Hypoxia-Stabilized HIF1α Restricts Hair Cell Reprogramming by Suppressing Wnt Signaling in the Mammalian Cochlea

Sensorineural hearing loss, caused by irreversible hair cell (HC) loss, remains incurable due to the inability of the mammalian cochlea to regenerate HCs spontaneously. Although the combinatorial modulation of Notch and Wnt signaling robustly reprograms cochlear supporting cells to HCs in vitro, these strategies show limited success in vivo, which suggests that the native cochlear microenvironment imposes inhibitory cues. Here, we identify hypoxia-inducible factor 1α (HIF1α) as a critical barrier to HC reprogramming in vivo. We found that HIF1α accumulates in the basilar membrane of the intact cochlea, whereas ex vivo culture rapidly eliminates this accumulation. Mimicking the in vivo hypoxic state recapitulated the reprogramming blockade, hindering supporting cells from completing the fate transition to HCs. Mechanistically, HIF1α selectively suppressed Wnt signaling, as evidenced by the reduced expression of Wnt target genes and Wnt10a. Importantly, the pharmacological inhibition of HIF1α rescued the impaired reprogramming under hypoxia. These findings demonstrate that HIF1α accumulation in the hypoxic cochlear environment antagonizes Wnt-mediated HC differentiation, providing a mechanistic explanation for the failure of in vivo regeneration. Targeting HIF1α to restore supporting cell reprogramming competence within the hypoxic cochlear niche represents a promising, clinically translatable strategy for functional HC regeneration and hearing restoration.