Development and Application of Therapeutics for Repair of Polytraumatic Volumetric Muscle Loss Injuries

Volumetric muscle loss (VML) injuries lead to permanent functional and cosmetic deficits and are a serious challenge faced by both civilian and military personnel. Further complicating repair of these injuries is extensive simultaneous damage to multiple tissue components, such as nerve and bone outside of the VML injury. Currently there are no therapies available that can completely restore neuromuscular function following polytraumatic VML injury. As a first step in that direction, this thesis proposal work will address the need for therapies targeting repair of both nerve and muscle, in order to improve functional outcomes for polytraumatic VML repair. First, co-culture and bioprinting techniques were applied for the biofabrication of tissue engineered repair constructs. Specifically, in vitro examination of bioprinted HA hydrogels laden with cells reveals the potential for bioprinting of scaffolds incorporating multiple cell types, with a tunable cell matrix architecture. The efficacy of a preferred therapeutic construct, that is, an Assembled Cell-Decorated Collagen (AC-DC) scaffold, was evaluated in a biologically relevant rat tibialis anterior (TA) VML model injury. Longitudinal studies of functional recovery were conducted over a 12 week time frame following surgical creation of a TA VML injury—with or without repair. Second, an in vitro co-culture strategy is evaluated for building engineered skeletal muscle that permits survival of nerve and muscle progenitor cells under identical cell culture conditions. Finally, we have endeavored to identify a reproducible and repairable nerve injury model in vivo that would permit simultaneous repair of muscle and nerve damage to the TA muscle. In short, this dissertation highlights the extant challenges and opportunities associated with designing novel therapeutics that incorporate a variety of cell types and architectures to improve regenerative support for polytraumatic VML injury.