VEGF Release Research Articles

Effect of Glucose on Retinal Endothelial Cell Viability and VEGF Secretion

Previous studies have shown that in diabetic patients, there is an increase of retinal capillaries associated with the development of diabetic retinopathy in the eye. The objective of current study is to investigate the effect of glucose on retinal endothelial cell viability and VEGF secretion. 20,000 cells per well were treated without glucose or with 5.5mM (euglycemic), 18.5mM and 30mM (hyperglycemic) glucose for 24 hours. Viable cells were counted using Trypan blue dye exclusion method. ELISA was used to measure VEGF secretion from cells into the cell medium. The number of viable cells incubated with 5.5mM glucose (physiological control) increased by 53.7% after 24 hours. In comparison, cells treated with 18.5mM glucose decreased by 2.8% while cells treated with 30mM glucose decreased by 20% after 24 hours of incubation. Cells without glucose treatment (0mM control) decreased by 33.3%. In contrast to the decrease of viable cell numbers after treatment with high glucose, there is an increase in VEGF secretion (pg/mL) to the cell medium with increase in glucose concentration from 5.5mM to 0, 18.5, and 30mM. The amount of VEGF secreted per cell also increased with increasing glucose concentrations. Our results show that viability of retinal endothelial cells and VEGF release are highly responsive to changes in glucose concentration. Such glucose-induced changes in retinal endothelial cells may negatively impact the integrity of the microvasculature in the diabetic retina leading to angiogenesis and microaneursyms.

Defective Autophagy in Diabetic Retinopathy.

Müller cells (MCs) are a major source of VEGF in diabetic retinopathy (DR). Vascular endothelial growth factor is the main therapeutic target for treating DR. This study aimed to investigate whether autophagy is involved in MC response under high glucose (HG). Rat retinal Müller cells (rMCs) were exposed to normal or high glucose in and out of presence of pharmacologic inhibitors and activators and small interfering RNA (siRNA) for p62/SQTSM1 for 24 hours. High glucose induces increase of early and late autophagic markers, accumulation of p62/SQTSM1 and endoplasmic reticulum (ER) stress response associated with apoptosis augmentation (P < 0.01). The inhibition of autophagy in HG leads to higher rMC apoptotic rate (P < 0.001). By silencing the p62/SQTSM1, ER stress is ameliorated (p<0.0001), preventing apoptosis. Retinal MCs in HG treated with rapamycin (mTOR inhibitor) show autophagy machinery activation and reestablishment of cargo degradation, protecting cells from apoptosis (P < 0.0001). Rapamycin improves lysosomal proteolytic activity by improving cathepsin L activity restoring autophagic cargo degradation, and preventing increased VEGF release (P < 0.0001). In experimental model of diabetes, Beclin-1 and p62/SQTSM-1 were found to be marked increased in retinas from diabetic Wystar Kyoto rats compared with control group (P < 0.003) with reduction of cathepsin L activity. High glucose upregulates autophagy but accumulates p62/SQTSM1 cargo due to lysosomal dysfunction, leading to massive VEGF release and cell death of rMCs. Lysosomal impairment and autophagic dysfunction are early events present in the pathogenesis of diabetic retinopathy (DR). This might be valuable for developing a novel therapeutic strategy to treat DR.

In vitro assays suggest Shenqi Fuzheng Injection has the potential to alter melanoma immune microenvironment

