Fluorescence Reflectance Imaging Research Articles

Tumor response to a mastermind inhibitor protein.

e17601 Background: Notch signalling is implicated in tumorigenesis prompting scientists to research and develop anti-Notch therapeutics. Drugging the Notch pathway has been a challenge due to severe G-I toxicity seen by many small-molecule inhibitors. Mastermind is a key nuclear factor that mediates Notch activity. We generated a novel protein drug, Syntana-4, that inhibits the Notch pathway at the Mastermind transcriptional level. Syntana-4 consists of the cell penetrating domain of Antennapedia, fused to a truncated peptide from Mastermind-like (MAML) that behaves in a dominant-negative fashion inhibiting Notch. Syntana-4 translocates into the cell nucleus, suppressing Notch activity and inducing apoptosis in Notch-driven cancer cells. Methods: We have conducted pharmacokinetics (PK), pharmacodynamics (PD) and toxicology studies, in combination with innovative imaging including in vivo flow cytometry and whole-body fluorescence reflectance imaging to define the behaviour of Syntana-4, determine its mode of action and establish a safety and efficacy profile in an orthotopic model of breast cancer in SCID mice based on the implantation of MDA-MB-231 cells into mammary fat pads. Samples of blood and tissues were examined for toxicity, apoptosis and immunogenicity. Results: We found that Syntana-4 was well-tolerated by normal cells and organs and was not immunogenic. Also, it was shown that free, non-internalized drug was rapidly cleared from the circulation. Whole body imaging showed that the drug in tissues was cleared within 24 hrs. Assessment of tumor growth demonstrated a reduction in tumor growth as evidenced by an overall increase of less than 50% in the intensity of fluorescence signal in the treated group compared to a 3-fold increase in signal and thus tumour size in untreated group by day 14. Conclusions: Syntana-4, a Mastermind inhibitor, was found to be well-tolerated and non-immunogenic in healthy animals. This drug targets the oncogenic Notch mechanism and can be applied across tumours with genetic defects in Notch signalling including breast, prostate, etc. We have demonstrated the utility of an innovative molecular imaging system emulating a clinical ‘phase I/II’ study in an orthotopic cancer model in order to measure the biodistribution, PK, PD, mode of action, toxicity and efficacy of a first-in-class biological therapy prior to entering the clinic. This innovative approach could be useful for accurate selection of lead drug candidates prior to entering clinical development.

Endothelial Palmitoylation Cycling Coordinates Vessel Remodeling in Peripheral Artery Disease.

Peripheral artery disease, common in metabolic syndrome and diabetes mellitus, responds poorly to medical interventions and is characterized by chronic vessel immaturity leading to lower extremity amputations. To define the role of reversible palmitoylation at the endothelium in the maintenance of vascular maturity. Endothelial knockout of the depalmitoylation enzyme APT-1 (acyl-protein thioesterase 1) in mice impaired recovery from chronic hindlimb ischemia, a model of peripheral artery disease. Endothelial APT-1 deficiency decreased fibronectin processing, disrupted adherens junctions, and inhibited in vitro lumen formation. In an unbiased palmitoylation proteomic screen of endothelial cells from genetically modified mice, R-Ras, known to promote vessel maturation, was preferentially affected by APT-1 deficiency. R-Ras was validated as an APT-1 substrate, and click chemistry analyses demonstrated increased R-Ras palmitoylation in cells with APT-1 deficiency. APT-1 enzyme activity was decreased in endothelial cells from db/db mice. Hyperglycemia decreased APT-1 activity in human umbilical vein endothelial cells, due, in part, to altered acetylation of the APT-1 protein. Click chemistry analyses demonstrated increased R-Ras palmitoylation in the setting of hyperglycemia. Altered R-Ras trafficking, increased R-Ras palmitoylation, and fibronectin retention were found in diabetes mellitus models. Loss of R-Ras depalmitoylation caused by APT-1 deficiency constrained R-Ras membrane trafficking, as shown by total internal reflection fluorescence imaging. To rescue cellular phenotypes, we generated an R-Ras molecule with an inserted hydrophilic domain to circumvent membrane rigidity caused by defective palmitoylation turnover. This modification corrected R-Ras membrane trafficking, restored fibronectin processing, increased adherens junctions, and rescued defective lumen formation induced by APT-1 deficiency. These results suggest that endothelial depalmitoylation is regulated by the metabolic milieu and controls plasma membrane partitioning to maintain vascular homeostasis.

