Investigation on the Molecular Mechanism of Photorejuvenation in Photodynamic Therapy
BACKGROUND: The photoaging of the skin is characterized by wrinkles, mottled pigmentation, telangiectasia and malignancies due to the effects of long-term UV exposure. Photodynamic therapy (PDT) is a therapeutic modality for cutaneous malignant and premalignant condition. Recently, several clinical studies reported that the PDT has photorejuvenation effects on the aged skin. In the previous report, which is examined direct effect of PDT on fibroblast (FB), PDT induced increase of matrix metalloproteinase (MMP)-3 and collagen type Iα through prolonged activation of extracellular signal–regulated kinase (ERK). Increased MMP-3 may induce breakage of old collagen and allow new collagen synthesis. PURPOSE: In this study, I investigated molecular mechanism of photorejuvenation after PDT focused on interaction between keratinocyte (KC), FB, and melanocyte (MC). METHODS: The “low level PDT” condition was used for PDT therapy to the KC, FB, and MC. FBs were stimulated with the KC-conditioned medium taken after PDT and MCs were stimulated with the KC-conditioned medium or FB-conditioned medium taken after PDT. Various kinds of cytokines in the supernatants of KC and FB were evaluated by enzymelinked immunosorbent assay (ELISA). The mRNA level of MMPs, transforming growth factor (TGF)-β and collagen type Iα in the FB were determined by real-time polymerase chain reaction (PCR). The melanin content and dopa oxidase activity of the MC were also evaluated. RESULTS: After stimulating FB with KC-conditioned medium, the mRNA of MMP-1 was decreased and the mRNA of collagen type Iα were increased compare to control. However, MMP-3 and TGF-β were not significantly changed. Among the FB stimulating cytokines, a significant elevation of interleukin (IL)-1α, IL-6, tumor necrosis factor (TNF)-α level in KC supernatants was noted after PDT compared with the untreated controls. TGF-β were not significantly altered after PDT. After PDT, significantly reduced melanin content and dopa oxidase activity were noted compared to the control group after 24 and 48h in MC. In addition, MC treated with KC-conditioned medium taken after PDT showed a significant reduction of melanin content and dopa oxidase activity compared with the control groups. Among the well known MC stimulating cytokines from KC, the level of stem cell factor (SCF) in KC-conditioned medium was significantly decreased after PDT, whereas endothelin (ET)-1 and granulocyte-macrophage colony stimulating factors (GM-CSF) were not significantly altered. MC treated with FB-conditioned medium taken after PDT showed a significant reduction of melanin content and dopa oxidase activity compared with control groups. Among the MC stimulating cytokines from FB, the hepatocyte growth factor (HGF) in FB-conditioned medium was significantly decreased after PDT compared to the untreated control. The SCF and basic fibroblast growth factor (bFGF) were not changed after PDT. CONCLUSION: PDT induced new collagen synthesis may be mediated not only by direct effect of PDT on FB but also by indirect effect of PDT on FB through cytokines from KC. In addition, PDT has inhibitory effect of melanogenesis in the human MC. This inhibitory effect of melanogenesis thought to be regulated indirectly by KC and FB as well as directly by PDT. Decreased secretion of SCF from KC and HGF from FB may have crucial role which induce inhibition of melanogenesis of MC after PDT.
Photodynamic therapy, Photorejuvenation, Keratinocyte, Fibroblast, Melanocyte, 광역동 치료, 광회춘, 각질세포, 섬유아세포, 멜라닌세포
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