In vitro assays of angiogenesis for assessment of angiogenic and anti-angiogenic agents

Liquid-liquid phase transition as a basis for novel materials for skin repair and regeneration

Inorganic materials are of increasing interest not only for bone repair but also for other applications in regenerative medicine. In this study, the combined effects of energy-providing, regeneratively active inorganic polyphosphate (polyP) and also morphogenetically active pearl powder on wound healing were investigated. Aragonite, the mineralic constituent of pearl nacre and thermodynamically unstable form of crystalline calcium carbonate, was found to be converted into a soluble state in the presence of a Ca2+-containing wound exudate, particularly upon addition of sodium polyP (Na-polyP), driven by the transfer of Ca2+ ions from aragonite to polyP, leading to liquid-liquid phase separation to form an aqueous Ca-polyP coacervate. This process is further enhanced in the presence of Ca-polyP nanoparticles (Ca-polyP-NP). Kinetic studies revealed that the coacervation of polyP and nacre aragonite in wound exudate is a very rapid process that results in the formation of a stronger gel with a porous structure compared to polyP alone. Coacervate formation, enabled by phase transition of crystalline aragonite in the presence of Na-polyP/Ca-polyP-NP and wound exudate, could also be demonstrated in a hydroxyethyl cellulose-based hydrogel used for wound treatment. Furthermore, it is shown that Na-polyP/Ca-polyP-NP together with nacre aragonite strongly enhances the proliferation of mesenchymal stem cells and promotes microtube formation in the in vitro angiogenesis assay with HUVEC endothelial cells. The latter effect was confirmed by gene expression studies, applying real-time polymerase chain reaction, using the biomarker genes VEGF (vascular endothelial growth factor) and hypoxia-inducible factor-1 α (HIF-1α). Division of Escherichia coli is suppressed when suspended in a matrix containing Na-polyP/Ca-polyP-NP and aragonite. The potential medical relevance of these findings is supported by an animal study on genetically engineered diabetic mice (db/db), which demonstrated a marked increase in granulation tissue and microvessel formation in regenerating experimental wounds treated with Ca-polyP-NP compared to controls. Co-administration of aragonite significantly accelerated the wound healing-promoting effect of polyP in db/db mice. Based on these results, we propose that the ability of polyP to form a mixed coacervate with aragonite, in addition to its energy (ATP)-generating function, can decisively contribute to the regenerative activity of this polymer in wound repair.

Directed Design, Screening and Antiglycation Activity for 3-Substituted Thiazolium Derivatives, New Analogs of Alagebrium

Preliminary ab initio calculations led to the synthesis of novel substituted thiazolium salts, analogs of Alagebrium, which were further explored in vitro for their potential as inhibitors of the glycation reaction utilizing three distinct assays: inhibition of fluorescent AGEs formation, anticrosslinking, and deglycation. Despite the unidirectionality of the assays, distinct differences were observed in the mechanisms of interference and activity manifestation by the compounds. The gathered data permitted the formation of hypotheses about the molecular fragments of the studied antiglycators that are of utmost significance in each assay, thereby guiding future design endeavors. Potential mechanisms of actions are discussed therein. The compound 4-meth-yl-3-[2-(4-methylbiphenyl-4-yl)-2-oxoethyl] thiazolium bromide displayed high activity across all three assays, establishing it as a lead compound. The cytotoxicological properties of the compounds were evaluated using LDH and MTT assays. However, the lead compound exhibited cytotoxicity, indicating the need for additional investigations aimed at decreasing toxicity while maintaining activity. The targeted thiazolium salts were synthesized through an N-alkylation reaction between the corresponding thiazoles and phenacyl bromides.

Circulating miRNA-4701-3p as a predictive biomarker of cardiovascular disease which induces angiogenesis by inhibition of TOB2

Angiogenesis is mainly regulated by the delivery of VEGF-dependent signaling to cells. However, the angiogenesis mechanism regulated by VEGF-induced miRNA is still not understood. After VEGF treatment in HUVECs, we screened the changed miRNAs through small-RNA sequencing and found VEGF-induced miR-4701-3p. Furthermore, the GFP reporter gene was used to reveal that TOB2 expression was regulated by miR-4701-3p, and it was found that TOB2 and miR-4701-3p modulation could cause angiogenesis in an in-vitro angiogenic assay. Through the luciferase assay, it was confirmed that the activation of the angiogenic transcription factor MEF2 was regulated by the suppression and overexpression of TOB2 and miR-4701-3p. As a result, MEF2 downstream gene mRNAs that induce angiogenic function were regulated. We used the NCBI GEO datasets to reveal that the expression of TOB2 and MEF2 was significantly changed in cardiovascular disease. Finally, it was confirmed that the expression of circulating miR-4701-3p in the blood of myocardial infarction patients was remarkably increased. In patients with myocardial infarction, circulating miR-4701-3p was increased regardless of age, BMI, and sex, and showed high AUC levels in specificity and sensitivity analysis (AUROC) (AUC = 0.8451, 95 % CI 0.78-0.90). Our data showed TOB2-mediated modulation of MEF2 and its angiogenesis by VEGF-induced miR-4701-3p in vascular endothelial cells. In addition, through bioinformatics analysis using GEO data, changes in TOB2 and MEF2 were revealed in cardiovascular disease. We suggest that circulating miR-4701-3p has high potential as a biomarker for myocardial infarction.

Sulfamoylated Estradiol Analogs Targeting the Actin and Microtubule Cytoskeletons Demonstrate Anti-Cancer Properties In Vitro and In Ovo

The microtubule-disrupting agent 2-methoxyestradiol (2-ME) displays anti-tumor and anti-angiogenic properties, but its clinical development is halted due to poor pharmacokinetics. We therefore designed two 2-ME analogs in silico-an ESE-15-one and an ESE-16 one-with improved pharmacological properties. We investigated the effects of these compounds on the cytoskeleton in vitro, and their anti-angiogenic and anti-metastatic properties in ovo. Time-lapse fluorescent microscopy revealed that sub-lethal doses of the compounds disrupted microtubule dynamics. Phalloidin fluorescent staining of treated cervical (HeLa), metastatic breast (MDA-MB-231) cancer, and human umbilical vein endothelial cells (HUVECs) displayed thickened, stabilized actin stress fibers after 2 h, which rearranged into a peripheral radial pattern by 24 h. Cofilin phosphorylation and phosphorylated ezrin/radixin/moesin complexes appeared to regulate this actin response. These signaling pathways overlap with anti-angiogenic, extra-cellular communication and adhesion pathways. Sub-lethal concentrations of the compounds retarded both cellular migration and invasion. Anti-angiogenic and extra-cellular matrix signaling was evident with TIMP2 and P-VEGF receptor-2 upregulation. ESE-15-one and ESE-16 exhibited anti-tumor and anti-metastatic properties in vivo, using the chick chorioallantoic membrane assay. In conclusion, the sulfamoylated 2-ME analogs displayed promising anti-tumor, anti-metastatic, and anti-angiogenic properties. Future studies will assess the compounds for myeloproliferative effects, as seen in clinical applications of other drugs in this class.

A 1, 4-benzoquinone derivative isolated from Ardisia crispa (Thunb.) A. DC. root suppresses angiogenesis via its angiogenic signaling cascades

The root hexane extract of Ardisia crispa (ACRH), which belongs to the Primulaceae family, has been reported to possess anti-inflammatory, chemopreventive, anti-arthritic, and antiangiogenic activities. In this study, we isolated a p-benzoquinone derivative, 2-methoxy-6-undecyl-1,4-benzoquinone (AC2), from ACRH and investigated its potential antiangiogenic activity in human umbilical vein endothelial cells (HUVECs) and zebrafish embryo models. Prior to this study, AC2 was characterized using 1H NMR spectroscopy and MS. AC2 significantly suppressed HUVEC proliferation in a time-independent manner, with an IC50 value of 1.35 ± 0.05, 1.15 ± 0.02, and 1.00 ± 0.01 µg/mL at 24, 48, and 72 h, respectively. AC2 also induced apoptosis in HUVECs and significantly suppressed their migration, invasion, and tube formation in a concentration-dependent manner. Additionally, AC2 significantly attenuated most of the analyzed protein markers, including pro-MMP-2, VEGF-C, VEGF-D, angiopoietin-2, endothelin-1, fibroblast growth factor (FGF)-1, FGF-2, follistatin, heparin-binding epidermal growth factor-like growth factor (HB-EGF), and hepatocyte growth factor (HGF) at all tested concentrations. Furthermore, AC2 significantly inhibited zebrafish embryo intersegmental vessels (ISVs), confirming its antiangiogenic role. In conclusion, AC2 exhibits a potential anti-angiogenic effect by suppressing several proangiogenic and growth factors. Further studies are needed to investigate their effects on other excessive angiogenic diseases.

Development of a 3D Perfused In Vitro System to Assess Proangiogenic Properties of Compounds

Perturbation of angiogenesis is associated with a variety of diseases and pro- as well as antiangiogenic therapies are being actively explored. Additionally, unintended adverse drug effects on angiogenesis might lead to promotion of tumor progression and cardiovascular complications. Several tri-dimensional microfluidic vessel-on-chip systems have been described that allow a more accurate investigation of vascular physiology and pathology, compared to the two-dimensional static culture of endothelial cells. The OrganoPlate® angiogenesis-on-chip system has been demonstrated to be amenable to high-throughput screening for the antiangiogenic properties of molecules. We set out to adapt this system for high-throughput screening of molecules with proangiogenic properties. Our technical advancement of the OrganoPlate® angiogenesis-on-chip assay expands its applicability in the early screening of both anti- as well as proangiogenic properties of compounds for therapeutic modulation of angiogenesis as well as the identification of angiogenesis-associated drug-induced vascular toxicities.

