How the elastase-induced rabbit aneurysm heals following flow diverter treatment: a histopathological study.

OBJECTIVE: Fibrin deposition is integral to thrombus formation and wound healing. The role of fibrin deposition and subsequent metabolism following flow diversion for aneurysm treatment remains poorly characterized. This study aimed to evaluate the role of fibrin in early thrombus organization after flow diverter treatment. METHODS: Thirty-five elastase-induced aneurysms were induced in New Zealand white rabbits and subjected to endoluminal flow diversion treatment. The device-bearing arteries were harvested at 1, 3, and 6 months postimplantation and processed for histopathological examination, including a modified picro-Mallory stain (Carstairs method) to visualize fibrin and platelets, immunohistochemical targeting of smooth muscle actin (SMA), and H&E staining for conventional morphological evaluation. Quantitative analysis of tissue components was carried out using the Orbit Image Analysis software. The samples were also assessed qualitatively to investigate the morphology and location of fibrin and other thrombus components within the intra-aneurysmal thrombi. Statistical analyses were conducted using R software version 4.3.1. RESULTS: Fibrin constituted 27.9% of the thrombus tissue within the aneurysm sac for aneurysms harvested at 1 month, and this rate was significantly lower in the 3-month group (10.2%, p = 0.018). The proportion of blood cells within the sac was also notably higher in the 1-month group compared with other time points. The primary tissue filling the dome at 1 month (14/15, 93%) was an unorganized thrombus primarily composed of fibrin, platelets, and red blood cells. Conversely, aneurysms harvested at 1 month had the lowest collagen level (25.6%). However, collagen became the dominant tissue component within the aneurysm sac, accounting for 71.8% of tissue in the 3-month group (p = 0.007). There were no differences observed among the examined components between the 3-month and 6-month groups. On qualitative analysis, collagen-producing SMA-positive myofibroblasts were located near or in between fibrin molecules. Healed aneurysms exhibited myofibroblasts, collagen, and a well-organized fibrin network on the aneurysm neck. In contrast, unhealed aneurysms displayed a poorly organized fibrin network with scattered myofibroblasts at the neck area. CONCLUSIONS: These findings indicate that fibrin plays a foundational role in the gradual occlusion of aneurysms after flow diverter treatment. Endovascular approaches that enhance fibrin accumulation could potentially improve aneurysm occlusion rates. Further research is needed to establish the precise role of fibrin in aneurysm occlusion.

WEB shape modifications: angiography-histopathology correlations in rabbits.

BACKGROUND: WEB Shape Modification (WSM) over time is frequent after aneurysm treatment. In this study, we explored the relationship between histopathological changes and angiographic evolution over time in experimental aneurysms in rabbits treated with the Woven EndoBridge (WEB) procedure. METHODS: Quantitative WSM was assessed using flat-panel computed tomography (FPCT) during follow-up by calculating height and width ratio (HR, WR), defined as the ratio between either measurement at an index time point and the measurement immediately after WEB implantation. The index time point varied from 1 day to 6 months. HR and WR were evaluated with angiographic and histopathological assessments of aneurysm healing. RESULTS: Final HR of devices varied from 0.30 to 1.02 and final WR varied from 0.62 to 1.59. Altogether, at least 5% of HR and WR variations were observed in 37/40 (92.5%) and 28/40 (70%) WEB devices, respectively, at the time of final assessment. There was no significant correlation between complete or incomplete occlusion groups and HR or WR (p=0.15 and p=0.43). Histopathological analysis revealed a significant association between WR and aneurysm healing and fibrosis 1 month following aneurysm treatment (both p<0.05). CONCLUSION: Using longitudinal FPCT assessment, we observed that WSM affects both the height and width of the WEB device. No significant association was found between WSM and aneurysm occlusion status. Although presumably a multifactorial phenomenon, the histopathological analysis highlighted a significant association between width variations, aneurysm healing and fibrosis in the first month following aneurysm treatment.

