Background: Aesthetic improvement of the chin is increasingly requested by patients, including those of Chinese origin. Methods: A randomized, evaluator-blinded, no-treatment controlled study evaluated the effectiveness and safety of a flexible hyaluronic acid (HA) filler, Restylane^® Defyne^TM (HA_DEF), in the correction of chin retrusion in a Chinese adult population over 12 months after treatment. On Day 1, subjects were randomized 3:1 into two groups, HA_DEF or delayed-treatment controls, and those in the HA_DEF group were administered treatment. An optional touch-up treatment was administered 1 month after treatment to obtain optimal chin augmentation. The initially untreated control group was offered delayed-treatment after 6 months (including 1-month touch-up). Results: HA_DEF was superior to no-treatment in improving chin retrusion according to the blinded evaluator at 6 months [Galderma Chin Retrusion Scale (GCRS) responder rate (≥ 1-point improvement from baseline) of 81% vs. 5% for untreated controls; p < 0.001, meeting the primary effectiveness objective. A majority of subjects maintained improvement at 12 months (61% in the HA_DEF group). All subjects reported satisfaction with results at 6 months after treatment with HA_DEF and aesthetic improvement rates per the global aesthetic improvement scale (GAIS) were high for 12 months following treatment, with an acceptable safety profile. Conclusions: These results demonstrated HA_DEF to be effective and safe for the correction of mild-to-moderate chin retrusion in Chinese subjects, confirming findings previously observed in a western population. Level of Evidence I: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Objective: This study aimed to chemically synthesize a homotrimeric collagen peptide, evaluate its safety, and assess its effectiveness in promoting collagen synthesis.Methods: A homotrimeric collagen peptide was synthesized and structurally characterized using circular dichroism and infrared spectroscopy. Thermal stability was analyzed by TG-DSC, and molecular weight and amino acid composition were determined. In vitro cytotoxicity testing assessed safety, while UV-induced photoaging experiments evaluated its effects on collagen and elastin synthesis. In vivo studies in BALB/c mice examined its impact on collagen content, skin structure, and angiogenesis.Results: The synthesized collagen peptide exhibited high purity (99.1%) and an amino acid composition of glycine, proline, and hydroxyproline in a balanced ratio (15:17:13). Structural analysis confirmed a stable triple-helical conformation similar to type I collagen with excellent thermal stability (Tm = 326.15°C). Cytotoxicity testing showed no adverse effects on cell viability. In vitro, the peptide significantly enhanced collagen and elastin synthesis in fibroblasts. In vivo, intradermal and subcutaneous injection increased collagen content, improved skin structure, and enhanced microvessel density.Conclusion: This study presents a chemically synthesized homotrimeric collagen peptide with superior purity, structural stability, and biological efficacy in promoting collagen synthesis. Compared to previous studies, this biomimetic material exhibits exceptional thermal stability (Tm = 326.15°C) and a well-balanced amino acid composition, enabling applications in cosmetics and medical devices requiring heat sterilization (e.g., autoclaving), as validated by our patented method (China Patent No. ZL202410309842.9).