Abstract 15327: In vivo Ischemic Limb Injury Activates Proliferation and Mobilization of Pluripotent Bone Marrow- Derived Very Small Embryonic-Like Stem Cells
Very small embryonic-like stem cells (VSELs) were identified as rare quiescent, nonhematopoietic (CD45-/Lineage-) and pluripotent Oct-4+ stem cells in adult murine and human tissues including bone marrow (BM). Murine BM- derived VSELs were shown to differentiate into cells from all three germ layers and to participate in heart repair after injection into infarcted myocardium by enhancing perfusion and angiogenesis. However, their activation during physiological or pathological events in vivo have not been reported. In this study, we examined if acute ischemic injury may stimulate both proliferation of quiescent VSELs in BM and their mobilization into peripheral blood (PB). Wild-type C57BL/6 mice (9-week old) underwent hind limb ischemia by permanent proximal femoral artery occlusion. Mice were injeced with bromodeoxyuridine (BrdU, 1mg/mouse/i.p.)every two days and were scarified at 2, 7, 14 and 28 days following ischemia (N=5/group). PB and BM from non- and ischemic limbs were collected from individual animals. Healthy non-ischemic mice were used as control groups in each time point. The presence of proliferating (BrdU+) VSELs (CD45-/Lineage-/Sca-1+), endothelial progenitor cells (EPCs; CD45-dim/Lin-/Sca-1+/Flk-1+) and hematopoietic stem cells (HSCs; CD45+/Lineage-/Sca-1+) in PB and BM was evaluated by multiparameter flow cytometry and ImageStream system. The expression of genes related to the VSEL and EPC presence was examined by real time RT-PCR. We established that the content of VSELs was significantly increased in BM of ischemic mice after 7 days post injury. We observed elevated number of BrdU+ VSELs in BM and circulating in PB of the injured animals indicating vast impact of acute ischemia on activation of these cells. Similar results were obtained for BM- derived and circulating EPCs. We conclude that acute tissue injury such as limb ischemia may provide stimulatory agents to activate proliferation of quiescent VSELs in BM and their mobilization into PB. Thus, the ischemic injury may recruit the normally quiescent pluripotent stem cell pools to enhance endogenous mechanisms of tissue repair including stem/ progenitor cell- dependent angiogenesis which we currently investigate.
- © 2012 by American Heart Association, Inc.