ENDOTHELIAL GLYCOCALYX SHEDDING IN INTRA-ABDOMINAL SEPSIS: A FEASIBILITY STUDY

Abstract

Background: The endothelial glycocalyx layer (EGL) is a complex meshwork of glycosaminoglycans and proteoglycans that protect the vascular endothelium. Cleavage or shedding of EGL-specific biomarkers, such as hyaluronic acid (HA) and syndecan-1 (SDC-1, CD138) in plasma, have been shown to be associated with poor clinical outcomes. However, it is unclear whether levels of circulating EGL biomarkers are representative of the EGL injury within the tissues. The objective of the present feasibility study was to describe a pathway for plasma and tissue procurement to quantify EGL components in a cohort of surgical patients with intra-abdominal sepsis. We sought to compare differences between tissue and plasma EGL biomarkers and to determine whether EGL shedding within the circulation and/or tissues correlated with clinical outcomes. Methods: This was a prospective, observational, single-center feasibility study of adult patients (N = 15) with intra-abdominal sepsis, conducted under an approved institutional review boards. Blood and resected tissue (pathologic specimen and unaffected peritoneum) samples were collected from consented subjects at the time of operation and 24-48 hours after surgery. Endothelial glycocalyx layer biomarkers (i.e., HA and SDC-1) were quantified in both tissue and plasma samples using a CD138 stain and ELISA kit, respectively. Pairwise comparisons were made between plasma and tissue levels. In addition, we tested the relationships between measured EGL biomarkers and clinical status and patient outcomes. Results: Fifteen patients with intra-abdominal sepsis were enrolled in the study. Elevations in EGL-specific circulating biomarkers (HA, SDC-1) were positively correlated with postoperative SOFA scores and weakly associated with resuscitative volumes at 24 hours. Syndecan-1 levels from resected pathologic tissue significantly correlated with SOFA scores at all time points ( R = 0.69 and P < 0.0001) and positively correlated with resuscitation volumes at 24 hours ( R = 0.41 and P = 0.15 for t = 24 hours). Tissue and circulating HA and SDC-1 positively correlated with SOFA >6. Conclusions: Elevations in both circulating and tissue EGL biomarkers were positively correlated with postoperative SOFA scores at 24 hours, with resected pathologic tissue EGL levels displaying significant correlations with SOFA scores at all time points. Tissue and circulating EGL biomarkers were positively correlated at higher SOFA scores (SOFA > 6) and could be used as indicators of resuscitative needs within 24 hours of surgery. The present study demonstrates the feasibility of tissue and plasma procurement in the operating room, although larger studies are needed to evaluate the predictive value of these EGL biomarkers for patients with intra-abdominal sepsis.

Fig. 1.. Representation of the EGL containing HA anchored to its cell surface receptor, CD44, and syndecan-1 (SDC-1, CD138), with associated heparan sulfate and chondroitin sulfate, during physiologic and pathophysiologic conditions.

HA and SDC-1 are cleaved by HYA, heparanases, and MMP during inflammation or mechanically disrupted during tissue injury, resulting in EGL component shedding into the blood stream (created on Biorender.com). EGL, endothelial glycocalyx layer; HA, hyaluronic acid; HYA, hyaluronidases (HYA); MMP, matrix metalloproteinases.

Fig. 2.. Correlations between plasma and tissue levels of SDC-1.

(A) Comparison between plasma SDC-1 levels and peritoneum tissue. Weak correlations are observed. Correlation coefficient (R) is −0.035 at t = 0 and −0.156 at t = 24 hours, P > .9 for both comparisons. (B) Comparison between plasma SDC-1 levels and resected tissue. Correlation coefficient (R) is 0.019 at t = 0 and −0.293 at t = 24 hours, P > 0.7 for both comparisons. No significant correlations between plasma and tissue levels of SDC-1 were observed in patients with intra-abdominal sepsis. While circulating plasma levels of SDC-1 tended to increase at 24 hours, the correlations between tissue and plasma levels remained weak. This suggests that there is minimal overlap between the circulating and local/tissue levels of glycocalyx biomarkers.

Fig. 3.. Elevations in EGL-specific circulating biomarkers (HA, SDC-1) were positively correlated with postoperative SOFA scores at 24 hours in intra-abdominal sepsis.

Correlation coefficient (R) for HA versus SOFA scores were 0.11 at t = 0 ( P = 0.69) and 0.36 at t = 24 hours ( P = 0.20). Correlation coefficient (R) for SDC-1 versus SOFA scores were 0.19 at t = 0 ( P = 0.48) and 0.35 at t = 24 hours ( P = 0.23). While the strength of association increased at 24 hours, these correlations were not statistically significant ( P > 0.05), potentially because of our small sample size. EGL, endothelial glycocalyx layer; HA, hyaluronic acid; SOFA, sequential organ failure assessment.

Fig. 4.. Elevations in EGL-specific circulating biomarkers (HA, SDC-1) were weakly correlated with postoperative fluid resuscitative volumes at 24 hours in intra-abdominal sepsis.

Correlation coefficient (R) was 0.12 for HA and resuscitation volume ( P = 0.67) and 0.07 for SDC-1 and resuscitation volumes ( P = 0.79). EGL, endothelial glycocalyx layer; HA, hyaluronic acid.

Fig. 5.. (A) Tissue EGL biomarkers (CD138) from resected tissue significantly correlated with SOFA scores at all time points (R = 0.69 and P < 0.0001) and (B) positively correlated with resuscitation volumes at 24 hours (R = 0.41 and P = 0.15 for t = 24 hours).

(C) The correlation coefficient (R) is 0.53 where an individual with a SOFA score >6 has an average 24× higher tissue SDC-1 levels than those with lower SOFA scores (0–6). EGL, endothelial glycocalyx layer; HA, hyaluronic acid; SOFA, sequential organ failure assessment.