Granulocyte colony-stimulating factor and stem cell factor improve contractile reserve of the infarcted left ventricle independent of restoring muscle mass

Human cardiac progenitor cell activation and regeneration mechanisms: exploring a novel myocardial ischemia/reperfusion in vitro model

BACKGROUND

Numerous studies from different labs around the world report human cardiac progenitor cells (hCPCs) as having a role in myocardial repair upon ischemia/reperfusion (I/R) injury, mainly through auto/paracrine signaling. Even though these cell populations are already being investigated in cell transplantation-based clinical trials, the mechanisms underlying their response are still poorly understood.

METHODS

To further investigate hCPC regenerative process, we established the first in vitro human heterotypic model of myocardial I/R injury using hCPCs and human-induced pluripotent cell-derived cardiomyocytes (hiPSC-CMs). The co-culture model was established using transwell inserts and evaluated in both ischemia and reperfusion phases regarding secretion of key cytokines, hiPSC-CM viability, and hCPC proliferation. hCPC proteome in response to I/R was further characterized using advanced liquid chromatography mass spectrometry tools.

RESULTS

This model recapitulates hallmarks of I/R, namely hiPSC-CM death upon insult, protective effect of hCPCs on hiPSC-CM viability (37.6% higher vs hiPSC-CM mono-culture), and hCPC proliferation (approximately threefold increase vs hCPCs mono-culture), emphasizing the importance of paracrine communication between these two populations. In particular, in co-culture supernatant upon injury, we report higher angiogenic functionality as well as a significant increase in the CXCL6 secretion rate, suggesting an important role of this chemokine in myocardial regeneration. hCPC whole proteome analysis allowed us to propose new pathways in the hCPC-mediated regenerative process, including cell cycle regulation, proliferation through EGF signaling, and reactive oxygen species detoxification.

CONCLUSION

This work contributes with new insights into hCPC biology in response to I/R, and the model established constitutes an important tool to study the molecular mechanisms involved in the myocardial regenerative process.

Granulocyte colony-stimulating factor therapy for stem cell mobilization following anterior wall myocardial infarction: the CAPITAL STEM MI randomized trial

BACKGROUND

Small studies have yielded divergent results for administration of granulocyte colony-stimulating factor (G-CSF) after acute myocardial infarction. Adequately powered studies involving patients with at least moderate left ventricular dysfunction are lacking.

METHODS

Patients with left ventricular ejection fraction less than 45% after anterior-wall myocardial infarction were treated with G-CSF (10 μg/kg daily for 4 days) or placebo. After initial randomization of 86 patients, 41 in the placebo group and 39 in the G-CSF group completed 6-month follow-up and underwent measurement of left ventricular ejection fraction by radionuclide angiography.

RESULTS

Baseline and 6-week mean ejection fraction was similar for the G-CSF and placebo groups: 34.8% (95% confidence interval [CI] 32.6%-37.0%) v. 36.4% (95% CI 33.5%-39.2%) at baseline and 39.8% (95% CI 36.2%-43.4%) v. 43.1% (95% CI 39.2%-47.0%) at 6 weeks. However, G-CSF therapy was associated with a lower ejection fraction at 6 months relative to placebo (40.8% [95% CI 37.4%-44.2%] v. 46.0% [95% CI 42.7%-44.3%]). Both groups had improved left ventricular function, but change in left ventricular ejection fraction was lower in patients treated with G-CSF than in those who received placebo (5.7 [95% CI 3.4-8.1] percentage points v. 9.2 [95% CI 6.3-12.1] percentage points). One or more of a composite of several major adverse cardiac events occurred in 8 patients (19%) within each group, with similar rates of target-vessel revascularization.

INTERPRETATION

In patients with moderate left ventricular dysfunction following anterior-wall infarction, G-CSF therapy was associated with a lower 6-month left ventricular ejection fraction but no increased risk of major adverse cardiac events. Future studies of G-CSF in patients with left ventricular dysfunction should be monitored closely for safety.

TRIAL REGISTRATION

ClinicalTrials.gov, no. NCT00394498.

