Abstract
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.
Highlights
Hair cells (HCs) of the inner ear sensory epithelium are highly differentiated
The number of HCs in the utricles had clearly increased. (F-1) The high magnifications of image F show EdU+/Myo7a+cells in the utricles. (I) In the cultured utricles co-treated with DAPT and QS11 and supplied with 10 μM EdU for 14 days, the number of EdU+/Myo7a+cells was significantly increased compared with the utricles co-treated for 3 days. (J) The histograms show the differences in the number of HCs between the utricles co-treated with DAPT +QS11 for 3 days or 14 days
The role of interaction between Notch and Wnt signaling in regulating supporting cell (SC) proliferation and HC regeneration remains unknown in the mouse utricle
Summary
Hair cells (HCs) of the inner ear sensory epithelium are highly differentiated. The mammalian utricle, which is a vestibular organ that requires HCs to detect linear acceleration, has limited capacity for spontaneous HC regeneration. The utricle has the capacity to fully regenerate lost HCs after damage to the sensory epithelium[2,3]. (J) The histograms show differences in the number of SCs between the utricles co-treated with DAPT+QS11 for 3 days and 14 days. (I) In the cultured utricles co-treated with DAPT and QS11 and supplied with 10 μM EdU for 14 days, the number of EdU+/Myo7a+cells was significantly increased compared with the utricles co-treated for 3 days. (J) The histograms show the differences in the number of HCs between the utricles co-treated with DAPT +QS11 for 3 days or 14 days. The cells were counted per 100 μm × 100 μm in the striolar or extrastriolar region of the utricles (*p < 0.05, **p < 0.01, ***p < 0.001)
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