Ethnopharmacological relevanceA modern agent Shenqi Fuzheng Injection (SFI), prepared from Codonopsis Radix and Astragali Radix, has been commonly used as a supplementary therapy for cancers including melanoma. This agent was derived from a formula documented in the “National Collection of Chinese Medicine Prescriptions”. The formula has long been used as a remedy for Qi deficiency that is closely associated with cancer-related fatigue and poor quality of life. However, the antimelanoma mechanisms of SFI remain unclear. Here we tested if SFI exerted antimelanoma effects by reprograming the tumour immune microenvironment using in vitro assays. Materials and methodsThe cytotoxic activities of Jurkat T cells when co-cultured with A375 cells were determined in the presence or absence of SFI. The migratory activities of Jurkat T cells were examined in the transwell assay system. The mRNA expression and production of cytokines (IL-10, TGF β and VEGF) in A375 cells in the presence or absence of SFI were determined by real-time PCR and ELISA, respectively. ResultsWhen A375 cells were co-cultured with Jurkat T cells in the presence of SFI (220µg/mL), a potent cytotoxicity effect against A375 cells was observed. Supernatants from A375 cells that were treated with SFI (110 and 220µg/mL) significantly increased the migratory capacity of Jurkat T cells in transwell assays. SFI also markedly reduced the mRNA expression levels and the release of immunosuppressive cytokines IL-10, TGF-β and VEGF in A375 cells in a concentration-dependent manner. ConclusionsSFI enhanced the cytotoxic and migratory activities of Jurkat T cells towards A375 melanoma cells. The effects were associated with SFI's suppression on immunosuppressive cytokines for their release from and gene expressions in A375 melanoma cells. These in vitro findings suggested that SFI might reprogramme the immunosuppressive melanoma microenvironment in vivo to enhance the cytotoxicity of tumour-infiltrating immune cells. This study provides a pharmacological basis for the adjunctive use of SFI in melanoma treatment.

High Seeding Density Induces Local Hypoxia and Triggers a Proinflammatory Response in Isolated Human Islets.

Hypoxia is the main threat to morphological and functional integrity of isolated pancreatic islets. Lack of oxygen seems to be of particular importance for functionality of encapsulated islets. The present study was initiated as an experimental model for the environment experienced by human islets in a confined space present during culture, shipment, and in an implanted macrodevice. Quadruplicate aliquots of isolated human islets (n = 12) were cultured for 24 h at 37°C under normoxic conditions using 24-well plates equipped with 8-µm pore size filter inserts and filled with islet aliquots adjusted to obtain a seeding density of 75, 150, 300, or 600 IEQ/cm(2). After culture viability, glucose-stimulated insulin release, DNA content as well as Bax and Bcl-2 gene expression were measured. Culture supernatants were collected to determine production of VEGF and MCP-1. Viability correlated inversely with IEQ seeding density (r = -0.71, p < 0.001), while the correlation of VEGF and MCP-1 secretion with seeding density was positive (r = 0.78, p < 0.001; r = 0.54, p < 0.001). Decreased viability corresponded with a significant increase in the Bax/Bcl-2 mRNA ratio at 300 and 600 IEQ/cm(2) and with a sigificantly reduced glucose-stimulated insulin secretion and insulin content compared to 75 or 150 IEQ/cm(2) (p < 0.01). The present study demonstrates that the seeding density is inversely correlated with islet viability and in vitro function. This is associated with a significant increase in VEGF and MCP-1 release suggesting a hypoxic and proinflammatory islet microenvironment.

The Effects Of Protease-Activated Receptors 1 And 4 In Human Platelet Activation And Inflammation

