Persistent vascular collagen accumulation alters hemodynamic recovery from chronic hypoxia

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• 作者：Diana M. Tabima^a ; Alejandro Roldan-Alzate^a ; Zhijie Wang^a ; Timothy A. Hacker^b ; Robert C. Molthen^c ; Naomi C. Chesler^a ; ^b ; ^{chesler@engr.wisc.edu}
• 关键词：Pulmonary hemodynamics ; Pulmonary hypertension ; Pulmonary vascular impedance ; Pulmonary artery stiffness ; Collagen
• 刊名：Journal of Biomechanics
• 出版年：2012
• 期刊代码：144_00219290
• 类别：med
• 出版时间：15 March, 2012
• 卷：45
• 期：5
• 页码：799-804
• 文件大小：324 K

摘要

Pulmonary arterial hypertension (PAH) is caused by narrowing and stiffening of the pulmonary arteries that increase pulmonary vascular impedance (PVZ). In particular, small arteries narrow and large arteries stiffen. Large pulmonary artery (PA) stiffness is the best current predictor of mortality from PAH. We have previously shown that collagen accumulation leads to extralobar PA stiffening at high strain (). We hypothesized that collagen accumulation would increase PVZ, including total pulmonary vascular resistance (Z₀), characteristic impedance (Z_C), pulse wave velocity (PWV) and index of global wave reflections (P_b/P_f), which contribute to increased right ventricular afterload. We tested this hypothesis by exposing mice unable to degrade type I collagen (Col1a1^R/R) to 21 days of hypoxia (hypoxia), some of which were allowed to recover for 42 days (recovery). Littermate wild-type mice (Col1a1^+/+) were used as controls. In response to hypoxia, mean PA pressure (mPAP) increased in both mouse genotypes with no changes in cardiac output (CO) or PA inner diameter (ID); as a consequence, Z₀ (mPAP/CO) increased by 鈭?00%in both genotypes (p<0.05). Contrary to our expectations, Z_C, PWV and P_b/P_f did not change. However, with recovery, Z_C and PWV decreased in the Col1a1^+/+ mice and remained unchanged in the Col1a1^R/R mice. Z₀ decreased with recovery in both genotypes. Microcomputed tomography measurements of large PAs did not show evidence of stiffness changes as a function of hypoxia exposure or genotype. We conclude that hypoxia-induced PA collagen accumulation does not affect the pulsatile components of pulmonary hemodynamics but that excessive collagen accumulation does prevent normal hemodynamic recovery, which may have important consequences for right ventricular function.