Regular ArticleCirculating endothelial and endothelial progenitor cells in patients with severe sepsis
Graphical abstract
Comparison of circulating endothelial cell counts between patients in the intensive care unit with severe sepsis compared to patients without sepsis was similar except at 48–72 h post-baseline when the severe sepsis cohort showed significantly higher counts providing insight into the mechanism of microvascular changes in severe sepsis.
Research Highlights
► Patients in intensive care, with and without severe sepsis, had significant elevations in circulating endothelial cell counts compared to healthy volunteers. ► Consensus methodology using immunomagnetic separation demonstrated the ability to quantify circulating endothelial and circulating endothelial progenitor cells. ► Positive correlation between improvement in organ function as measured by Sequential Organ Failure Assessment (SOFA) scores and baseline circulating endothelial progenitor cells.
Introduction
Severe sepsis, defined as sepsis associated with acute organ dysfunction (Levy et al., 2003), involves a complicated host response including activation of several cell types, inflammatory mediators, and coagulation factors. One of the hallmarks is microvascular damage, in which endothelial activation and dysfunction play a pivotal role (Aird, 2003, Bateman et al., 2003). Endothelial cells undergo changes in function and structure resulting in detachment from the vessel wall and subsequent appearance in the circulation (Aird, 2003, Boos et al., 2006).
The presence of circulating endothelial cells (CECs) in peripheral blood of healthy individuals is rare. Their numbers increase in a variety of conditions such as cardiovascular disease, cancer, infection, and inflammatory states (Dignat-George et al., 2003) including septic shock (Mutunga et al., 2001) where they serve as indicators of vascular damage. In the last decade, CEC counts have emerged as an index of assessing endothelial damage or dysfunction (Blann et al., 2005).
Circulating endothelial progenitor cells (CEPCs), which may arise in the bone marrow and appear in peripheral blood, are thought to be recruited in response to vascular trauma (Dignat-George et al., 2003). Increased numbers of CEPCs have been reported in conditions characterized by vascular injury, where a correlation has been shown between number of CEPCs and extent of endothelial damage (George et al., 1992, Strijbos et al., 2009, Woywodt et al., 2006). These cells have high proliferative potential and may function to replace endothelial cells destroyed by pathological processes like those in severe sepsis.
Despite increasing knowledge about CECs and CEPCs in vascular disease, there are few studies of patients with severe sepsis. One study demonstrated increased CEC counts in patients with severe sepsis compared to healthy volunteers and intensive care unit (ICU) patients without sepsis, providing direct evidence of endothelial damage during sepsis (Mutunga et al., 2001). Two other studies showed increased CEPCs in the blood of patients with sepsis compared to healthy controls (Becchi et al., 2008, Rafat et al., 2007). These studies, however, used different methods for identification and quantification of CECs and CEPCs than the current study, which used a Food and Drug Administration (FDA)-approved automated system to accurately and reliably enumerate CECs and an in vitro culture assay for the assessment of endothelial colony forming cells (ECFCs) that display all the properties of CEPCs (Yoder, 2009).
This study's primary objective was to compare the number of CECs in patients with severe sepsis to those in patients without severe sepsis at three time points to investigate the kinetics of the endothelial response. Secondary objectives included quantifying the number of CEPCs in the same patients and correlating CEC and CEPC counts with Sequential Organ Failure Assessment (SOFA) scores and outcomes (28-day mortality, length of ICU stay, or length of hospital stay). Understanding the relationship between CEC/CEPC levels and outcomes may provide insight into the mechanisms of endothelial cell changes in severe sepsis and lead to targeted therapy.
Section snippets
Methods
This was a nontherapeutic, observational study with patients enrolled between August 2007 and March 2009 at 3 hospitals in the United States. Hospitals included: Methodist Hospital (Indianapolis, IN), a 725-bed academic teaching hospital with 131 adult mixed medical and surgical ICU beds; Massachusetts General Hospital (Boston, MA), a 1000-bed quaternary referral center and teaching hospital affiliated with Harvard Medical School, with an 18-bed medical ICU and 16-bed coronary ICU; and
Patient data
Forty-six patients (18 in severe sepsis cohort and 28 in non-sepsis cohort) admitted to the ICU were enrolled into the study. No significant demographic differences between the cohorts were noted other than difference in the individual cardiology, renal, and neurology SOFA scores (Table 1).
Patients in the severe sepsis cohort met the following inclusion criteria: presence of a suspected or proven infection, and presence of ≥ 2 sepsis-associated organ dysfunctions. Patients in the non-sepsis
Discussion
This is the first study to evaluate CEC counts and CEPC culture assays in ICU patients with severe sepsis compared to ICU patients without sepsis. It is also the first study in these patients to use reliable methods and a consensus definition to identify the cells. Observed was an increase in CECs in the two cohorts when compared to established normal values in healthy volunteers. When compared to each other, CEC counts in both cohorts were similar except at 48–72 h, when they were
Acknowledgments
The authors would like to thank Barb Utterback of Eli Lilly and Company for project management, and Maryann Weller, Caron Modeas, and Joseph Durrant of i3Statprobe for writing and editorial assistance.
References (19)
The role of the endothelium in severe sepsis and multiple organ dysfunction syndrome
Blood
(2003)Circulating endothelial cells in cardiovascular disease
J. Am. Coll. Cardiol.
(2006)Identification of a novel hierarchy of endothelial progenitor cells using human peripheral and umbilical cord blood
Blood
(2004)Vessel wall-derived endothelial cells rapidly proliferate because they contain a complete hierarchy of endothelial progenitor cells
Blood
(2005)Isolation and enumeration of circulating endothelial cells by immunomagnetic isolation: proposal of a definition and a consensus protocol
J. Thromb. Haemost.
(2006)Defining human endothelial progenitor cells
J. Thromb. Haemost.
(2009)Redefining endothelial progenitor cells via clonal analysis and hematopoietic stem/progenitor cell principals
Blood
(2007)Bench-to-bedside review: microvascular dysfunction in sepsis–hemodynamics, oxygen transport, and nitric oxide
Crit. Care
(2003)The increase of endothelial progenitor cells in the peripheral blood: a new parameter for detecting onset and severity of sepsis
Int. J. Immunopathol. Pharmacol.
(2008)
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