Sepsis-induced endothelial glycocalyx disruption and remodeling: an ultrastructural study in mice

Sepsis damages endothelial cells through glycocalyx degradation, contributing to organ dysfunction. Glycocalyx repair is essential for recovery, but the underlying mechanisms remain unclear. Rhamnan sulfate (RS), a sulfated polysaccharide with anti-inflammatory properties, may support endothelial glycocalyx repair. In this study, we investigated the glycocalyx repair process and the therapeutic potential of RS using a mouse sepsis model.

Sepsis was induced in male C57BL/6 mice by cecal ligation and puncture (CLP). Mice were divided into the RS, control (CTL), and sham groups. RS was orally administered to the RS group, while the CTL group received no treatment after CLP. Sham mice underwent laparotomy only without CLP. Endothelial glycocalyx repair was evaluated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and quantitative TEM analysis. Gene expressions of glycocalyx-related enzymes and inflammatory cytokines were assessed in liver and small intestine tissues by quantitative real-time PCR.

The 7-day survival rate after CLP was significantly higher in the RS group (55%) than in the CTL group (25%). TEM and SEM demonstrated that in the CTL group, the endothelial glycocalyx remained disrupted for up to 72 h after CLP but by two weeks had undergone compensatory regeneration with thickening, exceeding that observed in sham-treated mice. In contrast, in the RS group, glycocalyx continuity was restored by 72 h and normalized to levels comparable to those of the sham-treated group by two weeks. Quantitative TEM analysis supported marked structural alteration of glycocalyx after CLP and normalization of glycocalyx thickness toward sham levels after RS treatment. Quantitative real-time PCR revealed a significant increase in inflammatory cytokines (IL-1β, IL-6, TNF-α) after CLP, which tended to be lower in the RS-treated group. A similar trend was observed for the glycocalyx-degrading enzymes heparanase and hyaluronidase, whose expression was also suppressed by RS treatment.

Electron microscopy allowed detailed observation of endothelial glycocalyx repair in septic mice. RS promoted glycocalyx repair and reduced inflammation, suggesting that administration of RS may be a novel therapeutic strategy for maintaining vascular integrity in sepsis.