Epidermal and Dermal Regeneration Through Sequential Monopolar and Bipolar Radiofrequency: Evidence From an Aging Mouse Model.

Background: It is well established that the aging process triggers various physiological changes, which may manifest as loss of hydration and the degradation of collagen and elastin fibers, ultimately leading to lines, wrinkles, and skin laxity. To restore the skin's youthful appearance, both noninvasive and minimally invasive procedures have been developed.

Objectives: The authors of this study aim to evaluate the safety and efficacy of noninvasive monopolar vs sequential monopolar-bipolar radiofrequency (RF) irradiation from a single tip on skin quality in an aged mouse model.

Methods: The experiment involved male mice aged 4 and 12 months. The Density RF device (Jeisys Global, Seoul, South Korea) used for irradiation employs both monopolar (Classic-Tip) and monopolar-bipolar (High-Tip) RF, operating at a frequency of 6.78 MHz. The device features an automatic impedance matching system that measures impedance in real time and determines the corresponding compensation value. RF irradiation was performed after applying coupling fluid to the dorsal skin of mice (4 cm²) using an energy density of 63.4 J/cm² per shot under anesthesia. RF was applied on Day 0; subsequently, the mice were sacrificed on Days 1 and 28 for sample harvesting and histological study.

Results: The RF-irradiated group has shown a significant increase in skin hydration and elasticity. The aging control group showed a 1.7-fold reduction in epidermal thickness compared with the young control group. However, in comparison with the aging control group, after 28 days, the RF irradiation group showed a substantially thicker epidermis, up to 1.5-fold thicker (monopolar group: 15.797 ± 1.093 µm, monopolar-bipolar group: 15.600 ± 0.963 µm). The monopolar group showed a 1.8-fold (P < .05) increase in collagen density; however, the monopolar-bipolar group showed a 2.4-fold (P < .05) increase. Notably, the monopolar-bipolar group demonstrated a substantial increase in collagen density compared with the controls. Elastin fiber expression significantly increased in both monopolar and monopolar-bipolar groups compared with the controls. However, the highest expression of elastin fibers was observed in the monopolar-bipolar group. Further, polymerase chain reaction analysis confirmed a significant increase in gene markers, such as Blimp1, Fsp1, and Dlk1, suggesting that RF irradiation promotes fibroblast differentiation.

Conclusions: The sequentially monopolar-bipolar RF irradiation (Density High-Tip) system significantly increases epidermal thickness, collagen, and elastin fiber production and promotes fibroblast cell differentiation compared with the monopolar RF alone.

Level of evidence 4 therapeutic: