Proangiogenic Cells Research Articles

Aspirin Affects Tumor Angiogenesis and Sensitizes Human Glioblastoma Endothelial Cells to Temozolomide, Bevacizumab, and Sunitinib, Impairing Vascular Endothelial Growth Factor-Related Signaling

Glioblastoma (GBM) is the most common and fatal human brain tumor, with the worst prognosis. The aberrant microenvironment, enhanced by the activation of proangiogenic mediators such as hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), and their downstream effectors, sustain GBM malignancy. Proangiogenic signaling represents an attractive chemotherapeutic target. Recent evidence suggests a therapeutic benefit from aspirin (acetylsalicylic acid, or ASA) intake in reducing risk and cancer progression. In the present study, human primary GBM-endothelial cells (ECs) were used to ascertain whether ASA could inhibit angiogenesis and improve cell sensitivity to drugs. The impact of ASA was observed by measuring cell viability, tube-like structure formation, migration, VEGF production, and proliferative, proangiogenic, and apoptotic modulators expression, such as HIF-1α/VEGF/vascular endothelial growth factor receptor/(VEGFR)-1/VEGFR-2, Ras/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase, phosphoinositide 3-kinase/AKT signaling axis, and Bcl-2-associated X protein/B-cell lymphoma 2 (BCL-2) ratio. Furthermore, we evaluated the effect of ASA alone or in combination with temozolomide (TMZ), bevacizumab (BEV), and sunitinib (SUN). Our data reported that ASA affected GBM-EC viability, tube-like structure formation, cell migration, and VEGF releasing in a dose-dependent manner and that combined treatments with TMZ, BEV, and SUN synergized to counteract proangiogenic cell ability. mRNA expression analysis displayed a marked effect of ASA in reducing VEGF, VEGFR-1, HIF-1α, RAS, mitogen-activated protein kinase kinase, AKT, and BCL-2, as well a combined anticancer effect of ASA together with TMZ, BEV, and SUN. Levels of HIF-1α, VEGFR-2, Bcl-2-associated X protein, and BCL-2 protein expression confirmed a positive trend. ASA and antiangiogenic therapies showed synergetic anticancer efficacy in human primary GBM-ECs. Thus, the combination of conventional chemotherapy with ASA may offer a new strategy to counteract tumor malignancy.

Association of growth-differentiation factor-15 with the number of circulating proangiogenic endothelial progenitor cells in patients with type 2 diabetes mellitus

The objective: to investigate the relationship between levels of growth differentiation factor-15 (GDF-15) and circulating number of endothelial progenitor cells (EPCs) with angiopoietin phenotypes: CD34+CD14+CD309+, and CD34+CD14+CD309+Tie2+ in patients with type 2 DM.
 Methods: The study was retrospectively involved 76 patients with type 2 DM aged 38 to 55 years and 30 healthy volunteers. Data collection included demographic and anthropometric information, hemodynamic performances and biomarkers of the diseases. Flow cytometry was used to determine EPCs' populations.
 Results: The levels of GDF-15 in peripheral blood of diabetics associated with age (r = 0.31, P = 0.044), high-sensitive C-reactive protein [hs-CRP] (r = 0.40, P = 0.001), smoking (r = 0.38, P = 0.001), body mass index [BMI] (r = 0.34, P = 0.001), LDL cholesterol (r = 0.28, P = 0.001), glycated hemoglobin [HbA1c] (r = -0.28, P = 0.001), number of CV risk factors (r = 0.26, P = 0.001). In univariate logistic regression analysis we found that level of GDF-15 ≥ 618 pg/mL, hs-CRP ≥7.12 mg/L, HbA1c ≥6.4%, fasting glucose ≥6.7 mmol/L, and BMI ≥27.3 kg/m2 predicted deficiency of both angiopoetic phenotypes of EPCs. In multivariate logistic regression model GDF-15 ≥618 pg/mL demonstrated the best odds ratio values for declining of EPCs in diabetics in comparison with other predictors including BMI, HbA1c and hs-CRP.
 Conclusion: GDF-15 was remarkably evaluated in type 2 DM population to healthy volunteers, and it was an independent factor that contributes to mobilization and probably proliferation of endothelial precursors with high angiopoetic activity.