Impaired proliferation and migration of HUVEC and melanoma cells by human anti-FGF2 mAbs derived from a murine hybridoma by guided selection

Disadvantages of using murine monoclonal antibodies (mAb) in human therapy, such as immunogenicity response, led to the development of technologies to transform murine antibodies into human antibodies. The murine anti-FGF2 3F12E7 mAb was proposed as a promising agent to treat metastatic melanoma tumors; once it blocks the FGF2, responsible for playing a role in tumor growth, angiogenesis, and metastasis. Considering the therapeutic potential of anti-FGF2 3F12E7 mAb and its limited use in humans due to its origin, we used this antibody as the template for a guided selection humanization technique to obtain human anti-FGF2 mAbs. Three Fab libraries (murine, hybrid, and human) were constructed for humanization. The libraries were phage-displayed, and the panning was performed against recombinant human FGF2 (rFGF2). The selected human variable light and heavy chains were cloned into AbVec vectors for full-length IgG expression into HEK293-F cells. Surface plasmon resonance analyses showed binding to rFGF2 of seven mAbs out of 20 expressed. Assays performed with these mAbs resulted in two that showed proliferation reduction and cell migration attenuation of HUVEC and SK-Mel-28 melanoma cells. In-silico analyses predicted that these two human anti-FGF2 mAbs interact with FGF2 at a similar patch of residues than the chimeric anti-FGF2 antibody, comprehending a region within the heparin-binding domains of FGF2, essential for its function. These results are comparable to those achieved by the murine anti-FGF2 3F12E7 mAb and showed success in the humanization process and selection of two human mAbs with the potential to inhibit undesirable FGF2 roles.

Supporting materials: Endothelial cells differentiated from patient dermal fibroblast-derived induced pluripotent stem cells resemble vascular malformations of Port Wine Birthmark

Background

Port wine birthmark (PWB) is a congenital vascular malformation resulting from developmentally defective endothelial cells (ECs). Developing clinically relevant disease models for PWB studies is currently an unmet need.

Objective

Our study aims to generate PWB-derived induced pluripotent stem cells (iPSCs) and iPSC-derived ECs that preserve disease-related phenotypes.

Methods

PWB iPSCs were generated by reprogramming lesional dermal fibroblasts and differentiated into ECs. RNA-seq was performed to identify differentially expressed genes (DEGs) and enriched pathways. The functional phenotypes of iPSC-derived ECs were characterized by capillary-like structure (CLS) formation in vitro and Geltrex plug-in assay in vivo .

Results

Human PWB and control iPSC lines were generated through reprogramming of dermal fibroblasts by introducing the "Yamanaka factors" (Oct3/4, Sox2, Klf4, c-Myc) into them; the iPSCs were successfully differentiated into ECs. These iPSCs and their derived ECs were validated by expression of a series of stem cell and EC biomarkers, respectively. PWB iPSC-derived ECs showed impaired CLS in vitro with larger perimeters and thicker branches as compared to control iPSC-derived ECs. In the plug-in assay, perfused human vasculature formed by PWB iPSC- derived ECs showed bigger perimeters and greater densities than those formed by control iPSC- derived ECs in severe combined immune deficient (SCID) mice. The transcriptome analysis showed that dysregulated pathways of stem cell differentiation, Hippo, Wnt, and focal adhesion persisted through differentiation of PWB iPSCs to ECs. Functional enrichment analysis showed that Hippo and Wnt pathway-related PWB DEGs are enriched for vasculature development, tube morphology, endothelium development, and EC differentiation. Further, members of the zinc finger (ZNF) gene family were overrepresented among the DEGs in PWB iPSCs. ZNF DEGs confer significant functions in transcriptional regulation, chromatin remodeling, protein ubiquitination, and retinoic acid receptor signaling. Furthermore, NF-kappa B, TNF, MAPK, and cholesterol metabolism pathways were dysregulated in PWB ECs as readouts of impaired differentiation.

Conclusions

PWB iPSC-derived ECs render a novel and clinically-relevant disease model by retaining pathological phenotypes. Our data demonstrate multiple pathways, such as Hippo and Wnt, NF-kappa B, TNF, MAPK, and cholesterol metabolism, are dysregulated, which may contribute to the development of differentiation-defective ECs in PWB.

Bulleted statements

What is already known about this topic?: Port Wine Birthmark (PWB) is a congenital vascular malformation with an incidence rate of 0.1 - 0.3 % per live births.PWB results from developmental defects in the dermal vasculature; PWB endothelial cells (ECs) have differentiational impairments.Pulse dye laser (PDL) is currently the preferred treatment for PWB; unfortunately, the efficacy of PDL treatment of PWB has not improved over the past three decades.What does this study add?: Induced pluripotent stem cells (iPSCs) were generated from PWB skin fibroblasts and differentiated into ECs.PWB ECs recapitulated their pathological phenotypes such as forming enlarged blood vessels in vitro and in vivo.Hippo and Wnt pathways were dysregulated in PWB iPSCs and ECs.Zinc-finger family genes were overrepresented among the differentially expressed genes in PWB iPSCs.Dysregulated NF-kappa B, TNF, MAPK, and cholesterol metabolism pathways were enriched in PWB ECs.What is the translational message?: Targeting Hippo and Wnt pathways and Zinc-finger family genes could restore the physiological differentiation of ECs.Targeting NF-kappa B, TNF, MAPK, and cholesterol metabolism pathways could mitigate the pathological progression of PWB.These mechanisms may lead to the development of paradigm-shifting therapeutic interventions for PWB.

A Human Cell-based Assay to Assess the Induction of Vasculature Formation for Non-genotoxic Carcinogenicity Testing Purposes: A Pilot Study

The induction of vasculature formation is proposed to be a significant mechanism behind the non-genotoxic carcinogenicity of a chemical. The vasculature formation model used in this study is based on the coculture of human primary HUVECs and hASCs. This model was used to develop an assay to assess the induction of vasculature formation. Three assay protocols, based on different conditions, were developed and compared in order to identify the optimal conditions required. Some serum supplements and growth factors were observed to be essential for initiating vasculature formation. Of the studied putative positive reference chemicals, aspartame, sodium nitrite, bisphenol A and nicotine treatment led to a clear induction of vasculature formation, but arsenic and cadmium treatment only led to a slight increase. This human cell-based assay has the potential to be used as one test within a next generation testing battery, to assess the non-genotoxic carcinogenicity of a chemical through the mechanism of vasculature formation induction.

PI(4,5)P2-dependent regulation of endothelial tip cell specification contributes to angiogenesis

Dynamic positioning of endothelial tip and stalk cells, via the interplay between VEGFR2 and NOTCH signaling, is essential for angiogenesis. VEGFR2 activates PI3K, which phosphorylates PI(4,5)P₂ to PI(3,4,5)P₃, activating AKT; however, PI3K/AKT does not direct tip cell specification. We report that PI(4,5)P₂ hydrolysis by the phosphoinositide-5-phosphatase, INPP5K, contributes to angiogenesis. INPP5K ablation disrupted tip cell specification and impaired embryonic angiogenesis associated with enhanced DLL4/NOTCH signaling. INPP5K degraded a pool of PI(4,5)P₂ generated by PIP5K1C phosphorylation of PI(4)P in endothelial cells. INPP5K ablation increased PI(4,5)P₂, thereby releasing β-catenin from the plasma membrane, and concurrently increased PI(3,4,5)P₃-dependent AKT activation, conditions that licensed DLL4/NOTCH transcription. Suppression of PI(4,5)P₂ in INPP5K-siRNA cells by PIP5K1C-siRNA, restored β-catenin membrane localization and normalized AKT signaling. Pharmacological NOTCH or AKT inhibition in vivo or genetic β-catenin attenuation rescued angiogenesis defects in INPP5K-null mice. Therefore, PI(4,5)P₂ is critical for β-catenin/DLL4/NOTCH signaling, which governs tip cell specification during angiogenesis.

Characterization of large extracellular vesicles (L-EV) derived from human regulatory macrophages (Mreg): novel mediators in wound healing and angiogenesis?

BACKGROUND

Large extracellular vesicles (L-EV) with a diameter between 1 and 10 µm are released by various cell types. L-EV contain and transport active molecules which are crucially involved in cell to cell communication. We have shown that secretory products of human regulatory macrophages (Mreg) bear pro-angiogenic potential in-vitro and our recent findings show that Mreg cultures also contain numerous large vesicular structures similar to L-EV with so far unknown characteristics and function.

AIM OF THIS STUDY

To characterize the nature of Mreg-derived L-EV (L-EV_Mreg) and to gain insights into their role in wound healing and angiogenesis.

METHODS

Mreg were differentiated using blood monocytes from healthy donors (N = 9) and L-EV_Mreg were isolated from culture supernatants by differential centrifugation. Characterization of L-EV_Mreg was performed by cell/vesicle analysis, brightfield/transmission electron microscopy (TEM), flow cytometry and proteome profiling arrays. The impact of L-EV_Mreg on wound healing and angiogenesis was evaluated by means of scratch and in-vitro tube formation assays.

