Blood-vessel formation: Bridges that guide and unite

Role of macrophages in vascular calcification: From the perspective of homeostasis

Vascular calcification (VC) is a crucial risk factor for the high morbidity and mortality associated with cardiovascular and cerebrovascular diseases. With the global population aging, the incidence of VC is escalating annually. However, due to its silent clinical process, VC often results in irreversible clinical outcomes. Inflammation is a core element in the VC process, and macrophages are the major inflammatory cells. Due to their diverse origins, microenvironments, and polarization states, macrophages exhibit significant heterogeneity, exerting strong effects on the occurrence, development, and even the regression of VC. In this review, we summarize the origin, distribution, classification, and surface markers of macrophages. Simultaneously, we explore the mechanisms by which macrophages maintain homeostasis or regulate inflammation, including the macrophage-mediated regulation of VC through the release of inflammatory factors, osteogenic genes, extracellular vesicles, and alterations in efferocytosis. Finally, we discuss research targeting inflammation and macrophages to develop novel therapeutic regimens for preventing and treating VC.

Identification of hub genes in placental dysfunction and recurrent pregnancy loss through transcriptome data mining: A meta-analysis

Recurrent pregnancy loss (RPL) is a condition characterized by the loss of two or more pregnancies before 20 weeks of gestation. The causes of RPL are complex and can be due to a variety of factors, including genetic, immunological, hormonal, and environmental factors. This transcriptome data mining study was done to explore the differentially expressed genes (DEGs) and related pathways responsible for pathogenesis of RPL using an Insilco approach. RNAseq datasets from the Gene Expression Omnibus (GEO) database was used to extract RNAseq datasets of RPL. Meta-analysis was done by ExpressAnalyst. The functional and pathway enrichment analysis of DEGs were performed using KEGG and BINGO plugin of Cytoscape software. Protein-protein interaction was done using STRING and hub genes were identified. A total of 91 DEGs were identified, out of which 10 were downregulated and 81 were upregulated. Pathway analysis indicated that majority of DEGs were enriched in immunological pathways (IL-17 signalling pathway, TLR-signalling pathway, autoimmune thyroid disease), angiogenic VEGF-signalling pathway and cell-cycle signalling pathways. Of these, 10 hub genes with high connectivity were selected (CXCL8, CCND1, FOS, PTGS2, CTLA4, THBS1, MMP2, KDR, and CD80). Most of these genes are involved in maintenance of immune response at maternal-fetal interface. Further, in functional enrichment analyses revealed the highest node size in regulation of biological processes followed by cellular processes, their regulation and regulation of multicellular organismal process. This in-silico transcriptomics meta-analysis findings could potentially contribute in identifying novel biomarkers and therapeutic targets for RPL, which could lead to the development of new diagnostic and therapeutic strategies for this condition.

The role of lymphatic vessels in corneal fluid homeostasis and wound healing

The cornea, essential for vision, is normally avascular, transparent, and immune-privileged. However, injuries or infections can break this privilege, allowing blood and lymphatic vessels to invade, potentially impairing vision and causing immune responses. This review explores the complex role of corneal lymphangiogenesis in health and diseases. Traditionally, the cornea was considered devoid of lymphatic vessels, a phenomenon known as "corneal (lymph)angiogenic privilege." Recent advances in molecular markers have enabled the discovery of lymphatic vessels in the cornea under certain conditions. Several molecules contribute to preserving both immune and lymphangiogenic privileges. Lymphangiogenesis, primarily driven by VEGF family members, can occur directly or indirectly through macrophage recruitment. Corneal injuries and diseases disrupt these privileges, reducing graft survival rates following transplantation. However, modulation of lymphangiogenesis offers potential interventions to promote graft survival and expedite corneal edema resolution.This review underscores the intricate interplay between lymphatic vessels, immune privilege, and corneal pathologies, highlighting innovative therapeutic possibilities. Future investigations should explore the modulation of lymphangiogenesis to enhance corneal health and transparency, as well as corneal graft survival, and this benefits patients with various corneal conditions.

