LRP1 protects against excessive superior mesenteric artery remodeling by modulating angiotensin II-mediated signaling.

Vascular smooth muscle cells (vSMCs) exert a critical role in sensing and maintaining vascular integrity. These cells abundantly express the low-density lipoprotein receptor-related protein 1 (LRP1), a large endocytic signaling receptor that recognizes numerous ligands, including apolipoprotein E-rich lipoproteins, proteases, and protease-inhibitor complexes. We observed the spontaneous formation of aneurysms in the superior mesenteric artery (SMA) of both male and female mice in which LRP1 was genetically deleted in vSMCs (smLRP1-/- mice). Quantitative proteomics revealed elevated abundance of several proteins in smLRP1-/- mice that are known to be induced by angiotensin II-mediated (AngII-mediated) signaling, suggesting that this pathway was dysregulated. Administration of losartan, an AngII type I receptor antagonist, or an angiotensinogen antisense oligonucleotide to reduce plasma angiotensinogen concentrations restored the normal SMA phenotype in smLRP1-/- mice and prevented aneurysm formation. Additionally, using a vascular injury model, we noted excessive vascular remodeling and neointima formation in smLRP1-/- mice that was restored by losartan administration. Together, these findings reveal that LRP1 regulates vascular integrity and remodeling of the SMA by attenuating excessive AngII-mediated signaling.

Regulation of tau internalization, degradation, and seeding by LRP1 reveals multiple pathways for tau catabolism.

In Alzheimer's disease (AD), pathological forms of tau are transferred from cell to cell and "seed" aggregation of cytoplasmic tau. Phosphorylation of tau plays a key role in neurodegenerative tauopathies. In addition, apolipoprotein E (apoE), a major component of lipoproteins in the brain, is a genetic risk determinant for AD. The identification of the apoE receptor, low-density lipoprotein receptor-related protein 1 (LRP1), as an endocytic receptor for tau raises several questions about the role of LRP1 in tauopathies: is internalized tau, like other LRP1 ligands, delivered to lysosomes for degradation, and does LRP1 internalize pathological tau leading to cytosolic seeding? We found that LRP1 rapidly internalizes 125I-labeled tau, which is then efficiently degraded in lysosomal compartments. Surface plasmon resonance experiments confirm high affinity binding of tau and the tau microtubule-binding domain to LRP1. Interestingly, phosphorylated forms of recombinant tau bind weakly to LRP1 and are less efficiently internalized by LRP1. LRP1-mediated uptake of tau is inhibited by apoE, with the apoE4 isoform being the most potent inhibitor, likely because of its higher affinity for LRP1. Employing post-translationally-modified tau derived from brain lysates of human AD brain tissue, we found that LRP1-expressing cells, but not LRP1-deficient cells, promote cytosolic tau seeding in a process enhanced by apoE. These studies identify LRP1 as an endocytic receptor that binds and processes monomeric forms of tau leading to its degradation and promotes seeding by pathological forms of tau. The balance of these processes may be fundamental to the spread of neuropathology across the brain in AD.

Optimal Medical Management Reduces Risk of Disease Progression and Ischemic Events in Asymptomatic Carotid Stenosis Patients: A Long-Term Follow-Up Study.

BACKGROUND AND PURPOSE: To assess the effect of optimal medical management including atherosclerotic risk factor control on ischemic stroke (IS), transient ischemic attack (TIA), carotid revascularization (CRV), and progression of severity of carotid stenosis (PSCS) in patients with asymptomatic carotid artery stenosis (ACAS). METHODS: We conducted a retrospective analysis of patients with ACAS (who had at least 3 serial carotid duplex ultrasounds) for incidence of IS, TIA, and PSCS. RESULTS: Eight hundred sixty-four patients with a mean follow-up duration of 79 ± 36 months were included. IS/TIA and CRV occurred in 12.2% of the patients and PCSS was observed in 21.5% vessels. On univariate analysis it was found that low-density lipoprotein (LDL) levels >100 mg/dL, no statin or low-potency statins, average systolic blood pressure (SBP) ≥140 mm Hg and/or diastolic blood pressure (DBP) ≥90 mm Hg and history of smoking were predictors of the combined endpoint of IS/TIA/CRV and PSCS. On multivariate analysis, it was found that LDL >100 mg/dL, no statin or low-potency statin, SBP ≥140 mm Hg and/or DBP ≥90 mm Hg, and Hx of smoking were independent predictors of PSCS. Similarly no statin or low-potency statin, SBP ≥140 mm Hg and/or DBP ≥90 mm Hg, Hx of atrial fibrillation/flutter, Hx of chronic kidney disease, and PSCS were independent predictors of IS/TIA. No statin or low-potency statin, SBP ≥140 mm Hg and/or DBP ≥90 mm Hg, diabetes mellitus, baseline carotid artery stenosis ≥70%, and PSCS were found to be independent predictors of combined endpoint IS/TIA and CRV. CONCLUSION: Intensive medical therapy in the patients with ACAS results in lower incidence of IS/TIA, CRV, and PSCS with a significant incremental beneficial effect.

