Effect Of Stem Cell Mobilization Research Articles

Influence of Local Chemokine Delivery and Postoperative Peripheral Blood Mobilization on Achilles Tendon Repair

Category:Basic Sciences/Biologics; Sports; TraumaIntroduction/Purpose:Mesenchymal stem cells (MSCs) have demonstrated promise in augmenting the surgical repair of full thickness tendon tears. Despite this promise, obtaining a therapeutic concentration of MSCs is time-, labor- and resource intensive, and is subject to ever-tightening governmental regulations. Our group recently demonstrated that postoperative mobilization of MSCs from the marrow compartment and into peripheral blood via subcutaneous granulocyte- colony stimulating factor administration enhanced tendon-bone healing in a rat model of surgical repair of a full-thickness supraspinatus tendon tear. We hypothesized that combining postoperative stem cell mobilization with local delivery of a chemokine that stimulates MSC chemotaxis would enhance the surgical repair of a mid-substance Achilles tendon transection.Methods:Following IACUC approval, Achilles tendons were unilaterally frayed via multiple longitudinal scalpel blade nicks in 24 Lewis rats. Tendons were then surgically transected, followed by repair with braided non-absorbable suture in a modified-Kessler pattern. Based on randomization (n=6/group), the tendon anastomosis was coated with a resorbable chitosan hydrogel containing 100 ng of the chemokine, CCL5 (RANTES), or hydrogel without RANTES. Skin closure and anesthesia recovery were then performed; rats were allowed ad libitum activity. Beginning 24 hours postoperatively, rats received a daily subcutaneous injection of either a peripheral blood mobilizing agent, AMD3100 (5 mg/kg), or saline; dosing was repeated at 48 and 72 hours. At the 4- week endpoint, Achilles tendons harvested en bloc. Decalcified histologic sections were stained with H&E and Alcian Blue as well as immunostained for Collagen III, CD163, and CD68. Slides were digitized (40x magnification) and graded by blinded reviewers via modified-Bonar score to assess tendon integrity.Results:Rats that received local application of RANTES-loaded chitosan hydrogel had worse (higher) modified-Bonar subscores with respect to tenocyte morphology, collagen orientation, and ground substance staining, though none of these comparisons were statistically significant (p=0.068, p=0.672, and p=0.407, respectively). Animals that received subcutaneous AMD3100 alone, or in conjunction with RANTES-loaded chitosan hydrogel displayed the best (lowest) total modified Bonar scores, though these comparisons were also not statistically significant (p = 0.498). No significant differences were found with respect to CD163 (p=0.132) and CD68 (p=0.104) staining. Despite a lack of statistical significance, animals that received AMD3100 displayed a higher number of both macrophage subtypes. No differences were found with respect to Collagen III immunostaining (p=0.808).Conclusion:Tendon repair and regeneration remains a significant clinical challenge, which may be aided by MSC transplantation. The mobilization of endogenous marrow-derived MSCs into peripheral blood and subsequent recruitment via local chemokine delivery may be an efficacious way to enhance tendon repair without the need for ex vivo processing. We failed to demonstrate significant effects of stem cell mobilization via AMD3100 injections, and chemokine-directed recruitment, though trends were present indicating that AMD3100 alone may be beneficial. Additional work is required to draw any translatable conclusions from this research.

No harmful effect of stem cell mobilization by granulocyte-colony stimulating factor on non-culprit coronary plaques after sirolimus-eluting stent implantation

