Quantitative Optical Imaging of Vascular Structure and Function in a Model of Peripheral Arterial Disease

Peripheral arterial disease (PAD) results in a failure to adequately supply blood and oxygen (O2) to working tissues and presents as claudication pain during walking. Nitric oxide (NO) bioavailability is essential for vascular health and function. Plasma nitrite (NO2−) is a marker of vascular NO production but may also be a protected circulating “source” that can be converted to NO during hypoxic conditions, possibly aiding perfusion. We hypothesized that dietary supplementation of inorganic nitrate in the form of beetroot (BR) juice would increase plasma NO2−concentration, increase exercise tolerance, and decrease gastrocnemius fractional O2extraction, compared with placebo (PL). This was a randomized, open-label, crossover study. At each visit, subjects ( n = 8) underwent resting blood draws, followed by consumption of 500 ml BR or PL and subsequent blood draws prior to, during, and following a maximal cardiopulmonary exercise (CPX) test. Gastrocnemius oxygenation during the CPX was measured by near-infrared spectroscopy. There were no changes from rest for [NO2−] (152 ± 72 nM) following PL. BR increased plasma [NO2−] after 3 h (943 ± 826 nM; P ≤ 0.01). Subjects walked 18% longer before the onset of claudication pain (183 ± 84 s vs. 215 ± 99 s; P ≤ 0.01) and had a 17% longer peak walking time (467 ± 223 s vs. 533 ± 233 s; P ≤ 0.05) following BR vs. PL. Gastrocnemius tissue fractional O2extraction was lower during exercise following BR (7.3 ± 6.2 vs. 10.4 ± 6.1 arbitrary units; P ≤ 0.01). Diastolic blood pressure was lower in the BR group at rest and during CPX testing ( P ≤ 0.05). These findings support the hypothesis that NO2−-related NO signaling increases peripheral tissue oxygenation in areas of hypoxia and increases exercise tolerance in PAD.

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Quantitative optical imaging of vascular response in vivo in a model of peripheral arterial disease

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00362.2013 ◽

2013 ◽

Vol 305 (8) ◽

pp. H1168-H1180 ◽

Cited By ~ 15

Author(s):

Kristin M. Poole ◽

Jason M. Tucker-Schwartz ◽

Wesley W. Sit ◽

Alex J. Walsh ◽

Craig L. Duvall ◽

...

Keyword(s):

Blood Flow ◽

Peripheral Arterial Disease ◽

Optical Imaging ◽

Hyperspectral Imaging ◽

Temporal Dynamics ◽

Arterial Disease ◽

Sensor Data ◽

Morphological Data ◽

Non Invasive ◽

Peripheral Arterial

The mouse hind limb ischemia (HLI) model is well established for studying collateral vessel formation and testing therapies for peripheral arterial disease, but there is a lack of quantitative techniques for intravitally analyzing blood vessel structure and function. To address this need, non-invasive, quantitative optical imaging techniques were developed to assess the time-course of recovery in the mouse HLI model. Hyperspectral imaging and optical coherence tomography (OCT) were used to non-invasively image hemoglobin oxygen saturation and microvessel morphology plus blood flow, respectively, in the anesthetized mouse after induction of HLI. Hyperspectral imaging detected significant increases in hemoglobin saturation in the ischemic paw as early as 3 days after femoral artery ligation ( P < 0.01), and significant increases in distal blood flow were first detected with OCT 14 days postsurgery ( P < 0.01). Intravital OCT images of the adductor muscle vasculature revealed corkscrew collateral vessels characteristic of the arteriogenic response to HLI. The hyperspectral imaging and OCT data significantly correlated with each other and with laser Doppler perfusion imaging (LDPI) and tissue oxygenation sensor data ( P < 0.01). However, OCT measurements acquired depth-resolved information and revealed more sustained flow deficits following surgery that may be masked by more superficial measurements (LDPI, hyperspectral imaging). Therefore, intravital OCT may provide a robust biomarker for the late stages of ischemic limb recovery. This work validates non-invasive acquisition of both functional and morphological data with hyperspectral imaging and OCT. Together, these techniques provide cardiovascular researchers an unprecedented and comprehensive view of the temporal dynamics of HLI recovery in living mice.

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Abstract 15850: Desmin Expression is Abnormal in Myofibers of the Gastrocnemius of Patients With Peripheral Arterial Disease and is Associated With Impaired Mitochondrial Respiration and Reduced Muscle Strength

Circulation ◽

10.1161/circ.130.suppl_2.15850 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Panagiotis Koutakis ◽

George P Casale ◽

Julian Kyung-So Kim ◽

Dimitrios Miserlis ◽

Zhen Zhu ◽

...

Keyword(s):

Muscle Strength ◽

Peripheral Arterial Disease ◽

Mitochondrial Respiration ◽

Force Production ◽

Arterial Disease ◽

Calf Muscle ◽

Gene Transcripts ◽

Peripheral Arterial ◽

And Function ◽

Muscle Force Production

Introduction: Patients with peripheral arterial disease (PAD) develop a myopathy in their ischemic limbs which is characterized by myofiber degeneration, mitochondrial dysfunction and decreased muscle force production. Desmin, a cytoskeletal protein of the myofiber, is central to maintenance of the structure, shape and function of the myofiber and its organelles especially the mitochondria. Hypothesis: We hypothesized that desmin expression in myofibers of the gastrocnemius of PAD patients is abnormal and correlates with decreased mitochondrial respiration and reduced muscle strength. Methods and Results: We quantified desmin protein and gene transcripts in myofibers of gastrocnemius biopsies from 30 PAD patients and 29 controls and determined their association with myofiber morphology, mitochondrial respiration and calf muscle strength. Compared to control, desmin protein and gene transcripts were increased in myofibers of PAD gastrocnemius. Increased expression was associated with a diffuse appearance of the protein, suggesting a loss of its normally filamentous structure. These changes in desmin correlated with altered myofiber morphology, decreased mitochondrial respiration and reduced calf muscle strength. Conclusions: Desmin expression and organization are abnormal in myofibers of the gastrocnemius of patients with PAD and these changes correlate with decreased mitochondrial function and reduced muscle strength.

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