Lucy Liaw

Tufts University, Бостон, Georgia, United States

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Publications (105)548.22 Total impact

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    ABSTRACT: Mutations in endoglin, a TGFβ/BMP coreceptor, are causal for hereditary hemorrhagic telangiectasia (HHT). Endoglin-null (Eng-/-) mouse embryos die at embryonic day (E)10.5-11.5 due to defects in angiogenesis. In part, this is due to an absence of vascular smooth muscle cell differentiation and vessel investment. Prior studies from our lab and others have shown the importance of endoglin expression in embryonic development in both endothelial cells and neural crest stem cells. These studies support the hypothesis that endoglin may play cell-autonomous roles in endothelial and vascular smooth muscle cell precursors. However, the requirement for endoglin in vascular cell precursors remains poorly defined. Our objective was to specifically delete endoglin in neural crest- and somite-derived Pax3-positive vascular precursors to understand the impact on somite progenitor cell contribution to embryonic vascular development. Pax3Cre mice were crossed with Eng+/- mice to obtain compound mutant Pax3(Cre/+);Eng+/- mice. These mice were then crossed with homozygous endoglin LoxP-mutated (Eng(LoxP/LoxP)) mice to conditionally delete the endoglin gene in specific lineages that contribute to endothelial and smooth muscle constituents of developing embryonic vessels. Pax3(Cre/+);Eng(LoxP/-) mice showed a variety of vascular defects at E10.5, and none of these mice survived past E12.5. Embryos analyzed at E10.5 showed malformations suggestive of misdirection of the intersomitic vessels. The dorsal aorta showed significant dilation with associated vascular smooth muscle cells exhibiting disorganization and enhanced expression of smooth muscle differentiation proteins, including smooth muscle actin. These results demonstrate a requirement for endoglin in descendants of Pax3-expressing vascular cell precursors, and thus provides new insight into the cellular basis underlying adult vascular diseases such as HHT.
    Developmental Biology 10/2015; DOI:10.1016/j.ydbio.2015.10.019 · 3.55 Impact Factor
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    ABSTRACT: Objective: Bone morphogenetic protein-9 (BMP9)/activin-like kinase-1 and delta-like 4 (DLL4)/Notch promote endothelial quiescence, and we aim to understand mechanistic interactions between the 2 pathways. We identify new targets that contribute to endothelial quiescence and test whether loss of Dll4(+/-) in adult vasculature alters BMP signaling. Approach and results: Human endothelial cells respond synergistically to BMP9 and DLL4 stimulation, showing complete quiescence and induction of HEY1 and HEY2. Canonical BMP9 signaling via activin-like kinase-1-Smad1/5/9 was disrupted by inhibition of Notch signaling, even in the absence of exogenous DLL4. Similarly, DLL4 activity was suppressed when the basal activin-like kinase-1-Smad1/5/9 pathway was inhibited, showing that these pathways are interdependent. BMP9/DLL4 required induction of P27(KIP1) for quiescence, although multiple factors are involved. To understand these mechanisms, we used proteomics data to identify upregulation of thrombospondin-1, which contributes to the quiescence phenotype. To test whether Dll4 regulates BMP/Smad pathways and endothelial cell phenotype in vivo, we characterized the vasculature of Dll4(+/-) mice, analyzing endothelial cells in the lung, heart, and aorta. Together with changes in endothelial structure and vascular morphogenesis, we found that loss of Dll4 was associated with a significant upregulation of pSmad1/5/9 signaling in lung endothelial cells. Because steady-state endothelial cell proliferation rates were not different in the Dll4(+/-) mice, we propose that the upregulation of pSmad1/5/9 signaling compensates to maintain endothelial cell quiescence in these mice. Conclusions: DLL4/Notch and BMP9/activin-like kinase-1 signaling rely on each other's pathways for full activity. This represents an important mechanism of cross talk that enhances endothelial quiescence and sensitively coordinates cellular responsiveness to soluble and cell-tethered ligands.
