This work was supported by Grant Award Numbers R01HL096593 and K23HL72825 from the National Heart, Lung, and Blood Institute. The content is solely the responsibility of Thomas Jefferson University and does not necessarily represent the official views of the National Heart, Lung, and Blood Institute or the National Institutes of Health.

Case Presentation (required, if applicable): N.A.; this is still an experimental research procedure, not yet used clinically.
Diagnosis, Assessment, and Plan (required, if applicable): N.A.; this is still an experimental research procedure, not yet used clinically.
Procedure (required): This part should include a step-by-step description of relevant procedures, meeting the guidelines below.
1. Capillary Microscopy (Figure 1)
<ol>
 <li>Our capillaroscopy technique was adapted from Serne and his colleagues 1. An exclusion criterion for this procedure is collagen vascular disease, since collagen vascular disease produces known capillary changes 2.</li>
 <li>Following a minimum 10-hr overnight fast and 20 min of seated rest, microvascular measurements are conducted for one half-hour between 7 and 11 am, in a quiet, temperature controlled room (maintained between 21.5-22.5 &deg;C), with the subject in the seated position and the left hand at heart level.</li>
 <li>Nailfold capillaries in the dorsal skin of the third finger are visualized using a stereomicroscope (Olympus; Center Valley, PA), linked to a 4 megapixel SPOT Insight monochrome digital camera (Model number IN-1400: Diagnostic Instruments; Sterling Heights, MI), and a laptop computer (Dell Latitude D600: Dell; Austin, TX). To limit movement, the left hand and forearm are loosely covered with a folded blanket, and rested on another folded blanket positioned at the base of the microscope.</li>
 <li>Nailbed illumination is achieved with a 250-W halogen fiber optic lamp (KL 2500LCD:Schott-Fostec; Elmsford, NY); additional illumination from a supplemental 150W fiber optic halogen light source (B&amp;B Microscopes, Ltd., Warrendale, PA) is used in darkly pigmented individuals.</li>
 <li>To visualize the capillaries, the 3.2x objective (Olympus 3.2/0.07) is used with a total system magnification of 38.4x.</li>
 <li>Using SPOT imaging software provided with the camera, light/dark contrast in the capillary photographs is enhanced using the same standard SPOT software function (stretching of bright and dark levels) to maximize visibility of the capillaries in all subjects.</li>
 <li>To quantify capillary density, digital photomicrographs are taken every 3-5 sec during each of three stages, at resting baseline, during postocclusive reactive hyperemia, and during venous occlusion. (a) At resting baseline, photomicrographs are taken over a three-minute period to detect capillaries perfused at rest. (b) During postocclusive reactive hyperemia, photomicrographs are taken to quantify functionally perfused capillaries (baseline plus reserve capillaries), as follows. First, an occlusion cuff on the left upper arm is inflated to 40 mm Hg above systolic pressure for 10 min. Photomicrographs are then taken during the first minute immediately following release of arterial occlusion, visualizing all functionally perfused capillaries. Lower capillary density following reactive hyperemia indicates impaired functional capillary recruitment, and therefore functional rarefaction. (c) During venous occlusion photomicrographs are taken to quantify maximal capillary density, which includes both perfused (with active red blood cell (RBC) motion) and nonperfused (filled with stagnant, non-moving RBCs) capillaries 3 as follows. Following ten minutes of rest after the postocclusive reactive hyperemia procedure, the arm cuff is inflated to 60 mm Hg for 60 sec, passively forcing blood into all patent capillaries present and photomicrographs were taken during this time. Since maximal capillary density includes all capillaries structurally present, a reduction in maximal capillary density indicates structural rarefaction.</li>
 <li>Capillary density is defined as the number of capillaries per square millimeter of nailfold skin, and is computed as the mean of four measurements obtained from the four most clearly focused images, least distorted by movement. In our studies, typical values for capillary counts (capillaries/mm2) have been 55-80 for baseline, 65-90 for post-ischemic, and 90-105 for venous occlusion. Values for percent capillary recruitment are typically between 5% and 25% (mean ~10-15%) and for percent perfused capillaries between 70% and 95% (mean ~80-90%), with values being lower among hypertensives than normotensives. The reproducibility of the counting procedure has been verified with three observers who performed independent manual assessments of photographs of 10 different subjects (Figure 2). The observers were blinded to the identity and blood pressure of these subjects. Following training, subsequent counts performed independently showed a high level of agreement. Average inter-rater and intra-rater discrepancies were of the order of 2-3 capillaries/mm2, and intraclass correlation coefficients were all greater than 0.90. Short-term variation of the capillaroscopy measures were of the same order of magnitude as inter-rater and intra-rater discrepancies (approximately 2 capillaries/mm2), but longer-term variation observed over 2-3 years was an order of magnitude larger (approximately 15 capillaries/mm2), indicating that longitudinal changes can be readily distinguished from rater variation. Reliability of the two capillary function measures was also high (intraclass correlation coefficient = 0.84 for percent capillary recruitment and 0.82 for percent perfused capillaries).</li>