Category: Basic Sciences/Biologics Introduction/Purpose: Tendon injuries occur frequently and cost billions of health care dollars annually. Recently, there has been an increase in the use of platelet-rich plasma (PRP) to treat tendon injuries. However, the efficacy of PRP treatment is controversial due to inconsistent results from human clinical trials. It is thought that variations in PRP preparation contribute to these inconsistencies. Specifically, platelets in PRP contain pro-angiogenic (e.g. VEGF) or anti-angiogenic (e.g. endostatin) factors, which may differentially affect the healing of tendon injuries. It is known that these factors are selectively released after platelet activation by specific receptors. Therefore, in this study we investigated the effect of protease-activated receptors 1 and 4 (PAR1 and PAR4) in platelet activation and inflammation. Methods: Platelet preparation – Human blood was obtained from 12 healthy donors and 9 ml of blood was mixed with 1 ml of 3.8% sodium citrate and centrifuged at 500g for 10 min. Then, the supernatant (PRP) without the buffy coat was centrifuged at 1000g for 10 min and the resulting pellet was washed in Tyrodes-HEPES buffer and centrifuged for 10 min at 1000g. Finally, platelets in the pellet was suspended in Tyrodes-HEPES buffer and used in experiments. Platelet activation – About 100 μl of platelet from above was activated with 5 μl 1 mM PAR1-activating peptide (PAR1-AP) or PAR4-activating peptide (PAR4-AP) at 25°C for 10 min. Then, the mixture was centrifuged at 1000g for 10 min, and the levels of VEGF, endostatin, IL-1RA and HMGB-1in the supernatant was determined by ELISA. Platelets without activators were used as controls. Results: PAR1 induced angiogenic effects in human platelets. PAR1 activated platelets released 3 times more VEGF than when activated with PAR4 (Fig. 1A). However, PAR4 activated platelets released 7 times more endostatin than the PAR1 activated platelets (Fig. 1B). Further, PAR1 induced anti-inflammatory effects in human platelets; it did not change IL-1R-A (Fig. 2A) but decreased HMGB-1 levels (Fig. 2B). In contrast, PAR4 stimulated inflammatory effects in human platelets by lowering IL-1-RA and increasing HMGB-1 levels. Conclusion: Our findings indicate that PAR1 induces angiogenetic and anti-inflammatory effects in human platelets, while PAR4 has anti-angiogenetic and inflammatory effects. Of significance is HMGB-1, which is constitutively expressed in the nuclei of most mammalian cells. Under cellular stress, HMGB1 is released into the extracellular matrix and activates the immune response thus acting as a danger-signal. Both PAR1 and PAR4 selectively regulated the release of VEGF and endostatin, and IL-1RA and HMGB-1 from human platelets. Therefore, the role of PAR1 and PAR4 on human platelet activation and inflammation should be considered prior to the use of PRP to treat tendon injuries.

Design and Fabrication of Complex Scaffolds for Bone Defect Healing: Combined 3D Plotting of a Calcium Phosphate Cement and a Growth Factor-Loaded Hydrogel

Additive manufacturing enables the fabrication of scaffolds with defined architecture. Versatile printing technologies such as extrusion-based 3D plotting allow in addition the incorporation of biological components increasing the capability to restore functional tissues. We have recently described the fabrication of calcium phosphate cement (CPC) scaffolds by 3D plotting of an oil-based CPC paste under mild conditions. In the present study, we have developed a strategy for growth factor loading based on multichannel plotting: a biphasic scaffold design was realised combining CPC with VEGF-laden, highly concentrated hydrogel strands. As hydrogel component, alginate and an alginate-gellan gum blend were evaluated; the blend exhibited a more favourable VEGF release profile and was chosen for biphasic scaffold fabrication. After plotting, two-step post-processing was performed for both, hydrogel crosslinking and CPC setting, which was shown to be compatible with both materials. Finally, a scaffold was designed and fabricated which can be applied for testing in a rat critical size femur defect. Optimization of CPC plotting enabled the fabrication of highly resolved structures with strand diameters of only 200µm. Micro-computed tomography revealed a precise strand arrangement and an interconnected pore space within the biphasic scaffold even in swollen state of the hydrogel strands.

Targeting the PI3K/AKT/mTOR pathway overcomes the stimulating effect of dabrafenib on the invasive behavior of melanoma cells with acquired resistance to the BRAF inhibitor.

