Recent advances in vascular development

HM-3-HSA exhibits potent anti-angiogenesis and antitumor activity in hepatocellular carcinoma

HM-3-HSA is an antitumor fusion protein which improved the pharmacokinetics of HM-3. Previous studies reported that HM-3-HSA enhanced antitumor activity of HM-3 in melanoma cells. However, the efficacy and the mechanism of HM-3-HSA in hepatocellular carcinoma, especially its effect on tumor angiogenesis, have not been elucidated. Herein, we showed that HM-3-HSA significantly inhibited the H22 and SMMC-7721 tumor xenografts growth and tumor angiogenesis in vivo, indicating the antitumor activity exerted by HM-3-HSA was closely corrected with its potency on tumor angiogenesis. To investigate the anti-angiogenic mechanism, we evaluated the efficacy of HM-3-HSA in HUVECs in vitro. The results showed that multiple steps of tumor angiogenesis, including endothelial cell proliferation, migration, invasion and tube formation, were substantially inhibited by HM-3-HSA. Mechanism investigations revealed that HM-3-HSA could bind HUVECs via integrin αvβ3 and α5β1 and inhibited phosphorylation of the downstream protein kinases including FAK, Src and PI3 K. Our study was the first to report the activity of HM-3-HSA against hepatocellular carcinoma and tumor angiogenesis as well as the underlying mechanism by which HM-3-HSA to exert its anti-angiogenic activity.

Molecular biomarkers in cardiac hypertrophy

Cardiac hypertrophy is characterized by an increase in myocyte size in the absence of cell division. This condition is thought to be an adaptive response to cardiac wall stress resulting from the enhanced cardiac afterload. The pathogenesis of heart dysfunction, which is one of the primary causes of morbidity and mortality in elderly people, is often associated with myocardial remodelling caused by cardiac hypertrophy. In order to well understand the potential mechanisms, we described the molecules involved in the development and progression of myocardial hypertrophy. Increasing evidence has indicated that micro‐RNAs are involved in the pathogenesis of cardiac hypertrophy. In addition, molecular biomarkers including vascular endothelial growth factor B, NAD‐dependent deacetylase sirtuin‐3, growth/differentiation factor 15 and glycoprotein 130, also play important roles in the development of myocardial hypertrophy. Knowing the regulatory mechanisms of these biomarkers in the heart may help identify new molecular targets for the treatment of cardiac hypertrophy.

Shear stress, arterial identity and atherosclerosis

In the developing embryo, the vasculature first takes the form of a web-like network called the vascular plexus. Arterial and venous differentiation is subsequently guided by the specific expression of genes in the endothelial cells that provide spatial and temporal cues for development. Notch1/4, Notch ligand delta-like 4 (Dll4), and Notch downstream effectors are typically expressed in arterial cells along with EphrinB2, whereas chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) and EphB4 characterise vein endothelial cells. Haemodynamic forces (blood pressure and blood flow) also contribute importantly to vascular remodelling. Early arteriovenous differentiation and local blood flow may hold the key to future inflammatory diseases. Indeed, despite the fact that atherosclerosis risk factors such as smoking, hypertension, hypercholesterolaemia, and diabetes all induce endothelial cell dysfunction throughout the vasculature, plaques develop only in arteries, and they localise essentially in vessel branch points, curvatures and bifurcations, where blood flow (and consequently shear stress) is low or oscillatory. Arterial segments exposed to high blood flow (and high laminar shear stress) tend to remain plaque-free. These observations have led many to investigate what particular properties of arterial or venous endothelial cells confer susceptibility or protection from plaque formation, and how that might interact with a particular shear stress environment.

