Shape Anisotropy-Governed High-Performance Nanomagnetosol for In Vivo Magnetic Particle Imaging of Lungs.

Caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), coronavirus disease 2019 (COVID-19) has shown extensive lung manifestations in vulnerable individuals, putting lung imaging and monitoring at the forefront of early detection and treatment. Magnetic particle imaging (MPI) is an imaging modality, which can bring excellent contrast, sensitivity, and signal-to-noise ratios to lung imaging for the development of new theranostic approaches for respiratory diseases. Advances in MPI tracers would offer additional improvements and increase the potential for clinical translation of MPI. Here, a high-performance nanotracer based on shape anisotropy of magnetic nanoparticles is developed and its use in MPI imaging of the lung is demonstrated. Shape anisotropy proves to be a critical parameter for increasing signal intensity and resolution and exceeding those properties of conventional spherical nanoparticles. The 0D nanoparticles exhibit a 2-fold increase, while the 1D nanorods have a > 5-fold increase in signal intensity when compared to VivoTrax. Newly designed 1D nanorods displayed high signal intensities and excellent resolution in lung images. A spatiotemporal lung imaging study in mice revealed that this tracer offers new opportunities for monitoring disease and guiding intervention.

Three-dimensional imaging and quantification of mouse ovarian follicles via optical coherence tomography.

Ovarian tissue cryopreservation has been successfully applied worldwide for fertility preservation. Correctly selecting the ovarian tissue with high follicle loading for freezing and reimplantation increases the likelihood of restoring ovarian function, but it is a challenging process. In this work, we explore the use of three-dimensional spectral-domain optical coherence tomography (SD-OCT) to identify different follicular stages, compare the identifications with H&E images, and measure the size and age-related follicular density distribution differences in mice ovaries. We use the thickness of the layers of granulosa cells to differentiate primordial and primary follicles from secondary follicles. The measured dimensions and age-related follicular distribution agree well with histological images and physiological aging. Finally, we apply attenuation coefficient map analyses to significantly improve the image contrast and the contrast-to-noise ratio (p < 0.001), facilitating follicle identification and quantification. We conclude that SD-OCT is a promising method to noninvasively evaluate ovarian follicles for ovarian tissue cryopreservation.

Deep learning-enabled quantification of simultaneous PET/MRI for cell transplantation monitoring.

Current methods of in vivo imaging islet cell transplants for diabetes using magnetic resonance imaging (MRI) are limited by their low sensitivity. Simultaneous positron emission tomography (PET)/MRI has greater sensitivity and ability to visualize cell metabolism. However, this dual-modality tool currently faces two major challenges for monitoring cells. Primarily, the dynamic conditions of PET such as signal decay and spatiotemporal change in radioactivity prevent accurate quantification of the transplanted cell number. In addition, selection bias from different radiologists renders human error in segmentation. This calls for the development of artificial intelligence algorithms for the automated analysis of PET/MRI of cell transplantations. Here, we combined K-means++ for segmentation with a convolutional neural network to predict radioactivity in cell-transplanted mouse models. This study provides a tool combining machine learning with a deep learning algorithm for monitoring islet cell transplantation through PET/MRI. It also unlocks a dynamic approach to automated segmentation and quantification of radioactivity in PET/MRI.

Three-dimensional imaging and quantification of mouse ovarian follicles via optical coherence tomography.

Ovarian tissue cryopreservation has been successfully applied worldwide for fertility preservation. Correctly selecting the ovarian tissue with high follicle loading for freezing and reimplantation increases the likelihood of restoring ovarian function, but it is a challenging process. In this work, we explore the use of three-dimensional spectral-domain optical coherence tomography (SD-OCT) to identify different follicular stages, especially primary follicles, compare the identifications with H&E images, and measure the size and age-related follicular density distribution differences in mice ovaries. We use the thickness of the layers of granulosa cells to differentiate primordial and primary follicles from secondary follicles. The measured dimensions and age-related follicular distribution agree well with histological images and physiological aging. Finally, we apply attenuation coefficient map analyses to significantly improve the image contrast and the contrast-to-noise ratio (p < 0.001), facilitating follicle identification and quantification. We conclude that SD-OCT is a promising method to noninvasively evaluate ovarian follicles.

