Pilot Study to Evaluate the Subcutaneous Tissue Effects of Four Skin Rejuvenation Procedures on a Porcine Model
With advancements in device technology and availability, there is a demand among some patients for non-surgical and minimally invasive options for facial rejuvenation. Although Botox remains the most common aesthetic procedure performed by plastic surgeons, there are many other neurotoxins and fillers currently available for the treatment of wrinkles. Radiesse (calcium hydroxylapatite) and Sculptra (poly-L-Lactic acid), for example, are dermal fillers FDA-approved to smoothen moderate to severe facial wrinkles and folds. There are also non-surgical and minimally invasive options for the treatment of skin laxity. Tissue heating with microfocused ultrasound targets the deep dermis and subcutaneous tissue, where focused damage is thought to cause collagen remodeling and resultant skin tightening. Microneedling with bipolar fractional radiofrequency induces both mechanical and thermal damage. The microneedling treatment inflicts injury on the skin, resulting in the wound healing process and resultant collagen production. Additionally, the heat generated by radiofrequency is thought to lead to collagen denaturation and remodeling, as well as a reduction in adipose tissue.
While these procedures are routinely performed in many clinics, limited investigation has been undertaken to examine their effects on subcutaneous tissue. In particular, the degree of inflammation beneath the skin associated with these dermal treatments has not been evaluated in either human or animal models. The objective of this study, therefore, is to investigate the long-term subcutaneous effects of these four minimally invasive aesthetic treatments.
Methods/Technique
:After receiving approval from the university Institutional Animal Care and Use Committee (IACUC), four aesthetic procedures were performed, each at two abdominal sites, on the abdomen of a pig (eight treatment sites total). These treatments included two injectables, 1cc of calcium hydroxylapatite (Radiesse; Merz North America, Inc., Raleigh, North Carolina) and 5cc of poly-L-lactic acid (Sculptra Aesthetic; Galderma Laboratories, L.P., Fort Worth, TX), as well as a bipolar fractional radiofrequency microneedling treatment (Profound System; Candela Medical, Wayland, Massachussetss) and a microfocused ultrasound treatment (Ulthera; Merz Aesthetics, Raleigh, North Carolina), both over a 2 in. x 2 in. area. All four aesthetic treatments were conducted in the same session under general anesthesia using 0.04 mg/kg atropine. The areas that received treatment were tattooed to identify the location and type of treatment performed. An untreated area was also marked to serve as a control. 90 days post-treatment, the treated skin and underlying subcutaneous tissue, as well as the control area, were excised to examine any histological changes resulting from the treatment. Additionally, gene expression assays of the treated skin and subcutaneous tissue were performed to assess for inflammatory markers.
Results/Complications
:All four aesthetic procedures were successfully performed without complication. In the four areas treated with calcium hydroxylapatite and poly-L-Lactic acid, mild pinpoint bleeding and edema was noted immediately post-injection, which subsided within minutes. Following bipolar fractional radiofrequency microneedling treatment, transient pinpoint bleeding was also observed, as well as mild bruising and moderate edema and erythema, all of which are anticipated reactions. The bruising, edema, and erythema resolved within 2 weeks of treatment. Microfocused ultrasound is a non-invasive treatment, and only mild, transient erythema was noted immediately following treatment. No aesthetic complications or unanticipated adverse events occurred as a result of the procedures.
Biopsies from the eight abdominal sites, as well as the untreated area, were successfully extracted for histology and gene expression analysis. Histologic staining allowed for visualization of the skin architecture, including the epidermis, dermal-epidermal junction, and subcutaneous layer. No significant changes were noted in the subcutaneous tissue following injection with either filler. After treatment with both energy-based devices, changes in the expression levels of extracellular matrix genes, as well growth factors and inflammatory genes, could be measured in the excised samples, even 90 days post-treatment.
Conclusion
:The results of this exploratory study highlight the impact several dermal aesthetic treatments have on deeper subcutaneous tissues and immune activity within the skin. While subcutaneous effects are anticipated with microfocused ultrasound, which is known to target the deep dermis and subcutaneous tissue, bipolar fractional radiofrequency microneedling technology is often advertised as producing a controlled thermal injury specifically to the dermis. Gene expression analysis, however, showed evidence of inflammatory processes in the subcutaneous tissue, deeper than what is originally anticipated. These results may be used to educate both future patients and clinicians on previously unknown risks to underlying tissues beneath the intended dermal treatment area.