Effects of low dose endotoxemia on endothelial progenitor cells in humans

Background Endothelial progenitor cells (EPCs) are a specific subtype of hematopoietic stem cells that migrate from the bone marrow to the peripheral circulation where they contribute to the repair of injured endothelium and to the formation of new blood vessels. Levels of circulating EPCs have been investigated in different inflammatory disease states. However, data on circulating EPC levels and systemic inflammation remain scarce and contradictory. Objective We investigated a putative relationship of low grade experimental endotoxemia to changes in circulating EPC levels. Methods Randomized, double-blind, placebo-controlled parallel group trial in 36 healthy male volunteers. Thirty-two volunteers received 2 ng/kg LPS intravenously, the remaining four an equal volume of physiologic saline solution as placebo. Results Endothelial progenitor cells showed a significant decrease over the observation period among the 32 subjects challenged with LPS (P < 0.0001) and reached their nadir at 6 h, with a median decrease of 62% (interquartile range: 48–81%) compared with baseline levels. Circulating EPCs returned to values comparable to baseline 24 h after LPS challenge. Conclusion Infusion of 2 ng/kg LPS led to a significant decrease in peripheral EPCs. These results suggest that the early phase of acute inflammation is associated with a decrease in peripheral EPCs.