Experimental Biology for the Identification of Causal Pathways in Atherosclerosis

More than 60 genomic loci have been implicated by genome-wide association studies (GWAS) and exome-wide association studies as conferring an increased risk of myocardial infarction and coronary artery disease (CAD). However, the causal gene and variant is often unclear. Using the functional analysis of genetic variants in experimental animal models, we anticipate understanding which candidate gene at a specific locus is associated with atherosclerosis and revealing the underlying molecular and cellular mechanisms, ultimately leading to the identification of causal pathways in atherosclerosis and may provide novel therapeutic targets for the treatment of atherosclerotic cardiovascular disease.

Cell-free 3D scaffold with two-stage delivery of miRNA-26a to regenerate critical-sized bone defects

MicroRNAs (miRNAs) are being developed to enhance tissue regeneration. Here we show that a hyperbranched polymer with high miRNA-binding affinity and negligible cytotoxicity can self-assemble into nano-sized polyplexes with a 'double-shell' miRNA distribution and high transfection efficiency. These polyplexes are encapsulated in biodegradable microspheres to enable controllable two-stage (polyplexes and miRNA) delivery. The microspheres are attached to cell-free nanofibrous polymer scaffolds that spatially control the release of miR-26a. This technology is used to regenerate critical-sized bone defects in osteoporotic mice by targeting Gsk-3β to activate the osteoblastic activity of endogenous stem cells, thus addressing a critical challenge in regenerative medicine of achieving cell-free scaffold-based miRNA therapy for tissue engineering.

Nitro-fatty acids in cardiovascular regulation and diseases: characteristics and molecular mechanisms

Electrophilic nitro-fatty acids (NO2-FAs) are endogenously formed by redox reactions of nitric oxide ((.)NO)- and nitrite ((.)NO2)- derived nitrogen dioxide with unsaturated fatty acids. Nitration preferentially occurs on polyunsaturated fatty acids with conjugated dienes under physiological or pathophysiological conditions such as during digestion, metabolism and as adaptive inflammatory processes. Nitro-fatty acids are present in free and esterified forms achieving broad biodistribution in humans and experimental models. Structural, functional and biological characterization of NO2-FAs has revealed clinically relevant protection from inflammatory injury in a number of cardiovascular, renal and metabolic experimental models. NO2-FAs are engaged in posttranslational modifications (PTMs) of a selective redox sensitive pool of proteins and regulate key adaptive signaling pathways involved in cellular homeostasis and inflammatory response. Here, we review and update the biosynthesis, metabolism and signaling actions of NO2-FAs, highlighting their diverse protective roles relevant to the cardiovascular system.

Altered long non-coding RNA transcriptomic profiles in brain microvascular endothelium after cerebral ischemia

The brain endothelium is an important therapeutic target for the inhibition of cerebrovascular dysfunction in ischemic stroke. Previously, we documented the important regulatory roles of microRNAs in the cerebral vasculature, in particular the cerebral vascular endothelium. However, the functional significance and molecular mechanisms of other classes of non-coding RNAs in the regulation of cerebrovascular endothelial pathophysiology after stroke are completely unknown. Using RNA sequencing (RNA-seq) technology, we profiled long non-coding RNA (lncRNA) expressional signatures in primary brain microvascular endothelial cells (BMECs) after oxygen-glucose deprivation (OGD), an in vitro mimic of ischemic stroke conditions. After 16h of OGD exposure, the expression levels for 362 of the 10,677 lncRNAs analyzed changed significantly, including a total of 147 lncRNAs increased and 70 lncRNAs decreased by more than 2-fold. Among them, the most highly upregulated lncRNAs include Snhg12, Malat1, and lnc-OGD 1006, whereas the most highly downregulated lncRNAs include 281008D09Rik, Peg13, and lnc-OGD 3916. Alteration of the most highly upregulated/downregulated ODG-responsive lncRNAs was further confirmed in cultured BMECs after OGD as well as isolated cerebral microvessels in mice following transient middle cerebral artery occlusion (MCAO) and 24h reperfusion by the quantitative real-time PCR approach. Moreover, promoter analysis of altered ODG-responsive endothelial lncRNA genes by bioinformatics showed substantial transcription factor binding sites on lncRNAs, implying potential transcriptional regulation of those lncRNAs. These findings are the first to identify OGD-responsive brain endothelial lncRNAs, which suggest potential pathological roles for these lncRNAs in mediating endothelial responses to ischemic stimuli. Endothelial-selective lncRNAs may function as a class of novel master regulators in cerebrovascular endothelial pathologies after ischemic stroke.