 <li>
 The investigators now utilize a computer-based method for quantifying capillary density using Image-Pro Plus imaging software (Version 6.2, Media Cybernetics, Inc., Bethesda, MD: Figure 3). Pearson correlations between baseline, post-ischemic, and venous congestion counts done with the software and corresponding manual counts in 10 subjects were 0.78, 0.78, and 0.71 respectively (all p &lt; 0.05), indicating reasonable agreement between the two methods. Reliability of the computer-based counts is slightly lower than that of manual counts but still high (intraclass correlation coefficient = 0.91 for baseline, 0.86 for post-ischemic, and 0.84 for venous occlusion). We have unpublished data also demonstrating the association of automated counts with multiple cardiovascular risk factors including hypertension, which we are currently preparing for publication.</li>
 <li>Table 1 summarizes the capillary density measurements and calculations. Percent capillary recruitment is assessed by dividing the increase in capillary density induced by postocclusive reactive hyperemia (postocclusive reactive hyperemia capillary density minus baseline capillary density), by the maximal capillary density (observed during passive venous occlusion). Percent perfused capillaries represents the proportion of all capillaries present that are perfused (functionally active), and is calculated by dividing postocclusive reactive hyperemia capillary density by the maximal capillary density. Both percent capillary recruitment and percent perfused capillaries reflect the number of functional capillaries. Lower values for these measures indicate functional capillary rarefaction.</li>
</ol>
2. Endothelial Function Assessment
<ol>
 <li>Endothelial function is assessed before and after postocclusive reactive hyperemia, using non-invasive plethysmography measurements of forearm blood flow, according to the method of Sivertsson,4 which utilizes the endothelium-dependent stimulus of reactive hyperemia to induce vasodilation.</li>
 <li>With the subject in the seated position following 10 min of supine rest, a mercury-in rubber strain gauge stretched to 10% beyond its resting length is looped around the subject's forearm 5 cm below the antecubital fossa.</li>
 <li>The strain-gauge is connected to a plethysmograph (EC-4: DE Hokanson, Inc; Bellevue, WA), which in turn is connected to a Doppler recorder (CW-1; DE Hokanson, Inc; Belleveue, WA).</li>
 <li>An upper arm occlusion cuff is applied, and the arm is suspended comfortably at heart level using a sling bandage connected to an adjustable intravenous pole. Systolic and diastolic blood pressures and heart rate are obtained with a Dinamap ProCare 100 automatic BP cuff (GE Healthcare, Piscataway, NJ) placed on the opposite arm.</li>
 <li>A pediatric cuff around the wrist is inflated to 200 mm Hg to occlude flow to the hand. The upper arm cuff is inflated to 50 mm Hg, deflated for 1.5 sec, and then re-inflated rapidly prior to each forearm blood flow measurement, obtained through expansion of the strain gauge placed around the forearm.</li>
 <li>Forearm blood flow (FBF) is measured at rested baseline (FBFbase) and again at postocclusive hyperemia-induced maximal vasodilation (FBFmax). For baseline blood flow measurements, four consecutive FBF curves are obtained within 30 sec (FBFbase).</li>
 <li>The occlusion cuff is then inflated to 40 mm Hg above systolic pressure for 10 min. Following release of arterial occlusion (postocclusive reactive hyperemia), four consecutive FBF curves are obtained within the first 30 sec of flow (FBFmax).</li>
 <li>The ratio FBFmax/FBFbase is computed as an estimate of vasodilation, by dividing the mean of the four FBFmax values by the mean of the four FBFbase values.5 Forearm vascular resistance at maximal vasodilation (FVRmax) is calculated as the mean arterial pressure (MAP) divided by FBFmax. FBFmaxduring reactive hyperemia is directly related to FBF after maximum infusion of intra-arterial acetylcholine, an endothelial-dependent vasodilator.6 Accordingly, FBFmax and the ratio FBFmax/FBFbase are accepted non-invasive measures of endothelial function.6-8 In addition, both FBFmax and FVRmax reflect resistance artery structural changes(increased wall/lumen ratio).9</li>
</ol>

