Use of granulocyte-colony stimulating factor during acute myocardial infarction to enhance bone marrow stem cell mobilization in humans: clinical and angiographic safety profile

Early onset of aging phenotype in vascular repair by Mas receptor deficiency

Aging is associated with impaired vascular repair following ischemic insult, largely due to reparative dysfunctions of progenitor cells. Activation of Mas receptor (MasR) was shown to reverse aging-associated vasoreparative dysfunction. This study tested the impact of MasR-deficiency on mobilization and vasoreparative functions with aging. Wild type (WT) or MasR-deficient mice (MasR^-/- or MasR^+/-) at 12-14 weeks (young) or middle age (11-12 months) (MA) were used in the study. Mobilization of lineage-negative, Sca-1-positive cKit-positive (LSK) cells in response to G-CSF or plerixafor was determined. Hindlimb ischemia (HLI) was induced by femoral artery ligation. Mobilization and blood flow recovery were monitored post-HLI. Radiation chimeras were made by lethal irradiation of WT or MasR^-/- mice followed by administration of bone marrow cells from MasR^-/- or WT mice, respectively. Nitric oxide (NO) generation by stromal-derived factor-1α (SDF) and mitochondrial reactive oxygen species (mitoROS) levels were determined by flow cytometry. Effect of A779 treatment on mobilization, blood flow recovery, and NO and ROS levels were determined in young WT and MasR^+/- mice. Circulating LSK cells in basal or in response to plerixafor or G-CSF or in response to ischemic injury were lower in MasR^-/- mice compared to the WT. Responses in MasR^+/- mice were similar to the WT at young age but at the middle age, impairments were observed. Impaired mobilization to ischemia or G-CSF was rescued in WT → MasR^-/- chimeras. NO levels were lower and mitoROS were higher in MasR^-/- LSK cells compared to WT cells. A779 precipitated dysfunctions in young-MasR^+/- mice similar to that observed in MA-MasR^+/-, and this accompanied decreased NO generation by SDF and enhanced mitoROS levels. This study shows that mice at MA do not exhibit vasoreparative dysfunction. Either partial or total loss of MasR precipitates advanced-aging phenotype likely due to lack of NO and oxidative stress.

Targeting Angiotensin-Converting Enzyme-2/Angiotensin-(1-7)/Mas Receptor Axis in the Vascular Progenitor Cells for Cardiovascular Diseases

Bone marrow-derived hematopoietic stem/progenitor cells are vasculogenic and play an important role in endothelial health and vascular homeostasis by participating in postnatal vasculogenesis. Progenitor cells are mobilized from bone marrow niches in response to remote ischemic injury and migrate to the areas of damage and stimulate revascularization largely by paracrine activation of angiogenic functions in the peri-ischemic vasculature. This innate vasoprotective mechanism is impaired in certain chronic clinical conditions, which leads to the development of cardiovascular complications. Members of the renin-angiotensin system-angiotensin-converting enzymes (ACEs) ACE and ACE2, angiotensin II (Ang II), Ang-(1-7), and receptors AT1 and Mas-are expressed in vasculogenic progenitor cells derived from humans and rodents. Ang-(1-7), generated by ACE2, is known to produce cardiovascular protective effects by acting on Mas receptor and is considered as a counter-regulatory mechanism to the detrimental effects of Ang II. Evidence has now been accumulating in support of the activation of the ACE2/Ang-(1-7)/Mas receptor pathway by pharmacologic or molecular maneuvers, which stimulates mobilization of progenitor cells from bone marrow, migration to areas of vascular damage, and revascularization of ischemic areas in pathologic conditions. This minireview summarizes recent studies that have enhanced our understanding of the physiology and pharmacology of vasoprotective axis in bone marrow-derived progenitor cells in health and disease. SIGNIFICANCE STATEMENT: Hematopoietic stem progenitor cells (HSPCs) stimulate revascularization of ischemic areas. However, the reparative potential is diminished in certain chronic clinical conditions, leading to the development of cardiovascular diseases. ACE2 and Mas receptor are key members of the alternative axis of the renin-angiotensin system and are expressed in HSPCs. Accumulating evidence points to activation of ACE2 or Mas receptor as a promising approach for restoring the reparative potential, thereby preventing the development of ischemic vascular diseases.

Effects of granulocyte colony‑stimulating factor on rabbit carotid and porcine heart models of chronic obliterative arterial disease

Previous studies suggest that granulocyte colony‑stimulating factor (G‑CSF) can promote bone marrow derived progenitor cells to mediate cardiovascular repair, potentially reversing mechanical dysfunction in chronic ischaemic heart disease and post myocardial infarction. Two models were used in the present study both using a surgical ameroid constrictor to induce arterial stenosis. The first model used the carotid artery of rabbits. They were divided into high fat diet (inducing atherosclerosis) or normal fat diet (control) groups. Each was subdivided into surgical exposure group without constrictor, ameroid constrictor receiving normal saline or receiving G‑CSF 15 µg/kg/day. Endothelial markers of endothelial nitric oxide synthase and endothelin 1 were increased by the use of ameroid constrictor in both atherosclerotic and non‑atherosclerotic mice, however were not further altered by G‑CSF. Scanning electron microscopy indicated that ameroid constrictor application altered endothelial morphology from an oval shape to a round shape and this was more prominent in the atherosclerotic compared with the non‑atherosclerotic group. G‑CSF injection increased the number of endothelial cells in all groups. The second model used the left coronary artery of pigs. They were equally divided into following groups, receiving normal saline (control), G‑CSF 2.5 µg/kg/day (low dose), 5 µg/kg/day (medium dose) and 10 µg/kg/day (high dose) for 5 days. G‑CSF at a low or high dose worsened intimal hyperplasia however at a medium dose improved it. In conclusion, G‑CSF had no effect in a rabbit carotid artery model of atherosclerosis. Its effects on the porcine heart were dose‑dependent; arterial disease worsened at a low or high dose, but improved at a medium dose.

