Figure 2.

HC loss increased the amount of S-phase entry in utricles from the youngest neonates but did not extend the age of responsiveness beyond P8. a, Utricles were cultured in control medium or that medium plus 2 mm neomycin for 24 h. Then, they were all cultured for 3 d in 7F medium with EdU. b, Quantification of HC density in utricles cultured under the two conditions (n = 8 for P0, n = 7 for P2 and P4, and n = 6 for P6, P8, P16, Adult for Control and 7F). c, Representative high-magnification images of P2 mouse utricles exposed to the 24 h pretreatment with 2 mm neomycin or control medium followed by 72 h in 7F medium and EdU. HCs were labeled with antibodies against myosin VIIA and spectrin. d, Low-magnification images show that experimental induction of HC loss potentiated S-phase entry in utricles from P0 and P2 mice cultured in 7F medium but had no such effect in utricles from mice older than 1 week. e, Quantification of EdU⁺/Sox2⁺ SCs in neomycin-treated and control utricles cultured 4 d (n = 8 for P0, n = 7 for P2 and P4, and n = 6 for P6, P8, P16, Adult for Control and 7F). The difference in P6 utricles was statistically significant, but with the EdU⁺/Sox2⁺ cells in control cultures exceeding the number of such cells in neomycin-treated cultures (control: 20 ± 8 vs neo: 5 ± 2, p = 0.01257, n = 6). Data are mean ± SD. ns, Not significant (p ≥ 0.05). *p < 0.05, **p < 0.01, ***p < 0.001. DIV, days in vitro.