Hearing loss due to old age impacts many people and often finds its cause in the depletion of those sensory receptors known as hair cells. At birth there are about 15,500, but they do not regenerate over time. Loud noises, infections, toxins, and the natural aging process damage them, which can lead to hearing loss.
However, researchers may now have found a way to regenerate them. In a study published in the European Journal of Neuroscience, a team coordinated by Patricia White of the University of Rochester in upstate New York has shown that it is possible to regrow hair cells in the cochlea of mice. This major breakthrough was made possible through the study of birds, whose bodies are capable of regrowing these cells, as is the case for other vertebrates, but not of mammals.
“From this point of view,” says Jingyuan Zhang, co-author of the study, “ mammals are an extravagant exception in the animal kingdom when it comes to cochlear regeneration.
As early as 2012, Patricia White found that hair cell generation is promoted by neighboring cells; in birds, it is a family of receptors called epidermal growth factor (EGF) that activates supporting cells. In mammals this signal is blocked, so the researchers looked for a way to turn it on temporarily.
They tried three different methods, all focused on a specific receptor called ERBB2, which is found in the supporting cells within the cochlea, and finally succeeded in reactivating it and achieving the desired effect. ERBB2 stimulated the supporting cells, and as they began to multiply, neighboring stem cells transformed into new sensory hair cells. In addition, hair cells naturally integrated with nerve cells. This is a crucial step without which regaining hearing would not be possible.
“The process of hearing repair ,” explains Patricia White. is a complex problem and requires a series of cellular events; regeneration of sensory hair cells is necessary and that these cells function properly, connecting with the network of neurons. This research could represent a new approach to cochlear regeneration and ultimately to hearing restoration.”
Zhang J, Wang Q, Abdul-Aziz D, Mattiacio J, Edge ASB, White PM. ERBB2 signaling drives supporting cell proliferation in vitro and apparent supernumerary hair cell formation in vivo in the neonatal mouse cochlea. Eur J Neurosci. 2018 Sep 30.