    Arteriosclerosis Thrombosis and Vascular Biology 10/2015; DOI:10.1161/ATVBAHA.115.306541 · 6.00 Impact Factor
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    ABSTRACT: This study investigated the effects of loss of Cthrc1 on adipogenesis, body composition, metabolism, physical activity, and muscle physiology. Complete metabolic and activity monitoring as well as grip strength measurements and muscle myography was performed in Cthrc1 null and wildtype mice. Compared to wildtypes, Cthrc1 null mice had similar body weights but significantly reduced energy expenditure, decreased lean mass, and increased fat mass, especially visceral fat. In vitro studies demonstrated that Cthrc1 inhibited adipocyte differentiation as well as PPAR and CREB reporter activity, while preadipocytes isolated from Cthrc1 null mice exhibited enhanced adipogenic differentiation. Voluntary physical activity in Cthrc1 null mice as assessed by wheel running was reduced to approximately half the distance covered by wildtypes. Reduced grip strength was observed in Cthrc1 null mice at the age of 15 weeks or older with reduced performance and mass of hyphenate muscle. In the brain, Cthrc1 expression was most prominent in neurons of thalamic and hypothalamic nuclei with evidence for secretion into the circulation in the median eminence. Our data indicate that Cthrc1 regulates body composition through inhibition of adipogenesis. In addition, central Cthrc1 may be a mediator of muscle function and physical activity. © 2015 The Obesity Society.
    Obesity 07/2015; 23(8). DOI:10.1002/oby.21144 · 3.73 Impact Factor
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    ABSTRACT: Despite their discovery as angiogenic factors and mitogens for endothelial cells more than 30 years ago, much remains to be determined about the role of fibroblast growth factors (FGFs) and their receptors in vascular development, homeostasis, and disease. In vitro studies show that members of the FGF family stimulate growth, migration, and sprouting of endothelial cells, and growth, migration, and phenotypic plasticity of vascular smooth muscle cells. Recent studies have revealed important roles for FGFs and their receptors in the regulation of endothelial cell sprouting and vascular homeostasis in vivo. Furthermore, recent work has revealed roles for FGFs in atherosclerosis, vascular calcification, and vascular dysfunction. The large number of FGFs and their receptors expressed in endothelial and vascular smooth muscle cells complicates these studies. In this review, we summarize recent studies in which new and unanticipated roles for FGFs and their receptors in the vasculature have been revealed.
    Current Atherosclerosis Reports 06/2015; 17(6):509. DOI:10.1007/s11883-015-0509-6 · 3.42 Impact Factor
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    ABSTRACT: Endoglin is a type III TGFβ auxiliary receptor that is upregulated in endothelial cells during angiogenesis and, when mutated in humans, results in the vascular disease hereditary hemorrhagic telangiectasia (HHT). Though endoglin has been implicated in cell adhesion, the underlying molecular mechanisms are still poorly understood. Here we show endoglin expression in endothelial cells regulates subcellular localization of zyxin in focal adhesions in response to BMP9. RNA knockdown of endoglin resulted in mislocalization of zyxin and altered formation of focal adhesions. The mechanotransduction role of focal adhesions and their ability to transmit regulatory signals through binding of the extracellular matrix are altered by endoglin deficiency. BMP/TGFβ transcription factors, SMADs, and zyxin have recently been implicated in a newly emerging signaling cascade, the Hippo pathway. The Hippo transcription coactivator, YAP1 (yes-associated protein 1), has been suggested to play a crucial role in mechanotransduction and cell-cell contact. Identification of BMP9-dependent nuclear localization of YAP1 in response to endoglin expression suggests a mechanism of crosstalk between the two pathways. Suppression of endoglin and YAP1 alters BMP9-dependent expression of YAP1 target genes CCN1 (cysteine-rich 61, CYR61) and CCN2 (connective tissue growth factor, CTGF) as well as the chemokine CCL2 (monocyte chemotactic protein 1, MCP-1). These results suggest a coordinate effect of endoglin deficiency on cell matrix remodeling and local inflammatory responses. Identification of a direct link between the Hippo pathway and endoglin may reveal novel mechanisms in the etiology of HHT.