In Vivo Bioluminescence for the Detection of the Fate of Pancreatic Islet Organoids Post-transplantation.

Pancreatic islet transplantation is a promising cell replacement treatment for patients afflicted with type 1 diabetes (T1D), which is an autoimmune disease resulting in the destruction of insulin-producing islet ß-cells. However, the shortage of donor pancreatic islets significantly hampers the widespread application of this strategy as routine therapy. Pluripotent stem cell-derived insulin-producing islet organoids constitute a promising alternative ß-cell source for T1D patients. Early after transplantation, it is critical to know the fate of transplanted islet organoids, but determining their survival remains a significant technical challenge. Bioluminescence imaging (BLI) is an optical molecular imaging technique that detects the survival of living cells using light emitted from luciferase-expressing bioreporter cells. Through BLI, the post-transplantation fate of islet organoids can be evaluated over time in a noninvasive fashion with minimal intervention, thus making BLI an ideal tool to determine the success of the transplant and improving cell replacement therapy approaches for T1D.

Magnetic Particle Imaging of Transplanted Human Islets Using a Machine Learning Algorithm.

Human islet transplantation is a promising therapy to restore normoglycemia for type 1 diabetes (T1D). Despite recent advances, human islet transplantation remains suboptimal due to significant islet graft loss after transplantation. Various immunological and nonimmunological factors contribute to this loss therefore signifying a need for strategies and approaches for visualizing and monitoring transplanted human islet grafts. One such imaging approach is magnetic particle imaging (MPI), an emerging imaging modality that detects the magnetization of iron oxide nanoparticles. MPI is known for its specificity due to its high image contrast and sensitivity. MPI through its noninvasive nature provides the means for monitoring transplanted human islets in real time. Here we summarize an approach to track transplanted human islets using MPI. We label human islet from donors with dextran-coated ferucarbotran iron oxide nanoparticles, transplant the labeled human islet into under the left kidney capsule, and image graft cells using an MPI scanner. We engineer a K-means++, clustering-based unsupervised machine learning algorithm for standardized image segmentation and iron quantification of the MPI, which solves problems with selection bias and indiscriminate signal boundary that accompanies this newer imaging modality. In this chapter, we summarize the methods of this emerging imaging modality of MPI in conjunction with unsupervised machine learning to monitor and visualize islets after transplantation.

3D in vivo Magnetic Particle Imaging of Human Stem Cell-Derived Islet Organoid Transplantation Using a Machine Learning Algorithm.

Stem cell-derived islet organoids constitute a promising treatment of type 1 diabetes. A major hurdle in the field is the lack of appropriate in vivo method to determine graft outcome. Here, we investigate the feasibility of in vivo tracking of transplanted stem cell-derived islet organoids using magnetic particle imaging (MPI) in a mouse model. Human induced pluripotent stem cells-L1 were differentiated to islet organoids and labeled with superparamagnetic iron oxide nanoparticles. The phantoms comprising of different numbers of labeled islet organoids were imaged using an MPI system. Labeled islet organoids were transplanted into NOD/scid mice under the left kidney capsule and were then scanned using 3D MPI at 1, 7, and 28 days post transplantation. Quantitative assessment of the islet organoids was performed using the K-means++ algorithm analysis of 3D MPI. The left kidney was collected and processed for immunofluorescence staining of C-peptide and dextran. Islet organoids expressed islet cell markers including insulin and glucagon. Image analysis of labeled islet organoids phantoms revealed a direct linear correlation between the iron content and the number of islet organoids. The K-means++ algorithm showed that during the course of the study the signal from labeled islet organoids under the left kidney capsule decreased. Immunofluorescence staining of the kidney sections showed the presence of islet organoid grafts as confirmed by double staining for dextran and C-peptide. This study demonstrates that MPI with machine learning algorithm analysis can monitor islet organoids grafts labeled with super-paramagnetic iron oxide nanoparticles and provide quantitative information of their presence in vivo.