Endothelial cells in the innate response to allergens and initiation of atopic asthma.

Protease-activated receptor 2 (PAR-2), an airway epithelial pattern recognition receptor (PRR), participates in the genesis of house dust mite-induced (HDM-induced) asthma. Here, we hypothesized that lung endothelial cells and proangiogenic hematopoietic progenitor cells (PACs) that express high levels of PAR-2 contribute to the initiation of atopic asthma. HDM extract (HDME) protease allergens were found deep in the airway mucosa and breaching the endothelial barrier. Lung endothelial cells and PACs released the Th2-promoting cytokines IL-1α and GM-CSF in response to HDME, and the endothelium had PAC-derived VEGF-C-dependent blood vessel sprouting. Blockade of the angiogenic response by inhibition of VEGF-C signaling lessened the development of inflammation and airway remodeling in the HDM model. Reconstitution of the bone marrow in WT mice with PAR-2-deficient bone marrow also reduced airway inflammation and remodeling. Adoptive transfer of PACs that had been exposed to HDME induced angiogenesis and Th2 inflammation with remodeling similar to that induced by allergen challenge. Our findings identify that lung endothelium and PACs in the airway sense allergen and elicit an angiogenic response that is central to the innate nonimmune origins of Th2 inflammation.

MiR-210 Enhances the Therapeutic Potential of Bone-Marrow-Derived Circulating Proangiogenic Cells in the Setting of Limb Ischemia.

Therapies based on circulating proangiogenic cells (PACs) have shown promise in ischemic disease models but require further optimization to reach the bedside. Ischemia-associated hypoxia robustly increases microRNA-210 (miR-210) expression in several cell types, including endothelial cells (ECs). In ECs, miR-210 represses EphrinA3 (EFNA3), inducing proangiogenic responses. This study provides new mechanistic evidences for a role of miR-210 in PACs. PACs were obtained from either adult peripheral blood or cord blood. miR-210 expression was modulated with either an inhibitory complementary oligonucleotide (anti-miR-210) or a miRNA mimic (pre-miR-210). Scramble and absence of transfection served as controls. As expected, hypoxia increased miR-210 in PACs. Invivo, migration toward and adhesion to the ischemic endothelium facilitate the proangiogenic actions of transplanted PACs. Invitro, PAC migration toward SDF-1α/CXCL12 was impaired by anti-miR-210 and enhanced by pre-miR-210. Moreover, pre-miR-210 increased PAC adhesion to ECs and supported angiogenic responses in co-cultured ECs. These responses were not associated with changes in extracellular miR-210 and were abrogated by lentivirus-mediated EFNA3 overexpression. Finally, ex-vivo pre-miR-210 transfection predisposed PACs to induce post-ischemic therapeutic neovascularization and blood flow recovery in an immunodeficient mouse limb ischemia model. In conclusion, miR-210 modulates PAC functions and improves their therapeutic potential in limb ischemia.

Autophagy activation in circulating proangiogenic cells aggravates AKI in type I diabetes mellitus.

