Adipogenesis and Stem Cell Activation in Facial Fat After Repeated Low-energy Continuous Monopolar Radiofrequency: Ultrasound, 3D Imaging, and Histological Study.

BACKGROUND

High-intensity pulsed radiofrequency (RF) devices are effective for skin tightening but may cause facial fat atrophy in lean individuals. This study investigates whether repeated low-energy continuous monopolar RF could stimulate adipogenesis and stem cell activation, providing a noninvasive approach to facial volumization.

METHODS

In this prospective, single-center study, 25 healthy women (body mass index <21 kg/m2) received 5 sessions of 115-W continuous monopolar RF at 3-week intervals. Facial volume and soft tissue thickness were assessed at baseline and 18 weeks using QuantifiCare and Morpheus 3D imaging and ultrasound. One participant underwent paired skin biopsies for immunohistochemical analysis of CD166, CD34, and CD31. Clinical outcomes were evaluated using the Global Aesthetic Improvement Scale.

RESULTS

Body weight remained stable throughout the study. Three-dimensional imaging demonstrated significant increases in tissue thickness (QuantifiCare, +0.86 ± 0.21 mm, P < 0.0001; Morpheus, +1.01 ± 0.22 mm, P = 0.0002). Ultrasound showed significant increases in total fat thickness (14.73 ± 2.02 to 16.33 ± 1.99 mm, P < 0.00001) and superficial fat thickness (5.99 ± 0.78 to 7.64 ± 0.86 mm, P < 0.0001). Histology demonstrated increased CD166 and CD34 expression, consistent with stem/progenitor cell activation, and increased CD31 expression, indicating angiogenesis. Global Aesthetic Improvement Scale scores showed high improvement in midface volume, skin texture, and elasticity.

CONCLUSIONS

This study is the first to present convergent evidence from 3D imaging, ultrasound, and histological analysis demonstrating that repeated low-energy continuous monopolar RF increased subcutaneous fat thickness and transiently activated mesenchymal stem/progenitor cells in human facial tissue. The increased fat layer was consistent with adipogenic remodeling rather than inflammatory edema and persisted beyond the treatment period.