Collagen secretion after photodynamic therapy versus scar-inducing anti-cancer modalities: An in vitro study

Photodynamic therapy (PDT) has been associated anecdotally with good quality healing and an absence of scar formation. Our previous studies, examining the levels of the collagen specific molecular chaperone Hsp47, have noted differences in the response after photodynamic therapy and hyperthermia at both the transcriptional and translational levels. In the present study the levels of Hsp47 after exposure to two chemotherapeutic agents (bleomycin and mitomycin), ionising radiation, hyperthermia and haematoporphyrin ester (HpE) mediated PDT were compared in both mouse and human fibroblast cell lines. A rapid assay for soluble collagen has also been used to quantify soluble collagen levels at early time points after treatment. Peak Hsp47 levels were found to correlate well with peak collagen levels. The results show that the levels of collagen measured in vitro are elevated in modalities associated with scarring in vivo but not after HpE-PDT.