Glossary

Vascular endothelial growth factor (VEGF), also called vascular permeability factor (VPF), is a specific type of protein known as a signal protein that encourages the body’s creation of blood vessels. When cells release this protein, it “signals” the body to take action — in the case of VEGF, either by angiogenesis or vasculogenesis. Angiogenesis is the creation of new blood vessels from existing vasculature, while vasculogenesis is the creation of the circulatory system in the embryo. The vascular endothelial growth factor protein is critical to human survival as it’s the protein that restores the supply of oxygen to tissues that have become hypoxic, or suffered a loss of oxygen. Most often, this occurs after cells become injured or to repair muscle after exercise. However, VEGF expression can also result in the formation of new blood vessels to circumvent ones that are blocked, a process called collateral circulation. Overexpression of VEGF can lead to disease.

All parts of the body require oxygen to function, which is carried to the cells via blood vessels or the vascular supply. The heart and lungs require a great deal of oxygen, while other parts of the body, like bone, require less. However, bone can also cease to function without an adequate supply of oxygen. In an average long bone, oxygenated blood is supplied by either periosteal vessels, epiphyseal vessels, or a nutrient artery. By having three systems in place, one can take over the function of the other if it becomes blocked or damaged in some way. If bone tissue does not receive enough oxygen, a process known as avascular necrosis or osteonecrosis occurs. This is the death or decay of the bone due to a lack of oxygenated blood. Osteonecrosis can cause the bone to become brittle, breaking into small pieces and eventually crumbling or collapsing if left untreated.