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Institute of Physiology and Pathophysiology

Hecker Group

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Group Members

Vascular blood flow and pressure act on endothelial as well as on smooth muscle cells. Not surprisingly, these mechanical forces are a major factor in the regulation of vascular perfusion as well as, in the long run, vascular cell phenotype and vessel structure.

Our group tries to further our understanding of how fluid shear stress and wall tension act on vascular cells, and what consequences can be expected under supra-physiological conditions, e.g. in hypertension. To this end we focus on two projects: a) the role of zyxin, a protein shuttling between the cytoskeleton and the nucleus, in pressure-induced vascular remodelling, and b) the expression of variants of the human endothelial nitric oxide synthase gene nos3 in response to fluid shear stress.

Background: Mechanical Forces in the Vascular System

In the blood vessel mechanical stimuli, mainly generated through fluid shear stress acting on endothelial cells, and Laplace wall tension affecting both endothelial and smooth muscle cells, play a major role in the regulation of blood flow and long term homeostasis of the vascular system (Figure 1).

Figure 1: Principal forces modulating vessel tone and vascular homeostasis. While fluid shear stress (τ) is defined by blood viscosity (η), laminar flow (Q), and the reciprocal of the vessel radius (r), Laplace wall tension (σ) depends on transmural pressure (ptm), radius (r), and the inverse of the vessel wall thickness (d).

As both forces inversely depend on the vessel diameter,  they play a functionally antagonistic role in regulating vessel tone and, thus, blood flow. This is well understood down to its molecular mechanisms, which rely on, e.g. nitric oxide (NO) and the vasoconstrictor peptide endothelin-1. However, although long-term effects of altered laminar shear stress and wall tension on vessel wall structure, as it occurs in, e.g. pressure-induced arterial hypertrophy/hyperplasia in hypertensive patients, are well documented, the signalling pathways underlying these processes are not characterised yet. Our group concentrates on two projects analysing the effects of wall tension and fluid shear stress on gene expression and phenotype regulation in endothelial and vascular smooth muscle cells.

Zyxin as a Mechanotransducer in Vascular Cells

In this project we analyse the mechanism of how supra-physiological levels of wall tension lead to phenotype changes in vascular cells in vitro and in situ. Although common signal transduction pathways play a role in the vascular response to increases in wall tension, a major event in this process is the wall tension/pressure-induced translocation of the cytoskeletal protein zyxin followed by zyxin-mediated changes in gene expression. This is the first description of a protein specific for mechanotransduction in vascular cells. Currently we analyse how wall tension activates zyxin and what the mechanisms of tension-induced zyxin-mediated gene expression are (Figure 2).

Figure 2: Zyxin in static and stretched aortic endothelial cells. Zyxin (red) is localised in the focal adhesions (FA; yellow) of quiescent cells. Cyclic stretch causes translocation of zyxin to the nuclei  (Nu; blue). Paxillin (green) colocalises with zyxin exclusively in focal  adhesions but not in the nucleus (after stretch). (confocal image)

Shear Stress-Dependent Regulation of NOS3 Expression in Endothelial Cells

The second project deals with the mechanisms of fluid shear stress-induced up-regulation of the expression of the endothelial nitric oxide synthase (NOS3). The enzyme as well as its high expression due to shear stress are major factors in maintaining endothelial function. This statement can be highlighted by the fact that a frequent variant of the human nos3 gene promoter, a single nucleotide exchange at position -786 is insensitive to fluid shear and that this variant constitutes a risk factor for developing coronary heart disease and rheumatoid arthritis. Currently we try to understand how nos3 gene expression normally is increased in response to laminar shear stress and how the exchange of a single nucleotide can lead to insensitivity to shear and other inducing factors. Answers to both questions might lead to a strategy to stabilise NOS3 expression independently from laminar shear stress and, thus, prevent endothelial dysfunction and, consecutively, the development of atherosclerosis.


Recent Publications

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Assembly of vascular smooth muscle cells in 3D aggregates provokes cellular quiescence. Exp Cell Res. 2020 Mar 1;388(1):111782. doi: 10.1016/j.yexcr.2019.111782. Epub 2019 Dec 16.

