Injectable poloxamer-based thermogel as a delivery platform for agmatine and hyaluronic acid in muscle tissue...

Volumetric muscle loss (VML) results in permanent functional deficits for which current therapeutic strategies are insufficient. We hypothesized that an injectable, thermoresponsive hydrogel enabling localized delivery of agmatine sulfate (AgS) and hyaluronic acid (HA) could synergistically promote robust neuromuscular regeneration. A poloxamer-based thermogel was systematically optimized using a 3² full factorial design. The lead formulation exhibited a physiologically advantageous gelation temperature (27 ± 1.03°C) and time (42 ± 1.4 s), with rapid bioactive release (85-90% within 18-24 h) matched to the critical satellite cell activation window. In vitro degradation studies confirmed complete gel erosion, providing burst delivery during the acute injury phase. In a rat tibialis anterior VML model, the AgS-HA combination therapy demonstrated profound synergistic effects, restoring grip strength and normalizing complex gait parameters to near-control levels. This functional recovery was corroborated by significantly reduced serum creatine kinase, indicating reduced muscle damage. Histopathological analysis revealed near-complete restitution of mature, organized myofiber architecture with minimal fibrosis, contrasting with extensive scar tissue in control groups. Notably, functional recovery occurred without significant modulation of systemic inflammatory markers (IL-6, IL-10, TNF-α), suggesting regeneration proceeds through direct pro-myogenic, anti-fibrotic, and neurovascular mechanisms rather than systemic anti-inflammatory effects. These findings demonstrate that a thermoresponsive hydrogel platform for rapid AgS and HA delivery effectively promotes comprehensive structural and functional recovery, representing a potent and clinically translatable strategy for VML.