Background: Photoaging represents a significant clinical challenge with limited effective therapeutic interventions capable of reversing established UV-induced damage. While conventional laser therapies rely on thermal mechanisms with associated complications, picosecond laser-induced optical breakdown (LIOB) offers a revolutionary photomechanical approach. This study provides the first comprehensive molecular characterization of photoaging reversal mechanisms following consecutive 755 nm Alexandrite picosecond laser treatments. Methods: Thirty female BALB/c nude mice underwent validated UV irradiation protocols to induce photoaging, followed by randomization into five groups (n=6 each): control, UVA-exposed without laser, UVB-exposed without laser, UVA-exposed with consecutive laser treatments, and UVB-exposed with consecutive laser treatments. Three consecutive picosecond laser sessions (755 nm, 0.71 J/cm², 500 pulses with diffractive lens array) were administered post-induction. Comprehensive assessments included wrinkle scoring, erythema quantification, transepidermal water loss measurement, collagen intensity evaluation, histological analysis, and immunohistochemical molecular characterization. Results: Consecutive picosecond laser treatments produced remarkable photoaging reversal across multiple biological systems. Wrinkle scores decreased from 2.11±0.78 to 0.78±0.67 in UVB-treated groups. LIOB simultaneously activated TGF-β/Smad pathways, enhanced collagen synthesis, reduced matrix degradation (decreased MMP-9 expression), restored barrier function (increased filaggrin and aquaporin 3 expression), and resolved inflammation (reduced NF-κB signaling). Histological analysis confirmed significant collagen regeneration and normalized epidermal architecture. Conclusions: This investigation establishes consecutive LIOB as a paradigm-shifting therapeutic approach that reverses photoaging through coordinated activation of repair pathways while avoiding thermal damage. The comprehensive molecular mechanisms elucidated provide robust scientific foundation for clinical translation, positioning consecutive picosecond laser technology as a transformative advancement in photoaging treatment with unprecedented efficacy and safety profiles.
Chang et al. (Tue,) studied this question.