Optimizing the Biodistribution of Radiofluorinated Barbiturate Tracers for Matrix Metalloproteinase Imaging by Introduction of Fluorescent Dyes as Pharmacokinetic Modulators.

Dysregulated expression or activation of matrix metalloproteinases (MMPs) is observed in many kinds of life-threatening diseases. Therefore, MMP imaging-for example, with radiolabeled MMP inhibitors (MMPIs)-potentially represents a valuable tool for clinical diagnostics using noninvasive single photon emission computed tomography (SPECT) or positron emission tomography (PET) imaging. Despite numerous preclinical imaging approaches, translation to a clinical setting has not yet been successful. We introduce and oppose three potential radiofluorinated MMP-targeted imaging probes, modified by the introduction of pentamethine cyanine (Cy5) dyes and therefore containing both radio- as well as fluorescent label with respect to their capability to assess MMP activity in vivo by means of scintigraphic (PET) and/or fluorescent (NIRF) imaging. New hybrid MMPI tracer candidates, structurally based on radiofluorinated pyrimidine-2,4,6-triones (barbiturates) from previous approaches, were synthesized by convenient two-step syntheses. In the first step, Cy5 dyes, varying in the number of sulfonate groups (nSO3- = 1, 2, or 4) and bearing an additional "clickable" alkyne moiety, were coupled to the barbiturate MMPI by amide formation. In the second step, the [18F]fluoride radiolabel was introduced into the resulting Cy5 dye conjugates by "radio-click" chemistry. Biodistribution studies of these hybrid tracer candidates were assessed and compared in C57BL/6 mice by PET as well as fluorescence imaging. MMP activity was imaged in a MMP-positive mouse model of irritant contact dermatitis (ICD) by PET and sequential fluorescence reflectance imaging (FRI), respectively. In vivo data were validated by scintillation counting, gelatin zymography, and MMP-histology. Three new potential hybrid MMP imaging probes were prepared, differing essentially in the number of sulfonate groups, introduced by Cy5 dye components. Although the hydrophilicity of these compounds was substantially increased, 10a (nSO3- = 1) and 10b (nSO3- = 2) were still rapidly eliminated via unfavorable hepatobiliary pathways, as observed in earlier approaches. Only 11 (nSO3- = 4) showed delayed in vivo clearance and a shift towards higher renal elimination. In the chosen mouse model of ICD, only 11 (nSO3- = 4) significantly accumulated in the inflamed mouse ear, which could be precisely visualized by means of PET and FRI.

Synaptotagmin-7 enhances calcium-sensing of chromaffin cell granules and slows discharge of granule cargos.

Synaptotagmin-7 (Syt-7) is one of two major calcium sensors for exocytosis in adrenal chromaffin cells, the other being synaptotagmin-1 (Syt-1). Despite a broad appreciation for the importance of Syt-7, questions remain as to its localization, function in mediating discharge of dense core granule cargos, and role in triggering release in response to physiological stimulation. These questions were addressed using two distinct experimental preparations-mouse chromaffin cells lacking endogenous Syt-7 (KO cells) and a reconstituted system employing cell-derived granules expressing either Syt-7 or Syt-1. First, using immunofluorescence imaging and subcellular fractionation, it is shown that Syt-7 is widely distributed in organelles, including dense core granules. Total internal reflection fluorescence (TIRF) imaging demonstrates that the kinetics and probability of granule fusion in Syt-7 KO cells stimulated by a native secretagogue, acetylcholine, are markedly lower than in WT cells. When fusion is observed, fluorescent cargo proteins are discharged more rapidly when only Syt-1 is available to facilitate release. To determine the extent to which the aforementioned results are attributable purely to Syt-7, granules expressing only Syt-7 or Syt-1 were triggered to fuse on planar supported bilayers bearing plasma membrane SNARE proteins. Here, as in cells, Syt-7 confers substantially greater calcium sensitivity to granule fusion than Syt-1 and slows the rate at which cargos are released. Overall, this study demonstrates that by virtue of its high affinity for calcium and effects on fusion pore expansion, Syt-7 plays a central role in regulating secretory output from adrenal chromaffin cells.