Minimally invasive cell-seeded biomaterial systems for injectable/epicardial implantation in ischemic heart disease

Myocardial infarction (MI) is characterized by heart-wall thinning, myocyte slippage, and ventricular dilation. The injury to the heart-wall muscle after MI is permanent, as after an abundant cell loss the myocardial tissue lacks the intrinsic capability to regenerate. New therapeutics are required for functional improvement and regeneration of the infarcted myocardium, to overcome harmful diagnosis of patients with heart failure, and to overcome the shortage of heart donors. In the past few years, myocardial tissue engineering has emerged as a new and ambitious approach for treating MI. Several left ventricular assist devices and epicardial patches have been developed for MI. These devices and acellular/cellular cardiac patches are employed surgically and sutured to the epicardial surface of the heart, limiting the region of therapeutic benefit. An injectable system offers the potential benefit of minimally invasive release into the myocardium either to restore the injured extracellular matrix or to act as a scaffold for cell delivery. Furthermore, intramyocardial injection of biomaterials and cells has opened new opportunities to explore and also to augment the potentials of this technique to ease morbidity and mortality rates owing to heart failure. This review summarizes the growing body of literature in the field of myocardial tissue engineering, where biomaterial injection, with or without simultaneous cellular delivery, has been pursued to enhance functional and structural outcomes following MI. Additionally, this review also provides a complete outlook on the tissue-engineering therapies presently being used for myocardial regeneration, as well as some perceptivity into the possible issues that may hinder its progress in the future.

Early use of granulocyte colony stimulating factor improves survival in a rabbit model of chronic myocardial ischemia

BACKGROUND

Granulocyte colony stimulating factor (G-CSF) improves the survival of animals with myocardial infarction by inducing bone marrow stem cell mobilization and homing to infarcted areas. However, its precise mechanisms and direct effects on the ischemic myocardium remain unclear. In this study we investigated the direct effects and mechanisms of G-CSF in a rabbit model of chronic myocardial ischemia.

METHODS

Myocardial ischemia models were created by partial ligation of the left anterior descending coronary artery in Japanese white male rabbits. Rabbits were subcutaneously injected with 10 μg/kg of G-CSF (G-CSF group) or saline (control group) for 6 days after myocardial ischemia. Direct effects of G-CSF were analyzed by immunohistochemistry and terminal dUTP nick end-labeling (TUNEL).

RESULTS

Rabbits in the G-CSF group exhibited 75% survival compared to 40% in the control group (p<0.05). Immunohistochemistry of the ischemic myocardium showed increased homing of CD34+ cells on day 7 post-surgery and more vessels on day 28 post-surgery by anti-von Willebrand factor staining in the G-CSF group compared with the control group. Furthermore, an increased percentage of CD34+ cells were observed in peripheral blood and upregulation of vascular endothelial growth factor expression in ischemic tissue in the G-CSF group compared with the control group. TUNEL showed that the apoptotic index in the ischemic myocardium decreased in the G-CSF group compared with the control group on day 28 post-surgery.

CONCLUSIONS

In addition to increasing stem cell mobilization and homing to ischemic myocardium, G-CSF treatment after myocardial ischemia improves survival by accelerating neovascularization and reducing apoptosis.

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 × 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.

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.

Postmyocardial infarct remodeling and heart failure: potential contributions from pro- and antiaging factors

Myocardial infarction and adverse postinfarct remodeling in older persons lead to poor outcome and need greater understanding of the contributions of age-related factors on abnormal cardiac function and management. In this perspective, how normal aging processes could contribute to the events of post-myocardial infarction and remodeling is reviewed. Post-myocardial infarction and remodeling involve cardiomechanical factors and neurohormonal response. Many factors prevent or accelerate aging including immunosenescence, recruitment and regeneration of stem cells, telomere shortening, oxidative damage, antiaging hormones klotho and melatonin, nutrition, and Sirtiun protein family, and these factors could affect post-MI remodeling and heart failure. Interest in stem cell repair of myocardial infarcts to mitigate post-MI remodeling needs more information on aging of stem cells, and potential effects on stem cell use in infarct repair. Integrating genomics and proteomics methods may help find clinically novel therapy in the management of post-MI remodeling and heart failure in aged individuals.