Acute kidney injury (AKI) occurs frequently in hospitals worldwide, but the therapeutic options are limited. Diabetes mellitus (DM) affects more and more people around the globe. The disease worsens the prognosis of AKI even further. In recent years, cell-based therapies have increasingly been applied in experimental AKI. The aim of the study was to utilize two established autophagy inducers for pharmacological preconditioning of so-called proangiogenic cells (PACs) in PAC treatment of diabetic AKI. Insulin-dependent DM was induced in male C57/Bl6N mice by intraperitoneal injections of streptozotocine. Six weeks later, animals underwent bilateral renal ischemia for 45 min, followed by intravenous injections of either native or zVAD (benzyloxycarbonyl-Val-Ala-Asp-fluoro-methylketone)- or Z-Leu-Leu-Leu-al (MG132)-pretreated syngeneic murine PACs. Mice were analyzed 48 h (short term) and 6 wk (long term) later, respectively. DM worsened postischemic AKI, and PAC preconditioning with zVAD and MG132 resulted in a further decline of excretory kidney function. Injection of native PACs reduced fibrosis in nondiabetic mice, but cell preconditioning promoted interstitial matrix accumulation significantly. Both substances aggravated endothelial-to-mesenchymal transition (EndoMT) under diabetic conditions; these effects occurred either exclusively in the short (zVAD) or in the short and long term (MG132). Preconditioned cells stimulated the autophagocytic flux in intrarenal endothelial cells, and all experimental groups displayed increased endothelial abundances of senescence-associated β-galactosidase, a marker of premature cell senescence. Pharmacological autophagy activation may not serve as an effective strategy for improving PAC competence in diabetic AKI in general. On the contrary, several outcome parameters (excretory function, fibrosis, EndoMT) may even be worsened.

Does metronomic chemotherapy induce tumor angiogenic dormancy? A review of available preclinical and clinical data

Tumor dormancy is the ability of cancer cells to survive in a non-proliferating state. This condition can depend on three main mechanisms: cell cycle arrest (quiescence or cell dormancy), immunosurveillance (immunologic dormancy), or lack of functional blood vessels (angiogenic dormancy). In particular, under angiogenic dormancy, cancer cell proliferation is counterbalanced by apoptosis owing to poor vascularization, impeding tumor mass expansion beyond a microscopic size, with an asymptomatic and non-metastatic state. Tumor vasculogenic or non-angiogenic switch is essential to promote escape from tumor dormancy, leading to tumor mass proliferation and metastasis. In avascular lesions angiogenesis process results blocked from the equilibrium between pro- and anti-angiogenic factors, such as vascular endothelial growth factor (VEGF) and thrombospondin-1 (TSP-1), respectively. The angiogenic switch mainly depends on the disruption of this balance, in favor of pro-angiogenic factors, and on the recruitment of circulating endothelial progenitors (CEPs) that promote the formation of new blood vessels. Metronomic chemotherapy, the regular intake of doses able to sustain low but active concentrations of chemotherapeutic drugs during protracted time periods, is an encouraging therapeutic approach that has shown to upregulate anti-angiogenic factors such as TSP-1 and decline pro-angiogenic factors such as VEGF, suppressing the proangiogenic cells such as CEPs. In this perspective, metronomic chemotherapy may be one of the available therapeutic approaches capable to modulate favorably the angiogenic tumor dormancy, but further research is essential to better define this particular characteristic.

Effect of sildenafil citrate on circulating levels of sFlt-1 in preeclampsia.

To examine the effect of sildenafil on level of antiangiogenic proteins of preeclampsia. Firstly to examine the effect of sildenafil on serum biomarkers in a patient with preterm preeclampsia. Secondly, to examine the effect of sildenafil on sFlt-1 and soluble endoglin secretion from primary trophoblasts and placental explants. The clinical team administered 50 mg tds sildenafil to a 26-year-old primigravid woman with severe preeclampsia at the threshold of viability (24 3/7 weeks gestation) and we collected bloods to examine the effect of slidenafil on antiangiogenic factors sFlt-1 and soluble endoglin (sENG), pro-angiogenic factor PlGF and vascular cell adhesion molecule 1 (VCAM-1) and endothelin-1 (ET1). We administered sildenafil to human primary trophoblasts and placental explants and explored its effect on sFlt-1 and sENG secretion. We examined serum anti-angiogenic factors sFlt-1 and sENG, pro-angiogenic factor PlGF, the potent vasoconstrictor ET1 and VCAM-1 by ELISA. We explored the effect of sildenafil on sFlt-1 secretion from primary trophoblasts and sFlt-1 and sENG secretion from placental explants. We found a reduction in serum sFlt-1, stabilisation in sENG and PlGF in a patient with peri-viable preterm preeclampsia administered oral sildenafil 50 mg three times daily (tds). Furthermore there was an initial stabilisation in serum VCAM-1 and a decline in ET1 with sildenafil administration. This was concordant with stabilisation of clinical and biochemical features of preeclampsia. Interestingly, treating placental cells and tissues in vitro with sildenafil did not appear to change sFlt-1 or sENG secretion. Sildenafil administration was associated with a reduction in serum sFlt-1 and sENG secretion and increase in PlGF secretion in a patient with preterm preeclampsia, potentially via increasing placental perfusion rather than acting directly on the placenta.

