"The creation of adequate tissue constructs and other therapeutic products in tissue engineering and regenerative medicine is a highly challenging task. Adequate vascularization of tissue engineering constructs is an important prerequisite, which could be promoted by allowing stem cells or progenitor cells to reach the site of injury/replacement for tissue repair. The development of new approaches leading to a fast and successful vascularization is therefore one of the most intensively studied subjects in tissue engineering and regenerative medicine. Our previous work has demonstrated that endothelial progenitor cells from peripheral blood or cord blood are a potential autologous cell source for cellular therapies aiming to enhance the neovascularization of tissue engineering constructs. However, in these in vitro angiogenesis studies, the effect of one important system present in vivo, the immune system, has not been taken account.Innate immunity plays a very important role in tissue engineering and regenerative medicine. Following biomaterial implantation the host reactions may include tissue injury, blood-material interactions, provisional matrix formation, acute inflammation, chronic inflammation, granulation tissue development, foreign body reaction, and fibrosis/fibrous capsule development.Innate immune recognition relies on a diverse set of germ line–encoded receptors, termed pattern recognition receptors (PRR), which recognize broad classes of molecular structures common to groups of microorganisms. Toll-like receptors (TLR) are one of the largest and best studied families of PRR. Several studies have linked the TLRs with angiogenesis in a variety of conditions. The final goal of this project is to understand the way that TLR signaling pathways affect angiogenesis and tissue regeneration, as well as to develop potential approaches to promote vascularization of tissue constructs in tissue engineering and regenerative medicine."