Background/Objectives: Photobiomodulation Therapy (PBMT) is widely used in musculoskeletal rehabilitation. Although its clinical use continues to expand, the dose-dependent metabolic responses on specific musculoskeletal cell populations remain undefined. This study assessed the effects of 1064 nm PBMT on primary human tenocytes and bursa-derived cells across varying fluence and irradiance. Methods: Primary tenocytes and bursa-derived cells were cultured in 24-well plates and exposed to Hiro TT 1064 nm laser at fluences ranging from 1.5 to 6.0 J/cm2 and irradiance levels of 90 or 125 mW/cm2. Treatments were administered once daily for three consecutive days. Cellular activity was assessed using an XTT assay and bright field microscopy was performed to assess cell morphology and confluency. Statistical analysis was compared to evaluate dose-dependent effects. Results: PBMT demonstrated tissue-dependent effects on cellular metabolic activity and proliferation. In tenocytes, moderate fluence (4.5–6.0 J/cm2) significantly increased metabolic activity compared with control. In contrast, bursa-derived cells exhibited smaller magnitude changes, with most treatment groups demonstrating neutral or modest deviations from control. Conclusions: PBMT of 1064 nm wavelenght produced distinct dose-dependent responses in musculoskeletal cell types, with tenocytes demonstrating a threshold-dependent response and bursa-derived cells showing attenuated effects. These findings support the need for tissue-specific parameters when applying PBMT in clinical tendon-related applications.
Sigman et al. (Fri,) studied this question.