Clinical applications of a novel poly‐L‐lactic acid microsphere and hyaluronic acid suspension for facial depression filling and rejuvenation

BACKGROUND: Poly L-lactic acid (PLLA) can stimulate fibrous tissue regeneration to exert a filling effect. However, severe inflammatory reactions and unsatisfactory effects remain a concern. OBJECTIVE: Herein, we describe the mechanism of action, efficacy, and safety of PLLA microspheres in suspension (PLLA-b-PEG/HA) for facial contouring and soft tissue augmentation. METHODS: PLLA-b-PEG/HA, ssynthesized by copolymerization with ethylene glycol, were suspended in hyaluronic acid (HA). Physiological verification was performed using scanning electron microscopy and X-ray computed tomography. PLLA-b-PEG/HA were subcutaneously injected into the dorsal region of 4-month-old rabbits. Ultrasound assessed volumetric capacity at 3 days and 1, 2, 4, and 12 weeks. The inflammatory response, collagen production, and HA degradation were evaluated. A retrospective case series of 10 patients who received PLLA-b-PEG/HA injections was conducted to assess long-term efficacy and safety. RESULTS: PLLA-b-PEG exhibited a spherical structure with a smooth surface (20-45 μm diameter). In rabbits, implant site volume increased within 4 weeks, gradually decreasing thereafter. Fibrous capsules, microvessel density, and new collagen fiber formation progressively increased at 4, 12, and 26 weeks after injection. Clinical data demonstrated significant improvements in face contouring at months 3 and 12 after injection. All patients showed improved internal contours based on the Global Aesthetic Improvement Scale. After 12 months, 90% of the patients retained good shaping and support effects with minimal adverse reactions. CONCLUSIONS: PLLA-b-PEG/HA demonstrated superior biocompatibility and facial regeneration potential, with outstanding dual collagen-stimulating properties. The clinical efficacy and safety of PLLA-b-PEG/HA have been validated and established as a promising therapeutic option.