Flow Perfusion Research Articles

Data-driven calculation of porous geometry-dependent permeability and fluid-induced wall shear stress within tissue engineering scaffolds

It is commonly known that mechanical stimulation, for example, wall shear stress (WSS), can affect cellular behaviours. In vitro experiments have been performed by applying fluid-induced WSS to investigate the cell physiology and pathology. Porous scaffolds are used in these experiments for housing and facilitating the micro-physical/chemical environment on cells during 3-dimensional (3D) cell culturing. It is known that scaffold porous geometries influence scaffold permeability and internal WSS. Computational simulations are commonly employed to determine the WSS; however, these simulations can be computationally expensive and may not be readily accessible to everyone due to a knowledge gap. To address this limitation, this study proposes an empirical equation for calculating the scaffold permeability based on the Kozeny-Carman equation. The new equation considers the porous geometric features, providing an accurate estimation of the scaffold permeability. Furthermore, the study introduces a new correlation between WSS and permeability, aiming to establish an efficient and precise estimation of internal WSS. This correlation enables efficient estimation of the WSS within porous scaffolds without relying on computationally demanding simulations. Therefore, the output from this study can negate the issues of using computational simulation for determining scaffold permeability and internal WSS under perfusion flow by providing empirical equations.

The cerebral and cardiac effects of Norepinephrine in an experimental cardiac arrest model

IntroductionEpinephrine has been the main drug recommended for decades during cardiopulmonary resuscitation (CPR). But epinephrine’s ß-adrenergic effects might increase myocardial oxygen consumption and may cause arrythmias after ROSC. Norepinephrine has a weaker ß-adrenergic effect and could be useful during CPR. Studies on norepinephrine’s effect on hemodynamic parameters and cerebral perfusion are scarce. This study aimed to assess norepinephrine's hemodynamic impact in an experimental model of cardiac arrest. MethodsAfter an initial dose study to determine the optimal dose, we conducted a prospective randomized study with 19 pigs. After 3 minutes of untreated ventricular fibrillation, animals received boluses of 0.5 mg Epinephrine (EPI) or 1 mg Norepinephrine (NE) every 5 minutes during CPR. Coronary perfusion pressure (CPP), carotid blood flow (CBF) and cerebral perfusion pressure (CePP) were evaluated. ResultsAt baseline, hemodynamic parameters did not differ between the two groups. During CPR, CPP and CBF were similar: 17.3 (12.8; 31.8) in the EPI group vs 16.0 (11.1; 37.7) in the NE group, p = 0.9 and 28.4 (22.0; 54.8) vs 30.8 (12.2; 56.3) respectively, p = 0.9. CePP was not significantly lower during resuscitation in the NE group compared to the EPI group: 12.2 (−8.2; 42.2) vs 7.8 (−2.0; 32.0) p = 0.4. Survival rate was low with only one animal in the EPI group and 2 in the NE group. ConclusionCerebral perfusion pressure, coronary perfusion pressure and carotid blood flow during CPR did not significantly differ between the norepinephrine group and the epinephrine group. Further investigations should evaluate different options such as a continuous NE infusion.

Validation of Human Bone Marrow-derived Mesenchymal Stem Cells and MCF-7 Breast Cancer Cells Co-culture Using a 3D Perfused Biomimetic Microfluidic Platform.

Microfluidic experimental models allow to study the mutual interrelation between tumor development and the microvasculature avoiding animal use and lacking interspecies differences. This study aimed to develop and characterize a 3D tissue culture model employing a two-compartment microfluidic chip-perfused platform to visualize and quantify human bone marrow-derived mesenchymal stem cells (hBM-MSCs) and MCF-7 breast cancer cell-cell interactions in real time. MCF-7 cells were implanted in the tumor chamber and hBM-MSCs were injected into microvascular channels. hBM-MSCs culture media was perfused into microvascular compartments. The microfluidic device was microscopically examined weekly for four weeks. VE- and E-cadherin immunofluorescence validated hBM-MSCs differentiation into endothelial cells and MCF-7 cell tumor formation. hBM-MSCs differentiation was highly heterogeneous along the microvascular channels, due to different perfusion flow. hBM-MSCs lining microvascular channels acquired VE-cadherin positive endothelial phenotype and continuously covered microchannels as an endothelium like layer. MCF-7 cells were constantly grown as spheroidal aggregates and later formed a compact area of E-cadherin-positive tumor cells inside tumor compartment. Our study provides valuable knowledge on the properties of hBM-MSCs as vasculogenesis-supporting cells when co-cultured with MCF-7 cells on a 3D perfused biomimetic microfluidic device. This newly established model may serve as an experimental platform for testing anti-tumor/anti-angiogenic drugs.

