Angiogenesis and Vasculogenesis in Health and Disease.

Angiogenesis is an important process that takes place during new blood vessel formation from preexisting ones. The first sign of vasculature occurs in the early phases of embryonic development when mesoderm-derived endothelial progenitor cells (EPCs) proliferate and form a primitive network of vessels during vasculogenesis. Vascular Endothelial Growth Factor (VEGF) is the most crucial factor in this process since it induces cell proliferation and migration. This primitive vascular structure, also known as the primary capillary plexus, is progressively remodeled in order to establish a mature circulatory network. Although vasculogenesis was thought to be restricted to embryonic development, recent studies support the existence of bone marrow-derived EPCs in adulthood that can contribute to neovascularization. In the adult, angiogenesis is mostly restricted to the ovarian cycle, injured tissues, and organ growth. Therefore, endothelial cells are considered stable and almost quiescent showing limited turnover in the adult vasculature. The lack of balance of pro- and antiangiogenic cues is considered one of the most crucial features that distinguish physiological from pathological angiogenesis. It is not surprising that we have witnessed an increase in interest in the field of angiogenesis research during the last decades with the main focus on trying to understand how to modulate blood vessel growth in order to develop new clinical approaches for a broad range of angiogenesis-related diseases. The main focus of this special issue is to highlight the complicated mechanism of angiogenesis in many different fields of cell biology. The special issue, which compiles a series of seven original research papers and two review articles, covers relevant aspects of vascular biology that are deeply discussed by experts in the field.