Identification of the integrin-binding site on coagulation factor VIIa required for proangiogenic PAR2 signaling

AbstractThe tissue factor (TF) pathway serves both hemostasis and cell signaling, but how cells control these divergent functions of TF remains incompletely understood. TF is the receptor and scaffold of coagulation proteases cleaving protease-activated receptor 2 (PAR2) that plays pivotal roles in angiogenesis and tumor development. Here we demonstrate that coagulation factor VIIa (FVIIa) elicits TF cytoplasmic domain-dependent proangiogenic cell signaling independent of the alternative PAR2 activator matriptase. We identify a Lys-Gly-Glu (KGE) integrin-binding motif in the FVIIa protease domain that is required for association of the TF-FVIIa complex with the active conformer of integrin β1. A point mutation in this motif markedly reduces TF-FVIIa association with integrins, attenuates integrin translocation into early endosomes, and reduces delayed mitogen-activated protein kinase phosphorylation required for the induction of proangiogenic cytokines. Pharmacologic or genetic blockade of the small GTPase ADP-ribosylation factor 6 (arf6) that regulates integrin trafficking increases availability of TF-FVIIa with procoagulant activity on the cell surface, while inhibiting TF-FVIIa signaling that leads to proangiogenic cytokine expression and tumor cell migration. These experiments delineate the structural basis for the crosstalk of the TF-FVIIa complex with integrin trafficking and suggest a crucial role for endosomal PAR2 signaling in pathways of tissue repair and tumor biology.

Rationale and design of the Clinical and Histologic Analysis of Mesenchymal Stromal Cells in AmPutations (CHAMP) trial investigating the therapeutic mechanism of mesenchymal stromal cells in the treatment of critical limb ischemia

ObjectiveCurrently, there are no accepted nonsurgical therapies that improve the delivery of blood-derived nutrients to patients with critical limb ischemia. Here, we describe the ongoing phase 1/2 Clinical and Histologic Analysis of Mesenchymal Stromal Cells in AmPutations (CHAMP) trial, which will provide crucial evidence of the safety profile of mesenchymal stromal cells (MSCs) and explore their therapeutic mechanisms in the setting of critical limb ischemia requiring below-knee amputation (BKA). MethodsIn the CHAMP and the parallel marrowCHAMP trials (hereafter grouped together as CHAMP), a total of 32 extremities with rest pain or tissue loss requiring BKA will be enrolled to receive intramuscular injections of allogeneic MSCs (CHAMP; n = 16) or autogenous concentrated bone marrow aspirate (marrowCHAMP; n = 16) along the distribution of the BKA myocutaneous flap and proximal tibialis anterior. After treatment, subjects are randomized to BKA at four time points after injection (days 3, 7, 14, and 21). At the time of amputation, skeletal muscle is collected at 2-cm increments from the tibialis injection site and used to determine proangiogenic cytokine description, MSC retention, quantification of proangiogenic hematopoietic progenitor cells, and histologic description. Clinical limb perfusion before and after treatment will be quantified using transcutaneous oximetry, toe-brachial index, ankle-brachial index, and indocyanine angiography. Additional clinical end points include all-cause mortality, need for amputation revision, and gangrene incidence during the 6-month post-treatment follow-up. ResultsEnrollment is under way, with 10 patients treated per protocol thus far. We anticipate full conclusion of follow-up within the next 24 months. ConclusionsCHAMP will be pivotal in characterizing the safety, efficacy, and, most important, therapeutic mechanism of allogeneic MSCs and autogenous concentrated bone marrow aspirate in ischemic skeletal muscle.

