MOLECULAR, BIOMECHANICAL, and GENETIC MECHANISMS OF ARTERIAL STIFFNESS
Co-Dir. Name Richard A. Cohen
Dept Medicine/Whitaker Cardiovascular Institute
Title Professor and Director, Vascular Biology Section
Email racohen@bu.edu
phone 617-638-7115
Co-Dir. Name Kathleen Morgan
Dept Health Sciences Department, Sargent College, Charles River Campus
Title Professor and Chair
Email kmorgan@bu.edu
phone 617-353-7464
Admin Karen Hennessey
khenness@bu.edu
617-638-7128
YOU ARE INVITED!
Arterial Stiffness ARC jointly with Whitaker Cardiovascular Institute Seminar
Thursday, FEB 21, 12 noon – 1pm, BU Medical Campus, 670 Albany St, room X107/108 (lunch provided)
Speaker: David G. Harrison, MD, FACC, FAHA
Betty and Jack Bailey Professor of Medicine and Pharmacology
Director, Division of Clinical Pharmacology
Director of the Center for Vascular Biology
Vanderbilt University School of Medicine
Nashville
Title: “Inflammation, Immunity and Hypertension”
If you want to participate remotely via web, please contact Dr. Francesca Seta (setaf@bu.edu).
OVERVIEW OF GOALS AND MISSION:
ABSTRACT
Arterial stiffness, measured in large epidemiological studies including the Framingham Heart Study, is a risk factor for the complications of cardiovascular disease that is independent of classical metabolic and genetic risk factors. An Arterial Stiffness pre-ARC began in December 2009. The proposed ARC would link people interested in molecular, biomechanical, and genetic mechanisms of arterial stiffness. Determining these mechanisms in rodent and cellular models will be important for greater understanding of why stiffness occurs, how it is linked to hypertension and end organ tissue damage in cardiovascular disease, and how therapeutics could be targeted to reverse the pathology. The pre-ARC has focused on 1) ultrasound methodology with which ARC members can assess aortic stiffness in rodent models, and 2) genetic studies in rodents and humans of arterial stiffness. Both have been guided by Gary Mitchell, an internationally recognized expert in arterial stiffness. The goals of the ARC are to extend these activities by 1) measuring aortic stiffness in vivo and in vitro to establish biomechanical properties for which mechanism can be explored, 2) performing gene expression array studies on the aorta of rodent models to seek mechanistic target genes, and 3) sponsoring seminar speakers on this topic.
ARC MEMBERS:
| Name/Title | Dept/School | |||
| Richard A. Cohen,
PhD; Professor |
Medicine | Director | racohen@bu.edu | |
| Kathleen Morgan, PhD; Professor | Sargent College, Charles River Campus | Co-Director | kmorgan@bu.edu | |
| ARC Members: | ||||
| Francesca Seta, PhD; Assistant Professor | Medicine | setaf@bu.edu | ||
| Bela Suki, PhD; Professor | Biomedical Engineering, Charles River Campus | bsuki@bu.edu | ||
| Gary Mitchell, PhD; President | Cardiovascular Engineering, Inc, Norwood, MA | GaryFMitchell@mindspring.com | ||
| Victoria Bolotina, PhD; Professor | Medicine | bolotina@bu.edu | ||
| Barbara Smith, PhD; Professor | Biochemistry | bdsmith@bu.edu | ||
| Barbara Schreiber, PhD; Professor | Biochemistry | schreibe@bu.edu | ||
| Matthew Layne, PhD; Assistant Professor | Biochemistry | mlayne@bu.edu | http://www.bumc.bu.edu/biochemistry/people/faculty/mlayne/ | |
| Xiao Yong Tong, PhD; Assistant Professor | Medicine | xytong@bu.edu | ||
| Katya Ravid, DSc/PhD; Professor | Medicine | kravid@bu.edu | ||
| Victoria Herrera, PhD; Professor | Medicine | vherrera@bu.edu | ||
| Joseph Vita, PhD; Professor | Medicine | jvita@bu.edu | ||
| Nelson Ruiz-Opazo, PhD; Professor | Medicine | nruizo@bu.edu | ||
| Joyce Wong, PhD; Assistant Professor | Engineering, Charles River Campus | jywong@bu.edu |
ARC AS A RESOURCE