Rhamnazin attenuates inflammation and inhibits alkali burn-induced corneal neovascularization in rats

The purpose of our study was to determine whether rhamnazin inhibits corneal neovascularization in the rat alkali burn model, and alleviates the inflammatory response of the cornea. Rhamnazin inhibited the proliferation of HUVEC cells in a dose-dependent manner, and it also inhibited the migration and luminal formation of HUVEC cells. 20 μM rhamnazin eye drops were applied to an animal model of corneal alkali burn neovascularization 4 times a day for 14 days. The corneal neovascularization in the rhamnazin group was obviously less than that in the PBS control group. In the rhamnazin group, the inflammatory index of the cornea decreased gradually over time, whereas the inflammatory index of the PBS group decreased only slightly with time. The corneal CNV area in the PBS group was significantly larger than that in the rhamnazin group. The expression level of VEGF protein of the rhamnazin group was lower than that in the PBS group, and the expression level of PEDF was significantly higher than that of the PBS group. Rhamnazin downregulated the expression of VEGFR2 protein and decreased the expression levels of p-STAT3, p-MAPK and p-Akt proteins. This study provides a new idea for the study of the molecular mechanism of corneal neovascularization.

The purpose of our study was to determine whether rhamnazin inhibits corneal neovascularization in the rat alkali burn model, and alleviates the inflammatory response of the cornea.

Assessment of in vivo anti-tumor activity of human umbilical vein endothelial cell vaccines prepared by various antigen forms

Human umbilical vein endothelial cell (HUVEC) vaccine has been proved as an effective whole-cell vaccine, but the modest therapeutic anti-tumor efficiency limits its clinical use. Various antigen forms, including paraformaldehyde-fixed HUVEC, glutaraldehyde-fixed HUVEC, HUVEC lysate and live HUVEC, have been intensively used in HUVEC vaccine preparation, however, the most effective antigen form has not yet been identified. In the present study, these four commonly used antigen forms were used to prepare vaccines named Para-Fixed-EC, Glu-Fixed-EC, Lysate-EC, and Live-EC respectively, and the anti-tumor efficacy of these four vaccines was investigated. Results showed that Live-EC exhibited the most favorable anti-tumor growth and metastasis effects among the four vaccines in both H22 hepatocellular carcinoma and Lewis lung cancer models. High titer anti-HUVEC antibodies were detected in Live-EC immunized mice sera, and the immune sera of Live-EC group could significantly inhibit HUVEC proliferation and tube formation. Moreover, T cells isolated from Live-EC immunized mice exhibited strong cytotoxicity against HUVEC cells, with an increasing IFN-γ and decreasing Treg production in Live-EC immunized mice. Finally, CD31 immunohistochemical analysis of the excised tumors verified a significant reduction in vessel density after Live-EC vaccination, which was in accordance with the anti-tumor efficiency. Taken together, all the results proved that live HUVEC was the most effective antigen form to induce robust HUVEC specific antibody and CTL responses, which could lead to the significant inhibition of tumor growth and metastasis. We hope the present findings would provide a rationale for the further optimization of HUVEC vaccine.

Eupafolin Exhibits Potent Anti-Angiogenic and Antitumor Activity in Hepatocellular Carcinoma

Eupafolin is a flavonoid extracted from the common sage herb which has been used in China as traditional medicine. Previous studies had reported that eupafolin had antioxidative, anti-inflammatory and antitumor effects. However, the function and the mechanism of eupafolin to exert its antitumor activity, especially its effect on tumor angiogenesis, have not been elucidated. Herein, we showed that eupafolin significantly inhibited vascular endothelial growth factor (VEGF)-induced cell proliferation, migration and tube formation of human umbilical vascular endothelial cells (HUVECs) in a dose-dependent manner. Meanwhile, the new blood microvessels induced by VEGF in the matrigel plug were also substantially suppressed by eupafolin. The results of HCC xenograft experiments demonstrated eupafolin remarkably inhibited tumor growth and tumor angiogenesis in vivo, suggesting the antitumor activity exerted by eupafolin was closely correlated with its potency on tumor angiogenesis. Mechanism investigations revealed that eupafolin significantly blocked VEGF-induced activation of VEGFR2 in HUVEC cells as well as its downstream signaling pathway. In addition to the effect on endothelial cells, through inhibiting Akt activity in tumor cells, VEGF secretion in HepG2 was dramatically decreased after eupafolin treatment. Our study was the first to report the activity of eupafolin against tumor angiogenesis as well as the underlying mechanism by which eupafolin to exert its anti-angiogenic activity.

