Enhancing the Repair of Substantial Volumetric Muscle Loss by Creating Different Levels of Blood Vessel Networks using Pre‐Vascularized Nerve Hydrogel Implants

Abstract Volumetric muscle loss (VML) is a significant loss of muscle tissue due to trauma or surgery, resulting in scarring, minimal regeneration, and notable fibrosis. This leads to permanent declines in muscle mass and function. One potential approach to enhance recovery in substantial VML is to restore vascular and neural networks at the injury site. However, the processes of neovascularization and tissue integration at the muscle injury site have not been widely studied. Collagen hydrogels have been explored as scaffolds for cultivating cell‐mediated blood vessels due to their biocompatibility. However, effectively reconstructing blood vessels and guiding host neurons for innervation at the injury site remains challenging. In this study, collagen hydrogels with varying blood vessel‐forming cell densities were subcutaneously implanted in mice, creating pre‐vascularized hydrogels with a wide range of vessel densities (0∼145 numbers/mm 2 ) within a week. Host motor neurons concurrently followed these pre‐formed vessels through coordinated interactions, forming pre‐vascularized nerve hydrogels. These hydrogels were then transplanted into muscle injury sites and evaluated for their muscle repair capabilities through histological and behavioral analyses. The results demonstrated that achieving sufficiently high microvessel densities within the hydrogel construct, which fully occupied the wound area, effectively reconnected with the host vasculature and interacted with neural networks to promote neovascularization, myogenesis, and integration processes, ultimately addressing approximately 63% of the volumetric muscle loss. This article is protected by copyright. All rights reserved