Abstract 6790: Breaking barriers: A high-throughput 3D drug discovery platform for ovarian cancer

Abstract Background: Ovarian Cancer (OVCA) is a formidable challenge in oncology and remains the most lethal gynecologic malignancy with many cases (~80%) diagnosed at a late stage with an equally high rate of recurrence. Yet, no established OVCA models exist that faithfully recapitulate the biological complexity of metastatic OVCA. This multidisciplinary team developed a new in vitro high-throughput model that maintains the characteristics of the patient’s tumor including resident immune cells. Key breakthroughs include long term (>21 day) culture of patient-derived microtumors, a functional and perfusable microgel medium (Liquid Like Solids - LLS™), microplates with controlled “pumpless” perfusion of culture media (Darcy Plates™), and integrated in situ imaging. Methods: We designed, fabricated, and validated a new 3D culture device in the standard SBS microplate format (Darcy Plate) that integrates in situ microscopy and perfusion through a bio-conjugated microgel bed (LLS). Patient tumors were collected during debulking surgery, micronized into 1 µl microtumors, suspended in LLS, and plated into the 48-well Darcy Plate. Viability and proliferation were assessed over 21 days in situ using a standard LIVE/DEAD™ kit and EDU staining, respectively. Epithelial OVCA cells and immune cells were identified with immunofluorescence microscopy. Results: Optimal media conditions (HPLM media with 10% FBS, 1% Pen/Strep, 2.5 mg L−1 Amphotericin B, 10 mM HEPES, 0.5 µM A83-01 -TGF-β inhibitor-, and ITS) and perfusion flow rates (100 µl/day per well) were identified that resulted in outstanding cell viability after 21 days (~100% - no detectable cell death using LIVE/DEAD™). PAX8 nuclear expression, a marker for epithelial metastatic OVCA, was retained. EDU staining confirmed cell proliferation and CD45 staining revealed retention of viable immune cells on and within the microtumor at 21 days. Drug testing to evaluate tumor response to chemotherapeutic agents, carboplatin, and emerging targeted therapies was performed by dosing the feed-wells at different concentrations and evaluating cell death through LIVE/DEAD imaging after 5 days of treatment. Conclusions: OVCA is a challenging disease with understudied biological complexity and extensive metastatic involvement. This study demonstrates that drug screening with 3D microtumors has important clinical implications and provides a unique opportunity to evaluate drug responses and personalized treatment strategies. These patient-derived microtumors retain crosstalk between diverse cell populations and the tumor microenvironment, which increases the likelihood of identifying effective therapies and drug candidates. This system retains patient-specific tumor heterogeneity and microenvironmental complexity of OVCA, offering a promising platform for drug screening, high-throughput assays, biomarker discovery, and ultimately improving treatment outcomes. Citation Format: Erin George, Diego I. Pedro, Alfonso Pepe, Angie M. Rivera, Ryan A. Smolchek, Jack E. Famiglietti, W. Gregory Sawyer. Breaking barriers: A high-throughput 3D drug discovery platform for ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6790.

O242: Prolonged subnormothermic acellular machine perfusion of human kidneys

Abstract Introduction Prolonged periods of ex vivo perfusion are required to effectively deliver regenerative therapies directly to a kidney before transplantation. This provides time to start repair processes and reduce the likelihood of early graft dysfunction. The aim of this study was to assess the capability of extending the preservation interval using subnormothermic acelllular machine perfusion (SNAP). Methods After a period of static cold storage, 12 human kidneys declined for transplantation were perfused with an oxygenated human serum albumin-based solution at 32°C for 6, 12 or 24h (n=4 per group). After preservation all kidneys were reperfused with a red blood cell-based solution at 37°C for 4h for assessment. Results Functional parameters remained stable during SNAP in all kidneys. However, the perfusate flow rate was significantly lower in the 24h group (24h 166±45, 12h 266±45, 6h 214±36 mL/min/100g; P=0.008). After reperfusion, levels of urinary neutrophil gelatinase-associated lipocalin (uNGAL), insulin-like growth factor binding protein 7 (IGFBP7) and liver-type fatty acid-binding protein (L-FABP) were similar between groups (P>0.05). Levels of oxygen consumption were significantly lower in 24h kidneys compared to 12h (24h 1.45±0.86, 12h 4.3±1.78 mL/min/100g; P=0.0294). Histological evaluation showed a preserved renal morphology in all kidneys, except for the 24h group which showed a mild increase in tubular and endothelial damage. Conclusion This study demonstrated that human kidneys can be successfully preserved with SNAP for up to 12h. There was some evidence of additional ischaemic injury in the 24h SNAP kidneys which warrants further investigation.

