Coronary heart disease is a leading cause of morbidity and mortality. This disease results from blockage of coronary arteries that supply blood to the heart muscle. To restore blood supply, physicians use angioplasty to open the obstructed artery and apply stenting to maintain the arterial patency. Approximately 1.3 million angioplasty and stenting procedures are performed every year in the US to relieve coronary obstruction. However, these procedures activate a population of vascular cells to grow into the arterial lumen, causing re-narrowing of the artery. This re-narrowing (restenosis) is the major hurdle limiting the success of angioplasty and stenting. Mental stents coated with drug inhibitors of cell growth (drug eluting stents, or DES) reduce re-narrowing; however, considerable concerns have emerged regarding the safety of DES due to an increased risk of sudden stent occlusion by platelet aggregates (or thrombosis) and the need for prolonged anti-platelet therapy, which poses bleeding risks. These concerns call for defining mechanisms that control re-narrowing of injured arteries.
A population of stem cells resides in the arterial wall. These cells are activated when arteries are injured by mechanical stress such as angioplasty and stenting. Activation of these cells directly contributes to arterial re-narrowing. Our goal is to understand how these stem cells are activated by vessel injury, how injury signals these cells to divide and invade the vessel lumen, what molecular effectors control the cellular responses, and how to intercept these signals and effectors to prevent vessel re-narrowing. We developed new methods for isolating and growing these vascular stem cells in test tubes. In the past year, we successfully used these methods to determine how arterial injury or mechanical stress signals the stem cells to produce different types of cells which grow into the arterial lumen, causing narrowing of the artery. We are using these methods and also developing new methods to define molecular pathways that control the reaction of stem cells to arterial injury. This will help identify drug targets for therapeutic intervention.