Real-time cell metabolism assessed repeatedly on the same cells via para-hydrogen induced polarization.

Signal-enhanced or hyperpolarized nuclear magnetic resonance (NMR) spectroscopy stands out as a unique tool to monitor real-time enzymatic reactions in living cells. The singlet state of para-hydrogen is thereby one source of spin order that can be converted into largely enhanced signals of e.g. metabolites. Here, we have investigated a parahydrogen-induced polarization (PHIP) approach as a biological assay for in vitro cellular metabolic characterization. Here, we demonstrate the possibility to perform consecutive measurements yielding metabolic information on the same sample. We observed a strongly reduced pyruvate-to-lactate conversion rate (flux) of a Hodgkin's lymphoma cancer cell line L1236 treated with FK866, an inhibitor of nicotinamide phosphoribosyltransferase (NAMPT) affecting the amount of NAD+ and thus NADH in cells. In the consecutive measurement the flux was recovered by NADH to the same amount as in the single-measurement-per-sample and provides a promising new analytical tool for continuous real-time studies combinable with bioreactors and lab-on-a-chip devices in the future.

Safety and Efficacy of Direct Thrombectomy Versus Bridging Therapy in Patients with Acute Ischemic Stroke Eligible for Intravenous Thrombolysis: A Meta-Analysis of Randomized Controlled Trials.

OBJECTIVE: In the present study, we conducted a meta-analysis of reported randomized controlled trials (RCTs) comparing the safety and efficacy of direct thrombectomy (DT) and bridging therapy (BT) for patients eligible for intravenous thrombolysis (IVT). METHODS: A comprehensive search of PubMed, Cochrane Library, EMBASE, and Web of Science up to July 11, 2022 was performed. RCTs comparing DT and BT were included. The relative risk or rate difference and their 95% confidence intervals in a Mantel-Haenszel fixed effects model were used as the effect index of each outcome. The noninferior margin was specified as 80% for the relative risk or -10% for the rate difference. The primary outcome was the proportion of patients with a favorable functional outcome, defined as a modified Rankin scale (mRS) score of 0-2 or a return to baseline at 90 days. Additional efficacy and safety outcomes included successful recanalization at the end of thrombectomy, excellent clinical outcomes (defined as an mRS score of 0-1), death within 90 ± 14 days, symptomatic intracerebral hemorrhage, any type of intracerebral hemorrhage, and clot migration. RESULTS: Six RCTs with 2334 patients were pooled for the meta-analysis. The results showed the noninferiority of DT for favorable functional outcomes, higher successful recanalization rates, and any intracerebral hemorrhage in the BT group, with no statistically significant differences for other outcomes. The risk of bias for all RCTs in our analysis was low. CONCLUSIONS: DT achieved noninferiority to BT for favorable functional outcomes. Patient-level pooled analysis and subgroup analysis are needed to provide more information to distinguish which patients will benefit more from which therapy.

Real-Time Pyruvate Chemical Conversion Monitoring Enabled by PHIP.

In recent years, parahydrogen-induced polarization side arm hydrogenation (PHIP-SAH) has been applied to hyperpolarize [1-13C]pyruvate and map its metabolic conversion to [1-13C]lactate in cancer cells. Developing on our recent MINERVA pulse sequence protocol, in which we have achieved 27% [1-13C]pyruvate carbon polarization, we demonstrate the hyperpolarization of [1,2-13C]pyruvate (∼7% polarization on each 13C spin) via PHIP-SAH. By altering a single parameter in the pulse sequence, MINERVA enables the signal enhancement of C1 and/or C2 in [1,2-13C]pyruvate with the opposite phase, which allows for the simultaneous monitoring of different chemical reactions with enhanced spectral contrast or for the same reaction via different carbon sites. We first demonstrate the ability to monitor the same enzymatic pyruvate to lactate conversion at 7T in an aqueous solution, in vitro, and in-cell (HeLa cells) via different carbon sites. In a second set of experiments, we use the C1 and C2 carbon positions as spectral probes for simultaneous chemical reactions: the production of acetate, carbon dioxide, bicarbonate, and carbonate by reacting [1,2-13C]pyruvate with H2O2 at a high temperature (55 °C). Importantly, we detect and characterize the intermediate 2-hydroperoxy-2-hydroxypropanoate in real time and at high temperature.

