Endothelial Cell Responses to Photobiomodulation Treatments in Diabetic Wounds Are Mediated via Concerted PDGF, VEGF and TGF-β Signalling.

Diabetic ulcers resulting from neural and vascular perturbations represent a large proportion of non-traumatic lower limb amputations. Conventional treatments have limited efficacy. The non-invasive use of low-dose light treatments, termed photobiomodulation (PBM), has shown therapeutic benefits in diabetic patients. This study aimed to explore the response of endothelial cells to PBM treatment under hyperglycemic conditions in vitro. The major goal was to gain mechanistic insights into the biological effects of low-dose light, with the aim of optimising clinical treatment strategies. Therefore, human umbilical vein endothelial cells were exposed to hyperglycemic conditions (150-300 mM glucose) and incubated at 37°C with 5% CO2 for 24 h. The cells were then treated with low-dose light (660 nm, CW, 10 mW/cm2, 200 s and 0.84 Einstein). Cell responses were assessed through key signalling pathways, evaluating proliferation using the AlamarBlue assay, migration through the wound scratch assay and angiogenesis via the tubulogenesis assay, with assessments after 24 or 48 h. Data were analysed using one-way ANOVA followed by Tukey's post-test. Data showed that PBM treatments performed under controlled thermal conditions significantly improved endothelial cell proliferation, migration and tubulogenesis under hyperglycemic conditions. Crosstalk among platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and transforming growth factor beta (TGF-β1) signalling modulated these critical responses involving matrix metalloproteinases (MMP-2 and 9) activity. These findings showed that PBM treatments exert positive endothelial cell responses under hyperglycemic conditions that could contribute to improved diabetic wound healing. These observations provide mechanistic insights into enabling PBM as a novel and adjacent therapy for diabetic wound management.