Artificial Intelligence Analysis of Magnetic Particle Imaging for Islet Transplantation in a Mouse Model.

PURPOSE: Current approaches to quantification of magnetic particle imaging (MPI) for cell-based therapy are thwarted by the lack of reliable, standardized methods of segmenting the signal from background in images. This calls for the development of artificial intelligence (AI) systems for MPI analysis. PROCEDURES: We utilize a canonical algorithm in the domain of unsupervised machine learning, known as K-means++, to segment the regions of interest (ROI) of images and perform iron quantification analysis using a standard curve model. We generated in vitro, in vivo, and ex vivo data using islets and mouse models and applied the AI algorithm to gain insight into segmentation and iron prediction on these MPI data. In vitro models included imaging the VivoTrax-labeled islets in varying numbers. In vivo mouse models were generated through transplantation of increasing numbers of the labeled islets under the kidney capsule of mice. Ex vivo data were obtained from the MPI images of excised kidney grafts. RESULTS: The K-means++ algorithms segmented the ROI of in vitro phantoms with minimal noise. A linear correlation between the islet numbers and the increasing prediction of total iron value (TIV) in the islets was observed. Segmentation results of the ROI of the in vivo MPI scans showed that with increasing number of transplanted islets, the signal intensity increased with linear trend. Upon segmenting the ROI of ex vivo data, a linear trend was observed in which increasing intensity of the ROI yielded increasing TIV of the islets. Through statistical evaluation of the algorithm performance via intraclass correlation coefficient validation, we observed excellent performance of K-means++-based model on segmentation and quantification analysis of MPI data. CONCLUSIONS: We have demonstrated the ability of the K-means++-based model to provide a standardized method of segmentation and quantification of MPI scans in an islet transplantation mouse model.

N-(2-18F-fluoropropionyl)-l-glutamate as a potential oncology tracer for PET imaging of glioma.

N-(2-18F-fluoropropionyl)-l-glutamate (18F-FPGLU), a new N-substituted 18F-labeling l-glutamate, is a potential amino acid tracer for oncology PET imaging with good tumor-to-background contrast in several tumor-bearing mice. Herein, we evaluated the potential value of 18F-FPGLU for PET imaging of glioma in orthotopic glioma-bearing SD rats. A series of competitive inhibition experiments with various types of inhibitors were conducted with C6 cells to investigate the transport mechanism of 18F-FPGLU in glioma. Establishment of orthotopic rat C6 glioma-bearing SD rats models was confirmed by MRI. Then PET imaging of 18F-FPGLU was performed on the orthotopic C6 glioma-bearing SD rats and compared with that of 18F-FDG. After the rats sacrificed, the whole brain was collected and immunofluorescence staining of glial fibrillary acidic protein (GFAP) and matrix metalloproteinase 2 (MMP2) were processed. Na+-dependent system XAG- and Na+-independent system XC- are the mainly transporters of 18F-FPGLU in C6 cells. N-methyl-d-aspartate (NMDA) receptor, which is associated with the invasiveness and proliferation of glioma cells, is also involved in the uptake of 18F-FPGLU. High uptake and retention of 18F-FPGLU was observerd in orthotopic glioma with good visualization and the tumor/background ratio reached 2.35 at 60 min post-injection, which was significantly higher than that of 18F-FDG (1.72) in small-animal PET images. High expression of MMP-2 and GFAP was observed in the immunofluorescence staining of glioma xerography slices. 18F-FPGLU seems to be a better potential PET tracer than 18F-FDG for brain glioma imaging with good visualization and ability to assess the tumor activity.

Current Progress and Perspective: Clinical Imaging of Islet Transplantation.