Mapping the pigment distribution of Vermeer\u2019s Girl with a Pearl Earring

As part of the 2018 Girl in the Spotlight project, reflectance and molecular fluorescence imaging spectroscopy (RIS, FIS), and macroscale X-ray fluorescence scanning (MA-XRF) were performed on Johannes Vermeer’s Girl with a Pearl Earring (c. 1665, Mauritshuis) with the goal of obtaining a comprehensive understanding of the distribution of pigments. Prior analysis of cross-sections in the 1990s, and their recent (re)-examination identified many of the pigments present in the painting. The results from all three imaging methods, along with site-specific fibre optic reflectance spectroscopy, confirmed Vermeer’s limited palette and determined how and where each pigment was used. RIS and MA-XRF found the blue region of the headscarf was painted with natural ultramarine and varying amounts of lead white. The yellow part of the headscarf was painted with yellow ochre and lead white, and the border of the headscarf additionally contained ultramarine and lead–tin yellow. The lit side of the jacket was painted with yellow ochre, lead white, and ultramarine, whereas the darker, ruddy blue-green areas that are in relative shadow contained yellow ochre with ultramarine. FIS also mapped a red lake in portions of the shadowed areas at the back of the jacket. The Girl’s skin was painted using earths (ochres), lead white, vermilion, and some red lake. Fluorescence emission from red lake was strongest in the lips, where vermilion was also found. The pearl earring was depicted using a scumble and highlight of lead white. In the dark background, the RIS data cube allowed the determination of the visible spectral shape even though the overall reflectance intensity was low (1 to 3%). A reflectance inflection point at ~ 700 nm indicated the presence of indigo, whereas lack of a reflectance peak at green wavelengths in most areas indicated degradation of the yellow pigment previously identified as weld. Some small green areas in the background (i.e. reflectance maximum at 525 nm) were found; these coincided with areas previously protected by old retouchings, and are thus better preserved. The combination of all three spectral imaging modalities provided a more complete understanding of how the colouration of the painting was achieved.

Multimodal and multiscale optical imaging of nanomedicine delivery across the blood-brain barrier upon sonopermeation.

Rationale: The blood-brain barrier (BBB) is a major obstacle for drug delivery to the brain. Sonopermeation, which relies on the combination of ultrasound and microbubbles, has emerged as a powerful tool to permeate the BBB, enabling the extravasation of drugs and drug delivery systems (DDS) to and into the central nervous system (CNS). When aiming to improve the treatment of high medical need brain disorders, it is important to systematically study nanomedicine translocation across the sonopermeated BBB. To this end, we here employed multimodal and multiscale optical imaging to investigate the impact of DDS size on brain accumulation, extravasation and penetration upon sonopermeation.Methods: Two prototypic DDS, i.e. 10 nm-sized pHPMA polymers and 100 nm-sized PEGylated liposomes, were labeled with fluorophores and intravenously injected in healthy CD-1 nude mice. Upon sonopermeation, computed tomography-fluorescence molecular tomography, fluorescence reflectance imaging, fluorescence microscopy, confocal microscopy and stimulated emission depletion nanoscopy were used to study the effect of DDS size on their translocation across the BBB.Results: Sonopermeation treatment enabled safe and efficient opening of the BBB, which was confirmed by staining extravasated endogenous IgG. No micro-hemorrhages, edema and necrosis were detected in H&E stainings. Multimodal and multiscale optical imaging showed that sonopermeation promoted the accumulation of nanocarriers in mouse brains, and that 10 nm-sized polymeric DDS accumulated more strongly and penetrated deeper into the brain than 100 nm-sized liposomes.Conclusions: BBB opening via sonopermeation enables safe and efficient delivery of nanomedicine formulations to and into the brain. When looking at accumulation and penetration (and when neglecting issues such as drug loading capacity and therapeutic efficacy) smaller-sized DDS are found to be more suitable for drug delivery across the BBB than larger-sized DDS. These findings are valuable for better understanding and further developing nanomedicine-based strategies for the treatment of CNS disorders.