Hemodynamic Impairments of Evaluating Symptomatic Intracranial Atherosclerotic Stenosis using Quantitative Flow Ratio on Digital Subtraction Angiography : AComparison with Computed Tomography Perfusion, MRI and Fractional Flow Reserve.

Cerebral hemodynamics are important for the management of intracranial atherosclerotic stenosis (ICAS). The quantitative flow ratio (QFR) is anovel angiography-derived index for assessing the functional relevance of ICAS without pressure wires and adenosine. Good diagnostic yield with the hyperemic fractional flow reserve (FFR) have been reported, while data on the comparison of QFR to FFR are scarce. In this prospective study 56patients with anterior circulation symptomatic ICAS who received endovascular treatment were included. The new method of computing QFR from asingle angiographic view, i.e., the Murray law-based QFR (μQFR), was applied to the examined vessels. An artificial intelligence algorithm was developed to realize the automatic delineation of vascular contour. Pressure gradients were measured before and after treatment within the lesion vessel using apressure guidewire and the FFR was calculated. There was agood correlation between μQFR and FFR. Preoperative FFR predicted DWI watershed infarction (FFR optimal cut-off level: 0.755). Preoperative μQFR predicted DWI watershed infarction (μQFR optimal cut-off level: 0.51). Preoperative FFR predicted CTP hypoperfusion (FFR best predictive value: 0.62). Preoperative μQFR predicted CTP hypoperfusion (μQFR best predictive value: 0.375). The μQFR based on DSA images can be used as an indicator to assess the functional status of the lesion in patients with ICAS.

Evaluation of rabbit adipose derived stem cells fate in perfused multilayered silk fibroin composite scaffold for Osteochondral repair.

Development of osteochondral tissue engineering approaches using scaffolds seeded with stem cells in association with mechanical stimulations has been recently considered as a promising technique for the repair of this tissue. In this study, an integrated and biomimetic trilayered silk fibroin (SF) scaffold containing SF nanofibers in each layer was fabricated. The osteogenesis and chondrogenesis of stem cells seeded on the fabricated scaffolds were investigated under a perfusion flow. 3-Dimethylthiazol-2,5-diphenyltetrazolium bromide assay showed that the perfusion flow significantly enhanced cell viability and proliferation. Analysis of gene expression by stem cells revealed that perfusion flow had significantly upregulated the expression of osteogenic and chondrogenic genes in the bone and cartilage layers and downregulated the hypertrophic gene expression in the intermediate layer of the scaffold. In conclusion, applying flow perfusion on the prepared integrated trilayered SF-based scaffold can support osteogenic and chondrogenic differentiation for repairing osteochondral defects.

Comparison of machine learning-based CT fractional flow reserve with cardiac MR perfusion mapping for ischemia diagnosis in stable coronary artery disease.

To compare the diagnostic performance of machine learning (ML)-based computed tomography-derived fractional flow reserve (CT-FFR) and cardiac magnetic resonance (MR) perfusion mapping for functional assessment of coronary stenosis. Between October 2020 and March 2022, consecutive participants with stable coronary artery disease (CAD) were prospectively enrolled and underwent coronary CTA, cardiac MR, and invasive fractional flow reserve (FFR) within 2weeks. Cardiac MR perfusion analysis was quantified by stress myocardial blood flow (MBF) and myocardial perfusion reserve (MPR). Hemodynamically significant stenosis was defined as FFR ≤ 0.8 or > 90% stenosis on invasive coronary angiography (ICA). The diagnostic performance of CT-FFR, MBF, and MPR was compared, using invasive FFR as a reference. The study protocol was completed in 110 participants (mean age, 62years ± 8; 73 men), and hemodynamically significant stenosis was detected in 36 (33%). Among the quantitative perfusion indices, MPR had the largest area under receiver operating characteristic curve (AUC) (0.90) for identifying hemodynamically significant stenosis, which is in comparison with ML-based CT-FFR on the vessel level (AUC 0.89, p = 0.71), with comparable sensitivity (89% vs 79%, p = 0.20), specificity (87% vs 84%, p = 0.48), and accuracy (88% vs 83%, p = 0.24). However, MPR outperformed ML-based CT-FFR on the patient level (AUC 0.96 vs 0.86, p = 0.03), with improved specificity (95% vs 82%, p = 0.01) and accuracy (95% vs 81%, p < 0.01). ML-based CT-FFR and quantitative cardiac MR showed comparable diagnostic performance in detecting vessel-specific hemodynamically significant stenosis, whereas quantitative perfusion mapping had a favorable performance in per-patient analysis. ML-based CT-FFR and MPR derived from cardiac MR performed well in diagnosing vessel-specific hemodynamically significant stenosis, both of which showed no statistical discrepancy with each other. • Both machine learning (ML)-based computed tomography-derived fractional flow reserve (CT-FFR) and quantitative perfusion cardiac MR performed well in the detection of hemodynamically significant stenosis. • Compared with stress myocardial blood flow (MBF) from quantitative perfusion cardiac MR, myocardial perfusion reserve (MPR) provided higher diagnostic performance for detecting hemodynamically significant coronary artery stenosis. • ML-based CT-FFR and MPR from quantitative cardiac MR perfusion yielded similar diagnostic performance in assessing vessel-specific hemodynamically significant stenosis, whereas MPR had a favorable performance in per-patient analysis.

