Circulating
endothelial
progenitor
cells
may
be
important
in
the
pathogenesis
of
idiopathic
pulmonary
arterial
hypertension
(IPAH)
and
give
rise
to
endothelial
colony-­‐forming
cells
(ECFCs)
in
culture.
These
cells
represent
an
accessible
surrogate
population
to
investigate
endothelial
dysfunction
in
IPAH.
Peripheral
blood
mononuclear
cells
were
cultured
from
healthy
volunteers
(n=25,
72%
female;
age
range
23-­‐57
yr)
and
IPAH
patients
(n=30,
60%
female;
age
range
22-­‐56
yr).
Older
IPAH
patients
(n=6,
50%
female;
age
range
62-­‐82
yr)
were
also
sampled.
Distinct
colonies
appeared
after
13-­‐35
days
and
exhibited
a
typical
cobblestone
morphology.
The
average
frequency
of
colonies
and
clonal
growth
of
isolated
cells
was
similar
in
healthy
volunteers
and
IPAH
patients.
Age-­‐dependent
differences
were
observed
however
in
the
number
and
frequency
of
colonies,
which
declines
with
age
in
the
control
but
not
in
IPAH
subjects.
The
endothelial
phenotype
was
confirmed
by
immunostaining
and
flow
cytometry,
exhibiting
endothelial
and
progenitor
markers,
but
not
hematopoietic
markers.
Endothelial
cell
functions,
including
proliferation,
angiogenesis,
migration
and
responses
to
apoptotic
stimuli,
were
compared
in
cells
between
passages
4
to
7.
IPAH
cells
showed
enhanced
angiogenic
capacity
(tube
formation
on
Matrigel),
significantly
less
apoptosis
(lower
caspase-­‐3/7
activity)
in
response
to
serum
and
growth
factor
deprivation,
and
impaired
migratory
capacity
compared
with
control
ECFCs.
Dysfunctional
transforming
growth
factor
(TGF)-­‐β
and
bone
morphogenetic
protein
receptor
expression
and
signalling
are
implicated
in
IPAH
and
were
assessed
by
RT-­‐PCR
and
western
blotting.
IPAH
and
control
ECFCs
differed
in
their
TGF-­‐β
type
I
(ALK5)
receptor
expression/signalling
and
in
the
expression
of
other
regulatory
proteins
(e.g.
chloride-­‐like
intracellular
channel-­‐4).
Blood-­‐derived
ECFCs
display
an
endothelial
lineage
similar
to
that
of
mature
endothelial
cells.
ECFCs
from
IPAH
patients
have
a
distinct
functional
phenotype
and
exhibit
differences
in
TGF-­‐β
receptor
superfamily
expression/signalling,
which
may
contribute
to
endothelial
dysfunction
and
vascular
remodelling
in
IPAH.