MicroCT analysis of vascular morphometry: a comparison of right lung lobes in the SUGEN/hypoxic rat model of pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a rare disease characterized by significant vascular remodeling within the lung. Clinical computed tomography (CT) scans are routinely used to aid in PAH diagnosis. Animal models, including the Sugen-hypoxic rat model (SU/hyp), of PAH closely mimic human PAH development. We have previously used micro-computed tomography (microCT) to find extensive right lung vascular remodeling in the SU/hyp. We hypothesized that the individual right lung lobes may not contribute equally to overall lung vascular remodeling. Sprague-Dawley rats were subjected to a subcutaneous injection of vascular endothelial growth factor receptor blocker (Sugen 5416) and subsequently exposed to chronic hypoxic conditions (10% O2) for three weeks. Following perfusion of the lung vasculature with an opaque resin (Microfil), the right lung lobes were microCT-imaged with a 10-µm voxel resolution and 3D morphometry analysis was performed separately on each lobe. As expected, we found a significantly lower ratio of vascular volume to total lobe volume in the SU/hyp compared with the control, but only in the distal lobes (inferior: 0.23 [0.21-0.30] versus 0.35 [0.27-0.43], P = 0.02; accessory: 0.27 [0.25-0.33] versus 0.37 [0.29-0.43], P = 0.06). Overall, we observed significantly fewer continuous blood vessels and reduced vascular density while having greater vascular lumen diameters in the distal lobes of both groups ( P < 0.05). In addition, the vascular separation within the SU/hyp lobes and the vascular surface area to volume ratio were significantly greater in the SU/hyp lobes compared with controls ( P < 0.03). Results for the examined parameters support the overall extensive vascular remodeling in the SU/hyp model and suggest this may be lobe-dependent.