Abstract Body (Do not enter title and authors here): Background
Up to 50% of infants with critical congenital heart disease (CCHD) experience neurodevelopmental delay, potentially due in part to neuroinflammation and iron deficiency. These factors contribute to long-term neurodevelopmental disorders in preterm infants, but it is unclear whether similar mechanisms occur in CCHD and thus represent intervention targets.
To address knowledge gaps about brain inflammation and iron status in CCHD, we developed a novel, non-invasive method to isolate brain-derived exosomes (BDEs) from peripheral blood using contactin-2 (CNTN2), a brain-specific glycoprotein. BDEs cross the blood-brain barrier and carry biomarkers reflecting their origin.

Aim
Determine the feasibility of isolating plasma BDEs and assessing therein markers for neuroinflammation and iron status in infants with CCHD.

Methods
This pilot study included infants ≤6 months old with transposition of the great arteries (TGA) or hypoplastic left heart syndrome (HLHS), using plasma from the Heart Centre Biobank (Toronto). CNTN2+ BDEs were isolated via size exclusion spin columns, enriched by immunoprecipitation, and analyzed for size, concentration, and integrity. BDE contents were assessed with a validated (for clinical use) panel of cytokines, chemokines, iron, and brain biomarkers. Analysis included data visualization and Pearson’s correlation matrix to explore relationships and compare results to published BDE values of healthy newborns from mothers with or without overweight/obesity (OWO).

Results
Infants (n=11; 5 HLHS, 6 TGA) were 55% female and mean age 3.7 months. Compared to healthy newborns (Fig. 1), infants with CCHD had higher ferritin and lower transferrin and S100B. While peripheral CRP (850.16 ± 637.94 ng/mL) was elevated, BDE CRP was lower compared to healthy newborn groups. BDE Ferritin was positively correlated (Fig. 2) with PARK7, a cell metabolism marker, and TfR correlated with S100B (reflects astrocytosis).

Conclusions
Assessing BDE biomarkers in infants with CCHD is feasible. In this small cohort, preliminary results showed that CCHD iron biomarker patterns aligned with those in newborns of mothers with OWO, an inflammatory condition that sequesters iron as ferritin. Further research is warranted to determine if patterns of low BDE CRP (amid systemic inflammation), reduced S100B, and higher BDNF (a nerve growth factor), are replicated in larger CCHD cohorts, and if BDE inflammation and iron biomarkers can indicate neurodevelopmental deficits.