    PLoS ONE 04/2015; 10(4):e0122892. DOI:10.1371/journal.pone.0122892 · 3.23 Impact Factor
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    ABSTRACT: Multiple myeloma is a B-cell malignancy characterized by the unrelenting proliferation of plasma cells. Multiple myeloma causes osteolytic lesions and fractures that do not heal due to decreased osteoblastic and increased osteoclastic activity. However, the exact relationship between osteoblasts and myeloma cells remains elusive. Understanding the interactions between these dynamic bone-forming cells and myeloma cells is crucial to understanding how osteolytic lesions form and persist, and how tumors grow within the bone marrow. This review provides a comprehensive overview of basic and translational research focused on the role of osteoblasts in multiple myeloma progression and their relationship to osteolytic lesions. Importantly, current challenges for in vitro studies exploring direct osteoblastic effects on myeloma cells, and gaps in understanding the role of the osteoblast in myeloma progression are delineated. Finally, successes and challenges in myeloma treatment with osteoanabolic therapy (i.e. any treatment that induces increased osteoblastic number or activity) are enumerated. Our goal is to illuminate novel mechanisms by which osteoblasts may contribute to multiple myeloma disease progression and osteolysis to better direct research efforts. Ultimately, we hope this may provide a roadmap for new approaches to the pathogenesis and treatment of multiple myeloma with a particular focus on the osteoblast. Copyright © 2015. Published by Elsevier Inc.
    Bone 02/2015; 75. DOI:10.1016/j.bone.2015.02.021 · 3.97 Impact Factor
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    ABSTRACT: BACKGROUNDPTEN/AKT signaling plays a key role in prostate cancer development and maintenance of prostate cancer stem cells. How other oncogenes or tumor suppressors interact with this pathway remain to be elucidated. SLUG is an zinc finger transcription factor of the Snail superfamily, and it promotes cancer metastasis and determines the mammary stem cell state.METHODSSLUG was overexpressed in cells by retroviral vector and knockdown of SLUG and PTEN was mediated by shRNAs-expressing lentiviruses. Expression level of SLUG and PTEN was examined by Western blot, RT-PCR, and qPCR analyses. PTEN promoter activity was measured by luciferase reporter assay. ChIP assay was used to measure the binding between SLUG and the PTEN promoter in vivo.RESULTWe showed that overexpression of SLUG decreased expression of PTEN tumor repressor in prostate cancer cell lines 22RV1 and DU145; conversely, knockdown of SLUG expression elevated PTEN expresson at both protein and RNA level in these cells. We demonstrated that SLUG overexpression inhibits PTEN promoter activity through the proximal promoter region in prostate cancer cells. By ChIP assay, we confirmed that SLUG directly binds to the PTEN promoter region covering the E-box sites. We also showed that Slug deficiency leads to an increased expression of PTEN in mouse embryo fibroblasts and prostate tissues. Importantly, we found that overexpression of SLUG increases drug resistance of DU145 prostate cancer cell line and knockdown of SLUG by shRNA sensitizes DU145 cell line to chemotherapeutic drugs. We further demonstrated that PTEN knockdown converts drug sensitivity of DU145 cells expressing SLUG shRNA to anticancer drugs.CONCLUSION We provide compelling evidence showing that PTEN is a direct functional target of SLUG. Our findings offer new insight in the regulation of the PTEN/AKT pathway and provide a molecular basis for potential targeted therapies of prostate cancer Prostate 9999: 1–10, 2015. © 2015 Wiley Periodicals, Inc.
    The Prostate 02/2015; 75(9). DOI:10.1002/pros.22974 · 3.57 Impact Factor
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    ABSTRACT: Notch signaling plays many important roles in homeostasis and remodeling in the vessel wall, and serves a critical role in the communication between endothelial cells and smooth muscle cells. Within blood vessels, Notch signaling integrates with multiple pathways by mechanisms including direct protein–protein interaction, cooperative or synergistic regulation of signal cascades, and co-regulation of transcriptional targets. After establishment of the mature blood vessel, the spectrum and intensity of Notch signaling change during phases of active remodeling or disease progression. These changes can be mediated by regulation via microRNAs and protein stability or signaling, and corresponding changes in complementary signaling pathways. Notch also affects endothelial cells on a system level by regulating key metabolic components. This review will outline the most recent findings of Notch activity in blood vessels, with a focus on how Notch signals integrate with other molecular signaling pathways controlling vascular phenotype.
