Strategic Plan for Lung Vascular Research
An NHLBI-ORDR Workshop Report
Serpil Erzurum1, Sharon I. Rounds2, Troy Stevens3, Micheala Aldred4, Jason Aliotta5, Stephen L. Archer6,
Kewal Asosingh1, Robert Balaban7, Natalie Bauer3, Jahar Bhattacharya8, Harm Bogaard9, Gaurav Choudhary2,
Gerald W. Dorn, II10, Raed Dweik1, Karen Fagan3, Michael Fallon11, Toren Finkel12, Mark Geraci13,
Mark T. Gladwin14, Paul M. Hassoun15, Marc Humbert16, Naftali Kaminski14, Steven M. Kawut17,
Joseph Loscalzo18, Donald McDonald19, Ivan F. McMurtry3, John Newman20, Mark Nicolls21,
Marlene Rabinovitch22, Judy Shizuru23, Masahiko Oka3, Peter Polgar24, David Rodman25, Paul Schumacker26,
Kurt Stenmark27, Rubin Tuder13, Norbert Voelkel9, Eugene Sullivan28, Richard Weinshilboum29, Mervin C. Yoder30,
Yingming Zhao31, Dorothy Gail32, and Timothy M. Moore32
1Department of Pathobiology, Cleveland Clinic, Cleveland, Ohio;2Department of Medicine, Providence Veterans Affairs Medical Center, Warren
Alpert Medical School of Brown University, Providence, Rhode Island;3University of South Alabama, Center for Lung Biology, Mobile, Alabama;
4Genomic Medicine, Cleveland Clinic, Cleveland, Ohio;5Division of Pulmonary, Sleep, and Critical Care Medicine, Department of Medicine, Warren
Alpert Medical School of Brown University, Providence, Rhode Island;6Section of Cardiology, Department of Medicine, University of Chicago,
Chicago, Illinois;7Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, Bethesda, Maryland;8Department of Medicine and
Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York City, New York;9Division of
Pulmonary and Critical Care Medicine, Department of Medicine, Virginia Commonwealth University, Richmond, Virginia;10Department of Internal
Medicine and Center for Pharmacogenomics, Washington University School of Medicine, St. Louis, Missouri;11Division of Gastroenterology,
Hepatology, and Nutrition, Department of Medicine, University of Texas Health Science Center at Houston Medical School, Houston, Texas;
12Translational Medicine Branch, National Heart, Lung, and Blood Institute, Bethesda, Maryland;13Department of Medicine, University of Colorado
at Denver, Denver, Colorado;14Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, and Vascular Medicine
Institute, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania;15Division of Pulmonary and Critical Care Medicine, Department of
Medicine, Johns Hopkins University, Baltimore, Maryland;16Universite ´ Paris-Sud 11, Ho ˆpital Antoine Be ´cle `re, Paris, France;17Department of
Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania;18Department of Medicine, Brigham and Women’s Hospital,
Harvard Medical School, Boston, Massachusetts;19Department of Anatomy, University of California San Francisco, San Francisco, California;
20Department of Allergy, Pulmonary, and Critical Medicine, Vanderbilt School of Medicine, Nashville, Tennessee;21Division of Pulmonary and
Critical Care, Department of Medicine, Stanford University School of Medicine, Stanford, California;22Vera Moulton Wall Center for Pulmonary
Vascular Disease, Stanford University School of Medicine, Stanford, California;23Department of Medicine/Blood and Marrow Transplantation,
Stanford University School of Medicine, Stanford, California;24Department of Biochemistry, Boston University School of Medicine, Boston,
Massachusetts;25Novartis Institutes for Biomedical Research, Cambridge, Massachusetts;26Department of Pediatrics, Northwestern University,
Chicago, Illinois;27Department of Pediatrics, University of Colorado at Denver, Denver, Colorado;28United Therapeutics, Silver Spring, Maryland;
29Department of Molecular Pharmacology and Experimental Therapeutics and Medicine, Mayo Medical School-Mayo Clinic, Rochester, Minnesota;
30Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana;31Ben May Department for Cancer Research, University of
Chicago, Chicago, Illinois; and32Division of Lung Diseases, National Heart, Lung, and Blood Institute, Bethesda, Maryland
The Division of Lung Diseases of the National Heart, Lung, and
Blood Institute, with the Office of Rare Diseases Research, held
a workshop to identify priority areas and strategic goals to enhance
and accelerate research that will result in improved understanding
ofthe lungvasculature, translational research needs,andultimately
the care of patients with pulmonary vascular diseases. Multidisci-
plinary experts with diverse experience in laboratory, translational,
and clinical studies identified seven priority areas and discussed
The focus for future research efforts include the following: (1) bet-
(Received in original form June 7, 2010; accepted in final form September 9, 2010)
Supported by the Division of Lung Diseases, National Heart, Lung, and Blood
Institute, NIH, Office of Rare Diseases Research, Office of the Director, NIH.
Correspondence and requests for reprints should be addressed to Timothy M.
Moore, M.D., Ph.D., Division of Lung Diseases, National Heart, Lung, and Blood
Institute, National Institutes of Health, 6701 Rockledge Drive, Rockledge Centre
II, Room 10182, Bethesda, MD 20892. E-mail: firstname.lastname@example.org
This article has an online supplement, which is accessible from this issue’s table of
contents at www.atsjournals.org
Am J Respir Crit Care Med
Originally Published in Press as DOI: 10.1164/rccm.201006-0869WS on October 8, 2010
Internet address: www.atsjournals.org
Vol 182. pp 1554–1562, 2010
AT A GLANCE COMMENTARY
Scientific Knowledge on the Subject
Basic lung vascular research is progressing and novel
translational and clinical study opportunities are emerg-
ing, particularly for pulmonary arterial hypertension.
