Automatic segmentation and plaque characterization in atherosclerotic carotid artery MR images

In vivo MRI provides a means to non-invasively image and assess the morphological features of atherosclerotic carotid arteries. To assess quantitatively the degree of vulnerability and the type of plaque, the contours of the lumen, outer boundary of the vessel wall and plaque components, need to be traced. Currently this is done manually, which is time-consuming and sensitive to inter- and intra-observer variability. The goal of this work was to develop an automated contour detection technique for tracing the lumen, outer boundary and plaque contours in carotid MR short-axis black-blood images. Seventeen patients with carotid atherosclerosis were imaged using high-resolution in vivo MRI, generating a total of 50 PD- and T1-weighted MR images. These images were automatically segmented using the algorithm presented in this work, which combines model-based segmentation and fuzzy clustering to detect the vessel wall, lumen and lipid core boundaries. The results demonstrate excellent correspondence between automatic and manual area measurements for lumen (r=0.92) and outer (r=0.91), and acceptable correspondence for fibrous cap thickness (r=0.71). Though further optimization is required, our algorithm is a powerful tool for automatic detection of lumen and outer boundaries, and characterization of plaque in atherosclerotic vessels.     

An optimum method designed for 2-D DIGE analysis of human arterial intima and media layers isolated by laser microdissection

The formation and progression of atherosclerotic lesions involve complex mechanisms which are still not fully understood. A variety of cell types from the distinct arterial layers are implicated in the whole process from lipid accumulation within the vascular wall to plaque development and final rupture. In the present work, we employ the combination of laser microdissection and pressure catapulting and 2-D DIGE saturation labeling to investigate the human intima and media sub-proteomes isolated from atherosclerotic (coronary and aorta) or non-atherosclerotic vessels (preatherosclerotic coronary arteries). Laser microdissection and pressure catapulting allows the specific isolation of regions of interest. In turn, DIGE saturation labeling overcomes the limitation of extensive microdissection times to recover the protein amount required to perform comparative 2-DE, particularly when dealing with tissue regions rich in myofilament proteins, which result in low protein recovery. The compatibility and optimum performance of both techniques were investigated in detail, paying special attention to tissue staining and protein solubilization. Since scarce amount of protein obtained from microdissected tissue made it impossible to directly perform protein identification from 2-DE spots by MS, we performed in-solution digestion followed by LC-MS/MS analysis of total protein extracts from intima and media in order to get an overall picture of protein composition. Proteins so identified confirm the nature of the isolated regions. Finally, similar spot resolution on 2-D DIGE gels was obtained for the different human artery types (coronary, aorta) and studied layers (intima, media), setting the basis for future clinical comparative studies.     

A Strategy for Atherosclerosis Image Segmentation by Using Robust Markers

The watersheds method is a powerful segmentation tool developed in mathematical morphology, which has the drawback of producing over-segmentation. In this paper, in order to prevent its over-segmentation, we present a strategy to obtain robust markers for image segmentation of atherosclerotic lesions of the thoracic aorta. In such sense, we introduced an algorithm, which was very useful in order to obtain the markers of the atherosclerotic lesions. Images were pre-processed using the Gauss filter and a contrast enhancement. The obtained results by using our strategy were validated calculating the false negatives (FN) and false positives (FP) according to criterion of physicians, where 0% for FN and less than 11% for FP were obtained. Extensive experimentation showed that, using real image data, the proposed strategy was very suitable for our application. These images will be subject to an additional morphometrical analysis in order to study automatically the atherosclerosis and its organic-consequences.     

Heme, heme oxygenase and ferritin in vascular endothelial cell injury

Iron-derived reactive oxygen species are implicated in the pathogenesis of numerous vascular disorders including atherosclerosis, microangiopathic hemolytic anemia, vasculitis, and reperfusion injury. One abundant source of redox active iron is heme, which is inherently dangerous when released from intracellular heme proteins. The present review concerns the involvement of heme in vascular endothelial cell damage and the strategies used by endothelium to minimize such damage. Exposure of endothelium to heme greatly potentiates cell killing mediated by polymorphonuclear leukocytes and other sources of reactive oxygen. Free heme also promotes the conversion of low-density lipoprotein (LDL) into cytotoxic oxidized products. Only because of its abundance, hemoglobin probably represents the most important potential source of heme within the vascular endothelium; hemoglobin in plasma, when oxidized, transfers heme to endothelium and LDL, thereby enhancing cellular susceptibility to oxidant-mediated injury. As a defense against such toxicity, upon exposure to heme or hemoglobin, endothelial cells up-regulate heme oxygenase-1 and ferritin. Heme oxygenase-1 is a heme-degrading enzyme that opens the porphyrin ring, producing biliverdin, carbon monoxide, and the most dangerous product - free redox active iron. The latter can be effectively controlled by ferritin via sequestration and ferroxidase activity. Ferritin serves as a protective gene by virtue of antioxidant, antiapoptotic, and antiproliferative actions. These homeostatic adjustments have been shown effective in the protection of endothelium against the damaging effects of exogenous heme and oxidants. The central importance of this protective system was recently highlighted by a child diagnosed with heme oxygenase-1 deficiency, who exhibited extensive endothelial damage.     

动脉硬化平滑肌细胞增殖和凋亡及其调节

为阐明动脉粥样硬化（ＡＳ）斑块发展与稳定的内在机制，围绕动脉增生内膜、ＡＳ斑块内平滑肌细胞（ＳＭＣ）增殖和凋亡密切相关的即刻早期基因（ｃ－ｆｏｓ、ｃ－ｊｕｎ、ｃ－ｍｙｃ）和相关基因（ｐ５３、ｂｃｌ－２、ｃ－ｓｉｓ）表达失衡和重调这一中心展开研究，提出血管ＳＭＣ增殖和凋亡是决定ＡＳ斑块发展的关键环节。     

脂联素对巨噬细胞ATP结合盒转运子A1表达及其功能的影响

目的探讨脂联素对巨噬细胞ATP结合盒转运子A1(ATP binding cassette transporter A1,ABCA1)及其上游调控因子肝脏X受体α(Liver X receptorα,LXRα)表达的影响及其在胆固醇逆转运(Reverse cholesterol transport,RCT)和抗动脉粥样硬化(Atherosclerosis,AS)中可能的作用机制。方法以不同浓度的脂联素(0、1、5、10μg/ml)体外培养巨噬细胞RAW264.7 24 h,RT-PCR法检测细胞中ABCA1和LXRα基因mRNA的转录水平,Western blot法检测细胞中ABCA1和LXRα蛋白的表达水平,闪烁计数法检测细胞内胆固醇的流出情况。结果脂联素能显著上调RAW264.7细胞中ABCA1和LXRα基因mRNA的转录水平及蛋白的表达水平(P<0.05),且呈浓度依赖性;脂联素能浓度依赖性地增加细胞内胆固醇的流出(P<0.05)。结论脂联素可通过LXRα途径上调巨噬细胞ABCA1基因的转录和翻译水平,促进胆固醇逆转运,延缓AS的发生、发展。