<ol>
	<li>Serne, E. H., Gans, R. O., ter Maaten, J. C., ter Wee, P. M., Donker, A. J., Stehouwer, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Capillary+recruitment+is+impaired+in+essential+hypertension+and+relates+to+insulin's+metabolic+and+vascular+actions.">Capillary recruitment is impaired in essential hypertension and relates to insulin's metabolic and vascular actions.</a> Cardiovasc. Res. 49, 161-168 (2001).</li><li>Bollinger, A., Fagrell, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Clinical Capillaroscopy: A guide to its use in clinical research and practice. , (1990).</li><li>Antonios, T. F., Rattray, F. E., Singer, D. R., Markandu, N. D., Mortimer, P. S., MacGregor, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maximization+of+skin+capillaries+during+intravital+video-microscopy+in+essential+hypertension:+comparison+between+venous+congestion,+reactive+hyperaemia+and+core+heat+load+tests.">Maximization of skin capillaries during intravital video-microscopy in essential hypertension: comparison between venous congestion, reactive hyperaemia and core heat load tests.</a> Clin. Sci. (Lond). 97, 523-528 (1999).</li><li>Sivertsson, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+hemodynamic+importance+of+structural+vascular+changes+in+essential+hypertension.">The hemodynamic importance of structural vascular changes in essential hypertension.</a> Acta. Physiol. Scand. Suppl. 343, 1-56 (1970).</li><li>Raitakari, O. T., Celermajer, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Testing+for+endothelial+dysfunction.">Testing for endothelial dysfunction.</a> Ann. Med. 32, 293-304 (2000).</li><li>Tousoulis, D., Antoniades, C., Stefanadis, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluating+endothelial+function+in+humans:+a+guide+to+invasive+and+non-invasive+techniques.">Evaluating endothelial function in humans: a guide to invasive and non-invasive techniques.</a> Heart. 91, 553-558 (2005).</li><li>Higashi, Y., Sasaki, S., Nakagawa, K., Matsuura, H., Kajiyama, G., Oshima, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+noninvasive+measurement+of+reactive+hyperemia+that+can+be+used+to+assess+resistance+artery+endothelial+function+in+humans.">A noninvasive measurement of reactive hyperemia that can be used to assess resistance artery endothelial function in humans.</a> Am. J. Cardiol. 87, 121-125 (2001).</li><li>Higashi, Y., Yoshizumi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+methods+to+evaluate+endothelial+function:+method+for+assessingendothelial+function+in+humans+using+a+strain-gauge+plethysmography:+nitric+oxide-dependent+and+independent+vasodilation.">New methods to evaluate endothelial function: method for assessingendothelial function in humans using a strain-gauge plethysmography: nitric oxide-dependent and independent vasodilation.</a> J. Pharmacol. Sci. 93, 399-404 (2003).</li><li>Lind, L., Sarabi, M., Millgard, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methodological+aspects+of+the+evaluation+of+endothelium+dependent+vasodilatation+in+the+human+forearm.">Methodological aspects of the evaluation of endothelium dependent vasodilatation in the human forearm.</a> Clin. Physiol. 18, 81-87 (1998).</li><li>Cheng, C., Diamond, J. J., Falkner, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+capillary+rarefaction+in+mild+blood+pressure+elevation.">Functional capillary rarefaction in mild blood pressure elevation.</a> Clinical and Translational Science. 1, 75-79 (2008).</li><li>Cheng, C., Daskalakis, C., Falkner, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Capillary+rarefaction+in+treated+and+untreated+hypertensive+subjects.">Capillary rarefaction in treated and untreated hypertensive subjects.</a> Therapeutic Advances in Cardiovascular Disease. 2, 79-88 (2008).</li><li>Antonios, T. F., Singer, D. R., Markandu, N. D., Mortimer, P. S., MacGregor, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rarefaction+of+skin+capillaries+in+borderline+essential+hypertension+suggests+an+early+structural+abnormality.">Rarefaction of skin capillaries in borderline essential hypertension suggests an early structural abnormality.</a> Hypertension. 34, 655-658 (1999).</li><li>Noon, J. P., Walker, B. R., Webb, D. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impaired+microvascular+dilatation+and+capillary+rarefaction+in+young+adults+with+a+predisposition+to+high+blood+pressure.">Impaired microvascular dilatation and capillary rarefaction in young adults with a predisposition to high blood pressure.</a> J. Clin. Invest. 99, 1873-1879 (1997).</li><li>Antonios, T. F., Rattray, F. M., Singer, D. R., Markandu, N. D., Mortimer, P. S., MacGregor, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rarefaction+of+skin+capillaries+in+normotensive+offspring+of+individuals+with+essential+hypertension.">Rarefaction of skin capillaries in normotensive offspring of individuals with essential hypertension.