Alterations Of Small Arteries Research Articles

Ultrasensitive Photonic Microsystem Enabling Sub-micrometric Monitoring of Arterial Oscillations for Advanced Cardiovascular Studies.

Cardiovascular diseases are the first cause of death globally. Their early diagnosis requires ultrasensitive tools enabling the detection of minor structural and functional alterations in small arteries. Such analyses have been traditionally performed with video imaging-based myographs, which helped to investigate the pathophysiology of the microvessels. Since new vascular questions have emerged, substantial modifications are necessary to improve the performance of imaging and tracking software, reducing the cost and minimizing the microvessel cleaning and manipulation. To address these limitations, we present a photonic microsystem fabricated in polydimethylsiloxane and integrating micro-optical elements and a lightguide-cantilever for sub-micrometric analysis of small arteries (between 125 and 400 μm of basal diameter). This technology enables simultaneous measurement of arterial distension, stiffness, vasomotion, and heartbeat and without the need for advanced imaging system. The microsystem has a limit of detection of 2 μm, five times lower than video imaging-based myographs, is two times more sensitive than them (0.5 μm/mmHg), reduces variability to half and doubles the linear range reported in these myographs. More importantly, it allows the analysis of intact arteries preserving the integrity and function of surrounding tissues. Assays can be conducted in three configurations according to the surrounding tissue: (i) isolated arteries (in vitro) where the surrounding tissue is partially removed, (ii) non-isolated arteries (in vivo) with surrounding tissue partially removed, and (iii) intact arteries in vivo preserving surrounding tissue as well as function and integrity. This technology represents a step forward in the prediction of cardiovascular risk.

ROCK inhibitor, Y-27632, reduces FBS-induced structural alteration in organ-cultured mesenteric artery

Abstract Background Chronic treatment with fetal bovine serum (FBS) causes gradual vasoconstriction, vascular wall thickening, and contractility reduction in organ-cultured vascular tissues. We have previously demonstrated that Rho-associated kinase (ROCK) inhibitors prevent the functional alterations of small arteries in response to the FBS treatment. Here, we tested a further hypothesis that the chronic inhibition of ROCK has a protective effect on FBS-induced structural alterations. Methods To verify the new hypothesis, the rabbit mesenteric arterial rings were cultured in FBS-supplemented culture medium with or without Y-27632, a reversible ROCK inhibitor and then western blot, immunohistochemistry, apoptosis assay, and electron microscopy were performed using organ-cultured arterial rings. Results Chronic treatment with Y-27632 maintained the arterial diameter by preventing FBS-induced gradual arterial constriction during organ culture. Y-27632 also reduced the apoptosis and the loss of contractile myosin and actin filaments of smooth muscle cells. In addition, Y-27632 protected the morphological integrity between the endothelial cell layer and smooth muscle cell layer by preventing endothelial cell detachment and platelet endothelial cell adhesion molecule (PECAM) expression decrement. Conclusions Chronic ROCK inhibition provides protective effects against FBS-stimulated structural in addition to functional alterations of vascular smooth muscle cells and endothelial cells. These results strongly suggest that the RhoA/ROCK signaling is crucial for maintaining the structural and functional phenotypes of vasculature, and hence, chronic ROCK inhibition may provide protective effects on excessive growth factor-related vascular diseases including hypertension and atherosclerosis.

ROCK inhibition prevents fetal serum-induced alteration in structure and function of organ-cultured mesenteric artery

Chronic treatment with fetal bovine serum (FBS) causes contractility reduction, morphological alteration and DNA synthesis in organ-cultured vascular tissues. Here, we tested the hypothesis that chronic inhibition of ROCK has a protective effect on FBS-induced alterations in small arteries. Rabbit mesenteric arterial rings were cultured in FBS-supplemented culture medium with or without Y-27632, a reversible ROCK inhibitor. Chronic Y-27632 treatment prevented FBS-induced gradual arterial constriction, wall thickening, reduced contractility, and increased ROCK-specific MYPT1 Thr853 phosphorylation. Treatment with Y-27632 also prevented decreased eNOS mRNA expression, and reduced acetylcholine-induced relaxation. Sudden application of Y-27632 to pre-cultured rings reduced MYPT1 phosphorylation and re-widened the constricted rings. Chronic treatment with Y-27632, however, rather augmented than reduced the FBS-induced RhoA over-expression, also increased ROCK1 and MYPT1 expression and averted the FBS-induced reduction of MLC expression, suggesting a compensation of inhibited RhoA/ROCK activity. Sudden removal of Y-27632 caused a rebound in MYPT1 phosphorylation and vasoconstriction in rabbit mesenteric artery. To test which ROCK isoform has greater involvement in FBS-induced contraction, haploinsufficient Rock1+/- and Rock2+/- mouse mesenteric arterial rings were subjected to organ-culture. FBS-induced contraction and RhoA over-expression in either heterozygous animal was not different from wild-type animals. These results suggest that FBS-induced contraction is mediated by up-regulation of RhoA and subsequent activation of ROCK. In conclusion, chronic ROCK inhibition produces some effects that protect against FBS-stimulated vasoconstriction and remodeling. There are also negative effects that a sudden withdrawal of ROCK inhibitor might cause a stronger vasoconstriction than before it was used.

