Shiga toxin type 2, a causal agent of hemolytic uremic syndrome, improved angiogenic and repair abilities of late outgrowth endothelial progenitor cells

MENA HA; LANDONI V.I; SCHIERLOH P; RODRIGUEZ-RODRIGUES N; SCHATTNER, M; FERNÁNDEZ G.C.; NEGROTTO, S

Berlin

Congreso; Congress of the International Society on Thrombosis and Haemostasis; 2017

ISTH

Hemolytic Uremic Syndrome (HUS), the main cause ofpediatric acute renal failure, is caused by E. coli producing Shiga toxins(Stx) and characterized by massive endothelial damage, which isworsened by inflammation, especially in the presence of bacterial lipopolysaccharides(LPS). Endogenous regeneration of the vessel wallinvolves local and bone marrow-derived endothelial progenitor cells(EPC) as well as nearby mature endothelial cells (EC). Although Stxtoxic effects on mature EC have been widely studied, its action onEPC and angiogenesis remain to be elucidated.Aims: We aimed to analyze the effect of Stx alone or in combinationwith LPS on survival and angiogenic properties of EPC.Methods: Human cord blood-derived late-outgrowth EPC and umbilicalvein EC were cultured in cytokine-rich growth medium EGM2.Cells were sensitized with LPS for 18 h and then Stx type 2 was addedfor another 18 h.Results: Nuclear morphology analysis revealed that Stx, at concentrationsthat are known to induce mature EC death, had no effect on EPCsurvival cultured in basic medium (EBM2+ 2% FBS), which undergoapoptosis only after LPS sensitization (Fig.1). Moreover, no Stx effectwas observed when EPC were cultured on EGM2 (Fig.1). Stx receptorGb3 was expressed on EPC surface and upregulated by LPS+Stx(180±12*% of control, n=3, *p< 0.05, ANOVA, flow cytometry). WhileEPC proliferation was not affected, ICAM-1 and E-selectin expression was significantly augmented by Stx on LPS-sensitized EPC (flow cytometry,Fig.1). Surprisingly and opposite to its well-known toxic effecton mature EC, Stx alone triggered EPC angiogenic functions likeadhesion (pNPP assay), self-repair abilities (scratch assay) and newvessel formation (matrigel), while LPS seems to have no effect (Fig.2).Conclusions: Our results showed that EPC not only were more resistantto Stx-mediated toxicity than mature EC, but also displayed improvedangiogenic abilities, suggesting that EPC could be considereda therapeutic target to promote repair in HUS.