Exome-wide association analysis reveals novel coding sequence variants associated with lipid traits in Chinese

Blood lipids are important risk factors for coronary artery disease (CAD). Here we perform an exome-wide association study by genotyping 12,685 Chinese, using a custom Illumina HumanExome BeadChip, to identify additional loci influencing lipid levels. Single-variant association analysis on 65,671 single nucleotide polymorphisms reveals 19 loci associated with lipids at exome-wide significance (P<2.69 × 10⁻⁷), including three Asian-specific coding variants in known genes (CETP p.Asp459Gly, PCSK9 p.Arg93Cys and LDLR p.Arg257Trp). Furthermore, missense variants at two novel loci—PNPLA3 p.Ile148Met and PKD1L3 p.Thr429Ser—also influence levels of triglycerides and low-density lipoprotein cholesterol, respectively. Another novel gene, TEAD2, is found to be associated with high-density lipoprotein cholesterol through gene-based association analysis. Most of these newly identified coding variants show suggestive association (P<0.05) with CAD. These findings demonstrate that exome-wide genotyping on samples of non-European ancestry can identify additional population-specific possible causal variants, shedding light on novel lipid biology and CAD.

An important risk factor for coronary artery disease is the level of blood lipids. Here the authors conduct an exome-wide association study in Chinese cohorts and identify three novel loci associated with lipid levels as well as three Asian-specific variants in known loci.

Ductile electroactive biodegradable hyperbranched polylactide copolymers enhancing myoblast differentiation

Myotube formation is crucial to restoring muscular functions, and biomaterials that enhance the myoblast differentiation into myotubes are highly desirable for muscular repair. Here, we report the synthesis of electroactive, ductile, and degradable copolymers and their application in enhancing the differentiation of myoblasts to myotubes. A hyperbranched ductile polylactide (HPLA) was synthesized and then copolymerized with aniline tetramer (AT) to produce a series of electroactive, ductile and degradable copolymers (HPLAAT). The HPLA and HPLAAT showed excellent ductility with strain to failure from 158.9% to 42.7% and modulus from 265.2 to 758.2 MPa. The high electroactivity of the HPLAAT was confirmed by UV spectrometer and cyclic voltammogram measurements. These HPLAAT polymers also showed improved thermal stability and controlled biodegradation rate compared to HPLA. Importantly, when applying these polymers for myotube formation, the HPLAAT significantly improved the proliferation of C2C12 myoblasts in vitro compared to HPLA. Furthermore, these polymers greatly promoted myogenic differentiation of C2C12 cells as measured by quantitative analysis of myotube number, length, diameter, maturation index, and gene expression of MyoD and TNNT. Together, our study shows that these electroactive, ductile and degradable HPLAAT copolymers represent significantly improved biomaterials for muscle tissue engineering compared to HPLA.

Derivation of Rabbit Embryonic Stem Cells from Vitrified-Thawed Embryos

The rabbit is a useful animal model for regenerative medicine. We previously developed pluripotent rabbit embryonic stem cell (rbESC) lines using fresh embryos. We also successfully cryopreserved rabbit embryos by vitrification. In the present work, we combined these two technologies to derive rbESCs using vitrified-thawed (V/T) embryos. We demonstrate that V/T blastocysts (BLs) can be used to derive pluripotent rbESCs with efficiencies comparable to those using fresh BLs. These ESCs are undistinguishable from the ones derived from fresh embryos. We tested the developmental capacity of rbESCs derived from V/T embryos by BL injection experiments and produced chimeric kits. Our work adds cryopreservation to the toolbox of rabbit stem cell research and applications and will greatly expand the available research materials for regenerative medicine in a clinically relevant animal model.

