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 is a potential underrecognized source of phenotypic heterogeneity. In pediatric ARDS (PARDS), we examined whether circulating heparan sulfate (HS) signatures, as readouts of eGCX shedding, capture inter-individual variability beyond other eGCX components and protein biomarkers, whether specific HS structural features are enriched, and whether they correlate with heparanase-1 (HPSE) activity. We retrospectively analyzed plasma samples (2018–2020) from children with and without PARDS. Mass spectrometry quantified glycosaminoglycans and sulfation subtypes alongside HPSE activity, while protein biomarkers were measured by multiplex assay. Among 46 children (36 PARDS, 10 no PARDS), principal component analysis identified three components explaining 63% of variance. The primary component (PC1) was driven by 6- O - and N -sulfated HS subtypes, while a secondary component (PC2) reflected inflammatory proteins. In PARDS, higher PC1 scores were associated with worse organ dysfunction and fewer ventilator-free days. Higher total HS levels were associated with enrichment of sulfated HS (including 6- O - and N -sulfated subtypes), whereas the opposite pattern was observed in non-PARDS; higher HPSE activity further correlated with these subtypes. These preliminary findings suggest that variation in circulating HS signatures identifies a distinct endothelial-derived biological axis linked to clinical outcomes.