Amiloride normalizes arterial pressure in Cyp1a1ren‐2 transgenic rats without significant effects on small artery function

Activation of the vascular and renal epithelial sodium channel (ENaC) may contribute to arterial hypertension. Cyp1a1ren‐2 transgenic rats carry a renin transgene the expression of which can be induced by feeding an inductor. During transgene induction, these rats show high plasma aldosterone and tissue angiotensin II levels. We tested if hypertension is sensitive to amiloride in these rats and if transgen activation causes amiloride‐sensitive alterations in small arteries that may contribute to hypertension. Cyp1a1ren‐2 transgenic rats (n = 6‐8 per group) were randomized to control (ctr), three weeks transgene induction (ind) and three‐weeks transgene induction + amiloride (amil) during the last week. At the end of the experiment, mean arterial pressure (MAP) was 118 ± 2 (ctr); 153 ± 8 (ind) and 118 ± 2 mmHg (amil). With MAP as effective transmural pressure, third order mesenteric and renal arteries did not show differences in lumen diameter. There was no difference in vascular compliance, α1‐adrenoceptor‐ or depolarisation‐induced vasoconstriction and endothelium‐dependent vasodilation. Amiloride‐induced arterial pressure reduction in transgen‐induced rats was accompanied by increased renal sodium excretion. We conclude that amiloride normalizes arterial pressure in Cyp1a1ren2 transgenic rats likely by stimulating renal sodium excretion but without appreciable effects on small artery function.

Relationships between coronary flow vasodilator capacity and small artery remodelling in hypertensive patients.

Arterial hypertension is frequently associated with the presence of structural alterations in small arteries. Moreover, a reduced coronary flow reserve and vasodilator capacity has been observed in essential hypertensive patients, possibly due, at least in part, to microangiopathy of small coronary vessels. The aim of the present study was to evaluate a possible relationship between subcutaneous small artery structure and coronary flow reserve or vasodilator capacity in patients with essential hypertension. A total of 20 patients with mild to moderate essential hypertension were included in the study, and underwent a biopsy of the subcutaneous fat from the gluteal region. Small arteries were dissected and mounted on a micromyograph. The media thickness, the normalized internal diameter and the media:lumen ratio (M/L) were then calculated. In addition, a transesophageal Doppler echocardiographic study, which allows the measurement of coronary flow velocity before and during maximal pharmacological vasodilatation, was performed. Coronary flow reserve (CFR) was measured as the ratio of coronary flow velocity assessed during adenosine infusion and that measured in basal conditions. From blood pressure and coronary flow velocity during adenosine infusion, minimum coronary resistance was calculated. CFR as well as minimum coronary resistance were significantly correlated to both M/L and to normalized internal diameter of subcutaneous small arteries. Our results are consistent with the hypothesis of a generalized remodelling of small arteries in the body, including the coronary circulation; this remodelling may play an important role in the reduction of coronary vasodilator capacity in patients with mild to moderate essential hypertension.

Structural Alterations in Subcutaneous Small Arteries of Normotensive and Hypertensive Patients With Non–Insulin-Dependent Diabetes Mellitus

It is not presently known whether non-insulin-dependent diabetes mellitus (NIDDM) is associated with the presence of structural alterations in small arteries or whether the combination of hypertension and NIDDM may have an additive effect on endothelial dysfunction. Therefore, we investigated subcutaneous small arteries in 12 normotensive subjects (NT group), 18 patients with essential hypertension (EH group), 13 patients with NIDDM, and 11 patients with NIDDM and EH (NIDDM+EH group). Subcutaneous small arteries were evaluated by a micromyographic technique. The internal diameter, the media-to-lumen ratio, remodeling and growth indices, and the collagen-to-elastin ratio were calculated. Concentration-response curves to acetylcholine, bradykinin, the endothelium-independent vasodilator sodium nitroprusside, and endothelin-1 were performed. The media-to-lumen ratio was higher in the EH, NIDDM, and NIDDM+EH groups compared with the NT group. EH patients showed the presence of eutrophic remodeling, whereas NIDDM and NIDDM+EH patients showed 40% to 46% cell growth. The collagen-to-elastin ratio was significantly increased in the EH and NIDDM+EH groups compared with the NT group. The vasodilatation to acetylcholine and bradykinin was similarly reduced in EH, NIDDM, and NIDDM+EH groups compared with the NT group. The contractile responses to endothelin-1 were similarly reduced in EH, NIDDM, and NIDDM+EH patients. Our data suggest that the effects of NIDDM and EH on small artery morphology are quantitatively similar but qualitatively different and that the presence of hypertension in diabetic patients has little additive effect on small artery morphology and none on endothelial dysfunction.