Atherosclerosis, also known as hardening of the arteries, is a common vascular disease caused by the buildup of a waxy plaque on the inside of blood vessels. This narrowing of blood vessels can cause blood clots, leading to heart attack or stroke. In almost half of all heart transplant patients, an accelerated form of hardening of the arteries, known as Transplant Vascular Disease (TVD), occurs in the transplanted heart. In fact, TVD is a leading cause of death one year after transplantation. The exact mechanisms behind this process remain unclear. Blood vessels are lined with endothelial cells, specific cells that create a barrier between blood and the artery. An important factor in TVD is damage to endothelial cells. This damage increases the size of gaps between cells, allowing fats to accumulate in artery walls. One protein that causes endothelial ""leakiness"" is called Vascular Endothelial Growth Factor (VEGF). VEGF is also important in many other serious diseases, such as cancer and degenerative eye diseases. David Lin is expanding on previous research that showed that VEGF is increased in the muscle cells in arteries of transplanted hearts. He is studying in detail the mechanisms by which VEGF alters the function and structure of endothelial cells. By learning how VEGF works in transplanted hearts, Lin hopes his research will lead to the development of new ways to maintain the health of heart blood vessels following transplantation.