This work was financially support by the grants from Research Grant Council of Hong Kong [17124718 and 17121714], Hong Kong Health and Medical Research Fund [13142651 and 13142641], Collaborative Research Fund of Hong Kong [C7055-14G], and the National Basic Research Program of China [973 Program 2015CB553603].

<ol>
	<li>Furchgott, R. F., Zawadzki, J. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+obligatory+role+of+endothelial+cells+in+the+relaxation+of+arterial+smooth+muscle+by+acetylcholine.">The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine.</a> Nature. 288 (5789), 373-376 (1980).</li><li>Furchgott, R. F., Vanhoutte, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelium-derived+relaxing+and+contracting+factors.">Endothelium-derived relaxing and contracting factors.</a> The FASEB Journal. 3 (9), 2007-2018 (1989).</li><li>Feletou, M., Kohler, R., Vanhoutte, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelium-derived+vasoactive+factors+and+hypertension:+possible+roles+in+pathogenesis+and+as+treatment+targets.">Endothelium-derived vasoactive factors and hypertension: possible roles in pathogenesis and as treatment targets.</a> Current Hypertension Reports. 12 (4), 267-275 (2010).</li><li>Vanhoutte, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+dysfunction:+the+first+step+toward+coronary+arteriosclerosis.">Endothelial dysfunction: the first step toward coronary arteriosclerosis.</a> Circulation Journal. 73 (4), 595-601 (2009).</li><li>Feletou, M., Huang, Y., Vanhoutte, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelium-mediated+control+of+vascular+tone:+COX-1+and+COX-2+products.">Endothelium-mediated control of vascular tone: COX-1 and COX-2 products.</a> British Journal of Pharmacology. 164 (3), 894-912 (2011).</li><li>Harrison, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+and+molecular+mechanisms+of+endothelial+cell+dysfunction.">Cellular and molecular mechanisms of endothelial cell dysfunction.</a> Journal of Clinical Investigation. 100 (9), 2153 (1997).</li><li>Vanhoutte, P. M., Shimokawa, H., Tang, E. H., Feletou, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+dysfunction+and+vascular+disease.">Endothelial dysfunction and vascular disease.</a> Acta physiologica. 196 (2), 193-222 (2009).</li><li>Kl&#246;&#223;, S., Bouloumi&#233;, A., M&#252;lsch, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aging+and+chronic+hypertension+decrease+expression+of+rat+aortic+soluble+guanylyl+cyclase.">Aging and chronic hypertension decrease expression of rat aortic soluble guanylyl cyclase.</a> Hypertension. 35 (1), 43-47 (2000).</li><li>Csiszar, A., 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=Aging-induced+phenotypic+changes+and+oxidative+stress+impair+coronary+arteriolar+function.">Aging-induced phenotypic changes and oxidative stress impair coronary arteriolar function.</a> Circulation Research. 90 (11), 1159-1166 (2002).</li><li>Guo, Y., 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=Endothelial+SIRT1+prevents+age-induced+impairment+of+vasodilator+responses+by+enhancing+the+expression+and+activity+of+soluble+guanylyl+cyclase+in+smooth+muscle+cells.">Endothelial SIRT1 prevents age-induced impairment of vasodilator responses by enhancing the expression and activity of soluble guanylyl cyclase in smooth muscle cells.</a> Cardiovascular Research. , (2018).</li><li>Auch-Schwelk, W., Katusic, Z. S., Vanhoutte, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitric+oxide+inactivates+endothelium-derived+contracting+factor+in+the+rat+aorta.">Nitric oxide inactivates endothelium-derived contracting factor in the rat aorta.</a> Hypertension. 19 (5), 442-445 (1992).</li><li>Tang, E. H., Feletou, M., Huang, Y., Man, R. Y., Vanhoutte, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acetylcholine+and+sodium+nitroprusside+cause+long-term+inhibition+of+EDCF-mediated+contractions.">Acetylcholine and sodium nitroprusside cause long-term inhibition of EDCF-mediated contractions.</a> American Journal of Physiology - Heart and Circulation Physiology. 289 (6), H2434-H2440 (2005).</li><li>Ghiadoni, L., 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=Endothelial+function+and+common+carotid+artery+wall+thickening+in+patients+with+essential+hypertension.">Endothelial function and common carotid artery wall thickening in patients with essential hypertension.</a> Hypertension. 32 (1), 25-32 (1998).</li><li>Xu, X., 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=Age-related+Impairment+of+Vascular+Structure+and+Functions.">Age-related Impairment of Vascular Structure and Functions.</a> Aging and Disease. 8 (5), 590-610 (2017).