A novel cerebrovascular drug-coated balloon catheter for treating symptomatic intracranial atherosclerotic stenosis lesions: Study protocol for a prospective, multicenter, single-arm, target-value clinical trial.

Background: Previous single-center studies have demonstrated that drug-coated balloons (DCBs) may reduce restenosis rates, which is an important factor affecting the prognosis for intracranial interventional therapy. However, currently available cardiac DCBs are not always suitable for the treatment of intracranial atherosclerotic stenosis (ICAS). This study aimed to evaluate the safety and efficacy of a novel DCB catheter designed for patients with severely symptomatic ICAS. Methods: This prospective, multicenter, single-arm, target-value clinical trial was conducted in 9 Chinese stroke centers to evaluate the safety and efficacy of a novel DCB catheter for treating symptomatic severe ICAS. Primary metrics and other indicators were collected and analyzed using SAS version 9.4 (SAS Institute, Cary, NC, USA). Results: A total of 155 patients were enrolled in this study. The preliminary collection of follow-up data has been completed, while data quality control is ongoing. Conclusion: Results of this study demonstrated the patency rate, safety, and effectiveness of a novel on-label paclitaxel DCB designed for the treatment of ICAS. Trial registration: ChiCTR, ChiCTR2100047223. Registered June 11, 2021-Prospective registration, https://www.chictr.org.cn/ChiCTR2100047223.

Evaluation of using a double helical, closed-cell stent-retriever (Skyflow) for thrombectomy procedures in acute arterial occlusion: A preclinical study and a clinical trial.

Background and purpose: Stent retriever thrombectomy is the standard therapeutic approach for ischemic stroke with acute large-vessel occlusion. This study evaluated the safety and efficacy of a new thrombectomy device (Skyflow) in the treatment of acute ischemic stroke. Methods: After an arterial occlusion model was established, stent-retriever thrombectomy was performed. Digital subtraction angiography (DSA) and autopsy were carried out immediately after thrombectomy in six animals in the acute experimental group. Simulated stent-retriever thrombectomy was performed for three animals in the subacute experimental group, and follow-up angiography and vascular pathological examination were assessed 90 days after the operation. In the clinical trial, 192 patients with intracranial anterior circulation large vessel occlusion, within 8 â€‹h of symptom onset, were included to undergo thrombectomy with either Skyflow or Solitaire FR stent retriever. Efficacy and safety endpoints were recorded (including successful reperfusion, favorable clinical outcomes, time from puncture to reperfusion, instrument operation success rates and National Institutes of Health Stroke Scale (NIHSS) scores at 7 days for efficacy endpoints, and symptomatic intracranial hemorrhage (sICH), subarachnoid hemorrhage (SAH) and all-cause mortality rates for safety endpoints). Results: All blood vessels achieved successful recanalization in the animal models. In the clinical trial, successful recanalization was attained in 88.4% of patients of the Skyflow group, which was comparable to that of the Solitaire FR group (82.5%) in the full analysis set of the clinical trial. There were no severe complications on DSA, an animal autopsy, or vessel pathological examination in animal experiments. Additionally, no statistically significant difference was observed between the Skyflow and Solitaire FR groups in the clinical trial regarding the safety endpoints. Conclusion: This study showed that the new Skyflow stent retriever is safe and effective for the treatment of acute large vessel occlusion, as demonstrated in our animal study and human trial.

Safety and efficacy of the SeparGateTM balloon-guiding catheter in neurointerventional surgery: A prospective, multicenter, single-arm clinical trial.

