Effect of low level laser therapy on hair cell regeneration following gentamicin induced ototoxicity in postnatal organotypic culture of rat cochlea

Abstract

Aim: To investigate effects of low level laser therapy (LLLT) on hair cell regeneration following gentamicin ototoxicity in organotypic culture of rat cochlea. Methods: Organotypic cultures of cochlea in culture medium were allowed to grow for 17 days (C group). The organotypic cultures were irradiated daily with 808 nm LD laser, at 28.8 J/ cm²(L group). The organotypic culture were exposed to 1 mM of gentamicin for 48 hr and allowed to recover (G group) or allowed to recover in the culture medium with daily LLLT at 28.8 J/ cm² (GL group) for 17 days. The cochleae were stained with FM1-43. The number of hair cells was counted in each group serially for 17 days. Results: While the C group kept on losing hair cells in vitro culture, the hair cells remained rather stationary in the L group. The number of hair cells revealed significantly larger number of hair cells in the L group compared to the C group (p=0.05). And the group × time interaction was also significant (p=0.04). That is, the number of hair cells in the C group showed decreasing tendency which was significantly different from the L group. In G group, the initial number of hair cells decreased to 37.2% of that of the gentamicin non-exposed groups. While the G group kept on losing hair cells, the number of hair cells increased in the GL group. The number of hair cells revealed significantly larger in the GL group (p=0.01) compared to G group. And the group × time interaction was also significant (p=0.01). Also, the number of hair cells in the GL group showed increasing tendency which was significantly different from the G group. Conclusion: These results suggest that LLLT promotes hair cell regeneration following gentamicin damage in cochlear explants.