Post-MI treatment with G-CSF and EPO-liposome with SLX repairs infarcted myocardium through EPCs mobilization and activation of prosurvival signals in rabbits

We investigated whether combination therapy of G-CSF and erythropoietin (EPO)-liposome with Siaryl Lewis X (SLX) is more cardioprotective than G-CSF or EPO-liposome with SLX alone. For the purpose of generating myocardial infarction (MI), rabbits underwent 30 minutes of coronary occlusion and 14 days of reperfusion. We administered saline (control group, i.v.,), G-CSF (G group, 10 μg/kg/day × 5 days, i.c., starting at 24 hours after reperfusion), EPO-liposome with SLX (LE group, i.v., 2500 IU/kg EPO containing liposome with SLX, immediately after reperfusion), and G-CSF + EPO-liposome with SLX (LE + G group) to the rabbits. The MI size was the smallest in the LE+G group (14.7 ± 0.8%), and smaller in the G group (22.4 ± 1.5%) and LE group (18.5 ± 1.1%) than in the control group (27.8 ± 1.5%). Compared with the control group, the cardiac function and remodeling of the G, LE, and LE + G groups were improved, and LE + G group tended to show the best improvement. The number of CD31-positive microvessels was the greatest in the LE + G group, greater in the G and LE groups than in the control group. Higher expressions of phosphorylated (p)-Akt and p-ERK were observed in the ischemic area of the LE and LE + G groups. The number of CD34+/CXCR4+ cells was significantly higher in the G and LE + G groups. The cardiac SDF-1 was more expressed in the G and LE + G groups. In conclusion, Post-MI combination therapy with G-CSF and EPO-liposome with SLX is more cardioprotective than G-CSF or EPO-liposome with SLX alone through EPCs mobilization, neovascularization, and activation of prosurvival signals.

Acute Myocardial Infarction, Cardioprotection, and Muse Cells

Acute myocardial infarction (AMI) is a common cause of morbidity and mortality worldwide. Severe MI leads to heart failure due to a marked loss of functional cardiomyocytes. First-line treatment for AMI is to reperfuse the occluded coronary artery by PCI as soon as possible. Besides PCI, there are several therapies to reduce the infarct size and improve the cardiac function and remodeling. These are drug therapies such as pharmacological pre- and postconditioning, cytokine therapies, and stem cell therapies. None of these therapies have been clinically developed as a standard treatment for AMI. Among many cell sources for stem cell therapies, the Muse cell is an endogenous non-tumorigenic pluripotent stem cell, which is able to differentiate into cells of all three germ layers from a single cell, suggesting that the Muse cell is a potential cell source for regenerative medicine. Endogenous Muse cell dynamics in the acute phase plays an important role in the prognosis of AMI patients; AMI patients with a higher number of Muse cells in the peripheral blood in the acute phase show more favorable improvement of the cardiac function and remodeling in the chronic phase, suggesting their innate reparative function for the heart. Intravenously administered exogenous Muse cells engrafted preferentially and efficiently to infarct border areas via the S1P-S1PR2 axis and differentiated spontaneously into working cardiomyocytes and vessels, showed paracrine effects, markedly reduced the myocardial infarct size, and delivered long-lasting improvement of the cardiac function and remodeling for 6 months. These findings suggest that Muse cells are reparative stem cells, and thus their clinical application is warranted.

Granulocyte Colony-Stimulating Factor and Its Potential Application for Skeletal Muscle Repair and Regeneration

Granulocyte colony-stimulating factor (G-CSF) was originally discovered in the context of hematopoiesis. However, the identification of the G-CSF receptor (G-CSFR) being expressed outside the hematopoietic system has revealed wider roles for G-CSF, particularly in tissue repair and regeneration. Skeletal muscle damage, including that following strenuous exercise, induces an elevation in plasma G-CSF, implicating it as a potential mediator of skeletal muscle repair. This has been supported by preclinical studies and clinical trials investigating G-CSF as a potential therapeutic agent in relevant disease states. This review focuses on the growing literature associated with G-CSF and G-CSFR in skeletal muscle under healthy and disease conditions and highlights the current controversies.

Therapeutic Angiogenesis With Bone Marrow—Derived Stem Cells

Despite that advances in medical treatment and interventional procedures have reduced the mortality rate in patients with coronary artery disease, the number of patients with refractory myocardial ischemia and congestive heart failure is rapidly increasing. Experimental studies have demonstrated that bone marrow (BM) contains adult stem cells that can induce neovascularization and improve heart function in ischemic myocardium. Recent insights into the understanding of the mechanisms involved in proliferation, recruitment, mobilization, and incorporation of BM-derived stem cells into the myocardium and blood vessels have prompted development of cellular transplantation therapy for heart diseases refractory to conventional therapy. Initial preliminary clinical studies indicated potential clinical benefit of BM therapy in patients with acute myocardial infarction and chronic myocardial ischemia. Nevertheless, many obstacles remain, such as long-term safety and optimal timing and treatment strategies for BM cell therapy, and these issues need to be addressed in rationally designed, randomized clinical trials.

Impaired Mobilization of Vascular Reparative Bone Marrow Cells in Streptozotocin-Induced Diabetes but not in Leptin Receptor-Deficient db/db Mice

Diabetes is associated with impaired mobilization of bone marrow stem/progenitor cells that accelerate vascularization of ischemic areas. This study characterized mobilization of vascular reparative bone marrow progenitor cells in mouse models of diabetes. Age-matched control or streptozotocin (STZ)-induced diabetic, and db/db mice with lean-controls were studied. Mobilization induced by G-CSF, AMD3100 or ischemia was evaluated by flow cytometric enumeration of circulating Lin(-)Sca-1(+)cKit(+) (LSK) cells, and by colony forming unit (CFU) assay. The circulating WBCs and LSKs, and CFUs were reduced in both models with a shorter duration (10-12 weeks) of diabetes compared to their respective controls. Longer duration of STZ-diabetes (≥20 weeks) induced impairment of G-CSF- or AMD3100-mobilization (P < 0.01, n = 8). In db/db mice, mobilization by G-CSF or AMD3100 was either increased or unaffected (P < 0.05, n = 6 to 8). Proliferation, migration, and ischemia-induced mobilization, of LSK cells were impaired in both models. Leptin receptor antagonist, PESLAN-1, increased G-CSF- or AMD3100-mobilization of WBCs and LSKs, compared to the untreated. Leptin increased basal WBCs, decreased basal and AMD3100-mobilized LSK cells, and had no effect on G-CSF. These results suggest that mobilopathy is apparent in STZ-diabetes but not in db/db mice. Leptin receptor antagonism would be a promising approach for reversing diabetic bone marrow mobilopathy.

