Microcirculation最新文献

Objective

Myotoxin injury of skeletal muscle disrupts myofibers and fragments capillaries. Following injury, myofibers and capillaries regenerate in concert; however, it remains unresolved whether myogenesis and angiogenesis are interdependent processes. We tested the hypothesis that myofiber regeneration is required for revascularization.

Methods

To limit myofiber regeneration, satellite cells were depleted by tamoxifen injections (+TMX) in adult Pax7-Cre^ERT2/+; Rosa^DTA/+ (Pax7-DTA) mice; vehicle injections (−TMX) served as controls. Two weeks later, the gluteus maximus muscle was injured by local injection of BaCl₂. Regeneration of myofibers and microvessels was assessed histologically. Microvascular perfusion was evaluated with fluorescent tracers injected into the bloodstream.

Results

Myofiber regeneration was minimal in +TMX. Through 21 days post injury (dpi), microvascular area (CD31 immunostaining) was similar between +TMX and −TMX, with disoriented microvessels prevailing in +TMX. At 7 dpi, fewer capillaries were perfused in +TMX compared to −TMX. At 21 dpi, EC area and capillary perfusion were not different between groups. For +TMX at 28 dpi, distinct regions with fewer perfused microvessels near “ghost” fibers were accompanied by adjacent areas of robust vascularity and clusters of adipocytes.

Conclusions

Following myotoxin injury after satellite cell ablation, angiogenesis ensues without myogenesis, and the microcirculation remodels according to changes in tissue composition.

Objective

This study investigates the effects of hyperglycemia on vascular morphology and hemodynamics during embryogenesis using the chick chorioallantoic membrane (CAM) model.

Methods

We employed a dual-modality, label-free imaging approach, Optical Coherence Tomography Angiography (OCTA) and biospeckle imaging, to evaluate microvascular architecture and real-time flow dynamics in chick embryos subjected to hyperglycemic conditions. Quantitative metrics such as vessel area, branching junctions, lacunarity, and biospeckle contrast were analyzed to assess angiogenic and metabolic responses.

Results

Hyperglycemia caused significant vascular attrition, including a 31% reduction in vessel area, 55% fewer vascular junctions, and a 58% increase in lacunarity, indicating fragmented and simplified networks. Biospeckle imaging revealed reduced blood flow velocities and elevated non-vascular speckle contrast, suggestive of metabolic stress and endothelial apoptosis. These vascular impairments extended to the retina, where hyperglycemic embryos exhibited thinner retinas, smaller lenses, and sparser retinal vasculature.

Conclusion

Our findings demonstrate that embryonic hyperglycemia leads to widespread vascular simplification and hemodynamic dysfunction, driven by oxidative stress and disrupted VEGF signaling. Unlike adult diabetic vasculopathy, the embryonic response involves global, not focal, vascular defects. This work establishes a novel multimodal imaging framework for studying developmental angiogenesis and lays the groundwork for future investigations into therapeutic strategies targeting diabetic embryopathy.

Objectives

The development of hemoglobin-based oxygen carriers (HBOCs) offers a promising alternative to traditional blood transfusions, addressing critical limitations such as the need for cold storage, blood type matching, and a short ex vivo shelf life. HBOCs mimic the oxygen-carrying function of red blood cells without the risk of transfusion-related complications. However, hemoglobin is prone to oxidation when freely circulating in the vasculature, resulting in methemoglobin formation. In this oxidized state, Hb does not transport oxygen, scavenges less nitric oxide, but it is more toxic. As continued research tries to develop effective HBOCs for use in emergency medicine, there needs to be an understanding of the microvascular and toxicological effects of the reduced and oxidized forms of Hb.

Materials and Methods

The study involved Golden Syrian Hamsters instrumented with a dorsal skin window chamber model to observe the acute effects resulting from a hypervolemic infusion (10% of the animal's blood volume) of human Hb [HbFe²⁺ (hHb)] or methemoglobin [HbFe³⁺ (met-hHb)] and lactated Ringer's solution as a volume control. Microhemodynamics, mean arterial pressure, heart rate, blood gases, and blood properties were measured.

Results

Mean arterial pressure (MAP) and heart rate (HR) were both altered; animals infused with hHb saw a significant increase in MAP and a decrease in HR, while animals infused with met-hHb saw a significant decrease in MAP and a decrease in HR. Infusion of hHb induced vasoconstriction and hypertension. However, infusion of met-hHb resulted in increased microvascular diameters compared to baseline, but a reduction in functional capillary density compared to baseline, alongside significant increases in inflammation, specifically in systemic and cardiac markers.

Conclusion

This study illuminates the complex impact of Hb oxidation on microvascular function and inflammation, pivotal to understanding the safety and efficacy of HBOC formulations. Future research should focus on strategies to regulate Hb oxidation to enhance therapeutic benefit and minimize detrimental effects in emergency medicine settings.

Background

Variations in resting pulsatile coronary flow velocity acceleration/deceleration characteristics (dU/dt) with respect to epicardial lesions and coronary microvascular dysfunction (CMD) remain incompletely understood.

Method

The coronary dU/dt pattern was extracted from the first derivative of the intracoronary Doppler velocity signal. Univariable and multivariable models evaluated the relationships between the dU/dt amplitudes, epicardial disease as well as CMD, defined by a blunted coronary flow reserve (CFR) adjusted for the concomitant epicardial disease severity (fractional flow reserve, FFR) yielding the microvascular resistance reserve (MRR). Functional CMD was defined by a blunted MRR (≤ 3.0) but normal hyperemic microvascular resistance (hMR < 2.5) whereas structural CMD was defined by a blunted MRR (≤ 3.0) combined with increased hMR (≥ 2.5). Six major acceleration or deceleration peaks were identified in each cardiac cycle; these were a (amplitude of peak diastolic acceleration), b (amplitude of early diastolic deceleration nadir), c (amplitude of peak diastolic re-acceleration), j (amplitude of end-diastolic deceleration nadir), x (amplitude of peak systolic acceleration), and z (amplitude of end-systolic deceleration nadir) waves.

Results

Functional CMD was associated with amplification of a (β = 55.944, 95% CI [21.112, 90.777], p = 0.002) and × (β = 44.069, 95% CI [20.182, 67.955], p < 0.001), b (β = −34.019, 95% CI [−50.865, −17.173], p < 0.001), j (β = −48.723, 95% CI [−71.272, −26.174], p < 0.001), and z (β = −31.047, 95% CI [−53.596, −8.498], p = 0.007) waves. Structural CMD was associated with blunted a (β = −76.938, 95% CI [−113.125, −40.751], p < 0.001) and j (β = 24.787, 95% CI [1.361, 48.213], p = 0.039).

Conclusion

Epicardial disease severity is minimally associated with alterations in the resting dU/dt pattern, whereas CMD endotypes are associated with distinctively altered intrabeat pulsatility characteristics. Stronger acceleration magnitudes at rest do not indicate a healthier microcirculation or absence of CMD.

Trial Registration

ClinicalTrials.gov (NCT02328820)

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.