Abstract
Individuals born prematurely are at increased risk for many chronic conditions, and respiratory disease
represents a significant portion of the morbidity and mortality in this population. Better understanding of the
etiology of chronic respiratory disease among those born preterm has the potential to improve diagnosis,
treatment, and prevention. Asthma occurs more frequently and severely among those born preterm. The etiology
of asthma is known to be multifactorial, involving innate inflammatory tendencies, potentiated by prenatal and
early life exposures. Asthma exhibits differences in presentation, and pathophysiology, based on biologic sex, a
phenomenon known as sexual dimorphism.
Epigenetics represents a powerful tool for understanding early-life origins of chronic disease. Research
from our group in the Extremely Low Gestational Age Newborn (ELGAN) cohort has illustrated the critical role of
epigenetic and gene expression changes in the placenta as they relate to later development of a host of chronic
conditions.
As a temporary organ during gestation, the placenta forms a barrier between the developing fetus, the
mother, and by extension, the outside world. It is a critical conduit through which the effects of environmental
exposures are filtered. The placenta also plays critical roles in directing fetal growth and development, and
establishing the neonatal immune system, while also protecting the fetus from rejection by the maternal immune
response. The placenta is also highly sexually dimorphic, responding differently to prenatal exposures, and
conferring risk differently for chronic disease, based on the biologic sex of the infant.
Prior work from other groups has shown epigenetic changes in immune-related genes from cord blood
cells in association with the later development of childhood asthma among children born at term. Preliminary
analyses from EGLAN have shown differential epigenetic changes to immune-related genes in the placenta that
are associated with asthma development in a largely sex-dependent manner. No other published studies have
examined placental epigenetic factors as antecedents of asthma.
We propose to further examine placental epigenetic mechanism and gene expression and their
association with development of asthma at age 10 years. Our study would be the first to provide a comprehensive
examination of epigenetic mechanisms and gene expression in the placenta, as well as epigenetic changes in
neonatal blood on day of life 1 as they relate to later development of asthma among ELGANs. The examination
of the role of differences based on biologic sex is also novel. These investigations will elucidate important general
and sex-specific genetic pathways that form the basis of the developmental origins of asthma. Enhanced
understanding of these will allow for improved diagnosis, treatment, and perhaps even prevention of asthma in
a particularly vulnerable population.