Effect of low-level laser therapy on cochlear hair cell recovery after gentamicin-induced ototoxicity

Abstract

Cochlear hair cells are the sensory receptors of the auditory system. It is well established that antibiotic drugs such as gentamicin can damage hair cells and cause hearing loss. Rescuing hair cells after ototoxic injury is an important issue in hearing recovery. Although many studies have indicated a positive effect of low-level laser therapy (LLLT) on neural cell survival, there has been no study on the effects of LLLT on cochlear hair cells. Therefore, the aim of this study was to elucidate the effects of LLLT on hair cell survival following gentamicin exposure in organotypic cultures of the cochlea of rats. The cochlea cultures were then divided into a control group (n = 8), a laser-only group (n = 8), a gentamicin-only group (n = 8) and a gentamicin plus laser group (n = 7). The control cultures were allowed to grow continuously for 11 days. The laser-only cultures were irradiated with a laser with a wavelength of 810 nm at 8 mW/cm(2) for 60 min per day (0.48 J/cm(2)) for 6 days. The gentamicin groups were exposed to 1 mM gentamicin for 48 h and allowed to recover (gentamicin-only group) or allowed to recover with daily irradiation (gentamicin plus laser group). The hair cells in all groups were stained with FM1-43 and counted every 3 days. The number of hair cells was significantly larger in the gentamicin plus laser group than in the gentamicin-only group. The number of hair cells was larger in the laser-only group than in the control group, but the difference did not reach statistical significance. These results suggest that LLLT may promote hair cell survival following gentamicin damage in the cochlea. This is the first study in the literature that has demonstrated the beneficial effect of LLLT on the recovery of cochlear hair cells.

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.…”

“…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. Our investigation introduces a better understanding of the mechanistic feature of NIR applied to cochlear hair cells and show that NIR reduces ROS, and suppresses proinflammatory mediators.…”

Transmeatal Low Level Laser Therapy (LLLT) on Vestibular Inner Ear after Topical Gentamicin Ototoxicity

“…Since LLLT was effective in vitro study, it was expected to be effective in vivo study as shown in this study.LLLT has been shown to be effective in the treatment of gentamicininduced ototoxicity. 5 The presently demonstrated positive results on vestibular ototoxicity may provide further clinical application of LLLT. Further studies are required to demonstrate the efficacy of delayed treatments on chronic vestibulopathy and for detailed understandings of its mechanisms.…”

“…4 LLLT has been effective to prevent and recover cochlear hair cells after gentamicin ototoxicity in vitro study. 5 LLLT has been effective to recue noise induced hearing loss in rats. 6 However, no study in the literature has investigated the effect of LLLT on the recovery of vestibular dysfunction and damaged vestibular hair cells after ototoxicity.…”

In vitro evaluation of low-intensity light radiation on murine melanoma (B16F10) cells

“…It was shown that therapeutic effects of low-level light radiation are dependent on the selected frequency and intensity of external exposures as well as absorption of such irradiation by molecules and cells [7,28,32]. Typical irradiation intensity range used in LILT is between 10 and 5000 mW/cm2 [9,17].…”