Photothermally activated hydrogel system for skeletal muscle repair in stress urinary incontinence

Stress urinary incontinence (SUI), primarily caused by weakening of the external urethral sphincter (EUS) muscle, remains a major clinical challenge, especially in aging or postpartum populations. Skeletal muscle regeneration at the sphincter is a promising therapeutic approach. In this study, a multifunctional nanocomposite hydrogel was developed, composed of gelatin, hyaluronic acid (HA), tannic acid (TA), silver nitrate (AgNO₃), and copper sulfide (CuS) nanoparticles and designed to be responsive to 1064nm laser irradiation for enhanced skeletal muscle regeneration. Upon 1064nm NIR irradiation, localized hyperthermia (≤55°C) was induced to promote muscle satellite cell proliferation and angiogenesis. In vitro, C2C12 myoblasts were cultured on the hydrogel under photothermal stimulation. For in vivo testing, hydrogels were injected into the skeletal muscle of the rat hindlimb, followed by 1064 nm laser irradiation. Histological analysis showed increased muscle fiber regeneration (40%) and reconstruction of skeletal muscle tissue. The current study demonstrated that the proposed hydrogel with 1064nm laser effectively promotes skeletal muscle regeneration and restores skeletal muscle function in a rat model. Further study will apply the developed hydrogel and 1064nm laser to EUS injury in an SUI animal model and investigate its potential for clinical translation as a non-invasive treatment for muscle disorders.