</a> Heart. 89, 175-178 (2003).</li><li>de Jongh, R. T., Ijzerman, R. G., Serne, E. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visceral+and+truncal+subcutaneous+adipose+tissue+are+associated+with+impaired+capillary+recruitment+in+healthy+individuals.">Visceral and truncal subcutaneous adipose tissue are associated with impaired capillary recruitment in healthy individuals.</a> J. Clin. Endocrinol. Metab. 91, 5100-5106 (2006).</li><li>de Jongh, R. T., Serne, E. H., Ijzerman, R. G., de Vries, G., Stehouwer, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Free+fatty+acid+levels+modulate+microvascular+function:+relevance+for+obesity-associated+insulin+resistance,+hypertension,+and+microangiopathy.">Free fatty acid levels modulate microvascular function: relevance for obesity-associated insulin resistance, hypertension, and microangiopathy.</a> Diabetes. 53, 2873-2882 (2004).</li><li>de Jongh, R. T., Serne, E. H., RG, I. J., Stehouwer, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microvascular+function:+a+potential+link+betweensalt+sensitivity,+insulin+resistance+and+hypertension.">Microvascular function: a potential link betweensalt sensitivity, insulin resistance and hypertension.</a> J. Hypertens. 25, 1887-1893 (2007).</li><li>Ijzerman, R. G., Voordouw, J. J., Van Weissenbruch, M. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TNF-alpha+levels+are+associated+withskin+capillary+recruitment+in+humans:+a+potential+explanation+for+the+relationship+between+TNF-alpha+and+insulin+resistance.">TNF-alpha levels are associated withskin capillary recruitment in humans: a potential explanation for the relationship between TNF-alpha and insulin resistance.</a> Clin. Sci. (Lond). 110, 361-368 (2006).</li><li>Yvonne-Tee, G. B., Rasool, A. H., Halim, A. S., Rahman, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Noninvasive+assessment+of+cutaneous+vascular+function+in+vivo+using+capillaroscopy,+plethysmography+and+laser-Doppler+instruments:+its+strengths+and+weaknesses.">Noninvasive assessment of cutaneous vascular function in vivo using capillaroscopy, plethysmography and laser-Doppler instruments: its strengths and weaknesses.</a> Clin. Hemorheol. Microcirc. 34, 457-473 (2006).</li><li>Wilkinson, I. B., Webb, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Venous+occlusion+plethysmography+in+cardiovascular+research:+methodology+and+clinical+applications.">Venous occlusion plethysmography in cardiovascular research: methodology and clinical applications.</a> Br. J. Clin. Pharmacol. 52, 631-646 (2001).</li><li>Thijssen, D. H., Bleeker, M. W., Smits, P., Hopman, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reproducibility+of+blood+flow+and+post-occlusive+reactive+hyperaemia+as+measured+by+venous+occlusion+plethysmography.">Reproducibility of blood flow and post-occlusive reactive hyperaemia as measured by venous occlusion plethysmography.</a> Clin. Sci. (Lond). 108, 151-157 (2005).</li><li>Leslie, S. J., Attina, T., Hultsch, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+two+plethysmography+systems+in+assessment+of+forearm+blood+flow.">Comparison of two plethysmography systems in assessment of forearm blood flow.</a> J. Appl. Physiol. 96, 1794-179 (2004).</li><li>James, M. A., Tullett, J., Hemsley, A. G., Shore, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+aging+and+hypertension+on+the+microcirculation.">Effects of aging and hypertension on the microcirculation.</a> Hypertension. 47, 968-9674 (2006).</li><li>Debbabi, H., Uzan, L., Mourad, J. J., Safar, M., Levy, B. I., Tibirica, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+skin+capillary+density+in+treated+essential+hypertensive+patients.">Increased skin capillary density in treated essential hypertensive patients.</a> Am. J. Hypertens. 19, 477-483 (2006).</li><li>Serne, E. H., Gans, R. O., ter Maaten, J. C., Tangelder, G. J., Donker, A. J., Stehouwer, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impaired+skincapillary+recruitment+in+essential+hypertension+is+caused+by+both+functional+and+structural+capillary+rarefaction.">Impaired skincapillary recruitment in essential hypertension is caused by both functional and structural capillary rarefaction.</a> Hypertension. 38, 238-242 (2001).</li><li>Carpentier, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+techniques+for+clinical+assessment+of+the+peripheral+microcirculation.">New techniques for clinical assessment of the peripheral microcirculation.</a> Drugs. 58, 17-22 (2001).</li><li>Shore, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Capillaroscopy+and+the+measurement+of+capillary+pressure.">Capillaroscopy and the measurement of capillary pressure.</a> Br. J. Clin. Pharmacol. 50, 501-513 (2000).</li></ol>