BRAF inhibitors (BRAFi) have proven clinical benefits in patients with BRAF-mutant melanoma. However, acquired resistance eventually arises. The effects of BRAFi on melanoma cell proliferation and survival have been extensively studied, and several mechanisms involved in acquired resistance to the growth suppressive activity of these drugs have been identified. Much less is known about the impact of BRAFi, and in particular of dabrafenib, on the invasive potential of melanoma cells. In the present study, the BRAF-mutant human melanoma cell line A375 and its dabrafenib-resistant subline A375R were analyzed for invasive capacity, expression of vascular endothelial growth factor receptor (VEGFR)-2, and secretion of VEGF-A and matrix metalloproteinase (MMP)-9, under basal conditions or in response to dabrafenib. The consequences of inhibiting the PI3K/AKT/mTOR pathway on A375R cell responses to dabrafenib were also evaluated. We found that A375R cells were more invasive and secreted higher levels of VEGF-A and MMP-9 as compared with A375 cells. Dabrafenib reduced invasiveness, VEGFR-2 expression and VEGF-A secretion in A375 cells, whereas it increased invasiveness, VEGF-A and MMP-9 release in A375R cells. In these latter cells, the stimulating effects of dabrafenib on the invasive capacity were markedly impaired by the anti-VEGF‑A antibody bevacizumab, or by AKT1 silencing. A375R cells were not cross-resistant to the PI3K/mTOR inhibitor GSK2126458A. Moreover, this inhibitor given in combination with dabrafenib efficiently counteracted the stimulating effects of the BRAFi on invasiveness and VEGF-A and MMP-9 secretion. Our data demonstrate that melanoma cells with acquired resistance to dabrafenib possess a more invasive phenotype which is further stimulated by exposure to the drug. Substantial evidence indicates that continuing BRAFi therapy beyond progression produces a clinical benefit. Our results suggest that after the development of resistance, a regimen combining BRAFi with bevacizumab or with inhibitors of the PI3K/AKT/mTOR pathway might be more effective than BRAFi monotherapy.

The Relationship Between Herbal Anticoagulants and Melasma

Context: Melasma is a common pigmentary disorder with the incidence of 1.5% - 33.3% worldwide. Targeting the vascular component in melasma lesions may decrease the melanocytic stimulation. Herbal anticoagulants can serve as effective candidates for melasma treatment. Evidence Acquisition: The evidence was gathered in this study by evaluating vascularization as an etiology of melasma and considering the role of herbal anticoagulants in natural vascular treatment. Databases such as PubMed and Scopus were screened and the following keywords were searched: melasma, vascularization, pigmentation, and herbal anticoagulant. These subjects were further investigated in traditional textbooks such as the canon of medicine by Avicenna and Alhavi by Razi. At the end, the results were discussed. Result: The use of anticoagulants can reduce the clot formation and lower the VEGF release. In this way, vascularization will be reduced, consequently leading to a decrease in melasma occurrence. The researchers of the present study went over the herbal components that were effective for treatment of melasma and found that most of them consisted of anticoagulants such as coumarin. Conclusion: The effect of herbal anticoagulants (administered orally) on melasma should be evaluated clinically and their combination with topical treatments is suggested.

VEGF as a Survival Factor in Ex Vivo Models of Early Diabetic Retinopathy.

Growing evidence indicates neuroprotection as a therapeutic target in diabetic retinopathy (DR). We tested the hypothesis that VEGF is released and acts as a survival factor in the retina in early DR. Ex vivo mouse retinal explants were exposed to stressors similar to those characterizing DR, that is, high glucose (HG), oxidative stress (OS), or advanced glycation end-products (AGE). Neuroprotection was provided using octreotide (OCT), a somatostatin analog, and pituitary adenylate cyclase activating peptide (PACAP), two well-documented neuroprotectants. Data were obtained with real-time RT-PCR, Western blot, ELISA, and immunohistochemistry. Apoptosis was induced in the retinal explants by HG, OS, or AGE treatments. At the same time, explants also showed increased VEGF expression and release. The data revealed that VEGF is released shortly after exposure of the explants to stressors and before the level of cell death reaches its maximum. Retinal cell apoptosis was inhibited by OCT and PACAP. At the same time, OCT and PACAP also reduced VEGF expression and release. Vascular endothelial growth factor turned out to be a protective factor for the stressed retinal explants, because inhibiting VEGF with a VEGF trap further increased cell death. These data show that protecting retinal neurons from diabetic stress also reduces VEGF expression and release, while inhibiting VEGF leads to exacerbation of apoptosis. These observations suggest that the retina in early DR releases VEGF as a prosurvival factor. Neuroprotective agents may decrease the need of VEGF production by the retina, therefore limiting the risk, in the long term, of pathologic angiogenesis.