Trans-system mechanisms against ischemic myocardial injury

A mammalian organism possesses a hierarchy of naturally evolved protective mechanisms against ischemic myocardial injury at the molecular, cellular, and organ levels. These mechanisms comprise regional protective processes, including upregulation and secretion of paracrine cell-survival factors, inflammation, angiogenesis, fibrosis, and resident stem cell-based cardiomyocyte regeneration. There are also interactive protective processes between the injured heart, circulation, and selected remote organs, defined as trans-system protective mechanisms, including upregulation and secretion of endocrine cell-survival factors from the liver and adipose tissue as well as mobilization of bone marrow, splenic, and hepatic cells to the injury site to mediate myocardial protection and repair. The injured heart and activated remote organs exploit molecular and cellular processes, including signal transduction, gene expression, cell proliferation, differentiation, migration, mobilization, and/or extracellular matrix production, to establish protective mechanisms. Both regional and trans-system cardioprotective mechanisms are mediated by paracrine and endocrine messengers and act in coordination and synergy to maximize the protective effect, minimize myocardial infarction, and improve myocardial function, ensuring the survival and timely repair of the injured heart. The concept of the trans-system protective mechanisms may be generalized to other organ systems-injury in one organ may initiate regional as well as trans-system protective responses, thereby minimizing injury and ensuring the survival of the entire organism. Selected trans-system processes may serve as core protective mechanisms that can be exploited by selected organs in injury. These naturally evolved protective mechanisms are the foundation for developing protective strategies for myocardial infarction and injury-induced disorders in other organ systems.

Hematopoietic progenitors are required for proper development of coronary vasculature

RATIONALE

During embryogenesis, hematopoietic cells appear in the myocardium prior to the initiation of coronary formation. However, their role is unknown.

OBJECTIVE

Here we investigate whether pre-existing hematopoietic cells are required for the formation of coronary vasculature.

METHODS AND RESULTS

As a model of for hematopoietic cell deficient animals, we used Runx1 knockout embryos and Vav1-cre; R26-DTA embryos, latter of which genetically ablates 2/3 of CD45(+) hematopoietic cells. Both Runx1 knockout embryos and Vav1-cre; R26-DTA embryos revealed disorganized, hypoplastic microvasculature of coronary vessels on section and whole-mount stainings. Furthermore, coronary explant experiments showed that the mouse heart explants from Runx1 and Vav1-cre; R26-DTA embryos exhibited impaired coronary formation ex vivo. Interestingly, in both models it appears that epicardial to mesenchymal transition is adversely affected in the absence of hematopoietic progenitors.

CONCLUSION

Hematopoietic cells are not merely passively transported via coronary vessel, but substantially involved in the induction of the coronary growth. Our findings suggest a novel mechanism of coronary growth.

Paracrine mechanisms of mesenchymal stem cell-based therapy: current status and perspectives

Mesenchymal stem cells (MSCs) are one of a few stem cell types to be applied in clinical practice as therapeutic agents for immunomodulation and ischemic tissue repair. In addition to their multipotent differentiation potential, a strong paracrine capacity has been proposed as the principal mechanism that contributes to tissue repair. Apart from cytokine/chemokine secretion, MSCs also display a strong capacity for mitochondrial transfer and microvesicle (exosomes) secretion in response to injury with subsequent promotion of tissue regeneration. These unique properties of MSCs make them an invaluable cell type to repair damaged tissues/organs. Although MSCs offer great promise in the treatment of degenerative diseases and inflammatory disorders, there are still many challenges to overcome prior to their widespread clinical application. Particularly, their in-depth paracrine mechanisms remain a matter for debate and exploration. This review will highlight the discovery of the paracrine mechanism of MSCs, regulation of the paracrine biology of MSCs, important paracrine factors of MSCs in modulation of tissue repair, exosome and mitochondrial transfer for tissue repair, and the future perspective for MSC-based therapy.

Role of formyl peptide receptor 2 in homing of endothelial progenitor cells and therapeutic angiogenesis

Endothelial progenitor cells (EPCs) hold a great promise as a therapeutic mediator in treatment of ischemic disease conditions. The discovery of EPCs in adult blood has been a cause of significant enthusiasm in the field of endothelial cell research and numerous clinical trials have been expedited. After more than a decade of research in basic science and clinical applications, limitations and new strategies of EPC therapeutics have emerged. With various phenotypes, vague definitions, and uncertain distinction from hematopoietic cells, understanding EPC biology remains challenging. However, EPCs, still hold great hope for treatment of critical ischemic injury as low concern regarding safety can accelerate the clinical applications from basic findings. This review provides an introduction to EPC as cellular therapeutics, which highlights a recent finding that EPC homing was promoted through FPR2 signaling.

Clenbuterol plus granulocyte colony-stimulating factor regulates stem/progenitor cell mobilization and exerts beneficial effect by increasing neovascularization in rats with heart failure

BACKGROUND

Treatment of beta2-adrenergic receptor agonists with myeloid cytokines, such as granulocyte colony-stimulating factor (G-CSF) has been reported to enhance stem/progenitor cell mobilization and proliferation in ischemic myocardium. However, whether the combination therapy of G-CSF and clenbuterol (Clen) contributes to improved left ventricular (LV) function remains uncertain. We investigated whether this combination therapy induced bone marrow-derived stem/progenitor cell mobilization, neovascularization, and altered LV function after acute myocardial infarction (MI).

METHODS AND RESULTS

Following MI, rats were treated with single Clen, high-dose Clen, and G-CSF + Clen. We evaluated LV function and remodeling with the use of echocardiography in addition to hemodynamics 3 weeks after MI. Treatment with G-CSF + Clen increased (P < .05), compared with no treatment, LV ejection fraction 46 ± 3% vs 34 ± 2%, LV dP/dt 5,789 ± 394 mm Hg vs 4,503 ± 283 mm Hg, and the percentage of circulating CD34+ cells, appearing to correlate with improvements in LV function.

CONCLUSIONS

Combination therapy improved LV function 3 weeks after MI, suggesting that G-CSF + Clen might augment stem/progenitor cell migration, contributing to tissue healing. These data raise the possibility that enhancing endogenous bone marrow-derived stem/progenitor cell mobilization may be a new treatment for ischemic heart failure after MI.

Multicenter prospective nonrandomized controlled clinical trial to prove neurotherapeutic effects of granulocyte colony-stimulating factor for acute spinal cord injury: analyses of follow-up cases after at least 1 year

STUDY DESIGN

An open-labeled multicenter prospective nonrandomized controlled clinical trial.

OBJECTIVE

To confirm the feasibility of using granulocyte colony-stimulating factor (G-CSF) for treatment of acute spinal cord injury (SCI).

SUMMARY OF BACKGROUND DATA

We previously reported that G-CSF promotes functional recovery after compression-induced SCI in mice. On the basis of these findings, we conducted a multicenter prospective controlled clinical trial to assess the feasibility of G-CSF therapy for patients with acute SCI.

