A26-13 Pediatric ARDS Is Characterized by Selective Enrichment of Sulfated Heparan Sulfate Fragments

Abstract Introduction The endothelial glycocalyx (EGCX), a heparan sulfate proteoglycan (HSPG)-rich layer lining the microvasculature, is a critical gatekeeper of endothelial cell (EC) homeostasis. During sepsis, HS is shed through TNF-α-dependent activation of endothelial heparanase, which selectively targets highly sulfated regions within HS chains; this targeted shedding renders core PG ectodomains more accessible to proteolytic cleavage. Together, these processes contribute to EGCX degradation, loss of EC barrier integrity, and propagation of organ injury. We hypothesized that in pediatric ARDS, EGCX degradation preferentially releases sulfated HS fragments into the circulation, and this pattern parallels that of syndecan-1, a major HSPG. Methods We conducted a retrospective analysis of prospectively collected plasma samples (2018-2020) from a cohort of children with and without ARDS. Children without ARDS had acute respiratory failure without evidence of lung injury or sepsis at enrollment. HPLC-MS/MS was used to measure sulfated and non-sulfated HS disaccharide levels (i.e., hexuronic acid, or ΔUA, linked to glucosamine, or GlcNAc) in plasma after enzymatic digestion of total (or unfractionated) HS. We quantified syndecan-1 concentrations with ELISA. We fit linear regression models to examine whether the proportion of sulfated HS changed with absolute levels of total HS (or syndecan-1) and assess whether these associations differed by ARDS status. We then compared the proportions of sulfated HS among HS-based patient clusters previously identified in pediatric ARDS. Results This study included 36 intubated children with and 10 without ARDS. Median plasma collection time was 4.5 days (IQR 3.4-5.6) from intubation, and sepsis was present in 81% of the ARDS cohort. In ARDS, higher total HS levels were associated with higher proportions of sulfated HS, while in children without ARDS, higher total HS corresponded to lower proportions of sulfated HS (Figure 1A). These associations significantly varied by ARDS status (Δ slope=0.15; 95% CI 0.07-0.26; p = 0.020), with similar associations observed for syndecan-1 (Δ slope=0.12; 95% CI 0.02-0.22; p = 0.022). Cluster 3 (n = 5), previously characterized by differentially elevated absolute levels of sulfated and non-sulfated HS and worse outcomes, exhibited the highest proportion of sulfated HS (p 0.001; Figure 1B). Conclusions We demonstrate that in pediatric ARDS, EGCX HS shedding is patterned; sulfated HS fragments, rather than non-sulfated, are proportionally enriched, and this enrichment may have both mechanistic and clinical significance. Future studies are needed to determine the temporal kinetics of these relationships, and whether the relative balance of sulfated and non-sulfated HS predicts disease severity and poor outcomes in pediatric ARDS. This abstract is funded by: Children’s Discovery and Innovation Institute at UCLA; K12HD047349; K23HD096018