Efficacy of Low-Level Laser Therapy in a Rabbit Model of Rhinosinusitis

Abstract

Little is known about alternative treatment options for rhinosinusitis (RS). We aimed to evaluate the efficacy of low-level laser therapy (LLLT) for RS in experimentally induced rabbit models of RS. A total of 18 rabbits were divided into four groups: a negative control group (n = 3), an RS group without treatment (n = 5, positive control group), an RS group with natural recovery (n = 5, natural recovery group), and an RS group with laser irradiation (n = 5, laser-treated group). Computed tomography and histopathological staining were performed for each group. mRNA and protein expression levels of local cytokines (IFN-γ, IL-17, and IL-5) were also measured. Tissue inflammation revealed a significant improvement in the laser-treated group compared with the RS and natural recovery groups (p < 0.01). In addition, sinus opacification in the CT scans and cytokine expression was reduced in the laser-treated group, though without statistical significance. LLLT could be an effective option for the management of RS concerning radiological, histological, and molecular parameters.

Keywords: cytokines; experimental model; inflammation; low-level laser therapy; sinusitis.

Figure 1

Representative images of and quantitative data for empyema volumes, estimated using computed tomography. (A) The negative control group showed no empyema in the maxillary sinus, whereas the positive control group showed total soft tissue density in the left maxillary sinus. (B) In the laser-treated group, empyema volumes were decreased compared with those in the natural recovery group. Data are expressed as the means ± SEMs. The results were statistically analyzed by Student’s t-tests.

Figure 2

Representative histopathological images of the sino-nasal mucosa according to groups (A). Quantitative data of histopathology in the sino-nasal mucosa among all groups (B). Data are expressed as the means ± SEMs. * p < 0.05, ** p < 0.01, *** p < 0.001. Scale bars = 80 μm. Upper and lower means head to oral cavity direction. (Upper indicated head direction whereas lower indicated oral cavity direction) Arrows and dot colors indicate eosinophils in Congo red stains, Mast cells in Toluidine blue stains and goblet cells in PAS stains.

Figure 3

Local cytokine levels as determined by real-time PCR and Western blotting. (A) Sino-nasal mucosa RNAs were isolated and the levels of IFN-γ, IL-17, and IL-5 were measured by RT-qPCR. (B) Sino-nasal mucosa proteins were isolated and the levels of IFN-γ, IL-17, and IL-5 were measured by Western blotting. Graphs indicate relative protein expression levels normalized to β-actin using the densitometric analysis with Western blotting bands presented in Supplementary Figure S1. Data are expressed as the means ± SEMs.

Figure 4

Experimental protocol. After 1 week of acclimatization, rabbits were divided into 4 groups: negative control group (n = 3), positive control group (n = 5), natural recovery group (n = 5), and laser-treated group (n = 5). Rabbits that were not subjected to experimental treatment (natural recovery group) and rabbits subjected to laser irradiation for one week (laser-treated group) were sacrificed on day 21.

Figure 5

Induction of rhinosinusitis in a rhinogenic rabbit model. (A) After anesthetization, a 3 cm sized bone window was created in the anterior wall of the maxilla. (B) A piece of surgical sponge, Merocel (Medtronic-Xomed, Jacksonville, FL, USA), was inserted into the sino-nasal cavity to block the natural ostium of the sinuses. (C) The surgical window was closed using surgical thread. RS induction by inserting Merocel was performed for 2 weeks in the positive control, natural recovery, and laser-treated groups.

Figure 6

Laser irradiation of rabbits. (A) A low-level laser device was used at the following wavelengths and powers: AlGaInP 670 nm, 3 mW and GaAs 830 nm, 20 mW. (B) Low-level laser therapy was applied to five rabbits (G4) through the nostrils for 20 min for 7 days.