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Summary

Background

Hypertrophic scarring (HS) is a chronic skin condition, and inhibition of normal fibroblast ageing plays an important role in its pathogenesis. Photodynamic therapy (PDT) is known to inhibit synthesis of collagen proliferation in blood vessels and fibroblasts in scar tissue, with no significant adverse reactions reported.

Aim

To investigate the effect of PDT in the rabbit ear model of HS, and the specific mechanism of action of PDT.

Methods

We assessed the clinical and histopathological appearance of rabbit ears with HS with and without PDT. In addition, mRNA levels of matrix metalloproteinase (MMP)-2, MMP-3, MMP-9 and tissue inhibitor of metalloproteinase (TIMP)-1, and concentration of β-galactose were all measured to confirm cell senescence.

Results

Our data indicate that PDT can accelerate fibroblast ageing by increasing the ratio of MMPs to TIMP, in addition to promoting degradation of collagen and extracellular matrix, thereby inhibiting HS formation. These effects lasted for up to 60 days, and induced no significant adverse local or systemic reactions. The efficacy of the treatment can be maximized by applying an appropriately high concentration of aminolaevulinic acid.

Conclusions

PDT can induce senescence in fibroblasts, and may constitute a useful treatment for pathological scarring.