Co-regulation of the Notch and Wnt signaling pathways promotes supporting cell proliferation and hair cell regeneration in mouse utricles

This work sought to determine the crosstalk between the Notch and Wnt signaling pathways in regulating supporting cell (SC) proliferation and hair cell (HC) regeneration in mouse utricles. We cultured postnatal day (P)3 and P60 mouse utricles, damaged the HCs with gentamicin, and treated the utricles with the γ-secretase inhibitor DAPT to inhibit the Notch pathway and with the Wnt agonist QS11 to active the Wnt pathway. We also used Sox2-CreER, Notch1-flox (exon 1), and Catnb-flox (exon 3) transgenic mice to knock out the Notch pathway and activate the Wnt pathway in Sox2+ SCs. Notch inhibition alone increased SC proliferation and HC number in both undamaged and damaged utricles. Wnt activation alone promoted SC proliferation, but the HC number was not significantly increased. Here we demonstrated the cumulative effects of Notch inhibition and Wnt activation in regulating SC proliferation and HC regeneration. Simultaneously inhibiting Notch and overexpressing Wnt led to significantly greater SC proliferation and greater numbers of HCs than manipulating either pathway alone. Similar results were observed in the transgenic mice. This study suggests that the combination of Notch inhibition and Wnt activation can significantly promote SC proliferation and increase the number of regenerated HCs in mouse utricle.