Early-outgrowth of endothelial progenitor cells can function as antigen-presenting cells

Blood-Derived Progenitor Cells Are Depleted in Older Adults with Cognitive Impairment: A Role for Vascular Resilience?

BACKGROUND

Depletion of blood-derived progenitor cells, including so called "early endothelial progenitor cells", has been observed in individuals with early stage Alzheimer's disease relative to matched older control subjects. These findings could implicate the loss of angiogenic support from hematopoietic progenitors or endothelial progenitors in cognitive dysfunction.

OBJECTIVE

To investigate links between progenitor cell proliferation and mild levels of cognitive dysfunction.

METHODS

We conducted in vitro studies of blood-derived progenitor cells using blood samples from sixty-five older adults who were free of stroke or dementia. Peripheral blood mononuclear cells from venous blood samples were cultured in CFU-Hill media and the number of colony forming units were counted after 5 days in vitro. Neuropsychological testing was administered to all participants.

RESULTS

Fewer colony forming units were observed in samples from older adults with a Clinical Dementia Rating global score of 0.5 versus 0. Older adults whose samples developed fewer colony forming units exhibited worse performance on neuropsychological measures of memory, executive functioning, and language ability.

CONCLUSION

These data suggest blood progenitors may represent a vascular resilience marker related to cognitive dysfunction in older adults.

Endothelial progenitor cells in peripheral blood may serve as a biological marker to predict severe acute pancreatitis

AIM

To investigate the significance of endothelial progenitor cells (EPCs) in predicting severe acute pancreatitis (SAP).

METHODS

We recruited 71 patients with acute pancreatitis (AP) and excluded 11 of them; finally, cases of mild acute pancreatitis (MAP) (n = 30) and SAP (n = 30), and healthy volunteers (n = 20) were internalized to investigate levels of EPCs, C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), fibrinogen (FIB) and white blood cells (WBC) in peripheral blood.

RESULTS

The levels of TNF-α, WBC, FIB and CRP were higher both in SAP and MAP cases than in healthy volunteers (P < 0.05, all). Interestingly, the level of EPCs was higher in SAP than MAP (1.63% ± 1.47% vs 6.61% ± 4.28%, P < 0.01), but there was no significant difference between the MAP cases and healthy volunteers (1.63% ± 1.47% vs 0.55% ± 0.54%, P > 0.05). Receiver operating characteristics curve (ROC) showed that EPCs, TNF-α, CRP and FIB were significantly associated with SAP, especially EPCs and CRP were optimal predictive markers of SAP. When the cut-off point for EPCs and CRP were 2.26% and 5.94 mg/dL, the sensitivities were 90.0% and 73.3%, and the specificities were 83.3% and 96.7%. Although, CRP had the highest specificity, and EPCs had the highest sensitivity and highest area under the curve value (0.93).

CONCLUSION

Data suggest that EPCs may be a new biological marker in predicting SAP.

Disrupted Endothelial Cell Layer and Exposed Extracellular Matrix Proteins Promote Capture of Late Outgrowth Endothelial Progenitor Cells

Late outgrowth endothelial progenitor cells (LO-EPC) possess a high proliferative potential, differentiate into vascular endothelial cells (EC), and form networks, suggesting they play a role in vascular repair. However, due to their scarcity in the circulation there is a requirement for ex vivo expansion before they could provide a practical cell therapy and it is currently unclear if they would home and engraft to an injury site. Using an in vitro flow system we studied LO-EPC under simulated injury conditions including EC activation, ischaemia, disrupted EC integrity, and exposed basement membrane. Perfused LO-EPC adhered to discontinuous EC paracellularly at junctional regions between adjacent cells under shear stress 0.7 dyn/cm(2). The interaction was not adhesion molecule-dependent and not enhanced by EC activation. LO-EPC expressed high levels of the VE-Cadherin which may explain these findings. Ischaemia reperfusion injury decreased the interaction with LO-EPC due to cell retraction. LO-EPC interacted with exposed extracellular matrix (ECM) proteins, fibronectin and vitronectin. The interaction was mediated by integrins α5β3, αvβ1, and αvβ3. This study has demonstrated that an injured local environment presents sufficient adhesive signals to capture flow perfused LO-EPC in vitro and that LO-EPC have properties consistent with their potential role in vascular repair.