Murine Bone Marrow Mesenchymal Stromal Cells Respond Efficiently to Oxidative Stress Despite the Low Level of Heme Oxygenases 1 and 2.

Mesenchymal stromal cells (MSCs) are heterogeneous cells from adult tissues that are able to differentiate in vitro into adipocytes, osteoblasts, or chondrocytes. Such cells are widely studied in regenerative medicine. However, the success of cellular therapy depends on the cell survival. Heme oxygenase-1 (HO-1, encoded by the Hmox1 gene), an enzyme converting heme to biliverdin, carbon monoxide, and Fe2+, is cytoprotective and can affect stem cell performance. Therefore, our study aimed at assessing whether Hmox1 is critical for survival and functions of murine bone marrow MSCs. Both MSC Hmox1+/+ and Hmox1-/- showed similar phenotype, differentiation capacities, and production of cytokines or growth factors. Hmox1+/+ and Hmox1-/- cells showed similar survival in response to 50 μmol/L hemin even in increased glucose concentration, conditions that were unfavorable for Hmox1-/- bone marrow-derived proangiogenic cells (BDMC). Hmox1+/+ MSCs but not fibroblasts retained low ROS levels even after prolonged incubation with 50 μmol/L hemin, although both cell types have a comparable Hmox1 expression and similarly increase its levels in response to hemin. MSCs Hmox1-/- treated with hemin efficiently induced expression of a vast panel of antioxidant genes, especially enzymes of the glutathione pathway. Innovation and Conclusion: Hmox1 overexpression is a popular strategy to enhance viability and performance of MSCs after the transplantation. However, murine MSCs Hmox1-/- do not differ from wild-type MSCs in phenotype and functions. MSC Hmox1-/- show better resistance to hemin than fibroblasts and BDMCs and rapidly react to the stress by upregulation of quintessential genes in antioxidant response. Antioxid. Redox Signal. 00, 000-000.

The role of hypoxia in shaping the recruitment of proangiogenic and immunosuppressive cells in the tumor microenvironment.

Hypoxia characterizes growing tumors and contributes significantly to their aggressiveness. Hypoxia-inducible factors (HIFs 1 and 2) are stabilized and act differentially as transcription factors on tumor growth and are responsible for important cancer hallmarks such as pathologic angiogenesis, cellular proliferation, apoptosis, differentiation and genetic instability as well as affecting tumor metabolism, tumor immune responses, invasion and metastasis. Taking into account the tumor tissue as a whole and considering the interplay of the various partners which react with hypoxia in the tumor site lead to reconsideration of the treatment strategies. Key limitations of treatment success result from the adaptation to the hypoxic milieu sustained by tumor anarchic angiogenesis. This raises immune tolerance by influencing the recruitment of immunosuppressive cells as bone marrow derived suppressor cells (MDSC) or by impairing the infiltration and killing of tumor cells by cytotoxic cells at the level of the endothelial cell wall of the hypoxic tumor vessels, as summarized in the schematic abstract.

Comparative Anti-Platelet Profiling Reveals a Potent Anti-Aggregatory Effect of CD34+ Progenitor Cell-Derived Late-Outgrowth Endothelial Cells in vitro

Background/Aims: Platelets affect endothelial progenitor cell (EPC) functionality, inducing their differentiation into mature endothelial cells. However, it remains to be established whether EPCs can influence platelet functionality. Methods: Mononuclear proangiogenic cells (MPCs) and early outgrowth cells (EOCs) were prepared from peripheral blood mononuclear cells, whereas late-outgrowth endothelial cells (OECs) were prepared from cord blood CD34+ cells. The effect of the above cells and their supernatants on washed platelet aggregation was studied. The effect of OECs and their supernatant on the adenosine diphosphate (ADP)-induced magnitude of platelet integrin receptor α_IIbβ₃ activation and on P-selectin membrane expression was investigated. The levels of nitric oxide (NO) and prostacyclin (PGI₂) that were secreted from EOCs, OECs, and human umbilical vein endothelial cells (HUVECs) were also assessed. Results: Among all progenitors, OECs and their supernatant exhibited the most potent inhibitory activity towards platelet aggregation. Furthermore, OECs and their supernatant, but not CD34+ cells, reduced α_IIbβ₃ activation and P-selectin membrane expression. Finally, OECs secreted higher NO and PGI₂ levels than EOCs did. Conclusion: The anti-platelet effect of EPCs depends highly on the degree of their endothelial phenotype, with OECs expressing the highest potency. Therefore, the induction of OEC generation and the enhancement of their functionality in vivo could be a new approach for the treatment of patients at a high thrombotic risk.