Purpose: Previous studies have demonstrated that stem cell mobilization by granulocyte-colony stimulating factor (G-CSF) attenuates the endothelial dysfunction in mechanically disrupted animal artery models. However, some clinical studies have shown increased neointimal hyperplasia in patients who underwent bare metal stent implantation. Furthermore, the effect of stem cell mobilization on non-culprit plaques is unknown. The purpose of this study was to evaluate the effects of stem cell mobilization by G-CSF on non-culprit coronary plaques after sirolimus-eluting stent (SES) implantation. Methods: This double-blinded randomized placebo-control study (primarily designed to evaluate the effect of stem cell mobilization by G-CSF on endothelial function after SES implantation) assigned patients to the G-CSF group (n=50) or the placebo group (n=50). After successful SES implantation, the patients received subcutaneous injection of G-CSF (300 mg daily) or saline for 5 days. Follow-up angiography and intravascular ultrasound (IVUS) was performed 9 months after SES implantation. Plaque volume was measured by IVUS at non-culprit segments which were defined as more than 5mm proximal or distal from the stent. Percent change in plaque volume (ΔPV) of non-culprit segments between post-procedure and follow-up was evaluated. Results: Plasma CD34+ cell level did not differ between the 2 groups at baseline (0.94±0.55 vs. 0.93±0.68/μL, p = 0.96). It significantly increased after G-CSF injection (0.94±0.55 vs. 18.39±13.55/μL, p <0.001) but did not in the placebo group (0.93±0.68/μL vs. 1.35±2.36/μL, p = 0.22). No death or myocardial infarction was observed during follow-up. Follow-up IVUS was available in 39 G-CSF patients (78%) and 43 placebo patients (86%) (p = 0.30). There was no significant difference in ΔPV between both groups at proximal (-11.0±16.4% vs. -14.7±9.8%, p = 0.35) and distal (-5.1±28.6% vs. -4.9±17.3%, p = 0.97) non-culprit segments. Conclusion: Stem cell mobilization by G-CSF does not increase plaque volume at non-culprit coronary plaques after SES implantation.

Granulocyte colony stimulating factor therapy for acute myocardial infarction

Acute myocardial infarction (AMI) is the leading cause of death in developed countries, and current treatment modalities have failed to regenerate the dead myocardium resulting from the ischemic damage. Stem cells have the potential to regenerate the damaged myocardium. These cells can be mobilized from the bone marrow by factors such as granulocyte colony stimulating factor (G-CSF). To assess the effects of stem cell mobilization following granulocyte colony stimulating factor therapy in patients with acute myocardial infarction. We searched CENTRAL (The Cochrane Library Issue 4, 2010), MEDLINE (1950 to November week 3, 2010), EMBASE (1980 to 2010 week 48), BIOSIS Previews (1969 to 30 November 2010), ISI Science Citation Index Expanded (1970 to 4 December 2010) and ISI Conference Proceedings Citation Index - Science (1990 to 4 December 2010). We also checked reference lists of articles. We included randomized controlled trials including participants with a clinical diagnosis of AMI who were randomly allocated to the subcutaneous administration of G-CSF through a daily dose of 2.5, 5 or 10 microgram/kg for four to six days or placebo. No age or other restrictions were applied for the selection of patients. Two authors independently selected trials, assessed trials for eligibility and methodological quality, and extracted data regarding the clinical efficacy and adverse outcomes. Disagreements were resolved by the third author. We included seven trials reported in 30 references in the review (354 participants). In all trials, G-CSF was compared with placebo preparations. Dosage of G-CSF varied among studies, ranging from 2.5 to 10 microgram/kg/day. Regarding overall risk of bias, data regarding the generation of randomization sequence and incomplete outcome data were at a low risk of bias; however, data regarding binding of personnel were not conclusive. The rate of mortality was not different between the two groups (RR 0.64, 95% CI 0.15 to 2.80, P = 0.55). Regarding safety, the limited amount of evidence is inadequate to reach any conclusions regarding the safety of G-CSF therapy. Moreover, the results did not show any beneficial effects of G-CSF in patients with AMI regarding left ventricular function parameters, including left ventricular ejection fraction (RR 3.41, 95% CI -0.61 to 7.44, P = 0.1), end systolic volume (RR -1.35, 95% CI -4.68 to 1.99, P = 0.43) and end diastolic volume (RR -4.08, 95% CI -8.28 to 0.12, P = 0.06). It should also be noted that the study was limited since the trials included lacked long enough follow up durations. Limited evidence from small trials suggested a lack of benefit of G-CSF therapy in patients with AMI. Since data of the risk of bias regarding blinding of personnel were not conclusive, larger RCTs with appropriate power calculations and longer follow up durations are required in order to address current uncertainties regarding the clinical efficacy and therapy-related adverse events of G-CSF treatment.