A Diet-Sensitive BAF60a-Mediated Pathway Links Hepatic Bile Acid Metabolism to Cholesterol Absorption and Atherosclerosis

Dietary nutrients interact with gene networks to orchestrate adaptive responses during metabolic stress. Here, we identify Baf60a as a diet-sensitive subunit of the SWI/SNF chromatin-remodeling complexes in the mouse liver that links the consumption of fat- and cholesterol-rich diet to elevated plasma cholesterol levels. Baf60a expression was elevated in the liver following feeding with a western diet. Hepatocyte-specific inactivation of Baf60a reduced bile acid production and cholesterol absorption, and attenuated diet-induced hypercholesterolemia and atherosclerosis in mice. Baf60a stimulates expression of genes involved in bile acid synthesis, modification, and transport through a CAR/Baf60a feedforward regulatory loop. Baf60a is required for the recruitment of the SWI/SNF chromatin-remodeling complexes to facilitate an activating epigenetic switch on target genes. These studies elucidate a regulatory pathway that mediates the hyperlipidemic and atherogenic effects of western diet consumption.

The Liver Clock Controls Cholesterol Homeostasis through Trib1 Protein-mediated Regulation of PCSK9/Low Density Lipoprotein Receptor (LDLR) Axis

Disruption of the body clock has been recognized as a risk factor for cardiovascular disease. How the circadian pacemaker interacts with the genetic factors associated with plasma lipid traits remains poorly understood. Recent genome-wide association studies have identified an expanding list of genetic variants that influence plasma cholesterol and triglyceride levels. Here we analyzed circadian regulation of lipid-associated candidate genes in the liver and identified two distinct groups exhibiting rhythmic and non-rhythmic patterns of expression during light-dark cycles. Liver-specific inactivation of Bmal1 led to elevated plasma LDL/VLDL cholesterol levels as a consequence of the disruption of the PCSK9/LDL receptor regulatory axis. Ablation of the liver clock perturbed diurnal regulation of lipid-associated genes in the liver and markedly reduced the expression of the non-rhythmically expressed gene Trib1. Adenovirus-mediated rescue of Trib1 expression lowered plasma PCSK9 levels, increased LDL receptor protein expression, and restored plasma cholesterol homeostasis in mice lacking a functional liver clock. These results illustrate an unexpected mechanism through which the biological clock regulates cholesterol homeostasis through its regulation of non-rhythmic genes in the liver.

Perhexiline activates KLF14 and reduces atherosclerosis by modulating ApoA-I production

Recent genome-wide association studies have revealed that variations near the gene locus encoding the transcription factor Krüppel-like factor 14 (KLF14) are strongly associated with HDL cholesterol (HDL-C) levels, metabolic syndrome, and coronary heart disease. However, the precise mechanisms by which KLF14 regulates lipid metabolism and affects atherosclerosis remain largely unexplored. Here, we report that KLF14 is dysregulated in the liver of 2 dyslipidemia mouse models. We evaluated the effects of both KLF14 overexpression and genetic inactivation and determined that KLF14 regulates plasma HDL-C levels and cholesterol efflux capacity by modulating hepatic ApoA-I production. Hepatic-specific Klf14 deletion in mice resulted in decreased circulating HDL-C levels. In an attempt to pharmacologically target KLF14 as an experimental therapeutic approach, we identified perhexiline, an approved therapeutic small molecule presently in clinical use to treat angina and heart failure, as a KLF14 activator. Indeed, in WT mice, treatment with perhexiline increased HDL-C levels and cholesterol efflux capacity via KLF14-mediated upregulation of ApoA-I expression. Moreover, perhexiline administration reduced atherosclerotic lesion development in apolipoprotein E-deficient mice. Together, these results provide comprehensive insight into the KLF14-dependent regulation of HDL-C and subsequent atherosclerosis and indicate that interventions that target the KLF14 pathway should be further explored for the treatment of atherosclerosis.

Patient-specific cardiovascular progenitor cells derived from integration-free induced pluripotent stem cells for vascular tissue regeneration

Tissue-engineered blood vessels (TEBVs) are promising in regenerating a live vascular replacement. However, the vascular cell source is limited, and it is crucial to develop a scaffold that accommodates new type of vascular progenitor cells and facilitates in vivo lineage specification of the cells into functional vascular smooth muscle cells (VSMCs) to regenerate vascular tissue. In the present study, integration-free human induced pluripotent stem cells (hiPSCs) were established from patient peripheral blood mononuclear cells through episomal vector nucleofection of reprogramming factors. The established hiPSCs were then induced into mesoderm-originated cardiovascular progenitor cells (CVPCs) with a highly efficient directed lineage specification method. The derived CVPCs were demonstrated to be able to differentiate into functional VSMCs. Subcutaneous implantation of CVPCs seeded on macroporous nanofibrous poly(l-lactide) scaffolds led to in vivo VSMC lineage specification and matrix deposition inside the scaffolds. In summary, we established integration-free patient-specific hiPSCs from peripheral blood mononuclear cells, derived CVPCs through directed lineage specification, and developed an advanced scaffold for these progenitor cells to further differentiate in vivo into VSMCs and regenerate vascular tissue in a subcutaneous implantation model. This study has established an efficient patient-specific approach towards in vivo regeneration of vascular tissue.