RESULTS

Mreg and L-EV_Mreg show an average diameter of 13.73 ± 1.33 µm (volume: 1.45 ± 0.44 pl) and 7.47 ± 0.75 µm (volume: 0.22 ± 0.06 pl) respectively. Flow cytometry analyses revealed similarities between Mreg and L-EV_Mreg regarding their surface marker composition. However, compared to Mreg fewer L-EV_Mreg were positive for CD31 (P < 0.01), CD206 (P < 0.05), CD103 (P < 0.01) and CD45 (P < 0.05). Proteome profiling suggested that L-EV_Mreg contain abundant amounts of pro-angiogenic proteins (i.e. interleukin-8, platelet factor 4 and serpin E1). From a functional point of view L-EV_Mreg positively influenced in-vitro wound healing (P < 0.05) and several pro-angiogenic parameters in tube formation assays (all segment associated parameters, P < 0.05; number of meshes, P < 0.05).

CONCLUSION

L-EV_Mreg with regenerative and pro-angiogenic potential can be reproducibly isolated from in-vitro cultured human regulatory macrophages. We propose that L-EV_Mreg could represent a putative therapeutic option for the treatment of chronic wounds and ischemia-associated diseases.

Nature's palette: An emerging frontier for coloring dairy products

Consumers all across the world are looking for the most delectable and appealing foods, while also demanding products that are safer, more nutritious, and healthier. Substitution of synthetic colorants with natural colorants has piqued consumer and market interest in recent years. Due to increasing demand, extensive research has been conducted to find natural and safe food additives, such as natural pigments, that may have health benefits. Natural colorants are made up of a variety of pigments, many of which have significant biological potential. Because of the promising health advantages, natural colorants are gaining immense interest in the dairy industry. This review goes over the use of various natural colorants in dairy products which can provide desirable color as well as positive health impacts. The purpose of this review is to provide an in-depth look into the field of food (natural or synthetic) colorants applied in dairy products as well as their potential health benefits, safety, general trends, and future prospects  in food science and technology. In this paper, we listed a plethora of applications of natural colorants in various milk-based products.

Replacement in angiogenesis research: Studying mechanisms of blood vessel development by animal-free in vitro, in vivo and in silico approaches

Angiogenesis, the development of new blood vessels from pre-existing ones, is an essential process determining numerous physiological and pathological conditions. Accordingly, there is a high demand for research approaches allowing the investigation of angiogenic mechanisms and the assessment of pro- and anti-angiogenic therapeutics. The present review provides a selective overview and critical discussion of such approaches, which, in line with the 3R principle, all share the common feature that they are not based on animal experiments. They include in vitro assays to study the viability, proliferation, migration, tube formation and sprouting activity of endothelial cells in two- and three-dimensional environments, the degradation of extracellular matrix compounds as well as the impact of hemodynamic forces on blood vessel formation. These assays can be complemented by in vivo analyses of microvascular network formation in the chorioallantoic membrane assay and early stages of zebrafish larvae. In addition, the combination of experimental data and physical laws enables the mathematical modeling of tissue-specific vascularization, blood flow patterns, interstitial fluid flow as well as oxygen, nutrient and drug distribution. All these animal-free approaches markedly contribute to an improved understanding of fundamental biological mechanisms underlying angiogenesis. Hence, they do not only represent essential tools in basic science but also in early stages of drug development. Moreover, their advancement bears the great potential to analyze angiogenesis in all its complexity and, thus, to make animal experiments superfluous in the future.

VEGF-A and FGF4 Engineered C2C12 Myoblasts and Angiogenesis in the Chick Chorioallantoic Membrane

Angiogenesis is the formation of new blood vessels from pre-existing vessels. Adequate oxygen transport and waste removal are necessary for tissue homeostasis. Restrictions in blood supply can lead to ischaemia which can contribute to disease pathology. Vascular endothelial growth factor (VEGF) is essential in angiogenesis and myogenesis, making it an ideal candidate for angiogenic and myogenic stimulation in muscle. We established C2C12 mouse myoblast cell lines which stably express elevated levels of (i) human VEGF-A and (ii) dual human FGF4-VEGF-A. Both stably transfected cells secreted increased amounts of human VEGF-A compared to non-transfected cells, with the latter greater than the former. In vitro, conditioned media from engineered cells resulted in a significant increase in endothelial cell proliferation, migration, and tube formation. In vivo, this conditioned media produced a 1.5-fold increase in angiogenesis in the chick chorioallantoic membrane (CAM) assay. Delivery of the engineered myoblasts on Matrigel demonstrated continued biological activity by eliciting an almost 2-fold increase in angiogenic response when applied directly to the CAM assay. These studies qualify the use of genetically modified myoblasts in therapeutic angiogenesis for the treatment of muscle diseases associated with vascular defects.

cytoNet: Spatiotemporal network analysis of cell communities

We introduce cytoNet, a cloud-based tool to characterize cell populations from microscopy images. cytoNet quantifies spatial topology and functional relationships in cell communities using principles of network science. Capturing multicellular dynamics through graph features, cytoNet also evaluates the effect of cell-cell interactions on individual cell phenotypes. We demonstrate cytoNet’s capabilities in four case studies: 1) characterizing the temporal dynamics of neural progenitor cell communities during neural differentiation, 2) identifying communities of pain-sensing neurons in vivo, 3) capturing the effect of cell community on endothelial cell morphology, and 4) investigating the effect of laminin α4 on perivascular niches in adipose tissue. The analytical framework introduced here can be used to study the dynamics of complex cell communities in a quantitative manner, leading to a deeper understanding of environmental effects on cellular behavior. The versatile, cloud-based format of cytoNet makes the image analysis framework accessible to researchers across domains.

Anti-Angiogenic and Cytotoxicity Effects of Selachyl Alcohol Analogues

BACKGROUND

The active ingredients in the shark liver oil (SLO) mixture were found to be a group of etherlinked glycerol known as alkylglycerols (AKGs). During the last century, initial clinical use of the SLO mixture was for treating leukemias and later preventing radiation sickness from cancer x-ray therapy. Selachyl alcohol is one of the most abundant AKGs in the SLO mixture and it displayed strong activity in reducing lung metastasis number on a model of grafted tumor in mice (Lewis lung carcinoma cells).

OBJECTIVES

In this study, selachyl alcohol analogue containing methoxyl (7), gem-difluorinated (8), azide (9) and hydroxyl (10) group at the 12 position in the alkyl chain were synthesized and compared regarding their cytotoxicity and anti-migratory effects on Human Umbilical Vein Endothelial Cell line.

METHODS

AKGs 7-10 were synthesized according to the literature procedure. The cytotoxicity of the studied AKGs was evaluated by the MTT test and Human Umbilical Vein Endothelial Cell line (HUVEC) was used as an in vitro model to evaluate their anti-migratory effects.

RESULTS

The four AKGs have substantially the same toxicity threshold (≥ 12 μM), whereas they have an anti-migratory activity significantly different on endothelial cells. AKGs 9 and 10 significantly reduce the chemotactic migration induced by VEGF, but analogue (10) containing the hydroxyl group at the 12 position in the alkyl chain was the most potent anti-VEGF inhibitor.

CONCLUSION

We presented here a series of four synthetic selachyl alcohol analogues, among which AKGs 9 and 10 showed the ability to inhibit endothelial cell migration. The relationship structures and anti-VEGF effects of these analogues were also evaluated and discussed. Unnatural synthesized AKGs could be explored as one new source of anticancer agents.

Three-dimensional spheroids of choroid-retinal vascular endothelial cells as an in-vitro model for diabetic retinopathy: Proof-of-concept investigation

Diabetic retinopathy (DR) is a primary microvascular complication of diabetes mellitus and a vision-threatening condition. Vascular endothelial growth factor (VEGF) induces neovascularization and causes metabolic damage to the retinal and choroidal vasculature in diabetic patients. Existing drug screening models and treatment strategies for DR need to be refined through the establishment of relevant pre-clinical models, which may enable development of effective and safe therapies. The present study discusses the development of an in-vitro three-dimensional (3D) spheroid model, using RF/6A choroid-retinal vascular endothelial cells, to closely mimic the in-vivo disease condition. Compact, reproducibly-sized, viable and proliferating RF/6A spheroids were fabricated, as confirmed by microscopy, live/dead assay, cell proliferation assay and histological staining. In-vitro angiogenesis was studied by evaluating individual effects of VEGF and an anti-VEGF monoclonal antibody, Bevacizumab, and their combination on cellular proliferation and 3D endothelial sprout formation. VEGF stimulated angiogenic sprouting while Bevacizumab demonstrated a dose-dependent anti-angiogenic effect, as determined from the cellular proliferation observed and extent and length of sprouting. These investigations validated the potential of RF/6A spheroids in providing an alternative-to-animal, pathophysiologically-relevant model to facilitate pre-clinical and biomedical research related to DR.

•

Matrix-free three-dimensional RF/6A spheroids were developed and characterized.

•

VEGF-induced sprouting in RF/6A spheroids mimicked in-vivo vascular angiogenesis.

•

Bevacizumab showed clinically-relevant anti-angiogenic responses in spheroid model.

