Hypoxic pulmonary hypertension (HPH) leads to stiffening of large pulmonary arteries, which affects right ventricular afterload. We hypothesized that vascular collagen accumulation is the major cause of large pulmonary artery (PA) stiffening in HPH. We tested this hypothesis with transgenic mice that produce collagen type I resistant to degradation (Col1a1R/R) and wild type littermate controls (Col1a1+/+) exposed to hypoxia and allowed to recover. Pressure-diameter testing on left PAs demonstrated that stiffness in control mice increased with hypoxia and decreased with recovery (p < 0.05). Preliminary tests in degradation-resistant mice suggest that PA stiffness decreases less with recovery than in controls. Quantitative measurements of vascular collagen content in right PAs are planned to develop statistical correlations between structure and function.

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