The Arterial Stiffness Pre-ARC has met 7 times since 12/2009. An initial series of meetings included discussions of the NIH NHLBI initiative in arterial stiffness and individual pre-ARC members own interest in arterial stiffness. One meeting consisted of an Evans Center sponsored seminar by Dr. Gary Mitchell, an expert in clinical hemodynamic measurements of arterial stiffness. Dr. Mitchell reviewed the hemodynamic connections between large artery stiffness and hypertension, various measurements of stiffness, and ongoing genome wide association studies to investigate gene single nucleotide polymorphisms (SNPs) associated with arterial stiffness. Following this seminar, Dr. Mitchell became a consulting pre-ARC investigator and has attended pre-ARC meetings. He has participated in discussions of PWV measurement in rodents and in genetics of vascular stiffness. Two additional meetings were held to discuss measurements of arterial stiffness in rodents in which Drs. Mitchell and Herrera discussed with participants ultrasound, pressure, and flow measurements that could be used to measure stiffness in live animals by methods similar to those being used in people. The pre-ARC has been supported by the participation of several BUMC investigators who have considerable expertise and experience in arterial stiffness measurements and evaluation in the Framingham Heart Study (Vita, Ramachandran, Levy).
B.1. Description of the proposed specific ARC project(s), including:
B.1.a. Background
With advancing age or prematurely in obese subjects, arterial stiffness increases and has been implicated in the altered vascular hemodynamics that ultimately lead to the development of hypertension (Mitchell GF, Hypertension 2004). Stiffness begins in the aorta and large arteries, but because artery stiffness transmits higher pressures to the smaller resistance arteries, large artery stiffness is implicated in the microvascular complications of hypertension in the kidney and brain. Data acquired at the Framingham Heart Study (FHS) demonstrate that vascular stiffness is an independent risk factor for cardiovascular disease endpoints (Figure 1), however the mechanisms involved and possible therapeutic approaches remain unclear. Arterial stiffness is assessed in patients by measurements of pulse wave velocity (PWV), and it has been proposed that routine measurements of PWV might provide an earlier and therefore better predictor of cardiovascular disease and preventive treatments. Mechanisms of increased stiffness likely include altered properties of elastin and collagen, as well as increased tone of smooth muscle cells resulting from increased stiffness of the connections between cells and matrix or from endothelial dysfunction. Thus, further investigations into the mechanisms of arterial stiffness will to address the vascular biology of the arterial wall and its component cells – smooth muscle, endothelium, fibroblasts, and bone marrow derived cells.
The Arterial Stiffness Pre-ARC consists of a group of investigators across both campuses interested in the structural, biochemical, physiological, molecular and genetic mechanisms that underlie arterial stiffness as it relates to negative cardiovascular disease outcomes. With the help of the Animal Ultrasound Core, directed by Dr. Victoria Herrera, the group has established the ability to assess PWV in rodent models of hypertension and arterial stiffness (Figure 2). At this writing, at least 5 such models being studied by pre-ARC members, including obese and aging mice and salt-sensitive rats have been demonstrated to have increased arterial stiffness. For example, in normal mice we have obtained values of approximately 2 mm/msec, which is in the same range as the normal value determined in children, and statistically significant 2- to 2.5-fold increases have been measured in high fat diet-fed and very aged mice, as well as in one novel transgenic mouse.
Another effort initiated by the pre-ARC with Dr. Mitchell is designed to evaluate correlates of genes of interest to the pre-ARC members with SNP’s in those genes determined to correlate with increased arterial stiffness in a multicenter, genome wide association study.