PET-determined myocardial perfusion and flow in coronary artery disease characterization

Positron emission tomography (PET) myocardial perfusion imaging in conjunction with tracer-kinetic modeling enables the concurrent assessment of myocardial perfusion and regional myocardial blood flow (MBF) of the left ventricle in absolute terms in milliliters per gram per minute (mL/g/min). The non-invasive quantification of MBF during pharmacologically induced hyperemia, at rest, and corresponding myocardial flow reserve (MFR) opens a new avenue for the identification and characterization of classical or endogen type of coronary microvascular dysfunction (CMD) as functional substrate for microvascular angina in patients with non-obstructive coronary artery disease (CAD) and/or no CAD at all. Further, PET-MBF quantification expands the scope of conventional myocardial perfusion imaging from the identification of advanced, and flow-limiting, epicardial CAD to early stages of atherosclerosis and/or CMD. Adding MBF assessment to myocardial perfusion may also reliably unravel diffuse ischemia owing to significant left main stenosis and/or multivessel CAD, commonly confirmed by peak stress transient ischemic cavity dilation of the left ventricle during maximal vasomotor stress compared to rest on gated PET images. Owing to high spatial and contrast resolution in conjunction with photon-attenuation free myocardial perfusion PET images, PET is preferentially used for CAD detection in advanced obesity and women with pronounced breast habitus. With increasing clinical use of cardiac PET perfusion and MBF assessment, individualized, and image-guided cardiovascular treatment decisions in CAD patients is likely to ensue, while its translation into improved cardiovascular outcome remains to be investigated.

Deep Learning for Perfusion Cerebral Blood Flow (CBF) and Volume (CBV) Predictions and Diagnostics

Dynamic susceptibility contrast magnetic resonance perfusion (DSC-MRP) is a non-invasive imaging technique for hemodynamic measurements. Various perfusion parameters, such as cerebral blood volume (CBV) and cerebral blood flow (CBF), can be derived from DSC-MRP, hence this non-invasive imaging protocol is widely used clinically for the diagnosis and assessment of intracranial pathologies. Currently, most institutions use commercially available software to compute the perfusion parametric maps. However, these conventional methods often have limitations, such as being time-consuming and sensitive to user input, which can lead to inconsistent results; this highlights the need for a more robust and efficient approach like deep learning. Using the relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) perfusion maps generated by FDA-approved software, we trained a multistage deep learning model. The model, featuring a combination of a 1D convolutional neural network (CNN) and a 2D U-Net encoder-decoder network, processes each 4D MRP dataset by integrating temporal and spatial features of the brain for voxel-wise perfusion parameters prediction. An auxiliary model, with similar architecture, but trained with truncated datasets that had fewer time-points, was designed to explore the contribution of temporal features. Both qualitatively and quantitatively evaluated, deep learning-generated rCBV and rCBF maps showcased effective integration of temporal and spatial data, producing comprehensive predictions for the entire brain volume. Our deep learning model provides a robust and efficient approach for calculating perfusion parameters, demonstrating comparable performance to FDA-approved commercial software, and potentially mitigating the challenges inherent to traditional techniques.

