Bioprinted human skin equivalent for evaluating non-invasive monopolar radiofrequency treatment: a novel approach

To establish a standardized 3D human dermis model for evaluating the biological and mechanical effects of non-invasive monopolar radiofrequency (NMRF) treatment. Collagen-based 3D dermal constructs with human dermal fibroblasts were fabricated via bioprinting and treated with NMRF. Histology, immunofluorescence, SEM, and compression tests were conducted to assess tissue remodeling. Conditioned media from treated constructs were applied to fibroblasts, melanocytes, and keratinocytes to evaluate paracrine effects on migration, pigmentation, and oxidative stress. NMRF treatment led to increased fibroblast activity and cellular enlargement, along with the formation of a denser and more organized collagen network, as demonstrated by histological and SEM analyses. Immunofluorescence staining revealed a marked increase in type I collagen deposition surrounding activated fibroblasts. Biomechanical testing showed a significant rise in compressive modulus and reduction in tissue dimensions, indicating enhanced dermal stiffness and matrix remodeling. Furthermore, conditioned media derived from NMRF-treated constructs significantly promoted fibroblast migration in wound healing assays, suppressed the expression of melanogenesis-related genes (MITF, tyrosinase, Trp-1, and Trp-2) in α-MSH-stimulated B16F10 melanoma cells, and improved the survival of keratinocytes exposed to oxidative stress (H₂O₂). This 3D dermis model enables reproducible assessment of NMRF-induced dermal remodeling. NMRF improves dermal structure and modulates paracrine signals, suggesting therapeutic potential in skin tightening, pigmentation control, and tissue regeneration.