The effect of phospholipid composition of reconstituted HDL on its cholesterol efflux and anti-inflammatory properties

The goal of this study was to understand how the reconstituted HDL (rHDL) phospholipid (PL) composition affects its cholesterol efflux and anti-inflammatory properties. An ApoA-I mimetic peptide, 5A, was combined with either SM or POPC. Both lipid formulations exhibited similar in vitro cholesterol efflux by ABCA1, but 5A-SM exhibited higher ABCG1- and SR-BI-mediated efflux relative to 5A-POPC (P < 0.05). Injection of both rHDLs in rats resulted in mobilization of plasma cholesterol, although the relative potency was 3-fold higher for the same doses of 5A-SM than for 5A-POPC. Formation of preβ HDL was observed following incubation of rHDLs with both human and rat plasma in vitro, with 5A-SM inducing a higher extent of preβ formation relative to 5A-POPC. Both rHDLs exhibited anti-inflammatory properties, but 5A-SM showed higher inhibition of TNF-α, IL-6, and IL-1β release than did 5A-POPC (P < 0.05). Both 5A-SM and 5A-POPC showed reduction in total plaque area in ApoE(-/-) mice, but only 5A-SM showed a statistically significant reduction over placebo control and baseline (P < 0.01). The type of PL used to reconstitute peptide has significant influence on rHDL's anti-inflammatory and anti-atherosclerosis properties.

Abstract 335: Atheroma-specific Delivery of Synthetic High-density Lipoprotein Containing Sphingosine-1-phosphate for Modulation of Vascular Inflammation

Introduction: Sphingosine-1-phosphate (S1P) is a potent anti-inflammatory signaling lipid carried in the body by circulating HDL. HDL has been shown to exhibit anti-inflammatory activities through activation of endothelial nitric oxide synthase (eNOS) and subsequent production and release of nitric oxide (NO) by endothelial cells.

Objective: The aim of this study is to use synthetic HDL particles to selectively deliver S1P to the site of arterial plaques in order to exert anti-inflammatory activity and modulate the progression of atherosclerosis.

Methods/Results: Synthetic HDL (sHDL) particles were prepared using the ApoA1 mimetic peptide 22A (PVLDLFRELLNELLEALKQKLK), dipalmitoylphosphatidylcholine (DPPC) and sphingomyelin. We also prepared sHDL containing either the hydrophobic dye, DiD, or S1P to assess the capability of sHDL to effectively reach atheroma site and induce nitric oxide (NO) release, respectively. The purity of all particles was determined to be > 97% and average particle size was 9.6 ± 0.4 nm for all preparations. To measure sHDL accumulation in the plaque, ApoE -/- mice were intravenously injected with 0.2 mg/kg HDL-DiD. Whole aortas were excised and analysed by IVUS imaging system, revealing significant accumulation of sHDL-DiD in the atherosclerotic lesions. We then tested the ability of sHDL to deliver S1P in vitro and induce NO production by treating human umbilical vein endothelial cells (HUVEC) with 1 mg/mL of 22A-DPPC-sHDL containing 0, 0.05, 0.5, or 5 nmol/mL of S1P using free 22A peptide (1 mg/mL) and saline as controls, and analyzing media by ozone chemiluminescence. Blank sHDL particles increased NO production two-fold over controls (0.27 ± 0.02 μM for 22A-DPPC-sHDLDL, 0.13 ± 0.01 μM PBS and 0.14 ± 0.02 μM for 22A peptide), while HDL-S1P further increased NO release: 0.35 ± 0.03, 0.44 ± 0.01, and 0.59 ± 0.01 μM for HDL with 0.05, 0.5, and 5 nmol/mL S1P, respectively.

