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Published on: April 16, 2018
Potential Molecular Mechanisms Involved in 5-Aminolevulinic Acid-Based Photodynamic Therapy against Human
Mengling Chang1, Xiaorong Ma, Tianxiang Ouyang
1Shanghai, People's Republic of China From the Department of Plastic and Reconstructive Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University.
Background:
Hypertrophic scars are manifestations of an abnormal process of tissue repair. Although photodynamic therapy is a promising treatment, details of the mechanisms underlying its inhibitory effects remain to be elucidated.
Methods:
Fibroblasts were isolated from human hypertrophic scar specimens and subjected to photodynamic therapy; 5-aminolevulinic acid was used as a photosensitizer. The accumulation of 5-aminolevulinic acid-derived protoporphyrin IX was detected under fluorescence microscopy. The potential cytotoxicity of 5-aminolevulinic acid alone and with photodynamic therapy was measured by 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide. Hoechst 33258 staining and flow cytometry were conducted to search for clues to apoptosis. Protein and/or mRNA expression levels of apoptosis-related pathways and other hypertrophic scar pathogenesis-associated signaling were investigated by Western blot analysis and/or real-time polymerase chain reaction.
Results:
Protoporphyrin IX accumulation peak was achieved at 1.0 mM 5-aminolevulinic acid. 5-Aminolevulinic acid ranging from 0 to 1.0 mM was demonstrated to be noncytotoxic but reduced cell viabilities in a dose-dependent manner with acid-based photodynamic therapy were demonstrated. Reduction of cell viability was attributed mainly to cell apoptosis and probably to mechanisms such as up-regulation of p53/p21, Bax/Bcl-2 ratio, and cleaved caspase-3. Concurrently, deregulation of transforming growth factor-β1-mediated signaling, serving as another putative mechanism underlying hypertrophic scar formation, was found to be reversely modulated in response to acid-based photodynamic therapy.
Conclusion:
The p53-related apoptosis pathway and transforming growth factor-β1-mediated signaling may be important factors used to predict and evaluate the treatment outcomes of 5-aminolevulinic acid-based photodynamic therapy used in hypertrophic scar patients.
Clinical Question/Level Of Evidence:
Therapeutic, V.
Insights
Photodynamic therapy using 5-aminolevulinic acid effectively reduces hypertrophic scar fibroblast viability by inducing apoptosis. This treatment modulates key pathways like p53 and transforming growth factor-β1, offering potential for improved scar treatment outcomes.
Area of Science:
- Dermatology
- Cell Biology
- Biochemistry
Background:
- Hypertrophic scars result from abnormal tissue repair processes.
- Photodynamic therapy (PDT) shows promise for treating hypertrophic scars, but its mechanisms require further elucidation.
Purpose of the Study:
- To investigate the mechanisms by which 5-aminolevulinic acid-based photodynamic therapy (ALA-PDT) affects hypertrophic scar fibroblasts.
- To explore the role of apoptosis and specific signaling pathways in ALA-PDT's inhibitory effects on hypertrophic scar tissue.
Main Methods:
- Human hypertrophic scar fibroblasts were treated with 5-aminolevulinic acid (ALA) and PDT.
- Cell viability was assessed using MTT assays.
- Apoptosis was evaluated via Hoechst staining and flow cytometry.
- Protein and mRNA expression of apoptosis-related and scar pathogenesis-associated pathways were analyzed using Western blot and real-time PCR.
Main Results:
- ALA-PDT reduced fibroblast viability in a dose-dependent manner without significant cytotoxicity at tested concentrations.
- The reduction in cell viability was primarily attributed to apoptosis, evidenced by the upregulation of p53/p21, increased Bax/Bcl-2 ratio, and cleaved caspase-3.
- ALA-PDT also modulated transforming growth factor-β1 signaling, a key factor in hypertrophic scar formation.
Conclusions:
- The p53-related apoptosis pathway is a significant mechanism underlying ALA-PDT's efficacy in treating hypertrophic scars.
- Modulation of transforming growth factor-β1-mediated signaling by ALA-PDT is another crucial factor.
- These pathways may serve as predictive markers for treatment outcomes in hypertrophic scar patients receiving ALA-PDT.
