Ephrin-B2 protein, a key factor in cell identity in the inner ear

The research of Jean Defourny and Brigitte Malgrange has resulted in a promising discovery. The results of this study have been published in the journal Nature Communications (1). “We identified a signaling pathway involving the Ephrin-B2 protein and its specific receptor EphA4. These play a very important role in the maintenance of the identity of the cells in the organ of Corti”, explains Brigitte Malgrange. The scientists used various methods and experiments with knockout mice whose coding gene for the protein Ephrin-B2 was invalidated by means of soluble inhibitors of the protein or interfering RNAs. “The Ephrin-B2 protein is only present in supporting cells, not in hair cells.  When we inhibit the expression of the coding gene for this protein or its function, the supporting cells transdifferentiate into hair cells”, explains the researcher. This very interesting discovery makes it possible to induce new hair cells directly at the right place within the inner ear. While the researchers from Liege would seem to be on the right path with regard to combatting sensorineural deafness linked to the loss of hair cells, other steps remain necessary before this can be achieved. “We must now verify that these newly generated hair cells connect correctly to the sensory nerves of the inner ear. This is the only way that sound can be transmitted to the brain”, explains Brigitte Malgrange. This research is currently under way at GIGA-Neurosciences.

A small step towards finding an alternative to hearing aids

Currently, there is no medical procedure to correct problems of sensorineural deafness. “The only possible solution are hearing aids, but only in the case where there is some residual hearing” explains Brigitte Malgrange. External hearing aids make it possible to amplify the sound that reaches the ear. Cochlear implants are used in case of profound deafness, when the patient’s inner ear is no longer capable of analyzing the sound that reaches him. Cochlear implants do this work in place of the cochlea and stimulate the residual neurones. 
The line of research involving the regeneration of hair cells that is currently being followed by Brigitte Malgrange’s team is both innovative and promising given the results that they have recently obtained. It only remains for science to succeed in finding a medical application for this discovery. 

(1) Jean Defourny, Susana Mateo Sánchez, Lies Schoonaert, Wim Robberecht, Alice Davy, Laurent Nguyen & Brigitte Malgrange. Cochlear supporting cell transdifferentiation and integration into hair cell layers by inhibition of ephrin-B2 signalling. Nature Communications, 2015-04-29 , DOI: 10.1038/ncomms8017