METHODS

The trial ran from August 2009 to March 2011, and included 41 patients with SCI treated within 48 hours of onset. Informed consent was obtained from all patients. After providing consent, patients were divided into 2 groups. In the G-CSF group (17 patients), G-CSF (10 μg/kg/d) was intravenously administered for 5 consecutive days, and in the control group (24 patients), patients were similarly treated except for the G-CSF administration. We evaluated motor and sensory functions using the American Spinal Cord Injury Association score and American Spinal Cord Injury Association impairment scale at 1 week, 3 months, 6 months, and 1 year after onset.

RESULTS

Only 2 patients did not experience American Spinal Cord Injury Association impairment scale improvement in the G-CSF group. In contrast, 15 patients in the control group did not experience American Spinal Cord Injury Association impairment scale improvement. In the analysis of increased American Spinal Cord Injury Association motor score, a significant increase in G-CSF group was detected from 1 week after the administration compared with the control group. After that, some spontaneous increase of motor score was detected in control group, but the significant increase in G-CSF group was maintained until 1 year of follow-up.

CONCLUSION

Despite the limitation that patient selection was not randomized, the present results suggest the possibility that G-CSF administration has beneficial effects on neurological recovery in patients with acute SCI.

LEVEL OF EVIDENCE

3.

Bioactive lipids and cationic antimicrobial peptides as new potential regulators for trafficking of bone marrow-derived stem cells in patients with acute myocardial infarction

Acute myocardial infarction (AMI) triggers mobilization of stem cells from bone marrow (BM) into peripheral blood (PB). Based on our observation that the bioactive sphingophospholipids, sphingosine-1 phosphate (S1P), and ceramide-1 phosphate (C1P) regulate trafficking of hematopoietic stem cells (HSCs), we explored whether they also direct trafficking of non-hematopoietic stem cells (non-HSCs). We detected a 3-6-fold increase in circulating CD34+, CD133+, and CXCR4+ lineage-negative (Lin-)/CD45- cells that are enriched in non-HSCs [including endothelial progenitors (EPCs) and very small embryonic-like stem cells (VSELs)] in PB from AMI patients (P<0.05 vs. controls). Concurrently, we measured a ∼3-fold increase in S1P and C1P levels in plasma from AMI patients. At the same time, plasma obtained at hospital admission and 6 h after AMI strongly chemoattracted human BM-derived CD34+/Lin- and CXCR4+/Lin- cells in Transwell chemotaxis assays. This effect of plasma was blunted after depletion of S1P level by charcoal stripping and was further inhibited by the specific S1P1 receptor antagonist such as W146 and VPC23019. We also noted that the expression of S1P receptor 1 (S1P1), which is dominant in naïve BM, is reduced after the exposure to S1P at concentrations similar to the plasma S1P levels in patients with AMI, thus influencing the role of S1P in homing to the injured myocardium. Therefore, we examined mechanisms, other than bioactive lipids, that may contribute to the homing of BM non-HSCs to the infarcted myocardium. Hypoxic cardiac tissue increases the expression of cathelicidin and β-2 defensin, which could explain why PB cells isolated from patients with AMI migrated more efficiently to a low, yet physiological, gradient of stromal-derived factor-1 in Transwell migration assays. Together, these observations suggest that while elevated S1P and C1P levels early in the course of AMI may trigger mobilization of non-HSCs into PB, cathelicidin and β-2 defensin could play an important role in their homing to damaged myocardium.

Granulocyte colony stimulating factor therapy for acute myocardial infarction

BACKGROUND

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).

OBJECTIVES

To assess the effects of stem cell mobilization following granulocyte colony stimulating factor therapy in patients with acute myocardial infarction.

SEARCH METHODS

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.

SELECTION CRITERIA

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.

DATA COLLECTION AND ANALYSIS

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.

MAIN RESULTS

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.

AUTHORS' CONCLUSIONS

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.

Ischemia/reperfusion injury promotes and granulocyte-colony stimulating factor inhibits migration of bone marrow-derived stem cells to endometrium

The endometrium is a dynamic tissue that undergoes repeated rounds of regeneration in each reproductive (estrous or menstrual) cycle. We have previously shown that bone marrow (BM)-derived stem cells engraft the endometrium in rodents and humans; however, it is not known if these cells contribute physiologically to uterine cyclic regeneration or alternatively are primarily involved in uterine repair in response to injury. Here we performed male-to-female BM transplant and tested the ability of uterine injury to recruit BM-derived cells to endometrium in the presence and absence of sex steroids. Uterine ischemia/reperfusion injury resulted in an ~2-fold increase in BM-derived stem cell recruitment to the endometrium. The effect was independent of sex steroids or the existence of an estrous cycle. BM-derived mesenchymal stem cells (MSCs) are involved in uterine repair after injury, but not the cyclic regeneration of the endometrium in the estrous/menstrual cycle. Granulocyte-colony stimulating factor (G-CSF) is used to increase BM mobilization for transplant and has been proposed as a means of mobilizing stem cells to the uterus. Here G-CSF treatment led to decreased BM engraftment of the uterus after injury, likely by favoring mobilization of hematopoietic stem cells over the MSCs. G-CSF is unlikely to be of benefit in repair of uterine injury in humans. Taken together, we demonstrate that ischemic injury drives BM MSC engraftment of the uterus, independent of estrous cycle, sex steroids, or G-CSF.

Epicardial progenitor cells in cardiac regeneration and neovascularisation

While cardiovascular diseases remain the major worldwide cause of mortality and morbidity, there is an urgent need to tackle the clinical and economic burden of heart failure. Since the mammalian heart is unable to adequately regenerate beyond early postnatal stages, individuals surviving acute myocardial infarction are at risk of heart failure. Understanding the embryonic mechanisms of vasculogenesis and cardiogenesis, as well as the mechanisms retained for regeneration in species such as the zebrafish, will inform on strategies for human myocardial repair. Due to their fundamental role in heart development, epicardium-derived cells (EPDCs) have emerged as a population with potential to restore myocardium and coronary vasculature. The ability to revive ordinarily dormant EPDCs lies in the identification of key molecular cues used in the embryo to orchestrate cardiovascular development. One such stimulatory factor, Thymosin β4 (Tβ4), restores the quiescent adult epicardium to its pluripotent embryonic state. Tβ4 treatment of infarcted hearts induces dramatic EPDC proliferation and formation of a network of perfused, functional vessels to enhance blood flow to the ischaemic myocardium. Moreover, Tβ4 facilitates an epicardial contribution of mature de novo cardiomyocytes, structurally and functionally coupled with resident myocardium, which may contribute towards the functional improvement of Tβ4-treated hearts post-MI.

