Transcript A Personal View of the Etiology of Preeclampsia

The Etiology of
Preeclampsia
9 June 2009
Presented by Damon T. Cudihy, MD
Mentor: Richard Lee, M.D.
Goals of Project
To survey and review recent literature
proposing evidence for theories of
pathogenesis of preeclampsia
2. To distinguish true causes of preeclampsia as
opposed to mere bio-indices and
epiphenomena
3. Regarding the etiology of preeclampsia, to
1.
provide a biologically plausible theory
that unifies the essential and validated
findings of past and current scientific
investigation.
Questions to answer
1.
2.
3.
What do we know about the burden of
pre-eclampsia so far?
Do we know enough to understand the
cause of pre-eclampsia?
With a better understanding of the cause
of pre-eclampsia could we begin to
prevent the disease and develop better
treatments that will minimize the
associated morbidity and mortality ?
Background

Diagnosis
– Hypertension: SBP≥140 or DBP≥90
– Proteinuria: ≥0.1g/L (2+) in ≥2 random urine
samples ≥4hrs apart; or ≥0.3g in 24hrs

Disease burden
– Affects 3-14% of all pregnancies worldwide
(5-8% of pregnancies in the U.S.)

Effect on mother and child
– Leading cause of worldwide pregnancy-related
maternal and neonatal mortality and morbidity
Spectrum of Preeclampsia
Conception
Failed implantation
Early Placental
Vascular dificiency
Late Placental
Dysfunction
Spontaneous abortion
Early onset
Preeclampsia
Preeclampsia
Risk Factors for Preeclampsia









Nulliparity
Primipaternity
Personal or family history
(37% in sisters)
Twin gestation (20, 70%)
Molar pregnancy (70%)
Maternal infection
Chronic Hypertension
Renal Disease
Diabetes (50%)




Androgen excess
Obesity/Insulin
Resistance
Dyslipidemia
Thrombophilias
(Antiphospholipid, Protein C/S

deficiency,AntithromMbin
deficiency, Factor V Leiden,
MTHFR)
Condom use
Donor sperm fertilization

Non-smoking

Pre-eclampsia as a risk factor:
Cardiovascular disease
 Renal disease
 Insulin resistance

Current Theories Associated with
Etiology of Preeclampsia
Immunologic phenomena
 Abnormal trophoblastic invasion
 Vascular endothelial damage
 Cardiovascular maladaptation
 Inflammation and oxidative stress
 Genetic predisposition
 Coagulation abnormalities
 Dietary deficiencies or excesses

Model of Contributing Factors
Preeclampsia
Maternal factors
Genetic
Acquired
Paternal factors
Gestational factors
Genetic
Acquired
Key Principles

“Disease of first pregnancy”
– 3-7% in nulliparas, 1-5% in multiparas
– Primipaternity model

Placental load association
– Increased incidence and severity in multiple
gestations and molar gestation

Global Endothelial dysfunction
Biomarkers for prediciton and
detection of Preeclampsia
the focus of most U.S. studies in past 2
years
 demonstrate preeclampsia as an
antiangiogenic state resulting from overproduction of antiangiogenic factors

Soluble fms-like tyrosine kinase 1
(sFlt-1) and Soluble Endoglin

Circulating placental proteins
– Inhibit angiogenesis and arteriolar
vasodilation
Excessive amounts may lead to systemic
endothelial dysfunction causing
preeclampsia
 screening test for preeclampsia?

--MAYNARD, SHARON E.; et al. Soluble Fms-like Tyrosine Kinase 1 and Endothelial Dysfunction in the
Pathogenesis of Preeclampsia. Pediatric Research. Review Issue. 57(5 Part 2):1R-7R, May 2005.
--Levine, Richard J.;et al. for the CPEP Study Group Soluble Endoglin and Other Circulating Antiangiogenic
Factors in Preeclampsia. Obstetrical & Gynecological Survey. 62(2):82-83, February 2007.
Pathophysiology of preeclampsia and resulting symptoms; EDFMD,
endothelium-dependent flow-mediated vasodilation.
From: WEISSGERBER: Med Sci Sports Exerc, Volume 36(12).December 2004.2024-2031
Clinical manifestations of
pre-eclampsia