Islet transplantation has great potential as a cure for type 1 diabetes. At present; the lack of a clinically validated non-invasive imaging method to track islet grafts limits the success of this treatment. Some major clinical imaging modalities and various molecular probes, which have been studied for non-invasive monitoring of transplanted islets, could potentially fulfill the goal of understanding pathophysiology of the functional status and viability of the islet grafts. In this current review, we summarize the recent clinical studies of a variety of imaging modalities and molecular probes for non-invasive imaging of transplanted beta cell mass. This review also includes discussions on in vivo detection of endogenous beta cell mass using clinical imaging modalities and various molecular probes, which will be useful for longitudinally detecting the status of islet transplantation in Type 1 diabetic patients. For the conclusion and perspectives, we highlight the applications of multimodality and novel imaging methods in islet transplantation.

Excitatory glutamate transporter EAAC1 as an important transporter of N-(2-[18F]fluoropropionyl)-L-glutamate in oncology PET imaging.

INTRODUCTION: We have reported that N-(2-[18F]fluoropropionyl)-L-glutamate ([18F]FPGLU) was a potential amino acid tracer for tumor imaging with positron emission tomography (PET). In this study, the relationship between glutamate transporter excitatory amino acid carrier 1 (EAAC1) expression and [18F]FPGLU uptake in rat C6 glioma cell lines and human SPC-A-1 lung adenocarcinoma cell lines was investigated. METHODS: The uptake of [18F]FPGLU was assessed in ATRA-treated and untreated C6 cell lines, and also in EAAC1 knock-down SPC-A-1(shRNA) cells and SPC-A-1(NT) control cells. PET imaging of [18F]FPGLU was performed on the SPC-A-1 and SPC-A-1 (shRNA)-bearing mice models. RESULTS: The uptake of [18F]FPGLU in C6 cells increased significantly after induced by ATRA for 24, 48, and 72 h, which was closely related to expression of EAAC1 in C6 cells (R2 = 0.939). Compared with the SPC-A-1(NT) control cells, the uptake of [18F]FPGLU on EAAC1 knock-down SPC-A-1(shRNA) cells significantly decreased to 64.0%. Moreover, the uptake of [18F]FPGLU in EAAC1 knock-down SPC-A-1(shRNA) xenografts was significantly lower than that in SPC-A-1 xenografts, with tumor/muscle ratios of 3.01 vs. 1.67 at 60 min post-injection of [18F]FPGLU. CONCLUSION: The transport mechanism of [18F]FPGLU in glioma C6 and lung adenocarcinoma SPC-A-1 cell lines mainly involves in glutamate transporter EAAC1. EAAC1 is an important transporter of N-(2-[18F]fluoropropionyl)-L-glutamate in oncologic PET imaging.

Validation of R-2-[18F]Fluoropropionic Acid as a Potential Tracer for PET Imaging of Liver Cancer.

PURPOSE: 2-[18F]Fluoropropionic acid (RS-[18F]FPA) has shown potential value as a short-chain fatty acid positron emission tomography (PET) tracer for the detection of liver cancer. However, RS-[18F]FPA is a mixture of 2-R-[18F]fluoropropionic acid (R-[18F]FPA) and 2-S-[18F]fluoropropionic acid (S-[18F]FPA). The aim of this study is to validate the feasibility of R-[18F]FPA in preclinical PET imaging of liver cancer and to compare the use of R-[18F]FPA with that of RS-[18F]FPA and S-[18F]FPA. PROCEDURES: A comparative study of R-[18F]FPA, RS-[18F]FPA, S-[18F]FPA, and [18F]FDG micro-PET imaging was performed in HepG2 and SK-Hep-1 tumor-bearing mice. A comparison of R-[18F]FPA uptake with that of S-[18F]FPA by HepG2 and SK-Hep-1 cells was made at different time points. Additionally, in vivo blocking experiments in HepG2 and SK-Hep-1 tumor models were conducted with orlistat and 3-nitropropionic acid (3-NP). In vitro blocking experiments with orlistat or 3-NP were performed with HepG2 and SK-Hep-1 cells. RESULTS: The radioactivity uptake values of R-[18F]FPA were comparable to those of RS-[18F]FPA but were higher than those of S-[18F]FPA and 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) in HepG2 tumors. The radioactivity uptake values of R-[18F]FPA in large HepG2 tumors were lower than those of [18F]FDG (P < 0.05), while R-[18F]FPA PET was significantly superior to [18F]FDG PET in detecting small tumors (both SK-Hep-1 and HepG2 tumors). The in vivo PET imaging experiments showed that R-[18F]FPA uptake in HepG2 tumor-bearing mice was blocked by 19.3 % and 31.8 % after treatment with orlistat and 3-NP, respectively. The radioactivity uptake values of R-[18F]FPA in SK-Hep-1 tumor-bearing mice was blocked by 39.5 % with orlistat. CONCLUSION: R-[18F]FPA seems to be more potential than S-[18F]FPA as an optically pure PET probe, with effective compensation for the deficiencies of [18F]FDG, particularly in PET imaging of small liver cancer. The uptake mechanism of [18F]FPA in liver cancer may be related to fatty acid synthesis and the tricarboxylic acid cycle. However, compared with the racemic RS-[18F]FPA, the possible advantages of R-enantiomer R-[18F]FPA still needs further research.

