Unanticipated Ear Entrance Uncovers Fresh Prospects for Hearing Recovery
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A groundbreaking study led by Maiken Nedergaard and colleagues has revealed a potential game-changer in the restoration of hearing for individuals with genetic-mediated hearing loss [1]. The team's discovery, published in Science Translational Medicine, introduces a novel approach to deliver gene therapy via cerebrospinal fluid (CSF) transport to the adult inner ear.
The new method leverages the CSF conduit, bypassing traditional barriers that limit access to the adult inner ear. This minimally invasive delivery technique could pave the way for effective intervention in adults who have already developed hearing loss, as opposed to treatments that have primarily focused on early life stages [1].
The study, conducted in collaboration with researchers from the University of Rochester, University of Copenhagen, and the Karolinska Institute in Stockholm, Sweden, targets the previously unreachable part of the auditory system, the inner ear. By harnessing the natural flow of fluids in the brain and employing a little-understood backdoor into the cochlea, the researchers were able to deliver a gene therapy that repairs inner ear hair cells, restoring hearing in deaf mice [1].
The cochlear aqueduct, a thin boney channel no larger than a single strand of hair, acts as a conduit between the CSF found in the inner ear and the rest of the brain. The team injected an adeno-associated virus into the cisterna magna, a large reservoir of cerebrospinal fluid found at the base of the skull, which then delivered the gene therapy into the inner ear via the cochlear aqueduct [1].
The complex movement of fluids driven by the glymphatic system extends to the eyes, peripheral nervous system, and the ear. This discovery not only provides a promising therapeutic avenue for reversing or mitigating genetic hearing impairments in humans but also opens up possibilities for adapting this delivery method for other neurological or sensory gene therapies [1].
The research was supported by various funding bodies, including the Lundbeck Foundation, the Novo Nordisk Foundation, the National Institute of Neurological Disorders and Stroke, and the European Union's Horizon 2020 Research and Innovation Programme.
The primary cause of the hearing loss targeted by this study is the death or loss of function of hair cells found in the cochlea. Hair cells do not naturally regenerate in humans and other mammals, but gene therapies have shown promise in repairing the function of hair cells in mice [1].
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. This discovery could potentially offer hope for a substantial clinical impact on hereditary deafness [1]. However, clinical translation will require further validation of safety, efficacy, and long-term outcomes in humans.
References:
[1] Nedergaard, M., et al. (2022). Delivery of gene therapy via cerebrospinal fluid transport to the adult inner ear. Science Translational Medicine. doi: 10.1126/scitranslmed.abb4478
This groundbreaking research offers a potential solution for those dealing with genetic hearing loss, as it proposes a novel strategy to deliver gene therapy through cerebrospinal fluid (CSF) transport to the adult inner ear [1]. Beyond hearing, this delivery method could also have implications for other medical-conditions, particularly those related to health-and-wellness and the sensory system.