•

Proof-of-concept for in-vitro diabetic retinopathy model was developed.

A Novel High Content Angiogenesis Assay Reveals That Lacidipine, L-Type Calcium Channel Blocker, Induces In Vitro Vascular Lumen Expansion

Angiogenesis is a critical cellular process toward establishing a functional circulatory system capable of delivering oxygen and nutrients to the tissue in demand. In vitro angiogenesis assays represent an important tool for elucidating the biology of blood vessel formation and for drug discovery applications. Herein, we developed a novel, high content 2D angiogenesis assay that captures endothelial morphogenesis’s cellular processes, including lumen formation. In this assay, endothelial cells form luminized vascular-like structures in 48 h. The assay was validated for its specificity and performance. Using the optimized assay, we conducted a phenotypic screen of a library containing 150 FDA-approved cardiovascular drugs to identify modulators of lumen formation. The screening resulted in several L-type calcium channel blockers being able to expand the lumen space compared to controls. Among these blockers, Lacidipine was selected for follow-up studies. We found that the endothelial cells treated with Lacidipine showed enhanced activity of caspase-3 in the luminal space. Pharmacological inhibition of caspase activity abolished the Lacidipine-enhancing effect on lumen formation, suggesting the involvement of apoptosis. Using a Ca²⁺ biosensor, we found that Lacipidine reduces the intracellular Ca²⁺ oscillations amplitude in the endothelial cells at the early stage, whereas Lacidipine blocks these Ca²⁺ oscillations completely at the late stage. The inhibition of MLCK exhibits a phenotype of lumen expansion similar to that of Lacidipine. In conclusion, this study describes a novel high-throughput phenotypic assay to study angiogenesis. Our findings suggest that calcium signalling plays an essential role during lumen morphogenesis. L-type Ca²⁺ channel blockers could be used for more efficient angiogenesis-mediated therapies.

Detrimental impact of fine dust on zebrafish: Investigating a protective agent against ocular-damage using in vitro and in vivo models

Pollution caused by fine dust is becoming a global problem in the aquatic environment. Many studies have investigated the hazards that fine dust may pose to terrestrial organisms; however, information on the effects on aquatic environments remain limited. In this study, the physicochemical characteristics of the fine dust associated with the captured powder or liquid state were compared using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Raw fine dust (RFD), in the captured powder state, was suspended in water (SFD), and the elemental composition, morphology, and size distribution of both were analyzed. Zebrafish were used as a model to study the effects of SFD-exposure on aquatic organisms. A fatal malformation was observed in the integuments of zebrafish exposed to SFD, specifically in the exterior and interior eye tissues. Furthermore, the exposure of SFD to Tg (flk; EGFP) zebrafish remarkably increased ocular vessel diameter expansion along with blood flow velocity. Regarding vessel diameter expansion, EA.hy926 cells exposed to SFD were adversely affected, with a significant increase in cell migration and capillary-like structure formation, which are angiogenic markers. The SFD-induced angiogenesis in vitro and in vivo was dramatically restored to normal via α/β-adenosine isolated from the anti-angiogenic brown algae Ishige okamurae extract. Taken together, the current study presents solid evidence of the altered physicochemical characteristics of SFD compared to RFD, and the detrimental impact of SFD in an aquatic in vivo zebrafish model. In addition, the protective effect of α/β-adenosine, a marine natural product, on SFD-induced angiogenesis suggests that it can be used as an agent to reduce the adverse effects of SFD on aquatic animals.

Fabrication and characterization of a pro-angiogenic hydrogel derived from the human placenta

Various hydrogels derived from the xenogeneic extracellular matrix (ECM) have been utilised to promote the repair and reconstruction of numerous tissues; however, there are few studies on hydrogels derived from allogeneic specimens. Human placenta derived hydrogels have been used in the therapy of ischaemic myocardium; however, their physicochemical properties and effects on cellular behaviour remain elusive. As the human placenta retains pro-angiogenic growth factors, it is hypothesized that the placenta hydrogels possess the potential to improve angiogenesis. In this study, a soluble decellularized human placenta matrix generated using a modified method could be stored in a powder form and could be used to form a hydrogel in vitro. Effective decellularization was evaluated by analysing the DNA content and histology images. The placenta hydrogel exhibited a fibrous porous morphology and was injectable. Fourier transform infrared (FTIR) spectroscopy revealed that the placenta hydrogel contained both collagen and sulfated glycosaminoglycans (GAGs). In addition, immunofluorescence imaging and enzyme-linked immunosorbent assay (ELISA) showed that the placenta hydrogel retained pro-angiogenic growth factors, including VEGF and bFGF, and transforming growth factor-β1 (TGF-β1). Further in vitro and in vivo analyses confirmed that the placenta hydrogel exerted better pro-angiogenic effects than a collagen type I hydrogel. Histological data also showed that the placenta hydrogels did not elicit a grave inflammatory response. In conclusion, the results suggest that placenta hydrogels may be deemed an attractive scaffold for regenerative medicine applications, especially in promoting vessel formation.

In Vitro and In Vivo Evaluation of a Cyclic LyP-1-Modified Nanosystem for Targeted Endostatin Delivery in a KYSE-30 Cell Xenograft Athymic Nude Mice Model

This work investigated the use of LyP-1 as a homing peptide for p32 receptor targeting on the surface of an endostatin (ENT)-loaded chitosan-grafted nanosystem intended for intracellular delivery of ENT and mitochondrial targeting in a squamous cell carcinoma (SCC) cell line (KYSE-30) model. The angiogenic factors for VEGF-C and MMP2 were assessed with in vivo evaluation of the nanosystem upon ENT release and tumor necrosis in nude mice with a KYSE-30 cell xenograft. The LyP-1-modified nanosystem revealed a three-fold decrease in proliferation at 1000 µg/mL compared with the control and facilitated receptor-mediated cellular uptake and internalization. In addition, targeting of the Lyp-1-functionalized nanosystem to mitochondrial and nuclear proteins in vitro and in vivo was achieved. Up to 60% inhibition of KYSE-30 cell migration was observed and the expressions of VEGF-C and MMP-2 as angiogenic markers were reduced 3- and 2-fold, respectively. A marked reduction in tumor mass was recorded (43.25%) with the control, a 41.36% decrease with the nanoparticles and a 61.01% reduction with the LyP-1-modified nanosystem following treatment in mice. The LyP-1-functionalized nanosystem targeted tumor lymphatics, instigated nuclear rupture and mitochondrial distortion, and decreased cell proliferation and migration with inhibition of VEGF-C and MMP2 expression.

Adiponectin Influences FGF2 in the Developing Porcine Corpus Luteum

Luteal angiogenesis is regulated by pro-angiogenic hormones including fibroblast growth factor 2 (FGF2) and angiopoietin 1 (Ang1), which are regulated by the adipokine leptin during development. Another adipokine, adiponectin, exhibits an inverse relationship with leptin and has been identified in the CL. Therefore, it is hypothesized that adiponectin will influence pro-angiogenic hormones in the developing porcine CL. Crossbred sows were randomly allocated to one of two days of the estrous cycle, day 5 (D5; n = 4) or day 7 (D7; n = 5) for CL collection. Tissue was processed for immunohistochemical localization of adiponectin receptor 2 (AdipoR2), gene expression of FGF2, Ang1, leptin, AdipoR2, and cell culture for adiponectin treatment. The expression of AdipoR2 tended (p = 0.09) to be higher in D7 lutea and was more prevalently localized to the cell surface of large and small luteal cells than in D5 tissue. Adiponectin influenced (p ≤ 0.05) FGF2, leptin, and AdipoR2 gene expression relative to the dose and day (D5 or D7). Collectively, the evidence supports the supposition that adiponectin influences angiogenic factors in the developing CL.

In Vitro Co-culture of Fibroblast and Endothelial Cells to Assess Angiogenesis

Angiogenesis relies on the spatial and temporal coordination of endothelial migration and proliferation to form new blood vessels. This occurs through synchronous activation of multiple downstream pathways which facilitate vascular development. Proangiogenic growth factors and supporting extracellular matrix allow the formation of capillary-like tubules, reminiscent of microvascular beds, in vitro. In this chapter, we describe a methodology for the establishment of vascular networks by co-culture of endothelial cells and fibroblasts to facilitate the study of tubulogenic and angiogenic potential. We detail the use of siRNA mediated knockdown to deplete target genes of interest, in either the endothelial or fibroblast cells, to allow the assessment of their role in angiogenesis. Finally, we detail how these vascular networks may be stained using immunofluorescence to allow quantification of angiogenic potential in vitro.

In Vitro Models to Study Angiogenesis and Vasculature

The development of vasculature in vivo is an extremely complex process that requires temporal and spatial coordination between multiple cell types to produce an effective vessel. The formation of vasculature from preexisting blood vessels, known as angiogenesis, plays important roles in several physiological and pathological processes, including wound healing, organ development and growth, ischemia, inflammatory disorders, fibrosis, and cancer. Means to deconstruct these complicated biological systems are necessary to gain mechanistic insight into their development, function, and modulation that can be tested in in vivo models and ultimately the clinic. In this chapter, we will first review the classical in vitro techniques to study angiogenesis. Next, we will explore the exciting recent advances that rely on 3D multicellular systems to more accurately mimic vasculature development in vitro. Finally, we will discuss the applications of in vitro angiogenic methods to study related vasculature phenomena, such as vasculogenic mimicry.

