Can we reverse hearing loss by regrowing cochlear hair cells? Quite possibly!

Good news! 

I guess, I was lucky and smart enough not loose my hearing due to loud noise in the past. With ageing my hearing sense is in a much better shape than my eyesight and sense of smell.

"... The most common cause of hearing loss is progressive because these hair cells—the primary cells to detect sound waves—cannot regenerate if damaged or lost. ...
On the other hand, birds and fish can regenerate these hair cells, and now researchers ... are getting closer to identifying the mechanisms that may promote this type of regeneration in mammals ...
Using single-cell RNA sequencing in mice, researchers compared cells with an overactive growth gene (ERBB2 signaling) with similar cells that lacked such signaling. They found the growth gene—ERBB2—promoted stem cell-like development by initiating the expression of multiple proteins—including SPP1, a protein that signals through the CD44 receptor. The CD44 receptor is known to be present in cochlear-supporting cells. This increase in cellular response promoted mitosis in the supporting cells, a key event for regeneration. ..."

From the abstract:

"Hearing loss caused by the death of cochlear hair cells (HCs) might be restored through regeneration from supporting cells (SCs) via dedifferentiation and proliferation, as observed in birds. In a previous report, ERBB2 activation in a subset of cochlear SCs promoted widespread down-regulation of SOX2 in neighboring cells, proliferation, and the differentiation of HC-like cells. Here we analyze single cell transcriptomes from neonatal mouse cochlear SCs with activated ERBB2, with the goal of identifying potential secreted effectors. ERBB2 induction in vivo generated a new population of cells with de novo expression of a gene network. Called small integrin-binding ligand n-linked glycoproteins (SIBLINGs), these ligands and their regulators can alter NOTCH signaling and promote cell survival, proliferation, and differentiation in other systems. We validated mRNA expression of network members, and then extended our analysis to older stages. ERBB2 signaling in young adult SCs also promoted protein expression of gene network members. Furthermore, we found proliferating cochlear cell aggregates in the organ of Corti. Our results suggest that ectopic activation of ERBB2 signaling in cochlear SCs can alter the microenvironment, promoting proliferation and cell rearrangements. Together these results suggest a novel mechanism for inducing stem cell-like activity in the adult mammalian cochlea."

Can we reverse hearing loss? Yes we can, here is how it works We are closer than ever to reversing hearing loss in humans, here is all the proof you need.

Can hearing loss be reversed? Research reveals clues that could regrow the cells that help us hear

Single cell RNA sequencing analysis of mouse cochlear supporting cell transcriptomes with activated ERBB2 receptor indicates a cell-specific response that promotes CD44 activation (open access)