Conclusions: Our studies show that HDL is capable of delivering hydrophobic cargo to atherosclerotic plaques, making HDL a promising platform to deliver S1P for modulation vascular inflammation and atherosclerosis. In vitro studies have revealed that HDL-S1P is able to increase NO production 2 to 4-fold over saline control setting the basis for future in vivo studies.

Abstract 132: CETP Deficiency in Rabbits Protects High Fat High Cholesterol Diet Induced Atherosclerosis

CETP has been suggested as an effective and promising target for further reducing cardiovascular events through elevation of the HDL-C levels. The failure of Pfizer’s torcetrapib and Roche’s dalcetrapib raised the question whether increased HDL from pharmacological inhibition of CETP are cardioprotective. Because mice lack CETP naturally, we generated CETP knockout (KO) rabbits by Zinc-finger nucleases (ZFN) to gain insights onto CETP and HDL biology in CVD. The ZFN pairs target on exon 3 of rabbit CETP gene. By microinjection of ZFN mRNA into rabbit embryos, we generated 5 CETP knockout (CETPko) founder rabbits. The founder used for this study contained 4 nucleotides deletion in exon 3 that results in a premature stop codon. Western blot confirms that there is no detectable CETP protein in the homozygous CETPko rabbit plasma and liver. No CETP activity was detected in the CETPko rabbit plasma, consistent with their genotype. At the normal chow fed conditions, there is no significant difference between wild type and CETPko male rabbits in plasma HDLc and total cholesterol (TC) level; whereas female CETPko rabbits show 40 to 100% increase in both HDLc and TC levels compared to wild type ones. By sequential ultracentrifugation method to separate plasma lipoproteins, we found that there is much higher HDL3 component in female CETPko rabbits, but not in male CETPko ones, comparing to their WT age matched control. At the HFHC (3% soy bean oil and 0.3% cholesterol) diet fed conditions, both male and female CETPko rabbits show significantly lower level of TC and LDLc compared to wild type rabbits. At the same time, the HDLc levels are significantly higher in the CETPko rabbits. In addition, apoB depleted plasma from CETPko rabbit showed 2-fold increase in cholesterol efflux tested in human THP1 cells. Furthermore, we measured the atherosclerotic plaque in the rabbit aorta after 16 weeks HFHC diet treatment. The total gross lesion areas in CETPko rabbits were only one-third of those in the wild type rabbits. In conclusion, our study shows that genetic deficiency of CETP in rabbits has beneficial effects on enhancing HDL function and reducing atherosclerosis. Our work sheds light on CETP and HDL biology, and provides valuable information to the development of CETP drugs.

GREGOR: evaluating global enrichment of trait-associated variants in epigenomic features using a systematic, data-driven approach

MOTIVATION

The majority of variation identified by genome wide association studies falls in non-coding genomic regions and is hypothesized to impact regulatory elements that modulate gene expression. Here we present a statistically rigorous software tool GREGOR (Genomic Regulatory Elements and Gwas Overlap algoRithm) for evaluating enrichment of any set of genetic variants with any set of regulatory features. Using variants from five phenotypes, we describe a data-driven approach to determine the tissue and cell types most relevant to a trait of interest and to identify the subset of regulatory features likely impacted by these variants. Last, we experimentally evaluate six predicted functional variants at six lipid-associated loci and demonstrate significant evidence for allele-specific impact on expression levels. GREGOR systematically evaluates enrichment of genetic variation with the vast collection of regulatory data available to explore novel biological mechanisms of disease and guide us toward the functional variant at trait-associated loci.

AVAILABILITY AND IMPLEMENTATION

GREGOR, including source code, documentation, examples, and executables, is available at http://genome.sph.umich.edu/wiki/GREGOR.

CONTACT

cristen@umich.edu

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Krüpple-like factors in the central nervous system: novel mediators in stroke

Transcription factors play an important role in the pathophysiology of many neurological disorders, including stroke. In the past three decades, an increasing number of transcription factors and their related gene signaling networks have been identified, and have become a research focus in the stroke field. Krüppel-like factors (KLFs) are members of the zinc finger family of transcription factors with diverse regulatory functions in cell growth, differentiation, proliferation, migration, apoptosis, metabolism, and inflammation. KLFs are also abundantly expressed in the brain where they serve as critical regulators of neuronal development and regeneration to maintain normal brain function. Dysregulation of KLFs has been linked to various neurological disorders. Recently, there is emerging evidence that suggests KLFs have an important role in the pathogenesis of stroke and provide endogenous vaso-or neuro-protection in the brain's response to ischemic stimuli. In this review, we summarize the basic knowledge and advancement of these transcriptional mediators in the central nervous system, highlighting the novel roles of KLFs in stroke.