Inhibition of Cytosolic Phospholipase A2α Induces Apoptosis in Multiple Myeloma Cells

Cytosolic phospholipase A2α (cPLA2α) is the rate-limiting enzyme in releasing arachidonic acid and biosynthesis of its derivative eicosanoids. Thus, the catalytic activity of cPLA2α plays an important role in cellular metabolism in healthy as well as cancer cells. There is mounting evidence suggesting that cPLA2α is an interesting target for cancer treatment; however, it is unclear which cancers are most relevant for further investigation. Here we report the relative expression of cPLA2α in a variety of cancers and cancer cell lines using publicly available datasets. The profiling of a panel of cancer cell lines representing different tissue origins suggests that hematological malignancies are particularly sensitive to the growth inhibitory effect of cPLA2α inhibition. Several hematological cancers and cancer cell lines overexpressed cPLA2α, including multiple myeloma. Multiple myeloma is an incurable hematological cancer of plasma cells in the bone marrow with an emerging requirement of therapeutic approaches. We show here that two cPLA2α inhibitors AVX420 and AVX002, significantly and dose-dependently reduced the viability of multiple myeloma cells and induced apoptosis in vitro. Our findings implicate cPLA2α activity in the survival of multiple myeloma cells and support further studies into cPLA2α as a potential target for treating hematological cancers, including multiple myeloma.

Novel Human Placenta-Based Extract for Vascularization Strategies in Tissue Engineering

There is critical unmet need for new vascularized tissues to support or replace injured tissues and organs. Various synthetic and natural materials were already established for use of two-dimensional (2D) and three-dimensional (3D) in vitro neovascularization assays, however, they still cannot mimic the complex functions of the sum of the extracellular matrix (ECM) in native intact tissue. Currently, this issue is only addressed by artificial products such as Matrigel^™, which comprises a complex mixture of ECM proteins, extracted from animal tumor tissue. Despite its outstanding bioactivity, the isolation from tumor tissue hinders its translation into clinical applications. Since nonhuman ECM proteins may cause immune reactions, as are frequently observed in clinical trials, human ECM proteins represent the best option when aiming for clinical applications. Here, we describe an effective method of isolating a human placenta substrate (hpS) that induces the spontaneous formation of an interconnected network of green fluorescence-labeled human umbilical vein endothelial cells (gfpHUVECs) in vitro. The substrate was biochemically characterized by using a combination of bicinchoninic acid (BCA) assay, DNA, and glycosaminoglycan (GAG) content assays, sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) analysis and Western blot, angiogenesis arrays, chromatographic thrombin detection, high performance liquid chromatography (HPLC)-based amino acid quantification analysis, and assessment of antimicrobial properties. 2D in vitro cell culture experiments have been performed to determine the vasculogenic potential of hpS, which demonstrated that cell networks developed on hpS show a significantly higher degree of complexity (number of tubules/junctions; total/mean tube length) when compared with Matrigel. As 3D cell culture techniques represent a more accurate representation of the in vivo condition, the substrate was 3D solidified using various natural polymers. 3D in vitro vasculogenesis assays have been performed by seeding gfpHUVECs in an hpS-fibrinogen clot. In conclusion, hpS provides a potent human/material-based alternative to xenogenic-material-based biomaterials for vascularization strategies in tissue engineering.

Isopimpinellin extends antiangiogenic effect through overexpression of miR-15b-5p and downregulating angiogenic stimulators

BACKGROUND

Angiogenesis is the formation of new blood vessels from an existing vasculature through a series of processes such as activation, proliferation, and directed migration of endothelial cells. Angiogenesis is instrumental in the metastatic spread of tumors. Isopimpinellin, a furanocoumarin group of phytochemicals, is an anticarcinogenic agent. However, no studies have proven its antiangiogenic effects. The current study thus aimed to screen the antiangiogenic effect of isopimpinellin.

METHODS AND RESULTS

Human Umblical Vein Endothelial Cell (HUVEC) as an in vitro model and zebrafish embryos as an in vivo model was used in this study. The experimental results showed that isopimpinellin effectively inhibited HUVEC proliferation, invasion, migration, and tube formation, which are the key steps in angiogenesis by markedly suppressing the expression of pro-angiogenic genes VEGF, AKT, and HIF-1α. In addition, isopimpinellin exerts its anti-angiogenic effect through the regulation of miR-15b-5p and miR-542-3p. Furthermore, in zebrafish embryos, isopimpinellin inhibited the development of intersegmental vessels (ISVs) through the significant downregulation of all pro-angiogenic genes vegf, vegfr2, survivin, angpt-1, angpt-2, and tie-2.

CONCLUSION

Collectively, these experimental findings offer novel insights into the antiangiogenic nature of isopimpinellin and open new avenues for therapeutic approaches.

3D tumor angiogenesis models: recent advances and challenges

The development of blood vessels, referred to as angiogenesis, is an intricate process regulated spatially and temporally through a delicate balance between the qualitative and quantitative expression of pro and anti-angiogenic molecules. As angiogenesis is a prerequisite for solid tumors to grow and metastasize, a variety of tumor angiogenesis models have been formulated to better understand the underlying mechanisms and associated clinical applications. Studies have demonstrated independent mechanisms inducing angiogenesis in tumors such as (a) HIF-1/VEGF mediated paracrine interactions between a cancer cell and endothelial cells, (b) recruitment of progenitor endothelial cells, and (c) vasculogenic mimicry. Moreover, single-cell sequencing technologies have indicated endothelial cell heterogeneity among organ systems including tumor tissues. However, existing angiogenesis models often rely upon normal endothelial cells which significantly differ from tumor endothelial cells exhibiting distinct (epi)genetic and metabolic signatures. Besides, the existence of intra-individual variations necessitates the development of improved tumor vascular model systems for personalized medicine. In the present review, we summarize recent advancements of 3D tumor vascular model systems which include (a) tissue engineering-based tumor models; (b) vascular organoid models, and (c) organ-on-chips and their importance in replicating the tumor angiogenesis along with the associated challenges to design improved models.

Tissues with Patterned Vessels or Protein Release Induce Vascular Chemotaxis in an In Vitro Platform

Engineered tissues designed for translational applications in regenerative medicine require vascular networks to deliver oxygen and nutrients rapidly to the implanted cells. A limiting factor of in vivo translation is the rapid and successful inosculation, or connection, of host and implanted vascular networks and subsequent perfusion of the implant. An approach gaining favor in vascular tissue engineering is to provide instructive cues from the engineered tissue to enhance host vascular penetration and connection with the implant. Here, we use a novel in vitro platform based on the aortic ring assay to evaluate the impact of patterned, endothelialized vessels or growth factor release from engineered constructs on preinosculative vascular cell outgrowth from surrogate host tissue in a controlled, defined environment, and introduce robust tools for evaluating vascular morphogenesis and chemotaxis. We demonstrate the creation of engineered vessels at the arteriole scale, which develop basement membrane, exhibit tight junctions, and actively sprout into the surrounding bulk hydrogel. Vessel-containing constructs are co-cultured adjacent to rodent aortic rings, and the resulting heterocellular outgrowth is quantified. Cells originating from the aortic ring migrate preferentially toward constructs containing engineered vessels with 1.5-fold faster outgrowth kinetics, 2.5-fold increased cellular density, and 1.6-fold greater network formation versus control (no endothelial cells and growth factor-reduced culture medium). Growth factor release from constructs with nonendothelialized channels and in reduced factor medium equivalently stimulates sustained vascular outgrowth distance, cellular density, and network formation, akin to engineered vessels in endothelial growth medium 2 (EGM-2) medium. In conclusion, we show that three-dimensional endothelialized patterned vessels or growth factor release stimulate a robust, host-derived vascular cell chemotactic response at early time points critical for instructive angiogenic cues. Further, we developed robust, unbiased tools to quantify metrics of vascular morphogenesis and preinosculative heterocellular outgrowth from rat aortic rings and demonstrated the utility of our complex, controlled environment, heterocellular in vitro platform. Impact statement Using a novel in vitro platform, we show that engineered constructs with patterned vessels or angiogenic growth factor release, two methods of instructing host revascularization responses, equivalently improve early host-derived vascular outgrowth. Our platform leverages the aortic ring assay in a tissue engineering context to study preinosculative vascular cell chemotaxis from surrogate host vascular cells in response to paracrine cues from co-cultured engineered tissues using robust, open-source quantification tools. Our accessible and flexible platform enables translationally focused studies in revascularization using implantable therapeutics containing prepatterned vessels with greater environmental control than in vivo studies to advance vascular tissue engineering.

Multi-target weapons: diaryl-pyrazoline thiazolidinediones simultaneously targeting VEGFR-2 and HDAC cancer hallmarks

In anticancer drug discovery, multi-targeting compounds have been beneficial due to their advantages over single-targeting compounds. For instance, VEGFR-2 has a crucial role in angiogenesis and cancer management, whereas HDACs are well-known regulators of epigenetics and have been known to contribute significantly to angiogenesis and carcinogenesis. Herein, we have reported nineteen novel VEGFR-2 and HDAC dual-targeting analogs containing diaryl-pyrazoline thiazolidinediones and their in vitro and in vivo biological evaluation. In particular, the most promising compound 14c has emerged as a dual inhibitor of VEGFR-2 and HDAC. It demonstrated anti-angiogenic activity by inhibiting in vitro HUVEC proliferation, migration, and tube formation. Moreover, an in vivo CAM assay showed that 14c repressed new capillary formation in CAMs. In particular, 14c exhibited cytotoxicity potential on different cancer cell lines such as MCF-7, K562, A549, and HT-29. Additionally, 14c demonstrated significant potency and selectivity against HDAC4 in the sub-micromolar range. To materialize the hypothesis, we also performed molecular docking on the crystal structures of both VEGFR-2 (PDB ID: 1YWN) and HDAC4 (PDB-ID: 4CBY), which corroborated the designing and biological activity. The results indicated that compound 14c could be a potential lead to develop more optimized multi-target analogs with enhanced potency and selectivity.

