Browsing by Subject "Vascular Remodeling"

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    Drebrin regulates angiotensin II-induced aortic remodelling.
    (Cardiovascular research, 2018-11) Zhang, Lisheng; Wu, Jiao-Hui; Huang, Tai-Qin; Nepliouev, Igor; Brian, Leigh; Zhang, Zhushan; Wertman, Virginia; Rudemiller, Nathan P; McMahon, Timothy J; Shenoy, Sudha K; Miller, Francis J; Crowley, Steven D; Freedman, Neil J; Stiber, Jonathan A

    Aims

    The actin-binding protein Drebrin is up-regulated in response to arterial injury and reduces smooth muscle cell (SMC) migration and proliferation through its interaction with the actin cytoskeleton. We, therefore, tested the hypothesis that SMC Drebrin inhibits angiotensin II-induced remodelling of the proximal aorta.

    Methods and results

    Angiotensin II was administered via osmotic minipumps at 1000 ng/kg/min continuously for 28 days in SM22-Cre+/Dbnflox/flox (SMC-Dbn-/-) and control mice. Blood pressure responses to angiotensin II were assessed by telemetry. After angiotensin II infusion, we assessed remodelling in the proximal ascending aorta by echocardiography and planimetry of histological cross sections. Although the degree of hypertension was equivalent in SMC-Dbn-/- and control mice, SMC-Dbn-/- mice nonetheless exhibited 60% more proximal aortic medial thickening and two-fold more outward aortic remodelling than control mice in response to angiotensin II. Proximal aortas demonstrated greater cellular proliferation and matrix deposition in SMC-Dbn-/- mice than in control mice, as evidenced by a higher prevalence of proliferating cell nuclear antigen-positive nuclei and higher levels of collagen I. Compared with control mouse aortas, SMC-Dbn-/- aortas demonstrated greater angiotensin II-induced NADPH oxidase activation and inflammation, evidenced by higher levels of Ser-536-phosphorylated NFκB p65 subunits and higher levels of vascular cell adhesion molecule-1, matrix metalloproteinase-9, and adventitial macrophages.

    Conclusions

    We conclude that SMC Drebrin deficiency augments angiotensin II-induced inflammation and adverse aortic remodelling.
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    The Actin-Binding Protein Drebrin Inhibits Neointimal Hyperplasia.
    (Arteriosclerosis, thrombosis, and vascular biology, 2016-05) Stiber, Jonathan A; Wu, Jiao-Hui; Zhang, Lisheng; Nepliouev, Igor; Zhang, Zhu-Shan; Bryson, Victoria G; Brian, Leigh; Bentley, Rex C; Gordon-Weeks, Phillip R; Rosenberg, Paul B; Freedman, Neil J

    Objective

    Vascular smooth muscle cell (SMC) migration is regulated by cytoskeletal remodeling as well as by certain transient receptor potential (TRP) channels, nonselective cation channels that modulate calcium influx. Proper function of multiple subfamily C TRP (TRPC) channels requires the scaffolding protein Homer 1, which associates with the actin-binding protein Drebrin. We found that SMC Drebrin expression is upregulated in atherosclerosis and in response to injury and investigated whether Drebrin inhibits SMC activation, either through regulation of TRP channel function via Homer or through a direct effect on the actin cytoskeleton.

    Approach and results

    Wild-type (WT) and congenic Dbn(-/+) mice were subjected to wire-mediated carotid endothelial denudation. Subsequent neointimal hyperplasia was 2.4±0.3-fold greater in Dbn(-/+) than in WT mice. Levels of globular actin were equivalent in Dbn(-/+) and WT SMCs, but there was a 2.4±0.5-fold decrease in filamentous actin in Dbn(-/+) SMCs compared with WT. Filamentous actin was restored to WT levels in Dbn(-/+) SMCs by adenoviral-mediated rescue expression of Drebrin. Compared with WT SMCs, Dbn(-/+) SMCs exhibited increased TRP channel activity in response to platelet-derived growth factor, increased migration assessed in Boyden chambers, and increased proliferation. Enhanced TRP channel activity and migration in Dbn(-/+) SMCs were normalized to WT levels by rescue expression of not only WT Drebrin but also a mutant Drebrin isoform that binds actin but fails to bind Homer.

    Conclusions

    Drebrin reduces SMC activation through its interaction with the actin cytoskeleton but independently of its interaction with Homer scaffolds.
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    Vascular Influence During Patterning and Differentiation of the Gonad
    (2011) Cool, Jonah

    The gonad is a unique primordial organ that retains the ability to adopt one of two morphological fates through much of mammalian embryonic development. Previous work in our lab found that dimorphic vascular remodeling was one of the earliest steps during sex-specific morphogenesis. In particular, vessels in XY gonads display highly ordered behavior that coincides with testis cord formation. It was unknown how the vasculature may influence testis cord morphogenesis and, if so, how this was mechanistically related to sex determination. The work in this thesis addresses a single over-arching hypothesis: Male-specific vascular remodeling is required for testis morphogenesis and orchestrates differentiation of the XY gonad.

    To address this question we have modified and developed techniques that allow us to isolate aspects of vascular behavior, gene expression, and endothelial influence on surrounding cells. In particular, the application of live imaging was instrumental to understanding the behavior of various gonadal cell-types in relation to remodeling vessels. It is difficult to grasp the complexity of an organ without understanding the dynamics of its constituents. A critical aim of my work was to identify specific inhibitors of the vasculature that do not affect the early stages of sex determination. Combining inhibitors, live imaging, cell sorting, qRT-PCR, mouse models, and whole organ culture has led to a far richer understanding of how the vasculature behaves and the cell-types that mediate its influence on organ morphogenesis. The beauty of our system is that we do not have to settle for a snapshot of the fate of cells in vivo, but can document their journeys and their acquaintances along the way.

    Vascular migration is required for testis cord morphogenesis. Specific inhibitors revealed that in the absence of vessels, testis cords do not form. The work below shows that vessels establish a feedback loop with mesenchymal cells that results in both endothelial migration and subsequent mesenchymal proliferation. Interstitial control of testis morphogenesis is a new model within the field. The mechanisms regulating this process include Vegf mediated vascular remodeling, Pdgf induced proliferation, and Wnt repression of coordinated endothelial-mesenchymal dynamics. Our work also suggests that vascular patterning underlies testis patterning and, again, is mediated by signals within the interstitial space not within testis cords themselves.

    A final aspect of my work has been focused on how vessels continue to influence morphology of the testis and the fate of surrounding cells. Jennifer Brennan, a graduate student in our lab, previously showed that loss of Pdgfrα antagonizes cord formation and development of male-specific lineages. The mechanisms and cell-types related to this defect were not clear. I began to reanalyze Pdgfrα mutants after finding remarkable similarity to gonads after vascular inhibition. This work is providing data suggesting that vessels are not simply responsible for testis morphology but also for the fate of specialized cells within the testis. On the whole, this thesis describes specific roles for endothelial cells during gonad development and mechanisms by which they are regulated.