Laminar flow downregulates Notch activity to promote lymphatic sprouting

The major function of the lymphatic system is to drain interstitial fluid from tissue. Functional drainage causes increased fluid flow that triggers lymphatic expansion, which is conceptually similar to hypoxia-triggered angiogenesis. Here, we have identified a mechanotransduction pathway that translates laminar flow-induced shear stress to activation of lymphatic sprouting. While low-rate laminar flow commonly induces the classic shear stress responses in blood endothelial cells and lymphatic endothelial cells (LECs), only LECs display reduced Notch activity and increased sprouting capacity. In response to flow, the plasma membrane calcium channel ORAI1 mediates calcium influx in LECs and activates calmodulin to facilitate a physical interaction between Krüppel-like factor 2 (KLF2), the major regulator of shear responses, and PROX1, the master regulator of lymphatic development. The PROX1/KLF2 complex upregulates the expression of DTX1 and DTX3L. DTX1 and DTX3L, functioning as a heterodimeric Notch E3 ligase, concertedly downregulate NOTCH1 activity and enhance lymphatic sprouting. Notably, overexpression of the calcium reporter GCaMP3 unexpectedly inhibited lymphatic sprouting, presumably by disturbing calcium signaling. Endothelial-specific knockouts of Orai1 and Klf2 also markedly impaired lymphatic sprouting. Moreover, Dtx3l loss of function led to defective lymphatic sprouting, while Dtx3l gain of function rescued impaired sprouting in Orai1 KO embryos. Together, the data reveal a molecular mechanism underlying laminar flow-induced lymphatic sprouting.

Endothelial Cells

Endothelial cells are a constitutive part of the heart and vasculature and form a crucial link between the cardiovascular system and the immune system. Besides their commonly accepted roles in angiogenesis, hemostasis, and the regulation of vascular tone, they are an essential and active component of immune responses. Expression of a range of innate pattern recognition receptors allows them to respond to inflammatory stimulation, and they control immune cell recruitment and extravasation into target tissues throughout the body.In this chapter, I will therefore summarize classical endothelial cell properties and functions and their cross talk with the immune system as well as the operational immunological role of endothelial cells in facilitating immune responses.

Antagonist antibodies to vascular endothelial growth factor receptor 2 (VEGFR-2) as anti-angiogenic agents

Interaction of numerous signaling pathways in endothelial and mesangial cells results in exquisite control of the process of physiological angiogenesis, with a central role played by vascular endothelial growth factor receptor 2 (VEGFR-2) and its cognate ligands. However, deregulated angiogenesis participates in numerous pathological processes. Excessive activation of VEGFR-2 has been found to mediate tissue-damaging vascular changes as well as the induction of blood vessel expansion to support the growth of solid tumors. Consequently, therapeutic intervention aimed at inhibiting the VEGFR-2 pathway has become a mainstay of treatment in cancer and retinal diseases. In this review, we introduce the concepts of physiological and pathological angiogenesis, the crucial role played by the VEGFR-2 pathway in these processes, and the various inhibitors of its activity that have entered the clinical practice. We primarily focus on the development of ramucirumab, the antagonist monoclonal antibody (mAb) that inhibits VEGFR-2 and has recently been approved for use in patients with gastric, colorectal, and lung cancers. We examine in-depth the pre-clinical studies using DC101, the mAb to mouse VEGFR-2, which provided a conceptual foundation for the role of VEGFR-2 in physiological and pathological angiogenesis. Finally, we discuss further clinical development of ramucirumab and the future of targeting the VEGF pathway for the treatment of cancer.

