Northwestern Medicine scientists discovered that a specific cell type in the inner ear directs the arrangement of the organ responsible for hearing, as reported in Science Advances.
The investigation used mice to study the organ of Corti, a highly ordered part of the cochlea that transforms sound vibrations into electrical impulses. The organ contains two sensory hair‑cell types and six supporting‑cell types arranged precisely in 11 rows.
**Inner hair cells** serve as developmental architects, guiding the formation and placement of surrounding supporting cells.
"This work goes beyond hearing and deafness research," said Jaime García‑Añoveros, Ph.D., professor and senior author. He noted that genetic manipulation allows conversion of one cell type into another and observation of its influence during different developmental stages.
Researchers genetically reshaped hair cells at various ages and generated mice lacking inner hair cells to observe their effect.
They found that inner hair cells stimulate the creation of outer pillar cells while inhibiting Deiters’ cells, ensuring distinct rows for each cell type. Inner hair cells are also crucial for early development of inner phalangeal cells, attracting them for enveloping during and after development.
These experiments demonstrate that inner hair cells actively direct the fate and arrangement of neighboring support cells rather than being passive.
"By swapping identities between sensory cells, we clarified the non‑cell‑autonomous roles they play in assembling the organ," García‑Añoveros explained. The study focuses on cells, not just genes, to reveal how complex multicellular structures form.
This insight uncovers the developmental choreography that builds the organ of Corti’s intricate layout and emphasizes the communication between cells during organ formation. Inner hair cells function as a conductor in the hearing symphony.
As damage to hair and support cells underlies hearing loss, understanding their developmental interplay could guide strategies to rebuild the inner ear and restore hearing.
"Inner hair cells are very directive, signaling the arrangement of other cells," García‑Añoveros said. "For hearing regeneration, one needs not only a hair cell but also its specialized supporting partners, which are essential."
The García‑Añoveros laboratory will continue exploring cell interactions in hearing. "We aim to piece the puzzle together," he said. "By converting an outer supporting cell into an inner one or another outer type, we can uncover each cell’s role—whether it follows instructions or gives them—and understand this command chain."