Targeted antagonism of CXCR4 mobilizes progenitor cells under investigation for cardiovascular disease

Impaired ability to grow colonies of endothelial stem cells could be the mechanism explaining the high cardiovascular morbidity and mortality of patients with depression

BACKGROUND

Subjects with depression are more prone to develop cardiovascular complications. Severity of depression is associated with higher rates of cardiovascular mortality and morbidity. Several mechanisms were suggested including accelerated atherosclerosis, alteration of the cardiac autonomic response with a decrease in heart rate variability. There is evidence that circulating endothelial progenitor cells (EPCs) are decreased in patients with major depression. Our hypothesis was that patients with depression would have an impaired ability to build colonies of EPCs.

METHODS

A prospective study enrolled twenty women with a diagnosis of major. All were not treated before for depression. Thirteen healthy age-matched women served as controls. All signed a consent form before recruitment to the study. Peripheral blood was drawn to build colonies of EPCs within 5 days. ELISA methods were used to measure levels of vascular cell adhesion molecule-1 (VCAM-1) and vascular endothelial growth factor (VEGF).

RESULTS

Twenty female patients with depression were recruited. The mean age was 43 ± 14 years (vs. controls 41 ± 11 years, P = 0.682), patients' average CFU-EPCs was 7 ± 8 colonies per well (controls 31 ± 11, P = 0.0001), VCAM-1 level was 121.7 ± 3.0 ng/ml (controls 119.3 ± 3.1 pg/ml, P = 0.037), VEGF level was 6.4 ± 0.2 pg/ml (controls 5.2 ± 0.5 pg/ml, P = 0.0001). An inverse correlation was found between VEGF level and EPCs' colonies (r  = -0.547, P < 0.001) and between age and CFU-EPCs (r = -0.576, P = 0.008).

CONCLUSIONS

We found that patients with major depression had high levels of VCAM-1 and VEGF. They also had a significant inhibition of EPCs' colonies. An inverse correlation was found between levels of VEGF and the ability to grow colonies of EPCs in culture.

Performance and safety of femoral central venous catheters in pediatric autologous peripheral blood stem cell collection

INTRODUCTION

Autologous peripheral blood hematopoietic progenitor cell collection (A-HPCC) in children typically requires placement of a central venous catheter (CVC) for venous access. There is scant published data regarding the performance and safety of femoral CVCs in pediatric A-HPCC.

METHODS

Seven-year, retrospective study of A-HPCC in pediatric patients collected between 2009 and January 2017. Inclusion criteria were an age ≤ 21 years and A-HPCC using a femoral CVC for venous access. Femoral CVC performance was examined by CD34 collection rate, inlet rate, collection efficiency (MNC-FE, CD34-FE), bleeding, flow-related adverse events (AE), CVC removal, and product sterility testing. Statistical analysis and graphing were performed with commercial software.

RESULTS

A total of 75/119 (63%) pediatric patients (median age 3 years) met study criteria. Only 16% of children required a CVC for ≥ 3 days. The CD34 collect rate and CD34-FE was stable over time whereas MNC-FE decreased after day 4 in 80% of patients. CD34-FE and MNC-FE showed inter- and intra-patient variability over time and appeared sensitive to plerixafor administration. Femoral CVC showed fewer flow-related AE compared to thoracic CVC, especially in pediatric patients (6.7% vs. 37%, P = 0.0005; OR = 0.12 (95%CI: 0.03-0.45). CVC removal was uneventful in 73/75 (97%) patients with hemostasis achieved after 20-30 min of pressure. In a 10-year period, there were no instances of product contamination associated with femoral CVC colonization.

CONCLUSION

Femoral CVC are safe and effective for A-HPCC in young pediatric patients. Femoral CVC performance was maintained over several days with few flow-related alarms when compared to thoracic CVCs.

