BASIC RESEARCH ON CARDIOVASCULAR AGEING AND PATHOPHYSIOLOGY
Leader: Patrick Lacolley, UMR S1116, Nancy
The objective of WP1 will be to search for and identify basic mechanisms and pathophysiological pathways of CV ageing. This WP organizes the implementation of two selected axes of research which will be conducted by the basic research teams participating in FHU-CARTAGE. Molecules and cellular senescence markers stemming from our basic research (WP1) are offered for clinical validation as biotargets/biomarkers or in bio-imaging research (WP2). In a true reciprocal translational approach, candidate genes and molecules emerging from clinical studies are tested in appropriate animal models.
Interactions between environment and genes in arterial ageing Although genetic epidemiology has extensively contributed to the elucidation of the pathophysiological mechanisms involved in the development of cardiovascular ageing, more integrative approaches will enable to provide insights into the synergy between genetic and environmental factors in order to propose novel, clinically useful biomarkers. Our area of interest will be the exploration of telomere dynamics and epigenetic factors that have recently emerged as important mechanisms in the development of early cardiovascular ageing.
Task 1: Telomere length and arterial ageing.
The prevailing view in telomere epidemiology is that leukocyte telomere length (LTL) is associated with atherosclerosis and accelerated ageing since it serves as a biomarker of the cumulative burden of inflammation and oxidative stress during adult life 3-4. Our recent results indicating that short telomeres antecede atherosclerosis suggest that TL is not just a simple marker but a genuine determinant of arterial ageing. The understanding of the mechanisms underlying telomere attrition is therefore crucial. The TELARTA project (described also in WP2), sampling human tissues, will enable the understanding of the mechanisms of the relationships between arterial ageing and telomere length. To achieve this, we examine various elements of TL dynamics simultaneously in several tissues and cell types: leukocytes, skeletal muscle, endothelial progenitor cells (EPCs) in patients with or without atherosclerosis. This model is based on 3 assumptions: (i) TL in skeletal muscle mainly reflects TL in early life, (ii) the difference in TL between muscle and leukocytes in adults mainly reflects LTL attrition during the growth period, and (iii) TL in endothelial progenitor cells reflects their proliferative ability and therefore the capacity for vessel repair during ageing.
Task 2: Epigenetic factors and pace of arterial ageing.
We will focus on inflammation which represents the central mechanism related to risk factors such as blood pressure, lipid metabolism, fibrosis, arterial stiffness and epigenetic factors. This work requires large biological collections (STANISLAS cohort)5 on which confirmatory/replication studies will be performed. A cooperation network has been established by joining the MAGIC Consortium (Meta-Analyses of Glucose and Insulin-related traits Consortium). For a given phenotype (or cluster of phenotypes), the latter will perform several steps from determination of the genetic components influencing the inter-individual variability of the intermediate phenotype to practical applications of the results in pharmacogenomics.
Axis 2. Identification of targets and bioengineering
Identification of early biomarkers of arterial and cardiac remodeling in specific age-related diseases is the ultimate challenge of several projects conducted in our laboratories: this is addressed by WP2. These studies have already identified new molecular targets that need to be brought into new clinical concepts. Those which are highly promising are detailed in the following program.
Task 1: Integrins, stiffness and thrombin generation6.
Arterial stiffness and a prothrombotic state increase consistently with age and nurture atherosclerosis and complications. We have demonstrated that αv integrins expressed at high density on vascular smooth muscle cells (VSMCs) mediate attachment to matrix proteins and increase VSMC-supported thrombin generation. The objective is to understand the
mechanisms and substratum underlying the role of VSMC-expressed αv integrins in linking arterial stiffness with thrombin generation within the vessel as well as platelet-vessel wall interactions through collaboration with Cecile Denis (UMR_S 770, Paris). The objectives are 1 to characterize the role of VSMCs and their αv integrin receptors in arterial elasticity and hemostasis of inducible VSMC-specific αv mutant mice and VSMC from induced pluripotent stem cells from mutant mice, 2 to determine the role of inflammation, 3 to characterize the role of transcriptional pathways on αv-mediated functions of VSMCs in cultured cells, isolated vessels and αv mutant mice in collaboration with Zhenlin Li (ERL U1164, Paris), 4 to validate our hypotheses in human tissue and 5 to evaluate therapeutic strategies targeting signaling pathways in VSMCs in mice.