Objective: To evaluate the safety and efficacy of the SeparGate™ balloon-guiding catheter (BGC) for blocking flow and delivering devices in neurointerventional surgery. Method: This prospective multicenter single-arm trial enrolled patients who received BGC adjuvant therapy to provide temporary blood flow arrest of the supra-aortic arch arteries and their branch vessels in interventional therapy. The primary endpoint was immediate procedural success rate in flow arrest, device delivery, and withdrawal. The efficacy endpoints were intraoperative product performance, including rigidity, smoothness, fracture resistance of the catheter wall, catheter push performance, compatibility and radiopaque display, integrity, adhesion thrombus after withdrawal and balloon rupture. The safety endpoints were adverse and serious adverse events associated with the test device and serious adverse events resulting in death or serious health deterioration. Result: A total of 129 patients were included; of them, 128 were analyzed in the full analysis set (FAS) and per protocol set (PPS). Immediate procedural success was achieved in 97.7% of patients with FAS and PPS. The lower bound of the 95% confidence interval was 94.6%, higher than the preset efficacy margin of 94%. Device-related adverse events occurred in 2 (1.6%) cases. One was mild adverse event of vasospasm, which resolved spontaneously. The other was serious adverse event of dissection aggravation, which was treated with stenting angioplasty. No device defects were observed. Conclusion: In neurointerventional surgery, the SeparGate™ BGC can be used to temporarily block the flow of the supra-aortic arch arteries and their branch vessels and guide the interventional device to the target vascular position.

Predictive accuracy of an ADC map for hemorrhagic transformation in acute ischemic stroke patients after successful recanalization with endovascular therapy.

Background: Hemorrhagic transformation (HT) of acute ischemic stroke (AIS) is associated with poor outcome. Previous studies only reported the association of mean ischemic severity or total infarct volume with HT after endovascular therapy (EVT). We aimed to investigate the predictive value of preoperative apparent diffusion coefficient (ADC) map for HT by combinated ischemic severity and corresponding volume in AIS after successful recanalization with EVT. Methods: We retrospectively analyzed 119 consecutive cases of AIS with large vessel occlusion of anterior circulation within 24 hours after symptom onset and successful recanalization after EVT. All cases had baseline magnetic resonance imaging (MRI), follow-up computed tomography (CT), and magnetic resonance angiography (MRA) or computed tomography angiography (CTA). Volumes of ADC <0.6×10-3, 0.5×10-3, 0.4×10-3, and 0.3×10-3 mm2/s, baseline characteristics and outcomes of patients with and without HT identified by European Collaborative Acute Stroke Study (ECASS) were compared. The optimal ADC and volume threshold for predicting HT were analyzed using receiver operating characteristic (ROC) curve, and multivariate logistic regression analysis were performed with clinical characteristics and volumes of optimal ADC threshold to determine risk factors for HT. Results: Among 119 patients, 42 patients had HT on follow-up CT, including 24 hemorrhagic infarct (HI) cases and 18 parenchymal hematoma (PH) cases. The optimal volumes were 6.46 mL with ADC <0.4×10-3 mm2/s for predicting both HT and PH, with a larger area under curve (AUC) of 83.3% for HT than that for PH of 80%. In logistic regression analysis, intravenous tissue plasminogen activator (IV tPA) treatment, atrial fibrillation, and volume of ADC <0.4×10-3 mm2/s were identified as independent predictors for HT and volume of ADC <0.4×10-3 mm2/s had the highest odds ratio (OR) value. Conclusions: The combination of ischemic severity and corresponding volume in ADC map may predict HT after thrombectomy. In addition to the total infarct volume, volume with severe ischemia should be taken into consideration in preoperative patient selection.

A Field-Independent Method for the Rapid Generation of Hyperpolarized [1-13 C]Pyruvate in Clean Water Solutions for Biomedical Applications.