The novel role of lymphatic vessels in the pathogenesis of ocular diseases

Historically, the eye has been considered as an organ free of lymphatic vessels. In recent years, however, it became evident, that lymphatic vessels or lymphatic-like vessels contribute to several ocular pathologies at various peri- and intraocular locations. The aim of this review is to outline the pathogenetic role of ocular lymphatics, the respective molecular mechanisms and to discuss current and future therapeutic options based thereon. We will give an overview on the vascular anatomy of the healthy ocular surface and the molecular mechanisms contributing to corneal (lymph)angiogenic privilege. In addition, we present (i) current insights into the cellular and molecular mechanisms occurring during pathological neovascularization of the cornea triggered e.g. by inflammation or trauma, (ii) the role of lymphatic vessels in different ocular surface pathologies such as dry eye disease, corneal graft rejection, ocular graft versus host disease, allergy, and pterygium, (iii) the involvement of lymphatic vessels in ocular tumors and metastasis, and (iv) the novel role of the lymphatic-like structure of Schlemm's canal in glaucoma. Identification of the underlying molecular mechanisms and of novel modulators of lymphangiogenesis will contribute to the development of new therapeutic targets for the treatment of ocular diseases associated with pathological lymphangiogenesis in the future. The preclinical data presented here outline novel therapeutic concepts for promoting transplant survival, inhibiting metastasis of ocular tumors, reducing inflammation of the ocular surface, and treating glaucoma. Initial data from clinical trials suggest first success of novel treatment strategies to promote transplant survival based on pretransplant corneal lymphangioregression.

Injectable bioactive glass/sodium alginate hydrogel with immunomodulatory and angiogenic properties for enhanced tendon healing

Tendon healing is a complex process involving inflammation, proliferation, and remodeling, eventually achieving a state of hypocellularity and hypovascularity. Currently, few treatments can satisfactorily restore the structure and function of native tendon. Bioactive glass (BG) has been shown to possess immunomodulatory and angiogenic properties. In this study, we investigated whether an injectable hydrogel fabricated of BG and sodium alginate (SA) could be applied to enhance tenogenesis following suture repair of injured tendon. We demonstrated that BG/SA hydrogel significantly accelerated tenogenesis without inducing heterotopic ossification based on histological analysis. The therapeutic effect could attribute to increased angiogenesis and M1 to M2 phenotypic switch of macrophages within 7 days post-surgery. Morphological characterization demonstrated that BG/SA hydrogel partially reverted the pathological changes of Achilles tendon, including increased length and cross-sectional area (CSA). Finally, biomechanical test showed that BG/SA hydrogel significantly improved ultimate load, failure stress, and tensile modulus of the repaired tendon. In conclusion, administration of an injectable BG/SA hydrogel can be a novel and promising therapeutic approach to augment Achilles tendon healing in conjunction with surgical intervention.

Decidual macrophages in recurrent spontaneous abortion

Recurrent spontaneous abortion (RSA) is defined as two or more pregnancy loss, affecting the happiness index of fertility couples. The mechanisms involved in the occurrence of RSA are not clear to date. The primary problem for the maternal immune system is how to establish and maintain the immune tolerance to the semi-allogeneic fetuses. During the pregnancy, decidual macrophages mainly play an important role in the immunologic dialogue. The purpose of this study is to explore decidual macrophages, and to understand whether there is a connection between these cells and RSA by analyzing their phenotypes and functions. Pubmed, Web of Science and Embase were searched. The eligibility criterion for this review was evaluating the literature about the pregnancy and macrophages. Any disagreement between the authors was resolved upon discussion and if required by the judgment of the corresponding author. We summarized the latest views on the phenotype, function and dysfunction of decidual macrophages to illuminate its relationship with RSA.

Netrin-1 in Post-stroke Neuroprotection: Beyond Axon Guidance Cue

BACKGROUND

Stroke, especially ischemic stroke, is a leading disease associated with death and long-term disability with limited therapeutic options. Neuronal death caused by vascular impairment, programmed cell death and neuroinflammation has been proven to be associated with increased stroke severity and poor stroke recovery. In light of this, a development of neuroprotective drugs targeting injured neurons is urgently needed for stroke treatment. Netrin-1, known as a bifunctional molecule, was originally described to mediate the repulsion or attraction of axonal growth by interacting with its different receptors. Importantly, accumulating evidence has shown that netrin-1 can manifest its beneficial functions to brain tissue repair and neural regeneration in different neurological disease models.

OBJECTIVE

In this review, we focus on the implications of netrin-1 and its possibly involved pathways on neuroprotection after ischemic stroke, through which a better understanding of the underlying mechanisms of netrin-1 may pave the way to novel treatments.

METHODS

Peer-reviewed literature was recruited by searching databases of PubMed, Scopus, Embase, and Web of Science till the year 2021.