Harnessing the mesenchymal stem cell secretome for the treatment of cardiovascular disease

The broad repertoire of secreted trophic and immunomodulatory cytokines produced by mesenchymal stem cells (MSCs), generally referred to as the MSC secretome, has considerable potential for the treatment of cardiovascular disease. However, harnessing this MSC secretome for meaningful therapeutic outcomes is challenging due to the limited control of cytokine production following their transplantation. This review outlines the current understanding of the MSC secretome as a therapeutic for treatment of ischemic heart disease. We discuss ongoing investigative directions aimed at improving cellular activity and characterizing the secretome and its regulation in greater detail. Finally, we provide insights on and perspectives for future development of the MSC secretome as a therapeutic tool.

Gene and cytokine therapy for heart failure: molecular mechanisms in the improvement of cardiac function

Despite significant advances in pharmacological and clinical treatment, heart failure (HF) remains a leading cause of morbidity and mortality worldwide. Many new therapeutic strategies, including cell transplantation, gene delivery, and cytokines or other small molecules, have been explored to treat HF. Recent advancement of our understanding of the molecules that regulate cardiac function uncover many of the therapeutic key molecules to treat HF. Furthermore, a theory of paracrine mechanism, which underlies the beneficial effects of cell therapy, leads us to search novel target molecules for genetic or pharmacological strategy. Gene therapy means delivery of genetic materials into cells to achieve therapeutic effects. Recently, gene transfer technology in the cardiovascular system has been improved and several therapeutic target genes have been started to examine in clinical research, and some of the promising results have been emerged. Among the various bioactive reagents, cytokines such as granulocyte colony-stimulating factor and erythropoietin have been well examined, and a number of clinical trials for acute myocardial infarction and chronic HF have been conducted. Although further research is needed in both preclinical and clinical areas in terms of molecular mechanisms, safety, and efficiency, both gene and cytokine therapy have a great possibility to open the new era of the treatment of HF.

Cotreatment with darbepoetin and granulocyte colony-stimulating factor is efficient to recruit proangiogenic cell populations in patients with acute myocardial infarction

To determine whether newer combination cytokine treatment with granulocyte colony-stimulating factor (G-CSF) and darbepoetin can improve efficacy of stem cell therapy, we evaluated safety and peripheral blood stem/progenitor cell (PBSC) mobilizing effects of combination cytokine in comparison with G-CSF alone in patients with acute myocardial infarction (AMI). We randomized 60 patients with AMI into two groups under 2:1 ratio; combination treatment with darbepoetin and G-CSF (n = 41: Combicytokine group) and the G-CSF alone (n = 19: G-CSF group). After coronary angioplasty, G-CSF was treated for 3 days with dose of 10 μg/kg/day in both groups. Only in the combicytokine group, additional single intravenous injection of 4.5 μg/kg of darbepoetin was administrated immediate after coronary angioplasty. Combination cytokine treatment was well tolerated as was G-CSF alone. PBSCs were obtained by apheresis for intracoronary infusion after completion of cytokine treatment and were analyzed by flow cytometry. The purity of proangiogenic cells was higher in combination cytokine group than the G-CSF group. Specifically, proportion of CD34(+)/KDR(+) endothelial progenitor cells, CD3(+)/CD31(+) angiogenic T cells and Tie2(+)/CXCR4(+) cells in apheresis products were higher in the combicytokine group. These meant that the combicytokine treatment recruited PBSCs in higher purity and fewer unwanted inflammatory cells than G-CSF alone in apheresis products. Combination treatment with darbepoetin and G-CSF is safe and more efficient to mobilize and recruit proangiogenic cells than G-CSF alone in patients with AMI. (

TRIAL REGISTRATION

www.ClinicalTrials. gov identifier: NCT00501917).

Neuroprotective therapy using granulocyte colony-stimulating factor for acute spinal cord injury: a phase I/IIa clinical trial

OBJECTIVE

Granulocyte colony-stimulating factor (G-CSF) is a cytokine that is clinically used to treat neutropenia. G-CSF also has non-hematopoietic functions and could potentially be used to treat neuronal injury. To confirm the safety and feasibility of G-CSF administration for acute spinal cord injury (SCI), we have initiated a phase I/IIa clinical trial of neuroprotective therapy using G-CSF.

METHODS

The trial included a total of 16 SCI patients within 48 h of onset. In the first step, G-CSF (5 μg/kg/day) was intravenously administered for 5 consecutive days to 5 patients. In the second step, G-CSF (10 μg/kg/day) was similarly administered to 11 patients. We evaluated motor and sensory functions of patients using the American Spinal Cord Injury Association (ASIA) score and ASIA impairment scale (AIS) grade.

RESULTS

In all 16 patients, neurological improvement was obtained after G-CSF administration. AIS grade increased by one step in 9 of 16 patients. A significant increase in ASIA motor scores was detected 1 day after injection (P < 0.01), and both light touch and pin prick scores improved 2 days after injection (P < 0.05) in the 10 μg group. No severe adverse effects were observed after G-CSF injection.

CONCLUSION

These results indicate that intravenous administration of G-CSF (10 μg/kg/day) for 5 days is essentially safe, and suggest that some neurological recovery may occur in most patients. We suggest that G-CSF administration could be therapeutic for patients with acute SCI.

Neuroprotective therapy using granulocyte colony-stimulating factor for patients with worsening symptoms of compression myelopathy, Part 1: a phase I and IIa clinical trial

OBJECTIVE

Based on the neuroprotective effects of granulocyte colony-stimulating factor (G-CSF) on experimental spinal cord injury, we initiated a clinical trial that evaluated the safety and efficacy of neuroprotective therapy using G-CSF for patients with worsening symptoms of compression myelopathy.

METHODS

We obtained informed consent from 15 patients, in whom the Japanese Orthopaedic Association (JOA) score for cervical myelopathy decreased two points or more during a recent 1-month period. G-CSF (5 or 10 μg/kg/day) was intravenously administered for five consecutive days. We evaluated motor and sensory functions of the patients and the presence of adverse events related to G-CSF therapy.

RESULTS

G-CSF administration suppressed the progression of myelopathy in all 15 patients. Neurological improvements in motor and sensory functions were obtained in all patients after the administration, although the degree of improvement differed among the patients. Nine patients in the 10-μg group (n=10) underwent surgical treatment at 1 month or later after G-CSF administration. In the 10-μg group, the mean JOA recovery rates 1 and 6 months after administration were 49.9±15.1 and 59.1±16.3%, respectively. On the day following the start of G-CSF therapy, the white blood cell count increased to more than 22,700 cells/mm3. It varied from 12,000 to 50,000 and returned to preadministration levels 3 days after completing G-CSF treatment. No serious adverse events occurred during or after treatment.