Abstract 72: Long Non-coding RNAs Mediate Cerebrovascular Endothelial Pathologies in Ischemic Stroke

The structural and functional changes in the cerebral endothelium during cerebral ischemia are well-known to affect the extent of ischemic brain injury and stroke outcome. Therefore, the brain endothelium becomes an important therapeutic target for the inhibition of cerebrovascular dysfunction in ischemic stroke. However, the regulatory mechanisms of cerebral endothelial dysfunction after cerebral ischemia remain largely unexplored. Previously we have documented the important regulatory roles of microRNAs in the cerebral vasculature, in particular the cerebral vascular endothelium. However, the functional significance and molecular mechanisms of other classes of non-coding RNAs in the regulation of cerebrovascular endothelial pathophysiology after stroke are completely unknown.

Using RNA-sequencing technology, we profiled long non-coding RNAs (lncRNAs) expressional signatures in primary brain microvascular endothelial cells (BMECs) after oxygen-glucose deprivation (OGD). After 16h of OGD exposure, the expression levels for 362 of the 10,677 lncRNAs analyzed changed significantly, including a total of 147 lncRNAs increased and 70 lncRNAs decreased by more than 2-fold. Interestingly, metastasis associated lung adenocarcinoma transcript 1 (Malat1) is one of the most highly upregulated OGD-responsive endothelial lncRNAs, which has been initially discovered as a tumor-associated lncRNA involved in epigenetic control of gene expression. Increased Malat1 levels were further confirmed in cultured BMECs after OGD as well as isolated cerebral microvessels in mice after 1h MCAO and 24h reperfusion by qPCR. Of note, Malat1 was not pathologically increased in whole mouse brains in response to the same ischemic insult. The expression and nuclear localization of Malat1 were also shown in BMECs by in situ hybridization. Furthermore, loss-of-Malat1 function by LNA-GapmeR significantly increased OGD-induced loss of endothelial markers and endothelial inflammation in BMECs, implying Malat1 a critical role in protecting the cerebral microvasculature from cerebral ischemic insults. These findings suggest that lncRNAs may function as a class of novel master regulators in cerebrovascular endothelial pathologies after ischemic stroke.

Rabbit models for the study of human atherosclerosis: from pathophysiological mechanisms to translational medicine

Laboratory animal models play an important role in the study of human diseases. Using appropriate animals is critical not only for basic research but also for the development of therapeutics and diagnostic tools. Rabbits are widely used for the study of human atherosclerosis. Because rabbits have a unique feature of lipoprotein metabolism (like humans but unlike rodents) and are sensitive to a cholesterol diet, rabbit models have not only provided many insights into the pathogenesis and development of human atherosclerosis but also made a great contribution to translational research. In fact, rabbit was the first animal model used for studying human atherosclerosis, more than a century ago. Currently, three types of rabbit model are commonly used for the study of human atherosclerosis and lipid metabolism: (1) cholesterol-fed rabbits, (2) Watanabe heritable hyperlipidemic rabbits, analogous to human familial hypercholesterolemia due to genetic deficiency of LDL receptors, and (3) genetically modified (transgenic and knock-out) rabbits. Despite their importance, compared with the mouse, the most widely used laboratory animal model nowadays, the use of rabbit models is still limited. In this review, we focus on the features of rabbit lipoprotein metabolism and pathology of atherosclerotic lesions that make it the optimal model for human atherosclerotic disease, especially for the translational medicine. For the sake of clarity, the review is not an attempt to be completely inclusive, but instead attempts to summarize substantial information concisely and provide a guideline for experiments using rabbits.