    Vascular Pharmacology 10/2014; 63(2). DOI:10.1016/j.vph.2014.10.003 · 3.64 Impact Factor
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    ABSTRACT: A more complete understanding of the mechanisms that regulate the angiogenic switch, which contributes to the conversion of small dormant tumors to actively growing malignancies, is important for the development of more effective anti-angiogenic strategies for cancer therapy. While significant progress has been made in understanding the complex mechanisms by which integrin αvβ3 expressed in endothelial cells governs angiogenesis, less is known concerning the ability of αvβ3 expressed within the tumor cell compartment to modulate the angiogenic output of a tumor. Here we provide evidence that αvβ3 expressed in melanoma cells may contribute to the suppression of IGFBP-4, an important negative regulator of IGF-1 signaling. Given the multiple context-dependent roles for αvβ3 in angiogenesis and tumor progression, our novel findings provide additional molecular insight into how αvβ3 may govern the angiogenic switch by a mechanism associated with a p38 MAPK and matrix metalloproteinases-dependent regulation of the endogenous angiogenesis inhibitor IGFBP-4.
    Angiogenesis 09/2014; 18(1). DOI:10.1007/s10456-014-9445-2 · 4.88 Impact Factor
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    ABSTRACT: The human genome encodes for over 1800 microRNAs (miRNAs), which are short non-coding RNA molecules that function to regulate gene expression post-transcriptionally. Due to the potential for one miRNA to target multiple gene transcripts, miRNAs are recognized as a major mechanism to regulate gene expression and mRNA translation. Computational prediction of miRNA targets is a critical initial step in identifying miRNA:mRNA target interactions for experimental validation. The available tools for miRNA target prediction encompass a range of different computational approaches, from the modeling of physical interactions to the incorporation of machine learning. This review provides an overview of the major computational approaches to miRNA target prediction. Our discussion highlights three tools for their ease of use, reliance on relatively updated versions of miRBase, and range of capabilities, and these are DIANA-microT-CDS, miRanda-mirSVR, and TargetScan. In comparison across all miRNA target prediction tools, four main aspects of the miRNA:mRNA target interaction emerge as common features on which most target prediction is based: seed match, conservation, free energy, and site accessibility. This review explains these features and identifies how they are incorporated into currently available target prediction tools. MiRNA target prediction is a dynamic field with increasing attention on development of new analysis tools. This review attempts to provide a comprehensive assessment of these tools in a manner that is accessible across disciplines. Understanding the basis of these prediction methodologies will aid in user selection of the appropriate tools and interpretation of the tool output.
    Frontiers in Genetics 02/2014; 5:23. DOI:10.3389/fgene.2014.00023
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    ABSTRACT: The quantitative analysis of blood vessel volumes from magnetic resonance angiograms (MRA) or μCT images is difficult and time-consuming. This fact, when combined with a study that involves multiple scans of multiple subjects, can represent a significant portion of research time. In order to enhance analysis options and to provide an automated and fast analysis method, we developed a software plugin for the ImageJ and Fiji image processing frameworks that enables the quick and reproducible volume quantification of blood vessel segments. The novel plugin named Volume Calculator (VolCal), accepts any binary (thresholded) image and produces a three-dimensional schematic representation of the vasculature that can be directly manipulated by the investigator. Using MRAs of the mouse hindlimb ischemia model, we demonstrate quick and reproducible blood vessel volume calculations with 95 – 98% accuracy. In clinical settings this software may enhance image interpretation and the speed of data analysis and thus enhance intervention decisions for example in peripheral vascular disease or aneurysms. In summary, we provide a novel, fast and interactive quantification of blood vessel volumes for single blood vessels or sets of vessel segments with particular focus on collateral formation after an ischemic insult.
