Quantitative optical imaging of vascular structure and function in a model of peripheral arterial disease
Poole, Kristin Marie
Peripheral arterial disease (PAD) leads to an increased risk of myocardial infarction and stroke, increased mortality, and reduced quality of life. The mouse hind limb ischemia (HLI) model is the most commonly used system for studying the mechanisms of collateral vessel formation and for testing new PAD therapies, but there is a lack of techniques for acquiring physiologically-relevant, quantitative data intravitally in this model. In this work, non-invasive, quantitative optical imaging techniques were applied to the mouse HLI model over a time course. Quantification of hemoglobin oxygen saturation with hyperspectral imaging was sensitive to changes in the oxygenation of the ischemic hind limb. Hemoglobin oxygen saturation measurements also correlated well with two standard measures of hind limb recovery: the perfusion ratio and probe-based tissue oxygen tension. Additionally, optical coherence tomography (OCT) techniques were applied to study changes in blood flow with high resolution. Restoration of blood flow in vessels distal to the site of occlusion was monitored non-invasively with Doppler OCT. Three dimensional images of the adductor muscle acquired with Doppler OCT revealed changes in collateral vessel morphology consistent with post-mortem analyses in previous studies. This visualization of hind limb vasculature in a given mouse over time without contrast agents or post-mortem methods was previously unattainable. Taken together, hyperspectral imaging and OCT enable acquisition of both functional and morphological data which fill the gaps in acquiring a complete picture of recovery in the mouse HLI model. Therefore, these optical imaging methods hold promise as tools for studying the mechanisms of vascular recovery and evaluating novel therapeutic treatments in preclinical studies.