Pulsed Electromagnetic Fields Modulate Inflammatory and Tenogenic Responses in Human Tenocytes: Insights from Acute and Prolonged Inflammation Models.

Tendinopathy is a prevalent musculoskeletal condition characterised by chronic inflammatory and degenerative changes. Pulsed electromagnetic fields (PEMFs) represent a promising biophysical therapeutic modality, yet their effects across different inflammatory states of tendinopathy remain poorly characterised. To evaluate PEMF biological effects on human tenocytes, three in vitro models differing in IL-1β dose and duration were tested: acute low-dose (0.1 ng/mL, 96 h), acute high-dose (1 ng/mL, 96 h), and prolonged (0.1 ng/mL, 9 days). At the transcriptional level, PEMFs significantly reduced IL-6 and IL-8 mRNA overexpression in the acute low-dose model and CCL2 upregulation in the prolonged model. At the secretome level, PEMFs reduced GM-CSF and IL-8 secretion in the acute high-dose model, and suppressed CCL2 and CCL5 protein secretion in the prolonged model. MMP activity was not modulated by PEMFs in any condition. PEMFs consistently increased tenocyte proliferation across both the acute models. Finally, in wound healing assays, non-inflamed tenocytes exposed to PEMFs showed significantly enhanced wound closure compared to IL-1β-treated cells across all models; in the acute low-dose model, PEMFs also significantly improved wound closure in IL-1β-treated cells at an early timepoint, whereas no such effect was observed in cells exposed to high-dose or prolonged inflammation. PEMFs exert context-dependent effects, promoting healing primarily during acute or mild inflammation. These findings suggest that the inflammatory stage of tenocytes may influence PEMF responsiveness in vitro, highlighting the importance of considering this variable in the design of future clinical studies evaluating PEMF therapy for tendinopathy.