The investigative community is assessing how to move
forward to acquire new knowledge, apply new technol-
ogies, and develop new tools to conduct modern studies
in lung vasculature research so that lung health may be
What This Study Adds to the Field
This report represents a collective body of scientific expert
opinion provided to the National Heart, Lung, and Blood
Institute for use in strategic support planning. The recom-
mendations given here will be of interest to the general
a summary of the directions lung vascular research may
take in the near future.
ter characterizing vascular genotype–phenotype relationships and
incorporating systems biology approaches when appropriate; (2)
advancing our understanding of pulmonary vascular metabolic
regulatory signaling in health and disease; (3) expanding our
function and disease; (4) improving translational research for iden-
tifyingdisease-modifying therapiesfor the pulmonary hypertensive
diseases; (5) establishing an appropriate and effective platform for
advancing translational findingsinto clinicalstudiestesting;and(6)
developing the specific technologies and tools that will be enabling
for these goals, such as question-guided imaging techniques and
lung vascular investigator training programs. Recommendations
from this workshop will be used within the Lung Vascular Biology
Keywords: right ventricle; pulmonary hypertension; metabolism; ge-
Lung perfusion is accomplished by the pulmonary circulation,
which originates from the right ventricle, and the bronchial
circulation, which originates from the aorta. The low-resistance
characteristics of the pulmonary circulation allow it to accom-
modate the entire cardiac output while maintaining low pulmo-
nary vascular pressures, thereby preventing hydrostatic damage
to the delicate alveolar blood–gas barrier. The bronchial
circulation is approximately 3% of total lung perfusion and
provides most of the nutrients and oxygen to the airways and
the large pulmonary vessels via the vasa vasorum. In addition,
the lung lymphatic vessels remove extravascular water and
Despite significant discoveries in vascular biology, there
remain gaps in our knowledge of lung diseases characterized
by vascular remodeling, proliferative vessel growth, and/or loss
of the pulmonary vascular bed. One lung vascular disease is
pulmonary arterial hypertension (PAH), which is now described
as a panvasculopathy of elastic, muscular, and nonmuscular
pulmonary arteries and arterioles. Although a rare disorder (1),
major improvements in the lives of patients with PAH have
directly resulted from basic lung vascular research. However,
without disease-modifying therapies, PAH remains a progres-
sive and rapidly fatal disease. Furthermore, a report from the
Centers for Disease Control and Prevention (Atlanta, GA)
indicated that during 1980–2002, death rates and hospitalization
rates significantly increased for ‘‘pulmonary hypertension’’ as
either any contributing cause of death or as any listed hospital
diagnosis (2). The etiology of this observation was hypothesized
to be multifactorial, but the economic impact of this trend was
clear, as was the need to further advance our scientific un-
derstanding of lung vascular health and disease, particularly in
an aging U.S. population.
To expedite progress in lung vascular research, an invita-
tional workshop of leading experts in laboratory, translational,
and clinical studies was held. The objectives of the workshop
were to review the state of science in lung vascular biology,
identify emerging opportunities, define research directions, and
make recommendations to the National Heart, Lung, and Blood
Institute (NHLBI) of the National Institutes of Health (NIH,
Bethesda, MD) to use for strategic planning. Emphasis on PAH
emerged, because several translational research opportunities
were identified specific to this clinical condition. Although a
primary focus on the pulmonary circulation is presented here,
we acknowledge that key areas for investigation exist specific to
the bronchial and lung lymphatic networks, but time constraints
did not allow for open discussion of all topics. Selected slides
presented at the meeting are included in the online supplement.
Integrating ‘‘-omics’’ and Systems Biology Approaches
The study of pulmonaryvascular disease has been accelerated by
genomicdiscoveries,but the potential forevengreater impact on
disease pathogenesis and treatment may be attained with the
advent of systems biology approaches. Much of what we are
learning is being derived from studies of familial PAH. In 2000,
researchers from Columbia University (New York, NY) and
Vanderbilt University (Nashville, TN) reported that a mutation
in a transforming growth factor (TGF)-b receptor superfamily
member was associated with familial PAH (3, 4). Heterozygous
germ line mutations of bone morphogenetic protein receptor-2
(BMPR2) underlie up to 80% of cases of familial PAH (3, 4).
Gene rearrangements of BMPR2 are also common (5, 6). In-
vestigation of other signaling molecules within the BMPR2
pathway has led to the discovery of other mutations associated
with PAH. Patients with hereditary hemorrhagic telangiectasia
may exhibit pulmonary hypertension. In these cases, coding
changes in activin receptor–like kinase-1 (ALK1) are associated
withdisease (7).Kindred functional analysis of ALK1 showsthat
the mutations are the cause of pulmonary hypertension in pa-
tients with hereditary hemorrhagic telangiectasia (8). Endoglin,
an accessory TGF-b receptor that is highly expressed during
angiogenesis, is essential for ALK1 signaling. Mutations in en-
doglin have also been reported in patients with PAH (9). Thus,
disruptions of the BMPR2 pathway are present in most cases of
familial PAH (10). The impact of BMPR2 mutations in affecting
global lung vascular function and disease will need to be
ascertained by continued investigation.
In addition to better understanding sequence variations, it is
becoming clear that epigenomic regulation plays an important
role in the manifestation of lung vascular disease (11). Pro-
liferation, migration, survival, and inflammation are processes
critically regulated by protein posttranslational changes. The
present understanding of posttranslational modifications affect-
ing phenotypic responses during pulmonary vascular remodel-
ing is limited. Histone modifications can induce epigenetic
changes, affecting gene expression and phenotype long after
the stimulus is removed. These changes are likely to play key
roles in regulating phenotypic and epigenetic responses in
pulmonary vascular diseases.