Double-edged Swords: Diaryl pyrazoline thiazolidinediones synchronously targeting cancer epigenetics and angiogenesis

In the present study, two novel series of compounds incorporating naphthyl and pyridyl linker were synthesized and biological assays revealed 5-((6-(2-(5-(2-chlorophenyl)-3-(4-fluorophenyl)-4,5-dihydro-1H-pyrazol-1-yl)-2-oxoethoxy) naphthalene-2-yl)methylene)thiazolidine-2,4-dione (14b) as the most potent dual inhibitors of vascular endothelial growth factors receptor-2 (VEGFR-2) and histone deacetylase 4 (HDAC4). Compounds 13b, 14b, 17f, and 21f were found to stabilize HDAC4; where, pyridyl linker swords were endowed with higher stabilization effects than naphthyl linker. Also, 13b and 14b showed best inhibitory activity on VEGFR-2 as compared to others. Compound 14b was most potent as evident by in-vitro and in-vivo biological assessments. It displayed anti-angiogenic potential by inhibiting endothelial cell proliferation, migration, tube formation and also suppressed new capillary formation in the growing chick chorioallantoic membranes (CAMs). It showed selectivity and potency towards HDAC4 as compared to other HDAC isoforms. Compound 14b (25 mg/kg, i.p.) also indicated exceptional antitumor efficacy on in-vivo animal xenograft model of human colorectal adenocarcinoma (HT-29). The mechanism of action of 14b was also confirmed by western blot.

A review of diabetic wound models-Novel insights into diabetic foot ulcer

Diabetic foot ulcer (DFU) is a major debilitating complication of diabetes. Many research investigations have been conducted with the aims to uncover the diabetic wound healing mechanisms, develop novel therapeutics, and screen bioactive wound dressings in order to improve the current management of DFU. These would have not been possible without the utilization of an appropriate wound model, especially in a diabetic wound context. This review focuses on the different in vitro research models used in DFU investigations such as the 2D scratch wound assay, 3D skin model, and 3D angiogenesis model as well as their limitations. The current efforts and challenges to apply the 2D and 3D in vitro models in a hyperglycemic context to provide insights into DFU modeling will be reviewed. Perspectives of utilizing 3D bioprinting and skin-on-the-chip model as a diabetic wound model in the future will also be highlighted. By leveraging knowledge from past experiences and current research, an improved experimental model for DFU is anticipated to be established in near future.

Pharmacological Preconditioning Improves the Viability and Proangiogenic Paracrine Function of Hydrogel-Encapsulated Mesenchymal Stromal Cells

The efficacy of cell therapy is limited by low retention and survival of transplanted cells in the target tissues. In this work, we hypothesize that pharmacological preconditioning with celastrol, a natural potent antioxidant, could improve the viability and functions of mesenchymal stromal cells (MSC) encapsulated within an injectable scaffold. Bone marrow MSCs from rat (rMSC) and human (hMSC) origin were preconditioned for 1 hour with celastrol 1 μM or vehicle (DMSO 0.1% v/v), then encapsulated within a chitosan-based thermosensitive hydrogel. Cell viability was compared by alamarBlue and live/dead assay. Paracrine function was studied first by quantifying the proangiogenic growth factors released, followed by assessing scratched HUVEC culture wound closure velocity and proliferation of HUVEC when cocultured with encapsulated hMSC. In vivo, the proangiogenic activity was studied by evaluating the neovessel density around the subcutaneously injected hydrogel after one week in rats. Preconditioning strongly enhanced the viability of rMSC and hMSC compared to vehicle-treated cells, with 90% and 75% survival versus 36% and 58% survival, respectively, after 7 days in complete media and 80% versus 64% survival for hMSC after 4 days in low serum media (p < 0.05). Celastrol-treated cells increased quantities of proangiogenic cytokines compared to vehicle-pretreated cells, with a significant 3.0-fold and 1.8-fold increase of VEGFa and SDF-1α, respectively (p < 0.05). The enhanced paracrine function of preconditioned MSC was demonstrated by accelerated growth and wound closure velocity of injured HUVEC monolayer (p < 0.05) in vitro. Moreover, celastrol-treated cells, but not vehicle-treated cells, led to a significant increase of neovessel density in the peri-implant region after one week in vivo compared to the control (blank hydrogel). These results suggest that combining cell pretreatment with celastrol and encapsulation in hydrogel could potentiate MSC therapy for many diseases, benefiting particularly ischemic diseases.

A novel substrate based on electrospun polyurethane nanofibers and electrosprayed polyvinyl alcohol microparticles for recombinant human erythropoietin delivery

After myocardial infarction caused by a heart attack, endothelial cells need to be preserved in order to regenerate new capillaries. Moreover, sufficient mechanical support is necessary for the infarcted myocardium to pump the blood. Herein, we designed a novel substrate containing polyurethane (PU) nanofibrous layers and recombinant human erythropoietin (rhEPO)-loaded microparticles for both controlled releases of rhEPO and mechanical support of myocardium. In this system, the single-layer (SL) and double-layer (DL) PU nanofibers were electrospun, and then microparticles with different rhEPO:polyvinyl alcohol (PVA) ratios were electrosprayed on the layers. The in vitro release behavior of rhEPO from SL substrates was not satisfactory, and then the study focused on DL patches in which the release profile was in accordance with Korsmeyer-Peppas model. The release exponent of 0.89 for the DL PU/120PVA:1rhEPO represented zero-order release. The results inferred that these substrates possessed highly tailored mechanical properties; Young's modulus and ultimate tensile strength of the substrates were 74-172 kPa and 7.4-9.9 MPa, respectively. The rhEPO release from the substrates was leading to the proper adhesion of endothelial cells and more than 95% cell viability. The results indicated that the patch of elastic nanofibers and microparticles offered a potential substrate for simultaneous rhEPO delivery to endothelial cells and also mechanically supporting the infarcted myocardium.

Bench-to-Bedside in Vascular Medicine: Optimizing the Translational Pipeline for Patients With Peripheral Artery Disease

Peripheral arterial disease is a growing worldwide problem with a wide spectrum of clinical severity and is projected to consume >$21 billion per year in the United States alone. While vascular researchers have brought several therapies to the clinic in recent years, few of these approaches have leveraged advances in high-throughput discovery screens, novel translational models, or innovative trial designs. In the following review, we discuss recent advances in unbiased genomics and broader omics technology platforms, along with preclinical vascular models designed to enhance our understanding of disease pathobiology and prioritize targets for additional investigation. Furthermore, we summarize novel approaches to clinical studies in subjects with claudication and ischemic ulceration, with an emphasis on streamlining and accelerating bench-to-bedside translation. By providing a framework designed to enhance each aspect of future clinical development programs, we hope to enrich the pipeline of therapies that may prevent loss of life and limb for those with peripheral arterial disease.

New Vascular Graft Using the Decellularized Human Chorion Membrane

The increase of both arterial occlusive diseases and coronary heart diseases leads to a higher demand for small-diameter vascular grafts (<6 mm). The gold standard for small-diameter vessel replacement is the use of autologous veins. Nevertheless, up to 30% of these patients need to use vascular grafts. Although synthetic polymers have been successfully used for the replacement of large-diameter vascular grafts (>6 mm), they are associated with thrombosis, intimal hyperplasia, calcification, and chronic inflammation when used as small-diameter vascular grafts. Therefore, natural materials have been studied for this application. In this study, a decellularized human chorion membrane (dHCM) vascular graft with a 3-4 mm diameter was created. Herein, the biocompatibility of dHCM with endothelial cells was demonstrated in vitro and ex ovo. Blood biocompatibility of dHCM was also shown by studying plasma protein adsorption, platelet adhesion and activation, and its hemolytic potential. Furthermore, dHCM antibacterial properties against Staphylococcus aureus were also studied. In summary, the dHCM reticular layer side presented all the needed characteristics to be used in the inner side of a vascular graft. Additionally, the mechanical properties of the dHCM tubular construct were studied, being similar to the ones of the saphenous vein, the gold standard for autologous small-diameter vessel replacement.