Evaluation of the efficacy of granulocyte colony-stimulating factor for the treatment of experimental myocardial destruction in mice

We studied the effects of recombinant granulocytic CSF on heart remodeling in BALB/c mice after cryodestruction. Administration of granulocytic CSF was started 1 day after cryodestruction (subcutaneously, 10 μg/kg/day, for 4 days). As early as after the first injection, leukocytosis in the peripheral blood started to develop, leukocyte count peaked on days 4-6 and returned to normal on day 14. Treatment with granulocytic CSF significantly increased the content of progenitor cells in the bone marrow and led to rapid development of the inflammatory reaction and myocardium infiltration with mononuclear cells. Injections of granulocytic CSF did not reduce scar area, but provided significantly less pronounced heart hypertrophy, which attests to its better functional properties. By day 30 after cryodestruction, control animals and animals receiving granulocytic CSF exhibited similar morphological picture at the site of damage. Thus, our regimen of granulocytic CSF administration produced a mobilizing effect on bone marrow progenitor cells and postinfarction heart remodeling. Direct effects of granulocytic CSF on the heart have to be established for its use in the treatment of myocardial infarction.

Effects of granulocyte-colony-stimulating factor on progenitor cell mobilization and heart perfusion and function in normal mice

BACKGROUND AIMS

Mobilization of stem cells and progenitor cells from the bone marrow (BM) into the peripheral blood (PB) by granulocyte-colony-stimulating factor (G-CSF) is being investigated for cardiac regeneration in ischemic heart disease. However, hematopoietic (HPC), mesenchymal (MPC) and endothelial (EPC) progenitor mobilization have not been optimized and the effect of G-CSF on myocardial perfusion and cardiac function in a normal heart has never been studied.

METHODS

Normal mice were injected daily for 1-10 days with subcutaneous recombinant human G-CSF. PB and BM were evaluated for HPC and EPC by flow cytometry and HPC and MPC by hematopoietic (CFU-GM) and mesenchymal (CFU-F) colony assays. Echocardiography, microSPECT imaging, cardiac catheterization and immunohistochemistry were performed in mice treated for 10 days.

RESULTS

HPC and CFU-GM in PB peaked after 2 days, CFU-F after 4 days and EPC after 3 days. Thereafter, while HPC temporally decreased before showing a second peak, EPC remained detectable only at low levels. In BM, hematopoietic stem cells (HSC) and CFU-GM did not increase much overall but peaked twice on days 2 and 7. EPC (peak on day 7) production increased in the BM, but CFU-F formation declined considerably after day 2. G-CSF enhanced myocardial perfusion and vascularization but impaired hemodynamic performance of the heart through apparently increased ventricular wall rigidity.

CONCLUSIONS

G-CSF induces the mobilization of HPC, EPC and CFU-F progenitors in PB according to very different patterns, and has a significant impact on perfusion and function of the normal heart.

Improving regenerating potential of the heart after myocardial infarction: factor-based approach

The emerging evidence that the heart has the potential to regenerate, albeit not ideally, has stimulated considerable interest in the field of cardiac regenerative medicine. Several lines of research demonstrated that factor-based therapy is feasible and effective, whether it is used independently or as an adjunct to cell therapy. The ultimate goal of the factor-based approach is to improve the regenerating potential of the heart as a means to treat patients with cardiovascular disease. This article reviews recent approaches involving factor-based therapy for cardiac repair and regeneration including some of the advantages of this type of therapy as well as some of the hurdles that must be overcome before this therapeutic approach becomes a standard part of clinical medicine.

The effects of G-CSF-induced mobilization of progenitor cells are limited by ADMA

OBJECTIVE

Progenitor cells (PC) are thought to induce angiogenesis, and thereby, PC may help to improve ventricular performance in patients with ischemic heart disease (IHD). However, mobilization of progenitor cells by application of G-CSF gives inconsistent clinical effects. The aim of the present study was to assess pathophysiologic effects of progenitor cell mobilization.

METHODS AND RESULTS

PC levels (CD34+/CD117+) were counted in 8 patients with severe coronary heart disease and angina pectoris symptoms refractory to conventional therapy during G-CSF treatment (5 μg/kg/d) on days 2, 5, 8, at the end of hospitalization (day 10-12) and after 142±33 days of follow-up. Levels of asymmetric dimethylarginine (ADMA; inhibitor of eNOS) and symmetric dimethylarginine (SDMA) were determined at each occasion and correlated with leukocyte count, systemic nitrite levels, myeloperoxidase (MPO) expression in leukocytes, and urine levels of 8-iso-prostaglandin F2α. Isolated CD34+ cells and endothelial cell cultures were used for functional experiments. G-CSF therapy induced leukocytosis and a rise in CD34+ cell levels. Amounts of MPO positive leukocytes and ADMA levels increased significantly during the treatment phase. ADMA levels correlated to MPO activity (r=0.78; p=0.001) and were inversely related to nitrate levels. In contrast, 8-iso-prostaglandin F2α and amounts of SDMA did not change. Culturing endothelial cells in the presence of myeloperoxidase caused an increase in endothelial ADMA synthesis, which was prevented by application of the antioxidant trolox.

