### **1.1 Causes of Skin Aging – Academic Knowledge (English)** --- #### 1. Intrinsic Aging - **Cellular Senescence**: Fibroblasts undergo telomere shortening and reduced proliferative capacity, secreting pro-inflammatory factors (SASP: senescence-associated secretory phenotype). - **Collagen Degradation**: Collagen type I and III synthesis declines ~1% per year after the mid-20s, while MMP (matrix metalloproteinase) activity increases, accelerating ECM breakdown. - **Elastin Fragmentation**: Elastic fibers lose integrity, leading to decreased recoil capacity. - **Hyaluronic Acid Decline**: Reduced glycosaminoglycan production diminishes dermal hydration and turgor. - **Mitochondrial Dysfunction**: Accumulated ROS (reactive oxygen species) damage proteins, lipids, and DNA, impairing repair mechanisms and accelerating dermal thinning. --- #### 2. Extrinsic Aging - **UV Radiation (Photoaging)** - UVA (320–400 nm): penetrates dermis, generates ROS, activates MMP-1 → collagen breakdown. - UVB (290–320 nm): direct DNA damage via thymine dimers → apoptosis, mutations. - Clinical consequence: solar elastosis, dyspigmentation, coarse wrinkles. - **Lifestyle Factors** - **Smoking**: Nicotine-induced vasoconstriction reduces oxygen supply; free radicals promote collagen degradation; Vitamin C depletion impairs collagen hydroxylation. - **Alcohol**: Acute dehydration + chronic ROS/acetaldehyde toxicity; vasodilation leads to persistent telangiectasia; nutrient deficiency impairs skin repair. - **Nutrition**: Excess sugar → AGEs (Advanced Glycation End Products) cross-link collagen, reducing elasticity; antioxidant deficiency (Vitamins A, C, E, selenium, zinc) accelerates oxidative injury. - **Pollution & Stress** - PM2.5 and heavy metals disrupt barrier function, increase oxidative stress, and worsen pigmentation. - **Hormonal Changes** - Estrogen decline post-menopause: up to 30% reduction in dermal collagen within 5 years; thinning, dryness, loss of vascularity. - Androgen decline in men: reduced sebaceous activity → dryness, decreased barrier integrity. --- #### 3. Structural Aging - **Bone Resorption** - Orbital rim enlargement → periorbital hollowing. - Maxillary retrusion → flattening of midface, deep nasolabial folds. - Mandibular resorption → blunting of jawline, jowl formation. - **Fat Redistribution** - Deep fat compartments (e.g., medial SOOF, deep medial cheek) atrophy → hollowing. - Superficial fat pads descend under gravity → nasolabial folds, jowls. - Buccal fat hypertrophy further blunts contour. - **Ligaments & Fascia** - Retaining ligaments (zygomatic, mandibular, orbital) stretch → diminished anchoring capacity. - SMAS (Superficial Musculoaponeurotic System) loses elasticity → soft tissue descent. --- #### 4. Clinical Manifestations - Fine wrinkles → collagen and HA loss. - Deep folds → fat descent + bone resorption. - Sagging jawline/neck bands → ligament elongation + SMAS laxity. - Volume loss (tear trough, temple) → deep fat atrophy. - Pigmentation & rough texture → UV, ROS, melanocyte dysregulation. --- # Chapter 1.2 Principles of Skin Lifting – Academic Knowledge --- ## 1. Skin Lifting의 핵심 개념 피부 리프팅(skin lifting)의 원리는 단순히 "피부를 당기는 것"이 아닙니다. 노화는 **다층 구조(피부–진피–지방–근막–골격)** 에서 동시에 진행되므로, 치료도 **세포 수준 → 조직 수준 → 구조 수준**으로 접근해야 합니다. --- ## 2. **Collagen & Elastin Remodeling** - **원리**: 열에너지(RF, HIFU, Laser 등)를 진피 깊은 층(55–65°C)까지 전달 → collagen triple helix 변성(denaturation) → 즉각적인 수축 + fibroblast 활성화 → 새로운 collagen & elastin 합성. - **Heat Shock Proteins (HSPs)**: fibroblast 내에서 HSP47, HSP70 발현 증가 → ECM 재생 촉진. - **Timeline** - Immediate effect: collagen contraction (tightening). - 3–6개월: neocollagenesis, elastogenesis. - 12–18개월: remodeling 안정화. - **Clinical implication**: Thermage, Ultherapy, Microneedling RF, Fractional CO₂ laser. --- ## 3. **Volume Restoration** - **문제**: Midface fat pad, temporal fat, deep orbital fat 등에서 volume loss 발생 → hollowing, sagging accentuation. - **해결 원리**: 결손 부위를 채워 facial convexity & lifting illusion 회복. - **방법** - **Injectables**: Hyaluronic acid, Calcium hydroxylapatite, Poly-L-lactic acid. - **Autologous fat graft**: adipose-derived stem cell 포함 → regenerative potential. - **Biomechanical effect**: 단순 볼륨 보충 외에도 피부 표면 tension ↑ → lifting effect 강화. --- ## 4. **Tissue Repositioning** - **Surgical**: - SMAS facelift: superficial musculoaponeurotic system을 mobilization & fixation. - Deep-plane facelift: retaining ligament release + anatomic repositioning. - **Non-surgical**: - Thread lift (PDO, PLLA, PCL): barbed threads가 기계적 traction 제공 + fibroblast biostimulation. - **핵심 원리**: 늘어진 ligament와 fascia를 재고정하여 중력 방향 하강을 역전시킴. --- ## 5. **Regeneration & Biological Stimulation** - **Platelet-Rich Plasma (PRP)**: PDGF, VEGF, TGF-β → fibroblast proliferation & angiogenesis. - **Exosomes**: stem-cell derived vesicles → collagen synthesis gene expression↑. - **Stem-cell conditioned media**: paracrine effect → ECM remodeling. - **Clinical implication**: Energy-based device + regenerative therapy 병합 시 synergistic effect. --- ## 6. **Skin Quality Optimization** 리프팅의 효과는 **피부 질(skin quality)** 과 직결됩니다. - Epidermal rejuvenation: fractional CO₂, Er:YAG, IPL → 색소·질감 개선. - Barrier repair: topical retinoids, antioxidants, moisturizers → 유지 효과 연장. - Sun protection: photoaging 억제 → 결과 longevity 보장. --- ## 7. **Patient-Tailored Strategy** 리프팅 원리는 환자 상태에 따라 다르게 적용해야 합니다. - **Mild laxity (30–40대)**: collagen remodeling 중심 (RF, HIFU, fractional laser). - **Moderate laxity (40–50대)**: collagen remodeling + volume restoration + thread lift. - **Severe laxity (60대 이상)**: surgical facelift ± energy-based device maintenance. --- ## 8. **Key Integration** 리프팅은 **3대 축**으로 요약할 수 있습니다. 1. **Skin & ECM**: collagen remodeling → 피부 자체의 탄력 복원 2. **Volume**: filler/fat → facial convexity 회복 3. **Structure**: ligament/SMAS repositioning → gravity effect 교정 이 세 가지를 균형 있게 결합하는 것이 최적의 리프팅 전략입니다. ---