Combination of endogenous neural stem cell mobilization and lithium chloride treatment for hydrocephalus following intraventricular hemorrhage

As there are multiple factors causing hydrocephalus subsequent to intraventricular hemorrhage (IVH), it is difficult to achieve the best treatment effect using a single drug alone. In the present study, the protective effect of combination treatment with granulocyte-colony stimulating factor (G-CSF) and lithium chloride against hydrocephalus after IVH was investigated. A total of 130 adult male Sprague-Dawley rats were divided into five groups, including the IVH control, G-CSF treatment, lithium chloride treatment, combination treatment and sham surgery groups. An IVH rat model was established in order to examine the effect of combination treatment on hydrocephalus incidence. A TUNEL assay was performed to detect neuronal apoptosis in the five groups. In addition, the protein expression levels of B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) were detected by western blot analysis. The differentiation of nerve cells in the brain tissue obtained from the five rat groups was also determined with double immunofluorescence staining. The results demonstrated that administration of G-CSF or lithium chloride alone was able to only partly relieve the incidence of hydrocephalus after IVH. By contrast, combination treatment with G-CSF and lithium chloride significantly attenuated the development of hydrocephalus following IVH. TUNEL assay showed that neuronal apoptosis was significantly reduced by the combination treatment with G-CSF and lithium chloride. Furthermore, the expression of Bcl-2 was upregulated, whereas Bax expression was downregulated in the combination treatment group. The results also detected the highest expression of BrdU/GFAP, BrdU/NeuN and BrdU/PSA-NCAM in the combination treatment group. In conclusion, the combination of endogenous neural stem cell mobilization (using G-CSF) and lithium chloride treatment resulted in highly reduced incidence of hydrocephalus after IVH by inhibiting neuronal apoptosis.

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.

Targeting stem cell niches and trafficking for cardiovascular therapy

Regenerative cardiovascular medicine is the frontline of 21st-century health care. Cell therapy trials using bone marrow progenitor cells documented that the approach is feasible, safe and potentially beneficial in patients with ischemic disease. However, cardiovascular prevention and rehabilitation strategies should aim to conserve the pristine healing capacity of a healthy organism as well as reactivate it under disease conditions. This requires an increased understanding of stem cell microenvironment and trafficking mechanisms. Engagement and disengagement of stem cells of the osteoblastic niche is a dynamic process, finely tuned to allow low amounts of cells move out of the bone marrow and into the circulation on a regular basis. The balance is altered under stress situations, like tissue injury or ischemia, leading to remarkably increased cell egression. Individual populations of circulating progenitor cells could give rise to mature tissue cells (e.g. endothelial cells or cardiomyocytes), while the majority may differentiate to leukocytes, affecting the environment of homing sites in a paracrine way, e.g. promoting endothelial survival, proliferation and function, as well as attenuating or enhancing inflammation. This review focuses on the dynamics of the stem cell niche in healthy and disease conditions and on therapeutic means to direct stem cell/progenitor cell mobilization and recruitment into improved tissue repair.

Bone marrow stem cells in clinical application: harnessing paracrine roles and niche mechanisms

The being of any individual throughout life is a dynamic process relying on the capacity to retain processes of self-renewal and differentiation, both of which are hallmarks of stem cells. Although limited in the adult human organism, regeneration and repair do take place in virtue of the presence of adult stem cells. In the bone marrow, two major populations of stem cells govern the dynamic equilibrium of both hemopoiesis and skeletal homeostasis; the hematopoietic and the mesenchymal stem cells. Recent cell based clinical trials utilizing bone marrow-derived stem cells as therapeutic agents have revealed promising results, while others have failed to display as such. It is therefore imperative to strive to understand the mechanisms by which these cells function in vivo, how their properties can be maintained ex-vivo, and to explore further their recently highlighted immunomodulatory and trophic effects.

CXCR4 in clinical hematology

Pharmacological manipulation of CXCR4 has proven clinically useful for mobilization of stem and progenitor cells and in several preclinical models of disease. It is a key component in the localization of leukocytes and stem cells. For patients with multiple myeloma and non-Hodgkin's Lymphoma, treatment with plerixafor, an inhibitor of CXCL12 binding to CXCR4, plus G-CSF mobilizes stem cells for autologous transplantation to a greater degree than the treatment with G-CSF alone, and in some cases when patients could not be mobilized with cytokines, chemotherapy, or the combination. Stem cells from healthy donors mobilized with single agent plerixafor have been used for allogeneic transplantation in acute myelogenous leukemia (AML) patients, although this is still in the early phase of clinical development. Plerixafor is also undergoing evaluation to mobilize tumor cells in patients with AML and chronic lymphocytic leukemia (CLL) to enhance the effectiveness of chemotherapy regimens. Plerixafor's effect on neutrophils may also restore circulating neutrophil counts to normal levels in patients with chronic neutropenias such as in WHIMs syndrome. Other areas where inhibition of CXCR4 may be useful based upon preclinical or clinical data include peripheral vascular disease, autoimmune diseases such as rheumatoid arthritis, pulmonary inflammation, and HIV.