The dose-dependence biological effect of laser fluence on rabbit fibroblasts derived from urethral scar

Two-micrometer laser vaporization resection has been used in clinic for years, but some patients received the treatment are still faced with excessive and abnormal wound repair which leads to the recurrent of urethral stricture eventually. Fibroblasts play a key role in the processes of “narrow–expansion/operation–restenosis” recurring problems. Here, we investigated the effect of laser fluence biomodulation on urethral scar fibroblasts as well as the underlying mechanism. Urethral scar fibroblasts were isolated and cultured, and laser irradiation (2 μm) was applied at different laser fluence or doses (0, 0.125, 0.5, 2, 8, 32 J/cm²) with a single exposure in 1 day. The effect of 2-μm laser irradiation on cell proliferation, viability, and expression of scar formation related genes were investigated. Two-micrometer laser irradiation with intermediate dose (8 J/cm²) promoted scar fibroblasts proliferation and reactive oxygen species (ROS) production, while higher doses of 32 J/cm² are suppressive as it decreased the survival rate, viability, and proliferation of fibroblasts. In addition, qRT-PCR and Western blotting results both proven that collagen type I, collagen IV, MMP9, and CTGF display significant increase, yet the TGF-β1 expression was severely reduced at intermediate dose (8 J/cm²) group when compared with the others groups. Our findings suggest the scar formation-related genes are sensitive to intermediate laser irradiation dose, the most in scar fibroblasts. We revealed the bioeffect and molecular mechanism of 2-μm laser irradiation on rabbit urethral scar fibroblasts. Our study provides new insights into the mechanisms which involved in the excessive and abnormal wound repair of 2-μm laser vaporization resection. These results could potentially contribute to further study on biological effects and application of 2-μm laser irradiation in urethral stricture therapy.