The Preventive Role of Low-Level Laser Therapy in Cochlear Outer Hair Cell Damage Due to Noise Exposure in Guinea Pigs

By considering the necessity prevention of hearing loss secondary to noise exposure, this research investigated the protective role of low-level laser (LLL) therapy in the prevention of cochlear outer hair cell (OHC) damage and death due to noise exposure in guinea-pigs.

In this study, a total of 30 male albino guinea-pigs (290±10 g) were used and randomly divided into three groups in order to evaluate hair cell counts and apoptosis of cochlear hair cells, including noise, control, and LLL therapy group each containing 10 pigs. The right outer ear canal of the LLL therapy group was exposed to165 mW/cm2 LLL for five successive days for just half an hour per day. Then, the LLL therapy and noise groups were exposed to 3-6 kHz octave band noise at 120 dBSPL. Twenty-one days after noise exposure, the animals of all groups were killed for the count of their OHCs and immunohistochemistry for caspase-3 experiments.

The percentage of OHCs in the base and middle turns of the cochlea was significantly lower in the noise group compared to the control and low laser therapy groups (P<0.05). The expression of caspase-3 significantly differed in the noise group in comparison to control and low laser groups regarding the experiment of immunohistochemistry (P<0.05).

The findings indicated that LLL was useful in the protection of the cochlear OHCs and could help in the prevention of hair-cell apoptosis.