Effects of stem cell mobilization by granulocyte colony-stimulating factor on endothelial function after sirolimus-eluting stent implantation: A double-blind, randomized, placebo-controlled clinical trial

Stem cell mobilization by granulocyte colony-stimulating factor (G-CSF) has been shown to enhance endothelial healing after spontaneous or iatrogenic arterial disruption. Granulocyte colony-stimulating factor treatment might attenuate endothelial dysfunction after sirolimus-eluting stent (SES) implantation that may be associated with adverse cardiac events during follow-up. This prospective, double-blind, randomized, placebo-controlled study investigated whether G-CSF improved endothelial dysfunction after SES implantation. One hundred patients who underwent SES implantation were randomly assigned to the G-CSF (n = 50) or the placebo group (n = 50). They received daily subcutaneous injection of 300 μg G-CSF or saline for 5 days. Endothelial function was estimated by measuring the coronary vasoreactivity in the segments 15 mm proximal and distal to SES in response to intracoronary infusion of acetylcholine (10(-8) and 10(-7) mol/L) at 9-month follow-up. Follow-up angiography was performed in 41 G-CSF patients (82%) and 46 placebo patients (92%) (P = .14). Changes in coronary diameter in response to acetylcholine infusion in the proximal segment were not significantly different between the 2 groups. However, vasoconstriction in the distal segment in response to 10(-8) mol/L (-3.9% ± 6.4% vs -7.0% ± 8.1%, P < .05) and 10(-7) mol/L (-8.8% ± 11.0% vs -15.2% ± 7.6%, P < .01) acetylcholine infusion was attenuated in the G-CSF group. Endothelium-independent vasodilatation after nitrate infusion did not differ between the 2 groups. Granulocyte colony-stimulating factor attenuates endothelial dysfunction after SES implantation.

Adult Stem Cell Mobilization Enhances Intramembranous Bone Regeneration: A Pilot Study

Stem cell mobilization, which is defined as the forced egress of stem cells from the bone marrow to the peripheral blood (PB) using chemokine receptor agonists, is an emerging concept for enhancing tissue regeneration. However, the effect of stem cell mobilization by a single injection of the C-X-C chemokine receptor type 4 (CXCR4) antagonist AMD3100 on intramembranous bone regeneration is unclear. We therefore asked: Does AMD3100 mobilize adult stem cells in C57BL/6 mice? Are stem cells mobilized to the PB after marrow ablation? And does AMD3100 enhance bone regeneration? Female C57BL/6 mice underwent femoral marrow ablation surgery alone (n = 25), systemic injection of AMD3100 alone (n = 15), or surgery plus AMD3100 (n = 57). We used colony-forming unit assays, flow cytometry, and micro-CT to investigate mobilization of mesenchymal stem cells, endothelial progenitor cells, and hematopoietic stem cells to the PB and bone regeneration. AMD3100 induced mobilization of stem cells to the PB, resulting in a 40-fold increase in mesenchymal stem cells. The marrow ablation injury mobilized all three cell types to the PB over time. Administration of AMD3100 led to a 60% increase in bone regeneration at Day 21. A single injection of a CXCR4 antagonist lead to stem cell mobilization and enhanced bone volume in the mouse marrow ablation model of intramembranous bone regeneration.

Stem Cell Mobilization by Granulocyte Colony-Stimulating Factor for Myocardial Recovery After Acute Myocardial Infarction: A Meta-Analysis

The objective of this meta-analysis was to evaluate the effect of stem cell mobilization by granulocyte colony-stimulating factor (G-CSF) on myocardial regeneration on the basis of a synthesis of the data generated by randomized, controlled clinical trials of G-CSF after acute myocardial infarction (AMI). Experimental studies and early-phase clinical trials suggest that stem cell mobilization by G-CSF may have a positive impact on cardiac regeneration after AMI. The role of G-CSF in patients with AMI remains unclear considering the inconsistent results of several clinical trials. For our analysis, PubMed, the Cochrane Central Register of Controlled Trials, conference proceedings from major cardiology meetings, and Internet-based sources of information on clinical trials in cardiology from January 2003 to August 2007 served as sources. Two reviewers independently identified studies and abstracted data on sample size, baseline characteristics, and outcomes of interest. Eligible studies were randomized trials with stem cell mobilization by G-CSF after reperfused AMI that reported data regarding the change in left ventricular ejection fraction (LVEF) at follow-up. Ten trials using stem cell mobilization by G-CSF, including 445 patients, met the inclusion criteria. Significant improvement in LVEF at follow-up was observed in both the G-CSF and placebo groups. Compared with placebo, stem cell mobilization by G-CSF did not enhance the improvement of LVEF at follow-up (mean difference 1.32% [95% confidence interval -1.52 to 4.16; p = 0.36]). Moreover, the mean difference of reduction of infarct size between the treatment and placebo groups was -0.15 (95% confidence interval -0.38 to 0.07, p = 0.17). Cumulatively, available evidence does not support a beneficial effect of G-CSF in patients with AMI after reperfusion.