Effects of cerium oxide nanoenzyme-gelatin methacrylate anhydride hydrogel in the repair of infected full-thickness skin defect wounds in mice

Objective: To investigate the effects of cerium oxide nanoenzyme-gelatin methacrylate anhydride (GelMA) hydrogel (hereinafter referred to as composite hydrogel) in the repair of infected full-thickness skin defect wounds in mice. Methods: This study was an experimental study. Cerium oxide nanoenzyme with a particle size of (116±9) nm was prepared by hydrothermal method, and GelMA hydrogel with porous network structure and good gelling performance was also prepared. The 25 μg/mL cerium oxide nanoenzyme which could significantly promote the proliferation of human skin fibroblasts and had high superoxide dismutase activity was screened out. It was added to GelMA hydrogel to prepare composite hydrogel. The percentage of cerium oxide nanoenzyme released from the composite hydrogel was calculated after immersing it in phosphate buffer solution (PBS) for 3 and 7 d. The red blood cell suspension of mice was divided into PBS group, Triton X-100 group, cerium oxide nanoenzyme group, GelMA hydrogel group, and composite hydrogel group, which were treated with corresponding solution. The hemolysis of red blood cells was detected by microplate reader after 1 h of treatment. The bacterial concentrations of methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli were determined after being cultured with PBS, cerium oxide nanoenzyme, GelMA hydrogel, and composite hydrogel for 2 h. The sample size in all above experiments was 3. Twenty-four 8-week-old male BALB/c mice were taken, and a full-thickness skin defect wound was prepared in the symmetrical position on the back and infected with MRSA. The mice were divided into control group without any drug intervention, and cerium oxide nanoenzyme group, GelMA hydrogel group, and composite hydrogel group applied with corresponding solution, with 6 mice in each group. The wound healing was observed on 3, 7, and 14 d after injury, and the remaining wound areas on 3 and 7 d after injury were measured (the sample size was 5). The concentration of MRSA in the wound exudation of mice on 3 d after injury was measured (the sample size was 3), and the blood flow perfusion in the wound of mice on 5 d after injury was observed using a laser speckle flow imaging system (the sample size was 6). On 14 d after injury, the wound tissue of mice was collected for hematoxylin-eosin staining to observe the newly formed epithelium and for Masson staining to observe the collagen situation (the sample size was both 3). Results: After immersion for 3 and 7 d, the release percentages of cerium oxide nanoenzyme in the composite hydrogel were about 39% and 75%, respectively. After 1 h of treatment, compared with that in Triton X-100 group, the hemolysis of red blood cells in PBS group, GelMA hydrogel group, cerium oxide nanoenzyme group, and composite hydrogel group was significantly decreased (P<0.05). Compared with that cultured with PBS, the concentrations of MRSA and Escherichia coli cultured with cerium oxide nanoenzyme, GelMA hydrogel, and composite hydrogel for 2 h were significantly decreased (P<0.05). The wounds of mice in the four groups were gradually healed from 3 to 14 d after injury, and the wounds of mice in composite hydrogel group were all healed on 14 d after injury. On 3 and 7 d after injury, the remaining wound areas of mice in composite hydrogel group were (29±3) and (13±5) mm2, respectively, which were significantly smaller than (56±12) and (46±10) mm2 in control group and (51±7) and (38±8) mm2 in cerium oxide nanoenzyme group (with P values all <0.05), but was similar to (41±5) and (24±9) mm2 in GelMA hydrogel group (with P values both >0.05). On 3 d after injury, the concentration of MRSA on the wound of mice in composite hydrogel group was significantly lower than that in control group, cerium oxide nanoenzyme group, and GelMA hydrogel group, respectively (with P values all <0.05). On 5 d after injury, the volume of blood perfusion in the wound of mice in composite hydrogel group was significantly higher than that in control group, cerium oxide nanoenzyme group, and GelMA hydrogel group, respectively (P<0.05). On 14 d after injury, the wound of mice in composite hydrogel group basically completed epithelization, and the epithelization was significantly better than that in the other three groups. Compared with that in the other three groups, the content of collagen in the wound of mice in composite hydrogel group was significantly increased, and the arrangement was also more orderly. Conclusions: The composite hydrogel has good biocompatibility and antibacterial effect in vivo and in vitro. It can continuously sustained release cerium oxide nanoenzyme, improve wound blood perfusion in the early stage, and promote wound re-epithelialization and collagen synthesis, therefore promoting the healing of infected full-thickness skin defect wounds in mice.