Mesenchymal Stem/Stromal Cells from the Placentae of Growth Restricted Pregnancies Are Poor Stimulators of Angiogenesis

The extensively branched vascular network within the placenta is vital for materno-fetal exchange, and inadequate development of this network is implicated in the pregnancy disorder fetal growth restriction (FGR), where babies are born pathologically small. Placental mesenchymal stem/stromal cells (pMSCs) and placental macrophages both reside in close proximity to blood vessels within the placenta, where they are thought to promote angiogenesis via paracrine mechanisms. However, the relationship between pMSCs, macrophages and placental vascular development has not yet been examined. We aimed to determine if inadequate paracrine stimulation of placental vascular development by pMSCs and macrophages during pregnancy may contribute to the inadequate vascularisation seen in FGR. Media conditioned by MSCs from FGR placentae significantly inhibited endothelial tube formation, compared to conditioned media derived from normal pMSCs. Similarly, macrophages exposed to media conditioned by FGR pMSCs were less able to stimulate endothelial tube formation in comparison to macrophages exposed to media conditioned by normal pMSCs. While MSCs from normal placentae produce a combination of angiogenic and anti-angiogenic cytokines, there were no significant differences in the secretion of the anti-angiogenic cytokines thrombospondin-1, insulin growth factor binding protein-4, or decorin between normal and FGR pMSCs that could explain how FGR pMSCs inhibited endothelial tube formation. Together, these data suggest a dysregulation in the secretion of paracrine factors by pMSCs in FGR placentae. These findings illustrate how cross talk between pro-angiogenic cell types in the placenta may be crucial for adequate angiogenesis.

PS1 FAD mutants decrease ephrinB2-regulated angiogenic functions, ischemia-induced brain neovascularization and neuronal survival

Microvascular pathology and ischemic lesions contribute substantially to neuronal dysfunction and loss that lead to Alzheimer disease (AD). To facilitate recovery, the brain stimulates neovascularization of damaged tissue via sprouting angiogenesis, a process regulated by endothelial cell (EC) sprouting and the EphB4/ephrinB2 system. Here, we show that in cultures of brain ECs, EphB4 stimulates the VE-cadherin/Rok-α angiogenic complexes known to mediate sprouting angiogenesis. Importantly, brain EC cultures expressing PS1 FAD mutants decrease the EphB4-stimulated γ-secretase cleavage of ephrinB2 and reduce production of the angiogenic peptide ephrinB2/CTF2, the VE-cadherin angiogenic complexes and EC sprouting and tube formation. These data suggest that FAD mutants may attenuate ischemia-induced brain angiogenesis. Supporting this hypothesis, ischemia-induced VE-cadherin angiogenic complexes, levels of neoangiogenesis marker Endoglin, vascular density, and cerebral blood flow recovery, are all decreased in brains of mouse models expressing PS1 FAD mutants. Ischemia-induced brain neuronal death and cognitive deficits also increase in these mice. Furthermore, a small peptide comprising the C-terminal sequence of peptide ephrinB2/CTF2 rescues angiogenic functions of brain ECs expressing PS1 FAD mutants. Together, our data show that PS1 FAD mutations impede the EphB4/ephrinB2-mediated angiogenic functions of ECs and impair brain neovascularization, neuronal survival and cognitive recovery following ischemia. Furthermore, our data reveal a novel brain angiogenic mechanism targeted by PS1 FAD mutants and a potential therapeutic target for ischemia-induced neurodegeneration. Importantly, FAD mutant effects occur in absence of neuropathological hallmarks of AD, supporting that such hallmarks may form downstream of mutant effects on neoangiogenesis and neuronal survival.

Inorganic Agents for Enhanced Angiogenesis of Orthopedic Biomaterials

Aseptic loosening of a permanent prosthesis remains one of the most common reasons for bone implant failure. To improve the fixation between implant and bone tissue as well as enhance blood vessel formation, bioactive agents are incorporated into the surface of the biomaterial. This study reviews and compares five bioactive elements (copper, magnesium, silicon, strontium, and zinc) with respect to their effect on the angiogenic behavior of endothelial cells (ECs) when incorporated on the surface of biomaterials. Moreover, it provides an overview of the state-of-the-art methodologies used for the in vitro assessment of the angiogenic properties of these elements. Two databases are searched using keywords containing ECs and copper, magnesium, silicon, strontium, and zinc. After applying the defined inclusion and exclusion criteria, 59 articles are retained for the final assessment. An overview of the angiogenic properties of five bioactive elements and the methods used for assessment of their in vitro angiogenic potential is presented. The findings show that silicon and strontium can effectively enhance osseointegration through the simultaneous promotion of both angiogenesis and osteogenesis. Therefore, their integration onto the surface of biomaterials can ultimately decrease the incidence of implant failure due to aseptic loosening.

Nanotechnology-Based Strategies to Evaluate and Counteract Cancer Metastasis and Neoangiogenesis

Cancer metastasis is the major cause of cancer-related morbidity and mortality. It represents one of the greatest challenges in cancer therapy, both because of the ability of metastatic cells to spread into different organs, and because of the consequent heterogeneity that characterizes primary and metastatic tumors. Nanomaterials can potentially be used as targeting or detection agents owing to unique chemical and physical features that allow tailored and tunable theranostic functions. This review highlights nanomaterial-based approaches in the detection and treatment of cancer metastasis, with a special focus on the evaluation of nanostructure effects on cell migration, invasion, and angiogenesis in the tumor microenvironment.

Minicircle-based expression of vascular endothelial growth factor in mesenchymal stromal cells from diverse human tissues

BACKGROUND

Mesenchymal stromal cells (MSC) have been exploited for the treatment of ischemic diseases given their angiogenic potential. Despite bone marrow (BM) being the most studied tissue source, cells with similar intrinsic properties can be isolated from adipose tissue (AT) and umbilical cord matrix (UCM). The present study aims to compare the angiogenic potential of MSC obtained from BM, AT and UCM that were genetically modified with vascular endothelial growth factor (VEGF)-encoding minicircle (MC) vectors. The overexpression of VEGF combined with the intrinsic properties of MSC could represent a promising strategy towards angiogenic therapies.

METHODS

We established a microporation-based protocol to transfect human MSC using VEGF-encoding MC (MC-VEGF). VEGF production levels were measured by an enzyme-linked immunosorbent assay and a quantitative polymerase chain reaction. The in vitro angiogenic potential of transfected cells was quantified using cell tube formation and migration functional studies.

RESULTS

MSC isolated from BM, AT or UCM showed similar levels of VEGF secretion after transfection with MC-VEGF. Those values were significantly higher when compared to non-transfected cells, indicating an effective enhancement of VEGF production. Transfected cells displayed higher in vitro angiogenic potential than non-transfected controls, as demonstrated by functional in vitro assays. No significant differences were observed among cells from different sources.

CONCLUSIONS

Minicircles can be successfully used to transiently overexpress VEGF in human MSC, regardless of the cell tissue source, representing an important advantage in a clinical context (i.e., angiogenic therapy) because a standard protocol might be applied to MSC of different tissue sources, which can be differentially selected according to the application (e.g., autologous versus allogeneic settings).

Suturable elastomeric tubular grafts with patterned porosity for rapid vascularization of 3D constructs

Vascularization is considered to be one of the key challenges in engineering functional 3D tissues. Engineering suturable vascular grafts containing pores with diameter of several tens of microns in tissue engineered constructs may provide an instantaneous blood perfusion through the grafts improving cell infiltration and thus, allowing rapid vascularization and vascular branching. The aim of this work was to develop suturable tubular scaffolds to be integrated in biofabricated constructs, enabling the direct connection of the biofabricated construct with the host blood stream, providing an immediate blood flow inside the construct. Here, tubular grafts with customizable shapes (tubes, Y-shape capillaries) and controlled diameter ranging from several hundreds of microns to few mm are fabricated based on poly(glycerol sebacate) (PGS) / poly(vinyl alcohol) (PVA) electrospun scaffolds. Furthermore, a network of pore channels of diameter in the order of 100 µm was machined by laser femtosecond ablation in the tube wall. Both non-machined and laser machined tubular scaffolds elongated more than 100% of their original size have shown suture retention, being 5.85 and 3.96 N/mm2 respectively. To demonstrate the potential of application, the laser machined porous grafts were embedded in gelatin methacryloyl (GelMA) hydrogels, resulting in elastomeric porous tubular graft/GelMA 3D constructs. These constructs were then co-seeded with osteoblast-like cells (MG-63) at the external side of the graft and endothelial cells (HUVEC) inside, forming a bone osteon model. The laser machined pore network allowed an immediate endothelial cell flow towards the osteoblasts enabling the osteoblasts and endothelial cells to interact and form 3D structures. This rapid vascularization approach could be applied, not only for bone tissue regeneration, but also for a variety of tissues and organs.

The homeostatic role of hydrogen peroxide, superoxide anion and nitric oxide in the vasculature

Reactive oxygen and nitrogen species are produced in a wide range of physiological reactions that, at low concentrations, play essential roles in living organisms. There is a delicate equilibrium between formation and degradation of these mediators in a healthy vascular system, which contributes to maintaining these species under non-pathological levels to preserve normal vascular functions. Antioxidants scavenge reactive oxygen and nitrogen species to prevent or reduce damage caused by excessive oxidation. However, an excessive reductive environment induced by exogenous antioxidants may disrupt redox balance and lead to vascular pathology. This review summarizes the main aspects of free radical biochemistry (formation, sources and elimination) and the crucial actions of some of the most biologically relevant and well-characterized reactive oxygen and nitrogen species (hydrogen peroxide, superoxide anion and nitric oxide) in the physiological regulation of vascular function, structure and angiogenesis. Furthermore, current preclinical and clinical evidence is discussed on how excessive removal of these crucial responses by exogenous antioxidants (vitamins and related compounds, polyphenols) may perturb vascular homeostasis. The aim of this review is to provide information of the crucial physiological roles of oxidation in the endothelium, vascular smooth muscle cells and perivascular adipose tissue for developing safer and more effective vascular interventions with antioxidants.