The authors have no financial conflicts of interest related to the conduct or publication of this work to disclose.

Capillaroscopy (capillary microscopy) is a non-standard measure of capillary structure. However, currently, there are no standard methods for direct assessment of capillary structure.Furthermore, capillary microscopy has been widely used for the direct evaluation of capillarydensity in a large and growing body of published work 12, 13, 10, 11, 14-18. Additionally, we have validated the capillary microscopy technique by correlating capillaroscopy findings with forearm blood flow, a well-established measure of v...

non-invasive assessment of microvascular and endothelial function

The authors have utilized capillaroscopy and forearm blood flow techniques to investigate the role of microvascular dysfunction in pathogenesis of cardiovascular disease. Capillaroscopy is a non-invasive, relatively inexpensive methodology for directly visualizing the microcirculation. Percent capillary recruitment is assessed by dividing the increase in capillary density induced by postocclusive reactive hyperemia (postocclusive reactive hyperemia capillary density minus baseline capillary density), by the maximal capillary density (observed during passive venous occlusion). Percent perfused capillaries represents the proportion of all capillaries present that are perfused (functionally active), and is calculated by dividing postocclusive reactive hyperemia capillary density by the maximal capillary density. Both percent capillary recruitment and percent perfused capillaries reflect the number of functional capillaries. The forearm blood flow (FBF) technique provides accepted non-invasive measures of endothelial function: The ratio FBFmax/FBFbase is computed as an estimate of vasodilation, by dividing the mean of the four FBFmax values by the mean of the four FBFbase values. Forearm vascular resistance at maximal vasodilation (FVRmax) is calculated as the mean arterial pressure (MAP) divided by FBFmax. Both the capillaroscopy and forearm techniques are readily acceptable to patients and can be learned quickly.
The microvascular and endothelial function measures obtained using the methodologies described in this paper may have future utility in clinical patient cardiovascular risk-reduction strategies. As we have published reports demonstrating that microvascular and endothelial dysfunction are found in initial stages of hypertension including prehypertension, microvascular and endothelial function measures may eventually aid in early identification, risk-stratification and prevention of end-stage vascular pathology, with its potentially fatal consequences.

Differences in the appearance of the microvasculature between normotensive and hypertensive individuals are readily apparent by comparing Figures 4 and 5. Figure 4 shows the typical network of straight capillaries in well organized rows in a normotensive individual. In contrast, Figure 5 demonstrates a more disarranged pattern of shrunken, coiled capillaries.
The authors have an ongoing interest in the role of microvascular dy...

Watch this Scientific Journal Video about Non-invasive Assessment of Microvascular and Endothelial Function at JoVE.com

Non-invasive Assessment of Microvascular and Endothelial Function

Capillaroscopy is a non-invasive, relatively inexpensive methodology for directly visualizing the microcirculation. The forearm blood flow technique provides accepted non-invasive measures of endothelial function.

The authors have utilized capillaroscopy and forearm blood flow techniques to investigate the role of microvascular dysfunction in pathogenesis of ...

non-invasive-assessment-of-microvascular-and-endothelial-function

Research

JoVE Journal

Medicine

16.1K Views.  Thomas Jefferson University. Capillaroscopy is a non-invasive, relatively inexpensive methodology for directly visualizing the microcirculation. The forearm blood flow technique provides accepted non-invasive measures of endothelial function.

Video: Non-invasive Assessment of Microvascular and Endothelial Function

Non-invasive Optical Measurement of Cerebral Metabolism and Hemodynamics in Infants

Perinatal brain injury remains a significant cause of infant mortality and morbidity, but there is not yet an effective bedside tool that can accurately screen for brain injury, monitor injury evolution, or assess response to therapy. The energy used by neurons is derived largely from tissue oxidative metabolism, and neural hyperactivity and cell death are reflected by corresponding changes in cerebral oxygen metabolism (CMRO2). Thus, measures of CMRO2 are reflective of neuronal viability and provide critical diagnostic information, making CMRO2 an ideal target for bedside measurement of brain health.
Brain-imaging techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) yield measures of cerebral glucose and oxygen metabolism, but these techniques require the administration of radionucleotides, so they are used in only the most acute cases.
Continuous-wave near-infrared spectroscopy (CWNIRS) provides non-invasive and non-ionizing radiation measures of hemoglobin oxygen saturation (SO2) as a surrogate for cerebral oxygen consumption. However, SO2 is less than ideal as a surrogate for cerebral oxygen metabolism as it is influenced by both oxygen delivery and consumption. Furthermore, measurements of SO2 are not sensitive enough to detect brain injury hours after the insult 1,2, because oxygen consumption and delivery reach equilibrium after acute transients 3. We investigated the possibility of using more sophisticated NIRS optical methods to quantify cerebral oxygen metabolism at the bedside in healthy and brain-injured newborns. More specifically, we combined the frequency-domain NIRS (FDNIRS) measure of SO2 with the diffuse correlation spectroscopy (DCS) measure of blood flow index (CBFi) to yield an index of CMRO2 (CMRO2i) 4,5.
With the combined FDNIRS/DCS system we are able to quantify cerebral metabolism and hemodynamics. This represents an improvement over CWNIRS for detecting brain health, brain development, and response to therapy in neonates. Moreover, this method adheres to all neonatal intensive care unit (NICU) policies on infection control and institutional policies on laser safety. Future work will seek to integrate the two instruments to reduce acquisition time at the bedside and to implement real-time feedback on data quality to reduce the rate of data rejection.

