Pericyte constriction underlies capillary derecruitment during hyperemia in the setting of arterial stenosis

Capillary derecruitment distal to a coronary stenosis is implicated as the mechanism of reversible perfusion defect and potential myocardial ischemia during coronary hyperemia; however, the underlying mechanisms are not defined. We tested whether pericyte constriction underlies capillary derecruitment during hyperemia under conditions of stenosis. In vivo two-photon microscopy (2PM) and optical microangiography (OMAG) were used to measure hyperemia-induced changes in capillary diameter and perfusion in wild-type and pericyte-depleted mice with femoral artery stenosis. OMAG demonstrated that hyperemic challenge under stenosis produced capillary derecruitment associated with decreased RBC flux. 2PM demonstrated that hyperemia under control conditions induces 26 ± 5% of capillaries to dilate and 19 ± 3% to constrict. After stenosis, the proportion of capillaries dilating to hyperemia decreased to 14 ± 4% ( P = 0.05), whereas proportion of constricting capillaries increased to 32 ± 4% ( P = 0.05). Hyperemia-induced changes in capillary diameter occurred preferentially in capillary segments invested with pericytes. In a transgenic mouse model featuring partial pericyte depletion, only 14 ± 3% of capillaries constricted to hyperemic challenge after stenosis, a significant reduction from 33 ± 4% in wild-type littermate controls ( P = 0.04). These results provide for the first time direct visualization of hyperemia-induced capillary derecruitment distal to arterial stenosis and demonstrate that pericyte constriction underlies this phenomenon in vivo. These results could have important therapeutic implications in the treatment of exercise-induced ischemia. NEW & NOTEWORTHY In the setting of coronary arterial stenosis, hyperemia produces a reversible perfusion defect resulting from capillary derecruitment that is believed to underlie cardiac ischemia under hyperemic conditions. We use optical microangiography and in vivo two-photon microscopy to visualize capillary derecruitment distal to a femoral arterial stenosis with cellular resolution. We demonstrate that capillary constriction in response to hyperemia in the setting of stenosis is dependent on pericytes, contractile mural cells investing the microcirculation.

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CCR7 ligands stimulate the intranodal motility of T lymphocytes in vivo

Journal of Experimental Medicine ◽

10.1084/jem.20061706 ◽

2007 ◽

Vol 204 (3) ◽

pp. 489-495 ◽

Cited By ~ 228

Author(s):

Tim Worbs ◽

Thorsten R. Mempel ◽

Jasmin Bölter ◽

Ulrich H. von Andrian ◽

Reinhold Förster

Keyword(s):

T Cells ◽

T Cell ◽

T Lymphocytes ◽

Cd4 T Cells ◽

Movement Behavior ◽

Wild Type ◽

Two Photon Microscopy ◽

Two Photon ◽

Systemic Application

In contrast to lymphocyte homing, little is known about molecular cues controlling the motility of lymphocytes within lymphoid organs. Applying intravital two-photon microscopy, we demonstrate that chemokine receptor CCR7 signaling enhances the intranodal motility of CD4+ T cells. Compared to wild-type (WT) cells, the average velocity and mean motility coefficient of adoptively transferred CCR7-deficient CD4+ T lymphocytes in T cell areas of WT recipients were reduced by 33 and 55%, respectively. Both parameters were comparably reduced for WT T lymphocytes migrating in T cell areas of plt/plt mice lacking CCR7 ligands. Importantly, systemic application of the CCR7 ligand CCL21 was sufficient to rescue the motility of WT T lymphocytes inside T cell areas of plt/plt recipients. Comparing the movement behavior of T cells in subcapsular areas that are devoid of detectable amounts of CCR7 ligands even in WT mice, we failed to reveal any differences between WT and plt/plt recipients. Furthermore, in both WT and plt/plt recipients, highly motile T cells rapidly accumulated in the subcapsular region after subcutaneous injection of the CCR7 ligand CCL19. Collectively, these data identify CCR7 and its ligands as important chemokinetic factors stimulating the basal motility of CD4+ T cells inside lymph nodes in vivo.

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Streptolysin S Inhibits Neutrophil Recruitment during the Early Stages of Streptococcus pyogenes Infection

Infection and Immunity ◽

10.1128/iai.00420-09 ◽

2009 ◽

Vol 77 (11) ◽

pp. 5190-5201 ◽

Cited By ~ 41

Author(s):

Ada Lin ◽

Jennifer A. Loughman ◽

Bernd H. Zinselmeyer ◽

Mark J. Miller ◽

Michael G. Caparon

Keyword(s):