    The Open Medical Imaging Journal 10/2013; 7(1):19-27. DOI:10.2174/1874347101307010019
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    ABSTRACT: Rationale: Deregulated vascular smooth muscle cell (VSMC) proliferation contributes to multiple vascular pathologies, and Notch signaling regulates VSMC phenotype. Objective: Previous work focused on Notch1 and Notch3 in VSMC during vascular disease; however, the role of Notch2 is unknown. Because injured murine carotid arteries display increased Notch2 in VSMC as compared with uninjured arteries, we sought to understand the impact of Notch2 signaling in VSMCs. Methods and results: In human primary VSMCs, Jagged-1 (Jag-1) significantly reduced proliferation through specific activation of Notch2. Increased levels of p27(kip1) were observed downstream of Jag-1/Notch2 signaling and were required for cell cycle exit. Jag-1 activation of Notch resulted in increased phosphorylation on serine 10, decreased ubiquitination, and prolonged half-life of p27(kip1). Jag-1/Notch2 signaling robustly decreased S-phase kinase-associated protein, an F-box protein that degrades p27(kip1) during G1. Overexpression of S-phase kinase-associated protein before Notch activation by Jag-1 suppressed the induction of p27(kip1). Additionally, increased Notch2 and p27(kip1) expression was colocalized to the nonproliferative zone of injured arteries as indicated by co-staining with proliferating cell nuclear antigen, whereas Notch3 was expressed throughout normal and injured arteries, suggesting Notch2 may negatively regulate lesion formation. Conclusions: We propose a receptor-specific function for Notch2 in regulating Jag-1-induced p27(kip1) expression and growth arrest in VSMCs. During vascular remodeling, colocalization of Notch2 and p27(kip1) to the nonproliferating region supports a model where Notch2 activation may negatively regulate VSMC proliferation to lessen the severity of the lesion. Thus, Notch2 is a potential target for control of VSMC hyperplasia.
    Circulation Research 08/2013; 113(8). DOI:10.1161/CIRCRESAHA.113.301272 · 11.02 Impact Factor
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    ABSTRACT: Background Changes in the vascular smooth muscle cell (VSMC) contractile phenotype occur in pathological states such as restenosis and atherosclerosis. Multiple cytokines, signaling through receptor tyrosine kinases (RTK) and PI3K/Akt and MAPK/ERK pathways, regulate these phenotypic transitions. The Spry proteins are feedback modulators of RTK signaling, but their specific roles in VSMC have not been established. Methodology/Principal Findings Here, we report for the first time that Spry1, but not Spry4, is required for maintaining the differentiated state of human VSMC in vitro. While Spry1 is a known MAPK/ERK inhibitor in many cell types, we found that Spry1 has little effect on MAPK/ERK signaling but increases and maintains Akt activation in VSMC. Sustained Akt signaling is required for VSMC marker expression in vitro, while ERK signaling negatively modulates Akt activation and VSMC marker gene expression. Spry4, which antagonizes both MAPK/ERK and Akt signaling, suppresses VSMC differentiation marker gene expression. We show using siRNA knockdown and ChIP assays that FoxO3a, a downstream target of PI3K/Akt signaling, represses myocardin promoter activity, and that Spry1 increases, while Spry4 decreases myocardin mRNA levels. Conclusions Together, these data indicate that Spry1 and Spry4 have opposing roles in VSMC phenotypic modulation, and Spry1 maintains the VSMC differentiation phenotype in vitro in part through an Akt/FoxO/myocardin pathway.