Validation of resting full-cycle ratio and diastolic pressure ratio with [15O]H2O positron emission tomography myocardial perfusion

Fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) are invasive techniques used to evaluate the hemodynamic significance of coronary artery stenosis. These methods have been validated through perfusion imaging and clinical trials. New invasive pressure ratios that do not require hyperemia have recently emerged, and it is essential to confirm their diagnostic efficacy. The aim of this study was to validate the resting full-cycle ratio (RFR) and the diastolic pressure ratio (dPR), against [15O]H2O positron emission tomography (PET) imaging. A total of 129 symptomatic patients with an intermediate risk of coronary artery disease (CAD) were included. All patients underwent cardiac [15O]H2O PET with quantitative assessment of resting and hyperemic myocardial perfusion. Within a 2 week period, coronary angiography was performed. Intracoronary pressure measurements were obtained in 320 vessels and RFR, dPR, and FFR were computed. PET derived regional hyperemic myocardial blood flow (hMBF) and myocardial perfusion reserve (MPR) served as reference standards. In coronary arteries with stenoses (43%, 136 of 320), the overall diagnostic accuracies of RFR, dPR, and FFR did not differ when PET hyperemic MBF < 2.3 ml min−1 (69.9%, 70.6%, and 77.1%, respectively) and PET MPR < 2.5 (70.6%, 71.3%, and 66.9%, respectively) were considered as the reference for myocardial ischemia. Non-significant differences between the areas under the receiver operating characteristic (ROC) curve were found between the different indices. Furthermore, the integration of FFR with RFR (or dPR) does not enhance the diagnostic information already achieved by FFR in the characterization of ischemia via PET perfusion. In conclusion, the novel non-hyperemic pressure ratios, RFR and dPR, have a diagnostic performance comparable to FFR in assessing regional myocardial ischemia. These findings suggest that RFR and dPR may be considered as an FFR alternative for invasively guiding revascularization treatment in symptomatic patients with CAD.

A paintbrush for delivery of nanoparticles and molecules to live cells with precise spatiotemporal control

Delivery of very small amounts of reagents to the near-field of cells with micrometer spatial precision and millisecond time resolution is currently out of reach. Here we present μkiss as a micropipette-based scheme for brushing a layer of small molecules and nanoparticles onto the live cell membrane from a subfemtoliter confined volume of a perfusion flow. We characterize our system through both experiments and modeling, and find excellent agreement. We demonstrate several applications that benefit from a controlled brush delivery, such as a direct means to quantify local and long-range membrane mobility and organization as well as dynamical probing of intercellular force signaling.

Wide dynamic range measurement of blood flow in vivo using laser speckle contrast imaging.

Laser speckle contrast imaging (LSCI) is a real-time wide-field technique that is applied to visualize blood flow in biomedical applications. However, there is currently a lack of relevant research to demonstrate that it can measure velocities over a wide dynamic range (WDR), which is critical for monitoring much higher and more pulsatile blood flow in larger size myocardial vessels, such as the coronary artery bypass graft, and visualizing the spatio-temporal evolution of myocardial blood flow perfusion in cardiac surgery. We aim to demonstrate that the LSCI technique enables measuring velocities over a WDR from phantom experiments to animal experiments. In addition, LSCI is preliminarily applied to imaging myocardial blood flow distribution in vivo on rabbits. Phantom and animal experiments are performed to verify that the LSCI method has the ability to measure blood velocities over a wide range. Our method is also validated by transit time flow measurement, which is the gold standard for blood flow measurement in cardiac surgery. Our method is demonstrated to measure the blood flow over a wide range from 0.2 to . To validate the phantom results, the varying blood flow rate from 0 to is detected in the rat carotid artery. Additionally, our technique also obtains blood flow maps of different myocardial vessels, such as superficial large/small veins, veins surrounded by fat, and myocardial deeper arteriole. Our study has the potential to visualize the spatio-temporal evolution of myocardial perfusion in coronary artery bypass grafting, which would be of great benefit for future research in the life sciences and clinical medicine.

Validation of a C57/BL6J mouse model of focal cerebral ischemia established by electrocoagulation of the middle cerebral artery

