Regenerative cochlear implants

Sensorineural hearing loss (SNHL) is a degeneration of the sensory cells or primary auditory neurons (ANs) present in the inner part of the ear called the cochlea. CIs effectively restore hearing but their utility could be improved by blocking the progression of neural degeneration and restoring synaptic connections with sensory cells resulting in better speech discrimination especially in noisy environments.

The 'Neurotrophic cochlear implant for severe hearing loss' (NEUEAR) project is working on using encapsulated cell (EC) technology with or without the CI to deliver neurotrophic factors that prevent further AN degeneration. Testing on animal models of hearing loss should reveal the feasibility of such an approach and facilitate further development and commercialisation of promising results.

Researchers first focused on producing and characterising cell clones for the EC device. Genetically engineered cells derived from ARPE-19, a human retinal pigment epithelial cell line showed excellent neurotrophic factor expression and tolerance to electrical stimulation. In vitro studies revealed that brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) clones provided the best neuroprotection among the cell clones tested.

Based on in vitro test results, the best expressing cell lines were selected to test the secretion of neurotrophic factors in vivo from the EC device. NEUEAR successfully modified the design and developed CI and EC device prototypes for cochlear co-implantation in large animal studies.

Already, testing has been initiated in animals and CI design optimisation is ongoing. The team is also working on designing neurotrophic CI device prototypes for eventual use in human clinical trials.

Research outcomes have been widely disseminated to key stakeholders, including patients' associations and charities, the scientific community and the European Commission.

NEUEAR's innovative neurotrophic EC with CI prototype could improve the prognosis for millions of people suffering from SNHL. Besides arresting progressive degeneration of ANs, such a device would also enhance the hearing experience through a better device-neuron interface. Furthermore, the EC prototype alone could be adapted for other regenerative therapies.

Successful commercialisation of EC and CI prototypes will also increase the competitiveness of the industrial partners in this project in a multi-million euro global CI market.