We combined frequency-domain near-infrared spectroscopy measures of cerebral hemoglobin oxygenation with diffuse correlation spectroscopy measures of cerebral blood flow index to estimate an index of oxygen metabolism. We tested the utility of this measure as a bedside screening tool to evaluate the health and development of the newborn brain.

Perinatal brain injury remains a significant cause of infant mortality  and morbidity, but there is not yet an effective bedside tool that can  accurately ...

Murine Spinotrapezius Model to Assess the Impact of Arteriolar Ligation on Microvascular Function and Remodeling

The murine spinotrapezius is a thin, superficial skeletal support muscle that extends from T3 to L4, and is easily accessible via dorsal skin incision. Its unique anatomy makes the spinotrapezius useful for investigation of ischemic injury and subsequent microvascular remodeling. Here, we demonstrate an arteriolar ligation model in the murine spinotrapezius muscle that was developed by our research team and previously published1-3. For certain vulnerable mouse strains, such as the Balb/c mouse, this ligation surgery reliably creates skeletal muscle ischemia and serves as a platform for investigating therapies that stimulate revascularization. Methods of assessment are also demonstrated, including the use of intravital and confocal microscopy. The spinotrapezius is well suited to such imaging studies due to its accessibility (superficial dorsal anatomy) and relative thinness (60-200 &mu;m). The spinotrapezius muscle can be mounted en face, facilitating imaging of whole-muscle microvascular networks without histological sectioning. We describe the use of intravital microscopy to acquire metrics following a functional vasodilation procedure; specifically, the increase in arterilar diameter as a result of muscle contraction. We also demonstrate the procedures for harvesting and fixing the tissues, a necessary precursor to immunostaining studies and the use of confocal microscopy.

We demonstrate a novel arterial ligation model in murine spinotrapezius muscle, including a step-by-step procedure and description of required instrumentation. We describe the surgery and relevant outcome measurements relating to vascular network remodeling and functional vasodilation using intravital and confocal microscopy.

The murine spinotrapezius is a thin, superficial skeletal support muscle that extends from T3 to L4, and is easily accessible via dorsal skin incision. ...

Murine Model for Non-invasive Imaging to Detect and Monitor Ovarian Cancer Recurrence

Epithelial ovarian cancer is the most lethal gynecologic malignancy in the United States. Although patients initially respond to the current standard of care consisting of surgical debulking and combination chemotherapy consisting of platinum and taxane compounds, almost 90% of patients recur within a few years. In these patients the development of chemoresistant disease limits the efficacy of currently available chemotherapy agents and therefore contributes to the high mortality. To discover novel therapy options that can target recurrent disease, appropriate animal models that closely mimic the clinical profile of patients with recurrent ovarian cancer are required. The challenge in monitoring intra-peritoneal (i.p.) disease limits the use of i.p. models and thus most xenografts are established subcutaneously. We have developed a sensitive optical imaging platform that allows the detection and anatomical location of i.p. tumor mass. The platform includes the use of optical reporters that extend from the visible light range to near infrared, which in combination with 2-dimensional X-ray co-registration can provide anatomical location of molecular signals. Detection is significantly improved by the use of a rotation system that drives the animal to multiple angular positions for 360 degree imaging, allowing the identification of tumors that are not visible in single orientation. This platform provides a unique model to non-invasively monitor tumor growth and evaluate the efficacy of new therapies for the prevention or treatment of recurrent ovarian cancer.

We describe a non-invasive animal imaging platform that allows the detection, quantification, and monitoring of ovarian cancer growth and recurrence. This intra-peritoneal xenograft model mimics the clinical profile of patients with ovarian cancer.

Epithelial ovarian cancer is the most lethal gynecologic malignancy in the United States. Although patients initially respond to the current standard of ...

A Methodological Approach to Non-invasive Assessments of Vascular Function and Morphology

The endothelium is the innermost lining of the vasculature and is involved in the maintenance of vascular homeostasis. Damage to the endothelium may predispose the vessel to atherosclerosis and increase the risk for cardiovascular disease. Assessments of peripheral endothelial function are good indicators of early abnormalities in the vascular wall and correlate well with assessments of coronary endothelial function. The present manuscript details the important methodological steps necessary for the assessment of microvascular endothelial function using laser Doppler imaging with iontophoresis, large vessel endothelial function using flow-mediated dilatation, and carotid atherosclerosis using carotid artery ultrasound. A discussion on the methodological considerations for each of the techniques is also presented, and recommendations are made for future research.

The present article describes the methodological considerations for several non-invasive assessments of vascular function and morphology that are commonly used in medical research to assess different stages of atherosclerosis.

The endothelium is the innermost lining of the vasculature and is involved in the maintenance of vascular homeostasis.  Damage to the endothelium may ...