Apoptotic PET Imaging of Rat Pulmonary Fibrosis with Small-Molecule Radiotracer.

PURPOSE: The purpose of this study was to assess the potential utility of small-molecule apoptotic radiotracer, 2-(5-[18F]fluoropentyl)-2-methyl malonic acid ([18F]ML-10), for positron emission tomography (PET)/computed tomography (CT) monitoring the progression of pulmonary fibrosis in a rat model. PROCEDURES: Male Sprague-Dawley rats were used to establish a rat model of pulmonary fibrosis by means of bleomycin (BLM) administration; control rats received saline (n = 12 per group). PET/CT with [18F]ML-10 and 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) was performed in two groups at different stages of pulmonary fibrosis. The fibrotic response and the cell apoptosis were assessed with histologic examination. Differences in the apoptosis rate, fibrotic activity, and the lung uptake of [18F]ML-10 and [18F]FDG between two groups were determined with Student t test. RESULTS: Compared with control group, BLM group showed a higher lung uptake of [18F]ML-10 at all imaging time points (all P < 0.001). During the fibrotic phase of this disease model (days 21 and 28), the lung uptake of [18F]ML-10 was higher than that of [18F]FDG in the BLM group (all P < 0.001). Moreover, accumulation of [18F]ML-10 in the lung tissues increased in proportion to the apoptosis rate (R2 = 0.9863, P < 0.0001) and fibrotic activity (R2 = 0.9631, P < 0.0001) of rat pulmonary fibrosis. Conversely, no correlation between [18F]FDG uptake and fibrotic activity was found. CONCLUSIONS: [18F]ML-10 PET/CT enabled monitoring the progression of rat pulmonary fibrosis, whereas [18F]FDG PET/CT could not. Implications for noninvasive diagnosis of pulmonary fibrosis, assessment of fibrotic activity, and evaluation of antifibrotic therapy are expected.

Apoptotic PET Imaging of Rat Pulmonary Fibrosis With [18F]ML-8.

OBJECTIVE: To investigate the value of 2-(3-[18F]fluoropropyl)-2-methyl-malonic acid ([18F]ML-8) positron emission tomography (PET) imaging of rat pulmonary fibrosis. METHODS: Male Sprague-Dawley rats were divided into 2 groups, including pulmonary fibrosis model group and control group. The rat model was established by an intratracheal instillation of bleomycin (BLM). Control rats were treated with saline. Positron emission tomography/computed tomography (CT) with [18F]ML-8 or 18F-fluorodeoxyglucose ([18F]FDG) was performed on 2 groups. After PET/CT imaging, lung tissues were collected for histologic examination. Data were analyzed and comparisons between 2 groups were performed using Student t test. RESULTS: Bleomycin-treated rats showed a higher lung uptake of [18F]ML-8 than control rats ( P < .05). In BLM-treated rats, the lung to muscle relative uptake ratio of [18F]ML-8 was also higher than that of [18F]FDG ( P < .05). Pathological examination showed overproliferation of fibroblasts and deposition of collagen in lungs from BLM-treated rats. Compared to control rats, BLM-treated rats had higher lung hydroxyproline content ( P < .05). Immunofluorescence staining indicated more apoptotic cells in BLM-treated rats than those in control rats. Moreover, the apoptosis rate of lung tissues obtained from BLM-treated rats was higher than that from control rats ( P < .05). CONCLUSIONS: 2-(3-[18F]fluoropropyl)-2-methyl-malonic acid PET/CT could be used for noninvasive diagnosis of pulmonary fibrosis in a rat model.