Targeting Endothelin Receptors in a Murine Model of Myocardial Infarction Using a Small Molecular Fluorescent Probe.

The endothelin (ET) axis plays a pivotal role in cardiovascular diseases. Enhanced levels of circulating ET-1 have been correlated with an inferior clinical outcome after myocardial infarction (MI) in humans. Thus, the evaluation of endothelin-A receptor (ETAR) expression over time in the course of myocardial injury and healing may offer valuable information toward the understanding of the ET axis involvement in MI. We developed an approach to track the expression of ETAR with a customized molecular imaging probe in a murine model of MI. The small molecular probe based on the ETAR-selective antagonist 3-(1,3-benzodioxol-5-yl)-5-hydroxy-5-(4-methoxyphenyl)-4-[(3,4,5-trimethoxyphenyl)methyl]-2(5H)-furanone (PD156707) was labeled with fluorescent dye, IRDye800cw. Mice undergoing permanent ligation of the left anterior descending artery (LAD) were investigated at day 1, 7, and 21 post surgery after receiving an intravenous injection of the ETAR probe. Cryosections of explanted hearts were analyzed by cryotome-based CCD, and fluorescence reflectance imaging (FRI) and fluorescence signal intensities (SI) were extracted. Fluorescence-mediated tomography (FMT) imaging was performed to visualize probe distribution in the target region in vivo. An enhanced fluorescence signal intensity in the infarct area was detected in cryoCCD images as early as day 1 after surgery and intensified up to 21 days post MI. FRI was capable of detecting significantly enhanced SI in infarcted regions of hearts 7 days after surgery. In vivo imaging by FMT localized enhanced SI in the apex region of infarcted mouse hearts. We verified the localization of the probe and ETAR within the infarct area by immunohistochemistry (IHC). In addition, neovascularized areas were found in the affected myocardium by CD31 staining. Our study demonstrates that the applied fluorescent probe is capable of delineating ETAR expression over time in affected murine myocardium after MI in vivo and ex vivo.

Roles of LRRC26 as an auxiliary γ1-subunit of large-conductance Ca2+-activated K+ channels in bronchial smooth muscle cells

In visceral smooth muscle cells (SMCs), the large-conductance Ca2+-activated K+ (BK) channel is one of the key elements underlying a negative feedback mechanism that is essential for the regulation of intracellular Ca2+ concentration. Although leucine-rich repeat-containing (LRRC) proteins have been identified as novel auxiliary γ-subunits of the BK channel (BKγ) in several cell types, its physiological roles in SMCs are unclear. The BKγ expression patterns in selected SM tissues were examined using real-time PCR analyses and Western blotting. The functional contribution of BKγ1 to BK channel activity was examined by whole cell patch-clamp in SMCs and heterologous expression systems. BKγ1 expression in mouse bronchial SMCs (mBSMCs) was higher than in other several SMC types. Coimmunoprecipitation and total internal reflection fluorescence imaging analyses revealed molecular interaction between BKα and BKγ1 in mBSMCs. Under voltage-clamp, steady-state activation of BK channel currents at pCa 8.0 in mBSMCs occurred in a voltage range comparable to that of reconstituted BKα/BKγ1 complex. However, this range was much more negative than in mouse aortic SMCs (mASMCs) or in HEK293 cells expressing BKα alone and β-subunit (BKβ1). Mallotoxin, a selective activator of BK channel that lacks BKγ1, dose-dependently activated BK currents in mASMCs but not in mBSMCs. The abundant expression of BKγ1 in mBSMCs extensively facilitates BK channel activity to keep the resting membrane potential at negative values and prevents contraction under physiological conditions.