Hyperpolarization methods in magnetic resonance enhance the signals by several orders of magnitude, opening new windows for real-time investigations of dynamic processes in vitro and in vivo. Here, we propose a field-independent para-hydrogen-based pulsed method to produce rapidly hyperpolarized 13 C-labeled substrates. We demonstrate the method by polarizing the carboxylic carbon of the pyruvate moiety in a purposely designed precursor to 24 % at ≈22 mT. Following a fast purification procedure, we measure 8 % polarization on free [1-13 C]pyruvate in clean water solutions at physiological conditions at 7 T. The enhanced signals allow real-time monitoring of the pyruvate-lactate conversion in cancer cells, demonstrating the potential of the method for biomedical applications in combination with existing or developing magnetic resonance technologies.

L-Arginine reduces downstream vascular contractility after flow-diverting device deployment: A preliminary study in a rabbit model.

BACKGROUND: Flow diverters (FDs) are an effective treatment for intracranial aneurysms, though not free from hemorrhagic complications. A previous study demonstrated increased vascular contractility after FD-implantation as a potential mechanism of distal complications. Our study aimed to investigate whether L-arginine medication affects vascular contractility following FD deployment in a rabbit model. METHODS: FDs were implanted in the aorta of normal rabbits (+FD, n = 10), with sham-operated aorta as controls (n = 5). L-Arginine was given in the drinking water (2.25% L-arginine hydrochloride) of half of the +FD animals (+FD/+Arg). Force contraction vascular contractility studies were performed on the aortic rings proximal and distal to the FD using an organ bath. Total eNOS, eNOS(pS1177), eNOS(pT495), COX-2, and S100A4 were quantified by western analysis on total protein lysates from aortic segments, normalizing to GAPDH. RESULTS: Mean vascular contractility was 53% higher in distal relative to proximal aortic segments (P = 0.0038) in +FD animals, but were not significantly different in +FD/+Arg animals, or in sham-operated controls. The +FD animals expressed significantly reduced levels of eNOS(pS1177) than sham-operated controls (P = 0.0335), while both the +FD and +FD/+Arg groups had reduced levels of eNOS(pT495) relative to sham-operated controls (P = 0.0331 and P = 0.0311, respectively). CONCLUSION: These results suggest that L-arginine medication reduces distal vascular contractility after FD treatment via nitric oxide production and thus might mitigate risk for downstream complications.

Photo-CIDNP in Solid State.

Photo-CIDNP (photo-chemically induced dynamic nuclear polarization) refers to nuclear polarization created by the spin-chemical evolution of spin-correlated radical pairs (SCRPs). This phenomenon occurs in gases, liquids and solids. Based on the solid-state photo-CIDNP effect observed under magic-angle spinning (MAS), photo-CIDNP MAS NMR has been developed as analytical method. Here we report the origin, the theory and the state of the art of this method.

In Vitro Study of Blood Clot Identification and Composition Assessment by Different Magnetic Resonance Sequences.

Background Growing data suggest that clot composition can impact revascularization outcomes and can potentially guide treatment strategies for stroke patients with large vessel occlusion. We performed an in vitro study to determine which magnetic resonance (MR) signaling characteristics correlate with clot compositions. Methodology A total of 25 clot analogs were prepared by mixing human plasma and red blood cells (RBCs) with five different combinations (five samples for each combination), namely, Group A, fibrin-rich (95% plasma:5% RBCs); Group B, fibrin-rich (75% plasma:25% RBCs); Group C, intermediate (50% plasma:50% RBCs); Group D, RBC-rich (25% plasma:75% RBCs), and Group E, RBC-rich (5% plasma:95% RBCs). The prepared samples were then scanned with quantitative T2* mapping, T2 fast spin-echo (FSE), T2 gradient-echo (GRE), fluid-attenuated inversion recovery (FLAIR), and susceptibility-weighted angiography (SWAN). Thrombus-T2* relaxation time (TT2*RT) and signal intensity (SI) from different scanning sequences were measured in all groups. SIs between different groups were compared using a one-way analysis of variance. Correlation between TT2*RT and SI was determined using the Pearson correlation test. Results The average TT2*RT decreased from 126 ms to 37 ms from fibrin-rich to RBC-rich clots (Groups A to E). Mean SIs of Groups D and E were lower than Groups A, B, and C on T2 mapping, T2 FSE, T2 GRE, FLAIR, and SWAN images (p < 0.00001). TT2*RT and SI were positively correlated on T2 mapping (R = 0.9628, p = 0.009). Conclusion Different compositions of blood clots can show different TT2*RT and SI on MR imaging. Quantitative T2* mapping and multicontrast MR scanning can help in the characterization of clots causing large vessel occlusion, which is useful to establish treatment strategies for stroke patients.