Positron Emission Tomography Imaging of Lesions pH Using 11C-Labeled Bicarbonate.

OBJECTIVES: As acid-base imbalance is involved in many pathological processes, the capability to image tissue pH alterations in the clinic could offer new ways to detect disease and respond to treatment. In this study, the authors show that tissue pH can be imaged in vivo with 11C-labeled bicarbonate (H11CO3-) buffer and positron emission tomography (PET). METHODS: H11CO3- was produced by on-column NaOH adsorption. Biodistribution of H11CO3- in normal mice was determined. In addition, uptake studies and inhibition experiments of H11CO3- in the S180 fibrosarcoma-bearing mice and the inflammatory mice were investigated with PET imaging. The tumor and inflammatory interstitial pH was measured by a needle pH microelectrode. RESULTS: PET imaging demonstrated the high uptake of H11CO3- in mice tumor tissues and inflammatory tissues, which showed that the average tumor or inflammatory interstitial pH was significantly lower than the surrounding tissue. Administration of sodium bicarbonate in the drinking water increased the measured tumor pH, while the uptake of H11CO3- in mice model tissues had no change. Similarly, administration with ammonium chloride (NH4Cl) decreased the pH, whereas the unchanged uptake of H11CO3- in mice model tissues was also found. However, after administration of acetazolamide, the low uptake of H11CO3- in mice model tissues was observed. CONCLUSIONS: H11CO3- solution is an endogenous bicarbonate buffer tracer that can be injected into patients without toxicity. H11CO3- PET can be used clinically to image pathological processes that are associated with acid-base imbalance, such as cancer and inflammation.

Efficacy and safety of apatinib combined with chemotherapy for the treatment of advanced gastric cancer in the Chinese population: a systematic review and meta-analysis.

OBJECTIVE: To systematically evaluate the efficacy and safety of the combination of apatinib targeted therapy and chemotherapy (CT) in the treatment of patients with advanced gastric cancer (GC). MATERIALS AND METHODS: Clinical trials were extracted from PubMed, the Cochrane Library, Web of Science, EMBASE, CNKI, and the Wanfang database. Outcome measures, including therapeutic efficacy, quality of life (QOL), and adverse events, were extracted and evaluated. RESULTS: Nineteen trials, including 1,256 advanced GC patients, were included. The results indicated that, compared with CT alone, the combination of apatinib targeted therapy with CT significantly improved the patients' complete response rate (OR=1.85, 95% CI=1.04-3.28, P=0.04), partial response rate (OR=2.19, 95% CI=1.71-2.80, P<0.00001), overall response (OR=2.57, 95% CI=1.99-3.32, P<0.00001), and disease control rate (OR=3.46, 95% CI=2.57-4.66, P<0.00001). Moreover, the combined therapy exhibited advantages over CT alone in the patients' QOL including the QOL improved rate (OR=1.77, 95% CI=0.94-3.33, P=0.08) and the Karnofsky performance score (OR=1.77, 95% CI=0.94-3.33, P=0.08). The group that received the combined therapy had higher rates of hypertension (OR=5.75, 95% CI=2.22-14.92, P=0.0003), albuminuria (OR=15.42, 95% CI=5.39-44.10, P<0.00001), and hand-foot syndrome (OR=2.09, 95% CI=1.26-3.48, P=0.004), whereas analyses of other adverse events, such as leucopenia, thrombocytopenia, and neutropenia, did not reveal significant differences (P>0.05). CONCLUSION: The combination of apatinib targeted therapy and CT is more effective for GC treatment than CT alone. However, this combined treatment could lead to greater rates of hypertension, albuminuria, and hand-foot syndrome. Therefore, the benefits and risks should be considered before treatment.

