Microneedle Radiofrequency Induces Extracellular Matrix Remodeling Through Fibroblast Activation: A Histological Study in a Porcine Model

OBJECTIVES: Microneedle radiofrequency (MRF) is a promising skin rejuvenation treatment. However, the mechanisms underlying its effects on extracellular matrix (ECM) remodeling remain unclear. This study aimed to investigate the immediate histological effects of MRF under varying settings, its short-term impact on collagen and elastin synthesis, and the roles of fibroblasts and adipose-derived stem cells (ADSCs). MATERIALS AND METHODS: Porcine abdominal skin was treated with an MRF device containing 49 insulated microneedles using varying energy parameters (8-12 W; 100-300 ms). Immediate histological responses to treatment were evaluated through hematoxylin and eosin (H&E) staining. Short-term changes in collagen and elastin synthesis at Days 7 and 28 posttreatment were assessed via picrosirius red and Victoria blue staining. Additionally, expression and distribution of ECM remodeling-related proteins (MMPs, TGF-β, EGF, Ki67) and ADSCs were analyzed by multiplex immunohistochemistry (mIHC) and western blot analysis. RESULTS: H&E staining revealed thermal coagulation zones in the dermis immediately after MRF treatment, with zone size increasing with higher power and longer pulse durations (p < 0.05). By Day 28, Collagen I and III densities and organization significantly improved, with the Collagen I/III ratio rising to 7.05 ± 1.21 in the treatment area (p < 0.01) and 3.90 ± 0.37 in the surrounding dermis (p < 0.001). Elastic fibers also showed increased density. mIHC staining demonstrated significant upregulation of MMP-1, MMP-3, and MMP-13 expression in treated and surrounding dermal regions by Day 7 (p < 0.01); however, by Day 28, MMP-1, MMP-9, and MMP-13 expression significantly decreased (p < 0.05), whereas MMP-3 remained elevated. Furthermore, expression levels of TGF-β, EGF, and Ki67 significantly increased by Day 28 (p < 0.05). mIHC analysis of the fibroblast marker FSP-1 coexpression, along with Western blot analysis of Collagen I, Collagen III, MMP-1, MMP-3, TGF-β, and EGF, revealed similar trends. Notably, significant expression of ADSC markers was detected at Day 7 posttreatment (p < 0.01). CONCLUSIONS: MRF predominantly promotes the synthesis of Collagen I and Collagen III, increasing the Collagen I/III ratio, and regulates the expression of MMP-1, MMP-3, MMP-9, TGF-β, and EGF. These factors collectively drive fibroblast activation, migration, and ECM remodeling. These changes are indicative of the potential for MRF to support skin regeneration and rejuvenation. Preliminary findings suggest that ADSCs may contribute to these regenerative processes.