Association between miR-181b and PKG 1 in myocardial hypertrophy and its clinical implications

The aim of this study was to explore the microRNA (miR)-181b expression in myocardial hypertrophy and to investigate its association with cGMP-dependent protein kinase type I (PKG 1) in an in vitro model. The miR-181b level in the peripheral blood was determined in patients with myocardial hypertrophy, and an in vitro model was established via phenylephrine (PE) treatment. Reverse transcription-quantitative polymerase chain reaction analysis and western blotting were performed to detect the expression levels of miR-181b, PKG 1 and hypertrophy-related genes. The results revealed that the expression of miR-181b was elevated in the peripheral blood of patients with myocardial hypertrophy, and this may have contributed to the pathology and progression of the disease. When the primary myocardial cells were treated with PE, microscopic observation and flow cytometry revealed significant hypertrophy. Furthermore, upregulation of myocardial hypertrophy-related genes, including β-myosin heavy chain, α-sarcomeric actinin and atrial natriuretic peptide, was observed. The miR-181b expression level in the PE-treated cells was elevated, while the mRNA and protein expression levels of PKG 1 were decreased, indicating a negative correlation between miR-181b and PKG 1 in myocardial hypertrophy. In addition, when the PE-treated primary myocardial cells were transfected with miR-181b inhibitor, the reduced PKG 1 expression was restored and the myocardial hypertrophy alleviated, as indicated by the reduced cellular sizes and decreased expression levels of the myocardial hypertrophy-related genes. In conclusion, miR-181b expression has been shown to be upregulated in myocardial hypertrophy, and this may play a role in the pathogenesis of the disease by regulating the expression of PKG 1. The present findings suggest that miR-181b is a promising molecular indicator for the clinical diagnosis and treatment of cardiac hypertrophy.

Modulation of endothelial cell phenotype by physical activity: impact on obesity-related endothelial dysfunction

Increased levels of physical activity are associated with reduced cardiovascular disease (CVD) risk and mortality in obesity and diabetes. Available evidence suggests that local factors, including local hemodynamics, account for a significant portion of this CVD protection, and numerous studies have interrogated the therapeutic benefit of physical activity/exercise training in CVD. Less well established is whether basal differences in endothelial cell phenotype between/among vasculatures related to muscle recruitment patterns during activity may account for reports of nonuniform development of endothelial dysfunction in obesity. This is the focus of this review. We highlight recent work exploring the vulnerability of two distinct vasculatures with established differences in endothelial cell phenotype. Specifically, based largely on dramatic differences in underlying hemodynamics, arteries perfusing soleus muscle (slow-twitch muscle fibers) and those perfusing gastrocnemius muscle (fast-twitch muscle fibers) in the rat exhibit an exercise training-like versus an untrained endothelial cell phenotype, respectively. In the context of obesity, therefore, arteries to soleus muscle exhibit protection from endothelial dysfunction compared with vulnerable arteries to gastrocnemius muscle. This disparate vulnerability is consistent with numerous animal and human studies, demonstrating increased skeletal muscle blood flow heterogeneity in obesity coincident with reduced muscle function and exercise intolerance. Mechanistically, we highlight emerging areas of inquiry exploring novel aspects of hemodynamic-sensitive signaling in endothelial cells and the time course of physical activity-associated endothelial adaptations. Lastly, further exploration needs to consider the impact of endothelial heterogeneity on the development of endothelial dysfunction because endothelial dysfunction independently predicts CVD events.

Notch signal integration in the vasculature during remodeling

Notch signaling plays many important roles in homeostasis and remodeling in the vessel wall, and serves a critical role in the communication between endothelial cells and smooth muscle cells. Within blood vessels, Notch signaling integrates with multiple pathways by mechanisms including direct protein–protein interaction, cooperative or synergistic regulation of signal cascades, and co-regulation of transcriptional targets. After establishment of the mature blood vessel, the spectrum and intensity of Notch signaling change during phases of active remodeling or disease progression. These changes can be mediated by regulation via microRNAs and protein stability or signaling, and corresponding changes in complementary signaling pathways. Notch also affects endothelial cells on a system level by regulating key metabolic components. This review will outline the most recent findings of Notch activity in blood vessels, with a focus on how Notch signals integrate with other molecular signaling pathways controlling vascular phenotype.

