Microcirculation最新文献

Objectives

The amino acid homocysteine (HCY) has been implicated in the pathobiology of several conditions, including spaceflight-associated neuro-ocular syndrome (SANS)—a collection of symptoms affecting near vision in astronauts. Blood-retinal barrier (BRB) and blood–brain barrier (BBB) dysfunctions are implicated in the pathobiology of SANS. Our objective was to assess how HCY affects BRB/BBB permeability and the role of the NLRP3 inflammasome in the modulation of such effects.

Methods

Human brain and retinal microvascular endothelial cells (HBMECs and HRMECs) were treated with 100 μM HCY alone or in conjunction with NLRP3 inflammasome inhibitor MCC950 at 1 μM. The assays performed included fluorometric assays to measure cell viability, an enzyme assay for caspase-1, expression of BRB/BBB tight junction protein zonula occludens-1 (ZO-1) by RT-PCR, and barrier permeability using FITC-dextran.

Results

In HRMECs and HBMECs, HCY-induced endothelial monolayer hyperpermeability significantly (p < 0.05). In HBMECs, the effect was attenuated by MCC950 (p < 0.05). Increased Caspase-1 activity was observed in both cell types following the addition of HCY. Following HCY addition, gene expression results denoting barrier damage were observed, particularly that of ZO-1 (p < 0.05).

Conclusions

HCY induces hyperpermeability in retinal and brain endothelial cells. NLRP3-mediation in HCY-induced microvascular permeability is prominent in brain endothelial cells compared to retinal endothelial cells.

Objective

Synthetic hydrogels that support 3D cell culture are widely used as platforms for modeling disease, such as tissue fibrosis, which leads to mechanical stiffening of the extracellular matrix (ECM). To interrogate how mechanical stiffness of the ECM affects microvascular remodeling, we developed a bioactive poly(ethylene glycol) diacrylate (PEGDA) hydrogel model with tunable stiffness that permits microvascular sprouting.

Methods

Lung explants harvested from healthy and fibrotic mice were cultured ex vivo on PEGDA hydrogels for 7 days. Capillary sprouting from lung segments was evaluated via imaging and secreted angiogenic markers.

Results

Healthy lung explants had decreased sprout formation and length on stiffer hydrogels. The sprouts from fibrotic lung explants, however, were not impacted by hydrogel stiffness. This difference was associated with higher expression of angiogenic markers and matrix remodeling enzymes in the fibrotic lung explants.

Conclusions

Our results suggest a compensation in vasculature derived from fibrotic tissue to matrix mechanics in promoting angiogenic sprouting.

Background

Availability of oxygen (O₂) is essential for life and function of all cells of the human body (n ≈ 10¹³–10¹⁴ cells). COVID-19 patients often have impaired lung function with compromised oxygen uptake, but little is known about microvascular oxygen delivery and tissue oxygenation.

Objectives

Use the Oxygen Delivery Index (ODIN) concept to assess peripheral microvascular regulation and oxygen extraction in COVID-19 patients.

Methods

The ODIN concept includes two technologies (diffuse reflectance spectroscopy—DRS and computer assisted microscopy—CAM) for data acquisition from subepidermal nutritive capillaries. Output parameters are microvascular oxygen saturation (SmvO₂) and functional capillary density (FCD).

Results

Forty patients hospitalized for COVID-19 grouped into early discharge (< 7 days, n = 11), severe (beyond 7 days, n = 24) and non-survivors (n = 5), and healthy controls (n = 23) were examined.

Microvascular oxygen saturation (SmvO₂) and the corresponding O₂ extraction (SaO₂—SmvO₂) was 56% ± 4%/42% ± 9% (mean ± SD) in healthy controls (n = 11), 61 ± 10/37 ± 10 for historic controls (n = 12), significantly different (p < 0.01) as compared with all COVID-19 groups (early discharge: 40% ± 13%/54% ± 13%, severe: 34% ± 15%/60% ± 15%, non-survivors 22% ± 15%/73% ± 16%). FCD expressed as the relative number of red pixels (belonging to a capillary erythrocyte) in a CAM frame were reduced in alle patient groups as compared to historic controls (p < 0⋅05).

Conclusion

Results show skin microvascular dysregulation and tissue hypoxia in patients, indicative of hypoxia also in other tissues. We hypothesize that tissue hypoxia is a cause of reversible and non-reversible long COVID-19 symptoms and of mortality.

Objective

During skin inflammation, inhibition of adhesion of regulatory T cells (Tregs) to the dermal microvascular endothelium leads to exacerbation of inflammation, evidence that the dermal endothelium is a key target of the anti-inflammatory actions of Tregs. The aim of this study was to investigate the capacity of Tregs to control the expression of endothelial adhesion molecules in inflamed and resting skin.

Methods

Treg function was assessed in a two-challenge contact hypersensitivity (CHS) model, measuring dermal adhesion molecule expression via imaging of cleared skin. Treg depletion was achieved using Foxp3^DTR mice.

Results

CHS induced upregulation of E-selectin and ICAM-1 but not P-selectin and VCAM-1. Elimination of Tregs following CHS challenge resulted in exacerbated skin inflammation and enhanced expression of E-selectin, P-selectin and ICAM-1 in the dermal microvasculature. Multiphoton imaging revealed that at this phase of the response, Tregs were enriched near blood vessels and underwent dynamic migration adjacent to the microvasculature. Additionally, in skin that was not undergoing hapten challenge, absence of Tregs also resulted in upregulation of E-selectin and ICAM-1 in skin vessels.

