660 nm photobiomodulation attenuates inflammatory-catabolic transcriptional programs in an osteoarthritis-like...

Photobiomodulation (PBM) has shown potential for modulating osteoarthritis (OA)-related inflammation and cartilage degeneration, yet the irradiation conditions used across studies vary widely and are often assessed with selected marker-based endpoints. The transcriptomic responses associated withselected PBM condition PBM conditions in OA-like cells remain insufficiently defined. Here, we applied a controlled-variable screening design to identify an effective 660 nm PBM condition in IL-1β-induced OA-like SW1353 cells and further characterized the associated transcriptomic response. PBM was evaluated under different irradiances and energy densities using cell viability and IL6/MMP13 expression as representative inflammatory-catabolic readouts. Within the tested range, PBM generally reduced IL-1β-induced IL6 and MMP13 expression, and the inhibitory effect followed a biphasic-like, window-dependent pattern. Among the tested parameters, 5 mW/cm² (18 J/cm² total dose) produced the most consistent inhibitory effect. RNA sequencing (RNA-seq) under this selected condition revealed coordinated transcriptomic remodeling after PBM treatment. PBM suppressed major inflammatory-catabolic programs, including TNF, nuclear factor kappa B (NF-κB), IL-17, JAK-STAT, and cytokine-related signaling, while partially reversing IL-1β-associated alterations in cellular organization and metabolic pathways. PBM-reversed gene analysis identified 157 genes showing opposite expression trends between OA and PBM conditions. Protein-protein interaction (PPI) and IL6/MMP13-centered co-expression analyses indicated that PBM-responsive genes converged on cytokine/chemokine signaling, NF-κB-associated regulation, and extracellular matrix degradation modules. RT-qPCR validation confirmed the downregulation of representative nodes from these modules, including IRAK2, NFKBIA, TNFAIP3, IL6, CXCL8, CCL2, MMP13, and MMP3. These findings provide a transcriptomic framework for understanding PBM-associated regulation of inflammatory-catabolic responses in OA-like SW1353 cells.