Angiogenesis-regulating microRNAs and Ischemic Stroke

Stroke is a leading cause of death and disability worldwide. Ischemic stroke is the dominant subtype of stroke and results from focal cerebral ischemia due to occlusion of major cerebral arteries. Thus, the restoration or improvement of reduced regional cerebral blood supply in a timely manner is very critical for improving stroke outcomes and poststroke functional recovery. The recovery from ischemic stroke largely relies on appropriate restoration of blood flow via angiogenesis. Newly formed vessels would allow increased cerebral blood flow, thus increasing the amount of oxygen and nutrients delivered to affected brain tissue. Angiogenesis is strictly controlled by many key angiogenic factors in the central nervous system, and these molecules have been well-documented to play an important role in the development of angiogenesis in response to various pathological conditions. Promoting angiogenesis via various approaches that target angiogenic factors appears to be a useful treatment for experimental ischemic stroke. Most recently, microRNAs (miRs) have been identified as negative regulators of gene expression in a post-transcriptional manner. Accumulating studies have demonstrated that miRs are essential determinants of vascular endothelial cell biology/angiogenesis as well as contributors to stroke pathogenesis. In this review, we summarize the knowledge of stroke-associated angiogenic modulators, as well as the role and molecular mechanisms of stroke-associated miRs with a focus on angiogenesis-regulating miRs. Moreover, we further discuss their potential impact on miR-based therapeutics in stroke through targeting and enhancing post-ischemic angiogenesis.

Telomere elongation and naive pluripotent stem cells achieved from telomerase haplo-insufficient cells by somatic cell nuclear transfer

Haplo-insufficiency of telomerase genes in humans leads to telomere syndromes such as dyskeratosis congenital and idiopathic pulmonary fibrosis. Generation of pluripotent stem cells from telomerase haplo-insufficient donor cells would provide unique opportunities toward the realization of patient-specific stem cell therapies. Recently, pluripotent human embryonic stem cells (ntESCs) have been efficiently achieved by somatic cell nuclear transfer (SCNT). We tested the hypothesis that SCNT could effectively elongate shortening telomeres of telomerase haplo-insufficient cells in the ntESCs with relevant mouse models. Indeed, telomeres of telomerase haplo-insufficient (Terc(+/-)) mouse cells are elongated in ntESCs. Moreover, ntESCs derived from Terc(+/-) cells exhibit naive pluripotency as evidenced by generation of Terc(+/-) ntESC clone pups by tetraploid embryo complementation, the most stringent test of naive pluripotency. These data suggest that SCNT could offer a powerful tool to reprogram telomeres and to discover the factors for robust restoration of telomeres and pluripotency of telomerase haplo-insufficient somatic cells.

Imaging body fat: techniques and cardiometabolic implications

Obesity is a worldwide epidemic and is associated with multiple comorbidities. The mechanisms underlying the relationship between obesity and adverse health outcomes remain poorly understood. This may be because of several factors including the crude measures used to estimate adiposity, the striking heterogeneity between adipose tissue depots, and the influence of fat accumulation in multiple organs. To advance our understanding of fat stores and associated comorbidities in humans, it will be necessary to image adiposity throughout the body and ultimately also assess its functionality. Large clinical studies are demonstrating the prognostic importance of adipose tissue imaging. Newer techniques capable of imaging fat metabolism and other functions of adipose tissue may provide additional prognostic use and may be useful in guiding therapeutic interventions.

Engineering vascular tissue with functional smooth muscle cells derived from human iPS cells and nanofibrous scaffolds

Tissue-engineered blood vessels (TEBVs) are promising in the replacement of diseased vascular tissues. However, it remains a great challenge to obtain a sufficient number of functional smooth muscle cells (SMCs) in a clinical setting to construct patient-specific TEBVs. In addition, it is critical to develop a scaffold to accommodate these cells and retain their functional phenotype for the regeneration of TEBVs. In this study, human induced pluripotent stem cells (iPSCs) were established from primary human aortic fibroblasts, and characterized with the pluripotency markers expression and cells' capabilities to differentiate into all three germ layer cells. A highly efficient method was then developed to induce these human iPSCs into proliferative SMCs. After multiple times of expansion, the expanded SMCs retained the potential to be induced into the functional contractile phenotype of mature SMCs, which was characterized by the contractile response to carbachol treatment, up-regulation of specific collagen genes under transforming growth factor β1 treatment, and up-regulation of specific matrix metalloproteinase genes under cytokine stimulation. We also developed an advanced macroporous and nanofibrous (NF) poly(l-lactic acid) (PLLA) scaffold with suitable pore size and interpore connectivity to seed these human iPSC-derived SMCs and maintain their differentiated phenotype. Subcutaneous implantation of the SMC-scaffold construct in nude mice demonstrated vascular tissue formation, with robust collagenous matrix deposition inside the scaffold and the maintenance of differentiated SMC phenotype. Taken together, this study established an exciting approach towards the construction of patient-specific TEBVs. We established patient-specific human iPSCs, derived proliferative SMCs for expansion, turned on their mature contractile SMC phenotype, and developed an advanced scaffold for these cells to regenerate vascular tissue in vivo.