</li><li>Tabit, C. E., Chung, W. B., Hamburg, N. M., Vita, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+dysfunction+in+diabetes+mellitus:+Molecular+mechanisms+and+clinical+implications.">Endothelial dysfunction in diabetes mellitus: Molecular mechanisms and clinical implications.</a> Reviews in Endocrine &amp; Metabolic Disorders. 11 (1), 61-74 (2010).</li><li>Tanaka, K., Sata, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Roles+of+perivascular+adipose+tissue+in+the+pathogenesis+of+atherosclerosis.">Roles of perivascular adipose tissue in the pathogenesis of atherosclerosis.</a> Frontiers in Physiology. 9, 3 (2018).</li><li>Brown, N. K., 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=Perivascular+adipose+tissue+in+vascular+function+and+disease:+a+review+of+current+research+and+animal+models.">Perivascular adipose tissue in vascular function and disease: a review of current research and animal models.</a> Arteriosclerosis Thrombosis and Vascular Biology. 34 (8), 1621-1630 (2014).</li><li>Lohn, 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=Periadventitial+fat+releases+a+vascular+relaxing+factor.">Periadventitial fat releases a vascular relaxing factor.</a> The FASEB Journal. 16 (9), 1057-1063 (2002).</li><li>G&#225;lvez-Prieto, B., 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=A+reduction+in+the+amount+and+anti-contractile+effect+of+periadventitial+mesenteric+adipose+tissue+precedes+hypertension+development+in+spontaneously+hypertensive+rats.">A reduction in the amount and anti-contractile effect of periadventitial mesenteric adipose tissue precedes hypertension development in spontaneously hypertensive rats.</a> Hypertension research. 31 (7), 1415 (2008).</li><li>Gao, Y. J., Lu, C., Su, L. Y., Sharma, A., Lee, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modulation+of+vascular+function+by+perivascular+adipose+tissue:+the+role+of+endothelium+and+hydrogen+peroxide.">Modulation of vascular function by perivascular adipose tissue: the role of endothelium and hydrogen peroxide.</a> British Journal of Pharmacology. 151 (3), 323-331 (2007).</li><li>Gao, Y. -. 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=Perivascular+adipose+tissue+promotes+vasoconstriction:+the+role+of+superoxide+anion.">Perivascular adipose tissue promotes vasoconstriction: the role of superoxide anion.</a> Cardiovascular Research. 71 (2), 363-373 (2006).</li><li>Szasz, T., Webb, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perivascular+adipose+tissue:+more+than+just+structural+support.">Perivascular adipose tissue: more than just structural support.</a> Clinical Science (London). 122 (1), 1-12 (2012).</li><li>Ramirez, J. G., O'Malley, E. J., Ho, W. S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pro-contractile+effects+of+perivascular+fat+in+health+and+disease.">Pro-contractile effects of perivascular fat in health and disease.</a> Brish Journal of Pharmacology. 174 (20), 3482-3495 (2017).</li><li>Hajer, G. R., van Haeften, T. W., Visseren, F. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adipose+tissue+dysfunction+in+obesity,+diabetes,+and+vascular+diseases.">Adipose tissue dysfunction in obesity, diabetes, and vascular diseases.</a> European Heart Journal. 29 (24), 2959-2971 (2008).</li><li>Mulvany, M. J., Halpern, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contractile+properties+of+small+arterial+resistance+vessels+in+spontaneously+hypertensive+and+normotensive+rats.">Contractile properties of small arterial resistance vessels in spontaneously hypertensive and normotensive rats.</a> Circulation Research. 41 (1), 19-26 (1977).</li><li>Mulvany, M. J., Halpern, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+properties+of+vascular+smooth+muscle+cells+in+situ.">Mechanical properties of vascular smooth muscle cells in situ.</a> Nature. 260 (5552), 617-619 (1976).</li><li>del Campo, L., Ferrer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wire+myography+to+study+vascular+tone+and+vascular+structure+of+isolated+mouse+arteries.">Wire myography to study vascular tone and vascular structure of isolated mouse arteries.</a> Methods in Molecular Biology. 1339, 255-276 (2015).</li><li>Dobrin, P. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+initial+length+on+length-tension+relationship+of+vascular+smooth+muscle.">Influence of initial length on length-tension relationship of vascular smooth muscle.</a> American Journal of Physiology. 225 (3), 664-670 (1973).</li><li>Xu, C., 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=Calorie+restriction+prevents+metabolic+aging+caused+by+abnormal+SIRT1+function+in+adipose+tissues.">Calorie restriction prevents metabolic aging caused by abnormal SIRT1 function in adipose tissues.