The role of immune cells in therapeutic angiogenesis: Concepts in tissue engineering

Immune cells can positively regulate new blood vessel formation by secreting proangiogenic mediators and modulating endothelial cell (EC) and endothelial progenitor cell (EPC) activities (e.g., homing). Accordingly, timely management of immune cell behavior is performed to promote angiogenesis and accelerate tissue healing. Different characteristics of biomaterials and scaffolds, including chemical (e.g., composition) and physical (e.g., topography) properties, were proven to influence the angiogenic potential of immune cells. Moreover, specific biomolecular cargoes can be loaded into 3D scaffolds to affect immune cells' behavior in favor of improved angiogenesis. Excess neovascularization can cause pathological conditions, thus establishing a balance between pro- and anti-angiogenic mediators should be taken into account once developing biomaterials and scaffolds for modulating immune cell activities. This review provides an indepth and concise review of the angiogenic-regulatory effects of immune cells and discusses the importance of its modulation by biomaterials and scaffolds for tissue engineering.