Blood flow-dependent arterial remodelling is facilitated by inflammation but directed by vascular tone

AIMS: Altered blood flow affects vascular tone, attracts inflammatory cells, and leads to microvascular remodelling. We tested the hypothesis that inflammation facilitates the remodelling response, but that vascular tone determines its direction (inward or outward). METHODS AND RESULTS: Mouse mesenteric resistance arteries were ligated to create either increased blood flow or low blood flow in vivo. In vivo microscopy was used to determine changes in vascular tone. Structural remodelling was studied after 2 days, with or without macrophage depletion. In order to characterize the inflammatory response, immunostaining, confocal microscopy, and real-time PCR were used. To address the role of vascular tone in remodelling, arteries were treated with the vasodilator amlodipine during organ culture. Vessels exposed to high blood flow dilated, whereas low flow induced constriction. After 1 day, inflammatory markers showed a complex but remarkably similar increase in expression during high flow and low flow. Both high-flow and low-flow vessels showed an increase in the number of adventitial macrophages. Depletion of macrophages eliminated flow-induced remodelling. Manipulation of vascular tone reversed inward remodelling in response to low blood flow. CONCLUSION: Altered blood flow triggers an inflammatory response that facilitates remodelling. Vascular tone is a crucial determinant of the direction of the remodelling respons

Structure and function of resistance arteries from BB-creatine kinase and ubiquitous Mt-creatine kinase double knockout micess

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Calcium channel blockade prevents pressure-dependent inward remodeling in isolated subendocardial resistance vessels

The capacity for myocardial perfusion depends on the structure of the coronary microvascular bed. Coronary microvessels may adapt their structure to various stimuli. We tested whether the local pressure profile affects tone and remodeling of porcine coronary microvessels. Subendocardial vessels (∼160 μm, n = 53) were cannulated and kept in organoid culture for 3 days under different transvascular pressure profiles: Osc 80: mean 80 mmHg, 60 mmHg peak-peak sine wave pulsation amplitude at 1.5 Hz; St 80: steady 80 mmHg; Osc 40: mean 40 mmHg, 30 mmHg amplitude; St 40: steady 40 mmHg. Under the Osc 80 profile, modest tone developed, reducing the diameter to 81 ± 14% (mean ± SE, n = 6) of the maximal, passive diameter. No inward remodeling was found here, as determined from the passive pressure-diameter relation after 3 days of culture. Under all other profiles, much more tone developed (e.g., Osc 40: to 26 ± 3%, n = 7). In addition, these vessels showed eutrophic (i.e., without a change in wall cross-sectional area) inward remodeling (e.g., Osc 40: passive diameter reduction by 24 ± 3%). The calcium blocker amlodipine induced maintained dilation in St 40 vessels and reversed the 22 ± 3% (n = 6) inward remodeling to 15 ± 3% (n = 8) outward remodeling toward day 3. Vessels required a functional endothelium to maintain structural integrity in culture. Our data indicate that reduction of either mean pressure or pulse pressure leads to microvascular constriction followed by inward remodeling. These effects could be reversed by amlodipine. Although microvascular pressure profiles distal to stenoses are poorly defined, these data suggest that vasodilator therapy could improve subendocardial microvascular function and structure in coronary artery disease. Copyrigh

Supplementary Material for: Smooth Muscle Contractile Plasticity in Rat Mesenteric Small Arteries: Sensitivity to Specific Vasoconstrictors, Distension and Inflammatory Cytokines

Small artery remodeling may involve a shift in the diameter-dependent force generating capacity of smooth muscle cells (SMC). We tested to what extent and under which conditions such contractile plasticity occurs. Rat mesenteric arteries were mounted on isometric myographs. Active diameter-tension relations were determined after application of several stimuli for 16 or 40 h at 40 or 110% of the passive diameter at 100 mm Hg. At 40%, 16-hour incubation with endothelin-1 (ET-1) but not U46619 shifted force capacity towards smaller diameters. Inflammatory cytokines (TNF-α, IL-1β, IFN-γ), TGF-β or serum neither induced such shift nor augmented the effect of ET-1. The ET-1-mediated change was not affected by superoxide dismutase and catalase. Inward matrix remodeling in the presence of ET-1 was slower, occurring after 40 h. Arteries maintained at 110% showed a shift of force capacity to larger diameters, which was prevented by ET-1 but not by U46619. In the active but not the passive state, SMC had altered nuclear lengths after incubation at 40%. These data demonstrate contractile plasticity in small arteries, where chronic strain is an outward drive and specifically ET-1 an inward drive, acting through mechanisms that do not seem to relate to oxidative stress, inflammatory pathways or major reorganization of the SMC

Supplementary Material for: Cerebral Artery Remodeling in Rodent Models of Subarachnoid Hemorrhage

Vasospasm is known to contribute to delayed cerebral ischemia following subarachnoid hemorrhage (SAH). We hypothesized that vasospasm initiates structural changes within the vessel wall, possibly aggravating ischemia and leading to resistance to vasodilator treatment. We therefore investigated the effect of blood on cerebral arteries with respect to contractile activation and vascular remodeling. In vitro experiments on rodent basilar and middle cerebral arteries showed a gradual contraction in response to overnight exposure to blood. After incubation with blood, a clear inward remodeling was found, reducing the caliber of the passive vessel. The transglutaminase inhibitor L682.777 fully prevented this remodeling. Translation of the in vitro findings to an in vivo SAH model was attempted in rats, using both a single prechiasmatic blood injection model and a double cisterna magna injection model, and in mice, using a single prechiasmatic blood injection. However, we found no substantial changes in active or passive biomechanical properties in vivo. We conclude that extravascular blood can induce matrix remodeling in cerebral arteries, which reduces vascular caliber. This remodeling depends on transglutaminase activity. However, the current rodent SAH models do not permit in vivo confirmation of this mechanism

Enhanced interstitial fluid drainage in the hippocampus of spontaneously hypertensive rats

Hypertension is associated with cognitive decline and various forms of dementia, including Alzheimer's disease. In animal models of hypertension, many of Alzheimer's disease characteristics are recapitulated, including brain atrophy, cognitive decline, amyloid beta accumulation and blood brain barrier dysfunction. Removal of amyloid beta and other waste products depends in part on clearance via the brain interstitial fluid (ISF). Here we studied the impact of hypertension on ISF drainage, using spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). At 8 months, high (500 kD) and low (3 kD) fluorescent molecular weight tracers released passively into the hippocampus showed a drastically enhanced spreading in SHR. Tracer spreading was inhomogeneous, with accumulation at ISF-CSF borders, around arteries, and towards the stratum lacunosum moleculare. These locations stained positively for the astrocyte marker GFAP, and aquaporin 4. Despite enhanced dispersion, clearance of tracers was not affected in SHR. In conclusion, these data indicate enhanced bulk flow of ISF in the hippocampus of hypertensive rats. ISF drains along astrocytes towards the cerebrospinal fluid compartment, which leads to sieving of high molecular weight solutes. Sieving may lead to a local increase in the concentration of waste products and potentially promotes the aggregation of amyloid beta