Name: assessment of vascular function in patients with chronic kidney disease
Uploaded: 2014-06-16T14:00:00
Description: Watch this Scientific Journal Video about Assessment of Vascular Function in Patients With Chronic Kidney Disease at JoVE.com

The authors thank Nina Bispham for her technical assistance. This work was supported by the American Heart Association (12POST11920023), and the NIH (K23DK088833, K23DK087859).

This protocol follows the guidelines of the Colorado Multiple Institutional Review Board (COMIRB).
1. Preparation for Testing Session
<ol>
	<li>Participants should follow these restrictions for most accurate measurements: 12 hr fast from food and caffeine, 12 hr restraint from exercise, 12 hr restraint from smoking, if applicable, &#62;4 half-life restraint from medications if possible (may not be feasible in a population such as CKD patients), and pre-menopausal women should be teste...

Obtaining accurate results for FMDBA and aPWV requires acquiring high quality ultrasound images and pressure waveforms, respectively. Central to this is appropriate and continued training and use of each technique by the operator44. In addition, it is critical to control for as many external variables that may influence the results as possible by standardizing the testing session (e.g.,&#160;prior 12 hr fast, climate controlled room, etc.)44,45. As mentioned above, the u...

Chronic kidney disease (CKD) is a major public health concern that has reached epidemic proportions, affecting ~11.5% of the population in the United States alone1. The risk of cardiovascular death or a cardiovascular event in patients with CKD is significantly increased compared with the general population2-4. Although patients with CKD exhibit a high prevalence of traditional cardiovascular risk factors, this only explains part of their increased incidence of cardiovascular disease (CVD)5. Vascular dysfunction is an important nontraditional cardiovascular risk factor gaining increased recognition in the field of nephrology6-9.
While many changes likely contribute to the development of arterial dysfunction, among those of greatest concern are the development of vascular endothelial dysfunction, most commonly assessed as impaired endothelium-dependent dilation (EDD), and stiffening of the large elastic arteries10. Various techniques exist to assess EDD and large elastic artery stiffness, but the most commonly used are brachial artery flow-mediated dilation FMDBA and aortic pulse-wave velocity (aPWV), respectively. Another commonly used technique to assess EDD is measuring forearm blood flow response to pharmacological agents such as acetylcholine using venous occlusion plethysmography11,12. However, this methodology requires catheterization of the brachial artery, which is more invasive than FMDBA and may be contraindicated in patients with CKD. An alternate technique to assess arterial stiffness is to measure the local arterial compliance (the inverse of stiffness) of the carotid artery, although this is not as widely used or validated with clinical endpoints as aPWV13 .
Patients with CKD demonstrate both impaired FMDBA14-16 and increased aortic pulse-wave velocity aPWV13,17,18, even prior to needing dialysis. Importantly from a clinical perspective, both of these noninvasive measures of vascular dysfunction are independent predictors of future cardiovascular events and mortality both in patients with CKD19-21, as well as in other populations22-26. These techniques can be applied to studying various populations at risk of CVD, including patients with CKD.
The exact mechanisms by which arterial dysfunction develops in CKD are incompletely understood; however, reduced nitric oxide (NO) bioavailability is a critical contributor27-30 and a common mechanism of both impaired EDD and increased arterial stiffness10,31. In CKD, oxidative stress is increased and contributes to the reduction in NO bioavailability32-34. Oxidative stress is defined as excessive bioavailability of reactive oxygen species (ROS) relative to antioxidant defenses. Physiological stimuli, including inflammatory signaling, promote oxidant enzyme systems (e.g., the oxidant enzyme NADPH oxidase) to produce ROS, including superoxide anion (O2&#9679;-)35. Production of superoxide ultimately leads to reduces bioavailability of nitric oxide (NO).
Impaired NO bioavailability may in turn contribute to the development of CKD, as endothelial dysfunction is an independent predictor of incident CKD36. This is consistent with animal data indicating that eNOS inhibition induces hypertension (systemic and glomerular), glomerular ischemia, glomerulosclerosis, and tubulo-interstitial injury37. Indeed, reduced NO bioavailability appears necessary for the development and progression of experimental kidney disease that mimics human disease, suggesting a key role for endothelial dysfunction in human CKD38,39.
Markers of vascular oxidative stress can be assessed in vascular endothelial cells collected from human research subjects, using a technique originally developed by Colombo et al.40 and modified Seals et al41-43. Using 2 sterile J-wires, cells are collected from the antecubital vein, recovered, fixed, and later positively identified as endothelial cells and analyzed for expression of proteins of interest using immunofluorescence.
We provide here a discussion of this methodology that can be used to a) measure FMDBA; b) measure aPWV; c) measure vascular endothelial cell protein expression of markers of oxidative stress. The focus is on patients with CKD, not requiring chronic dialysis.