PET imaging of cardiomyocyte apoptosis in a rat myocardial infarction model.

Cardiomyocyte apoptosis has been observed in several cardiovascular diseases and contributes to the subsequent cardiac remodeling processes and progression to heart failure. Consequently, apoptosis imaging is helpful for noninvasively detecting the disease progression and providing treatment guidance. Here, we tested 18F-labeled 2-(5-fluoropentyl)-2-methyl-malonic acid (18F-ML-10) and 18F-labeled 2-(3-fluoropropyl)-2-methyl-malonic acid (18F-ML-8) for apoptosis imaging in rat models of myocardial infarction (MI) and compared them with 18F-fluorodeoxyglucose (18F-FDG). MI was induced in Sprague-Dawley rats by permanent left coronary artery ligation. Procedural success was confirmed by echocardiography and positron emission tomography (PET) imaging with 18F-FDG. In vivo PET imaging with 18F-ML-10 and 18F-ML-8 was performed in the MI models at different time points after operation. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assays and immunohistochemical analyses were used to evaluate myocardial apoptosis. In vitro cell binding assays were performed to validate 18F-ML-8 binding to apoptotic cardiomyocytes. PET imaging demonstrated high 18F-ML-10 and 18F-ML-8 uptake where 18F-FDG uptake was absent. The focal accumulation of the two tracers was high on days 1 and 3 but was not notable on days 5 and 7 after surgery. The infarct-to-lung uptake ratio was 4.29 ± 0.30 for 18F-ML-10 and 3.51 ± 0.18 for 18F-ML-8 (n = 6, analyzed by averaging the uptake ratios on postoperative days 1 and 3, P < 0.05). The TUNEL results showed that myocardial cell apoptosis was closely related to the focal uptake of the apoptotic tracers in the infarct area. In addition, the apoptosis rates calculated from the TUNEL results were better correlated with 18F-ML-8 uptake than with 18F-ML-10 uptake. Ex vivo cell binding assays demonstrated that 18F-ML-8 accumulated in apoptotic cells but not in necrotic or normal cells. PET imaging using 18F-ML-10 or 18F-ML-8 allows the noninvasive detection of myocardial apoptosis in the early phase. In addition, 18F-ML-8 may be better than 18F-ML-10 for apoptosis imaging. We propose that PET imaging with 18F-ML-10 or 18F-ML-8 combined with 18F-FDG is an alternative for detecting and assessing MI.

Essential genes of the macrophage response to Staphylococcus aureus exposure.

BACKGROUND: Although significant advances have been made in understanding the mechanisms of macrophage response to Staphylococcus aureus infection, the molecular details are still elusive. Identification of the essential genes and biological processes of macrophages that are specifically changed at different durations of S. aureus exposure is of great clinical significance. METHODS: We aimed to identify the significantly changed genes and biological processes of S. aureus-exposed macrophages. We systematically analyzed the macrophage gene expression profile GSE 13670 database with 8 h, 24 h or 48 h S. aureus infection. The results were further confirmed by western blot and quantitative polymerase chain reaction (qPCR) analyses. RESULTS: After 8 h of S. aureus infection, the expression of 624 genes was significantly changed. Six hundred thirteen differentially expressed genes (DEGs) were identified after 24 h of S. aureus infection. Two hundred fifty-three genes were significantly changed after 48 h of S. aureus infection. STAT1 was consistently up-regulated in these three treatments. TP53, JAK2, CEBPA, STAT3, MYC, CTNNB1 and PRKCA were only identified in the 8 h or 24 h S. aureus infection groups. CTNNB1 and PRKCA were for the first time identified as potential essential genes in S. aureus infection of macrophages. In the Gene Ontology (GO) term analysis, the defense response was shown to be the most significantly changed biological process among all processes; KEGG pathway analysis identified the JAK-STAT signaling pathway involved in early infection. CONCLUSIONS: Our systematic analysis identified unique gene expression profiles and specifically changed biological processes of the macrophage response to different S. aureus exposure times.