Retrospective study of perioperative cardiac arrest from a Chinese tertiary hospital.

ABSTRACT: Studies on perioperative cardiac arrest in Chinese hospitals have rarely been retrieved from international journals. This survey evaluated the incidence, causes, and outcomes of perioperative cardiac arrests in a Chinese tertiary general hospital between July 2013 and December 2020. The incidence of cardiac arrest within 24 hours of anesthesia administration was retrospectively identified using an anesthesia database in Liaocheng People's Hospital. During the study period, there were 118,152 anesthetics. Data collected included patient characteristics, surgical procedures (elective or emergency), American Society of Anesthesiologists (ASA) physical status score, type of surgery, anesthesia technique, and outcome. Cardiac arrests were grouped into one of 3 groups: totally anesthesia-related, partially anesthesia-related, or anesthesia-unrelated. In total, 41 cardiac arrests (3.5:10,000) and 26 deaths (2.2:10,000) were found. Major risk factors for cardiac arrest were children under 1 year, adults between 19 and 65 years, and the elderly (>80 years) (P < .001), male patients (P = .02), emergency surgery (P < .001), and ASA grade V patients without anesthesia (P = .009). There were 19 anesthesia-related cardiac arrests (1.6:10,000) - 2 were totally related, and 17 were partially related to anesthesia. There were 9 anesthesia-related deaths (0.8:10,000), all of which were partially related to anesthesia. Perioperative cardiac arrests were correlated with age, gender, ASA grade and surgical procedures. The 2 most important patient factors leading to cardiac arrest were hemorrhagic shock from trauma and septic shock, respectively.

Mapping the role of aromatic amino acids within a blue-light sensing LOV domain.

Photosensing LOV (Light, Oxygen, Voltage) domains detect and respond to UVA/Blue (BL) light by forming a covalent adduct between the flavin chromophore and a nearby cysteine, via the decay of the flavin triplet excited state. LOV domains where the reactive cysteine has been mutated are valuable fluorescent tools for microscopy and as genetically encoded photosensitisers for reactive oxygen species. Besides being convenient tools for applications, LOV domains without the reactive cysteine (naturally occurring or engineered) can still be functionally photoactivated via formation of a neutral flavin radical. Tryptophans and tyrosines are held as the main partners as potential electron donors to the flavin excited states. In this work, we explore the relevance of aromatic amino acids in determining the photophysical features of the LOV protein Mr4511 from Methylobacterium radiotolerans by introducing point mutations into the C71S variant that does not form the covalent adduct. By using an array of spectroscopic techniques we measured the fluorescence quantum yields and lifetimes, the triplet yields and lifetimes, and the efficiency of singlet oxygen (SO) formation for eleven Mr4511 variants. Insertion of Trp residues at distances between 0.6 and 1.5 nm from the flavin chromophore results in strong quenching of the flavin excited triplet state and, at the shorter distances even of the singlet excited state. The mutation F130W (ca. 0.6 nm) completely quenches the singlet excited state, preventing triplet formation: in this case, even if the cysteine is present, the photo-adduct is not formed. Tyrosines are also quenchers for the flavin excited states, although not as efficient as Trp residues, as demonstrated with their substitution with the inert phenylalanine. For one of these variants, C71S/Y116F, we found that the quantum yield of formation for singlet oxygen is 0.44 in aqueous aerobic solution, vs 0.17 for C71S. Based on our study with Mr4511 and on literature data for other LOV domains we suggest that Trp and Tyr residues too close to the flavin chromophore (at distances less than 0.9 nm) reduce the yield of photoproduct formation and that introduction of inert Phe residues in key positions can help in developing efficient, LOV-based photosensitisers.