CONCLUSIONS

Leukocytosis associated with increased MPO activity during G-CSF therapy appears to be responsible for the systemic release of ADMA, which impairs eNOS activity. Thus, increased MPO and ADMA levels seem to counteract the potential beneficial effects of PC mobilization.

Cytokine treatment improves parenchymal and vascular damage of salivary glands after irradiation

PURPOSE

During radiotherapy for head and neck cancer, co-irradiation (IR) of salivary glands results in acute and often lifelong hyposalivation. Recently, we showed that bone marrow-derived cells (BMC) can partially facilitate postradiation regeneration of the mouse submandibular gland. In this study, we investigate whether optimized mobilization of BMCs can further facilitate regeneration of radiation-damaged salivary glands.

EXPERIMENTAL DESIGN

Salivary glands of mice reconstituted with eGFP+ bone marrow cells were irradiated with a single dose of 15 Gy. One month later, BMCs were mobilized using granulocyte colony-stimulating factor (G-CSF) or the combination of FMS-like tyrosine kinase-3 ligand, stem cell factor, and G-CSF (termed F/S/G) as mobilizing agents. Salivary gland function and morphology were evaluated at 90 days post-IR by measuring the saliva flow rate, the number of acinar cells, and the functionality of the vasculature.

RESULTS

Compared with G-CSF alone, the combined F/S/G treatment mobilized a 10-fold higher number and different types of BMCs to the bloodstream and increased the number of eGFP+ cells in the irradiated submandibular gland from 49% to 65%. Both treatments reduced radiation-induced hyposalivation from almost nothing in the untreated group to approximately 20% of normal amount. Surprisingly, however, F/S/G treatment resulted in significant less damage to submandibular blood vessels and induced BMC-derived neovascularization.

CONCLUSIONS

Post-IR F/S/G treatment facilitates regeneration of the submandibular gland and ameliorates vascular damage. The latter is partly due to BMCs differentiating in vascular cells but is likely to also result from direct stimulation of existing blood vessel cells.

Treatment with granulocyte colony stimulating factor is associated with improvement in endothelial function

PRIMARY OBJECTIVE

Granulocyte-colony stimulating factor (G-CSF) is used for the mobilization of bone marrow and endothelial progenitor cells, though G-CSF-induced inflammation may cause endothelial dysfunction. We examined the effects of G-CSF on endothelium, C-reactive protein (CRP), tumour necrosis factor-alpha (TNF-alpha) and anti-inflammatory cytokines namely interleukin 10 (IL-10).

RESEARCH DESIGN

We studied 60 women with breast cancer, who were randomized to either subcutaneous G-CSF (5 microg/kg), o.d. for 5 days after adjuvant chemotherapy (n = 40) or placebo (n = 20).

EXPERIMENTAL INTERVENTIONS

We measured flow-mediated dilatation (FMD%) of the brachial artery by ultrasonography, CRP, TNF-alpha, IL-10 and the ratio TNF-alpha/ IL-10 blood levels before, 2-h and 5-days after the G-CSF or placebo treatment.

MAIN OUTCOMES AND RESULTS

There was a greater increase of FMD, IL-10 and reduction of TNF-alpha/ IL-10, 2 h and 5 days after the G-CSF treatment compared to placebo. Although, CRP and TNF-alpha were higher, TNF-alpha/IL-10 was lower at the end of G-CSF treatment compared to placebo. Improvement of FMD was related to changes of IL-10 and TNF-alpha/IL-10.

CONCLUSIONS

Treatment with G-CSF improves endothelial function in vivo, possibly by shifting the balance between the pro- and anti-inflammatory cytokines.

