Bipolar fractional radiofrequency treatment induces neoelastogenesis and neocollagenesis

Abstract

We recently introduced Renesis, a novel minimally invasive radiofrequency (RF) device, for the treatment of human skin. The wound healing response post-fractional RF (FRF) treatment was examined in human subjects. The FRF system delivered RF energy directly within the dermis via 5 micro-needle electrode pairs. Tissue temperature was held at 72 degrees C for 4 seconds using an intelligent feedback system. The wound healing response was evaluated histologically and by RT-PCR up to 10 weeks post-RF treatment. Neoelastogenesis and the role of heat shock proteins (HSPs) were assessed by immunohistochemistry. FRF treatment generated a RF thermal zone (RFTZ) pattern in the reticular dermis that consisted of zones of denatured collagen separated by zones of spared dermis. RFTZs were observed through day 28 post-treatment but were replaced by new dermal tissue by 10 weeks. HSP72 expression rapidly diminished after day 2 while HSP47 expression increased progressively through 10 weeks. Reticular dermal volume, cellularity, hyaluronic acid, and elastin content increased. RT-PCR studies revealed an immediate increase in IL-1beta, TNF-alpha, and MMP-13 while MMP-1, HSP72, HSP47, and TGF-beta levels increased by 2 days. We also observed a marked induction of tropoelastin, fibrillin, as well as procollagens 1 and 3 by 28 days post-treatment. Our study revealed a vigorous wound healing response is initiated post-treatment, with progressive increase in inflammatory cell infiltration from day 2 through 10 weeks. An active dermal remodeling process driven by the collagen chaperone HSP47 led to complete replacement of RFTZs with new collagen by 10 weeks post-treatment. Furthermore, using both immunohistochemical and PCR studies, we successfully demonstrated for the first time evidence of profound neoelastogenesis following RF treatment of human skin. The combination of neoelastogenesis and neocollagenesis induced by treatment with the FRF system may provide a reliable treatment option for skin laxity and/or rhytids.