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Clusters of cooperative ion channels enable a membrane-potential-based mechanism for short-term memory. Elife. 2020 Feb 7;9. pii: e49974. doi: 10.7554/eLife.49974.

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AAV-mediated TIMP-1 overexpression in aortic tissue reduces the severity of allograft vasculopathy in mice. J Heart Lung Transplant. 2020 Jan 30. pii: S1053-2498(20)31356-5. doi: 10.1016/j.healun.2020.01.1338. [Epub ahead of print]

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Mepivacaine reduces calcium transients in isolated murine ventricular cardiomyocytes. BMC Anesthesiol. 2020 Jan 8;20(1):10. doi: 10.1186/s12871-019-0926-0.

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Factors determining microbial colonization of liquid nitrogen storage tanks used for archiving biological samples. Appl Microbiol Biotechnol. 2020 Jan;104(1):131-144. doi: 10.1007/s00253-019-10242-1. Epub 2019 Nov 28.

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Shaping the heart: Structural and functional maturation of iPSC-cardiomyocytes in 3D-micro-scaffolds. Biomaterials. 2020 Jan;227:119551. doi: 10.1016/j.biomaterials.2019.119551. Epub 2019 Oct 19.

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Simulation Strategies for Calcium Microdomains and Calcium Noise. Adv Exp Med Biol. 2020;1131:771-797. doi: 10.1007/978-3-030-12457-1_31.

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Tyrphostin AG490 reduces inflammation and fibrosis in neonatal obstructive nephropathy. PLoS One. 2019 Dec 17;14(12):e0226675. doi: 10.1371/journal.pone.0226675. eCollection 2019.

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Mild metabolic stress is sufficient to disturb the formation of pyramidal cell ensembles during gamma oscillations. J Cereb Blood Flow Metab. 2019 Dec 16:271678X19892657. doi: 10.1177/0271678X19892657. [Epub ahead of print

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Risk and protective factors for post-thrombotic syndrome after deep venous thrombosis. J Vasc Surg Venous Lymphat Disord. 2019 Dec 13. pii: S2213-333X(19)30537-2. doi: 10.1016/j.jvsv.2019.10.012. [Epub ahead of print]

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AAV-Mediated Expression of AP-1-Neutralizing RNA Decoy Oligonucleotides Attenuates Transplant Vasculopathy in Mouse Aortic Allografts. Mol Ther Methods Clin Dev. 2019 Dec 13;15:246-256. doi: 10.1016/j.omtm.2019.09.009. eCollection 2019 Dec 13. Epub 2019 Oct 2.

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Amyloid, APP, and Electrical Activity of the Brain. Neuroscientist. 2019 Nov 29:1073858419882619. doi: 10.1177/1073858419882619. [Epub ahead of print]

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The mitochondrial calcium uniporter is crucial for the generation of fast cortical network rhythms. J Cereb Blood Flow Metab. 2019 Nov 13:271678X19887777. doi: 10.1177/0271678X19887777. [Epub ahead of print]

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Somatic mutations and promotor methylation of the ryanodine receptor 2 is a common event in the pathogenesis of head and neck cancer. Int J Cancer. 2019 Dec 15;145(12):3299-3310. doi: 10.1002/ijc.32481. Epub 2019 Jun 19.

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Loss of the serine protease HTRA1 impairs smooth muscle cells maturation. Sci Rep. 2019 Dec 3;9(1):18224. doi: 10.1038/s41598-019-54807-6.

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Persistent increase in ventral hippocampal long-term potentiation by juvenile stress: A role for astrocytic glutamine synthetase. Glia. 2019 Dec;67(12):2279-2293. doi: 10.1002/glia.23683. Epub 2019 Jul 17.

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Functional association of a CD40 gene single nucleotide polymorphism with the pathogenesis of coronary heart disease. Cardiovasc Res. 2019 Aug 2. pii: cvz206. doi: 10.1093/cvr/cvz206. [Epub ahead of print]


Institute of
Physiology and Pathophysiology

Heidelberg University

Im Neuenheimer Feld 326

69120 Heidelberg

Germany

Phone:+49 6221 54-4056
Fax:+49 6221 54-6364
E-mail:susanne.bechtel@
physiologie.uni-heidelberg.de