Influence of Stem Cell Mobilization and Liver Regeneration on Hepatic Parenchymal Chimerism in the Rat

Despite the newly discovered plasticity of hematopoietic stem cells, their capacity to "transdifferentiate" into parenchymal cells and the regulation of this process is not yet elucidated. The present study was designed to investigate the effect of stem cell mobilization and liver regeneration on this process using a syngeneic rat female-to-male liver transplantation model. Rate and frequency of Y-chromosome containing hepatocytes was determined by fluorescence-in situ hybridization (FISH) using a rat Y-chromosome specific probe. Rats were subjected to full-size or partial liver transplantation with and without stem cell mobilization using granulocyte colony stimulating factor (G-CSF). The effect of stem cell mobilization was confirmed by assessing the white blood count and by evaluating the migration of granulopoietic precursor cells to the liver. Treatment with G-CSF induced a twofold increase of peripheral white blood cells and a strong influx of granulopoietic precursor cells into the liver. Transplantation of a partial liver graft was followed by a 90% recovery of the original liver weight within a week, demonstrating the strong regenerative stimulus. Irrespective of the experimental model, the incidence and rate of Y-chromosome containing hepatocytes never exceeded 0.77%. Neither stem cell mobilization nor liver regeneration enhanced the incidence or rate of stem cell derived hepatocytes in a liver graft with unimpaired regenerative potential.

The Effect of Stem Cell Mobilization by Granulocyte-Colony Stimulating Factor on Neointimal Hyperplasia and Endothelial Healing After Vascular Injury With Bare-Metal Versus Paclitaxel-Eluting Stents

The goal of this study was to investigate the effect of mobilized stem cells by granulocyte-colony stimulating factor (G-CSF) on neointimal growth, the biologic impact on vascular healing process, and the utility of paclitaxel-eluting stent (PES) in this circumstance. Questions have been raised on the safety of stem cell mobilization because of the tendency of neointimal overgrowth in a recent clinical trial, despite improvement of cardiac function. Rabbits underwent iliac artery injury with bare-metal stent (BMS) or PES and then received rhG-CSF or placebo for 6 days. Morphometric analysis and scanning electron microscopy for re-endothelialization were performed. The characteristics of mobilized peripheral blood mononuclear cells were determined in vitro, and the fate of these cells was evaluated by re-infusion with tagging in vivo. At day 60 after stenting, neointimal overgrowth was observed at BMS with G-CSF. The tendency of neointimal overgrowth was substantially reduced on PES. Intriguingly, the delayed endothelial recovery on PES was restored to normal after G-CSF treatment. The G-CSF increased not only the endothelial progenitor cells, but also putative smooth muscle progenitor cells. Paclitaxel, at working concentration, preferentially inhibited proliferation of smooth muscle lineage cells rather than endothelial lineage cells. Our findings demonstrate that G-CSF mobilizes putative vascular progenitor cells in peripheral blood, which induces neointimal overgrowth at stented vasculature. Unique differential action of paclitaxel results in the enhanced endothelial healing with reduced neointimal growth after G-CSF treatment, suggesting that drug-eluting stents might be the optimal modality for revascularization in cytokine-based stem cell therapy.

Effects of Stem-Cell Mobilization With Recombinant Human Granulocyte Colony Stimulating Factor in Patients With Percutaneously Revascularized Acute Anterior Myocardial Infarction