Abstract 535: Trem Like Transcript-1 (TLT-1) Regulates Both Leukocytes and Endothelial Cells to Mediate Immunohemostasis

TLT-1 is a 35kd receptor stored in the α-granules of platelets and released upon platelet activation like p-selectin. A soluble form is also released. A case has been made that the protein or proteins that regulate inflammatory bleeding is stored in the platelet α-granules. We hypothesized that TLT-1 is one of these proteins and we investigated TLT-1’s role in inflammatory bleeding. Using two different models of inflammation and three different models of transmigration we show that TLT-1 mediates neutrophil transmigration across the vessel wall. In the absence of TLT-1 transmigration leads to bleeding that can be partially rescued by soluble TLT-1 (sTLT-1: see poster J. Morales). Based on these results we hypothesized that TLT-1 enhances the progression of atherosclerosis and cancer. To test this hypothesis we crossed the treml1 -/- mice with apoe -/- mice creating the DKO mouse and evaluated lesion progression over 20 weeks. Our results demonstrate that the DKO has significantly less lesions in the aortic sinus than their littermate controls (n=8/group; p &lt;0.05). The smaller lesions are associated with less platelet activation and fewer platelet-leukocyte conjugates. Parallel studies investigating TLT-1 in the α-granules revealed a significant co-localization with pro-angiogenic VEGF and higher sTLT-1 release with PAR1 vs PAR4 platelet activation; suggestive of a role for TLT-1 in angiogenesis. We subsequently asked if, “sTLT-1 has an effect on endothelial cells?” We show angiogenic effects of sTLT-1 on HUVECs that is blocked by the addition of anti-TLT-1, demonstrating it’s a sTLT-1 mediated process. Further studies using the Lewis lung carcinoma model demonstrate that the tumors in the null mouse have significantly fewer vessels than wildtype tumors and lower infiltration of macrophages (n=15). We subsequently show that sTLT-1 partially rescues the phenotype by increasing macrophage infiltration and increasing vessel growth (n=13) and that antibodies to TLT-1 recapitulate the treml1 -/- phenotype (n=10) suggesting anti-TLT-1 may be used as an intervention. We conclude that TLT-1 regulates both leukocytes and endothelial cells to mediate vascular integrity and is a plausible target for therapeutic interventions in cancer and atherosclerosis.

Impaired endothelial shear stress induces podosome assembly via VEGF up-regulation.

Podosomes are dynamic cytoskeletal membrane structures with local adhesive and proteolytic activity. They are critically involved in angiogenesis and vascular adaptive growth. Here, we studied in HUVECs and murine small vessels whether shear stress controls podosome assembly and local proteolytic activity. Podosomes were characterized by immunohistochemistry, and their proteolytic activity was assessed as degradation imprints in fluorescent gelatin that was used as growth substrate. Compared with controls (10 dyn/cm(2)), the number of podosomes formed per time was doubled when cells were exposed to low shear stress (0.3 dyn/cm(2)) or even increased 5-fold under static conditions. This was a result of an enhanced expression of VEGF after reduction of shear stress. Consequently, enhanced podosome formation could be prevented by a VEGF receptor antagonist as well by interruption of VEGF signaling via inhibition of PI3K, Src, or p38. Increase of podosome assembly went along with significantly augmented cell motility. In vivo experiments in mouse arteries confirmed increased endothelial podosome numbers when shear stress was abolished by vessel occlusion. We conclude that shear stress, by reducing VEGF release, inhibits podosome assembly. Hence, endothelial cell-mediated matrix proteolysis and migratory activity are inhibited, thereby stabilizing the structure of the vessel wall.-Fey, T., Schubert, K. M., Schneider, H., Fein, E., Kleinert, E., Pohl, U., Dendorfer, A. Impaired endothelial shear stress induces podosome assembly via VEGF up-regulation.