B.1.b. Rationale and AIMS of research for the upcoming year
1. To measure arterial stiffness assessed by alterations in pulse wave velocity in rodent models hypothesized by API’s to have arterial stiffness based on their previous studies on the protein or disease. An expanding number of ARC investigators will be able to have PWV measured in their various mouse models that they believe might have arterial stiffness, thereby achieving pathological significance for their gene or protein of interest.
2. To measure gene expression in mouse aortas that prove to be stiff in Aim #1 using RTPCR array chip technology in the BU chip core. The genes that are most important in mediating in the integrated development of stiffness are unknown. We hope to detect novel genes important for stiffness in two mouse models of stiffness, obese and aged mice, and in that way stimulate further study by the ARC members.
3. To collaborate with Gary Mitchell to test if genes of interest to ARC members may contain polymorphisms detected in a multicenter genome wide association study of arterial stiffness in ~30,000 human subjects. Detecting SNP’s in genes of interest to ARC members is seen as important for further development of their research programs and for establishing significance of their genes of interest to arterial stiffness in humans.
4. Make biomechanical measurements of stiffness to directly assess in vitro aortic stiffness in mice shown to have increased arterial pulse wave velocity. These measurements are seen as necessary to link in vivo properties of stiffness to biomechanical, and therefore biochemical and molecular mechanisms. An obvious reason is to discriminate whether stiffness in various models results from active (i.e. smooth muscle tone) or passive structural components. These experiments will also allow determination of endothelial contributions and coordination with biochemical measurements.
5. Seminar speakers on topics related to clinical and experimental arterial stiffness, hypertension, matrix, smooth muscle, and endothelium will be invited to increase knowledge and awareness of the group, and a mini-symposium will be held on the topic.
B.1.c. PLAN- an outline of how will these aims be achieved, listing the investigators involved and their interdisciplinary expertise
1: Several of the pre-ARC members have already started to make measurements in their particular mouse/rat of interest. Methods are being evaluated and upgraded based on experience, and ARC members can take advantage of shared experience that will be discussed at ARC meetings. Drs. Cohen and Herrera have been intensively refining methods for PWV measurements in mice. Mice from laboratories of Dr. Cohen, Bolotina, Smith, and Schreiber have already had preliminary studies of PWV. The ARC funds will support the ultrasound core user and analysis fees required for the core staff to do preliminary studies on new models. By collaborating with Drs. Cohen and Ruiz-Opazo, methods will also be available with which to measure blood pressure in rodents with arterial stiffness in order to study the pathophysiological link to hypertension.
2: The Affymatrix GeneChip® Gene 1.0 ST Array, containing primers for 28,000 mouse genes will be used to assess mRNA expression in aortas from 5 obese and 5 aged mice, determined to have increased stiffness, along with 5 of their respective controls. These arrays will be tested in the BUSM gene expression core, and the data made available to ARC members for analysis.
3: Limited lists of genes of interest are submitted to Dr. Mitchell and are being evaluated by statisticians attached to the multi-center GWAS study. Methods are being tested to group genes into focused areas, in order to decrease second order statistical error.
4: Role of Bela Suki: Direct measurements will assess passive and active tone of mouse aorta, to discriminate contributions of extracellular matrix, elastin, collagen, and smooth muscle tone. These measurements are viewed as needed to realize mechanistic insights into specific molecular mechanisms of active and passive stiffness.
5: Seminar speakers will be sought from the following areas related to arterial stiffness: 1) vascular smooth muscle tone, 2) extracellular matrix components, 3) hemodynamics, 4) clinical measurements 5) epidemiology and genetics. In the last year of activity, outstanding intramural and extramural investigators with expertise in arterial stiffness have been invited to seminars and work-in-progress discussions:
Date Seminar speaker/Presenter Seminar title/topic
12-21-10 Suki B. Work in progress on mechanical properties of the lung related to elastin and collagen; discussion on stretching apparatus for in vitro stiffness measurement.