Manipulation of a VEGF-Notch signaling circuit drives formation of functional vascular endothelial progenitors from human pluripotent stem cells

Human pluripotent stem cell (hPSC)-derived endothelial lineage cells constitutes a promising source for therapeutic revascularization, but progress in this arena has been hampered by a lack of clinically-scalable differentiation protocols and inefficient formation of a functional vessel network integrating with the host circulation upon transplantation. Using a human embryonic stem cell reporter cell line, where green fluorescent protein expression is driven by an endothelial cell-specific VE-cadherin (VEC) promoter, we screened for > 60 bioactive small molecules that would promote endothelial differentiation, and found that administration of BMP4 and a GSK-3β inhibitor in an early phase and treatment with VEGF-A and inhibition of the Notch signaling pathway in a later phase led to efficient differentiation of hPSCs to the endothelial lineage within six days. This sequential approach generated > 50% conversion of hPSCs to endothelial cells (ECs), specifically VEC⁺CD31⁺CD34⁺CD14⁻KDR^high endothelial progenitors (EPs) that exhibited higher angiogenic and clonogenic proliferation potential among endothelial lineage cells. Pharmaceutical inhibition or genetical knockdown of Notch signaling, in combination with VEGF-A treatment, resulted in efficient formation of EPs via KDR⁺ mesodermal precursors and blockade of the conversion of EPs to mature ECs. The generated EPs successfully formed functional capillary vessels in vivo with anastomosis to the host vessels when transplanted into immunocompromised mice. Manipulation of this VEGF-A-Notch signaling circuit in our protocol leads to rapid large-scale production of the hPSC-derived EPs by 12- to 20-fold vs current methods, which may serve as an attractive cell population for regenerative vascularization with superior vessel forming capability compared to mature ECs.

Transcriptional changes in organoculture of full-thickness human skin following topical application of all-trans retinoic acid

Objective

Retinoids are used as therapeutic agents for numerous skin diseases, for example, psoriasis, acne and keratinization disorders. The same substances have also been recognized in the treatment for hyperpigmentation disorders such as melasma.

Other studies on photo-damaged skin have shown that retinoids reduce wrinkles, surface roughness, mottled pigmentation, and visual skin appearance as a whole. We tested the hypothesis that an organoculture of full-thickness human skin could be used as a preclinical model to investigate the retinoid transcriptional profile in human skin in vitro.

Methods

Full-thickness skin explants were exposed to topically applied all-trans retinoic acid (RA) for 24 h. The gene expression profile was analysed using oligonucleotide microarrays, and data were validated with real-time (RT) PCR.

Results

We showed that the expression of 93 genes was significantly altered more than twofold. Several of the altered genes, for example, KRT4, CYP26 and LCN2, have previously been shown to be affected by RA in keratinocyte monocultures, reconstructed epidermis and skin biopsies from patients treated topically or orally with RA. In addition, genes, such as SCEL, NRIP1, DGAT2, RDH12 EfnB2, MAPK14, SAMD9 and CEACAM6 not previously reported to be affected by RA in human skin, were identified for the first time in this study.

Conclusion

The results in the present study show that full-thickness human explants represent a valuable pre-clinical model for studying the effects of retinoids in skin.

Résumé

Extracellular matrix synthesis in vascular disease: hypertension, and atherosclerosis

Extracellular matrix (ECM) within the vascular network provides both a structural and regulatory role. The ECM is a dynamic composite of multiple proteins that form structures connecting cells within the network. Blood vessels are distended by blood pressure and, therefore, require ECM components with elasticity yet with enough tensile strength to resist rupture. The ECM is involved in conducting mechanical signals to cells. Most importantly, ECM regulates cellular function through chemical signaling by controlling activation and bioavailability of the growth factors. Cells respond to ECM by remodeling their microenvironment which becomes dysregulated in vascular diseases such hypertension, restenosis and atherosclerosis. This review examines the cellular and ECM components of vessels, with specific emphasis on the regulation of collagen type I and implications in vascular disease.