Advances in our understanding of genetics and epigenetics in
lung vascular health and disease may be achieved by employing
novel methodologies and analysis techniques. Expression stud-
ies (transcriptional profiling) on lung tissue are limited by small
sample sizes (12). However, alternative strategies using surro-
gate tissue (peripheral blood) validate the utility of transcrip-
tional profiling (13). Gleaning information from diseased lung
tissue samples more easily obtained by biopsy may also provide
useful information for lung vascular disease. For example,
a sampling of lung tissue expression array analysis demonstrates
similar pathway disruption among PAH and pulmonary fibrosis
(14). Finally, putting all relevant ‘‘-omic’’ information into
a systems biology model of pulmonary vascular disease may
provide unique insights (15).
Determine DNA variation. Examination of DNA sequence
variation related to disease states and defined phenotypes may
enable highly accurate determination of the importance of rare
Explore gene expression and control of transcription. A broad
approach to analysis of gene expression, including involved
tissues, laser capture of defined elements, cell line–based exam-
NHLBI Workshop 1555
inations, and surrogate tissues such as blood, will likely be re-
quired. Technologies have emerged to examine the control of
transcription including epigenomic modifications and the role of
microRNA and RNA-binding proteins in disease processes.
Define epigenetic modifications. Epigenetic mechanisms alter
gene expression responses in vascular and progenitor cells.
Basic studies to define these mechanisms in the context of
vascular remodeling will be important.
Identify protein posttranslational modifications. Modifica-
tions such as thiol-redox changes likely enhance pulmonary
vascular disease. Distinguishing static and constitutive modifi-
cations from those responsible for the reversible regulation of
pathogenic cell behavior is an important goal.
Define proteomic and metabolomic signatures. Augmented
capacities in proteomic technologies enable broader examina-
tion of proteomic profiles, posttranslational modification, and
metabolomic signatures. Application of these technologies
holds promise for discovering disease pathogenesis and bio-
Institute systems biology approaches. Integration of broad-
based approaches is essential for better defining the pathogen-
esis of lung vascular disease and therapeutic interventions.
Network analysis can be derived for simple canonical system
motifs, or more complex, scale-free, systems may be envisioned
to examine the potential for disease similarities by common
hubs and nodes. Application of computational biology is
expected to reveal new diagnostic and therapeutic targets.
Identify specific clinical cohorts. A comprehensive and in-
tegrated approach to patient enrollment and development of
databases of large cohorts is the best method to define pheno-
types. Because lung vascular disease has protean manifesta-
tions, yet remains relatively rare, a consortium approach to
acquisition of cohorts will likely be required.
Metabolic signaling contributes importantly to cellular behavior
in pulmonary vascular disease. Improved understanding of the
systems regulating these signals is important for identifying
potential therapeutic approaches. Interactions among these
systems likely create synergisms that align with environmental
and genetic factors to initiate or promote lung vascular prob-
lems. In PAH, the observations of increased glycolysis (16) in
the pulmonary vasculature coupled with a hypertrophied right
ventricle indicate the need for comprehensive profiling of the
metabolism of both heart and lung.
Hypoxia and shear stress, recognized triggers in the de-
velopment of vascular remodeling, alter cellular metabolic
signaling pathways that regulate proliferation, migration, cell
survival, inflammation, and other components of pulmonary
vascular diseases (17–22). Reactive oxygen species (ROS) medi-
ate many of the cellular responses to hypoxia, shear stress, and
TGF-b family members. ROS arise from multiple sources, in-
cluding mitochondria, NAD(P)H oxidase complexes, and cyto-
chrome P-450s. Genetic variation affecting estrogen metabolism,
such as CYP1B1, a member of the cytochrome P-450 family,
may underlie the enhanced susceptibility of women to PAH.
Understanding the mechanisms responsible for regulating ROS
production in various cell types, the targets of oxidant signals,
and ROS contributions to pulmonary vascular disease is impor-
tant for both pathogenesis and potential treatments.
Signaling pathways involving mitochondria, including fission
and fusion, may influence vascular remodeling. Altered glucose
utilization by lung vascular cells may enhance the proliferation
potential, although our understanding of the underlying mech-
anisms is limited. Metabolic syndrome and insulin resistance
alter mitogen-activated protein kinase–induced cell prolifera-
tion, decrease nitric oxide synthesis and adiponectin secretion,
and increase inflammation through enhanced signaling via
receptors for advanced glycation end products (RAGE).
BMPR2 signaling promotes cell migration by a RAGE-
dependent mechanism, and inhibits proliferation through per-
oxisome proliferator–activated receptor (PPAR)-g signaling.
Other metabolic signaling systems are implicated in pulmonary
vascular disease, including L-arginine/polyamine metabolism,
leptin signaling, and serine/threonine kinase pathways including
the mammalian target of rapamycin (mTOR) and phosphoino-
Characterize oxidant signaling. In subcellular compartments of
vascular, progenitor, and stem cells, and in the context of
pulmonary vascular remodeling, elucidating oxidant signaling
pathways and regulation is critical for defining mechanisms.
Understand cellular bioenergetics. Mitochondria regulate cel-
lular bioenergetics, NAD(P)H redox, stress signaling, calcium,
and ROS generation. Alterations in mitochondrial biosynthesis,
autophagy, and fission/fusion affect cellular behavior. Changes
in glucose utilization (e.g., the ‘‘Warburg effect’’) may contrib-
ute to pulmonary vascular cell proliferation.