Potency of Tokishakuyakusan in treating preeclampsia: Drug repositioning method by in vitro screening of the Kampo library

Introduction

Preeclampsia therapy has not been established, except for the termination of pregnancy. The aim of this study was to identify a potential therapeutic agent from traditional Japanese medicine (Kampo) using the drug repositioning method.

Materials and methods

We screened a library of 74 Kampo to identify potential drugs for the treatment of preeclampsia. We investigated the angiogenic effects of these drugs using human umbilical vein endothelial cells (HUVECs). Enzyme-linked immunosorbent assays were performed to measure the levels of placental growth factor (PlGF) in conditioned media treated with 100 μg/mL of each drug. We assessed whether the screened drugs affected cell viability. We performed tube formation assays to evaluate the angiogenic effects of PlGF-inducing drugs. PlGF was measured after administering 10, 50, 100, and 200 μg/mL of the candidate drug in the dose correlation experiment, and at 1, 2, 3, 6, 12, and 24 h in the time course experiment. We also performed tube formation assays with the candidate drug and 100 ng/mL of soluble fms-like tyrosine kinase 1 (sFlt1). PlGF production by the candidate drug was measured in trophoblastic cells (BeWo and HTR-8/SVneo). The Mann-Whitney U test or one-way analyses of variance followed by the Newman-Keuls post-hoc test were performed. P–values < 0.05 were considered significant.

Results

Of the 7 drugs that induced PlGF, Tokishakuyakusan (TS), Shoseiryuto, and Shofusan did not reduce cell viability. TS significantly facilitated tube formation (P = 0.017). TS administration increased PlGF expression in a dose- and time-dependent manner. TS significantly improved tube formation, which was inhibited by sFlt1 (P = 0.033). TS also increased PlGF production in BeWo (P = 0.001) but not HTR-8/SVneo cells (P = 0.33).

Conclusions

By using the drug repositioning method in the in vitro screening of the Kampo library, we identified that TS may have a therapeutic potential for preeclampsia. Its newly found mechanisms involve the increase in PlGF production, and improvement of the antiangiogenic state.

An in vitro self-organized three-dimensional model of the blood-brain barrier microvasculature

The blood-brain barrier (BBB) protects the human brain from external aggression. Despite its great importance, very few in vitro models of the BBB reproducing its complex organization are available yet. Here we fabricated such a three-dimensional (3D) self-organized in vitro model of BBB microvasculature by means of a combination of collagen microfibers (CMF) and fibrin gel. The interconnected fibers supported human brain microvascular endothelial cell migration and the formation of a capillary-like network with a lumen diameter close to in vivo values. Fibrin, a protein involved in blood vessel repair, favored the further 3D conformation of the brain microvascular endothelial cells, astrocytes and pericytes, ensured gel cohesion and avoided shrinkage. The maturation of the BBB microvasculature network was stimulated by both the CMF and the fibrin in the hydrogel. The expression of essential tight-junction proteins, carriers and transporters was validated in regards to bidimensional simple coculture. The volume of gel drops was easily tunable to fit in 96-well plates. The cytotoxicity of D-Mannitol and its impacts on the microvascular network were evaluated, as an example of the pertinence of this 3D BBB capillary model for screening applications.

microRNA-322/424 promotes liver fibrosis by regulating angiogenesis through targeting CUL2/HIF-1α pathway

AIMS

To investigate the effects and mechanism of miR-322/424 in liver fibrosis.

MAIN METHODS

miR-322/424 expression in liver cirrhosis patients, mouse and rat liver fibrosis was determined by qPCR. Mice liver fibrosis was established by CCl₄, and intervened by miR-322/424 agomir or antagomir. Liver hydroxyproline content and Sirius red staining were used to evaluate collagen deposition. CD31 expression was used to evaluate liver microvessel density. In vitro, the effects of miR-322/424 mimic or inhibitor on human hepatic sinusoidal endothelial cells (HHSECs) migration and tube formation were investigated. A dual luciferase reporter assay was performed to confirm the direct interaction between miR-322/424 and Cullin2. mRNA expression of elongin B/C, Cullin2, and RBX1 was determined by qPCR. HIF-1α protein expression was determined by Western blotting.

KEY FINDINGS

miR-322/424 level in liver cirrhosis patients, mouse liver fibrosis induced by CCl₄ and BDL, and rat liver fibrosis induced by CCl₄ and dimethylnitrosamine was increased. miR-322/424 agomir exacerbated CCl₄-induced mouse liver fibrosis, whereas the opposite effect was observed for miR-322/424 antagomir. miR-322/424 agomir significantly upregulated liver CD31 expression; opposite effects occurred with miR-322/424 antagomir. In vitro, miR-322/424 mimic significantly promoted tube formation and cell migration, and increased von Willebrand factor expression, whereas miR-322/424 inhibitor had the opposite effect. Dual-Luciferase Reporter Assay identified Cullin2 as miR-322/424 target. miR-322/424 decreased the mRNA expression of elongin B/C, Cullin2, and RBX1 and increased HIF-1α protein expression in HHSECs.

SIGNIFICANCE

miR-322/424 plays a central role in the pathogenesis of liver fibrosis by targeting Cullin2, and enhancing HIF-1α-mediated hepatic angiogenesis.

In situ sprayed NIR-responsive, analgesic black phosphorus-based gel for diabetic ulcer treatment

The treatment of diabetic ulcer (DU) remains a major clinical challenge due to the complex wound-healing milieu that features chronic wounds, impaired angiogenesis, persistent pain, bacterial infection, and exacerbated inflammation. A strategy that effectively targets all these issues has proven elusive. Herein, we use a smart black phosphorus (BP)-based gel with the characteristics of rapid formation and near-infrared light (NIR) responsiveness to address these problems. The in situ sprayed BP-based gel could act as 1) a temporary, biomimetic "skin" to temporarily shield the tissue from the external environment and accelerate chronic wound healing by promoting the proliferation of endothelial cells, vascularization, and angiogenesis and 2) a drug "reservoir" to store therapeutic BP and pain-relieving lidocaine hydrochloride (Lid). Within several minutes of NIR laser irradiation, the BP-based gel generates local heat to accelerate microcirculatory blood flow, mediate the release of loaded Lid for "on-demand" pain relief, eliminate bacteria, and reduce inflammation. Therefore, our study not only introduces a concept of in situ sprayed, NIR-responsive pain relief gel targeting the challenging wound-healing milieu in diabetes but also provides a proof-of-concept application of BP-based materials in DU treatment.

The effect of pramlintide, an antidiabetic amylin analogue, on angiogenesis-related markers in vitro

Background and purpose:

Irregularities of angiogenesis may participate in the pathogenesis of diabetes complications. Pramlintide is an amylin analogue administered for the treatment of type 1 and type 2 diabetes. The present investigation aimed at surveying the effect of pramlintide on angiogenesis-related markers in human umbilical vein endothelial cells (HUVECs).

Experimental approach:

The proliferation of cells was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) method. The effect of pramlintide on migration was estimated by Transwell® assay. in vitro evaluation of angiogenesis was performed by tube formation assay. The secretion of vascular endothelial growth factor (VEGF) to the supernatant of HUVECs was measured by an enzyme- linked immunosorbent assay (ELISA) kit. All experiments were performed in triplicate.

Findings / Results:

Pramlintide exhibited no inhibitory effect on HUVECs proliferation. It significantly increased cell migration at the concentration of 1 μg/mL. Pramlintide (1 μg/mL) also enhanced average tubules length, size, and the mean number of junctions. However, there was not any significant change in VEGF release from HUVECs.

Conclusion and implications:

Findings of this research revealed the effect of pramlintide on angiogenesis- related markers via enhancing migration and tubulogenesis in vitro, suggesting a worthwhile proposition for further clinical researches on improving vascular complications and healing of diabetic wounds.

Fentanyl stimulates tumor angiogenesis via activating multiple pro-angiogenic signaling pathways

Angiogenesis plays a vital role in tumor progression and metastasis. To better understand the role of anesthesia in tumor biology, we previously reported that bupivacaine displayed the inhibitory effects in endothelial cells. In this work, we demonstrated that fentanyl, an opioid medication commonly used in cancer patients, stimulated tumor angiogenesis. We found that fentanyl at nanomolar concentrations significantly stimulated capillary network formation of human lung tumor-associated endothelial cell (HLT-EC) in a similar manner as vascular endothelial growth factor (VEGF), and furthermore that the stimulatory effect of fentanyl was mainly involved in early stage of HLT-EC vascular structure assembly. Particularly, fentanyl significantly increased HLT-EC growth and migration. Fentanyl also protected HLT-EC from apoptosis induced by growth factor withdrawal. In contrast, the same concentrations of fentanyl did not affect human lung cancer cell growth and survival. Fentanyl stimulated migration of some but not all tested human lung cancer cells. Mechanism analysis suggested that fentanyl activates multiple pro-angiogenic signaling pathways, including VEGFR2/FAK/PI3K/Akt and small GTPases. Our work systematically demonstrates that fentanyl stimulates tumor angiogenesis via activating multiple pro-angiogenic signaling pathways. Our findings highlight the potential adverse effect of fentanyl in cancer patients.