    PLoS ONE 03/2013; 8(3):e58746. DOI:10.1371/journal.pone.0058746 · 3.23 Impact Factor
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    ABSTRACT: We discovered the gene Collagen Triple Helix Repeat Containing 1 (Cthrc1) and reported its developmental expression and induction in adventitial cells of injured arteries and dermal cells of skin wounds. The role of Cthrc1 in normal adult tissues has not yet been determined. We generated mutant mice with a novel Cthrc1 null allele by homologues recombination. Cthrc1 null mice appeared developmentally normal. On the C57BL/6J background, livers from Cthrc1 null mice accumulated vast quantities of lipid, leading to extensive macrovesicular steatosis. Glycogen levels in skeletal muscle and liver of Cthrc1 null mice on the 129S6/SvEv background were significantly increased. However, Cthrc1 expression is not detectable in these tissues in wild-type mice, suggesting that the lipid and glycogen storage phenotype may be a secondary effect due to loss of Cthrc1 production at a distant site. To investigate potential hormonal functions of Cthrc1, tissues from adult mice and pigs were examined for Cthrc1 expression by immunohistochemistry with monoclonal anti-Cthrc1 antibodies. In pigs, Cthrc1 was detected around chromophobe cells of the anterior pituitary, and storage of Cthrc1 was observed in colloid-filled follicles and the pituitary cleft. Pituitary follicles have been observed in numerous vertebrates including humans but none of the known pituitary hormones have hitherto been detected in them. In C57BL/6J mice, however, Cthrc1 was predominantly expressed in the paraventricular and supraoptic nucleus of the hypothalamus but not in the posterior pituitary. In human plasma, we detected Cthrc1 in pg/ml quantities and studies with (125)I-labeled Cthrc1 revealed a half-life of 2.5 hours in circulation. The highest level of Cthrc1 binding was observed in the liver. Cthrc1 has characteristics of a circulating hormone generated from the anterior pituitary, hypothalamus and bone. Hormonal functions of Cthrc1 include regulation of lipid storage and cellular glycogen levels with potentially broad implications for cell metabolism and physiology.
    PLoS ONE 10/2012; 7(10):e47142. DOI:10.1371/journal.pone.0047142 · 3.23 Impact Factor
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    ABSTRACT: BMP9 signaling has been implicated in hereditary hemorrhagic telangiectasia (HHT) and vascular remodeling, acting via the HHT target genes, endoglin and ALK1. This study sought to identify endothelial BMP9-regulated proteins that could affect the HHT phenotype. Gene ontology analysis of cDNA microarray data obtained following BMP9 treatment of primary human endothelial cells indicated regulation of chemokine, adhesion, and inflammation pathways. These responses included the upregulation of the chemokine, CXCL12/SDF1 and downregulation of its receptor, CXCR4. Quantitative mass spectrometry identified additional secreted proteins, including the chemokine CXCL10/IP10. RNA knockdown of endoglin and ALK1 impaired SDF1/CXCR4 regulation by BMP9. Because of the association of SDF1 with ischemia, we analyzed its expression under hypoxia in response to BMP9 in vitro, and during the response to hindlimb ischemia, in endoglin-deficient mice. BMP9 and hypoxia were additive inducers of SDF1 expression. Moreover, data suggest that endoglin deficiency impaired SDF1 expression in endothelial cells in vivo. Our data implicate BMP9 in regulation of the SDF1/CXCR4 chemokine axis in endothelial cells and point to a role for BMP9 signaling via endoglin in a switch from an SDF1-responsive autocrine phenotype to an SDF1 non-responsive paracrine state that represses endothelial cell migration and may promote vessel maturation.
    Blood 09/2012; 120(20). DOI:10.1182/blood-2012-07-440784 · 10.45 Impact Factor
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    ABSTRACT: Negative-pressure wound therapy (NPWT) has been used for to treat wounds for more than 15 years and, more recently, has been used to secure split-thickness skin grafts. There are some data to support this use of NPWT, but the actual mechanism by which NPWT speeds healing or improves skin graft take is not entirely known. The purpose of this project was to assess whether NPWT improved angiogenesis, wound healing, or graft survival when compared with traditional bolster dressings securing split-thickness skin grafts in a porcine model. We performed two split-thickness skin grafts on each of eight 30 kg Yorkshire pigs. We took graft biopsies on postoperative days 2, 4, 6, 8, and 10 and submitted the samples for immunohistochemical staining, as well as standard hematoxylin and eosin staining. We measured the degree of vascular ingrowth via immunohistochemical staining for von Willenbrand's factor to better identify blood vessel epithelium. We determined the mean cross-sectional area of blood vessels present for each representative specimen, and then compared the bolster and NPWT samples. We also assessed each graft for incorporation and survival at postoperative day 10. Our analysis of the data revealed that there was no statistically significant difference in the degree of vascular ingrowth as measured by mean cross-sectional capillary area (p = 0.23). We did not note any difference in graft survival or apparent incorporation on a macroscopic level, although standard hematoxylin and eosin staining indicated that microscopically, there seemed to be better subjective graft incorporation in the NPWT samples and a nonsignificant trend toward improved graft survival in the NPWT group. We were unable to demonstrate a significant difference in vessel ingrowth when comparing NPWT and traditional bolster methods for split-thickness skin graft fixation. More studies are needed to elucidate the manner by which NPWT exerts its effects and the true clinical magnitude of these effects.