To modify the method for establishing mouse models of middle cerebral artery occlusion (MCAO)-induced focal cerebral ischemia using electrocoagulation. Forty-six C57/BL6J male mice were divided into MCAO model group (n=34) and sham-operated group (n=12). In the model group, MCAO was induced by permanent coagulation of the right middle cerebral artery (MCA) using a coagulator, and cerebral blood flow perfusion was monitored before and at 20 min and 1 day after modeling. Neurological deficits of the mice at 1, 7, and 14 days after modeling were evaluated using Longa score, mNSS score, beam walking test, cylinder test and corner test. TTC staining was used to measure the cerebral infarct size, and Western blotting was performed to detect the expressions of BDNF, GFAP and DCX proteins in the ischemic cortex. The mice in the model group showed significantly reduced cerebral blood flow in the MCA on the ischemic side and obvious neurological deficits with increased forelimb use asymmetry on days 1, 7 and 14 after modeling (P < 0.05). In the cerebral cortex on the ischemic side of the model mice, the expressions of GFAP and DCX increased significantly at 1, 7, and 14 days (P < 0.05) and the expression of BDNF increased at 1 day after modeling ischemia (P < 0.05). We successfully prepared mouse models of MCAO using a modified method by changing the electrocoagulation location from the distal location of the junction between the MCA and the inferior cerebral vein to a 2 mm segment medial to the junction between the MCA and the olfactory bundle.

Analysis of transjugular intrahepatic portosystemic shunt by hemodynamic simulation.

Transjugular intrahepatic portosystemic shunt (TIPS), which artificially creates a portocaval shunt to reduce portal venous pressure, has gradually become the primary treatment for portal hypertension (PH). However, there is no prefect shunting scheme in TIPS to balance the occurrence of postoperative complications and effective haemostasis. To construct cirrhotic PH models and compare different shunting schemes in TIPS. Three cases of cirrhotic PH with different liver volumes were selected for enhanced computed tomography scanning. The models for different shunting schemes were created using Mimics software, and following FLUENT calculation, all the models were imported into the software computational fluid dynamic-post for processing. In each shunting scheme, the differences in portal vein pressure, hepatic blood perfusion and blood flow from the superior mesenteric vein in the shunt tract were compared. The coefficient G was adapted to evaluate the advantages and disadvantages. (1)Concerning the precise location of the shunt tract, the wider the diameter of the shunt tract, the lower the pressure of the portal vein and the lesser the hepatic blood perfusion. Meanwhile, the pressure drop objective was not achieved with the 6 mm-diameter shunting scheme. (2)The 8 mm-diameter shunting scheme through the left portal vein (LPV) had the highest coefficient G. The 8 mm-diameter shunting scheme through the LPV may demonstrate a superior effect and prognosis in TIPS procedures.

Ultrasound microvascular flow imaging: evaluating fetal mesenteric blood flow and predicting postnatal surgery in meconium peritonitis

Objective This study explored the characteristics of fetal mesenteric blood flow perfusion across various gestational weeks and evaluated the efficacy of Microvascular Flow (MV-Flow) imaging technology in assessing intestinal wall blood flow in fetuses with meconium peritonitis (MP). Method In this retrospective study, we analyzed 35 fetuses with MP and 160 healthy fetuses. We examined the correlation between the Vascular Index (VI) of mesenteric perfusion and gestational age, conducted an analysis comparing MP operative and non-operative groups, and developed a predictive model for surgical intervention. Results The VI value demonstrated no significant change with increasing gestational age (correlation coefficient = 0.005, p = 0.946). For healthy fetuses, VI ranged approximately from 34.66% to 67.26% using the automatic ellipse method. The MP operative group exhibited significantly more cesarean deliveries (100% vs. 52.9%, p = 0.003), shorter gestational periods (34.76 ± 2.16 weeks vs. 37.48 ± 1.55 weeks, p < 0.001), lower birth weights (2762.14 ± 452.76 g vs. 3225.88 ± 339.98 g, p = 0.003), more persistent ascites (92.9% vs. 52.9%, p = 0.021), more frequent intestinal wall echo reductions (57.1% vs. 5.9%, p = 0.004), and lower VI (18.57 ± 5.51% vs. 39.41 ± 7.02%, p < 0.001). A predictive model was established: Logit (P)=8.86 - (0.37* VI) + (1.49* ascites), yielding an area under the curve of 0.857, with 78.6% sensitivity and 88.2% specificity. The VI value was significantly associated with the need for postnatal surgery (OR = 0.689, 95% confidence interval: 0.511 − 0.929, p = 0.015). A Receiver Operating Characteristic curve analysis for VI in predicting postnatal surgery showed an area under the curve of 0.971, with an optimal cutoff value of 35%, achieving 91% sensitivity and 94.4% specificity. Conclusion MV-Flow imaging effectively quantified fetal bowel wall blood flow perfusion. There was no significant change in VI across different gestational weeks. Significantly lower VI values in MP fetuses indicated an increased risk of intestinal wall necrosis and the potential need for postnatal surgical intervention.

