Project Summary There are almost 5 million reconstructive procedures performed annually as a result of traumatic injury, cancer ablation, cosmetic procedures, or combat injuries. The destruction or removal of large amounts of skeletal muscle, termed volumetric muscle loss (VML), resulting from traumatic events such as car crashes or combat injuries, represents a significant health concern. Skeletal muscle is highly vascularized, and relies on adequate infiltration of blood vessels to repair and regenerate. The gold standard for VML repair is autologous grafting, and is limited by reduced functional outcomes and inadequate host-mediated graft revascularization. Current biomaterial-based tissue engineered approaches towards the repair of skeletal muscle tissue after VML rely on passive neovascularization from the host, as opposed to actively recruiting vascular networks to accompany satellite cell infiltration during repair. As such, there remains a significant need to develop materials that will actively stimulate the development of vasculature that will guide organized and aligned skeletal muscle tissue regeneration. We hypothesize that scaffolds that stimulate the rapid creation of a new vasculature and aligned muscle tissue will significantly enhance skeletal muscle repair in VML injuries. To test this hypothesis, we will create a class of biodegradable composite scaffolds that will be implanted into VML injuries to enable the recruitment of endothelial cells and satellite cells. As such, the objective is to create a composite material that promotes in situ regeneration of mature functional muscle tissue. To fabricate these scaffolds, collagen sponges with defined, anisotropic architectures will be fabricated and embedded with angiogenic self-assembling peptide hydrogels, termed SLan (Aim 1). Assessment of the mechanics of scaffolds will complement in vitro analyses of cellular infiltration and compatibility to define material parameters that will induce aligned vascularized skeletal muscle tissue. Scaffolds comprised of collagen, SLan, or composites will then be implanted into a murine model of VML to assess the contribution of each material to enhance VML repair (Aim 2). Particular emphasis will be placed on the ability of these scaffolds to support functional recovery as measured by muscular contraction in longitudinal studies. Histologic assessments will characterize i) the cellular infiltrate and the contribution of aligned scaffolds to guide organized skeletal muscle tissue growth, ii) the modulation of in situ neovascularization and supporting structures, and iii) changes in inflammation. Ultimately, we aim to address two major limitations within skeletal muscle tissue regeneration: i) inadequate vascularization of constructs in situ, and ii) the lack of organized alignment of nascent myofibers during repair of VML injuries; both factors known to inhibit functional recovery. These outcomes will result in the creation of a new class of composite materials to functionally drive cellular infiltration with hydrogels that are specifically designed to recruit specific supporting structures necessary for tissue regeneration and repair.

Project Narrative There is a large, unmet clinical need to develop tissue engineered strategies to treat volumetric muscle loss. We propose the development of off-the-shelf materials that will promote rapid endogenous vascularization and organized skeletal muscle regeneration. Using microfabrication techniques and designer peptide materials, we will evaluate biodegradable composite scaffolds that will ultimately yield functional, organized skeletal muscle tissue in situ.