Inflammatory environment and oxidized LDL convert circulating human proangiogenic cells into functional antigen-presenting cells

The function of human circulating PACs has been described extensively. However, little focus has been placed on understanding how these cells differ in their functions in the presence of microenvironments mimicking vascular inflammation. We hypothesized that exposure to proinflammatory cytokines or the oxLDL, an autoantigen abundant in advanced atherosclerotic plaques, converts PACs into immune-modulating/proinflammatory cells. Hence, we examined the effect of oxLDL and inflammatory stimuli on their phenotype by use of a functional genomics model based on secretome and whole genome transcriptome profiling. PACs obtained from culturing a PBMC fraction in angiogenic medium were primed with DC differentiation cytokines and then exposed to proinflammatory cytokines or oxLDL. Under these conditions, PACs converted into APCs, expressed maturation markers CD80 and CD83, and showed an increased up-regulation of CD86. APCcy and APCox induced a robust T cell BrdU incorporation. Despite a similar ability to induce lymphocyte proliferation, APCcy and APCox differed for the secretory pathway and mRNA expression. Analysis of the differentially expressed genes identified 4 gene "clusters," showing reciprocal modulation in APCcy vs. APCox, justifying, according to functional genomics analyses, a different putative function of the cells in antigen processing. Together, these data show that treatment with inflammatory cytokines or oxLDL converts human PAC phenotypes and functions into that of APCs with similar lymphocyte-activating ability but distinct maturation degree and paracrine functions.

Late-outgrowth endothelial progenitors from patients with coronary artery disease: endothelialization of confluent stromal cell layers

Patients with coronary artery disease (CAD) are the primary candidates to receive small-diameter tissue-engineered blood vessels (TEBVs). Peripheral blood derived endothelial progenitor cells (EPCs) from CAD patients (CAD EPCs) represent a minimally invasive source of autologous cells for TEBV endothelialization. We have previously shown that human CAD EPCs are highly proliferative and express many of the hallmarks of mature and healthy endothelial cells; however, their behavior on stromal cells that comprise the media of TEBVs has not yet been evaluated. Primary CAD EPCs or control human aortic endothelial cells (HAECs) were seeded over confluent, quiescent layers of human smooth muscle cells (SMCs) using a direct co-culture model. The percent coverage, adhesion strength, alignment under flow and generation of flow-induced nitric oxide of the seeded CAD EPCs were compared to that of HAECs. The integrin-binding profile of CAD EPCs was also evaluated over a layer of confluent, quiescent SMCs. Direct comparison of our CAD EPC results to analogous co-culture studies with cord blood EPCs show that both types of blood-derived EPCs are viable options for endothelialization of TEBVs.

A reappraisal of the role of circulating (progenitor) cells in the pathobiology of diabetic complications

Traditionally, the development of diabetic complications has been attributed to the biochemical pathways driving hyperglycaemic cell damage, while reparatory mechanisms have been long overlooked. A more comprehensive view of the balance between damage and repair suggests that an impaired regenerative capacity of bone marrow (BM)-derived cells strongly contributes to defective re-endothelisation and neoangiogenesis in diabetes. Although recent technological advances have redefined the biology and function of endothelial progenitor cells (EPCs), interest in BM-derived vasculotropic cells in the setting of diabetes and its complications remains high. Several circulating cell types of haematopoietic and non-haematopoietic origin are affected by diabetes and are potentially involved in the pathobiology of chronic complications. In addition to classical EPCs, these include circulating (pro-)angiogenic cells, polarised monocytes/macrophages (M1 and M2), myeloid calcifying cells and smooth muscle progenitor cells, having disparate roles in vascular biology. In parallel with the study of elusive progenitor cell phenotypes, it has been recognised that diabetes induces a profound remodelling of the BM stem cell niche. The alteration of circulating (progenitor) cells in the BM is now believed to be the link among distant end-organ complications. The field is rapidly evolving and interest is shifting from specific cell populations to the complex network of interactions that orchestrate trafficking of circulating vasculotropic cells.