Perivascular adipose tissue in vascular function and disease: a review of current research and animal models

Perivascular adipose tissue (PVAT), long assumed to be nothing more than vessel-supporting connective tissue, is now understood to be an important, active component of the vasculature, with integral roles in vascular health and disease. PVAT is an adipose tissue with similarities to both brown and white adipose tissue, although recent evidence suggests that PVAT develops from its own precursors. Like other adipose tissue depots, PVAT secretes numerous biologically active substances that can act in both autocrine and paracrine fashion. PVAT has also proven to be involved in vascular inflammation. Although PVAT can support inflammation during atherosclerosis via macrophage accumulation, emerging evidence suggests that PVAT also has antiatherosclerotic properties related to its abilities to induce nonshivering thermogenesis and metabolize fatty acids. We here discuss the accumulated knowledge of PVAT biology and related research on models of hypertension and atherosclerosis.

Abstract 302: Generation of Patient-Specific Tissue-Engineered Blood Vessels From Nonintegrated Induced Pluripotent Stem Cells

Cell resourcing remains one of the major problems in the development of patient-specific TEBVs. The iPSC derived cardiovascular cells provide a promising source for TEBVs and cell therapy. The goal of this study is to construct TEBVs using patient-specific iPSCs.

Using a non-integrated episomal vector based reprogramming system, we generated human iPSCs from peripheral blood mononuclear cells (PBMCs) isolated from the blood harvested from aneurysm patients with bicuspid aortic valves and coronary artery bypass patients with normal aortas and aortic valves. These iPSCs showed the expression of pluripotent markers and could differentiate into 3 layers of cells in vitro. We directed the iPSCs differentiation into vascular smooth muscle cells (VSMCs) in vitro. We documented the expression of VSMC markers, including smooth muscle α-actin (α-SMA), calponin and SM22α by quantitative real-time-PCR, immunocytochemistry, as well as Western-blotting. Furthermore, we confirmed that the iPSC-derived VSMCs could contract in response to carbachol, a muscarinic agonist. The treatment of iPSC-derived VSMCs with IL-1β, an atherogenic cytokine, changed MMPs (matrix metallopeptidases) activity. Finally, we found that iPSC-derived VSMCs could survive well and secrete collagen when transferred and cultured on PLLA scaffolds in vitro, suggesting a great cell sourcing for tissue-engineered blood vessels.

Our data suggests that by using non-integrated iPSCs, we could efficiently differentiate patient-specific iPSCs into functional VSMCs, which may provide great cell sourcing for patient-specific TEBVs.

Non-coding RNAs in cerebral endothelial pathophysiology: emerging roles in stroke

Cerebral vascular endothelial cells form the major element of the blood-brain barrier (BBB) and constitute the primary interface between circulating blood and brain parenchyma. The structural and functional changes in cerebral endothelium during cerebral ischemia are well known to result in BBB disruption, vascular inflammation, edema, and angiogenesis. These complex pathological processes directly contribute to brain infarction, neurological deficits, and post-stroke neurovascular remodeling. Ischemic endothelial dysfunction appears to be tightly controlled by multiple gene signaling networks. Non-coding RNAs (ncRNAs) are functional RNA molecules that are generally not translated into proteins but can actively regulate the expression and function of many thousands of protein-coding genes by different mechanisms. Various classes of ncRNAs, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), small nucleolar RNAs (snoRNAs) and piwi-interacting RNAs (piRNAs), are highly expressed in the cerebrovascular endothelium where they serve as critical mediators to maintain normal cerebral vascular functions. Dysregulation of ncRNA activities has been closely linked to the pathophysiology of cerebral vascular endothelium and neurologic functional disorders in the brain's response to ischemic stimuli. In this review, we summarize recent advancements of these ncRNA mediators in the brain vasculature, highlighting the specific roles of endothelial miRNAs in stroke.