Non-invasive Assessment of the Efficacy of New Therapeutics for Intestinal Pathologies Using Serial Endoscopic Imaging of Live Mice

Animal models of inflammatory bowel disease (IBD) and colorectal cancer (CRC) have provided significant insight into the cell intrinsic and extrinsic mechanisms that contribute to the onset and progression of intestinal diseases. The identification of new molecules that promote these pathologies has led to a flurry of activity focused on the development of potential new therapies to inhibit their function. As a result, various pre-clinical mouse models with an intact immune system and stromal microenvironment are now heavily used. Here we describe three experimental protocols to test the efficacy of new therapeutics in pre-clinical models of (1) acute mucosal damage, (2) chronic colitis and/or colitis-associated colon cancer, and (3) sporadic colorectal cancer. We also outline procedures for serial endoscopic examination that can be used to document the therapeutic response of an individual tumor and to monitor the health of individual mice. These protocols provide complementary experimental platforms to test the effectiveness of therapeutic compounds shown to be well tolerated by mice.

We describe methods for longitudinal monitoring of the efficacy of therapeutics for the treatment of colonic pathologies in mice using a rigid endoscope. This protocol can be readily used for the characterization of the therapeutic response of an individual tumor in live mice and also for monitoring potential disease relapse.

Animal models of inflammatory bowel disease (IBD) and colorectal cancer (CRC) have provided significant insight into the cell intrinsic and extrinsic ...

Ultrasound Assessment of Endothelial Function: A Technical Guideline of the Flow-mediated Dilation Test

Cardiovascular disease is the primary cause of mortality and a major cause of disability worldwide. The dysfunction of the vascular endothelium is a pathological condition characterized mainly by a disruption in the balance between vasodilator and vasoconstrictor substances and is proposed to play an important role in the development of atherosclerotic cardiovascular disease. Therefore, a precise evaluation of endothelial function in humans represents an important tool that could help better understand the etiology of multiple cardio-centric pathologies.
Over the past twenty-five years, many methodological approaches have been developed to provide an assessment of endothelial function in humans. Introduced in 1989, the FMD test incorporates a forearm occlusion and subsequent reactive hyperemia that promotes nitric oxide production and vasodilation of the brachial artery. The FMD test is now the most widely utilized, non-invasive, ultrasonic assessment of endothelial function in humans and has been associated with future cardiovascular events.
Although the FMD test could have clinical utility, it is a physiological assessment that has inherited several confounding factors that need to be considered. This article describes a standardized protocol for determining FMD including the recommended methodology to help minimize the physiological and technical issues and improve the precision and reproducibility of the assessment.

The flow mediated dilation (FMD) test is the most commonly utilized, non-invasive, ultrasound assessment of endothelial function in humans. Although the FMD test has been related with the prediction of future cardiovascular disease and events, it is a physiological assessment with many inherent confounding factors that need to be considered.

Cardiovascular disease is the primary cause of mortality and a major cause of disability worldwide. The dysfunction of the vascular endothelium is a ...

Assessment of Human Adipose Tissue Microvascular Function Using Videomicroscopy

While obesity is closely linked to the development of metabolic and cardiovascular disease, little is known about mechanisms that govern these processes. It is hypothesized that pro-atherogenic mediators released from fat tissues particularly in association with central/visceral adiposity may promote pathogenic vascular changes locally and systemically, and the notion that cardiovascular disease may be the consequence of adipose tissue dysfunction continues to evolve. Here, we describe a unique method of videomicroscopy that involves analysis of vasodilator and vasoconstrictor responses of intact small human arterioles removed from the adipose depot of living human subjects. Videomicroscopy is used to examine functional properties of isolated microvessels in response to pharmacological or physiological stimuli using a pressured system that mimics in vivo conditions. The technique is a useful approach to gain understanding of the pathophysiology and molecular mechanisms that contribute to vascular dysfunction locally within the adipose tissue milieu. Moreover, abnormalities in the adipose tissue microvasculature have also been linked with systemic diseases. We applied this technique to examine depot-specific vascular responses in obese subjects. We assessed endothelium-dependent vasodilation to both increased flow and acetylcholine in adipose arterioles (50 - 350 &#181;m internal diameter, 2 - 3 mm in length) isolated from two different adipose depots during bariatric surgery from the same individual. We demonstrated that arterioles from visceral fat exhibit impaired endothelium-dependent vasodilation compared to vessels isolated from the subcutaneous depot. The findings suggest that the visceral microenvironment is associated with vascular endothelial dysfunction which may be relevant to clinical observation linking increased visceral adiposity to systemic disease mechanisms. The videomicroscopy technique can be used to examine vascular phenotypes from different fat depots as well as compare findings across individuals with different degrees of obesity and metabolic dysfunction. The method can also be used to examine vascular responses longitudinally in response to clinical interventions.