Odilon Redon\u2019s noir drawings: characterization of materials and methods using noninvasive imaging and spectroscopies

The artist Odilon Redon (1840–1916) was a French symbolist known for both the dark, surreal prints and drawings he created in the first half of his career, as well as the colorful pastel works that characterized the second half of his career. This study examines two drawings by Redon in the J. Paul Getty Museum collection—Apparition (ca. 1880–1890) and Head within an Aureole (ca. 1894–1895)—executed during the period in his career in which he was transitioning between these two modes. In order to better understand the materials the artist chose and the methods by which he applied them, two noninvasive, macroscopic characterization techniques—macro X-ray fluorescence (MA-XRF) scanning and reflectance imaging spectroscopy (RIS)—were employed. These techniques allowed the materials present to be distinguished and the relationship between their applications visualized. Coupled with fiber optic reflectance spectroscopy (FORS) and Raman microspectroscopy with principal component analysis (PCA), these results give new insight into the materials and methods used by Redon. Six distinct black drawing materials and a yellow pastel were identified in Apparition, underscoring the complexity of Redon’s noir drawings. As he began using color pastel more frequently he seemed to use a simplified black palette; in Head within an Aureole the artist used only two black drawing materials and three color pastels (two pink and one blue). This research provides a framework for future noninvasive technical analysis of works by Redon in other collections as well as mixed media drawings more generally.

Target-Specific Imaging of Cathepsin and S100A8/A9 Reflects Specific Features of Malignancy and Enables Estimation of Tumor Malignancy.

Tumor development and metastasis are dependent on tumor infiltrating immune cells which form a characteristic tumor microenvironment (TME). Activated monocytes secrete the protein heterodimer S100A8/A9 promoting TME formation. Monocyte-dependent proteases facilitate local tumor cell invasion by degradation of the extracellular matrix. We aimed for target specific in vivo imaging of S100A8 and proteases to provide differentiating biomarkers for local tumor growth and metastatic potential. Murine breast cancer cells of the 4T1 model with graduated metastatic potential (4T1 and 4T07: both hematogenous metastasis > 168FAR: lymph-node metastasis > 67NR: no metastasis) were orthotopically implanted into female BALB/c mice. At 4mm size, tumors were investigated by injecting the protease-specific probe ProSense 750EX (PerkinElmer, 4T1 n = 7, 4T07 n = 10, 168FAR n = 16, 67NR n = 15) and anti-S100A8-Cy5.5 (n = 6 each) and performing fluorescence reflectance imaging at 0 and 24h after injection. In vivo imaging was validated with immunohistochemistry. At 24h, S100A8-specific signals in 4T1 and 4T07 were significantly higher (1714.05/1683.45AU) as compared to 168FAR and 67NR (174.85/167.95AU, p = 0.0012/p = 0.0003), reflecting the capability of hematogenous spread. Protease-specific signals were significantly higher in 4T1 and 4T07 (348.01/409.93AU) as compared to 168FAR (214.91AU) and 67NR (129.78AU p < 0.0001 each), reflecting local vessel invasion and tumor cell shedding. Immunohistology supported the in vivo imaging results. Non-invasive in vivo imaging of S100A8 and monocytic proteases allows for differentiation of the tumors' local invasive and systemic metastatic potential in reflecting the TME formation. While proteases augment local tumor cell invasion, solid metastases seem to be dependent on a pro-tumoral microenvironment.

Kinetic Measurements of Endocytosis and Exocytosis in Cultured Neurons.

The measurement of synaptic vesicle recycling in live neurons transfected with vesicular glutamate transporter fused to pHluorin (vGLUT-pHluorin) allows us to study exocytosis and endocytosis in neurons. When neurons are transfected with this protein we can measure the rate of vesicles fusing and internalizing from the membrane using live total internal reflection fluorescence (TIRF) imaging. Here, we describe transfection, culturing, and imaging of wild-type and αβγ-synuclein knockout hippocampal neurons. This technique can be used to evaluate the effect of different phenotypes and treatments in the physiology of synaptic vesicle recycling in cultured neurons.

2018 AHA Late-Breaking Basic Science Abstracts.

2018 AHA Late-Breaking Basic Science Abstracts.

Molecular imaging of MMP activity discriminates unstable from stable plaque phenotypes in shear-stress induced murine atherosclerosis.