Task 2: Mineralocorticoid receptor (MR)7-8
The beneficial or deleterious effects of aldosterone are site-specific and depend on the cellular context and pathological setting. We have shown that MR activation acts on endothelial cells to protect against thrombosis in physiological conditions. This protective effect may be lost with age-associated endothelium dysfunction and vascular stiffness consistent with the beneficial effect of MR antagonists in cardiovascular diseases. We have shown that MR activation is involved in the cardiovascular and renal profibrotic process through several pathways (Gal-3, Cardiotrophin-1, the latter being involved in the cardiovascular ageing process). MR is also one of the pathways under investigation within the EU FP7 fibrotarget program coordinated by Nancy CIC http://www.fibrotargets.eu. Through collaboration with Frederic Jaisser (UMR_S872, Paris), we will have
access to transgenic mice with either smooth muscle- or endothelial-specific deletion of MR. By using these models, we should be able to identify the role of cell-specific MR expression and or activation.
Task 3: Cytokines, histones and inflammation. Cytokines (such as cardiotrophin-1, see Task 2) and extracellular histones are potent activators of platelets and vascular cells and these effects are partly mediated by toll-like receptors. Our “Competent Center for Rare Vascular, Systemic and Immune Diseases” provides a unique opportunity to address the role of histones as a mechanistic bridge between inflammation, vascular remodeling and thrombosis in the anti-phospholipid syndrome. Pro-inflammatory signals are crucial in mediating the response to injury, regulating debridement of the infarcted myocardium and initiating the cellular events necessary for scar formation. Triggering receptor expressed on myeloid cells 1 (TREM-1)9 is an immune-receptor that acts as an amplifier of the innate immune response. We have shown that blockade of TREM-1 activation protects from hyper-responsiveness and death in various models of severe infections. We aim to examine the role of TREM-1 in orchestrating the inflammatory response that follows myocardial infarction in mice (TREM-1 KO), rats and mini-pigs. With regard to tissue bioengineering, we propose to differentiate human mesenchymal stem cells into endothelial-like cells on surfaces coated with polyelectrolyte multilayer film. The ultimate goal is to engineer suitable blood vessel substitutes which could be stored in vascular bank conditions.
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2 Benetos A, et al. Pulse pressure: a predictor of long-term cardiovascular mortality in a French male population. Hypertension. 1997 Dec;30(6):1410-5.
3 Benetos A, Labat C et al. A model of canine leukocyte telomere dynamics. Ageing Cell. 2011;10:991-5.
4 Benetos A, Labat C… et al. Tracking and fixed ranking of leukocyte telomere length across the adult life course. Ageing Cell. 2013;12:615-21
5 Sophie Visvikis-Siest and Gerard Siest. The STANISLAS Cohort: a 10-year follow-up of supposed healthy families. Gene-environment interactions, reference values and evaluation of biomarkers in prevention of cardiovascular diseases. Clin Chem Lab Med. 2008;46(6):733–74
6 Regnault, V;.... Lacolley, P Tissue factor pathway inhibitor: a new link among arterial stiffness, pulse pressure, and coagulation in postmenopausal women. Arterioscler. Thromb. Vasc. Biol., 2011; 31:1226-32
7 Lagrange J, Li Z, … Wahl D, Lacolley P, Jaisser F, Regnault V. Endothelial mineralocorticoid receptor activation enhances endothelial protein C receptor and decreases vascular thrombosis in mice. FASEB J. 2014;28:2062-72
8 Galmiche G, Pizard A, …, Labat C, Lacolley P, Jaisser F. Smooth muscle cell mineralocorticoid receptors are mandatory for aldosteronesalt to induce vascular stiffness. Hypertension. 2014;63:520-6.
9 Gibot S et al. Soluble triggering receptor expressed on myeloid cells and the diagnosis of pneumonia. N. Engl. J. Med., 2004 vol. 350(5) pp. 451-8