Explore BMPR2 signaling and identify factors that synergize
with BMPR2 mutations. The mechanisms by which BMP signals
regulate cell proliferation remain elusive, and the contributions
of PPAR-g, RAGE, and their interactions with b-catenin to
elicit lung vascular disease should be explored.
Advance basic understanding of estrogen metabolism, L-arginine/
nitric oxide, polyamine signaling, mTOR, and cell–matrix signal-
ing. These biologic processes have strong associations with
enhancing the incidence or severity of lung vascular disease.
The arena of cell–extracellular matrix interactions remains
underdeveloped in pulmonary vascular pathobiology, and yet
these features are fundamental in controlling cell behavior and
vascular stiffness. Collaborations with experts in bioengineering
who investigate the regulation of matrix assembly would
enhance studies in this area.
Integrate metabolic syndrome research. Hyperinsulinemia,
decreased adiponectin, altered leptin signaling, inflammation,
and other manifestations of metabolic syndrome appear to
accelerate lung vascular disease (22, 23). Research enhancing
understanding of the relationships between global metabolic
dysfunction and lung circulatory disease should be continued.
Endothelial cells lining the pulmonary vasculature display great
heterogeneity with respect to cell surface antigen expression,
metabolic and physiologic activity, barrier properties, morphol-
ogy, and proliferative potential (24–27). Circulating red blood
cells can modulate NO signaling in the lung vasculature, by
viscosity and shear-mediated mechanotransduction of endothe-
lial NO synthase activation, by hemoglobin-dependent NO
scavenging, and by production of vasodilatory mediators such
as nitrite and ATP. Red cell hemolysis releases vasoconstrictive
factors such as hemoglobin and arginase-1 that produce endo-
thelial dysfunction (28). It is increasingly apparent that circu-
lating ‘‘endocrine’’ vasodilatory mediators in blood such as
nitrite, derived from the diet or endothelial NO synthase, can
be delivered via the bloodstream and converted to NO to mod-
ulate pulmonary endothelial responses to hypoxia (29, 30).
Likewise, pulmonary endothelial cells release metabolic and
endocrine factors that stimulate the growth and differentiation
1556AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE VOL 1822010
of epithelial cells (31), demonstrating that the lung endothelium
is integrating information locally and from the systemic circu-
lation to alter lung function.
Cell-derived vesicles are heterogeneous particles containing
cell membrane proteins, metabolites, DNA, and RNA (in-
cluding mRNA and microRNA) from numerous cell types
within the circulation (32). Release of vesicles into the circula-
tion occurs on cell stress or injury or in response to a host of
diseases (33, 34). Vascular endothelium responds to circulating
vesicles by changing its gene expression profile and function
(35). Circulating vesicles may play roles in tissue and cell repair
and regeneration or may contribute to organ damage.
The relationship between resident lung stem cells and
circulating cells, and the paracrine signaling effects they pro-
duce to participate in vascular repair and lung regeneration,
remain unknown. Circulating proangiogenic cells that are de-
rived from the hematopoietic system have also been identified
and used as biomarkers of lung injury; however, only resident or
the rare circulating endothelial cells are able to form vessels
in vivo (36, 37). Pulmonary vascular endothelium possesses
proliferative potential (38), but endothelial stem cells capable of
repopulating vessels within the lung have been recognized only
more recently. There is a need to improve our understanding of
the functional heterogeneity of vascular cells in different
segments of the lung vascular beds, using high-throughput
approaches, including large-scale proteomics and phage display
(39). The systemic bronchial vascular endothelium may have
greater proliferative capacity than the pulmonary vascular
endothelium, but factors influencing this are unknown. Mice
possess lung cells that can be isolated and enriched for lung
vascular repopulating cells in older, lethally irradiated congenic
recipients. Rare, stemlike cells engraft and proliferate as
colonies within the recipient vasculature. Once lung stem cell–
derived vessels are functional they appear to enhance the
engraftment of transplanted pulmonary epithelial cells.
Understanding dynamic remodeling (i.e., growth and in-
volution) of the lung circulation impacts on regenerative
therapies aimed not only at pulmonary vascular diseases, but
other lung diseases, including interstitial lung diseases (40) and
emphysema (41). Another area of emerging understanding
includes the critical contributions of the immune system in
terms of immune surveillance of the vascular milieu.
Explore lung vascular regeneration potential. Opportunities exist
to define whether the lung harbors cells that repair or re-
generate endothelium and to determine where they reside, how
they can be isolated, what homing molecules they express, and
whether there are specific niches into which they engraft.
Studying how circulating bone marrow–derived proangiogenic
cells amplify or remodel the lung vasculature should be a re-
Advance cell-derived vesicle research. There is a need to
develop tools that specifically identify, quantify, and analyze
the molecular composition of circulating cell–derived vesicles
and to correlate their number and function with lung vascular
health and disease in animal models of human cardiopulmonary
diseases and human subjects.