Comparison of dual-bolus versus dual-sequence techniques for determining myocardial blood flow and myocardial perfusion reserve by cardiac magnetic resonance stress perfusion: From the Automated Quantitative analysis of myocardial perfusion cardiac Magnetic Resonance Consortium

BackgroundQuantitative stress cardiac magnetic resonance (CMR) can be performed using the dual sequence (DS) technique or dual bolus (DB) method. It is unknown if DS and DB produce similar results for myocardial blood flow (MBF) and myocardial perfusion reserve (MPR). The study objective is to investigate if there are any differences between DB and DS derived MBF and MPR. MethodsRetrospective observational study with 168 patients underwent stress CMR. Dual bolus and dual sequence methods were simultaneously performed on each patient on the same day. Global and segmental stress MBF and rest MBF values were collected. ResultsUsing Bland-Altman analysis, segmental and global stress MBF values were higher in DB than DS (0.22 + 0.60ml/g/min, p<0.001 and 0.20 + 0.48ml/g/min, p=0.005 respectively) with strong correlation (r = 0.81, p < 0.001 for segmental and r = 0.82, p < 0.001 for global). In rest MBF, segmental and global DB values were higher than by DS (0.15 + 0.51ml/g/min, p<0.001 and 0.14 + 0.36ml/g/min, p=0.011 respectively) with strong correlation (r = 0.81, p < 0.001 and r = 0.77, p < 0.001). Mean difference between MPR by DB and DS was -0.02 + 0.68ml/g/min (p=0.758) for segmental values and -0.01 + 0.49ml/g/min (p=0.773) for global values. MPR values correlated strongly as well in both segmental and global, both (r = 0.74, p < 0.001) and (r = 0.75, p < 0.001) respectively. ConclusionsThere is very good correlation between DB and DS derived MBF and MPR values. However, there are significant differences between DB and DS derived global stress and rest MBF. Whilst MPR values did not show statistically significant differences between DB and DS methods.

Investigating the impact of the interstitial fluid flow and hypoxia interface on cancer transcriptomes using a spheroid-on-chip perfusion system.

Solid tumours are complex and heterogeneous systems, which exist in a dynamic biophysical microenvironment. Conventional cancer research methods have long relied on two-dimensional (2D) static cultures which neglect the dynamic, three-dimensional (3D) nature of the biophysical tumour microenvironment (TME), especially the role and impact of interstitial fluid flow (IFF). To address this, we undertook a transcriptome-wide analysis of the impact of IFF-like perfusion flow using a spheroid-on-chip microfluidic platform, which allows 3D cancer spheroids to be integrated into extracellular matrices (ECM)-like hydrogels and exposed to continuous perfusion, to mimic IFF in the TME. Importantly, we have performed these studies both in experimental (normoxia) and pathophysiological (hypoxia) oxygen conditions. Our data indicated that gene expression was altered by flow when compared to static conditions, and for the first time showed that these gene expression patterns differed in different oxygen tensions, reflecting a differential role of spheroid perfusion in IFF-like flow in tumour-relevant hypoxic conditions in the biophysical TME. We were also able to identify factors primarily linked with IFF-like conditions which are linked with prognostic value in cancer patients and therefore could correspond to a potential novel biomarker of IFF in cancer. This study therefore highlights the need to consider relevant oxygen conditions when studying the impact of flow in cancer biology, as well as demonstrating the potential of microfluidic models of flow to identify IFF-relevant tumour biomarkers.

Flow-induced fabrication of ZnO nanostructures in pillar-arrayed microchannels.

The emergence of microfluidic devices integrated with nanostructures enables highly efficient, flexible and controllable biosensing, among which zinc oxide (ZnO) nanostructure-based fluorescence detection has been demonstrated to be a promising methodology due to its high electrical point and unique fluorescence enhancement properties. The optimization of microfluidic synthesis of ZnO nanostructures for biosensing on chip has been in demand due to its low cost and high efficiency, but still the flow-induced growth of ZnO nanostructures is not extensively studied. Here, we report a simple and versatile strategy that could manipulate the local flow field by creating periodically arranged micropillars within a straight microchannel. We have explored the effects of perfusion speed and flow direction of seed solution, localized flow variation of growth solution and growth time on the morphology of nanostructures. This provided a comprehensive understanding which governs nanostructure fabrication controlled by flow. The results demonstrated that localized flow in microfluidic devices was essential for the initiation and growth of zinc oxide crystals, enabling precise control over their properties and morphology. Furthermore, a model protein was used to demonstrate the intrinsic fluorescence enhancement of ZnO nanostructures as an example to reveal the morphology-related enhancement properties.