Effect of prostaglandin D2 on VEGF release by nasal polyp fibroblasts

BackgroundVascular endothelial growth factor (VEGF) is known to be associated with the pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP). VEGF is produced by a variety of cells including fibroblasts. It was recently reported that prostaglandin (PG) E2 induces VEGF release by nasal polyp fibroblasts. However, little is known regarding possible regulation of VEGF by other PGs. We have reported that molecules that regulate PGD2 metabolism play roles in the pathogenesis of CRS including in local eosinophilia and type 2 cytokine production. In the present study, we sought to determine whether PGD2 regulates VEGF release by nasal polyp fibroblasts. MethodsNasal polyp fibroblasts were established from nasal polyps. These fibroblasts were stimulated with serial dilutions of PGD2 or PGD2 receptor (DP/CRTH2)-selective agonists in the presence or absence of receptor-selective antagonists. The concentration of VEGF in the culture supernatants was determined using ELISA. Results5 μM of PGD2 significantly induced VEGF release by nasal polyp fibroblasts. VEGF release was also obtained by stimulation with a DP receptor-selective, but not with a CRTH2 receptor-selective agonist. In addition, PGD2-induced VEGF release was significantly inhibited by pre-treatment with DP receptor-selective antagonists. In contrast, pre-treatment with a CRTH2 receptor-selective antagonist significantly enhanced PGD2-induced VEGF release. ConclusionsPGD2 stimulates VEGF production via DP but not CRTH2 receptors in nasal polyp fibroblasts.

Proinsulin C‐peptide prevents VEGF release from ARPE‐19 cells: A novel signaling mechanism

Diabetic macular edema is associated with the breakdown of tight junctions between retinal pigment epithelial (RPE) cells, which form the blood‐retinal barrier and provide metabolic support to the photoreceptors. Loss of tight junctions within this single‐celled layer of the retina leads to enhanced permeability of the blood‐retinal barrier, intra‐ocular swelling, and macular edema. The mechanisms underlying RPE dysfunction in diabetic macular edema are not fully understood, but excessive VEGF secretion and signaling appears to play a role. Because proinsulin C‐peptide has been shown to prevent and reverse diabetic eye disease and protect against the deleterious effects of VEGF hyper‐secretion, we evaluated the effect of C‐peptide on VEGF release from the human RPE cell line, ARPE‐19. Exposure of ARPE‐19 cells to C‐peptide inhibited basal and high glucose‐stimulated VEGF release. Furthermore, C‐peptide suppressed insulin‐stimulated VEGF release from these cells as well. Because C‐peptide has been shown to regulate activity of the Na+/K+ ATPase in multiple cell types, we hypothesized that C‐peptide prevents the hyper‐secretion of VEGF induced by high glucose by enhancing Na+/K+ ATPase activity. However, treatment with the Na+/K+ ATPase inhibitor ouabain also decreased VEGF release from ARPE‐19 cells exposed to high glucose. We therefore propose that C‐peptide prevents excessive VEGF release from the retinal pigment epithelium by suppressing Na+/K+ ATPase activity, which could have important implications for the management of diabetic macular edema.

Hormone signaling pathways as treatment targets in renal cell cancer (Review).

Epidemiological, clinical, biochemical and genetic research has revealed that renal cell cancer (RCC) etiology is hormone-related. It was shown that hormone receptors are abnormally expressed in RCC cells. Abnormal endocrine stimulation also plays a significant role in RCC pathophysiology. Cellular proliferation, migration, angiogenesis, and drug resistance in RCC is modulated by para- and autocrine hormonal stimulation. In particular, RCC overexpression of gonadotropin-releasing hormone and its receptor was reported. On the contrary, corticotropin releasing hormone was reported to inhibit RCC cell proliferation and regulate angiogenesis. Overexpression of luteinizing hormone also promotes RCC tumor angiogenesis. Estrogen receptor α overexpression increases the transcriptional factor activity of hypoxia inducible factor HIF-1α, but estrogen receptor β has a cancer suppressive role. Glucocorticoid receptors and androgen receptor are markers of indolent RCC and assigned tumor suppressive activity. Proopiomelanocortin is upregulated in VHL-mutated renal cell carcinoma via Nur77 transcription factor signaling. In RCC, follicle-stimulating hormone receptor promotes angiogenesis and metastatic formation via VEGF release. Mineralocorticoid receptor overexpression promotes cell survival and increases RCC cell proliferation. Vitamin D receptor expression is downregulated or absent in RCC and differentiate subtypes of renal cell tumors. RAR-β promotes tumorigenesis but retinoic acid receptor γ expression correlates negatively with the TNM stage at diagnosis. Finally, progesterone receptor expression is negatively correlated with the cancer stage. Molecular data analysis revealed the possibility of renal cancer cell proliferation induction via hormone activated pathways. Inhibition of hormonal signaling may thus play a putative role in supportive therapies against this cancer type.

