Changes in Dermal Thickness in Biopsy Study of Histologic Findings After a Single Injection of Polycaprolactone-Based Filler into the Dermis

BACKGROUND: During aging, facial skin thins, atrophies, and loses elasticity. Subdermal filler injections can volumize and treat wrinkles but cannot directly change dermal thickness. Polycaprolactone (PCL) fillers can improve skin texture and quality through dermal thickening and inducing neocollagenesis. Through biopsy study, evidence of neocollagenesis will be introduced. OBJECTIVES: In this single-clinic prospective study, 13 patients received a single injection of diluted 0.5 cc of PCL filler in the facial dermis except the right temple area for intra-individual control study. METHODS: A biopsy was performed from temple skin at 1 year for all patients. An additional biopsy was performed at 2 weeks and 4 years posttreatment for 3 patients. Dermal thickness was measured with sonography after 1 year. RESULTS: On average, the mean rate of temporal skin thickness in biopsy specimens (n = 117 points in 13 patients) at 1 year posttreatment increased by 26.74% ± 9.26% from 1412.41 μm ± 69 μm to 1781.11 μm ± 110 μm (P < 0.001). On average, the mean thickness of facial skin (n = 39 points in 13 patients) measured by ultrasound at 1 year increased by 21.31% ± 4.34%. Around PCL particles, many fibroblasts, giant cells, new capillaries, new collagen, and elastic fibers were found in various stains. CONCLUSIONS: Facial dermal thickness increased after intradermal injection of PCL filler by neocollagenesis to treat skin atrophy. PCL filler may last more than 4 years in the dermis. LEVEL OF EVIDENCE: 4: [Image: see text]