Conclusions

These observations demonstrate that the microvascular endothelium is a target of the anti-inflammatory actions of Tregs in the skin, both during CHS and in steady-state skin.

Neuropeptide Y (NPY) is a sympathetic co-transmitter that mediates vasoconstriction. However, there is evidence that it may also mediate dilation through a nitric oxide (NO)-dependent mechanism.

Objective

We used a swine model to examine how NPY influences cerebral vascular regulation and hypothesized that NPY would elicit both vasoconstrictor and vasodilatory effects, and that such effects would be modulated partially by NO signaling.

Methods

Briefly, cerebral perfusion and blood pressure were monitored during intracarotid saline or NPY infusion (0.1 μg/kg) in the presence and absence of NO synthase (NOS) inhibition (N^G-nitro-l-arginine methyl ester; 0.35 mg/kg/min). Separately, Y1 receptor distribution (immunohistochemistry) and vasomotor responses to intra- and extraluminal NPY under control and NOS inhibition conditions were examined in isolated arteries.

Results

Intracarotid NPY infusions elicited transient dilation that was blocked by NOS inhibition. In isolated pial arteries, distinct populations of NPY-Y1 receptors were observed on both the vascular smooth muscle (VSM) and endothelium. Extraluminal application of NPY elicited vasoconstriction, while intraluminal delivery elicited vasodilation. NOS inhibition enhanced the magnitude of vasoconstriction in isolated pial arteries. Endothelial denudation, Y1 receptor antagonism, and NOS inhibition each blunted NPY-induced vasodilation.

Conclusion

These data suggest both vasoconstrictor and vasodilatory effects of NPY are modulated partially by NO signaling.

Objective

Hypertension is related to the pathogenesis of microvascular dysfunction. Renal denervation is a guideline-endorsed intervention for the management of uncontrolled hypertension. However, the effect of renal denervation on skin capillary density, as assessed by nailfold capillaroscopy, is unknown.

Methods

Individuals with stage I/II uncontrolled hypertensions were enrolled and allocated to either undergo renal denervation or serve as controls. Nailfold capillaroscopy was performed at baseline and at 12 months. Furthermore, the albumin to creatinine ratio (ACR) and office/ambulatory blood pressure (BP) levels were monitored throughout the study.

Results

A total of 45 individuals (28 renal denervation, 17 control) were enrolled in our study. No difference was found in baseline capillary density. At 12 months, all patients had controlled BP, while the denervation arm had a significantly greater number of capillaries, compared with control (90.9 ± 14.0 vs. 82.5 ± 10.6 capillaries/mm²; p = 0.036). However, the change from baseline capillary density was not significantly different between groups (4.6 ± 6.1 vs. 1.39 ± 8.8 capillaries/mm²; p = 0.150). Moreover, the change of ACR was not different between groups (−2.7 ± 13.8 vs. 0.46 ± 5.2; p = 0.365).

Conclusion

In patients with uncontrolled stage I/II hypertension, renal denervation may have a beneficial effect on skin capillary density.

Objective

This study investigates the effects of hemodynamic factors on blood cell suspension flows and their properties in curved microvessels. A parametric study is employed to compare these properties between curved and straight vessels.

Methods

A 3D fluid solver coupled with a cell membrane modeling framework via the immersed boundary method was used to simulate cell-resolved blood flow in straight and curved vessels featuring a 90° bend with moderate curvature.

Results

Blood flow in curved vessels shows lower and higher shear rates in the inner and outer bulk regions, respectively, compared to straight vessels. Asymmetry in hematocrit profiles is linked to less dense suspensions, smaller diameters, and higher Capillary numbers, while the maximum velocity location remains consistent with straight vessels. At physiological shear rates, moderate curvatures, and large diameters, curvature has minimal impact on apparent viscosity. However, diffusivity is elevated at the center of curved vessels compared to straight ones.

Conclusions

This study reveals new insights into blood suspension flows in curved microvessels with a 90° bend, highlighting key differences from straight vessels under certain hemodynamic conditions. These findings lay the groundwork for future research on realistic microvessel geometries and their implications.

Objective

Cell-free hemoglobin (CFH) is released into the circulation during sepsis where it can redox cycle from the ferrous 2+ to ferric 3+ and disrupt endothelial function, but the mechanisms of CF-mediated endothelial dysfunction are unknown. We hypothesized that oxidized CFH induces mitochondrial dysfunction via the mitochondrial permeability transition pore (mPTP) in pulmonary endothelial cells, leading to the release of mitochondrial DNA (mtDNA).

Methods

Human lung microvascular endothelial cells were treated with CFH2+/CFH3+. We measured mitochondrial mPTP activation (flow cytometry), network and mass (immunostaining), structure (electron microscopy), mtDNA release (PCR), and oxygen consumption rate (OCR; Seahorse). Plasma from critically ill patients and conditioned cell media were quantified for mtDNA and CFH.

Results

CFH3+ disrupted the mitochondrial network, activated the mPTP (1434 (874–1642) vs. 2302 (1729–2654) mean fluorescent intensity, p = 0.02), increased the spare respiratory capacity (30.61 (29.36–37.78) vs. 7.83 (3.715–10.63) OCR, p = 0.004), and caused the release of mtDNA. CFH was associated with circulating mtDNA (R² = 0.1912, p = 0.0077) in plasma from critically ill patients.

Conclusion

CFH3+, not CFH2+, is the primary driver of CFH-induced lung microvascular mitochondrial dysfunction. Activation of the mPTP and the release of mtDNA are a feature of CFH3+ mediated injury.