Cell-derived microvesicles mediate the delivery of miR-29a/c to suppress angiogenesis in gastric carcinoma

Microvesicles (MVs) secreted from cells have been found to mediate signal transduction between cells. In the tumor microenvironment, VEGF released from cancer cells plays a key role in promoting tumor angiogenesis. In this study, we characterized the inhibitory effect of MV-delivered miR-29a/c on angiogenesis and tumor growth in gastric cancer (GC). We found that the downregulation of miR-29a/c increases VEGF expression and release in GC cells, promoting the growth of vascular cells. By simulating the tumor microenvironment, the MV-delivered miR-29a/c significantly suppresses VEGF expression in GC cells, inhibiting vascular cell growth, metastasis, and tube formation. We also used a tumor implantation mouse model to show that secreted MVs containing overexpressed miR-29a/c significantly reduced the growth rate of the vasculature and tumors in vivo. To conclude, our results contribute to a novel anti-cancer strategy using miRNA-containing MVs to control tumor cell growth by blocking angiogenesis.

Causation by Diesel Exhaust Particles of Endothelial Dysfunctions in Cytotoxicity, Pro-inflammation, Permeability, and Apoptosis Induced by ROS Generation.

Epidemiological studies suggest that an increase of diesel exhaust particles (DEP) in ambient air corresponds to an increase in hospital-recorded myocardial infarctions within 48h after exposure. Among the many theories to explain this data are endothelial dysfunction and translocation of DEP into vasculature. The mechanisms for such DEP-induced vascular permeability remain unknown. One of the major mechanisms underlying the effects of DEP is suggested to be oxidative stress. Experiments have shown that DEP induce the generation of reactive oxygen species (ROS), such as superoxide anion and H2O2 in the HUVEC tube cells. Transcription factor Nrf2 is translocated to the cell nucleus, where it activates transcription of the antioxidative enzyme HO-1 and sequentially induces the release of vascular permeability factor VEGF-A. Furthermore, a recent study shows that DEP-induced intracellular ROS may cause the release of pro-inflammatory TNF-α and IL-6, which may induce endothelial permeability as well by promoting VEGF-A secretion independently of HO-1 activation. These results demonstrated that the adherens junction molecule, VE-cadherin, becomes redistributed from the membrane at cell-cell borders to the cytoplasm in response to DEP, separating the plasma membranes of adjacent cells. DEP were occasionally found in endothelial cell cytoplasm and in tube lumen. In addition, the induced ROS is cytotoxic to the endothelial tube-like HUVEC. Acute DEP exposure stimulates ATP depletion, followed by depolarization of their actin cytoskeleton, which sequentially inhibits PI3K/Akt activity and induces endothelial apoptosis. Nevertheless, high-dose DEP augments tube cell apoptosis up to 70% but disrupts the p53 negative regulator Mdm2. In summary, exposure to DEP affects parameters influencing vasculature permeability and viability, i.e., oxidative stress and its upregulated antioxidative and pro-inflammatory responses, which sequentially induce vascular permeability factor, VEGF-A release and disrupt cell-cell junction integrity. While exposure to a low dose of DEP actin triggers cytoskeleton depolarization, reduces PI3K/Akt activity, and induces a p53/Mdm2 feedback loop, a high dose causes apoptosis by depleting Mdm2. Addition of ROS scavenger N-acetyl cysteine suppresses DEP-induced oxidative stress efficiently and reduces subsequent damages by increasing endogenous glutathione.

Influence of scaffold morphology on co-cultures of human endothelial and adipose tissue-derived stem cells.

