The general ofjective of this project is to gain a better understanding of how the structure and mechanical propertied of lung tiddue, airways, and pulmonary blood vessels change under physical stress such as hypertension, or disease such as diabetes, and how do the changes affect the pressure and flow in the Lung.
The Specific Aims are: (1) To determine the zero-stress state of al generations of pulmonary blood vessels and airways, and their changes due to tissue remodeling in hypertension and other disease, and to correlate them with other markers of remodeling such as hypertrophy, cell proliferation, DNA content, and radioactive thymidine incorporation. (2) To determine the remodeling of the mechanical properties of different layers of pulmonary blood vessels and airways and pulmonary capillaries. (3) To distill the infformation obtained into constitutive equations describing the mechanical properties of the tissues, with coefficients depending on species, location, and disease states. (4) To use the remodeling data and constitutive equations to predict the pressure and flow distribution in the lung in pulmonary hypertension and diabetes, and to validate the theory with experiments. The point of departure of this study is our new discovery that at the zero-stress state the pulmonary artery is not an unloaded tube. If we take an artery, cut a short segment out, then cut the ring radially, it will spring open into a sector. An opening angle of the sector is defined as the angle between two radii joining the midpoint of the inner wall to the tips of the inner wall. This angle varies with the location on the vascular tree. In some parts it can be greater than 180 degrees. In the main pulmonary artery of the rat, it is often 360 degrees or larger; and it changes with the onset of hypertension and diseases. This opening angle reveals the zero-stress state of the vessel at which the different layers of the vessel (ensothelium, collagen and elastin layers, smooth muscle cells, adventitia) are put together without being deformed by residual stress. Any stress calculation must be based on the zero- stress state. We define strains from the zero-stress state, and use load-deformation relationship to determine the constitutive equations. With information on the remodeling of structure, materials, cellular growth, and mechanical properties, a theory to predict the changes in pressure-flow relationship will be formulated and validated with experiments.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL026647-14
Application #
2216016
Study Section
Respiratory and Applied Physiology Study Section (RAP)
Project Start
1981-05-01
Project End
1996-08-31
Budget Start
1994-09-30
Budget End
1996-08-31
Support Year
14
Fiscal Year
1994
Total Cost
Indirect Cost
Name
University of California San Diego
Department
Engineering (All Types)
Type
Schools of Arts and Sciences
DUNS #
077758407
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Li, Zhuangjie; Huang, Wei; Jiang, Zong Lai et al. (2004) Tissue remodeling of rat pulmonary arteries in recovery from hypoxic hypertension. Proc Natl Acad Sci U S A 101:11488-93
Li, Zhuang-Jie; Huang, Wei; Fung, Yuan-Cheng (2002) Changes of zero-bending-moment states and structures of rat arteries in response to a step lowering of the blood pressure. Ann Biomed Eng 30:379-91
Zhou, J; Fung, Y C (1997) The degree of nonlinearity and anisotropy of blood vessel elasticity. Proc Natl Acad Sci U S A 94:14255-60
Han, H C; Fung, Y C (1996) Direct measurement of transverse residual strains in aorta. Am J Physiol 270:H750-9
Liu, S Q; Fung, Y C (1996) Indicial functions of arterial remodeling in response to locally altered blood pressure. Am J Physiol 270:H1323-33
Debes, J C; Fung, Y C (1995) Biaxial mechanics of excised canine pulmonary arteries. Am J Physiol 269:H433-42
Fung, Y C; Liu, S Q (1995) Determination of the mechanical properties of the different layers of blood vessels in vivo. Proc Natl Acad Sci U S A 92:2169-73
Han, H C; Fung, Y C (1995) Longitudinal strain of canine and porcine aortas. J Biomech 28:637-41
Xie, J; Zhou, J; Fung, Y C (1995) Bending of blood vessel wall: stress-strain laws of the intima-media and adventitial layers. J Biomech Eng 117:136-45
Deng, S X; Tomioka, J; Debes, J C et al. (1994) New experiments on shear modulus of elasticity of arteries. Am J Physiol 266:H1-10

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