PurposeAs atherosclerotic plaque ruptures are the primary cause of ischaemic events, their preventive identification by imaging remains a clinical challenge. Matrix metalloproteinases (MMP) are involved in plaque progression and destabilisation and are therefore promising targets to characterize rupture-prone unstable plaques. This study aims at evaluating MMP imaging to discriminate unstable from stable plaque phenotypes.MethodsApoE deficient mice (ApoE-/-) on a high cholesterol diet underwent implantation of a tapered cuff around the right common carotid artery (CCA) inducing a highly inflamed atherosclerotic plaque upstream (US) and a more stable plaque phenotype downstream (DS) of the cuff. 8 weeks after surgery, the MMP inhibitor-based photoprobe Cy5.5-AF443 was administered i.v. 3h prior to in situ and ex vivo fluorescence reflectance imaging of the CCAs. Thereafter, CCAs were analysed regarding plaque size, presence of macrophages, and MMP-2 and MMP-9 concentrations by immunohistochemistry and ELISA.ResultsWe found a significantly higher uptake of Cy5.5-AF443 in US as compared to DS plaques in situ (1.29 vs. 1.06 plaque-to-background ratio; p<0.001), which was confirmed by ex vivo measurements. Immunohistochemistry revealed a higher presence of macrophages, MMP-2 and MMP-9 in US compared to DS plaques. Accordingly, MMP-2 concentrations were significantly higher in US plaques (47.2±7.6 vs. 29.6±4.6 ng/mg; p<0.05).ConclusionsIn the ApoE-/- cuff model MMP-2 and MMP-9 activities are significantly higher in upstream low shear stress-induced unstable atherosclerotic plaques as compared to downstream more stable plaque phenotypes. MMP inhibitor-based fluorescence molecular imaging allows visualization of these differences in shear stress-induced atherosclerosis.

Joint data treatment for Vis–NIR reflectance imaging spectroscopy and XRF imaging acquired in the Theban Necropolis in Egypt by data fusion and t-SNE

Abstract Hyperspectral imaging allows the acquisition of representative information on cultural heritage objects. For a complete identification of the chemical compounds present, one needs instruments employing different forms of radiation, sensitive to different chemical features. Data treatment workflows are commonly developed for a single spectroscopic technique, so that data sets are evaluated separately, and the reduced representations yielded are compared during interpretation. In this publication, we describe how t-stochastic neighbor embedding (t-SNE) allows for the evaluation and interpretation of data acquired in a Ramesside tomb (13th century BC) of the Theban Necropolis in Egypt. By fusing X-ray Fluorescence (XRF) imaging and Reflectance Imaging Spectroscopy (RIS) into a single data set, we exploit the synergies between both methods to support interpretation and presentation of the results yielded.

Rapid diffusion-state switching underlies stable cytoplasmic gradients in the Caenorhabditis elegans zygote

Protein concentration gradients organize cells and tissues and commonly form through diffusion away from a local source of protein. Interestingly, during the asymmetric division of the Caenorhabditis elegans zygote, the RNA-binding proteins MEX-5 and PIE-1 form opposing concentration gradients in the absence of a local source. In this study, we use near-total internal reflection fluorescence (TIRF) imaging and single-particle tracking to characterize the reaction/diffusion dynamics that maintain the MEX-5 and PIE-1 gradients. Our findings suggest that both proteins interconvert between fast-diffusing and slow-diffusing states on timescales that are much shorter (seconds) than the timescale of gradient formation (minutes). The kinetics of diffusion-state switching are strongly polarized along the anterior/posterior (A/P) axis by the PAR polarity system such that fast-diffusing MEX-5 and PIE-1 particles are approximately symmetrically distributed, whereas slow-diffusing particles are highly enriched in the anterior and posterior cytoplasm, respectively. Using mathematical modeling, we show that local differences in the kinetics of diffusion-state switching can rapidly generate stable concentration gradients over a broad range of spatial and temporal scales.

Monitoring of tumor burden invivo by optical imaging in a xenograft SCID mouse model: evaluation of two fluorescent proteins of the GFP-superfamily.

