Deciphering how arteries contribute to hypertension

National Insitute of Standards and Technology (NIST) scientists are taking their knowledge of mechanical tensile strength tests in metals and composites and applying it to medical research problems. Doctors long have known that babies born with congenital heart defects at higher altitudes have an increased risk of developing complications, such as pulmonary hypertension. Could there be some way to trick the arterial walls so that they wouldn’t stiffen under increased blood pressure?

Working with the Children’s Hospital and University of Colorado Health Sciences Center in Denver, NIST researchers have used rat arteries–both normal and hypertensive–supplied by the university center and placed them in a mechanical stress tester. The tester holds a small disc-shaped sample of the arterial tissue that is slowly stretched by pumping a special liquid against the back of the disc. The pressure of the liquid causes a bubble to form on the front of the disc. The shape of the resulting bubble helps the researchers determine details about the tissues’ elasticity, strength, stiffness and other properties.

” Hypertensive tissue should be stiffer, so we will get less inflation with the same amount of pressure,” says NIST researcher Elizabeth Drexler. “What we want to know is what it is in the artery that causes it to stiffen. Is it more collagen? Is it the smooth muscle cells? Perhaps we could give the muscle cell a signal not to produce more collagen.” So far they have studied 20 rat arteries and plan to study 20 more, along with some calf arteries. A preliminary report that verifies their test method appears in the May/June issue of the NIST Journal of Research.