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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.
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