Synergistic SHH activation and BMP inhibition remodel progenitor niche for enhanced hair cell generation

Hair cell regeneration from supporting cells declines rapidly during early postnatal development, limiting therapeutic applications. We demonstrate that strategic microenvironmental remodeling can dramatically enhance inner ear progenitor cell (IEPC) function beyond what conventional marker-based approaches predict. Using functional screening focused on differentiation capacity rather than single progenitor markers (Lgr5), we discovered that concurrent Sonic hedgehog activation and BMP inhibition create a synergistic niche environment. This dual signaling approach generated high-purity Sox2⁺/Ki67⁺ IEPCs from postnatal day 7 (P7) supporting cells with 50.83%±1.76% hair cell differentiation efficiency. Single-cell RNA sequencing revealed that this strategy drives progenitor reprogramming by activating inner ear developmental gene programs while suppressing supporting cell identity. Regenerated hair cells exhibited functional mechanotransduction, voltage-gated currents, and drug sensitivity profiles. Importantly, this microenvironmental control strategy remained effective up to the P9 stage, demonstrating that niche reconstruction can overcome developmental stage-specific limitations in progenitor function. These findings establish niche remodeling as a powerful framework for enhancing stem cell therapeutic potential.