Construct model systems. There is a lack of model systems
for understanding the function of the pulmonary endothelium
as a dynamic system, which integrates circulating cellular and
molecular input from all types of circulating elements (e.g.,
normal and diseased erythrocytes, erythrocyte products, plate-
lets and platelet products, leukocytes and leukocyte products,
Vascular Cross-talk between Pulmonary
and Systemic Circulations
Whereas the uniqueness of the pulmonary circulation proper
rests with its hypoxic vasoconstriction physiological response,
we know little of lung vasculature involvement in integrating
overall vascular health and disease development. The complex-
ity of overall lung circulatory biology is enhanced because of the
potential for differential physiological and pathophysiological
roles of lung vascular components, that is, pulmonary veins,
bronchial circulation, and lung lymphatics. Concepts derived
from studies in the systemic circulation have highlighted several
potential areas of interest in the overall lung circulation. The
use of angiogenesis inhibitors, particularly of vascular endothe-
lial growth factor (VEGF) signaling, has underscored the dy-
namic nature of vascular regression and regrowth; in fact, the
basement membrane left behind by the regressing vasculature
provides ‘‘tracks’’ for the regrowth of blood vessels (42). The
tumor environment is conducive to vascular regeneration as it is
rich in proangiogenic factors (43), but antiangiogenic ap-
proaches collaterally damage circulatory beds that rely on
growth factor signaling, such as the lung.
Systemic vascular beds and the pulmonary circulation do
interact, perhaps best exemplified by pulmonary hypertension
due to liver cirrhosis and hepatopulmonary syndrome (44).
Some form of pulmonary vasodilation is present in 60% of
cirrhotic patients, with 30% having gas exchange abnormalities.
Pulmonary hypertension is seen in about 6% of all cirrhotic
patients. Investigations into the pathogenesis of experimental
hepatopulmonary syndrome based on bile duct ligation have
uncovered an increased interaction of circulating monocytes
and the pulmonary circulation, leading to the production of
mediators such as nitric oxide and carbon monoxide (45). These
alterations are accompanied by increased alveolar capillary
density and correlate with increased expression of VEGF and
VEGF receptor-2. Furthermore, renal–lung interactions have
been found in models of acute renal injury, leading to perme-
ability changes in the lung (46).
Advances in live optical imaging, when combined with
genetic interventions, provide a powerful approach for studying
key signaling events in the systemic and pulmonary circulation
(47). These approaches have the added advantage of allowing
for cellular responses in the multicellular context of the intact
lung. For example, real-time assessment of neutrophil migration
through capillaries can be visualized concomitantly with cellular
signaling events, including calcium fluxes and ROS generation.
The incorporation of these tools for research and eventually for
diagnosis, which are well developed in studies of the systemic
circulation and tumor vascular biology, is critical for the future
studies in lung circulation.
Develop imaging technology for the pulmonary circulation. De-
veloping live molecular and structural imaging will offer insight
into novel molecular markers and molecular pathways involved
in the control of the pulmonary (arterial and venous), bronchial,
and lymphatic circulations. Visualizing real-time cell–cell com-
munications in the lung will be possible with nanotechnology, as
will detecting altered metabolic signaling. Imaging efforts need
a strong training component in multidisciplinary approaches
that leverage expertise in chemistry, physics, experimentation,
and clinical problems, among others. Fostering programs be-
tween academia and industry would be desirable, as would
enhancing access to shared imaging centers. The creation of
core facilities run by imaging scientists and equipped with high
NHLBI Workshop 1557
field strength magnetic resonance imaging (MRI), micro-PET/
SPECT/CT (positron emission tomography/single-photon emis-
sion computed tomography/computed tomography), high-
frequency Doppler imaging, and advanced optical imaging
should be encouraged at national centers of excellence in
cardiopulmonary research. Improving imaging will lead to
improved early disease detection.
Explore the relationships between systemic vasculature and
pulmonary vascular function. Abnormalities in systemic vascu-
lar reactivity and function that occur in relation to pulmonary
vascular disease may reveal a new understanding of pulmonary
vascular pathophysiology. There is a need to understand why
a genetic or environmental insult results in vascular disease in
the lung, rather than in other organs.
The Lung Vascular–Cardiac Axis
It has become apparent that the pulmonary circulation is
intimately coupled to right ventricular health and disease.
Severe forms of PAH (including idiopathic forms) continue to
be treated with a single vasodilator agent or a combination of
vasodilator drugs (48). After more than a decade of clinical
experience with this approach it is clear that in too many
instances a significant and lasting reduction of the right ven-
tricular afterload cannot be achieved, and patients with PAH
die of right heart failure (49). Prevention of the development of
right ventricular failure (RVF) independent of attempts to
reduce the RV afterload has not been a treatment goal. There
is lack of robust and validated diagnostic criteria that describe
early phases of RV dysfunction (50) No detailed knowledge
base exists regarding the transition from RV hypertrophy
(RVH) to RVF in the setting of the remodeled lung circulation
in PAH (51). However, acquisition of this knowledge is critical
given the observation that RV function can fully recover within
weeks of lung transplantation in patients with end-stage PAH.
How the failing RV returns to normal function after lung
transplantation is unknown.
Our concepts of RVF mechanisms have been shaped largely
by investigations of left ventricular failure, even though there is
evidence that the right and left ventricles differ in responses to
increased afterload. For example, right ventricular systolic
pressure undergoes a four- to fivefold increase above normal
during the development of severe pulmonary hypertension
whereas the left ventricular systolic pressure in the setting of
aortic stenosis undergoes a small percent change only. In
addition, it is known that a1-adrenergic agonists increase the
contractile force of the left ventricle, whereas they cause a force
reduction in the corresponding normal RV (52), and long-term
infusion of norepinephrine leads to left ventricle hypertrophy
whereas the RV does not undergo hypertrophy (53). Other
differences between right and left ventricular biology are being
discovered, including developmental programs and resident
stem cell populations.