</a> Diabetes. 64 (5), 1576-1590 (2015).</li><li>Sheykhzade, M., Nyborg, N. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Caliber+dependent+calcitonin+gene-related+peptide-induced+relaxation+in+rat+coronary+arteries:+effect+of+K++on+the+tachyphylaxis.">Caliber dependent calcitonin gene-related peptide-induced relaxation in rat coronary arteries: effect of K+ on the tachyphylaxis.</a> European Journal of Pharmacology. 351 (1), 53-59 (1998).</li><li>Soltis, E. E., Cassis, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+perivascular+adipose+tissue+on+rat+aortic+smooth+muscle+responsiveness.">Influence of perivascular adipose tissue on rat aortic smooth muscle responsiveness.</a> Clinical and Experimental Hypertension A. 13 (2), 277-296 (1991).</li><li>Lohn, 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=Periadventitial+fat+releases+a+vascular+relaxing+factor.">Periadventitial fat releases a vascular relaxing factor.</a> FASEB Journal. 16 (9), 1057-1063 (2002).</li><li>Fesus, G., 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=Adiponectin+is+a+novel+humoral+vasodilator.">Adiponectin is a novel humoral vasodilator.</a> Cardiovascular Research. 75 (4), 719-727 (2007).</li><li>Greenstein, A. S., 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=Local+inflammation+and+hypoxia+abolish+the+protective+anticontractile+properties+of+perivascular+fat+in+obese+patients.">Local inflammation and hypoxia abolish the protective anticontractile properties of perivascular fat in obese patients.</a> Circulation. 119 (12), 1661-1670 (2009).</li><li>Yudkin, J. S., Eringa, E., 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="Vasocrine"+signalling+from+perivascular+fat:+a+mechanism+linking+insulin+resistance+to+vascular+disease.">"Vasocrine" signalling from perivascular fat: a mechanism linking insulin resistance to vascular disease.</a> Lancet. 365 (9473), 1817-1820 (2005).</li><li>Xia, N., 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=Uncoupling+of+endothelial+nitric+oxide+synthase+in+perivascular+adipose+tissue+of+diet-induced+obese+mice.">Uncoupling of endothelial nitric oxide synthase in perivascular adipose tissue of diet-induced obese mice.</a> Arteriosclerosis Thrombosis and Vascular Biology. 36 (1), 78-85 (2016).</li><li>Xia, N., Forstermann, U., Li, H. <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+resveratrol+on+eNOS+in+the+endothelium+and+the+perivascular+adipose+tissue.">Effects of resveratrol on eNOS in the endothelium and the perivascular adipose tissue.</a> Annals of the New York Academy of Sciences. 1403 (1), 132-141 (2017).</li><li>Schinzari, F., Tesauro, M., Cardillo, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+and+perivascular+adipose+tissue+abnormalities+in+obesity-related+vascular+dysfunction:+novel+targets+for+treatment.">Endothelial and perivascular adipose tissue abnormalities in obesity-related vascular dysfunction: novel targets for treatment.</a> Journal of Cardiovascular Pharmacology. 69 (6), 360-368 (2017).</li><li>Liu, J. T., 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=Lipocalin-2+deficiency+prevents+endothelial+dysfunction+associated+with+dietary+obesity:+role+of+cytochrome+P450+2C+inhibition.">Lipocalin-2 deficiency prevents endothelial dysfunction associated with dietary obesity: role of cytochrome P450 2C inhibition.</a> British Journal of Pharmacology. 165 (2), 520-531 (2012).</li><li>Martinez-Quinones, P., 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=Hypertension+induced+morphological+and+physiological+changes+in+cells+of+the+arterial+wall.">Hypertension induced morphological and physiological changes in cells of the arterial wall.</a> American Journal of Hypertension. 31 (10), 1067-1078 (2018).</li><li>Outzen, E. 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=Translational+value+of+mechanical+and+vasomotor+properties+of+mouse+isolated+mesenteric+resistance-sized+arteries.">Translational value of mechanical and vasomotor properties of mouse isolated mesenteric resistance-sized arteries.</a> Pharmacology Research and Perspectives. 3 (6), e00200 (2015).</li><li>Sheykhzade, M., Simonsen, A. H., Boonen, H. C., Outzen, E. M., Nyborg, N. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+ageing+on+the+passive+and+active+tension+and+pharmacodynamic+characteristics+of+rat+coronary+arteries:+age-dependent+increase+in+sensitivity+to+5-HT+and+K+.">Effect of ageing on the passive and active tension and pharmacodynamic characteristics of rat coronary arteries: age-dependent increase in sensitivity to 5-HT and K+.</a> Pharmacology. 90 (3-4), 160-168 (2012).</li></ol>