Improvement of the breaking strength of wound by combined treatment with recombinant human G-CSF, recombinant human M-CSF, and a TGF-beta1 receptor kinase inhibitor in rat skin

Effective doses of ionizing radiation during preoperative radiotherapy occasionally cause wound complications after subsequent surgery. The authors attempted to accelerate radiation-impaired wound healing in animal models. Recombinant human granulocyte colony-stimulating factor (rhG-CSF), recombinant human macrophage colony-stimulating factor (rhM-CSF), and an inhibitor of transforming growth factor (TGF)-beta1 receptor kinase, SB431542, were injected s.c. into a full-thickness incisional wound site in the dorsal skin of rats after local irradiation of X-ray (30 Gy). Wound healing of irradiated skin was assessed using the breaking strength of the wound and histological analyses. The impaired wound healing in irradiated skin was found to be associated with impaired mobilization of bone marrow-derived cells and enhanced expression of TGF-beta1 mRNA. The breaking strength of the wound in the irradiated skin was approximately one-eighth of that in the non-irradiated skin; however, following combined treatment with the above three compounds the breaking strength increased to approximately one-half of that in the non-irradiated skin. Histological analysis of the wounded skin revealed an increase in formation of collagen fibers and the panniculus carnosus following the combined treatment. Moreover, the increased breaking strength was associated with an increase in a subpopulation of fibrocytes (collagen I/ED1 double positive cells). These findings suggested that a combined treatment with rhG-CSF, rhM-CSF, and SB431542 is promising as a means of improving radiation-impaired wound healing.

Quantitation of myocardial borderzone using reconstructive 3-D echocardiography after chronic infarction in rats: incremental value of low-dose dobutamine

Myocardial remodeling determines the degree of left ventricular dysfunction and mortality after transmural chronic myocardial infarction (CMI). Noninvasive characterization and quantitation of myocardial borderzone and collagenous scar are therefore parameters of clinical interest. The aims of this study were (i) to measure accuracy of reconstructive 3-D echocardiography (3DE) in scar and myocardial borderzone size assessment and (ii) to investigate the incremental value of low-dose dobutamine stress. 3DE was performed in 14 immunodeficient rats (rnu-rnu, 180-200 g) with anterior CMI 25 d after coronary ligation. Briefly, consecutive parallel short-axis cineloops were obtained electrocardiogram-gated starting from base to the apex. Morphology (mass, surface) and function (contractility, contractile reserve) of different compartments were assessed and correlated with 3-D histomorphometry. Histology was done using picrosirius red for collagen staining. 3DE left ventricular mass correlated closely with histomorphometry (y = 0.89x + 155, p < 0.0001, r = 0.80). Hypo- and akinetic myocardial surface correlated well with borderzone myocardium (y = 0.34x + 17, p = 0.009, r = 0.62) and collagenous scar (y = 1.9x + 4.4, p < 0.0001, r = 0.79), respectively. Extent of abnormal wall motion was closely related to borderzone and scar tissue area (y = 0.82x + 7, p < 0.0001, r = 0.77). 3DE quantitation of borderzone myocardium, but not collagenous scar, was more closely correlated to histomorphometry during inotropic stimulation. Global contractile reserve is positively associated with the size of myocardial borderzone. Regional contractile reserve of borderzone myocardium is not negatively associated with its collagen content. 3DE allows precise quantitation of myocardial borderzone and identification of transmural scar tissue noninvasively. Assessment of contractile reserve improves characterization and estimation of myocardial borderzone after CMI.

Chemokine-mobilized adult stem cells; defining a better hematopoietic graft

Stem cell research is currently focused on totipotent stem cells and their therapeutic potential, however adult stem cells, while restricted to differentiation within their tissue or origin, also have therapeutic utility. Transplantation with bone marrow hematopoietic stem cells (HSC) has been used for curative therapy for decades. More recently, alternative sources of HSC, particularly those induced to exit marrow or mobilize to peripheral blood by G-CSF, have become the most widely used hematopoietic graft and show significant superiority to marrow HSC. The chemokine/chemokine receptor axis also mobilizes HSC that occurs more rapidly than with G-CSF. In mice, the HSC and progenitor cells (HPC) mobilized by the CXCR2 receptor agonist GRObeta can be harvested within minutes of administration and show significantly lower levels of apoptosis, enhanced homing to marrow, expression of more activated integrin receptors and superior repopulation kinetics and more competitive engraftment than the equivalent cells mobilized by G-CSF. These characteristics suggest that chemokine axis-mobilized HSC represent a population of adult stem cells distinct from those mobilized by G-CSF, with superior therapeutic potential. It remains to be determined if the chemokine mobilization axis can be harnessed to mobilize other populations of unique adult stem cells with clinical utility.

