Transient Extremity Ischemia Augments CD34+Progenitor Cell Availability

Peripheral blood is an easily accessed source for stem cell production; however, the number of cells produced is relatively low. We hypothesized that ischemic preconditioning may serve as a safe method to increase the number of CD34+ cells that can be harvested and cultured in a short period. This study was conducted to test this hypothesis by examining the safety and efficacy of brief, transient ischemia of the lower limbs to augment the number of cells that can be produced from blood of healthy volunteers. Following induction of ischemia, blood samples were withdrawn at baseline, 30 min, 12 h and 24 h. The number of progenitor cells was determined by flow cytometry after the harvested cells were cultured for 5 days. We also analyzed the blood samples to determine IL-8 and VEGF concentrations. No serious adverse events were observed. The total number of cells increased from 0.46 +/- 0.1 x 10(6) cells/ml in the pretreatment blood samples to 0.7 +/- 0.1 x 10(6) cells/ml in blood taken 12 h after the conclusion of transient ischemia, p = 0.0029. The number of CD34+ cells increased from 4.23 +/- 0.8 x 10(4) cells/ml in the pretreatment samples to 7.17 +/- 1.34 x 10(4) cells/ml in blood taken 12 h after ischemia, p = 0.0001. The harvested stem cells maintained their ability to construct tubular structures. The augmentation in the number of CD34+ cells was positively correlated with the increase of IL-8, but not with VEGF concentrations. Ischemic preconditioning is a safe and effective technique to increase the availability of stem cells for therapeutic purposes.