Authors have nothing to disclose.

Apart from the endothelial cells, signals derived from PVAT play an important role in the regulation of smooth muscle tone reactivity30. Healthy PVAT releases NO and anti-inflammatory adiponectin to exert an anti-contractile effect on arteries, which is lost under pathological conditions such as obesity and metabolic syndrome31,32. In disease states, PVAT contributes to the development of endothelial dysfunction and other cardiovascular ab...

Dilatations and constrictions of arteries are achieved by relaxations and contractions, respectively, of their vascular smooth muscle cells. Changes in vascular responsiveness of small arteries contribute to the homeostatic regulation of arterial blood pressure by autonomic nerves and hormones present in the blood (e.g., catecholamines, angiotensin II, serotonin, vasopressin). At the local level, the vascular responses of smooth muscle cells are modulated by signals from both the endothelial cells of the intima and the adipose tissue surrounding the arteries (Figure 1).
The endothelium is not only a passive barrier, but also serves as a surface to exchange signals between the blood and the underlying vascular smooth muscle cells. By releasing various vasoactive substances, the endothelium plays a critical role in the local control of vascular tone responses1. For example, in response to acetylcholine, endothelial nitric oxide synthase (eNOS) is activated in the endothelium to produce nitric oxide (NO), which induces relaxation of the underlying vascular smooth muscle by activating soluble guanylyl cyclase (sGC)2. Other vasoactive substances include the products of cyclooxygenases (e.g., prostacyclin and thromboxane A2), lipoxygenase (e.g., 12-hydroxyeicosatetraenoic acids, 12-HETE), and cytochrome P450 monooxygenases (HETEs and epoxyeicosatrienoic acids, EETs), reactive oxygen species (ROS), and vasoactive peptides (e.g., endothelin-1 and angiotensin II), and endothelium-derived hyperpolarizing factors (EDHF)3. A delicate balance between endothelium-derived vasodilators and vasoconstrictors maintain the local vasomotor tone4,5.
Endothelial dysfunction is characterized by the impairment in endothelium-dependent vasodilatation6, a hallmark of vascular aging7. With age, the ability of endothelium to promote vasodilatation is progressively reduced, due largely to a decreased NO bioavailability, as well as the abnormal expression and function of eNOS in the endothelium and sGC in the vascular smooth muscle cells8,9,10. Reduced NO bioavailability potentiates the production of endothelium-dependent vasoconstrictors11,12. In aged arteries, endothelial dysfunction causes hyperplasia in the media, as reflected by the marked increases in wall thickness, number of medial nuclei, which are reminiscent of the arterial thickening in hypertension and atherosclerosis observed in human patients13,14. In addition, pathophysiological conditions such as obesity, diabetes or hypertension accelerate the development of endothelial dysfunction15,16.
Perivascular adipose tissue (PVAT) releases numerous adipokines to regulate vascular structure and function17. The anti-contractile effect of PVAT is mediated by relaxing factors, such as adiponectin, NO, hydrogen peroxide and hydrogen sulphide18,19,20. However, depending on the location and pathophysiological condition, PVAT also can enhance contractile responses&#160;in various arteries21. The pro-contractile substances produced by PVAT include angiotensin-II, leptin, resistin, and ROS22,23.&#160; In most of the studies on isolated blood vessels, PVAT has been considered as a simple structural support for the vasculature and thus removed during the preparation of blood vessel ring segments. Since adipose dysfunction represents an independent risk factor for hypertension and associated cardiovascular complications24, the PVAT surrounding the blood vessels should be considered when investigating the vascular responsiveness of different arteries.
The multi wire myograph systems have been widely used to investigate the vasomotor functions of a variety of blood vessels, including the aorta, mesenteric, renal, femoral, cerebral and coronary arteries25,26. The protocols described herein will use wire myography to evaluate vascular responsiveness in mesenteric arteries isolated from genetically modified mouse models, with a special focus on the modulation by PVAT.

