Photobiomodulation at 660 nm stimulates proliferation and migration of diabetic wounded cells via the expression of epidermal growth factor and the JAK/STAT pathway

Photobiomodulation (PBM) modulates cellular processes to enhance diabetic wound healing. The photon energy activates wounded cells to proliferate and migrate. However, the signalling pathways responsible for these observations remain unknown. This study aimed to determine if PBM stimulates cellular proliferation and migration via the expression of epidermal growth factor (EGF) and activation of the Janus kinase/Signal transducer and activators of transcription (JAK/STAT) signalling pathway. Normal, wounded, diabetic and diabetic wounded cell models were exposed to PBM at a wavelength of 660 nm and fluence of 5 J/cm² and incubated for 48 h. Non-irradiated cells (0 J/cm²) and cells exposed to exogenous EGF (rh EGF) served as controls. Cellular migration was determined microscopically at 0, 24 and 48 h. Flow cytometry (BrdU) was used to determine cell proliferation, while the Trypan blue exclusion assay and adenosine triphosphate (ATP) luminescence was used to determine cell viability. The enzyme linked immunosorbent assay (ELISA) was used to analyse EGF expressed in the culture media, and phosphorylated (p-) EGF receptor (p-EGFR), p-JAK2, p-STAT1 and p-STAT5 in cells. Irradiated diabetic wounded cells showed a significant increase in EGF, and activation of its receptor (p-EGFR) and JAK/STAT (p-JAK2, p-STAT1 and p-STAT5). PBM at 660 nm and 5 J/cm² is able to modulate cellular autocrine signalling, particularly the EGF/EGFR loop leading to activation of the JAK/STAT pathway which in turn stimulates cell proliferation and migration.