Plasma heparan sulfate structural variation and phenotypic heterogeneity in pediatric Acute Respiratory Distress Syndrome

Endothelial glycocalyx (eGCX) shedding contributes to microvascular endotheliopathy in Acute Respiratory Distress Syndrome (ARDS) and may represent an underrecognized source of phenotypic heterogeneity. We examined whether circulating heparan sulfate (HS) signatures, as readouts of eGCX shedding, capture patterns of inter-patient biological variation distinct from other eGCX components and conventional protein biomarkers, whether specific HS structural features are enriched, and whether these signatures are associated with heparanase-1 (HPSE) activity. We retrospectively analyzed prospectively collected plasma samples (2018-2020) from children with and without pediatric ARDS (PARDS). Plasma levels (ng/mL) of sulfated and non-sulfated HS disaccharides (following enzymatic digestion of total [unfractionated] HS), and HPSE activity (U/mL) were measured using mass spectrometry, while protein biomarkers were assessed by multiplex assay. Among 46 children (36 PARDS, 10 no PARDS), principal component analysis identified three components explaining > 60% of the variance. The primary component (PC1) was characterized by an HS-driven endothelial signature and was distinct from an inflammatory protein signature captured by PC2. In PARDS, children with higher PC1 scores had worse organ dysfunction and fewer ventilator-free days after adjustment for PC2 and PC3. Higher total HS levels were further associated with selective enrichment of sulfated HS motifs, whereas the opposite pattern was observed in non-PARDS. HPSE activity positively correlated with circulating HS levels. These preliminary findings suggest that circulating HS signatures capture a distinct and clinically meaningful dimension of PARDS heterogeneity.