Validate diagnostic criteria of RV dysfunction. Candidate non-
invasive (echocardiographic) variables include tricuspid valve
annular plane systolic excursion, RV fractional shortening (54,
55), and isovolumetric acceleration. Cardiac MRI has become
the reference standard modality for evaluation of cardiac
anatomy, function, and remodeling. New imaging markers for
afterload need to be further explored, including main pulmo-
nary artery mean flow using phase-contrast MRI. The role of
myocardial perfusion reserve in RV dysfunction is unknown
and should be explored. Candidate MRI variables include RV
volumes, RV wall strain, and RV perfusion. Three-dimensional
echocardiography of the RV could substitute for MRI when
device contraindications exist or could complement MRI.
Improve understanding of RVH and RVF development. Key
areas to address include the following: the role of the adrenergic
receptor system in RVF; an understanding of whether RVH in
PAH is an adaptive compensatory mechanism similar to left
ventricular hypertrophy in the athlete; identification of the
processes that lead to adaptive and ‘‘functional’’ RVH; identi-
fication of mechanisms of the transition from RVH to RVF;
advancements in understanding the metabolic changes charac-
teristic of RVH and RVF; investigating whether RVF is a form
of myocardial hibernation; and the role of phosphodiesterase
inhibitors in RVH and/or RVF.
Develop imaging techniques for assessing RV remodeling. A
switch to glycolysis (from fatty acid oxidation) reflects cardiac
hypertrophy and indicates hyperpolarized mitochondria in RV
remodeling. Glucose uptake as indicated by the uptake value of
fluorodeoxyglucose by PET may correlate with vascular remod-
eling and RV function in PAH. The identification of RV
dysfunction biomarkers and/or strain would complement imag-
Discover and design directed therapies to prevent (and reverse)
RVF. Model animal studies are needed to explore cellular and
molecular mechanisms of RVF (56, 57). Potential targets for
study include neurohormonal activation and mechanisms for
preventing RV capillary loss, restoring blood flow, and de-
creasing fibrosis to improve energy utilization. Trials need end
points reflective of the treatment of RV dysfunction and failure.
Assessment of the heart directly by endomyocardial biopsy
(genomic, proteomic analysis) must also be considered.
Advance collective organization of research efforts. A con-
ceptual approach that integrates cardiac and pulmonary vascu-
lar evaluations should be advanced, including left ventricular
function knowledge. Types of studies might include evaluation
of the transcriptomes and proteomes from the right and left
ventricles and determination of how the left ventricle is affected
by ventricular interdependence in the setting of PAH and RVF.
Discovery of Novel PAH Treatments
Although a minority (,15%) of patients with severe PAH
respond significantly to acute pulmonary vasodilators and can
be treated successfully with calcium channel blockers, most are
not responsive to vasodilators and are currently treated with
prostacyclin analogs, endothelin-1 receptor blockers, type 5
phosphodiesterase inhibitors, or various combinations of these
agents (58). These treatments provide some improvement in the
quality of life of patients, but there is no convincing evidence
that they significantly prolong survival (59). Overall, despite the
use of many expensive drugs, PAH remains a debilitating and
deadly disease and more effective therapies are urgently
needed. The pathogenesis of PAH is generally ascribed to
vasoconstriction, vascular wall remodeling, and in situ throm-
bosis. It is also generally believed that whereas vasoconstriction
may be important in the early stages, the major factor re-
sponsible for the high pulmonary vascular resistance in severe,
established PAH is the formation of occlusive neointimal and
plexiform lesions in small, peripheral pulmonary arteries. It is
likely that these hypercellular and/or fibrotic lesions will have to
be ‘‘dissolved’’ or bypassed by new vessel growth to effectively
reverse the high resistance and pressure of PAH. This presents
a formidable challenge, because we do not yet understand
exactly what causes the formation of these vascular lesions or
the cellular and molecular mechanisms involved.
1558 AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINEVOL 1822010
Advance pharmacogenomic approaches. Pharmacogenomic ap-
proaches (60) are now feasible to identify the roles of gene
polymorphisms in determining the differences among patients
with PAH and the predicted efficacy and/or toxicity of therapy.
This includes considering both vascular-directed and right
ventricular–directed treatments, thereby offering personalized
therapy for PAH based on identification of individuals likely to
receive the most benefit at least risk.
Improve drug delivery. Homing peptides (61) to the pulmo-
nary vascular bed should be evaluated to optimize the selective
delivery of drugs to specific vascular segments and cells.
Develop methods to identify regression of vascular lesions.
Tracking both the formation and dissolution of occlusive pulmo-
nary vascular lesions may be accomplished via high-resolution
angiographic or nuclear imaging using radioisotope-labeled par-
ticulates or biologics that specifically target vessel legions.
Improve animal models of pulmonary vascular disease. Ani-
mal models that closely mimic the hemodynamic pathophysiology
and occlusive neointimal and plexiform pulmonary arteriopathy
of human PAH will be essential for more rigorous preclinical
testing of new therapies (62).
Improving PAH Care through Human Subject Studies
Clinical research efforts in lung vascular disease have focused
on PAH. The management of PAH has advanced since the
publication of the NIH-supported 1980s registry, which estab-
lished a prognostic benchmark for survival that is still in use
today (63, 64). The French Network on Pulmonary Hyperten-
sion has investigated contemporary survival during a 3-year
study of adult patients with idiopathic, familial, or anorexigen-
associated PAH. Using the NIH model, survival in incident
cases has improved by only about 10–15%. Higher mortality
was closely associated with male sex, right ventricular function,
and exercise limitation. Nevertheless, the long-term manage-
ment of patients with PAH beyond the initiation of drug
therapy is poorly studied and understood (65, 66). A pro-
spective study of epidemiological risk for PAH has not been
performed. Such studies would require a large cohort for
informative analysis. Understanding the mechanisms of human
pulmonary vascular disease will require efforts similar to those
made in more common cardiovascular diseases, that is, large,
multicenter studies. Indeed, pulmonary hypertension studies
should be considered as a component of national studies such as
MESA (Multi-Ethnic Study of Atherosclerosis) (67) whenever
possible. Most simple and important questions, such as the
value of anticoagulation or of introducing aspirin or b blockade,
have not been systematically addressed.