Mitchell G. Significance of arterial stiffness from clinical prospective and GWAS studies.
02-10-11 Herrera V. Work in progress on arterial stiffness and salt-sensitive hypertension in rats.
Schreiber B. Work in progress on serum amyloid A-induced decrease in elastin and collagen in smooth muscle cells.
03-08-11 Cassis L. (invited speaker) “The Renin-Angiotensin System in Obesity and Vascular Diseases”. Seminar followed by discussion with Arterial Stiffness ARC members.
03-29-11 Berkowitz D. (invited speaker) Arginase and transglutaminase-2 in aging and arterial stiffness Seminar followed by discussion with Arterial Stiffness ARC members.
06-06-11 Genco C. Work in progress on the role of Toll-like receptors in P.Gengivalis-induced inflammation, atherosclerosis, arterial stiffness.
Gao T,/Suki B. Work in progress on in vitro measurements of arterial stiffness.
07-12-11 Mitchell G. Genetics of Arterial stiffness and presentation of results from AortaGen Consortium GWAS.
08-03-11 (Joint seminar) Bolton (mitoARC guest speaker) Mitochondrial retinal damage during aging
Leopold J. (invited speaker) Aldosterone-dependent autophagy and arterial stiffness
10-06-11 Reinhart-King C. (invited speaker) “The Role of Extracellular Matrix Stiffening in Endothelial Cell Function”.
11-14-11 Seta F. Update on Arterial Stiffness ARC-sponsored mRNA microchip for genes involved in arterial stiffness in mouse models.
Weisbord R. Work in progress on measurements of arterial stiffness on various mouse models from Arterial Stiffness ARC members.
02-28-12 Zhang Yanhang (BU Dept Biomed Engineering) The role of elastin in the mechanics of large arteries
03-21-12 Humphrey Jay (Yale University; invited speaker; seminar organized by BU Dept Biomed Engineering) Biomechanics and Mechanobiology of Abdominal Aortic Aneurysms
05-08-12 Mitchell Gary Genome wide evaluation of arterial stiffness: A pathways approach
06-20-12 Seals Douglas (University of Colorado, Boulder; invited speaker) Strategies for the prevention and treatment of age-associated arterial stiffness
09-19-12 Rafael deCabo (NIA, invited speaker) Resveratrol vascular protection from mice to monkeys
11-13-12 Weisbrod, Aprahamian, Ravid: Discussion of arterial stiffness in genetic models from ARC investigators
12-04-12 Wagenseil Jessica (Saint Louis University; invited speaker)Elastin, arterial stiffness and hypertension
B.1.d. The novelty, impact and significance of your proposed projects, including relevance to human disease
This ARC will use novel approaches to study the emerging concept that cardiovascular disease can be detected early by noninvasive measurements of arterial stiffness. The ARC members constitute members of the BU community with diverse expertise in vascular biology, hypertension, smooth muscle physiology, extracellular matrix, biomechanics, and genetics for which the concept of arterial stiffness represents increased significance for their own areas of focus. We will apply novel methods by 1) establishing mouse models of increased pulse wave velocity in order to make the translational link between human measurements and those in the rodent in which mechanisms can be studied, 2) measuring arterial stiffness directly in isolated rodent aortas order to make the link from in vivo measurements to active and passive properties of the blood vessel in order to establish biochemical and biomechanical mechanisms, 3) detecting novel genes of interest by probing aortas of obese and aging mice, 4) determining if expression of genes in which polymorphisms are identified to be associated with arterial stiffness are also affected in rodents with stiffness. The significance of ARC studies is to establish rodent models of stiffness in which mechanisms and biomarkers of stiffness in humans might be confirmed. Therapeutic approaches can then be tested by ARC members in these rodent models.