<table><tbody><tr><td>Acetylcholine</td><td>Sigma-Aldrich</td><td>A6625</td><td>&lt;strong&gt;Stock concentration&lt;/strong&gt;: 10&lt;sup&gt;-1&lt;/sup&gt; M&lt;br/&gt; &lt;strong&gt;Working concentration&lt;/strong&gt;: 10&lt;sup&gt;-10&lt;/sup&gt; to 10&lt;sup&gt;-5&lt;/sup&gt; M</td></tr><tr><td>L-NAME (N&amp;omega;-nitro-L-arginine methyl ester)</td><td>Sigma-Aldrich</td><td>N5751</td><td>&lt;strong&gt;Stock concentration&lt;/strong&gt;: 3 x 10&lt;sup&gt;-2&lt;/sup&gt; M&lt;br/&gt; &lt;strong&gt;Working concentration&lt;/strong&gt;: 10&lt;sup&gt;-4&lt;/sup&gt; M</td></tr><tr><td>Phenylephrine</td><td>Sigma-Aldrich</td><td>P6126</td><td>&lt;strong&gt;Stock concentration&lt;/strong&gt;: 10&lt;sup&gt;-2&lt;/sup&gt; M&lt;br/&gt; &lt;strong&gt;Working concentration&lt;/strong&gt;: 10&lt;sup&gt;-10&lt;/sup&gt; to 10&lt;sup&gt;-5&lt;/sup&gt; M</td></tr><tr><td>U46619 (9,11-dideoxy-9&amp;alpha;,11&amp;alpha;methanoepoxy prostaglandin F2&amp;alpha;)</td><td>Enzo</td><td>BML-PG023-0001</td><td>&lt;strong&gt;Stock concentration&lt;/strong&gt;: 10&lt;sup&gt;-5&lt;/sup&gt; M&lt;br/&gt; &lt;strong&gt;Working concentration&lt;/strong&gt;: 1&lt;sup&gt;-3&lt;/sup&gt; x 10&lt;sup&gt;-8&lt;/sup&gt; M</td></tr><tr><td>Multiwire myograph</td><td>Danish MyoTechnology (DMT)</td><td>620M</td><td></td></tr><tr><td>PowerLab 4/26</td><td>ADInstruments</td><td>ML848</td><td></td></tr><tr><td>Labchart7</td><td>ADInstruments</td><td>-</td><td></td></tr><tr><td>Adipo-SIRT1 wild type mice</td><td>Laboratory Animal Unit, The University of Hong Kong</td><td>CULATR NO.: 4085-16</td><td></td></tr><tr><td>Silicon-coated Petri dishes</td><td>Danish MyoTechnology (DMT)</td><td></td><td></td></tr><tr><td>Tungsten wires</td><td>Danish MyoTechnology (DMT)</td><td>300331</td><td></td></tr><tr><td>Surgical tools</td><td></td><td></td><td></td></tr></tbody></table>

assessment of vascular tone responsiveness using isolated mesenteric arteries with a focus on modulation by perivascular adipose tissues

Altered vascular tone responsiveness to pathophysiological stimuli contributes to the development of a wide range of cardiovascular and metabolic diseases. Endothelial dysfunction represents a major culprit for the reduced vasodilatation and enhanced vasoconstriction of arteries. Adipose (fat) tissues surrounding the arteries play important roles in the regulation of endothelium-dependent relaxation and/or contraction of the vascular smooth muscle cells. The cross-talks between the endothelium and perivascular adipose tissues can be assessed ex vivo using mounted blood vessels by a wire myography system. However, optimal settings should be established for arteries derived from animals of different species, ages, genetic backgrounds and/or pathophysiological conditions.

Examination of the length/tension relationships to obtain the normalization factor k 
The amount of stretch applied to a vessel segment influences the extent of the actin-myosin interaction and hence the maximal active force developed. Thus, for every type of blood vessel, determining the amount of stretch needed for maximal active force is required for proper myography studies. Here, normalization of t...

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Assessment of Vascular Tone Responsiveness using Isolated Mesenteric Arteries with a Focus on Modulation by Perivascular Adipose Tissues

The protocol describes the use of wire myography to evaluate the transmural isometric tension of mesenteric arteries isolated from mice, with special consideration of the modulation by factors released from endothelial cells and perivascular adipose tissues.

Altered vascular tone responsiveness to pathophysiological stimuli contributes to the development of a wide range of cardiovascular and metabolic ...

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JoVE Journal

Biology

9.7K Views.  University of Hong Kong. The protocol describes the use of wire myography to evaluate the transmural isometric tension of mesenteric arteries isolated from mice, with special consideration of the modulation by factors released from endothelial cells and perivascular adipose tissues.

Video: Assessment of Vascular Tone Responsiveness using Isolated Mesenteric Arteries with a Focus on Modulation by Perivascular Adipose Tissues

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.

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 ...