This study reports the findings in a group of 13 patients aged 53+/-8 years with anterior wall acute myocardial infarction who were revascularized with stents and treated with recombinant human granulocyte colony stimulating factor (G-CSF). Patients were initially treated with intravenous thrombolytics. The first cardiac catheterization was performed between days 0 and 5 after acute myocardial infarction, when the left anterior descending artery was stented. A 10-day course of 10 .g/kg/day G-CSF was started 5 days after acute myocardial infarction. Blood cell counts and immunophenotyping were done to assess the total number of circulating CD34+ cells and their subpopulations in serial fashion. At 3-month follow-up, cardiac catheterization was repeated. Functional recovery was defined as an increase in ejection fraction. All patients did well initially, but 1 had spontaneous spleen rupture on day 8 of G-CSF administration, which required emergency splenectomy. The gain in ejection fraction varied among patients from -22 to +18 (mean, 6.2%+/-12%), and correlated directly with the total number of circulating CD34+ CD38- cells/microL on the fifth day of G-CSF treatment (r=0.78; P<.003). The gain in ejection fraction correlated inversely with peak MB fraction creatine kinase (r=-0.82; P<.002). Stem-cell mobilization with G-CSF is a feasible and safe treatment for patients with revascularized acute myocardial infarction. However, because of the possibility of acute splenitis induced by massive cell mobilization, future studies should be designed with due caution to take this eventuality into account.

Effect of stem cell mobilization with cyclophosphamide plus granulocyte colony‐stimulating factor on morphology of haematopoietic organs in mice

Both granulocyte colony-stimulating factor (G-CSF) and cyclophosphamide (CY) are employed in the clinic as mobilizing agents to stimulate the egress of haematopoietic stem/progenitor cells (HSPC) from bone marrow (BM) into peripheral blood (PB). However, although both compounds are effective, the simultaneous administration of G-CSF + CY allows for optimal mobilization. The aim of this study was to compare morphological changes in major haematopoietic organs in mice mobilized by G-CSF + CY. We employed the standard G-CSF + CY mobilization protocol, in which mice were injected at day 0 with a single dose of CY followed by daily injection of G-CSF for 6 consecutive days. We noticed that the cytoreductive effect of CY on BM and spleen tissue was compensated at day 2 by the pro-proliferative effect of G-CSF. Furthermore, as evidenced by histological examination of BM sections at day 4, egress of haematopoietic cells from BM was accelerated by 2 days as compared to mobilization by G-CSF or CY alone; also, by day 6 there was accumulation of early haematopoietic (Thy-l(low) c-kit+) cells in the spleens and livers of mobilized animals. This implies that HSPC that are mobilized from BM and circulate in PB may 'home' to peripheral organs. We envision that such an accumulation of these cells in the spleen (which is a major haematopoietic organ in mouse) allows them to participate in haematopoietic reconstitution. Their homing to other sites (for example the liver) is evidence that BM-derived stem cells are playing a pivotal role in organ/tissue regeneration. The potential involvement of major chemoattractants for stem cells, like stromal-derived factor-1 which is induced by CY in various regenerating organs such as the liver, requires further study. We conclude that inclusion of CY into mobilization protocols on the one hand efficiently increases the egress of HSPC from the BM, but on the other hand may lead to the relocation of BM stem cell pools to peripheral tissues.

No effect of stem cell mobilization with GM-CSF on infarct size and left ventricular function in experimental acute myocardial infarction.

To evaluate the effect of bone marrow pluripotent stem cell mobilization with granulocyte-monocyte colony stimulating factor (GMCSF) on infarct size and left ventricular function, in the setting of acute myocardial infarction, with a protocol easily applicable in clinical practice. Ten pigs underwent left thoracotomy and left anterior descending coronary artery occlusion for 1 h, followed by reperfusion. After 50 min of arterial occlusion, the animals were randomly divided between treatment with placebo (Group 1) and subcutaneous GM-CSF (Group 2). The thoracotomy was closed and the animals recovered. In Group 2, GM-CSF, 20 microg/kg, was administered daily, 5 days/week, for 3 weeks. Echocardiograms were obtained at 5 and 28 days after acute myocardial infarction. At 30 days, infarct size, expressed as a percentage of the whole left ventricular mass, was measured. The white blood cell count increased from 13000 +/- 3338/ microl to 28700 +/- 4916/ microl (p = 0.001) in the GM-CSF-treated group. Infarct size was 7.8 +/- 6.1% in Group 1 vs 7.5 +/- 7.7% in Group 2 (ns). Similarly, no significant difference was observed between the 2 study groups in any of the echocardiographic measurements made at 28 days. Subcutaneous GMCSF administered during the early post acute myocardial infarction period neither decreased infarct size nor improved left ventricular function. Other protocols for mobilization of stem cells and their concentration in the injured area should be developed to combine efficacy and clinical applicability.