The design of future pulmonary hypertension clinical studies
must include improved clinical measurements, the marriage of
basic scientific aims to clinical trials (68), the development of
surrogate survival end points, the development of large data-
bases, standardized methods of precise phenotyping across
methods for sample collection and storage, and complete data
collection with open access (69, 70).
Identify new clinical studies in PAH. The efficacy of long-term
therapy should be addressed, including the systematic evalua-
tion of therapies bearing low risk and low cost that show
substantial impact in systemic vascular diseases (e.g., warfarin,
exercise, and antiplatelet therapy). Routine pulmonary arterial
‘‘stiffness’’ measurements are possible for assessing the pulmo-
nary circulation (71–74) and validated measures of vascular
stiffness and ventricular–vascular coupling should be incorpo-
rated into clinical trials.
Implement an appropriate research support structure. A con-
sortium of research centers should serve to form a modern
translational and clinical research support platform. A key
function of a consortium would be to perform phenotyping.
Associations with pharmaceutical clinical trials could be lever-
aged for simultaneous cost-effective collection of data and
biobanked materials for use in common research. Basic ques-
tions of risk and etiology in PAH must be addressed by
a multicenter, prospective study of a large number of carefully
Enhance training of lung vascular investigators. Training
components supported by a consortium or other mechanisms
are necessary to ensure that the next generation of lung vascular
scientists is equipped to move forward.
Summary of Recommendations to the Institute
To be used for planning and prioritization in concert with the
NHLBI mission, formal recommendations from this workshop
are summarized as follows:
d Advance basic scientific research in lung vascular biology,
utilizing emerging technologies.
d Advance and coordinate basic and clinical knowledge of
the pulmonary circulation–right heart axis through novel
research efforts, utilizing multidisciplinary teams.
d Define interactions between lung vascular components
and circulating elements and systemic circulations by
fostering novel collaborations.
d Encourage systems biology analysis to understand and
define interactions between lung vascular genetics, epige-
netics, metabolic pathways, and molecular signaling.
d Develop strategies using appropriate animal models to
improve the understanding of the lung vasculature in
health and in conditions that reflect human disease.
d Enhance translational research in lung vascular disease by
comparing cellular and tissue abnormalities identified in
animal models with those in human specimens.
d Improve lung vascular disease molecular and clinical
d Develop in vivo imaging techniques that assess structural
changes in lung vasculature, metabolic shifts, functional
cell responses, and right ventricular function.
d Develop research consortia that advance basic, transla-
tional, and clinical studies; allow for multicenter epidemi-
ological study feasibility; and support training of junior
investigators in lung vascular biology and disease.
Author Disclosure: S.E. received more than $100,001 from Asthmatx as an
investigator industry-sponsored grant. SIR received more than $100,001 from
the NHLBI in sponsored grants and up to $1,000 from the NHLBI in consultancy
fees as a study section member. T.S. does not have a financial relationship with
a commercial entity that has an interest in the subject of this manuscript. M.A.
received more than $100,001 from the NIH/NHLBI and more than $100,001
from the AHA in sponsored grants. J.A. does not have a financial relationship with
a commercial entity that has an interest in the subject of this manuscript. S.L.A.
holds patents related to the use of PDK inhibitors to treat cancer, but these have
not been commercialized. K.A. does not have a financial relationship with
a commercial entity that has an interest in the subject of this manuscript.
R.S.B. does not have a financial relationship with a commercial entity that has an
interest in the subject of this manuscript. N.B. received $50,001–$100,000 from
Gilead in industry-sponsored grants for the Research Scholars Program, and
$10,001–$50,000 from the Parker B. Francis Foundation as a fellowship and
$50,001–$100,000 from the American Heart Association as a beginning grant-in-
aid. J.B. received up to $1,000 from Chromocell Corporation in consultancy fees
and more than $100,001 from the NIH in RO1, RC1 grants. H.B. does not have
a financial relationship with a commercial entity that has an interest in the subject
of this manuscript. G.C. received $50,001–$100,000 from Actelion Pharmaceu-
ticals in industry-sponsored grants as the Entelligence Young Investigator Award-
2008 and is an employee of the Department of Veteran Affairs. G.W.D. does not
have a financial relationship with a commercial entity that has an interest in the
subject of this manuscript. R.D. received more than $100,001 from Actelion,
more than $100,001 from Gilead, and more than $100,001 from Novartis in
industry-sponsored grants, and more than $100,001 from the NIH and more
than $100,001 from the State of Ohio in sponsored grants. K.F. received up to
$1,000 from Cytoskeleton for a phone consult concerning a research compound,
$1,001–$5,000 from Pfizer for serving as a research committee member, and
$10,001–$50,000 from Gilead for serving on a research committee (twice) and
as an advisory board panelist, $5,010–$10,000 from Gilead in promotional
lecture fees, and $1,001–$5,000 from ABComm and $1,001–$5,000 from Simply
Speaking for CME lecture fees, $50,001–$100,000 from Actelion and $50,001–
$100,000 from Gilead in institutional grants, up to $1,000 from Up-to-Date in
royalties as a chapter author, and $50,001–$100,000 from the NIH (RO1s) and
$50,001–$100,000 from the AHA (EIA) in sponsored grants, and up to $1,000
from the PHA in advisory board fees for serving as a journal writer and editor.
