Surgical corner. Evaluation of the wound healing response after deep dermal heating by fractional micro-needle radiofrequency device.

Fractional Radiofrequency Microneedles (FRM) are minimally invasive devices that use inserting bipolar radiofrequency for deep dermal heating, has been introduced. We investigated the tissue response after FRM according to different energy levels in porcine skin.Porcine back skin was used in the study. A FRM device was composed of 49 insulated needles. Needles were vertically inserted with 1.5mm depth and four different energy levels were used to examine wound healing response chronologically. Histologic evaluation was done by hematoxylin & eosin (H&E) and heat shock proteins (HSP) 47 staining for immediately after, 2 days after, 14 days after, 28 days after and 10 weeks after the procedure. RT-PCR was done for various cytokines including HSP47, HSP72, metalloproteinase (MMP), and extracellular matrix (ECM) proteins.FRM treatment generated a thermally coagulated zone localized in the reticular dermis, without damaging the epidermis. The coagulation necrosis zone in H&E staining was replaced by new collagen tissue over 10 weeks. RT-PCR studies revealed an increase in HSP, MMPs, and ECM proteins. In the high energy level procedure, an increased number of fibroblasts were found.FRM treatment induced a dermal remodeling process including neocollagenesis in the deep dermis. From this result, FRM is expected to provide a good and positive efficacy for skin rejuvenation.