Cochlear Organoids to Identify Drugs to Regenerate Hair Cells

High-throughput screening on cochlear organoids identifies VEGFR-MEK-TGFB1 signaling promoting hair cell reprogramming

Highlights

• Cochlear organoids can be derived from both LGR5+ and LGR5– supporting cells
• HTS using cochlear organoids identifies regorafenib for hair cell differentiation
• Regorafenib promotes hair cell reprogramming and maturation in cochlear explants
• Regorafenib acts via a NOTCH-independent and VEGFR-MEK-TGFB1-dependent mechanism

Summary
Hair cell degeneration is a major cause of sensorineural hearing loss. Hair cells in mammalian cochlea do not spontaneously regenerate, posing a great challenge for restoration of hearing. Here, we establish a robust, high-throughput cochlear organoid platform that facilitates 3D expansion of cochlear progenitor cells and differentiation of hair cells in a temporally regulated manner. High-throughput screening of the FDA-approved drug library identified regorafenib, a VEGFR inhibitor, as a potent small molecule for hair cell differentiation. Regorafenib also promotes reprogramming and maturation of hair cells in both normal and neomycin-damaged cochlear explants. Mechanistically, inhibition of VEGFR suppresses TGFB1 expression via the MEK pathway and TGFB1 downregulation directly mediates the effect of regorafenib on hair cell reprogramming. Our study not only demonstrates the power of a cochlear organoid platform in high-throughput analyses of hair cell physiology but also highlights VEGFR-MEK-TGFB1 signaling crosstalk as a potential target for hair cell regeneration and hearing restoration.