A phase II trial of lenalidomide plus rituximab in previously untreated follicular non-Hodgkin’s lymphoma (NHL): CALGB 50803 (Alliance)

BackgroundThis multicenter, phase II trial tested the tolerability and efficacy of lenalidomide plus rituximab in patients with previously untreated follicular lymphoma (FL). Patients and methodsPatients with grade 1–3a FL, stage 3–4 or bulky stage 2, FL international prognostic index (FLIPI) 0–2, and no prior therapy were eligible to receive rituximab 375mg/m2 weekly during cycle 1 and day 1 of cycles 4, 6, 8, and 10, plus lenalidomide 20–25mg on days 1–21 for twelve 28-day cycles. The primary objectives were to evaluate response rates [complete (CR) and overall] and time to progression. Secondary objectives included toxicity, response according to polymorphisms in FcgR2A and FcgR3A, and changes in circulating pro-angiogenic cells. ResultsFrom October 2010 to September 2011, 66 patients were enrolled. Median age was 53years, 34 were female, 15 had bulky disease, 21 were FLIPI 0-1, 43 FLIPI 2, and 2 FLIPI 3. One patient withdrew before receiving treatment. Fifty-one patients completed 12 cycles of lenalidomide. Reasons for discontinuation included withdrawal (n=6), adverse events (n=6), progression (n=2). Grade 3–4 hematologic toxicity included neutropenia (21%), lymphopenia (9%), and thrombocytopenia (2%), infection (11%), and rash (8%). Grade 1–2 toxicity included fatigue (78%), diarrhea (37%), rash (32%), and febrile neutropenia in one patient. The overall response rate was 95%; the CR rate was 72% (95% confidence interval, 60% to 83%). With a median follow-up of 5years, the 2- and 5-year progression-free survival were 86% and 70%, respectively, and the 5-year overall survival was 100%. There was no association between CR rate or PFS and FLIPI, histological grade, bulky disease, FcgR2A/FcgR3A polymorphism, or change in circulating endothelial cell/hematopoietic progenitor cell. ConclusionLenalidomide plus rituximab was associated with low rates of grade 3–4 toxicity, yielded a CR rate and PFS similar to chemotherapy-based treatment and may represent a reasonable alternative to immunochemotherapy in previously untreated FL. ClinicalTrials.gov IdentifierNCT01145495.

Guiding morphogenesis in cell-instructive microgels for therapeutic angiogenesis

Efficient cell delivery strategies are urgently needed to improve the outcome of cell-based pro-angiogenic therapies. This study describes the design of an injectable cell delivery platform, based on biomaterial-guided morphogenesis principles. Soft high-mannuronic acid alginate microgels, oxidized and functionalized with integrin-binding peptides, provided adequate biochemical/biomechanical cues for the co-assembly of mesenchymal stem cells and outgrowth endothelial cells (OEC) into pre-vascularized microtissues. In vitro priming conditions regulated OEC tubulogenesis, which only occurred under normoxia (+O2) in the presence of angiogenic factors (+GF) and, importantly, did not revert in an ischemic-like environment. Primed (+O2+GF) microgel-entrapped cells secreted a large variety of angiogenesis-related proteins and produced endogenous extracellular-matrix, rich in fibronectin and collagen type I, fostering cell-cell/cell-matrix interactions and establishing a stable angiogenic niche. Extending the pre-culture time resulted in higher cell outward migration and in vivo angiogenic potential. Microgels partially disintegrated upon implantation in chick embryos, promoting interaction between pre-vascularized microtissues and the host. Preserved human vascular structures were still detected in vivo, and human cells showed the ability to migrate and integrate with the chick vasculature. Our results suggest that an integrated approach combining pro-angiogenic cells, cell-instructive microgels and adequate in vitro priming may provide the basis for successful therapeutic angiogenesis.