B.2. Specific goals of the ARC as a whole and plans for achieving them:
1: ARC funds will be used to support small animal ultrasound core measurements and analyses of vascular stiffness in rodents provided by ARC members other than those who already have funded grants to do so (ie. Cohen, Ruiz-Opazo). Dr. Herrera and Cohen will further refine methods for these measurements together with our consultant, Gary Mitchell. Ten API currently have or are developing mouse or rats that they hypothesize might have arterial stiffness that will need to be screened.
2: mRNA will be isolated from aortas of obese and aging mice during the first 3 months of the ARC so that data can be made available for ARC members during the first year.
3. ARC members will develop lists of genes of interest focused on each of the research areas of ARC members and submitted to Dr. Mitchell. While the results of his GWA study are currently unpublished, Dr. Mitchell has indicated many significant changes in genes have been identified. By submitting limited numbers of genes and by grouping them according to function, we hypothesize that additional significant associations of polymorphisms in genes of interest will be acquired by limiting second order statistical error.
4. Dr. Bela Suki, an expert in biomechanical measurements of stiffness in Biomedical Engineering on the CRC has been recruited by the ARC. ARC funds will support a part time student to use equipment already present in his lab to measure stiffness in rodents identified by ARC members to have increased pulse wave velocity. In addition, preliminary studies by Dr Tsui and Dr. Morgan will begin to develop the use of atomic force microscopy and optical tweezers to measure stiffness of single isolated smooth muscle cells and their connections to the matrix.
5: Seminar speaker travel and accommodation expenses will be supported by the ARC.
B.2.a. Plans for collaborative, interdisciplinary research and how will the ARC format help you promote NEW discovery?
Collaborative studies will continue to develop improved methods for stiffness measurements as it continues to be measured in live rodents and in vitro on isolated rodent aortas of ARC members. We expect that ARC members will develop collaborations together. For instance, Dr. Morgan and Tsui will develop methods to measure stiffness in individual cells. In their funded programs Drs. Cohen, Ruiz-Opazo, and Herrera use both tail cuff and telemetry blood pressure measurements, and as members identify stiffness in their rodent models, they can collaborate with these investigators to have blood pressure evaluated in their rodents to determine if stiffness is associated with hypertension. Examples of other potential collaborative efforts are 1) use of immunohistochemistry core facilities to determine changes in matrix or protein expression in stiff aortas, 2) development of nanoparticles for local delivery of genes or drugs expected to improve stiffness, 3) with identification of mice with alterations in the expression of genes identified in the human studies, the members can obtain transgenic mice of their interest and have stiffness measurements in them using ARC funds. It is also evident to all ARC members that the topic of vascular stiffness encompasses the interest of a large number of basic, translational, and clinical investigators on both the BUSM and CRC campuses, making it an ideal topic for programmatic development within the BU community.
B.2.b. Envisioned application of technologies in the ARC. See above
B.3.c. Plans for frequency of meetings, content (seminars, work in progress, presentations by trainees etc.) and criteria for self-evaluation.
ARC progress meetings will continue monthly. Members who have stiffness studies performed using ARC funds will present their findings for discussion at ARC meetings. This will allow the ARC to include new models into its repertoire of rodent models with arterial stiffness. Other sessions will be devoted to methods being developed by ARC investigators. In addition, 6 seminar speakers are anticipated in the first year. Annual reports will include newly established collaborations, publications and project development by ARC investigators on the subject of stiffness.
B.3.d. Plans for seeking external support (individual grants and/or PPG)
Pre-ARC meeting discussions on this subject have suggested that bringing the diverse interests and expertise in the ARC together for a program funding application would probably require 2 – 2.5 years. ARC members will be encouraged to develop and submit collaborative applications as individual projects develop. One advantage for the ARC is that two ARC investigators already have two NIH grants to study arterial stiffness in rodents (Cohen, Ruiz-Opazo), which should help to stimulate collaborations within the ARC group. In addition, Drs. Mitchell, Ramachandran and Vita are ARC members who have extensive experience in stiffness measurements and analyses in Framingham Heart Study population, which should allow us to develop collaborative projects with them on biomarkers and genetics of arterial stiffness.