A novel rabbit thromboembolic occlusion model.

BACKGROUND: To develop a preclinical thromboembolic occlusion model for studying revascularization strategies. METHODS: Clot analog with barium sulfate was injected into the distal aorta in 9 New Zealand white rabbits. The situation of aorta occlusion was compared among fibrin-rich (n=4), red blood cell (RBC)-rich (n=3), and whole blood clot analogs (n=2) using digital subtraction angiography. Arterial geometries, histologic features and circumferential stretch of the distal aorta in rabbits were compared with the common carotid artery in swine and the distal internal carotid artery (ICA) in humans. Aspiration thrombectomy and mechanical thrombectomy using a stent retriever were performed in two rabbits. RESULTS: The aortic bifurcation was occluded after a single delivery of clot in 4 cases. It was occluded after the second clot injection in the 5 remaining rabbits. Fragmentation of RBC-rich clots occurred during clot injection in 2 cases. The mean diameters of the distal aorta and right common iliac artery in rabbits were 3.7±0.4 and 2.8±0.3 mm, respectively; the mean diameters of human ICA, and first and second segments of the middle cerebral artery (M1, M2) were 3.6±0.4, 3.1±0.4, and 2.4±0.4 mm, respectively. Arterial revascularization was achieved in both rabbits. Geometric, mechanical and histological factors of the distal aorta in rabbit were more close to human distal ICA than swine carotid artery. CONCLUSION: Arterial occlusion can be achieved at the aortic bifurcation in rabbits, which is comparable to human ICA bifurcation. This thrombectomy model has the potential to be used for testing of thrombectomy devices.

Characterization of thrombus composition with multimodality CT-based imaging: an in-vitro study.

BACKGROUND: CT is the most commonly used imaging modality for acute ischemic stroke evaluation. There is growing interest to use pre-operative imaging to characterize clot composition in stroke. We performed an in-vitro study examining the ability of various CT techniques in differentiation between different clot types. METHODS: Five clot types with varying fibrin and red blood cells (RBCs) densities (5% RBC and 95% fibrin; 25% RBC and 75% fibrin; 50% RBC and 50% fibrin; 75% RBC and 25% fibrin; 95% RBC and 5% fibrin) were prepared and scanned using various CT scanning protocols (single-energy, dual-energy, photon-counting detector CT, mixed images, and virtual monoenergetic images). Martius Scarlett Blue trichrome staining was performed to confirm the composition of each clot. Mean CT values of each type of clot under different scanning protocol were calculated and compared. RESULTS: Mean CT values of the CT numbers in the five clot specimens for 5%, 25%, and 50% RBC clot were similar across modalities, and increased significantly for 75% and 95% RBC clots (P<0.0001). Mean CT values are highest in the Mono +50 keV images in each type of clot, and they were also significantly higher than all other imaging protocols (P<0.001). Dual-energy CT with Mono +50 keV images showed the greatest difference between attenuation in each type of clot. CONCLUSION: Mono +50 keV dual-energy CT scan may be helpful for differentiating between RBC-rich and fibrin-rich thrombi seen in large-vessel occlusion patients.

Assessment of Blood Clot Composition by Spectral Optical Coherence Tomography: An In Vitro Study.