    08/2012; 73(2):447-51. DOI:10.1097/TA.0b013e31825aa9ea
  • Yuefeng Tang · Hao Bai · Sumithra Urs · Zack Wang · Lucy Liaw ·
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    ABSTRACT: Hematopoietic stem cells (HSC) are found in several independent sites embryonically. Loss-of-function studies indicated that Notch1, but not Notch2 signaling was required for HSC emergence from the aortic-gonado-mesonephros (AGM) region. We previously showed that constitutive Notch1 activation impaired primitive erythroid differentiation, but its effects on HSC emergence from the AGM region were not studied. To further define specific roles of Notch receptors, we characterized HSC in mouse embryos expressing either Notch1 intracellular domain (ICD) or Notch4ICD in VE-cadherin or SM22α expressing populations. Although embryonic Notch1 activation in VE-cadherin populations led to lethality after E13.5, earlier defects in the fetal liver were observed. Embryos were analyzed at E12.5 to assess hematopoiesis and the phenotype of developing cells in the AGM region. We found that activation of Notch1 in the endothelial compartment in VE-cadherin expressing cells resulted in the absence of intra-aortic clusters and defects in fetal liver hematopoiesis. In contrast, although Notch4 expression is regulated during fetal hematopoiesis, activation of Notch4 in VE-cadherin expressing populations did not affect HSC phenotype, although later vascular remodeling was impaired. Likewise, activation of Notch1 in SM22α positive populations had no significant effect on hematopoiesis. Our results indicate a cell type-dependent activity and distinct features of Notch1 versus Notch4 signaling and their impact on HSC generation.
    Transgenic Research 08/2012; 22(2). DOI:10.1007/s11248-012-9637-8 · 2.32 Impact Factor
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    Yuefeng Tang · Joshua M Boucher · Lucy Liaw ·
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    ABSTRACT: Histone deacetylases (HDACs) modify smooth muscle cell (SMC) proliferation and affect neointimal lesion formation by regulating cell cycle progression. HDACs might also regulate SMC differentiation, although this is not as well characterized. Notch signaling activates SMC contractile markers and the differentiated phenotype in human aortic SMCs. Using this model, we found that HDAC inhibition antagonized the ability of Notch to increase levels of smooth muscle α-actin, calponin1, smooth muscle 22α, and smooth muscle myosin heavy chain. However, inhibition of HDAC activity did not suppress Notch activation of the HRT target genes. In fact, HDAC inhibition increased activation of the canonical C-promoter binding factor-1 (CBF-1)-mediated Notch pathway, which activates HRT transcription. Although CBF-1-mediated Notch signaling was increased by HDAC inhibition in human SMCs and in a C3H10T1/2 model, SMC differentiation was inhibited in both cases. Further characterization of downstream Notch signaling pathways showed activation of the c-Jun N-terminal kinase, p38 mitogen-activated protein kinase, and PI3K/Akt pathways. The activation of these pathways was sensitive to HDAC inhibition and was positively correlated with the differentiated phenotype. Our studies define novel signaling pathways downstream of Notch signaling in human SMCs. In addition to the canonical CBF-1 pathway, Notch stimulates c-Jun N-terminal kinase, mitogen-activated protein kinase, and PI3K cascades. Both canonical and noncanonical pathways downstream of Notch promote a differentiated, contractile phenotype in SMCs. Although CBF-1-mediated Notch signaling is not suppressed by HDAC inhibition, HDAC activity is required for Notch differentiation signals through mitogen-activated protein kinase and PI3K pathways in SMCs. (J Am Heart Assoc. 2012;1:e000901 doi: 10.1161/JAHA.112.000901).
