Effect of photobiomodulation on rat parotid gland cells after ionizing radiation - an experimental study in animal model - Part 1.

BACKGROUND

Radiotherapy for head and neck cancers often impairs salivary gland function. Photobiomodulation (PBM) has emerged as a potential intervention to mitigate radiation-induced tissue damage. This study aimed to evaluate the effects of PBM on the parotid glands of Wistar rats subjected to ionizing radiation.

METHODS

Forty-two male Wistar rats (7-8 weeks old) were randomly assigned to seven groups (n = 6). G1: control; G2: radiotherapy only (20 Gy); G3: PBM only; G4-G7: PBM combined with radiotherapy. PBM was applied using the Laser Duo (MMOptics®) with 660 nm and/or 808 nm wavelengths, varying in dose and number of application points. The histological analysis focused on preserving the acinar area. Receiver operating characteristic (ROC) curve analysis was used to determine the threshold for preserved acinar architecture.

RESULTS

The group receiving combined PBM (660 nm + 808 nm, 54 J per gland; G5) demonstrated the highest preservation of acinar morphology, closely resembling the control. Groups receiving isolated red or infrared wavelengths (G4, G6) showed moderate protection. The lowest dose group (G7, 1.8 J) was ineffective.

CONCLUSION

PBM significantly reduced RT-induced damage to the parotid glands in a dose-dependent manner. The red laser protocol at 27 J per gland showed the highest level of tissue preservation. These findings support the potential of PBM as a protective adjunct during radiation therapy (RT) and justify further studies to standardize optimal clinical parameters.