It’s become an accepted fact of life that people tend to lose much of their hearing as they get old. This is because our hair cells, the cells in our ears which allow us to hear, cannot regenerate - we’re born with 30,000 per ear, but once they die off or get damaged, they’re gone for good. Stefan Heller, a professor of otolaryngology (ear, nose and throat stuff) at Stanford University, wants to change that. To that end, he recently succeeded in creating mouse hair cells in a petri dish. Could an end to deafness be far behind?
Heller and his team used embryonic stem cells from mice, along with mouse fibroblasts (cells found within fibrous connective tissue) reprogrammed to act like stem cells. After ten years of lab work, they were able to engineer these cells into something that looked and performed just like hair cells. “We knew it was really working when we saw them in the electron microscope,” Heller said. “They really looked like they were more or less taken out of the ear.”
The team mimicked the steps involved in the formation of a mouse’s ear in utero. They started by turning the cells into the type that form a mouse embryo’s ectoderm, or outer layer of cells. By manipulating growth factors, they then proceeded to transform them into ear cells. Finally, they altered the “chemical soup” in the petri dish, causing the cells to cluster like hair cells.
At this point the cells also developed stereocilia, which are tiny clumps of hair-like projections found on hair cells. Stereocilia bend when subjected to vibrations, converting those vibrations into electrochemical signals that the brain interprets as sound. The Stanford researchers used a probe to stimulate the synthesized stereocilia, and found that they did indeed produce an electrochemical current.
Heller is working towards producing human hair cells for transplantation, but says the engineered cells could also be used for testing possible deafness-curing medications. “We could now test thousands of drugs in a culture dish,” he explained. “It is impossible to achieve such a scale in animals. Within a decade or so we could reap the benefits of this type of screening.”
Heller’s research was recently published in the journal Cell.