BackgroundThe adipose tissue is an endocrine regulator and a risk factor for atherosclerosis and cardiovascular disease when by excessive accumulation induces obesity. Although the adipose tissue is also a reservoir for stem cells (ASC) their function and “stemcellness” has been questioned. Our aim was to investigate the mechanisms by which obesity affects subcutaneous white adipose tissue (WAT) stem cells.ResultsTranscriptomics, in silico analysis, real-time polymerase chain reaction (PCR) and western blots were performed on isolated stem cells from subcutaneous abdominal WAT of morbidly obese patients (ASCmo) and of non-obese individuals (ASCn). ASCmo and ASCn gene expression clustered separately from each other. ASCmo showed downregulation of “stemness” genes and upregulation of adipogenic and inflammatory genes with respect to ASCn. Moreover, the application of bioinformatics and Ingenuity Pathway Analysis (IPA) showed that the transcription factor Smad3 was tentatively affected in obese ASCmo. Validation of this target confirmed a significantly reduced Smad3 nuclear translocation in the isolated ASCmo.ConclusionsThe transcriptomic profile of the stem cells reservoir in obese subcutaneous WAT is highly modified with significant changes in genes regulating stemcellness, lineage commitment and inflammation. In addition to body mass index, cardiovascular risk factor clustering further affect the ASC transcriptomic profile inducing loss of multipotency and, hence, capacity for tissue repair. In summary, the stem cells in the subcutaneous WAT niche of obese patients are already committed to adipocyte differentiation and show an upregulated inflammatory gene expression associated to their loss of stemcellness.

Objective-Low-density lipoprotein (LDL) receptor-related protein (LRP1) mediates the internalization of aggregated LDL (agLDL)-LDL trapped in the arterial intima bound to proteoglycans-into human vascular smooth muscle cells (VSMC). LRP1-mediated agLDL uptake induces high-intracellular cholesteryl ester (CE) accumulation. The aim of this study was to characterize the mechanism of agLDL internalization in human VSMC. Methods and Results-The lipidic component of LDL was labeled with [ 3 H] and the apolipoprotein component with [ 125 I]. We found that 90% of intracellular CE derived from agLDL uptake was not associated with apoB100 degradation but was selectively taken up from agLDL. The inhibition of LRP1 expression by small interfering RNA treatment led to a decrease of 800.05% in agLDL-CE selective uptake. AgLDL induced intracellular CE accumulation without a concomitant CE synthesis. Cytosolic and cytoskeletal proteins were not required for CE transport. Electron and confocal microscopy experiments indicate that CE derived from agLDL accumulated in adipophilin-stained lipid droplets that were not removable by high-density lipoprotein. Conclusions-Taken together, these results demonstrate that LRP1 mediates the selective uptake of CE from agLDL and that CE derived from agLDL is not intracellularly processed but stored in lipid droplets in human VSMC. (Arterioscler Thromb Vasc Biol. 2006;26:117-123.) Key Words: LRP1 selective uptake cholesteryl ester adipophilin aggregated LDL O ne of the main events in the atherogenic process is the accumulation of lipids, mainly cholesteryl esters (CEs), in the subendothelial space of the arterial wall. 1-3 Macro-phages become foam cells through uptake of diversely modified low-density lipoprotein (LDL), whereas aggrega-tion of LDL (agLDL) seems to be a key condition for lipid accumulation in vascular smooth muscle cells (VSMCs). 4,5 We have demonstrated previously that the pattern of agLDL internalization differs from that of native LDL (nLDL) in human VSMC. Endocytosed nLDL were found in bright vesicles that were homogenously distributed in the perinu-clear space, leading to an unstained cytoplasm surrounding the fluorescent vesicles. In contrast, agLDLs were found in bigger and more diffuse structures distributed throughout the cytoplasm. 5 Contrarily to nLDL, agLDL was shown to be a strong inducer of intracellular CE accumulation in human VSMC. 5-8 These findings are related to differences in the internalization mechanisms; whereas nLDL is taken up by the endocytic LDL receptor (LDLr), which is downregulated by intracellular cholesterol, agLDL is taken up through LDLr-related protein (LRP1). 6,7 Uptake of agLDL through LRP1 allows high-intracellular CE accumulation not only because of its high capacity to bind and internalize agLDL but also because of its transcriptional upregulation by intracellular cholesterol. 8 LRP1 collaborates with heparan sulfate proteo-glycans (HS-PGs) to mediate the internalization of certain ligands. 9,10 However, in human VSMC, we have demonstrat...

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Background-Tissue factor (TF) is the main initiator of the arterial blood coagulation system, and aggregated LDL (agLDL) are found in the arterial intima. Our hypothesis is that agLDL internalization by vascular smooth muscle cells (VSMCs) may trigger TF-procoagulant activity.