Transient Extremity Ischemia Augments CD34+ Progenitor Cell Availability

Abstract

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 Following induction of ischemia, blood samples were withdrawn at baseline, 30 min, 12 h and 24 h. The number of progenitor cells was determined by flow cytometry after the harvested cells were cultured for 5 days.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 × 10(6) cells/ml in the pretreatment blood samples to 0.7 ± 0.1 × 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 × 10(4) cells/ml in the pretreatment samples to 7.17 ± 1.34 × 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.

Remote Limb Ischemic Conditioning at Two Cuff Inflation Pressures Yields Learning Enhancements in Healthy Adults

“…Others have found, however, that RLIC did not affect serum levels of tissue plasminogen activator (tPA), nor tPA inhibitor antigen and activity, in healthy humans (Pedersen et al, 2012). For VEGF, one study found that RLIC increased plasma VEGF levels and the number of circulating endothelial progenitor cells (Kimura et al, 2007), while another reported that VEGF concentrations did not change 0.5, 12, or 24 hours after conditioning (Czeiger et al, 2011), in healthy adults. Regarding inflammatory biomarkers, RLIC altered levels of IL-6 and TNF-α in infants undergoing cardiac surgery (Zhou et al, 2010), but caused no change in IL-6 or TNF-α levels in children undergoing surgery for a congenital heart defect (Cheung et al, 2006).…”

Remote ischaemic conditioning in the context of type 2 diabetes and neuropathy: the case for repeat application as a novel therapy for lower extremity ulceration

“…It has been demonstrated that EPC mobilisation occurs following RIPC in both mice and humans [82, 83], and this appears likely to contribute significantly to the late phase cardioprotective effects of RIPC [82]. We therefore hypothesise that this may be another important and under-recognised mechanism behind the poorer response to RIPC in T2DM, particularly in the rarely-studied late phase of protection.…”

“…It is felt the mechanisms are similar, but that both the early and late phase of RIPC are reliant on neural pathways to a greater degree than local ischaemic preconditioning [42]. The late phase of RIPC has also been shown to result in the mobilisation of bone marrow-derived stem cells, including CD34+ cells, into both the peripheral blood and damaged myocardium, which have the capacity to induce angiogenesis and endothelial repair [82, 83]. …”

“…Current methods to increase EPCs include administration of granulocyte-colony stimulating factor, which has serious cardiovascular side effects and is often ineffective in diabetics [23, 169], or by culturing and re-administering EPCs [83]. RRIC would offer a safer, more cost-effective and easily-administered alternative, with automated RRIC devices already designed and manufactured for self-administration at home.…”

“…Kimura et al found VEGF levels to be increased after one month of 6 times daily RRIC [197]. In contrast, Czeiger et al did not identify raised VEGF levels, despite increased EPC numbers following RIPC [83]. Further, increased EPC levels are associated with a decreased incidence of diabetic complications, including retinopathy [142, 143, 170, 217].…”