Mouse models of human-malignant-melanoma (MM) are important tools to study tumor dynamics. The enhanced green fluorescent protein (EGFP) is widely used in molecular imaging approaches, together with optical scanners, and fluorescence imaging. Currently, there are no data available as to whether other fluorescent proteins are more suitable. The goal of this preclinical study was to analyze two fluorescent proteins of the GFP superfamily under real-time invivo conditions using fluorescence reflectance imaging (FRI). The human melanoma cell line MeWo was stable transfected with one plasmid: pEGFP-C1 or pDsRed1-N1. We investigated two severe combined immunodeficiency (SCID)-mice groups: A (solid xenografts) and B (xenografts as metastases). After three weeks, the animals were weekly imaged by FRI. Afterwards the mice were euthanized and metastases were imaged in situ: to quantify the cutis-dependent reduction of emitted light, we compared signal intensities obtained by metastases invivo with signal intensities obtained by in situ liver parenchyma preparations. More than 90% of cells were stable transfected. EGFP-/DsRed-xenograft tumors had identical growth kinetics. Invivo the emitted light by DsRed tumors/metastases was much brighter than by EGFP. DsRed metastases were earlier (3 vs. 5 weeks) and much more sensitive detectable than EGFP metastases. Cutis-dependent reduction of emitted light was greater in EGFP than in DsRed mice (tenfold). Autofluorescence of DsRed was lower than of EGFP. We established an invivo xenograft mouse model (DsRed-MeWo) that is reliable, reproducible, and superior to the EGFP model as a preclinical tool to study innovative therapies by FRI under real-time invivo conditions.

Abstract 051: A New Model of Murine Stasis Pulmonary Thromboembolism in vivo With Assessment by Noninvasive Multimodal Molecular-Structural Imaging

Objective: Pulmonary embolism (PE) is a life-threatening cardiovascular disease that urgently requires improved diagnostic, prognostic and therapeutic options. Here we established and investigated a novel murine PE model based on embolization of a stasis-induced venous thrombus (VT). We further utilized in vivo molecular-structural imaging of fibrin accessibility to assess the healing status of the PE. Methods: Stasis VT was induced in the femoral veins of donor C57BL6 mice. VT was resected 24 hours (h) after induction and then intravenously injected into recipient mice to create PE. Pulse-wave Doppler of pulmonary artery flow was utilized to evaluate the pulmonary arterial pressure (PAP) before and 24h after embolization. One day after embolization, the fibrin-specific probe FTP11-CyAm7 (750/767nm ex/em, 150 nmoles/kg i.v.) assessed the FTP binding and spatial localization of PE via integrated fluorescence-mediated tomography and computed tomography (FMT-CT) pulmonary angiography. Mice were sacrificed 1, 4, 8, or 21 days following stasis-VT embolization, and underwent histological analysis of the PE. Results: Femoral vein stasis-VT exhibited similar temporal inflammatory neutrophil and monocyte/macrophage infiltration and FTP11 binding (fibrin accessibility) kinetics compared to inferior vena cava stasis-VT models. The mean VT width and length were 2.4±0.2mm and 0.65±0.02mm, respectively (n=29 thrombi). Noninvasive ultrasound assessment of the mouse PAP, assessed via the pulmonary acceleration time (PAT), showed a 22% decrease (p=0.03) in pre-to-post-PE PAT times, consistent with increased PAP due to PE. FMT-CT imaging using FTP11 demonstrated accessible fibrin in day 1 PE and visualized PE confined to the lungs, primarily (91%) in the right lung. Ex vivo fluorescence reflectance imaging and histological analysis verified the location PE reported by FMT-CT. Conclusions: These data validate the first in vivo model of PE based on stasis VT formed in vivo. The model reproducibly generates a survival PE that harbors accessible fibrin in recent stasis VT lodged in the lung, and acute increases PAP. This new clinically relevant model of PE is anticipated to facilitate research of acute PE and chronic thromboembolic pulmonary hypertension.

Abstract 301: A New Model of Murine Stasis Pulmonary Thromboembolism in vivo With Assessment by Noninvasive Multimodal Molecular-Structural Imaging

