Circulating endothelial progenitor cells inversely associate with organ dysfunction in sepsis

Abstract

Purpose: Endothelial dysfunction is a primary contributor to sepsis-related organ dysfunction and death. In sepsis animal models, endothelial progenitor cells (EPC) have contributed to vascular repair. The role of endothelial progenitor cells as a biomarker for organ dysfunction is still unknown. We hypothesized that circulating numbers of endothelial progenitor cells would be associated with improved outcomes in sepsis.

Methods: Prospective, observational single-center cohort study in adult intensive care units at Grady Memorial Hospital, an affiliate of Emory University, from July 2007 through April 2009. Peripheral blood was obtained from 95 patients with sepsis, 37 intensive care unit controls, and 51 healthy controls, of whom only 86 patients with sepsis were used in the analysis because we were not able to obtain enough blood in 9 sepsis patients. Clinical data were obtained, and organ dysfunction was measured by Sepsis-Related Organ Failure Assessment (SOFA) score. Endothelial progenitor cells were assessed by a colony-forming unit (CFU) assay in which peripheral blood mononuclear cells were isolated using Ficoll density-gradient centrifugation and cultured in growth media.

Results: The patients with sepsis had significantly lower mean endothelial progenitor cell colony counts compared with intensive care unit controls (p = 0.035) and healthy controls (p = 0.0005). There was no difference in colony counts between ICU controls and healthy controls (p = 0.81). In the sepsis patients, EPC CFU numbers inversely associated with SOFA score, adjusting for mortality (r (2) = 0.05, p = 0.04).

Conclusion: Increased circulating endothelial progenitor cells inversely correlate with organ dysfunction in sepsis patients.

Fig. 1

a Phase-contrast microscopy of endothelial progenitor cell (EPC) colonies on day 7 from a patient with sepsis. After the initial preplating step, nonadherent cells were collected from the supernatant of the culture and plated again on new fibronectin-coated wells (seen here). Colonies consist of a central cluster of rounded cells surrounded by thin, flat cells (×10). b Endothelial progenitor cell (EPC) colony from patient with sepsis. Similar to Fig. 1, nonadherent cells were collected from the supernatant of the culture after an initial plating step, and replated again on new fibronectin-coated wells. This picture depicts an overlapping fluorescent microscopic image of dil-acetylated low-density lipoprotein (LDL) uptake in red, Ulex europaeus lectin binding in green, and 4′,6-diamidino-2-phenylindole (DAPI), a blue nuclear stain (×10)

Fig. 2

Numbers of EPC colony-forming units (CFU) from patients with sepsis (n = 86), ICU control subjects (n = 37), and healthy control subjects (n = 49). As compared with ICU controls, EPC CFU counts were significantly lower in sepsis patients (p = 0.035). There was no significant difference in EPC CFU counts between ICU controls and healthy controls. Boxes represent the median, 25th and 75th percentiles. The whiskers are the 10th and 90th percentiles. Blue dots represent individual data values

Fig. 3

In patients with sepsis (n = 86), EPC CFU numbers inversely associated with Sepsis-Related Organ Failure Assessment (SOFA) score, adjusting for mortality, assuming an equal slope. Specifically, for a 10-cell decline in EPC counts measured by CFU, total SOFA score increased by 0.5 points (p = 0.04). Black dots represent individual data values, and the line is the fitted regression line. Results were similar after adjustments for presence or absence of shock (p = 0.003). p-Value was calculated from analysis of covariance (ANCOVA)