Stem cell mobilization by granulocyte-colony-stimulating factor in acute myocardial infarction: lessons from the REVIVAL-2 trial

Experimental studies and early-phase clinical trials suggest that mobilization of bone marrow stem cells by granulocyte-colony-stimulating factor (G-CSF) can be used to improve cardiac regeneration after acute myocardial infarction (AMI). In order to more fully evaluate this intervention in patients with AMI, we conducted the Regenerate Vital Myocardium by Vigorous Activation of Bone Marrow Stem Cells (REVIVAL-2) clinical trial. Following successful reperfusion by percutaneous coronary intervention for AMI, patients were randomly assigned to receive a subcutaneous daily dose of 10 microg/kg G-CSF or placebo for 5 days. Treatment with G-CSF produced a significant mobilization of stem cells. After 4-6 months the reduction in infarct size from baseline, as determined by technetium-99-labeled single-photon-emission CT, did not differ significantly between the G-CSF group and the placebo group. Furthermore, the improvement in left ventricular ejection fraction, as assessed by late-enhancement MRI, did not differ significantly between the two groups. G-CSF treatment did not increase the risk of adverse clinical events and did not promote restenosis. Our trial demonstrates that stem cell mobilization by G-CSF does not improve infarct size, left ventricular function, or coronary restenosis in patients with AMI who have had successful mechanical reperfusion.

Granulocyte-colony stimulating factor administration after myocardial infarction in a porcine ischemia-reperfusion model: functional and pathological effects of dose timing

BACKGROUND

Acute MI results in cardiomyocyte death, left ventricular (LV) dysfunction and adverse remodeling. The use of growth factors may prevent this. The aim of this study was to assess early and delayed administration of granulocyte colony-stimulating factor (G-CSF) in a porcine model of myocardial infarction (MI) and reperfusion.

METHODS

MI was induced by balloon occlusion followed by reperfusion. There were 3 groups: Control (n = 11), Early (n = 17), and Delayed treatment (n = 8). The Early group received G-CSF 10 microg/kg/d every other day for 20 days beginning immediately. The Delayed group received G-CSF 10 microg/kg/d daily for 10 days beginning on day 5. Magnetic resonance imaging was performed on days 5 and 56. LV end-diastolic volumes (EDV), end-systolic volumes, ejection fraction, expansion index, sphericity index, thinning ratio, and infarct mass were calculated. Histology was analyzed at 56 days.

RESULTS

At 56 days the change in EDV was 53% less in the Early (p = 0.005) and 24% greater in the Delayed (p = NS) group versus Control. The Delayed group also showed a 60% increase in normalized infarct mass (p = 0.055) and an 88% increase in expansion index (p = 0.003). Both groups had significantly less capillary density in the infarct border zone. The Delayed also had decreased arteriolar density in the mid scar.

CONCLUSIONS

Early treatment with G-CSF after MI decreases ventricular dilatation, while delayed treatment has a deleterious effect on LV remodeling. This may be related to changes in myocardial vascularity. The effects of G-CSF therapy and its dose timing help to elucidate the results of recent human trials.

The effect of granulocyte colony stimulating factor on regional and global myocardial function in the porcine infarct model

BACKGROUND

Stem cell therapy has been shown to attenuate the reduction of left ventricular function following myocardial infarction. Most studies have utilized either a direct injection or intra-coronary infusion of cells, but cytokine mobilization of stem cells in the murine model of acute myocardial infarction has been reported to induce similar improvement in cardiac function.

METHODS

An antero-apical infarction was induced in swine by balloon occlusion, followed by the daily administration of granulocyte colony stimulating factor (G-CSF) or placebo for 5 days. We used left ventricular angiograms and 2D echocardiograms to assess global function, and 3D echocardiograms to assess regional function prior to infarction, immediately following infarction, and at 8 weeks. Histologic evaluation was performed after sacrifice at 8 weeks.

RESULTS

There was no significant difference in early or late post-infarction left ventricular ejection fraction or in myocardial histology between the two groups. Following G-CSF therapy, however, 3D echocardiography demonstrated that the regional ejection fractions of the infarcted segments showed a 50.3% improvement in the G-CSF pigs compared to a 7.4% deterioration in the untreated pigs (p=0.005).

