There are no licensed drugs that can fix the adult central nervous system’s inability to regenerate. Implants have been able to restore some function, but for most, spinal cord injuries are life-changing.

Previous studies have shown that nerve growth can be stimulated by activating the RARb2 receptor, but no drug suitable for humans has been developed. KCL-286, an RARb2 agonist, was developed by Professor Corcoran and team and used in a first in man study to test its safety in humans.

The study by the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London, recruited 109 healthy males in a single ascending dose (SAD) adaptive design with a food interaction (FI) arm, and multiple ascending dose (MAD) arm. Participants in each arm were further divided into different dose treatments.

SAD studies are designed to establish the safe dosage range of a medicine by providing participants with small doses before gradually increasing the dose provided. Researchers look for any side effects, and measure how the medicine is processed within the body. MAD studies explore how the body interacts with repeated administration of the drug, and investigate the potential for a drug to accumulate within the body.

Researchers found that participants were able to safely take 100mg doses of KCL-286, with no severe adverse events.

Professor Jonathan Corcoran, Professor of Neuroscience and Director of the Neuroscience Drug Discovery Unit, at King’s IoPPN and the study’s senior author said, “This represents an important first step in demonstrating the viability of KCL-286 in treating spinal cord injuries. This first-in-human study has shown that a 100mg dose delivered via a pill can be safely taken by humans. Furthermore, we have also shown evidence that it engages with the correct receptor.

“Our focus can hopefully now turn to researching the effects of this intervention in people with spinal cord injuries.”

Dr Bia Goncalves, a senior scientist and project manager of the study, and the study’s first author from King’s IoPPN said, “Spinal Cord Injuries are a life changing condition that can have a huge impact on a person’s ability to carry out the most basic of tasks, and the knock-on effects on their physical and mental health are significant.

“The outcomes of this study demonstrate the potential for therapeutic interventions for SCI, and I am hopeful for what our future research will find.”

The researchers are now seeking funding for a Phase 2a trial studying the safety and tolerability of the drug in those with SCI.

Source: King’s College London

Backdoor to the Inner Ear Allows Delivery of Gene Therapy

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An international team of researchers has developed a new method to deliver drugs into the inner ear, according to a new study in Science Translational Medicine. The discovery was possible by harnessing the natural flow of fluids in the brain and employing a little-understood backdoor into the cochlea. When combined to deliver a gene therapy that repairs inner ear hair cells, the researchers were able to restore hearing in deaf mice.

“These findings demonstrate that cerebrospinal fluid transport comprises an accessible route for gene delivery to the adult inner ear and may represent an important step towards using gene therapy to restore hearing in humans,” says lead author Barbara Canlon, professor at Karolinska Institutet.

The number of people worldwide predicted to have mild to complete hearing loss is expected to grow to around 2.5 billion by mid-century.  The primary cause is the death or loss of function of hair cells found in the cochlea – which relay sounds to the brain – due to mutations of critical genes, aging, noise exposure, and other factors. 

While hair cells do not naturally regenerate in humans and other mammals, gene therapies have shown promise and in separate studies have successfully repaired the function of hair cells in neo-natal and very young mice.

“However, as both mice and humans age, the cochlea, already a delicate structure, becomes enclosed in the temporal bone. At this point, any effort to reach the cochlea and deliver gene therapy via surgery risks damaging this sensitive area and altering hearing,” says Barbara Canlon.

In the new study, the researchers describe a little-understood passage into the cochlea called the cochlear aqueduct. The cochlear aqueduct is a thin boney channel no larger than several strands of hair. 

Channel for spinal fluid

A new study shows that the cochlear aqueduct acts as a conduit between the cerebrospinal fluid found in the inner ear and the rest of the brain. 

Scientists are developing a clearer picture of the mechanics of the glymphatic system, the brain’s unique process of removing waste. Because the glymphatic system pumps cerebrospinal fluid deep into brain tissue to wash away toxic proteins, researchers have been eyeing it as a potential new way to deliver drugs into the brain, a major challenge in developing drugs for neurological disorders. 

The new study represented an opportunity to put the drug delivery potential of the glymphatic system to the test, while at the same time targeting a previously unreachable part of the auditory system.   

Employing several imagining and modeling technologies, the researchers were able to develop a detailed portrait of how fluid from other parts of the brain flows through the cochlear aqueduct and into the inner ear.

The team then injected an adeno-associated virus into the cisterna magna, a large reservoir of cerebrospinal fluid found at the base of the skull. 

The virus found its way into the inner ear via the cochlear aqueduct and delivered a gene therapy that expresses a protein called vesicular glutamate transporter-3, which enables the hair cells to transmit signals and rescue hearing in adult deaf mice. 

“This new delivery route into the ear may not only serve the advancement of auditory research but also prove useful when translated to humans with progressive genetic-mediated hearing loss,” says Barbara Canlon.

Source: Karolinska Institutet