Ultrastructural features of ischemic tissue following application of a bio-membrane based progenitor cardiomyocyte patch for myocardial infarction repair.

BACKGROUND AND OBJECTIVE: Implantation of cell-sheets into damaged regions of the heart after myocardial infarction (MI) has been shown to improve heart function. However, the tissue morphology following application of induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CM) has not been studied in detail at the level afforded by electron microscopy. We hypothesized that increasing the number of CM derived from iPSC would increase the effectiveness of cell-sheets used to treat ischemic cardiomyopathy. We report here on the ultrastructural features after application of a bio-membrane 'cell patch'. METHODS: iPSC-derived progenitor cells were transduced using lentivirus vectors with or without NCX1 promoter. iPSC-CM sheets were transplanted over the transmural MI region in a mouse model of regional ischemic cardiomyopathy. Mice were divided into four groups, 1) Sham; 2) MI; 3) MI + iPSC without NCX1 treated cells (MI + iPSCNull) and 4) MI + iPSC receiving NCX1 promoter treated cells (MI + iPSCNCX1). Echocardiography was performed 4 weeks after cell patch application, followed by histological and transmission electron microscopy (TEM) analysis. RESULTS: Large numbers of transplanted CM were observed with significant improvements in left ventricular performance and remodeling in group 4 as compared with group 3. No teratoma formation was detected in any of the treatment groups. CONCLUSION: Manipulation of iPSC yields large numbers of iPSC-CM and favorable morphological and ultrastructural tissue changes. These changes have the potential to enhance current methods used for restoration of cardiac function after MI.

MicroRNA-377 regulates mesenchymal stem cell-induced angiogenesis in ischemic hearts by targeting VEGF.

MicroRNAs have been appreciated in various cellular functions, including the regulation of angiogenesis. Mesenchymal-stem-cells (MSCs) transplanted to the MI heart improve cardiac function through paracrine-mediated angiogenesis. However, whether microRNAs regulate MSC induced angiogenesis remains to be clarified. Using microRNA microarray analysis, we identified a microRNA expression profile in hypoxia-treated MSCs and observed that among all dysregulated microRNAs, microRNA-377 was decreased the most significantly. We also validated that vascular endothelial growth factor (VEGF) is a target of microRNA-377 using dual-luciferase reporter assay and Western-blotting. Knockdown of endogenous microRNA-377 promoted tube formation in human umbilical vein endothelial cells. We then engineered rat MSCs with lentiviral vectors to either overexpress microRNA-377 (MSC miR-377) or knockdown microRNA-377 (MSC Anti-377) to investigate whether microRNA-377 regulated MSC-induced myocardial angiogenesis, using MSCs infected with lentiviral empty vector to serve as controls (MSC Null). Four weeks after implantation of the microRNA-engineered MSCs into the infarcted rat hearts, the vessel density was significantly increased in MSC Anti-377-hearts, and this was accompanied by reduced fibrosis and improved myocardial function as compared to controls. Adverse effects were observed in MSC miR-377-treated hearts, including reduced vessel density, impaired myocardial function, and increased fibrosis in comparison with MSC Null-group. These findings indicate that hypoxia-responsive microRNA-377 directly targets VEGF in MSCs, and knockdown of endogenous microRNA-377 promotes MSC-induced angiogenesis in the infarcted myocardium. Thus, microRNA-377 may serve as a novel therapeutic target for stem cell-based treatment of ischemic heart disease.

Ischemic preconditioning potentiates the protective effect of stem cells through secretion of exosomes by targeting Mecp2 via miR-22.

Mesenchymal stem cells (MSCs) have potential application for the treatment of ischemic heart diseases. Besides differentiation properties, MSCs protect ischemic cardiomyocytes by secretion of paracrine factors. In this study, we found exosomes enriched with miR-22 were secreted by MSCs following ischemic preconditioning (Exo(IPC)) and mobilized to cardiomyocytes where they reduced their apoptosis due to ischemia. Interestingly, by time-lapse imaging, we for the first time captured the dynamic shedding of miR-22 loaded exosomes from cytosol to extracellular space. Furthermore, the anti-apoptotic effect of miR-22 was mediated by direct targeting of methyl CpG binding protein 2 (Mecp2). In vivo data showed that delivery of Exo(IPC) significantly reduced cardiac fibrosis. Our data identified a significant benefit of Exo(IPC) for the treatment of cardiac diseases by targeting Mecp2 via miR-22.