Medicine

Assessing Myogenic Response and Vasoactivity In Resistance Mesenteric Arteries Using Pressure Myography

Small resistance arteries constrict and dilate respectively in response to increased or decreased intraluminal pressure; this phenomenon known as myogenic response is a key regulator of local blood flow. In isobaric conditions small resistance arteries develop sustained constriction known as myogenic tone (MT), which is a major determinant of systemic vascular resistance (SVR). Hence, ex vivo&#160;pressurized preparations of small resistance arteries are major tools to study microvascular function in near-physiological states. To achieve this, a freshly isolated intact segment of a small resistance artery (diameter ~260 &#956;m) is mounted onto two small glass cannulas and pressurized. These arterial preparations retain most in vivo characteristics and permit assessment of vascular tone in real-time. Here we provide a detailed protocol for assessing vasoactivity in pressurized small resistance mesenteric arteries from rats; these arteries develop sustained vasoconstriction - approximately 25% of maximal diameter - when pressurized at 70 mmHg. These arterial preparations may be used to study the effect of investigational compounds on relationship between intra-arterial pressure and vasoactivity and determine changes in microvascular function in animal models of various diseases.

Pressure myography is used to assess vasoactivity of small arteries that develop sustained constriction when pressurized. This manuscript provides a detailed protocol to assess in isolated segments of small mesenteric arteries from rats, vasoactivity and the effect of intraluminal pressure on vascular diameter.

Small resistance arteries constrict and dilate respectively in response to increased or decreased intraluminal pressure; this phenomenon known as myogenic ...

Isolating and Using Sections of Bovine Mesenteric Artery and Vein as a Bioassay to Test for Vasoactivity in the Small Intestine

Mammalian gastrointestinal systems are constantly exposed to compounds (desirable and undesirable) that can have an effect on blood flow to and from that system. Changes in blood flow to the small intestine can result in effects on the absorptive functions of the organ. Particular interest in toxins liberated from feedstuffs through fermentative and digestive processes has developed in ruminants as an area where productive efficiencies could be improved. The video associated with this article describes an in vitro bioassay developed to screen compounds for vasoactivity in isolated cross-sections of bovine mesenteric artery and vein using a multimyograph. Once the blood vessels are mounted and equilibrated in the myograph, the bioassay itself can be used: as a screening tool to evaluate the contractile response or vasoactivity of compounds of interest; determine the presence of receptor types by pharmacologically targeting receptors with specific agonists; determine the role of a receptor with the presence of one or more antagonists; or determine potential interactions of compounds of interest with antagonists. Through all of this, data are collected real-time, tissue collected from a single animal can be exposed to a large number of different experimental treatments (an in vitro advantage), and represents vasculature on either side of the capillary bed to provide an accurate picture of what could be happening in the afferent and efferent blood supply supporting the small intestine.

The small intestine is frequently exposed to toxins that can influence blood flow and negatively impact nutrient absorption. Using a multimyograph and mesenteric artery and vein isolates, compounds or toxins of interest can be screened for vasoactivity.

Mammalian gastrointestinal systems are constantly exposed to compounds (desirable and undesirable) that can have an effect on blood flow to and from that ...

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 ...

Surgical Placement of Catheters for Long-term Cardiovascular Exercise Testing in Swine

This protocol describes the surgical procedure to chronically instrument swine and the procedure to exercise swine on a motor-driven treadmill. Early cardiopulmonary dysfunction is difficult to diagnose, particularly in animal models, as cardiopulmonary function is often measured invasively, requiring anesthesia. As many anesthetic agents are cardiodepressive, subtle changes in cardiovascular function may be masked. In contrast, chronic instrumentation allows for measurement of cardiopulmonary function in the awake state, so that measurements can be obtained under quiet resting conditions, without the effects of anesthesia and acute surgical trauma. Furthermore, when animals are properly trained, measurements can also be obtained during graded treadmill exercise.
Flow probes are placed around the aorta or pulmonary artery for measurement of cardiac output and around the left anterior descending coronary artery for measurement of coronary blood flow. Fluid-filled catheters are implanted in the aorta, pulmonary artery, left atrium, left ventricle and right ventricle for pressure measurement and blood sampling. In addition, a 20 G&#160;catheter is positioned in the anterior interventricular vein to allow coronary venous blood sampling.
After a week of recovery, swine are placed on a motor-driven treadmill, the catheters are connected to pressure and flow meters, and swine are subjected to a five-stage progressive exercise protocol, with each stage lasting 3 min. Hemodynamic signals are continuously recorded and blood samples are taken during the last 30 sec of each exercise stage.
The major advantage of studying chronically instrumented animals is that it allows serial assessment of cardiopulmonary function, not only at rest but also during physical stress such as exercise. Moreover, cardiopulmonary function can be assessed repeatedly during disease development and during chronic treatment, thereby increasing statistical power and hence limiting the number of animals required for a study.

