Effect of low-level laser treatment on cochlea hair-cell recovery after ototoxic hearing loss

Abstract

The primary cause of hearing loss includes damage to cochlear hair cells. Low-level laser therapy (LLLT) has become a popular treatment for damaged nervous systems. Based on the idea that cochlea hair cells and neural cells are from same developmental origin, the effect of LLLT on hearing loss in animal models is evaluated. Hearing loss animal models were established, and the animals were irradiated by 830-nm diode laser once a day for 10 days. Power density of the laser treatment was 900 mW/cm(2), and the fluence was 162 to 194 J. The tympanic membrane was evaluated after LLLT. Thresholds of auditory brainstem responses were evaluated before treatment, after gentamicin, and after 10 days of LLLT. Quantitative scanning electron microscopic (SEM) observations were done by counting remaining hair cells. Tympanic membranes were intact at the end of the experiment. No adverse tissue reaction was found. On SEM images, LLLT significantly increased the number of hair cells in middle and basal turns. Hearing was significantly improved by laser irradiation. After LLLT treatment, both the hearing threshold and hair-cell count significantly improved.

A preliminary study on the efficacy and safety of low level light therapy in the management of cochlear tinnitus: A single blind randomized clinical trial

“…This preliminary study evaluated the efficacy and safety of LLLT with new irradiation parameters (diode laser with an 830 nm wavelength and an output level of 100 mw) for the treatment of chronic cochlear tinnitus. According to an animal study, only 5-6% of the output energy can reach the cochlea when an 830 nm wavelength is used 17 . One way to deliver more laser energy to the cochlea is to increase the output power of the laser.…”

Pre‐conditioning with near infrared photobiomodulation reduces inflammatory cytokines and markers of oxidative stress in cochlear hair cells

“…Determination of whether NIR prevents gentamicin from inhibiting these enzymes or, on the contrary, results in a limitation of ROS production rate will require further investigation. Previous studies showed that PBM increase survival of cochlear hair cell numbers and mediates their recovery after acoustic or gentamicin-induced trauma in rats in vivo [66,67]. However, recovery is only partial and mainly benefits cells in the middle turn of the cochlea [67], yet the mechanism driving oxidative stress and modulating inflammatory pathways remain unclear.…”

Treatment of peripheral vestibular dysfunction using photobiomodulation

“…10,22 Several studies from the authors have shown that photobiomodulation can have both preventative and regenerative effects. 12,13 However, these studies were performed in ex vivo organ culture systems using the utricle, and they lack functional outcomes. 23,24 In this study, rats were used as a model animal, and function and morphology were examined using the SHA test and cupula histology, respectively.…”

“…The inner ear comprises the cochlea (hearing organ) and the vestibular organ (balancing organ), which are located adjacent to one another and form a fluid-filled cavity with a bony wall. Several recent studies have shown promising effects from photobiomodulation of the cochlea; [8][9][10][11][12][13] however, the effect of photobiomodulation on the vestibular organ is not well understood.…”

“…The irradiation was performed as previously described. [8][9][10][11][12] Only the left ear was irradiated in groups H and L, and groups G and C did not receive photobiomodulation (PBM). PBM parameters were determined considering the penetration rate and the safety of the peripheral sensory organ.…”