Mesenchymal Stem Cell-derived Exosome Promotes Recovery from UVB-Induced Cell Death in Human Fibroblasts = 줄기세포 유래 엑소좀 처리에 따른 인간 섬유아세포의 UVB 유도 세포 사멸 회복 효과

다국어 초록 (Multilingual Abstract)

Despite growing interest in therapeutic strategies, effective approaches to attenuate UVB-induced damage at the cellular level remain limited. Exosomes, as nanoscale extracellular vesicles with regenerative and immunomodulatory functions, have emerged as promising candidates for cell-free skin rejuvenation therapies. This study aimed to evaluate the protective effects of mesenchymal stem cell–derived exosomes on UVB-induced photoaging in human dermal fibroblast (hDFs). Cells were exposed to UVB irradiation (35 mJ/cm²) and subsequently treated with exosomes at a final concentration of 1×10⁴ particles/mL for 3 h or 6 h. Cell viabilities and morphological changes were assessed by MTT assay and DAPI staining, while protein and gene expression profiles were analyzed by western blotting and qPCR. Exosome treatment did not exert cytotoxicity at the tested dose, whereas DAPI staining confirmed UVB-induced cellular shrinkage and nuclear condensation, which appeared attenuated by exosomes. At 3 h post-irradiation, differences between the UVB and UVB +Exosome (UVB +Exo) groups were minimal; however, at 6 h, exosome treatment markedly mitigated UVB-induced alterations. Western blotting revealed that p38 MAPK, ERK1/2, and Vimentin levels were elevated in the UVB group but decreased following exosome treatment. In parallel, qPCR results showed that COL1A1 expression was reduced and TLR1, TLR3, and TLR4 were upregulated after UVB exposure at 6 h. Interestingly, exosome administration partially restored COL1A1 and attenuated TLR1/3/4 induction, whereas COL3A1 did not show a significant change under our conditions. Collectively, these findings indicate that mesenchymal stem cell–derived exosomes attenuate UVB-induced photoaging in hDFs by suppressing MAPK signaling and TLR-mediated innate immune responses while preserving collagen I expression. This study highlights the therapeutic potential of exosomes as a novel and cell-free intervention to protect hDFs from UVB-mediated damage and delay skin aging.

목차 (Table of Contents)

• CONTENTS i
• LIST OF FIGURES iii
• LIST OF TABLES iv
• ABSTRACT (in English) 1
• INTRODUCTION 3
• 1.1 Skin Structure, HDFs, and ECM Homeostasis 4
• 1.2 Ultraviolet Radiation and Cutaneous Biology 7
• 1.3 Intrinsic vs. Extrinsic Skin Aging 10
• 1.4 Vimentin and Cytoskeletal Dynamics in Photoaging 14
• 1.5 MAPK Signaling Pathway in UVB-Induced Photoaging 18
• 1.6 Toll-Like Receptors and Innate Immune Activation in Photoaging 22
• 1.7 Stem Cells and Their Regenerative Potential 27
• 1.8 Exosomes as Cell-Free Therapy 29
• 1.9 Rationale and Aims of This Study 32
• MATERIALS AND METHODS 34
• 2.1 Cell Culture 35
• 2.2 Exosome Isolation and Characterization 35
• 2.3 UVB Irradiation 36
• 2.4 Exosome Treatment 37
• 2.5 Cell Viability Assays 37
• 2.5.1 MTT Assay 37
• 2.5.2 DAPI Staining 37
• 2.6 Immunocytochemistry 38
• 2.7 Western Blotting Analysis 39
• 2.8 Quantitative PCR (qPCR) 41
• 2.9 Statistical Analysis 43
• RESULTS 44
• 3.1 Characteristics of Exosomes 45
• 3.2 Effects of Exosomes in hDFs 47
• 3.3 Exosomes Attenuate UVB-induced Apoptotic Cell Death 49
• 3.4 Expression of Vimentin Recovered with Exosome 51
• 3.5 Exosome Suppress UVB-Induced Activation of MAPK Signaling 53
• 3.6 Protective Effects of Exosomes on Apoptotic Signaling 55
• 3.7 Collagen-Related Gene Expression in UVB-Irradiated hDFs 58
• 3.8 TLR1, TLR3, and TLR4 Expression in UVB-Irradiated hDFs 60
• DISCUSSION 62
• CONCLUSIONS 68
• REFERENCES 69
• ABSTRACT (in Korean) 85