PROJECT SUMMARY/ABSTRACT Studies into regeneration of damaged skeletal muscle via the resident stem cell population (satellite cells) in the past 30 years have provided a wealth of knowledge regarding transcriptional, epigenetic, and signaling influences on this process. However, given that muscle tissue is made up of multiple cell types that are essential to its function, surprisingly little is currently known about regeneration of the vascular network that exists physically alongside muscle fibers and is necessary for their physiological function, or of signaling interactions between regenerating myofibers and their microvasculature. To address this gap in knowledge, the Cornelison lab (with expertise in muscle regeneration and molecular signaling) and the Segal lab (with expertise in vascular physiology) have been pursuing studies aimed at identifying molecular and physiological interactions coordinating the repair of muscle and vessels after injury. This proposal will leverage the unique and complementary strengths of both labs and will also develop and apply new 3D imaging and cell culture techniques to advance this goal. Specifically, the applicant will 1) test the requirement for the juxtacrine signaling molecule ephrin-B2 in microvessel regeneration following muscle injury; 2) test the hypothesis that perturbed vessel regeneration will lead to perturbed muscle regeneration; and 3) identify key molecular interactions between endothelial cells and myoblasts in a novel ex vivo system. These experiments will be the first to investigate the role microvessel regeneration plays in muscle regeneration, and the first to examine the role of Eph/ephrin signaling in microvessel regeneration in skeletal muscle. In the course of performing this research, the applicant will receive training that spans physiological, cell biological, and molecular techniques and their interpretations as well as experience in critical thinking, reading, and writing.