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			<td height="42" style="height:42px;width:216px;">Name of Material/ Equipment</td>
			<td style="width:109px;">Company</td>
			<td style="width:244px;">Catalog Number</td>
			<td style="width:167px;">Comments/Description</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:216px;">J-wire</td>
			<td style="width:109px;">St. Jude</td>
			<td style="width:244px;">404584</td>
			<td>2 per collection</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Disposable shorts (MediShorts)</td>
			<td>Quick Medical&#160;</td>
			<td>4507</td>
			<td></td>
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		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Non-invasive hemodynamic workstation (NIHem)</td>
			<td style="width:109px;">Cardiovascualr Engineering</td>
			<td style="width:244px;">N/A</td>
			<td>Includes custom ruler.&#160; An alternate system is the Sphygmocor</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Ultrasound</td>
			<td style="width:109px;">G.E.</td>
			<td>Model: Vivid7 Dimension</td>
			<td>We use a G.E., but there are many companies and models</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Vascular software (Vascular Imager)&#160;</td>
			<td style="width:109px;">Medical Imaging Applications</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">R-wave trigger box</td>
			<td style="width:109px;">Medical Imaging Applications</td>
			<td>N/A</td>
			<td>custom made</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Rapid Cuff Inflation System</td>
			<td style="width:109px;">Hokanson</td>
			<td style="width:244px;">Model: Hokanson E20</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Forearm blood pressure cuff</td>
			<td style="width:109px;">Hokanson</td>
			<td style="width:244px;">N/A</td>
			<td>custom cuff with 6.5 x 34 cm bladder&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">HUVECs</td>
			<td style="width:109px;">Invitrogren&#160;</td>
			<td>C-015-5C</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Donkey serum</td>
			<td style="width:109px;">Jackson&#160;</td>
			<td>017-000-121</td>
			<td></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Pap pen</td>
			<td style="width:109px;">Research Products International</td>
			<td>195505</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">VE Cadherin</td>
			<td style="width:109px;">Abcam</td>
			<td style="width:244px;">ab33168</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">AF568</td>
			<td style="width:109px;">Life Technologies</td>
			<td>A11011</td>
			<td>depends on specifications of microscpe&#160;</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">AF488</td>
			<td style="width:109px;">Life Technologies</td>
			<td>A11034</td>
			<td>depends on specifications of microscpe&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Nitrotyrosine antibody&#160;</td>
			<td style="width:109px;">Abcam</td>
			<td>ab7048</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">NADPH oxidase antibody</td>
			<td>Upstate</td>
			<td>07-001</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">DAPI&#160;</td>
			<td style="width:109px;">Vector</td>
			<td style="width:244px;">H-1200</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Delicate task wipe (Kimwipe)&#160;</td>
			<td style="width:109px;">Fisher Scientific</td>
			<td>06-666-A&#160;</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Plastic paraffin film (parafilm)&#160;</td>
			<td style="width:109px;">Fisher Scientific</td>
			<td>13-374-10</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Confocal microscope&#160;</td>
			<td style="width:109px;">Olympus&#160;</td>
			<td>Model: FV1000 FCS/RICS</td>
			<td>many options exist&#160;</td>
		</tr>
	</tbody>
</table>

assessment of vascular function in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) have significantly increased risk of cardiovascular disease (CVD) compared to the general population, and this is only partially explained by traditional CVD risk factors. Vascular dysfunction is an important non-traditional risk factor, characterized by vascular endothelial dysfunction (most commonly assessed as impaired endothelium-dependent dilation [EDD]) and stiffening of the large elastic arteries. While various techniques exist to assess EDD and large elastic artery stiffness, the most commonly used are brachial artery flow-mediated dilation (FMDBA) and aortic pulse-wave velocity (aPWV), respectively. Both of these noninvasive measures of vascular dysfunction are independent predictors of future cardiovascular events in patients with and without kidney disease. Patients with CKD demonstrate both impaired FMDBA, and increased aPWV. While the exact mechanisms by which vascular dysfunction develops in CKD are incompletely understood, increased oxidative stress and a subsequent reduction in nitric oxide (NO) bioavailability are important contributors. Cellular changes in oxidative stress can be assessed by collecting vascular endothelial cells from the antecubital vein and measuring protein expression of markers of oxidative stress using immunofluorescence. We provide here a discussion of these methods to measure FMDBA, aPWV, and vascular endothelial cell protein expression.

FMDBA is quantified as the peak change in diameter of the brachial artery following reactive hyperemia. Thus, the diameter at rest is compared to the diameter following the end of a 5 min blood pressure cuff occlusion period (Figure 1). Panel A shows a representative ultrasound image of the brachial artery, and Panel B displays a graph of the R-wave gated change in diameter from cuff release to 2 min following, as obtained using commercially available software. As the change is often quite min...

Watch this Scientific Journal Video about Assessment of Vascular Function in Patients With Chronic Kidney Disease at JoVE.com

Assessment of Vascular Function in Patients With Chronic Kidney Disease

The degree of vascular dysfunction and contributing physiological mechanisms can be assessed in patients with chronic kidney disease by measuring brachial artery flow-mediated dilation, aortic pulse-wave velocity, and vascular endothelial cell protein expression.

Patients with chronic kidney disease (CKD) have significantly increased risk of cardiovascular disease (CVD) compared to the general population, and this ...

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