Streptococcus Pyogenes ◽

Neutrophil Recruitment ◽

Host Cells ◽

Wild Type ◽

Two Photon Microscopy ◽

Two Photon ◽

Streptolysin S ◽

Early Stages

ABSTRACT In contrast to infection of superficial tissues, Streptococcus pyogenes infection of deeper tissue can be associated with a significantly diminished inflammatory response, suggesting that this bacterium has the ability to both promote and suppress inflammation. To examine this, we analyzed the behavior of an S. pyogenes mutant deficient in expression of the cytolytic toxin streptolysin S (SLS−) and evaluated events that occur during the first few hours of infection by using several models including injection of zebrafish (adults, larvae, and embryos), a transepithelial polymorphonuclear leukocyte (PMN) migration assay, and two-photon microscopy of mice in vivo. In contrast to wild-type S. pyogenes, the SLS− mutant was associated with the robust recruitment of neutrophils and significantly reduced lethal myositis in adult zebrafish. Similarly, the mutant was attenuated in embryos in its ability to cause lethality. Infection of larva muscle allowed an analysis of inflammation in real time, which revealed that the mutant had recruited PMNs to the infection site. Analysis of transepithelial migration in vitro suggested that SLS inhibited the host cells' production of signals chemotactic for neutrophils, which contrasted with the proinflammatory effect of an unrelated cytolytic toxin, streptolysin O. Using two-photon microscopy of mice in vivo, we showed that the extravasation of neutrophils during infection with SLS− mutant bacteria was significantly accelerated compared to infection with wild-type S. pyogenes. Taken together, these data support a role for SLS in the inhibition of neutrophil recruitment during the early stages of S. pyogenes infection.

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Endothelial NMDA receptors mediate activity-dependent brain hemodynamic responses in mice

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1902647116 ◽

2019 ◽

Vol 116 (21) ◽

pp. 10229-10231 ◽

Cited By ~ 11

Author(s):

Adam D. Hogan-Cann ◽

Ping Lu ◽

Christopher M. Anderson

Keyword(s):

Endothelial Cells ◽

Energy Demand ◽

Barrel Cortex ◽

Loss Of Function ◽

Wild Type ◽

Hemodynamic Responses ◽

Two Photon Microscopy ◽

Two Photon ◽

Activity Dependent

Dynamic coupling of blood supply with energy demand is a natural brain property that requires signaling between synapses and endothelial cells. Our previous work showed that cortical arteriole lumen diameter is regulated by N-methyl-d-aspartate receptors (NMDARs) expressed by brain endothelial cells. The purpose of this study was to determine whether endothelial NMDARs (eNMDARs) regulate functional hyperemia in vivo. In response to whisker stimulation, regional cerebral blood flow (rCBF) and hemodynamic responses were assessed in barrel cortex of awake wild-type or eNMDAR loss-of-function mice using two-photon microscopy. Hyperemic enhancement of rCBF and vasodilation throughout the vascular network was observed in wild-type mice. eNMDAR loss of function reduced hyperemic responses in rCBF and plasma flux in individual vessels. Discovery of an endothelial receptor that regulates brain hyperemia provides insight into how neuronal activity couples with endothelial cells.

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In vivo imaging of liver injury and regeneration by functional two-photon microscopy

Zeitschrift für Gastroenterologie ◽

10.1055/s-0036-1597342 ◽

2016 ◽

Vol 54 (12) ◽

pp. 1343-1404

Author(s):

A Ghallab ◽

R Reif ◽

R Hassan ◽

AS Seddek ◽

JG Hengstler

Keyword(s):

Liver Injury ◽

In Vivo Imaging ◽

Two Photon Microscopy ◽

Two Photon

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Sensory Transmission is Bi-directionally Modulated by Astrocytic Ca2+ in Barrel Cortex of Behaving Mice

10.21203/rs.3.rs-199750/v1 ◽

2021 ◽

Author(s):

Simeng Gu ◽

Wei Wang ◽

Kuan Zhang ◽

Rou Feng ◽

Naling Li ◽

...

Keyword(s):

Sensory Input ◽

Barrel Cortex ◽

Synaptic Function ◽

Metabolic Clearance ◽

Sleep State ◽

Two Photon Microscopy ◽

Two Photon ◽

Sensory Transmission

Abstract Different effects of astrocyte during sleep and awake have been extensively studied, especially for metabolic clearance by the glymphatic system, which works during sleep and stops working during waking states. However, how astrocytes contribute to modulation of sensory transmission during sleep and awake animals remain largely unknown. Recent advances in genetically encoded Ca2+ indicators have provided a wealth of information on astrocytic Ca2+, especially in their fine perisynaptic processes, where astrocytic Ca2+ most likely affects the synaptic function. Here we use two-photon microscopy to image astrocytic Ca2+ signaling in freely moving mice trained to run on a wheel in combination with in vivo whole-cell recordings to evaluate the role of astrocytic Ca2+ signaling in different behavior states. We found that there are two kinds of astrocytic Ca2+ signaling: a small long-lasting Ca2+ increase during sleep state and a sharp widespread but short-long-lasting Ca2+ spike when the animal was awake (fluorescence increases were 23.2 ± 14.4% for whisker stimulation at sleep state, compared with 73.3 ± 11.7% for at awake state, paired t-test, p < 0.01). The small Ca2+ transients decreased extracellular K+, hyperpolarized the neurons, and suppressed sensory transmission; while the large Ca2+ wave enhanced sensory input, contributing to reliable sensory transmission in aroused states. Locus coeruleus activation works as a switch between these two kinds of astrocytic Ca2+ elevation. Thus, we show that cortical astrocytes play an important role in processing of sensory input. These two types of events appear to have different pharmacological sources and may play a different role in facilitating the efficacy of sensory transmission.

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