All result from endothelial dysfunction at
the various end organs in the body:
– Systemic Arterial vasculature HTN, edema
– Central Nervous System headache, visual
changes, seizure
– Hepatic system RUQ pain, HELLP
– Renal system proteinuria, renal failure
– Placental system IUGR, oligohyrdramnios,
abruption
Risk factors for pre-eclampsia
A loosely defined grouping
1.
2.
3.
Genetically inherited susceptibilities
(maternal and paternal side)
Conditions with known associations with
endothelial dysfunction
States affecting the immune-modulated
placental cytotrophoblastic cell invasion
of maternal spiral artery endothelium
1. Genetically Inherited Factors
Both men and women who themselves were the
born of a pregnancy complicated by preeclampsia are significantly more likely to be
parents of a child with pre-eclampsia
 Baseline “fitness” of maternal endothelial
function
 Maternal immune system function
 Particular genotype combinations between
mother and child (or mother and father)
associated with preeclampsia

2. Endothelial Dysfunction
All clinical manifestations can be explained by
endothelial dysfunction
 Most risk factors associated with endothelial
dysfunction

– all chronic disease risk before and after preeclampsia
– role of infection, diet, exercise, and oxidative stress

Pregnancy and preeclampsia as a physiologic
endothelial stress test
3. Immune-mediated invasion
and angiogenesis
Accounts for remaining risk factors:
nulliparity, primipaternity, condom use,
IVF, twins, moles, and non-smoking
 Maternal immune system facilitates
invasion of fetal extravillous cytophoblastic
cells into the myometrium and arteriolar
endothelium
 Accounts latest findings of anti-angiogenic
factors associated with preeclampsia

Grouping of Risk Factors
for Preeclampsia
1.
Genetic
–
2.
Personal or family history
(37% in sisters)
Endothelial dysfunction
–
–
–
–
–
–
–
–
Maternal infection
Chronic Hypertension
Renal Disease
Diabetes (50%)
Androgen excess
Obesity/Insulin
Resistance
Dyslipidemia
Thrombophilias
3.
Immune-mediated
invasion
and angiogenesis
–
–
–
–
–
–
–
Nulliparity
Primipaternity
Twin gestation (20, 70%)
Molar pregnancy (70%)
Condom use
Donor sperm fertilization
Non-smoking
Pathophysiology of Preeclampsia

2 Stage process
1. Preclinical (≤20 weeks):
– inadequate invasion of maternal spiral arterioles
by fetal cytotrophoblasts insufficient maternal
vascular remodeling and angiogenesis
2. Clinical (normally >20 weeks):
– Oxidatively stressed/hypoxic placenta
 generalized systemic inflammatory response
with release of anti-angiogenic factors,
inflammatory cytokines, and trophoblast debris
 maternal syndrome
Natural Killer Cells:
Friend or Foe?



Named for their cytotoxic action against virusinfected and tumor-transformed cells
Paradoxically, NK cells play a key role in
facilitating and stimulating the invasion of
tumor-like fetal trophoblastic cells into the
maternal vasculature.
The dysfunction/dysregulation of decidual NK
cells recocile the two leading theories:
1. Immune maladaptation
2. Insufficient invasion of the maternal spiral arteries
by fetal trophoblasts
Diagram of basic maternal and
placental vasculature
Normal vs Abnormal Vascular
Remodeling of Spiral Arteries
Future Directions
Further clarification of the physiologic vs. pathologic
interactions between maternal decidual NK cells and
fetal extravillous trophoblasts
 Identification of genes involved with immune
maladaptation
 Biomarkers as screening tools to target interventions to
reduce risk
 Tx’s designed to boost extravillous trophoblastic invasion
targeted to high risk women?
 Pharmacologic manipulation of NK cells to direct them in
the pro-angiogenic pathway?

Conclusion
1.
2.
3.
Early maternal-fetal interface involving
decidual/uterine NK cells and extravillous
trophoblasts
Healthy pregnancy requires NK cell stimulation of
vascular invasion by fetal trophoblasts
(an immune-mediated process)
Inadequate vascular invasion by fetal cells leads to
placental hypoxiaoxidative stressmaternal
endothelial dysfunctionclinical signs and
symptoms of pre-eclampsia
“Therefore, one may state at least
tentatively, that future collaboration
between the obstetrician and
immunologist should produce the needed
diagnostic and therapeutic tools to place
preeclampsia together with Rh
isoimmunization as an interesting, but
eminently treatable immunologic
dysfunction.”
--John Willems. The Etiology of Preeclampsia: A Hypothesis. Obstetrics
and Gynecology, 50 (4), Oct 1977.
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