Abstract:

Objective To investigate the effect of δ-aminolevulinic acid （ALA）-induced photodynamic reaction on biological characteristics of skin fibroblasts. Methods Human skin fibroblasts were isolated from the foreskin of children and cultured in the presence of 0.5 to 5.0 mmol/L ALA; three hours later, they were irradiated with 632.8 nm laser followed by additional 12-hour culture. Then, MTT assay and flow cytometry were used to measure the proliferation and apoptosis of cells. The levels of matrix metalloproteinase （MMP）-1, -2 and -3 and hydroxyproline in the culture supernatant of irradiated cells were determined by avidin-biotin complex-based ELISA and alkaline hydrolysis-based method, respectively. Results With the rise of ALA concentration from 0.5 to 5.0 mmol/L, the proliferation level of fibroblasts expressed as the absor-bance at 570 nm dropped from 0.45 ± 0.05 to 0.32 ± 0.04, and cell death rate increased from 6.4% ± 2.0% to 29.6% ± 2.2%. Meanwhile, the contents of MMP-1, -2 and -3 increased at the early stage, but decreased at the late stage, whereas the hydroxyproline level showed an inverse tendency during the increase of ALA concentration from 0.5 to 5.0 mmol/L. Conclusions Proper intensity of photodynamic reaction induced by ALA could enhance the secretion of MMP and inhibit the synthesis of collagen by skin fibroblasts, however, high concentration of ALA may exert an inverse effect.