CONCLUSION

The results indicate that G-CSF administration at 10 μg/kg/day is safe for patients with worsening symptoms of compression myelopathy and may be effective for their neurological improvement.

Progenitor cell mobilization and recruitment: SDF-1, CXCR4, α4-integrin, and c-kit

Progenitor cell retention and release are largely governed by the binding of stromal-cell-derived factor 1 (SDF-1) to CXC chemokine receptor 4 (CXCR4) and by α4-integrin signaling. Both of these pathways are dependent on c-kit activity: the mobilization of progenitor cells in response to either CXCR4 antagonism or α4-integrin blockade is impaired by the loss of c-kit kinase activity; and c-kit-kinase inactivation blocks the retention of CXCR4-positive progenitor cells in the bone marrow. SDF-1/CXCR4 and α4-integrin signaling are also crucial for the retention of progenitor cells in the ischemic region, which may explain, at least in part, why clinical trials of progenitor cell therapy have failed to display the efficacy observed in preclinical investigations. The lack of effectiveness is often attributed to poor retention of the transplanted cells and, to date, most of the trial protocols have mobilized cells with injections of granulocyte colony-stimulating factor (G-CSF), which activates extracellular proteases that irreversibly cleave cell-surface adhesion molecules, including α4-integrin and CXCR4. Thus, the retention of G-CSF-mobilized cells in the ischemic region may be impaired, and the mobilization of agents that reversibly disrupt SDF-1/CXCR4 binding, such as AMD3100, may improve patient response. Efforts to supplement SDF-1 levels in the ischemic region may also improve progenitor cell recruitment and the effectiveness of stem cell therapy.

Therapeutic angiogenesis for myocardial ischemia revisited: basic biological concepts and focus on latest clinical trials

Therapeutic angiogenesis is based on the premise that the development of new blood vessels can be augmented by exogenous administration of the appropriate growth factors. Over the last years, successful preclinical studies and promising results of early clinical trials have created great excitement about the potential of therapeutic angiogenesis for patients with advanced ischemic heart disease. The authors provide an overview of the biology of angiogenesis, the basic characteristics of angiogenic factors, and the different routes of their delivery. They discuss experimental studies in animal models of myocardial ischemia and outline available clinical studies on therapeutic angiogenesis for myocardial ischemia. Related safety issues are also addressed followed by a critical perspective about the future of proangiogenic therapies for ischemic cardiovascular disorders. Despite the established proof of concept and reasonable safety, however, results of the latest trials on therapeutic angiogenesis for myocardial ischemia have provided inconsistent results and the definite means of inducing clinically useful therapeutic angiogenesis remain elusive. More studies are required to gain further insights into the biology of angiogenesis and address pharmacological limitations of current approaches of angiogenic therapy. The authors hope and envisage that in the not-too-distant future, these investigative efforts will lead to important new strategies for treatment of myocardial ischemic syndromes. Means of non-invasive individualized pharmacological therapeutic neovascularization may be the next major advance in the treatment of ischaemic heart disease.

Different clinical models of CD34 + cells mobilization in patients with cardiovascular disease

To test the role of necrosis, ischemia or both in bone marrow cells (BMC) mobilization in patients with cardiovascular disease. We studied three groups of patients: group 1, Iatrogenic Necrosis, with pure necrosis (28 patients undergoing transcatheter radiofrequency ablation); group 2, Ischemic Necrosis (30 patients with myocardial infarction); group 3, Pure Ischemia (24 patients with unstable angina). As control groups, we studied 27 patients with stable coronary artery disease (CAD), and 20 patients without CAD undergoing angiography for valvular diseases or cardiomiopathy. CD34 + cells and cytokines were evaluated at: T(0) (baseline), 48 h and 5, 7, 10, 14 days thereafter. We observed a significant increase of CD34 + cells at T(3) and T(4) only in Iatrogenic Necrosis and Ischemic Necrosis group. The peak of mobilization was observed ten days after the necrotic event (2.8 ± 1.4 vs. 5.9 ± 1.9 in the group 1, P = 0.03; and 3 ± 1.5 vs. 5.6 ± 2 in the group 2, P = 0.04; respectively). We found a good correlation between CD34 + and vascular endothelial growth factor (VEGF) and stromal derived factor (SDF-1α) peak values (r = 0.77 and r = 0.63, respectively). At multivariable analysis, myocardial necrosis (OR 3.5, 95%CI 2.2-4.2, P < 0.01), VEGF (OR 2, 95%CI 1.1-3, P = 0.01 as above versus below median value), and SDF-1α (OR 1.6, 95%CI 1.1-2.5, P = 0.02 as above versus below median value) emerged as independent predictors of C34 + cells increase. Myocardial necrosis with simultaneous elevation of VEGF and SDF-1α causes a significant CD34 + cells mobilization in patients with cardiovascular disease.

Hematopoietic cytokines for cardiac repair: mobilization of bone marrow cells and beyond

Hematopoietic cytokines, traditionally known to influence cellular proliferation, differentiation, maturation, and lineage commitment in the bone marrow, include granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor, stem cell factor, Flt-3 ligand, and erythropoietin among others. Emerging evidence suggests that these cytokines also exert multifarious biological effects on diverse nonhematopoietic organs and tissues. Although the precise mechanisms remain unclear, numerous studies in animal models of myocardial infarction (MI) and heart failure indicate that hematopoietic cytokines confer potent cardiovascular benefits, possibly through mobilization and subsequent homing of bone marrow-derived cells into the infarcted heart with consequent induction of myocardial repair involving multifarious mechanisms. In addition, these cytokines are also known to exert direct cytoprotective effects. However, results from small-scale clinical trials of G-CSF therapy as a single agent after acute MI have been discordant and largely disappointing. It is likely that cardiac repair following cytokine therapy depends on a number of known and unknown variables, and further experimental and clinical studies are certainly warranted to accurately determine the true therapeutic potential of such therapy. In this review, we discuss the biological features of several key hematopoietic cytokines and present the basic and clinical evidence pertaining to cardiac repair with hematopoietic cytokine therapy.

