Expression of the collagen-related heat shock protein HSP47 in fibroblasts treated with hyperthermia or photodynamic therapy.

Heat shock protein (HSP) 47 is associated with collagen type I metabolism, both constitutively and after stress-inflicted injury. It has been claimed that, in contrast to hyperthermia (HT), photodynamic therapy (PDT) does not damage collagen, as measured at the level of tissue. We have studied HSP47 expression in normal murine skin fibroblasts (3T6) treated with hyperthermia or photodynamic therapy (PDT) mediated by three different photosensitizers: (1) haematoporphyrin ester (HpE), (2) meta tetra hydroxyphenyl chlorin (mTHPC) and (3) riboflavin (RB). Riboflavin is not an established photosensitizer for PDT and was chosen here because it is known to provoke collagen damage. The applied doses of the treatments were isoeffective in terms of 3T6 clonogenic cell survival. Analysis, at both transcriptional and translational levels, revealed HSP47 elevation after hyperthermia and after PDT with RB. PDT sensitized by HpE and mTHPC did not significantly alter HSP47 expression. These observations are consistent with our hypothesis that this collagen chaperone is up-regulated by laser-mediated modalities known to damage collagen (i.e. HT and RB PDT) but not by more conventional PDT treatments. Additionally, unexpected significant up-regulation of HSP47 was detected after illumination alone (no photosensitizer) of 3T6 cells at 653 nm laser light, but not at 630 nm.