Laser-Induced Regulation of Pro-Inflammatory Mediators in Human Tendon and Bursa-Derived Cells In Vitro: A Preliminary Report

Background/Objectives: Photobiomodulation therapy (PBMT) has shown promising clinical results for a variety of musculoskeletal disorders, yet many of the cellular mechanisms underlying its anti-inflammatory effects remain incompletely understood in the context of tenocytes and bursa-derived cells. This study evaluated the effects of a 1064 nm laser on inflammatory gene expression with an in vitro model of IL-1β-induced inflammation. Methods: Human tenocytes and subacromial bursa-derived cells were isolated following rotator cuff repair and cultured under standard conditions. An inflammatory model was established by stimulating cells with IL-1β prior to PBMT treatment, to evaluate whether PBMT alters inflammatory gene expression. Cells then received PBMT at fluences of 1.5 and 4.5 J/cm2 using a 1064 nm laser once daily for three days. Relative markers of TNF-α, IL-6, MMP-1, MMP-3, PTGS2 (COX-2), and NF-κB were quantified using RT-qPCR. Statistical analysis was performed with Dunnett-adjusted comparisons. Results: PBMT showed no significant effects on gene expression compared with IL-1β-treated controls after correction for multiple comparisons. An isolated significant increase in IL-6 expression was observed in bursa-derived cells treated at 1.5 J/cm2 (p = 0.024), whereas no other significant differences were detected. Bursa-derived cells nevertheless showed greater variability and directional responsiveness. Conclusions: PBMT at 1.5 and 4.5 J/cm2 did not modulate inflammatory gene expression in this in vitro model. Further studies with larger sample sizes and additional time points are needed to determine the cellular effects of PBMT during inflammation.