Novel Evidence That Very Small Embryonic Like Stem Cells (VSELs) Are Mobilized Into Peripheral Blood in Patients with Inflammatory Bowel Diseases – Correlation with Young Age and Severity of Disease.

We have hypothesized that circulating pluripotent stem cells could play a protective role in the pathogenesis of inflammatory bowel diseases (IBD) and participate in regeneration of damaged intestinal eipthelium. Recently, our group has identified in murine and human BM as well as other organs a population of very small embryonic like stem cells (VSELs) (Leukemia 2006, 20, 857-69). These are cells deposited in BM during development, differentiate into cells from all three germ layers and are capable of long term repopulation of hematopoiesis. They also play an important role in turnover of tissue-specific/committed stem cells in various organs. We have also shown that the number of VSELs circulating in peripheral blood (PB) increases during stress and tissue/organ injury e.g., in patients after stroke (Stroke 2009, 40, 1237-1244) and myocardial infarction (JACC 2009, 53, 1-9). It is currently unknown whether VSELs are mobilized into PB in patients with IBD.

We evaluated the mobilization of VSELs into PB in patients with active IBD. There were twenty patients (n=20) enrolled with de novo diagnosed or untreated flare-ups with mild to moderate ulcerative colitis (Truelove and Witt's criteria) and Crohn's disease (Crohns Disease Activity Index) as well as age-matched healthy subjects (n=10). Blood was sampled on admission, erythrocytes were lysed and CXCR4⁺ CD133⁺ lin^- CD45^- VSELs were evaluated in PB by fluorescence-activated cell sorting analysis (FACS), direct immunofluorescence staining and real-time quantitative polymerase chain reaction to detect expression of developmentally early genes.

In IBD patients, we found an increase in the number of circulating cells expressing stem cells-associated antigens such as CD133, CD34, and CXCR4. More important, we found an increase in the number of circulating primitive cells expressing the VSEL phenotype (CXCR4⁺ CD133⁺ in^- CD45^- cells - smaller than erythrocytes) (median 3.7 [range 0.9 to 8.9] cells/ml; p < 0.001) in comparison to healthy individuals (median 1.33 [range 0.2 – 1.45] cells/ml; p < 0.001 [Mann–Whitney test Friedman's ANOVA followed by Wilcoxon signed-rank test]). The mobilization of VSELs was higher in patients with active Crohn's disease and younger patients. Of note antimicrobial treatment also influenced the mobilization process. Circulating VSELs express pluripotent stem cell markers (Oct-4, SSEA-4, Nanog), CXCR4 receptor and respond robust to stromal derived factor-1 (SDF-1) gradient. We also noticed that the number of mobilized/circulating VSELs correlated in IBD patients with elevated serum level of CXCR4 receptor ligand - stromal derived factor -1 (SDF-1).

Using multiparameter analysis, we have demonstrated for the first time that VSELs could be detected in circulating PB of patients with active IBD. The number of this cell positively correlated with intensity of disease and young age. This strongly supports a potential involvement of circulating pluripotent stem cells in regeneration of damaged intestinal epithelium. However, the biological significance as well as potential application of these cells in regeneration of damaged gut tissue needs further investigations and is currently tested in animal models in our laboratories.

No relevant conflicts of interest to declare.