Glycoprotein Non-Metastatic Melanoma Protein B (GPNMB) and Cancer: A Novel Potential Therapeutic Target

Glycoprotein non-metastatic melanoma protein B (GPNMB) is a transmembrane protein enriched on the cell surface of cancer cells, including melanoma, glioblastoma, and triple-negative breast cancer. There is growing evidence identifying GPNMB as a tumor-promoter; however, despite its biological and clinical significance, the molecular mechanisms engaged by GPNMB to promote tumorigenesis are not well understood. GPNMB promotes aggressive behaviors such as tumor cell proliferation, migration, and invasion. The extracellular domain of GPNMB shed from the cell surface interacts with integrins to facilitate in the recruitment of immune-suppressive and pro-angiogenic cells to the tumor microenvironment, thereby enhancing tumor migration and invasion. GPNMB also modulates receptor tyrosine kinases and integrin signaling in a cell autonomous fashion, leading to downstream kinase signaling that in turn triggers the expression and secretion of tumorigenic factors such as matrix metalloproteinases (MMPs) and cytokines. Therefore, GPNMB exerts its pro-tumorigenic role both intracellularly and in a paracrine fashion through shedding its extracellular domain. This review highlights the importance of GPNMB in cancer progression and discusses molecular mediators of GPNMB-induced tumor growth and invasion.

Neonatal exposure to high oxygen levels leads to impaired ischemia-induced neovascularization in adulthood

Adverse perinatal conditions can lead to developmental programming of cardiovascular diseases. Prematurely born infants are often exposed to high oxygen levels, which in animal models has been associated with endothelial dysfunction, hypertension, and cardiac remodeling during adulthood. Here we found that adult mice that have been transiently exposed to O2 after birth show defective neovasculariation after hindlimb ischemia, as demonstrated by impaired blood flow recovery, reduced vascular density in ischemic muscles and increased tissue damages. Ischemic muscles isolated from mice exposed to O2 after birth exhibit increased oxidative stress levels and reduced expression of superoxide dismutase 1 (SOD1) and vascular endothelial growth factor (VEGF). Pro-angiogenic cells (PACs) have been shown to have an important role for postnatal neovascularisation. We found that neonatal exposure to O2 is associated with reduced number of PACs in adults. Moreover, the angiogenic activities of both PACs and mature mouse aortic endothelial cells (MAECs) are significantly impaired in mice exposed to hyperoxia after birth. Our results indicate that neonatal exposure to high oxygen levels leads to impaired ischemia-induced neovascularization during adulthood. The mechanism involves deleterious effects on oxidative stress levels and angiogenic signals in ischemic muscles, together with dysfunctional activities of PACs and mature endothelial cells.

CXCL6 is an important paracrine factor in the pro-angiogenic human cardiac progenitor-like cell secretome

Studies in recent years have established that the principal effects in cardiac cell therapy are associated with paracrine/autocrine factors. We combined several complementary techniques to define human cardiac progenitor cell (CPC) secretome constituted by 914 proteins/genes; 51% of these are associated with the exosomal compartment. To define the set of proteins specifically or highly differentially secreted by CPC, we compared human mesenchymal stem cells and dermal fibroblasts; the study defined a group of growth factors, cytokines and chemokines expressed at high to medium levels by CPC. Among them, IL-1, GROa (CXCL1), CXCL6 (GCP2) and IL-8 are examples whose expression was confirmed by most techniques used. ELISA showed that CXCL6 is significantly overexpressed in CPC conditioned medium (CM) (18- to 26-fold) and western blot confirmed expression of its receptors CXCR1 and CXCR2. Addition of anti-CXCL6 completely abolished migration in CPC-CM compared with anti-CXCR2, which promoted partial inhibition, and anti-CXCR1, which was inefficient. Anti-CXCL6 also significantly inhibited CPC CM angiogenic activity. In vivo evaluation also supported a relevant role for angiogenesis. Altogether, these results suggest a notable angiogenic potential in CPC-CM and identify CXCL6 as an important paracrine factor for CPC that signals mainly through CXCR2.

