Atherosclerosis and the Recent Development of Artificial Blood Vessels
Abstract： For atherosclerosis patients, angioplasty procedures, including stents and bypass, are widely used, especially in China. However, in-stent restenosis has remained a clinical challenge. Fortunately, recent innovations in artificial vessel can potentially address the in-stent restenosis issue.
Cardiovascular disease is the leading cause of death in China and many other developed countries. In China, cardiovascular disease causes around 3.5 million deaths annually. Nearly two deaths out of five are due to cardiovascular disease and one adult out of five has cardiovascular disease. Atherosclerosis is the main cause of cardiovascular disease, with plaque building up inside big or middle-sized arteries, like carotid artery and coronary artery. With the progress of atherosclerosis, the lumen grows narrower, which may eventually cause total occlusion. Also, the components of atherosclerosis can be very fragile. Both occlusion and rupture of atherosclerosis can cause ischemia of heart, brain or extremities.
The current available treatments for patients with atherosclerosis including medicines, surgery and lifestyle changes. Medicines are widely prescribed for atherosclerosis treatment, to reduce cholesterol level (using medicines like statins) or to prevent clot.
However, atherosclerosis is a chronic disease, and when there are some symptoms, it often has already progressed to an advanced stage. When the plaque is very big or risky, the slowly effective drug can hardly help to reduce the risk immediately. In this case, surgery will be advised. Carotid endarterectomy is clinically used to remove plaque from the carotid arteries, by referring to stenosis severity and symptom criteria. For high-risk surgical patients, angioplasty procedures, including stents and bypass, are more widely used, especially in China. However, in-stent restenosis has remained a clinical challenge. Fortunately, recent innovations in artificial vessel can potentially address the in-stent restenosis issue.
Cutting-edge research on artificial vessels
Recently chemists from ITMO University in Russia developed a new type of clot-free artificial blood vessel coating. The coating contains dense nanorods made of aluminum oxide blended with a substance that activates a clot-busting enzyme. The coating has a porous structure which can hold the nanorods to react with plasminogen in the blood while keep it from reacting too fast. The clots-dissolving enzyme, therefore, can be generated. The proposed vessel works well in the lab test. The artificial clots were dissolved soon after being put into the vessel. As a matter of fact, the coating would destroy clots at their early stage. This innovation can potentially address the blood clots problem after vascular grafts and stents implantation.
This vessel belongs to the latest “drug-eluting” types of grafts and stents. They are normally coated with drugs that can be slowly released into the blood. However, the amount of drug stored often limits the lifetime of the grafts or stents. While for this new coating, thanks to the porous matrix structure, the lifetime is almost “unlimited”.
Research teams from Vienna University of Technology and Vienna Medical University have developed another new material for artificial blood vessels. The new material allows the artificial blood vessels to be replaced by endogenous material and finally become fully functional vessels.
In this work, Vienna University of Technology synthesized new polymers using the prepolymer method, the new material has satisfying biomechanics properties, and the by-products from its degradation are non-toxic. The polymer solutions were then “spun in an electrical field to form very fine threads and wound onto a spool”. The wall of the artificial vessels has similar properties as that naturally in the human body. One outstanding feature about the polymer fabric is that they are slightly porous, so that at the initial stage a small amount of blood is able to permeate through the wall of the artificial vessels, which could enhance the growth of the wall and also accelerate the migration of the endogenous cells. This new vessel has been applied successfully in rats. The replaced blood vessels in the rats were examined six moths after the insertion. No aneurysms, thromboses or inflammation were found. In all, they successfully fabricated biodegradable, porous grafts with very thin wall, as a small diameter vascular substitute.
Researchers from the University of California, San Diego School of Medicine developed an in vitro, live-cell artificial vessel, which can be used to study both the application and effects of devices used to extract blood clots in the brain. In this work, they perfused bovine artery ECs into optically clear, biocompatible tubular silicone with a thickness of 0.25 millimeters and inner diameters of 2.5, 3.5 and 4.5 millimeters. Then, they introduced porcine blood clots into the platform, allowing the clots to integrate, tested various clot-retrieval devices and examined the post-removal effects.
The results showed that the in vitro platform permitted high-resolution quantification and characterization of the pattern and timing of EC injury with various thrombectomy devices and vessel diameters. The devices each displayed different effects. Subsequently, animal in vivo studies confirmed the relevance of the platform, which suggests the artificial model could represent a practical, scalable and physiological alternative to existing technologies.
How to prevent atherosclerosis?
Though these innovations of artificial vessel can potentially provide better treatment to atherosclerosis patients, you may be wondering how to prevent atherosclerosis?
Atherosclerosis is progressive. The cause of atherosclerosis isn't clearly known. But it's also preventable.
Some risk factors such as certain traits, conditions, or habits may increase your risk for the disease. You should adopt a healthy lifestyle to lower the risk of it.
First, it is a very important part of healthy style that you follow a healthy diet. It includes all sorts of fruits, vegetables, whole grains, lean meats, seafood and low-fat-milk. Actually a healthy diet is low in refined grains, salt, sugar and solid fats.
The second, you should take exercises as possible as you can. Exercises can make your fitness level and your health improved.
The third, if you smoke, quit immediately. Smoking can tighten blood vessels and then raise your risk for atherosclerosis.
The last, you should take an action to record your family history of atherosclerosis. Be sure to tell your doctor, if your family members have an atherosclerosis-related disease. Take all of your medicines which can control your atherosclerosis risk factors as your doctor advises.
These healthy lifestyles won't remove blockage, however they are proven to reduce the risk of atherosclerosis.
 Hoyert, D.L. and J. Xu, Deaths: preliminary data for 2011. Natl Vital Stat Rep, 2012. 61(6): p. 1-65.
 Naghavi, M., et al., From vulnerable plaque to vulnerable patient: a call for new definitions and risk assessment strategies: Part I. Circulation, 2003. 108(14): p. 1664-72.
 Ross, R., Atherosclerosis--an inflammatory disease. N Engl J Med, 1999. 340(2): p. 115-26.
 Sarembock, I.J., Stent restenosis and the use of drug-eluting stents in patients with diabetes mellitus, Current Diabetes Reports, 2004, 4(1) p. 12-19