    Journal of the American Heart Association 06/2012; 1(3):e000901. DOI:10.1161/JAHA.112.000901 · 4.31 Impact Factor
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    Joshua Boucher · Thomas Gridley · Lucy Liaw ·
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    ABSTRACT: Notch signaling in the cardiovascular system is important during embryonic development, vascular repair of injury, and vascular pathology in humans. The vascular smooth muscle cell (VSMC) expresses multiple Notch receptors throughout its life cycle, and responds to Notch ligands as a regulatory mechanism of differentiation, recruitment to growing vessels, and maturation. The goal of this review is to provide an overview of the current understanding of the molecular basis for Notch regulation of VSMC phenotype. Further, we will explore Notch interaction with other signaling pathways important in VSMC.
    Frontiers in Physiology 04/2012; 3:81. DOI:10.3389/fphys.2012.00081 · 3.53 Impact Factor
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    ABSTRACT: Adipose tissue development is dependent on multiple signaling mechanisms and cell-cell interactions that regulate adipogenesis, angiogenesis and extracellular remodeling. The Notch signaling pathway is an important cell-fate determinant whose role in adipogenesis is not clearly defined. To address this issue, we examined the effect of inhibition of Notch signaling by soluble-Jagged1 in the 3T3-L1 preadipocyte line. In vitro, soluble-Jagged1 expression in 3T3-L1 cells altered cell morphology, increased the rate of cell proliferation and induced an early transcriptional response to differentiation stimuli. However, these cells did not form mature adipocytes due to their inability to exit the cell-cycle in response to serum-starvation and glucocorticoid-induced cell-cycle arrest. In contrast, subcutaneous allografts of soluble-Jagged1 cells formed larger fat pads containing lipid-filled adipocytes with improved neovascularization compared with controls. Since adipogenesis is tightly associated with angiogenesis, we evaluated the influence of soluble-Jagged1 on endothelial cells by culturing them in cell-free conditioned media from preadipocytes. Soluble Jagged1-mediated inhibition of Notch signaling increased levels of secreted cytokines, potentially contributing to the improved cell growth and proliferation observed in these cultures. Our findings demonstrate an initial requirement of Notch signaling inactivation for preadipocyte cell commitment and support the hypothesis that cell-to-cell crosstalk between the preadipocytes and endothelial cells is required for neovascularization and remodeling of the tissue to promote hyperplasia and hypertrophy of differentiating adipocytes.
    01/2012; 1(1):46-57. DOI:10.4161/adip.19186

Publication Stats

6k Citations
548.22 Total Impact Points


  • 2015
    • Tufts University
      Бостон, Georgia, United States
  • 2003-2015
    • University of Maine
      Orono, Minnesota, United States
    • Maine Medical Center
      Portland, Maine, United States
  • 1999-2015
    • Maine Medical Center Research Institute
      Скарбороу, Maine, United States
  • 2008
    • University of New Hampshire
      Durham, New Hampshire, United States
    • University of Southern Maine
      • Department of Applied Medical Sciences
      Gorham, Maine, United States
    • University of Massachusetts Boston
      Boston, Massachusetts, United States
  • 1994-2006
    • University of Washington Seattle
      • • Division of Nephrology
      • • Department of Pathology
      Seattle, Washington, United States
  • 2001
    • Hokkaido University
      • Institute for Genetic Medicine
      Sapporo, Hokkaidō, Japan
  • 1996-1999
    • Howard Hughes Medical Institute
      Ашбърн, Virginia, United States
  • 1995-1998
    • Vanderbilt University
      • Department of Cancer Biology
      Нашвилл, Michigan, United States