Synthetic microparticles conjugated with VEGF165 improve the survival of endothelial progenitor cells via microRNA-17 inhibition

Several cell-based therapies are under pre-clinical and clinical evaluation for the treatment of ischemic diseases. Poor survival and vascular engraftment rates of transplanted cells force them to work mainly via time-limited paracrine actions. Although several approaches, including the use of soluble vascular endothelial growth factor (sVEGF)—VEGF165, have been developed in the last 10 years to enhance cell survival, they showed limited efficacy. Here, we report a pro-survival approach based on VEGF-immobilized microparticles (VEGF-MPs). VEGF-MPs prolong VEGFR-2 and Akt phosphorylation in cord blood-derived late outgrowth endothelial progenitor cells (OEPCs). In vivo, OEPC aggregates containing VEGF-MPs show higher survival than those treated with sVEGF. Additionally, VEGF-MPs decrease miR-17 expression in OEPCs, thus increasing the expression of its target genes CDKN1A and ZNF652. The therapeutic effect of OEPCs is improved in vivo by inhibiting miR-17. Overall, our data show an experimental approach to improve therapeutic efficacy of proangiogenic cells for the treatment of ischemic diseases.

Differences in Stem Cell Processing Lead to Distinct Secretomes Secretion—Implications for Differential Results of Previous Clinical Trials of Stem Cell Therapy for Myocardial Infarction

Stem cell therapy for acute myocardial infarction (AMI) seemed to be a promising therapy, however, large clinical trials brought differential outcome. It has been shown that paracrine effects of secretomes of stem cells rather than cell therapy might play a fundamental role. The present study seeks to compare cell processing protocols of clinical trials and investigate effects of differential cell culture conditions on chemokine secretion and functional effects. Different secretomes are compared regarding IL-8, VEGF, MCP-1, and TNF-alpha secretion. Secretome mediated effects are evaluated on endothelial cell (HUVEC) tube formation and migration. Cardioprotective signaling kinases in human cardiomyocytes are determined by Western immunoblotting. Cells processed according to the REPAIR-AMI protocol secrete significantly higher amounts of IL-8 (487.3 ± 1231.1 vs 9.1 ± 8.2 pg mL-1 ; p < 0.05). REAPIR-AMI supernatants lead to significantly pronounced tube formation and migration on HUVEC and enhance the phosphorylation of Akt, ERK, and CREB. Cell processing conditions have a major impact on the composition of the secretome. The REPAIR-AMI secretome significantly enhances proangiogenic chemokine secretion, angiogenesis, cell migration, and cardioprotective signaling pathways. These results might explain differential outcomes between clinical trials. Optimizing cell processing protocols with special regards to paracrine factors, might open a new therapeutic concept for improving patient outcome.

Endothelial colony-forming cells and pro-angiogenic cells: clarifying definitions and their potential role in mitigating acute kidney injury.

Acute kidney injury (AKI) represents a significant clinical concern that is associated with high mortality rates and also represents a significant risk factor for the development of chronic kidney disease (CKD). This article will consider alterations in renal endothelial function in the setting of AKI that may underlie impairment in renal perfusion and how inefficient vascular repair may manifest post-AKI and contribute to the potential transition to CKD. We provide updated terminology for cells previously classified as 'endothelial progenitor' that may mediate vascular repair such as pro-angiogenic cells and endothelial colony-forming cells. We consider how endothelial repair may be mediated by these different cell types following vascular injury, particularly in models of AKI. We further summarize the potential ability of these different cells to mitigate the severity of AKI, improve perfusion and maintain vascular structure in pre-clinical studies.