Human inner ear tissues have been grown in laboratory, a scientific breakthrough that could lead to treatment for hearing impairment. The findings are published in the journal Nature Biotechnology.
A team of researchers from Indiana University (IU) have successfully grown inner ear tissues from human stem cells. The aim of this endeavour is to test new therapies—normally, human inner ear cells are not available for research purposes, and study author Eri Hashino from IU School of Medicine explains that the inner ear is among a little group of organs on which biopsy is not performed; that is, the tissues cannot be removed from a living body to be examined. Therefore, growing the inner ear from stem cells in laboratory promises to further research in the development of therapies for hearing and balance disorders as the dish-grown tissues can be used to model disease, and test new treatment methods.
The team has dubbed the end result as “inner ear organoids”. The latter are described as 3D structures that consist of inner ear sensory and nerve cells. Hashino and colleagues were able to culture human stem cells which were administered with the required signalling molecules directing them into the production of the human inner ear, by using a method they developed in former studies of theirs. They had previously worked on a technique called 3D culture whereby stem cells are incubated in a floating spherical aggregate, as opposed to conventional cell culture which has cells growing on a flat surface. The sophisticated 3D method allowed the scientists to make several inner ear organoids in a single cell aggregate that was the size of a pea.
Moreover, the new technique accommodates for more complex cellular interactions that are more representative of what really happens in the human body, explains lead author, Karl R. Koehler. He describes the technique they used as a recipe for concocting human inner ear tissues from stem cells; this “recipe” was, then, improved, leading to the final production of the organoids.
Also, the sensory cells within the organoids appear to have the same function as human inner ear cells that sense gravity and motion. The neurones were also found to resemble those that relay signals connecting the ear to the brain. The researchers also observed these nerve cells connecting with the sensory cells. Koehler explains that this interaction (between the two types of cells) is extremely important as it accounts for hearing and balance.
Hashino says their findings are a “real game changer” as this will allow researchers to shift from testing drugs and therapies on animal cells to doing the same on human cells.
“We hope to discover new drugs capable of helping regenerate the sound-sending hair cells in the inner ear of those who have severe hearing problems,” says Hashino.