UBIAD1-mediated vitamin K2 synthesis is required for vascular endothelial cell survival and development

Multi-organ animals, such as vertebrates, require the development of a closed vascular system to ensure the delivery of nutrients to, and the transport of waste from, their organs. As a result, an organized vascular network that is optimal for tissue perfusion is created through not only the generation of new blood vessels but also the remodeling and maintenance of endothelial cells via apoptotic and cell survival pathways. Here, we show that UBIAD1, a vitamin K2/menaquinone-4 biosynthetic enzyme, functions cell-autonomously to regulate endothelial cell survival and maintain vascular homeostasis. From a recent vascular transgene-assisted zebrafish forward genetic screen, we have identified a ubiad1 mutant, reddish/reh, which exhibits cardiac edema as well as cranial hemorrhages and vascular degeneration owing to defects in endothelial cell survival. These findings are further bolstered by the expression of UBIAD1 in human umbilical vein endothelial cells and human heart tissue, as well as the rescue of the reh cardiac and vascular phenotypes with either zebrafish or human UBIAD1. Furthermore, we have discovered that vitamin K2, which is synthesized by UBIAD1, can also rescue the reh vascular phenotype but not the reh cardiac phenotype. Additionally, warfarin-treated zebrafish, which have decreased active vitamin K, display similar vascular degeneration as reh mutants, but exhibit normal cardiac function. Overall, these findings reveal an essential role for UBIAD1-generated vitamin K2 to maintain endothelial cell survival and overall vascular homeostasis; however, an alternative UBIAD1/vitamin K-independent pathway may regulate cardiac function.

Endothelial cell-specific lymphotoxin-β receptor signaling is critical for lymph node and high endothelial venule formation

The development of lymph nodes (LNs) and formation of LN stromal cell microenvironments is dependent on lymphotoxin-β receptor (LTβR) signaling. In particular, the LTβR-dependent crosstalk between mesenchymal lymphoid tissue organizer and hematopoietic lymphoid tissue inducer cells has been regarded as critical for these processes. Here, we assessed whether endothelial cell (EC)-restricted LTβR signaling impacts on LN development and the vascular LN microenvironment. Using EC-specific ablation of LTβR in mice, we found that conditionally LTβR-deficient animals failed to develop a significant proportion of their peripheral LNs. However, remnant LNs showed impaired formation of high endothelial venules (HEVs). Venules had lost their cuboidal shape, showed reduced segment length and branching points, and reduced adhesion molecule and constitutive chemokine expression. Due to the altered EC-lymphocyte interaction, homing of lymphocytes to peripheral LNs was significantly impaired. Thus, this study identifies ECs as an important LTβR-dependent lymphoid tissue organizer cell population and indicates that continuous triggering of the LTβR on LN ECs is critical for lymphocyte homeostasis.

Tight control - decision-making during T cell-vascular endothelial cell interaction

Vascular endothelial cells (ECs) form the inner layer of blood vessels and exert crucial functions during immune reactions including coagulation, inflammation, and regulation of innate immunity. Importantly, ECs can interact with T cells in an antigen-specific, i.e., T cell receptor-dependent manner. In this review, we will discuss EC actions and reactions during acute inflammation and focus on the interaction of T cells with ECs at two vascular sites: the high endothelial venule (HEV) of lymph nodes, and the vascular lesion during transplant vasculopathy (TV). HEVs are characterized by a highly active endothelium that produces chemoattracting factors and expresses adhesion molecules to facilitate transit of lymphocytes into the lymph node (LN) parenchyma. Yet, T cell-EC interaction at this anatomical location results neither in T cell activation nor tolerization. In contrast, the endothelium at sites of chronic inflammation, such as solid organ transplants, can promote T cell activation by upregulation of major histocompatibility complex (MHC) and costimulatory molecules. Importantly, a major function of ECs in inflamed tissues must be the maintenance of vascular integrity including the efficient attenuation of effector T cells that may damage the vascular bed. Thus, antigen-specific T cell-EC interaction is characterized by a tightly controlled balance between immunological ignorance, immune activation, and tolerization.