Myocardial blood flow and infarct size after CD133+ cell injection in large myocardial infarction with good recanalization and poor reperfusion: results from a randomized controlled trial

OBJECTIVE

Large acute ST-elevation myocardial infarction (STEMI) sometimes leaves extensive ischemic damage despite timely and successful primary angioplasty. This clinical picture of good recanalization with incomplete reperfusion represents a good model to assess the reparative potential of locally administered cell therapy. Thus, we conducted a randomized controlled trial aimed at evaluating the effect of intracoronary administration of CD133 stem cells on myocardial blood flow and function in this setting.

METHODS

Fifteen patients with large anterior STEMI, myocardial blush grade 0-1 and more than 50% ST-elevation recovery after optimal coronary recanalization (TIMI 3 flow) with stenting were randomly assigned to receive CD133 cells from either bone marrow (group A) or peripheral blood (group B), or to stay on drug therapy alone (group C). The cells were intracoronary injected within 10-14 days of STEMI. Infarct-related myocardial blood flow (MBF) was evaluated by NH positron emission tomography 2-5 days before cell administration and after 1 year.

RESULTS

MBF increased in the infarct area from 0.419 (0.390-0.623) to 0.544 (0.371-0.729) ml/min per g in group A, decreased from 0.547 (0.505-0.683) to 0.295 (0.237-0.472) ml/min per g in group B and only slightly changed from 0.554 (0.413-0.662) to 0.491 (0.453-0.717) ml/min per g in group C (A vs. C: P = 0.023; B vs. C: P = 0.066). Left ventricular volume tended to increase more in groups B and C than in group A, ejection fraction and wall motion score index remained stable in the three groups.

CONCLUSION

These findings support the hypothesis that intracoronary administration of bone marrow-derived, but not peripheral blood-derived CD133 cells 10-14 days after STEMI may improve long-term perfusion.

Current status of stem cell therapy in heart failure

Inspired by studies demonstrating the potential for new myocyte formation within adult mammalian hearts, an ongoing explosion of research is elucidating the biology of cardiac myogenesis and angiogenesis. Multiple lines of research suggest that disease-associated activation of endogenous cardiac repair processes are often insufficient to overcome the cell death resulting from myocardial infarction and chronic heart failure. In this context, this review highlights current evidence supporting endogenous cardiac repair mechanisms in human hearts, recent progress with clinical application of myocardial cell therapy, and complementary efforts to manipulate endogenous myocardial repair processes using a variety of tissue engineering strategies. The goal of this overview is to demonstrate that the insights and opportunities derived from each of these lines of inquiry are mutually complementary for ultimately achieving the goal of therapeutic cardiac regeneration.

The therapeutic potential of G-CSF in pressure overload induced ventricular reconstruction and heart failure in mice

In animal models of clinical entities causative of severe right and left ventricular (LV) pressure overload hypertrophy, increased density of the cellular microtubule network, through viscous loading of active myofilaments, causes contractile dysfunction that is normalized by microtubule depolymerization. In this study, 86 male mice were divided into seven groups. The transverse ascending aorta constriction (TAC) in six groups were performed in order to make heart failure model. Mice in each group were injected with G-CSF or/and telmisartan subcutaneously at different time respectively. Results showed that reduction in left ventricular volume and improved function persisted at 2 week, but recurrent dilatation at 4 weeks was associated with a loss of functional improvement. Compared with PBS group, the expression of VEGF protein and HIF-1 mRNA were significantly higher in mice injected with G-CSF or/and telmisartan (P<0.05). The expression of p53 mRNA, myocardial fibrosis and mortality were significantly lower in mice injected with G-CSF or/and telmisartan (P<0.05). It could be concluded that G-CSF can delay the progression of pressure overload induced ventricular reconstruction and heart failure in mice.

Secondary prevention of CAD with ACE inhibitors: a struggle between life and death of the endothelium

Angiotensin-converting enzyme (ACE) inhibitors improve outcomes in patients with coronary artery disease (CAD), heart failure, and hypertension. This short review examines clinical evidence for such effects and the underlying mechanism of action. One potential mode of action for ACE inhibitors in CAD is blood pressure reduction. However, recent data suggest that the effects of ACE inhibitors on the endothelium may also be relevant in attenuating the progression of atherosclerosis. In CAD, chronic overexpression of tissue ACE disrupts the angiotensin II/bradykinin balance with a net result of endothelial dysfunction, mainly due to an increased rate of apoptosis. An imbalance between endothelial apoptosis (death) and its renewal from the bone marrow (life) causes discontinuity of the endothelial layer, favoring the initiation and progression of a biochemical sequence that leads to atherosclerosis, plaque rupture, and eventually acute coronary syndromes. There is clinical and experimental evidence that ACE inhibition improves the life and death cycle of the endothelium. By restoring the bradykinin/angiotensin II balance, ACE inhibition reduces the rate of endothelial apoptosis and experimental results suggest that ACE inhibition can also improve the production and mobilization of endothelial progenitor cells from bone marrow. We report our experience in this context with perindopril.

Stem and progenitor cell-based therapy in ischaemic heart disease: promise, uncertainties, and challenges

In the absence of effective endogenous repair mechanisms after cardiac injury, cell-based therapies have rapidly emerged as a potential novel therapeutic approach in ischaemic heart disease. After the initial characterization of putative endothelial progenitor cells and their potential to promote cardiac neovascularization and to attenuate ischaemic injury, a decade of intense research has examined several novel approaches to promote cardiac repair in adult life. A variety of adult stem and progenitor cells from different sources have been examined for their potential to promote cardiac repair and regeneration. Although early, small-scale clinical studies underscored the potential effects of cell-based therapy largely by using bone marrow (BM)-derived cells, subsequent randomized-controlled trials have revealed mixed results that might relate, at least in part, to differences in study design and techniques, e.g. differences in patient population, cell sources and preparation, and endpoint selection. Recent meta-analyses have supported the notion that administration of BM-derived cells may improve cardiac function on top of standard therapy. At this stage, further optimization of cell-based therapy is urgently needed, and finally, large-scale clinical trials are required to eventually proof its clinical efficacy with respect to outcomes, i.e. morbidity and mortality. Despite all promises, pending uncertainties and practical limitations attenuate the therapeutic use of stem/progenitor cells for ischaemic heart disease. To advance the field forward, several important aspects need to be addressed in carefully designed studies: comparative studies may allow to discriminate superior cell populations, timing, dosing, priming of cells, and delivery mode for different applications. In order to predict benefit, influencing factors need to be identified with the aim to focus resources and efforts. Local retention and fate of cells in the therapeutic target zone must be improved. Further understanding of regenerative mechanisms will enable optimization at all levels. In this context, cell priming, bionanotechnology, and tissue engineering are emerging tools and may merge into a combined biological approach of ischaemic tissue repair.

