Silk-extracellular matrix sponges for striated muscle tissue engineering: Regeneration after injury and disease

Abstract

Event Abstract Back to Event Silk-extracellular matrix sponges for striated muscle tissue engineering: Regeneration after injury and disease Whitney Stoppel1, Kelly E. Sullivan1, David L. Kaplan1 and Lauren D. Black1, 2 1 Tufts University, Biomedical Engineering, United States 2 Sackler School of Graduate Biomedical Sciences at Tufts University, Cell, Molecular, and Developmental Biology, United States Introduction: Repair and regeneration of critically sized defects or injuries to striated muscle tissue, such as cardiac and skeletal muscles, necessitates the use of a complex biomaterial capable of providing structural support that mimics native tissue mechanics and architecture, while promoting host cell integration, vascularization, and remodeling. Silk fibroin protein sponges containing decellularized extracellular matrix (ECM) make an excellent candidate material for the support and repair of injured tissue due to the tunability of the silk scaffold properties, the ease of incorporation of ECM components[1], and demonstrated efficacy in vitro[3],[4]. Materials and Methods: Silk fibroin protein was extracted from B. mori cocoons[2]. ECM was isolated from either adult or fetal porcine cardiac muscle. Anisotropic sponges were formed via directional freezing, followed by lyophilization and water annealing (Fig. 1). Primary and stem cell-derived cardiac progenitors were used to evaluate scaffold formulations in vitro via Western blot analysis and histology. Optimized scaffolds were implanted subcutaneously in Sprague Dawley rats to evaluate cell infiltration and vascularization[1]. In addition, scaffolds were implanted at the site of injury (left ventricle following permanent ligation of the left anterior descending coronary artery to induce myocardial infarction (MI)). Ejection fraction and left ventricle diameters were used to monitor animal health and assess functional outcomes over 8 weeks (echocardiography). Pressure-volume loop analyses, echocardiography, histology, and gene expression of cells in the infarct region and boarder zones were used to determine the degree of repair, cell infiltration, vascularization, and immune response at the termination of the study. All silk-ECM sponges were compared to a silk only control as well as a sham (no repair) condition. Results and Discussion: Addition of ECM components improved cell infiltration in silk sponges implanted subcutaneously[1]. Silk-ECM composite patches also showed improved function of cardiac progenitors in vitro. In a pilot study, trends in ejection fraction and fractional area shortening calculated from echocardiography data suggested that silk-ECM patches were able to restore function similar to pre-injury values after 6 and 8 weeks (p < 0.15) (Fig. 2). Ongoing experiments are evaluating silk-ECM sponges loaded with soluble ECM for their ability to improve cardiac function following myocardial infarction (1 week post-MI implant). Conclusion: Silk fibroin-ECM sponges improve host cell infiltration and remodeling, promote angiogenesis, and improve functional measures in rodent models of cardiac injury. Future work aims to develop materials for the eventual use in the repair of congenital heart defects in pediatric patients. This work was funded in part by the National Institutes of Health P41 program (EB002520).; WLS would like to acknowledge funding from the National Institutes of Health Institutional Research and Academic Career Development Awards program at Tufts University (K12GM074869, Training in Education and Critical Research Skills (TEACRS)).