The interior of tissue engineering scaffolds must be vascularizable and allow adequate nutrients perfusion in order to ensure the viability of the cells colonizing them. The promotion of rapid vascularization of scaffolds is critical for thick artificial constructs. In the present study co-cultures of human endothelial and adipose tissue-derived stem cells have been performed in poly(ethyl acrylate) scaffolds with two different pore structures: grid-like (PEA-o) or sponge-like (PEA-s), in combination with a self-assembling peptide gel filling the pores, which aims to mimic the physiological niche. After 2 and 7 culture days, cell adhesion, proliferation and migration, the expression of cell surface markers like CD31 and CD90 and the release of VEGF were assessed by means of immunocytochemistry, scanning electronic microscopy, flow cytometry and ELISA analyses. The study demonstrated that PEA-s scaffolds promoted greater cell organization into tubular-like structures than PEA-o scaffolds, and this was enhanced by the presence of the peptide gel. Paracrine signaling from adipose cells significantly improved endothelial cell viability, proving the advantageous combination of this system for obtaining easily vascularizable tissue engineered grafts. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1523-1533, 2016.

Semipermeable Capsules Wrapping a Multifunctional and Self-regulated Co-culture Microenvironment for Osteogenic Differentiation.

A new concept of semipermeable reservoirs containing co-cultures of cells and supporting microparticles is presented, inspired by the multi-phenotypic cellular environment of bone. Based on the deconstruction of the “stem cell niche”, the developed capsules are designed to drive a self-regulated osteogenesis. PLLA microparticles functionalized with collagen I, and a co-culture of adipose stem (ASCs) and endothelial (ECs) cells are immobilized in spherical liquified capsules. The capsules are coated with multilayers of poly(L-lysine), alginate, and chitosan nano-assembled through layer-by-layer. Capsules encapsulating ASCs alone or in a co-culture with ECs are cultured in endothelial medium with or without osteogenic differentiation factors. Results show that osteogenesis is enhanced by the co-encapsulation, which occurs even in the absence of differentiation factors. These findings are supported by an increased ALP activity and matrix mineralization, osteopontin detection, and the up regulation of BMP-2, RUNX2 and BSP. The liquified co-capsules also act as a VEGF and BMP-2 cytokines release system. The proposed liquified capsules might be a valuable injectable self-regulated system for bone regeneration employing highly translational cell sources.

Effect of timed and localized release of BMP-2 and VEGF on vascularized osteogenesis in a 3D co-culture of human mesenchymal and endothelial stem cells

Effect of timed and localized release of BMP-2 and VEGF on vascularized osteogenesis in a 3D co-culture of human mesenchymal and endothelial stem cells

Activation of Melanocortin Receptors MC 1 and MC 5 Attenuates Retinal Damage in Experimental Diabetic Retinopathy.

We hypothesize that melanocortin receptors (MC) could activate tissue protective circuit in a model of streptozotocin- (STZ-) induced diabetic retinopathy (DR) in mice. At 12–16 weeks after diabetes induction, fluorescein angiography (FAG) revealed an approximate incidence of 80% microvascular changes, typical of DR, in the animals, without signs of vascular leakage. Occludin progressively decreased in the retina of mice developing retinopathy. qPCR of murine retina revealed expression of two MC receptors, Mc1r and Mc5r. The intravitreal injection (5 μL) of the selective MC1 small molecule agonist BMS-470539 (33 μmol) and the MC5 peptidomimetic agonist PG-901 (7.32 nM) elicited significant protection with regular course and caliber of retinal vessels, as quantified at weeks 12 and 16 after diabetes induction. Mouse retina homogenate settings indicated an augmented release of IL-1α, IL-1β, IL-6, MIP-1α, MIP-2α, MIP-3α, and VEGF from diabetic compared to nondiabetic mice. Application of PG20N or AGRP and MC5 and MC1 antagonist, respectively, augmented the release of cytokines, while the agonists BMS-470539 and PG-901 almost restored normal pattern of these mediators back to nondiabetic values. Similar changes were quantified with respect to Ki-67 staining. Finally, application of MC3-MC4 agonist/antagonists resulted to be inactive with respect to all parameters under assessment.