Late outgrowth endothelial progenitor cells engineered for improved survival and maintenance of function in transplant-related injury

Chronic allograft vasculopathy (CAV) is a major cause of organ transplant failure that responds poorly to treatment. Endothelial activation, dysfunction and apoptosis contribute to CAV, whereas strategies for protecting endothelium and maximizing endothelial repair may diminish it. Late outgrowth endothelial progenitor cells (LO-EPC) can home to areas of injury and integrate into damaged vessels, implying a role in vascular repair; however, in an allograft, LO-EPC would be exposed to the hazardous microenvironment associated with transplant-related ischaemia reperfusion (I/R) injury and persistent inflammation. We evaluated the in vitro effect of I/R injury and the proinflammatory cytokine tumour necrosis factor (TNF)-α on LO-EPC phenotype and function. We show that LO-EPC are intrinsically more tolerant than mature EC to I/R injury induced apoptosis, maintaining their proliferative, migratory and network formation capacity. Under inflammatory conditions, LO-EPC were activated and released higher levels of inflammatory cytokines, upregulated adhesion molecule expression, and were more susceptible to apoptosis. Lentiviral vector-mediated overexpression of the protective gene A20 in LO-EPC maintained their angiogenic phenotype and function, and protected them against TNF-α-mediated apoptosis, reducing ICAM-1 expression and inflammatory cytokine secretion. Administration of ex vivo modified LO-EPC overexpressing A20 might effect vascular repair of damaged allografts and protect from CAV.

Distribution of exogenous endothelial progenitor cells in a rat model of hepatoma and their impact on liver cancer formation

AIM: To investigate the role of endothelial progenitor cells (EPCs) in the formation of liver cancer and to explore the possibility of using EPCs as a delivery vehicle for the treatment of liver cancer.

METHODS: Isolated and cultured EPCs were labeled with DAPI in vitro. Sprague-Dawley rats were divided into three groups: control group, model group, and EPC group. The model group and EPC group were intraperitoneally injected with diethylnitrosamine (DEN) to induce liver cancer, while the control group was injected with saline. Rats of the EPC group were further divided into three subgroups and intravenously injected with 1 mL of low (1 × 10⁵/150 μL), medium (2 × 10⁵/150 μL), and high (4 × 10⁵/150 μL) concentrations of EPCs-DAPI suspension, respectively, while the control group and model group were injected with equal volume of saline. At weeks 4, 6 and 8, rats were killed to take liver tissue samples to detect the expression of EPCs markers CD34, CD133, and KDR, and serum samples to measure the levels of ALT, AST, and AFP. EPCs-DAPI-positive area (PA) was quantified using the Imagepro plus image analysis software.

RESULTS: Positive expression of cell surface markers CD34, CD133, and KDR could be detected on cultured cells after 7 days of culture. Serum ALT, AST, and AFP differed significantly between the low-concentration EPC group and model group at week 4, between the medium-concentration EPC group and model group at week 6, and between the high-concentration EPC group and model group at week 8 (all P < 0.01). Positive DAPI was detected in all the EPC groups, and the positive rate of DAPI was dependent on the concentration of injected EPCs and injection duration. PA was significantly different among rats injected with different concentrations of EPCs at all time points (all P < 0.05), but showed no significant differences among rats injected with the same concentration of EPCs at different time points (all P > 0.05).

CONCLUSION: EPCs affect liver function in the rat model of liver cancer in a concentration- and time-dependent manner. EPCs in the liver can promote the formation of liver cancer. EPCs have a tropism to liver cancer in vivo.

Anti-angiogenic active immunotherapy: a new approach to cancer treatment

Tumor angiogenesis plays an important role in tumor growth, aggression and metastasis. Many molecules have been demonstrated as positive regulators of angiogenesis, including vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), and others. In recent years, significant progress has been made in the research on anti-angiogenic strategies for tumor therapies. In this review, anti-angiogenic active immunotherapies for tumors based on vaccination with xenogeneic homologous molecules and non-xenogeneic homologous molecules are discussed.

Biologic properties of endothelial progenitor cells and their potential for cell therapy

Recent studies indicate that portions of ischemic and tumor neovasculature are derived by neovasculogenesis, whereby bone marrow (BM)-derived circulating endothelial progenitor cells (EPCs) home to sites of regenerative or malignant growth and contribute to blood vessel formation. Recent data from animal models suggest that a variety of cell types, including unfractionated BM mononuclear cells and those obtained by ex vivo expansion of human peripheral blood or enriched progenitors, can function as EPCs to promote tissue vasculogenesis, regeneration, and repair when introduced in vivo. The promising preclinical results have led to several human clinical trials using BM as a potential source of EPCs in cardiac repair as well as ongoing basic research on using EPCs in tissue engineering or as cell therapy to target tumor growth.