PURPOSE: Optical coherence tomography (OCT) has the potential for in vivo clot composition characterization in difficult mechanical embolectomy cases. We performed an in vitro study to determine the OCT characteristics of red blood cells (RBCs) and fibrin rich clots. MATERIALS AND METHODS: Analogues of 5 compositions of clots (5% to 95% RBCs from Group A to E) were created from human blood. The blood mixture was injected into the bifurcation of a 3D printed bifurcated silicone tube. The OPTISTM Integrated System (St. Jude Medical Inc.) was used to identify the magnitude of OCT signals from different compositions of clots. Martius Scarlett Blue trichrome (MSB) staining was performed to confirm the composition of RBCs and fibrin in each clot. RESULTS: Group A and B showed less signal attenuation (less than 30%) from its surface to the inside, which indicated high penetration (low-back scattering). Group C indicated intermediate signal attenuation (60%) from its surface to inside the clots, in which signals were found even at the periphery of the clot. Group D and E were superficially signal rich with more signal attenuation (more than 80%) from its surface to the inside indicating low penetration (high-back scattering). Signal-free shadowing was shown in 3 clots in Group E. MSB staining indicated color change (from red in fibrin-rich clots to yellow in RBC-rich clots). CONCLUSION: Different compositions of clots can be assessed using OCT. Fibrin-rich clots have homogeneous signals with high penetration, while RBC-rich clots can be recognized as superficially signal rich with low penetration.

Cellular responses to flow diverters in a tissue-engineered aneurysm model.

BACKGROUND: Notwithstanding the widespread implementation of flow diverters (FDs) in the treatment of intracranial aneurysms, the exact mechanism of action of these devices remains elusive. We aimed to advance the understanding of cellular responses to FD implantation using a 3D tissue-engineered in vitro aneurysm model. METHODS: Aneurysm-like blood vessel mimics (aBVMs) were constructed by electrospinning polycaprolactone nanofibers onto desired aneurysm-like geometries. aBVMs were seeded with human aortic smooth muscle cells (SMCs) followed by human aortic endothelial cells (ECs). FDs were then deployed in the parent vessel of aBVMs covering the aneurysm neck and were cultivated for 7, 14, or 28 days (n=3 for each time point). The EC and SMC coverage in the neck was measured semi-quantitatively. RESULTS: At day 7, the device segment in contact with the parent vessel was partially endothelialized. Also, the majority of device struts, but not pores, at the parent vessel and neck interface were partially covered with ECs and SMCs, while device struts in the middle of the neck lacked cell coverage. At 14 days, histology verified a neointimal-like lining had formed, partially covering both the struts and pores in the center of the neck. At 28 days, the majority of the neck was covered with a translucent neointimal-like layer. A higher degree of cellular coverage was seen on the struts and pores at the neck at 28 days compared with both 7 and 14 days. CONCLUSION: aBVMs can be a valuable alternative tool for evaluating the healing mechanisms of endovascular aneurysm devices.

Tailored flavoproteins acting as light-driven spin machines pump nuclear hyperpolarization.

The solid-state photo-chemically induced dynamic nuclear polarization (photo-CIDNP) effect generates non-Boltzmann nuclear spin magnetization, referred to as hyperpolarization, allowing for high gain of sensitivity in nuclear magnetic resonance (NMR). Well known to occur in photosynthetic reaction centers, the effect was also observed in a light-oxygen-voltage (LOV) domain of the blue-light receptor phototropin, in which the functional cysteine was removed to prevent photo-chemical reactions with the cofactor, a flavin mononucleotide (FMN). Upon illumination, the FMN abstracts an electron from a tryptophan to form a transient spin-correlated radical pair (SCRP) generating the photo-CIDNP effect. Here, we report on designed molecular spin-machines producing nuclear hyperpolarization upon illumination: a LOV domain of aureochrome1a from Phaeodactylum tricornutum, and a LOV domain named 4511 from Methylobacterium radiotolerans (Mr4511) which lacks an otherwise conserved tryptophan in its wild-type form. Insertion of the tryptophan at canonical and novel positions in Mr4511 yields photo-CIDNP effects observed by 15N and 1H liquid-state high-resolution NMR with a characteristic magnetic-field dependence indicating an involvement of anisotropic magnetic interactions and a slow-motion regime in the transient paramagnetic state. The heuristic biomimetic design opens new categories of experiments to analyze and apply the photo-CIDNP effect.