Acrylated Hyaluronic-Acid Based Hydrogel for the Treatment of Craniofacial Volumetric Muscle Loss.

Current treatment options for craniofacial volumetric muscle loss (VML) have disadvantages and cannot fully restore normal function. Bio-inspired semisynthetic acrylated hyaluronic acid (AcHyA) hydrogel, which fills irregularly shaped defects, resembles an extracellular matrix, and induces a minimal inflammatory response, has shown promise in experimental studies of extremity VML. We therefore sought to study AcHyA hydrogel in the treatment of craniofacial VML. For this, we used a novel model of masseter VML in the rat. Following the creation of a 5 mm × 5 mm injury to the superficial masseter and administration of AcHyA to the wound, masseters were explanted between 2 and 16 weeks postoperatively and were analyzed for evidence of muscle regeneration including fibrosis, defect size, and fiber cross-sectional area (FCSA). At 8 and 16 weeks, masseters treated with AcHyA showed significantly less fibrosis than nonrepaired controls and a smaller decrease in defect size. The mean FCSA among fibers near the defect was significantly greater among hydrogel-repaired than control masseters at 8 weeks, 12 weeks, and 16 weeks. These results show that the hydrogel mitigates the fibrotic healing response and wound contracture. Our findings also suggest that hydrogel-based treatments have potential use as a treatment for the regeneration of craniofacial VML and demonstrate a system for evaluating subsequent iterations of materials in VML injuries.