A multicenter, prospective, randomized, controlled trial evaluating the safety and efficacy of intracoronary cell infusion mobilized with granulocyte colony-stimulating factor and darbepoetin after acute myocardial infarction: study design and rationale of the 'MAGIC cell-5-combination cytokine trial'

Background

Bone marrow derived stem/progenitor cell transplantation after acute myocardial infarction is safe and effective for improving left ventricular systolic function. However, the improvement of left ventricular systolic function is limited. This study will evaluate novel stem/progenitor cell therapy with combination cytokine treatment of the long-acting erythropoietin analogue, darbepoetin, and granulocyte colony-stimulating factor (G-CSF) in patients with acute myocardial infarction.

Methods

The 'MAGIC Cell-5-Combination Cytokine Trial' is a multicenter, prospective, randomized, 3-arm, controlled trial with blind evaluation of the endpoints. A total of 116 patients will randomly receive one of the following three treatments: an intravenous darbepoetin infusion and intracoronary infusion of peripheral blood stem cells mobilized with G-CSF (n = 58), an intracoronary infusion of peripheral blood stem cells mobilized with G-CSF alone (n = 29), or conventional therapy (n = 29) at phase I. Patients with left ventricular ejection fraction < 45% at 6 months, in the patients who received stem cell therapy at phase I, will receive repeated cell therapy at phase II. The objectives of this study are to evaluate the safety and efficacy of combination cytokine therapy with erythropoietin and G-CSF (phase I) and repeated progenitor/stem cell treatment (phase II).

Discussion

This is the first study to evaluate the safety and efficacy of combination cytokine based progenitor/stem cell treatment.

Trial registration

http://www.ClinicalTrials.gov identifier: NCT00501917.

Beneficial effects of granulocyte-colony stimulating factor on small-diameter heparin immobilized decellularized vascular graft

Autologous recellularization of decellularized scaffolds is a promising challenge in the field of tissue-engineered vascular graft and could be boosted by endothelial progenitor cells (EPCs). The purpose of this study was to examine the effects of granulocyte-colony stimulating factor (G-CSF) treatment on this process. Heparin immobilized decellularized grafts were fabricated and implanted into 48 rats, of which 25 rats received G-CSF (50 ug/kg/day) for 14 days after operation (G-CSF group) and other 23 received saline serving as control. Five animals of each group were euthanized at 2 weeks for analysis of early graft endothelialization; whereas the rest were investigated by Doppler ultrasound to monitor the graft patency rate up to 6 months. After 14 days of G-CSF administration, the number of CD(34) (+)/CD(133) (+) progenitor cells was increased by 16.2 folds, and endothelial cell-specific immunostaining revealed an enhancement of early endothelialization in G-CSF group. After 6 months of implantation, the G-CSF treated grafts exhibited a significantly smaller hyperplastic neointima area compared with the controls, not only at midportion (0.38 ± 0.02 vs. 0.47 ± 0.07 mm(2), p < 0.0001), but also at distal anastomosis (0.42 ± 0.04 vs. 0.70 ± 0.13 mm(2), p < 0.0001). Moreover, G-CSF treated grafts had a higher patency rate compared with the control animals (19/20 vs. 12/18, p = 0.005). In conclusion, G-CSF-induced mobilization of circulating EPCs regenerated endothelium and inhibited neointimal hyperplasia of small-diameter heparinized decellularized vascular graft. This cytokine therapy may be a feasible strategy for the improvement of patency rate of the novel allogeneic graft.

Rebuilding the damaged heart: the potential of cytokines and growth factors in the treatment of ischemic heart disease

Cytokine therapy promises to provide a noninvasive treatment option for ischemic heart disease. Cytokines are thought to influence angiogenesis directly via effects on endothelial cells or indirectly through progenitor cell-based mechanisms or by activating the expression of other angiogenic agents. Several cytokines mobilize progenitor cells from the bone marrow or are involved in the homing of mobilized cells to ischemic tissue. The recruited cells contribute to myocardial regeneration both as a structural component of the regenerating tissue and by secreting angiogenic or antiapoptotic factors, including cytokines. To date, randomized, controlled clinical trials have not reproduced the efficacy observed in pre-clinical and small-scale clinical investigations. Nevertheless, the list of promising cytokines continues to grow, and combinations of cytokines, with or without concurrent progenitor cell therapy, warrant further investigation.

Granulocyte colony-stimulating factor attenuates oxidative stress-induced apoptosis in vascular endothelial cells and exhibits functional and morphologic protective effect in oxygen-induced retinopathy

Granulocyte colony-stimulating factor (G-CSF) is a known hematopoietic glycoprotein, and recent studies have revealed that G-CSF possesses other interesting properties. Oxidative stress is involved in many diseases, such as atherosclerosis, heart failure, myocardial infarction, Alzheimer disease, and diabetic retinopathy. This study was designed to examine whether G-CSF has a protective effect on endothelial cells against oxidative stress and to investigate whether G-CSF has a therapeutic role in ischemic vascular diseases. Expression of G-CSF (P < .01) and G-CSF receptor (P < .05) mRNA in human retinal endothelial cells (HRECs) was significantly up-regulated by oxidative stress. Treatment with 100 ng/mL G-CSF significantly reduced H(2)O(2)-induced apoptosis in HRECs from 61.7% to 41.4% (P < .05). Akt was phosphorylated in HRECs by G-CSF addition, and LY294002, a PI3K inhibitor, significantly attenuated the antiapoptotic effect of G-CSF (by 44.1%, P < .05). The rescue effect was also observed in human umbilical vein endothelial cells. In mouse oxygen-induced retinopathy model, G-CSF significantly reduced vascular obliteration (P < .01) and neovascular tuft formation (P < .01). G-CSF treatment also clearly rescued the functional and morphologic deterioration of the neural retina. A possibility of a novel therapeutic strategy for ischemic diseases through attenuating vascular regression using G-CSF was proposed.

Phases I-III Clinical Trials Using Adult Stem Cells

First randomized clinical trials have demonstrated that stem cell therapy can improve cardiac recovery after the acute phase of myocardial ischemia and in patients with chronic ischemic heart disease. Nevertheless, some trials have shown that conflicting results and uncertainties remain in the case of mechanisms of action and possible ways to improve clinical impact of stem cells in cardiac repair. In this paper we will examine the evidence available, analyze the main phase I and II randomized clinical trials and their limitations, discuss the key points in the design of future trials, and depict new directions of research in this fascinating field.