M.F. does not have a financial relationship with a commercial entity that has an
interest in the subject of this manuscript. T.F. does not have a financial relation-
ship with a commercial entity that has an interest in the subject of this
manuscript. M.G. received $1,001–$5,000 from Mindstar-Medical-Bayer for
serving on the Bayer Riociguat Pulm Clin Advisory Board; M.G.’s institution
received more than $100,001 from the NIH in sponsored grants. M.T.G. received
$50,001–$100,000 from the Collaborative Research and Development Agree-
ment between the U.S. government and INO Therapeutics in industry-sponsored
grants and holds a patent from the U.S. government as a coinventor for use of
nitrite salts for cardiovascular indications. P.M.H. received $1,001–$5,000 from
Novartis for serving on an advisory board, $1,001–$5,000 from Abcomm in
lecture fees for Medical Grand Rounds, $50,001–$100,000 from Actelion/UT in
industry-sponsored grants for the PAH registry (REVEAL), and more than
$100,001 from the NIH/NHLBI in sponsored grants for the Specialized Center
for Clinically Oriented Research (SCCOR). M.H. received $5,001–$10,000 from
Actelion and $1,001–$5,000 from Novartis in consultancy fees, $5,001–$10,000
from Actelion, and $1,001–$5,000 from Novartis in advisory board fees, and
$1,001–$5,000 from Actelion, $1,001–$5,000 from Bayer Schering, $1,001–
$5,000 from GlaxoSmithKline, $1,001–$5,000 from Pfizer, and $1,001–$5,000
from United Therapeutics in lecture fees. N.K. has received consultancy fees from
Stromedix and Genentech (each $1,001–$5,000); he has received industry-
sponsored grants from Biogen Idec and Centocor (each more than $100,000); he
holds three patents along with the University of Pittsburgh (related to use of
microRNAs in treatment and diagnosis of IPF, peripheral blood biomarkers in IPF,
and urinary biomarkers in IPF); he holds sponsored grants from the NIH (over
$100,000). S.K. has received consultancy fees from Gilead and Novartis (each
$1,001–$5,000); he has received advisory board fees from Bayer and
Gilead (each $1,001–$5,000); he has received steering committee fees
from Gilead ($10,001–$50,000); he has received grant review committee fees
from Gilead ($10,001–$50,000) and Pfizer ($5,001–$10,000); he has received
lecture fees from Gilead ($1,001–$5,000) and Actelion ($1,001–$5,000); he has
received industry-sponsored grants from Actelion, Gilead, United Therapeutics,
Lung Rx, and Pfizer (each $10,001–$50,000); he has received fees from Pfizer as a
collaborator on an institutional grant (F) ($50,001–$100,000), from Merck for
a drug study for an NIH-funded grant (F) ($10,001–$50,000), and from Bayer for
a drug study for an NIH-funded grant (F) ($5001–$10,000); he has received
sponsored grants from the NIH (more than $100,000); he has received advisory
board fees from the American Lung Association ($1,001–$5,000); he has
received advisory board fees from the NIH (up to $1000). J.L. does not have
a financial relationship with a commercial entity that has an interest in the subject
of this manuscript. D.M.M. has received industry-sponsored grants from Med-
Immune (more than $100,000). I.F.M. has received consultancy fees from
Cytokinetics (up to $1,000); he has received sponsored grants from the American
Heart Association ($10,001–$50,000). J.N. does not have a financial relationship
with a commercial entity that has an interest in the subject of this manuscript.
M.N. has received sponsored grants from the NIH (more than $100,000). M.R.
does not have a financial relationship with a commercial entity that has an
interest in the subject of this manuscript. J.S. has received consultancy fees from
Stem Cells, Inc. ($1,001–$5,000); she has received sponsored grants from the
NIH, CIRM, and Council for Tobacco Research (each more than $100,000). M.O.
does not have a financial relationship with a commercial entity that has an
interest in the subject of this manuscript. P.P. does not have a financial relation-
ship with a commercial entity that has an interest in the subject of this
manuscript. D.R. is employed by Novartis Institutes for BM Res; he holds patents
along with Novartis AG; he holds restricted stock grants from Novartis AG (more
than $100,000). P.T.S. has received sponsored grants from the NIH (more than
$100,000), Chicago Biomed Consort (more than $100,000), American Academy
of Pediatricians ($10,001–$50,000), and American Heart Association ($50,001–
$100,000). K.S. has received sponsored grants from Pfizer (more than $100,000)
and the NHLBI/NIH (more than $100,000). R.M.T. has received consultancy fees
from Novartis (up to $1,000); he has received sponsored grants from the NIH
(more than $100,000). N.V. has received consultancy fees from Bayer-Schering
and Pfizer (each $1,001–$5,000). E.S. is employed by United Therapeutics
Corporation; he has applied for a patent along with United Therapeutics
Corporation; he holds stock in United Therapeutics Corporation (more than
$100,000). R.W. has received royalties from Laboratory Corporation of America
and Ricerca Biosciences LLC (up to $1,000). M.C.Y. does not have a financial
relationship with a commercial entity that has an interest in the subject of this
manuscript. Y.Z. does not have a financial relationship with a commercial entity
that has an interest in the subject of this manuscript. D.B.G. is a full-time
employee of the NIH. T.M.M. has received sponsored grants from the American
Heart Association ($50,001–$100,000) and the Parker B. Francis Foundation
Acknowledgment: Additional participants included Dr. James Kiley (NHLBI), Dr.
Gail Weinmann (NHLBI), Dr. Andrea Harabin (NHLBI), Dr. Weinu Gan (NHLBI),
and Dr. Carol Blaisdell (NHLBI).
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