Here we present a protocol to assess cardiopulmonary function in awake swine, at rest and during graded treadmill exercise. Chronic instrumentation allows for repeated hemodynamic measurements uninfluenced by cardiodepressive anesthetic agents.

This protocol describes the surgical procedure to chronically instrument swine and the procedure to exercise swine on a motor-driven treadmill. Early ...

The ex vivo Isolated Skeletal Microvessel Preparation for Investigation of Vascular Reactivity

The isolated microvessel preparation is an ex vivo preparation that allows for examination of the different contributions of factors that control vessel diameter, and thus, perfusion resistance1-5. This is a classic experimental preparation that was, in large measure, initially described by Uchida et al.15 several decades ago. This initial description provided the basis for the techniques that was extensively modified and enhanced, primarily in the laboratory of Dr. Brian Duling at the University of Virginia6-8, and we present a current approach in the following pages. This preparation will specifically refer to the gracilis arteriole in a rat as the microvessel of choice, but the basic preparation can readily be applied to vessels isolated from nearly any other tissue or organ across species9-13. Mechanical (i.e., dimensional) changes in the isolated microvessels can easily be evaluated in response to a broad array of physiological (e.g., hypoxia, intravascular pressure, or shear) or pharmacological challenges, and can provide insight into mechanistic elements comprising integrated responses in an intact, although ex vivo, tissue. The significance of this method is that it allows for facile manipulation of the influences on the integrated regulation of microvessel diameter, while also allowing for the control of many of the contributions from other sources, including intravascular pressure (myogenic), autonomic innervation, hemodynamic (e.g., shear stress), endothelial dependent or independent stimuli, hormonal, and parenchymal influences, to provide a partial list. Under appropriate experimental conditions and with appropriate goals, this can serve as an advantage over in vivo or in situ tissue/organ preparations, which do not readily allow for the facile control of broader systemic variables. 
The major limitation of this preparation is essentially the consequence of its strengths. By definition, the behavior of these vessels is being studied under conditions where many of the most significant contributors to the regulation of vascular resistance have been removed, including neural, humoral, metabolic, etc. As such, the investigator is cautioned to avoid over-interpretation and extrapolation of the data that are collected utilizing this preparation. The other significant area of concern with regard to this preparation is that it can be very easy to damage cellular components such as the endothelial lining or the vascular smooth muscle, such that variable source of error can be introduced. It is strongly recommended that the individual investigator utilize appropriate measurements to ensure the quality of the preparation, both at the initiation of the experiment and periodically throughout the course of a protocol.

The ex vivo Isolated Skeletal Microvessel Preparation for Investigation of Vascular Reactivity

An ex vivo preparation is described for isolation of the largest gracilis muscle resistance arterioles for interrogation of both vascular responses to vasoactive stimuli and the assessment of basic structural properties via passive wall mechanics.

The isolated  microvessel preparation is an ex vivo preparation that allows for examination of the different contributions of  factors that control vessel ...

Co-staining Blood Vessels and Nerve Fibers in Adipose Tissue

Recent studies have highlighted the critical role of angiogenesis and sympathetic innervation in adipose tissue remodeling during the development of obesity. Therefore, developing an easy and efficient method to document the dynamic changes in adipose tissue is necessary. Here, we describe a modified immunofluorescent approach that efficiently co-stains blood vessels and nerve fibers in adipose tissues. Compared to traditional and recently developed methods, our approach is relatively easy to follow and more efficient in labeling the blood vessels and nerve fibers with higher densities and less background. Moreover, the higher resolution of the images further allows us to accurately measure the area of the vessels, amount of branching, and length of the fibers by open source software. As a demonstration using our method, we show that brown adipose tissue (BAT) contains higher amounts of blood vessels and nerve fibers compared to white adipose tissue (WAT). We further find that among the WATs, subcutaneous WAT (sWAT) has more blood vessels and nerve fibers compared to epididymal WAT (eWAT). Our method thus provides a useful tool for investigating adipose tissue remodeling.

New blood vessel formation and sympathetic innervation play pivotal roles in adipose tissue remodeling. However, there remain technical issues in visualizing and quantitatively measuring adipose tissue. Here we present a protocol to successfully label and quantitatively compare the densities of blood vessels and nerve fibers in different adipose tissues.

Recent studies have highlighted the critical role of angiogenesis and sympathetic innervation in adipose tissue remodeling during the development of ...

Immunology and Infection

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. ...