CONCLUSIONS

Global left ventricular ejection fraction remained unchanged, and there is no histologic evidence for infarct attenuation following G-CSF infusion in the porcine infarct-reperfusion model. There was recovery of regional function in the infarcted segment in the G-CSF pigs. These data suggest that bone marrow mobilization in larger species has limited potential as a therapy designed to replace infarcted myocardium or to improve overall cardiac function, although further studies are needed to examine regional effect in the infarct area.

Cardiac repair--fact or fancy?

Patients with ischemic cardiomyopathy have a poor prognosis despite all pharmacological, interventional and surgical treatment modalities currently applied. Heart transplantation remains the ideal treatment for this group of patients but the scarcity of donors hinders its widespread application. The autologous transplantation of stem cells (SCs) for cardiac repair is emerging as a new therapy for patients with myocardial dysfunction early after an acute infarction or ischemic cardiomyopathy. The rationale of this novel method is the enhancement of the repair mechanisms achieved by tissue-specific and circulating stem/progenitor cells. SCs assist naturally occurring myocardial repair by contributing to increased myocardial perfusion and contractile performance especially in the setting of acute myocardial infarction (AMI), but also in patients with chronic ischemic heart failure and advanced, diffuse coronary artery disease. The exact mechanism of their action has not been fully elucidated. Few studies continue to suggest a formation of few new contractile tissue. The majority if investigators believe that these cells do not persist long in the myocardium but that they secrete vascular growth and other cardioprotective factors.

Actions and therapeutic potential of G-CSF and GM-CSF in cardiovascular disease

Despite their names, the cytokines granulocyte- and granulocyte-macrophage-colony stimulating factor (G-CSF and GM-CSF respectively) have actions far beyond simply stimulating the proliferation of neutrophil and monocyte lineage cells. A comprehensive body of evidence now exists demonstrating that G-CSF and GM-CSF effectively mobilize bone-marrow-derived progenitor cells into the peripheral circulation. These mobilized progenitor cells can be conveniently harvested for use in reconstituting bone marrow by transplantation after myelo-ablative treatment of hematological malignancies. In addition, much evidence has recently emerged to suggest that these cytokines may have multiple direct and indirect beneficial cardiovascular effects--including neovascularization of ischemic myocardium and reducing the extent of myocardial damage after infarction. Based on this knowledge and a strong safety record in hematological applications, a number of early clinical trials have evaluated the use of G-CSF or GM-CSF in patients with both acute and chronic myocardial ischemia. Although the interpretation of these trials is complicated by heterogeneity in study design, small patient numbers and methodological concerns related to appropriate selection and blinding of patients, the results of ongoing larger phase II/III trials should soon be available to determine if these agents will be useful additions to the cardiovascular armamentarium.

Angiogenic cells can be rapidly mobilized and efficiently harvested from the blood following treatment with AMD3100

Circulating endothelial progenitor cells (EPCs) are thought to contribute to angiogenesis following vascular injury, stimulating interest in their ability to mediate therapeutic angiogenesis. However, the number of EPCs in the blood is low, limiting endogenous repair, and a method to rapidly mobilize EPCs has not been reported. In this study, healthy donors were mobilized sequentially with the CXCR4 antagonist, AMD3100, and G-CSF. The number of EPCs and circulating angiogenic cells (CACs) in the blood and pheresis product was determined and the angiogenic capacity of each cell population assessed. Compared with baseline, treatment with AMD3100 or G-CSF increased the number of blood CACs 10.0-fold +/- 4.4-fold and 8.8-fold +/- 3.7-fold, respectively. The number of EPCs in the blood increased 10.2-fold +/- 3.3-fold and 21.8-fold +/- 5.4-fold, respectively. On a percell basis, CACs harvested from G-CSF-mobilized blood displayed increased in vivo angiogenic potential compared with AMD3100-mobilized CACs. Mobilized EPCs displayed a greater proliferative capacity than EPCs isolated from baseline blood. Both CACs and EPCs were efficiently harvested by leukapheresis. Cryopreserved CACs but not EPCs retained functional activity after thawing. These data show that AMD3100 is a potent and rapid mobilizer of angiogenic cells and demonstrate the feasibility of obtaining and storing large numbers of angiogenic cells by leukapheresis.