Abstract
BACKGROUND: Initial and early swelling post injection of hyaluronic acid (HA) filler are considered to affect outcomes and complications in patients; however, the contribution of HA filler type to swelling postinjection remains undetermined. Here, initial and early swelling post injection of HA fillers manufactured via different crosslinking technologies was evaluated in mice. METHODS: Mice received injections of HA fillers or controls: High Concentration Equalized (HICE), Stabilized High Concentration Equalized (S-HICE), High molecular Ideal, VYCROSS, NASHA, HICE control, non-HICE control, or no HA control. Initial and early swelling were evaluated via magnetic resonance imaging and collagen deposition via histological evaluation over 28 days. RESULTS: Mice (N = 65) were allocated to 13 groups (per group, n = 5) to receive subcutaneous injections of HA filler or control. Maximum swelling in descending order was High molecular Ideal, 290%; non-HICE control, 256%; VYCROSS 1, 249%; S-HICE 2, 248%; S-HICE 1, 238%; S-HICE 3, 226%; VYCROSS 2, 210%; HICE 1, 203%; HICE 2, 184%; NASHA 1, 174%; HICE control, 159%; NASHA 2, 148%; and no HA control, 100.0%. The mean (SD) collagen area in the residual substance ranged from 2525 (3612) µm(2)/HPF (high-power field [×400]) for NASHA 2 to 18,870 (4544) µm(2)/HPF for S-HICE 2. The mean (SD) collagen area around the substance ranged from 9879 (2923) µm(2)/HPF for VYCROSS 1 to 15,248 (7005) µm(2)/HPF for S-HICE 3. CONCLUSIONS: HA fillers manufactured via different crosslinking technologies may lead to different levels of initial and early swelling and collagen stimulation over 28 days.