Objective: Pulmonary embolism (PE) is a life-threatening cardiovascular disease that urgently requires improved diagnostic, prognostic and therapeutic options. Here we established and investigated a novel murine PE model based on embolization of a stasis-induced venous thrombus (VT). We further utilized in vivo molecular-structural imaging of fibrin accessibility to assess the healing status of the PE. Methods: Stasis VT was induced in the femoral veins of donor C57BL6 mice. VT was resected 24 hours (h) after induction and then intravenously injected into recipient mice to create PE. Pulse-wave Doppler of pulmonary artery flow was utilized to evaluate the pulmonary arterial pressure (PAP) before and 24h after embolization. One day after embolization, the fibrin-specific probe FTP11-CyAm7 (750/767nm ex/em, 150 nmoles/kg i.v.) assessed the FTP binding and spatial localization of PE via integrated fluorescence-mediated tomography and computed tomography (FMT-CT) pulmonary angiography. Mice were sacrificed 1, 4, 8, or 21 days following stasis-VT embolization, and underwent histological analysis of the PE. Results: Femoral vein stasis-VT exhibited similar temporal inflammatory neutrophil and monocyte/macrophage infiltration and FTP11 binding (fibrin accessibility) kinetics compared to inferior vena cava stasis-VT models. The mean VT width and length were 2.4±0.2mm and 0.65±0.02mm, respectively (n=29 thrombi). Noninvasive ultrasound assessment of the mouse PAP, assessed via the pulmonary acceleration time (PAT), showed a 22% decrease (p=0.03) in pre-to-post-PE PAT times, consistent with increased PAP due to PE. FMT-CT imaging using FTP11 demonstrated accessible fibrin in day 1 PE and visualized PE confined to the lungs, primarily (91%) in the right lung. Ex vivo fluorescence reflectance imaging and histological analysis verified the location PE reported by FMT-CT. Conclusions: These data validate the first in vivo model of PE based on stasis VT formed in vivo. The model reproducibly generates a survival PE that harbors accessible fibrin in recent stasis VT lodged in the lung, and acute increases PAP. This new clinically relevant model of PE is anticipated to facilitate research of acute PE and chronic thromboembolic pulmonary hypertension.

Three-dimensional super-resolved live cell imaging through polarized multi-angle TIRF.

Measuring three-dimensional nanoscale cellular structures is challenging, especially when the structure is dynamic. Owing to the informative total internal reflection fluorescence (TIRF) imaging under varied illumination angles, multi-angle (MA) TIRF has been examined to offer a nanoscale axial and a subsecond temporal resolution. However, conventional MA-TIRF still performs badly in lateral resolution and fails to characterize the depth image in densely distributed regions. Here, we emphasize the lateral super-resolution in the MA-TIRF, exampled by simply introducing polarization modulation into the illumination procedure. Equipped with a sparsity and accelerated proximal algorithm, we examine a more precise 3D sample structure compared with previous methods, enabling live cell imaging with a temporal resolution of 2s and recovering high-resolution mitochondria fission and fusion processes. We also shared the recovery program, which is the first open-source recovery code for MA-TIRF, to the best of our knowledge.

Dynamic and Irregular Distribution of RyR2 Clusters in the Periphery of Live Ventricular Myocytes

Cardiac ryanodine receptors (RyR2s) are Ca2+ release channels clustering in the sarcoplasmic reticulum membrane. These clusters are believed to be the elementary units of Ca2+ release. The distribution of these Ca2+ release units plays a critical role in determining the spatio-temporal profile and stability of sarcoplasmic reticulum Ca2+ release. RyR2 clusters located in the interior of cardiomyocytes are arranged in highly ordered arrays. However, little is known about the distribution and function of RyR2 clusters in the periphery of cardiomyocytes. Here, we used a knock-in mouse model expressing a green fluorescence protein (GFP)-tagged RyR2 to localize RyR2 clusters in live ventricular myocytes by virtue of their GFP fluorescence. Confocal imaging and total internal reflection fluorescence microscopy was employed to determine and compare the distribution of GFP-RyR2 in the interior and periphery of isolated live ventricular myocytes and in intact hearts. We found tightly ordered arrays of GFP-RyR2 clusters in the interior, as previously described. In contrast, irregular distribution of GFP-RyR2 clusters was observed in the periphery. Time-lapse total internal reflection fluorescence imaging revealed dynamic movements of GFP-RyR2 clusters in the periphery, which were affected by external Ca2+ and RyR2 activator (caffeine) and inhibitor (tetracaine), but little detectable movement of GFP-RyR2 clusters in the interior. Furthermore, simultaneous Ca2+- and GFP-imaging demonstrated that peripheral RyR2 clusters with an irregular distribution pattern are functional with a Ca2+ release profile similar to that in the interior. These results indicate that the distribution of RyR2 clusters in the periphery of live ventricular myocytes is irregular and dynamic, which is different from that of RyR2 clusters in the interior.