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% O 2 ) 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.