Evaluation of Vascular Control Mechanisms Utilizing Video Microscopy of Isolated Resistance Arteries of Rats

This protocol describes the use of in vitro television microscopy to evaluate vascular function in isolated cerebral resistance arteries (and other vessels), and describes techniques for evaluating tissue perfusion using Laser Doppler Flowmetry (LDF) and microvessel density utilizing fluorescently labeled Griffonia simplicifolia (GS1) lectin. Current methods for studying isolated resistance arteries at transmural pressures encountered in vivo and in the absence of parenchymal cell influences provide a critical link between in vivo studies and information gained from molecular reductionist approaches that provide limited insight into integrative responses at the whole animal level. LDF and techniques to selectively identify arterioles and capillaries with fluorescently-labeled GS1 lectin provide practical solutions to enable investigators to extend the knowledge gained from studies of isolated resistance arteries. This paper describes the application of these techniques to gain fundamental knowledge of vascular physiology and pathology in the rat as a general experimental model, and in a variety of specialized genetically engineered &#34;designer&#34; rat strains that can provide important insight into the influence of specific genes on important vascular phenotypes. Utilizing these valuable experimental approaches in rat strains developed by selective breeding strategies and new technologies for producing gene knockout models in the rat, will expand the rigor of scientific premises developed in knockout mouse models and extend that knowledge to a more relevant animal model, with a well understood physiological background and suitability for physiological studies because of its larger size.

This manuscript describes in vitro video microscopy protocols for evaluating vascular function in rat cerebral resistance arteries. The manuscript also describes techniques for evaluating microvessel density with fluorescently labeled lectin and tissue perfusion using Laser Doppler Flowmetry.

This protocol describes the use of in vitro television microscopy to evaluate vascular function in isolated cerebral resistance arteries (and other ...

Measurement of Endothelium-Dependent Vasorelaxation in the Mouse Thoracic Aorta Using Tensometric Small Volume Chamber Myography

Small volume chamber tensometric myography is a commonly used technique to evaluate the vascular contractility of small and large blood vessels in laboratory animals and small arteries isolated from human tissue. The technique allows researchers to maintain isolated blood vessels in a tightly controlled and standardized (near-physiological) setting, with the option of adjusting to various environmental factors, while challenging the isolated vessels with different pharmacological agents that can induce vasoconstriction or vasodilation. The myograph chamber also provides a platform to measure vascular reactivity in response to various hormones, inhibitors, and agonists that may impact the function of smooth muscle and endothelial layers separately or simultaneously. The blood vessel wall is a complex structure consisting of three different layers: the intima (endothelial layer), media (smooth muscle and elastin fibers), and adventitia (collagen and other connective tissue). To gain a clear understanding of the functional properties of each layer, it is critical to have access to an experimental platform and system that would allow for a combinational approach to study all three layers simultaneously. Such an approach demands access to a semi-physiological condition that would mimic the in vivo environment in an ex vivo setting. Small volume chamber tensometric myography has provided an ideal environment to evaluate the impact of environmental cues, experimental variables, or pharmacological agonists and antagonists on vascular properties. For many years, scientists have used the tensometric myograph technique to measure endothelial function and smooth muscle contractility in response to different agents. In this report, a small volume chamber tensometric myograph system is used to measure endothelial function in the isolated mouse aorta. This report focuses on how small volume chamber tensometric myography can be used to evaluate the functional integrity of the endothelium in small segments of a large artery such as the thoracic aorta.

The present protocol describes the concepts and technical application of the tensometric myograph technique using a multi-chamber myograph system in the experimental ex vivo assessment of mouse aortic endothelial function.

Assessment of Vascular Tone Responsiveness using Isolated Mesenteric Arteries with a Focus on Modulation by Perivascular Adipose Tissues

Summary

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Non-invasive Assessment of Microvascular and Endothelial Function

Assessing Myogenic Response and Vasoactivity In Resistance Mesenteric Arteries Using Pressure Myography

Isolating and Using Sections of Bovine Mesenteric Artery and Vein as a Bioassay to Test for Vasoactivity in the Small Intestine

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

Surgical Placement of Catheters for Long-term Cardiovascular Exercise Testing in Swine

The ex vivo Isolated Skeletal Microvessel Preparation for Investigation of Vascular Reactivity

Co-staining Blood Vessels and Nerve Fibers in Adipose Tissue

Assessment of Human Adipose Tissue Microvascular Function Using Videomicroscopy

Evaluation of Vascular Control Mechanisms Utilizing Video Microscopy of Isolated Resistance Arteries of Rats

Measurement of Endothelium-Dependent Vasorelaxation in the Mouse Thoracic Aorta Using Tensometric Small Volume Chamber Myography