Videomicroscopy systems are used to examine functional properties of isolated adipose tissue arterioles in response to physiological and pharmacological stimuli. This technique can be used to examine microvascular phenotypes in different adipose tissue domains in obese humans.

While obesity is closely linked to the development of metabolic and cardiovascular disease, little is known about mechanisms that govern these processes. ...

Assessment of Kidney Function in Mouse Models of Glomerular Disease

The use of murine models to mimic human kidney disease is becoming increasingly common. Our research is focused on the assessment of glomerular function in diabetic nephropathy and podocyte-specific VEGF-A knock-out mice; therefore, this protocol describes the full kidney work-up used in our lab to assess these mouse models of glomerular disease, enabling a vast amount of information regarding kidney and glomerular function to be obtained from a single mouse. In comparison to alternative methods presented in the literature to assess glomerular function, the use of the method outlined in this paper enables the glomerular phenotype to be fully evaluated from multiple aspects. By using this method, the researcher can determine the kidney phenotype of the model and assess the mechanism as to why the phenotype develops. This vital information on the mechanism of disease is required when examining potential therapeutic avenues in these models. The methods allow for detailed functional assessment of the glomerular filtration barrier through measurement of the urinary albumin creatinine ratio and individual glomerular water permeability, as well as both structural and ultra-structural examination using the Periodic Acid Schiff stain and electron microscopy. Furthermore, analysis of the genes dysregulated at the mRNA and protein level enables mechanistic analysis of glomerular function. This protocol outlines the generic but adaptable methods that can be applied to all mouse models of glomerular disease.

This protocol describes a full kidney work-up that should be carried out in mouse models of glomerular disease. The methods allow for detailed functional, structural, and mechanistic analysis of glomerular function, which can be applied to all mouse models of glomerular disease.

The use of murine models to mimic human kidney disease is becoming increasingly common. Our research is focused on the assessment of glomerular function ...

Non-invasive Assessment of Dorsiflexor Muscle Function in Mice

Assessment of skeletal muscle contractile function is an important measurement for both clinical and research purposes. Numerous conditions can negatively affect skeletal muscle. This can result in a loss of muscle mass (atrophy) and/or loss of muscle quality (reduced force per unit of muscle mass), both of which are prevalent in chronic disease, muscle-specific disease, immobilization, and aging (sarcopenia). Skeletal muscle function in animals can be evaluated by a range of different tests. All tests have limitations related to the physiological testing environment, and the selection of a specific test often depends on the nature of the experiments. Here, we describe an in vivo, non-invasive technique involving a helpful and easy assessment of force frequency-curve (FFC) in mice that can be performed on the same animal over time. This permits monitoring of disease progression and/or efficacy&#160;of a potential therapeutic treatment.

Measurement of rodent skeletal muscle contractile function is a useful tool that can be used to track disease progression as well as efficacy of therapeutic intervention. We describe here the non-invasive, in vivo assessment of the dorsiflexor muscles that can be repeated over time in the same mouse.

Assessment of skeletal muscle contractile function is an important measurement for both clinical and research purposes. Numerous conditions can negatively ...

A Computerized Functional Skills Assessment and Training Program Targeting Technology Based Everyday Functional Skills

Today, many functional skills are technology-based, so development of a technology-based training program has broad importance. Here we present a computerized functional skills training program that was paired in half of the participants with a commercially available cognitive training (CCT) program.
Non-impaired older individuals (NC) aged 60+ (n=45) and similarly aged individuals with mild cognitive impairment (MCI; n=50) were randomized to receive 12 weeks of twice-weekly computerized functional skills training (CFST) or 12 weeks of twice-weekly sessions split between CCT and CFST. Skills trained were use of an ATM; internet banking; ticket kiosk; telephone and internet prescription refill; medication management; and internet shopping. As with previous functional capacity assessments, we focus on completion time for each simulation.
51 participants completed the training program, either by mastering all 6 tasks (34) or completing 12 weeks of training. 44 more participants completed 4 or more training sessions so they were also analyzed for improvement up to their last training session. Completion time for all 6 tests significantly improved from the baseline assessment to the final training session in both groups of participants (all p&#60;0.001 with an average improvement in task completion time of 45%). Further, there was no differential improvement in MCI and NC in the 6 tests from baseline to end of training (all t&#60;1.66, all p&#62;0.12). Finally, combined CCT plus CFST did not differ from CSFT alone on any of the percent-change score measures (all t&#60;1.64, all p&#62;0.11).
Both NC and MCI groups evidenced substantial improvements in performance. CCT supplementation led to similar functional gains with half as many training sessions. The NC participants proceeded through the training fairly rapidly even without CCT supplementation; MCI participants required more training but learned equivalently. These findings suggest that even in cases with memory impairments, functional skills can be efficiently learned with training.

This training protocol uses computerized training to teach technology-related everyday functional skills. These skills include financial skills, travel and transit, as well as medication management.