Congenital: Mechanical Circulatory Support: Basic Science
Prenatal hypoxemia alters microglial morphology in fetal sheep

Read at the 99th Annual Meeting of The American Association for Thoracic Surgery, Toronto, Ontario, Canada, May 4-7, 2019.
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Abstract

Objective

Neuroimmune cells, particularly microglia and astrocytes, play a critical role in neurodevelopment. Neurocognitive delays are common in children with congenital heart disease, but their etiology is poorly understood. Our objective was to determine whether prenatal hypoxemia, at levels common in congenital heart disease, induced neuroimmune activation to better understand the origins of neurobehavioral disorders in congenital heart disease.

Methods

Eight fetal sheep at gestational age 109 ± 3 days (term ∼145 days) were cannulated onto a pumpless extracorporeal oxygenator via the umbilical vessels and supported in a fluid environment for 22 ± 2 days under normoxic (n = 4) or hypoxic (n = 4) conditions. Control fetuses (n = 7) were harvested at gestational age 133 ± 4 days. At necropsy, brains were stained with ionized calcium-binding adaptor molecule 1 and glial fibrillary acidic protein antibodies to quantify microglia and astrocytes, respectively, in gray and white matter in frontotemporal and cerebellar sections. Microglia were classified into 4 morphologic types based on cell shape. Data were analyzed with 1-way analysis of variance or Fisher exact test, as appropriate.

Results

Oxygen delivery was significantly reduced in hypoxic fetuses (15.6 ± 1.8 mL/kg/min vs 24.3 ± 2.3 mL/kg/min; P < .01). Rates of apoptosis were similar in hypoxic, normoxic, and intrauterine control animals in all examined areas. There were also no differences between groups in area occupied by glial fibrillary acidic protein-labeled astrocytes or ionized calcium-binding adaptor molecule 1-labeled microglia in all examined areas. However, round microglia were significantly increased in hypoxic animals compared with normoxic animals (33% vs 6%; P < .01) and control animals (33% vs 11%; P < .01).

Conclusions

Prenatal hypoxemia altered microglial morphology without significant gliosis. Additional studies characterizing these mechanisms may provide insight into the origins of neurobehavioral disabilities in children with congenital heart disease.

Key Words

congenital heart disease
neurodevelopment
microglia

Abbreviations and Acronyms

CHD
congenital heart disease
EXTEND
Extra-uterine Environment for Neonatal Development
GA
gestational age
GFAP
glial fibrillary acidic protein
Iba-1
ionized calcium-binding adaptor molecule 1
ROI
region of interest

Cited by (0)

Supported by The Preclinical Core of the Institutional Intellectual Developmental Disabilities Research Core of the Children's Hospital of Philadelphia (HD26979) as well as the Children's Hospital of Philadelphia Departments of Surgery and Cardiothoracic Surgery and the Mortimer J. Buckley Endowed Chair.