CONCLUSION

There has been certain evidence to support the neuroprotective function of netrin-1 by regulating angiogenesis, autophagy, apoptosis and neuroinflammation after stroke. Netrin-1 may be a promising drug candidate in reducing stroke severity and improving outcomes.

Denervation Affected Skin Wound Healing in a Modified Rat Model

Introduction: Lacking of normal innervation increases the chance of chronic wounds and recurrence of ulceration. Various rodent models are designed to reveal nerve-wound relationship but present many limitations to mimic human wound which heals primarily by re-epithelialization rather than contraction in rodents. This article tested a modified rat model of denervated wound healing to better mimic clinical common denervated wounds. Material and Methods: The wounds formed on right hind paws of 18 SD rats served as the experimental (denervated) group and the left side as contra-lateral control (non-denervated). The denervation was achieved through sciatic and femoral nerve co-transection and the control side underwent sham-surgery 3 days prior to a skin punch wound formation on both sides. Wound closure rate was calculated under digital photographing. Loss of innervation and affected healing process was confirmed by histological analyses. Results: Truncation of the sciatic and femur nerve successfully denervated the skin of the hind paw and resulted in a significantly declined healing rate, prolonged inflammation, weakened dermal contraction, hindered macrophage recruitment, retarded re-epithelialization and collagen deposition, decreased angiogenesis and epidermal proliferation, and persisted epidermal apoptosis compared to the innervated contra-lateral control. Conclusion: Wound on denervated dorsal pedis in rats can be used to study denervated skin healing in multiple histological process. We believe that this model will assist in understanding the underlying mechanism of nerve-wound relationship and identifying new treatment strategies that can be more rapidly translated into clinical practice.

Immunomodulation by endothelial cells - partnering up with the immune system?

Blood vessel endothelial cells (ECs) have long been known to modulate inflammation by regulating immune cell trafficking, activation status and function. However, whether the heterogeneous EC populations in various tissues and organs differ in their immunomodulatory capacity has received insufficient attention, certainly with regard to considering them for alternative immunotherapy. Recent single-cell studies have identified specific EC subtypes that express gene signatures indicative of phagocytosis or scavenging, antigen presentation and immune cell recruitment. Here we discuss emerging evidence suggesting a tissue-specific and vessel type-specific immunomodulatory role for distinct subtypes of ECs, here collectively referred to as 'immunomodulatory ECs' (IMECs). We propose that IMECs have more important functions in immunity than previously recognized, and suggest that these might be considered as targets for new immunotherapeutic approaches.

Novel Pathways for Targeting Tumor Angiogenesis in Metastatic Breast Cancer

Breast cancer is the most common cancer affecting women and is the second leading cause of cancer related death worldwide. Angiogenesis, the process of new blood vessel development from pre-existing vasculature, has been implicated in the growth, progression, and metastasis of cancer. Tumor angiogenesis has been explored as a key therapeutic target for decades, as the blockade of this process holds the potential to reduce the oxygen and nutrient supplies that are required for tumor growth. However, many existing anti-angiogenic approaches, such as those targeting Vascular Endothelial Growth Factor, Notch, and Angiopoietin signaling, have been associated with severe side-effects, limited survival advantage, and enhanced cancer regrowth rates. To address these setbacks, alternative pathways involved in the regulation of tumor angiogenesis are being explored, including those involving Bone Morphogenetic Protein-9 signaling, the Sonic Hedgehog pathway, Cyclooxygenase-2, p38-mitogen-activated protein kinase, and Chemokine Ligand 18. This review article will introduce the concept of tumor angiogenesis in the context of breast cancer, followed by an overview of current anti-angiogenic therapies, associated resistance mechanisms and novel therapeutic targets.

Epigenetic Regulation of the Vascular Endothelium by Angiogenic LncRNAs

The functional properties of the vascular endothelium are diverse and heterogeneous between vascular beds. This is especially evident when new blood vessels develop from a pre-existing closed cardiovascular system, a process termed angiogenesis. Endothelial cells are key drivers of angiogenesis as they undergo a highly choreographed cascade of events that has both exogenous (e.g., hypoxia and VEGF) and endogenous regulatory inputs. Not surprisingly, angiogenesis is critical in health and disease. Diverse therapeutics target proteins involved in coordinating angiogenesis with varying degrees of efficacy. It is of great interest that recent work on non-coding RNAs, especially long non-coding RNAs (lncRNAs), indicates that they are also important regulators of the gene expression paradigms that underpin this cellular cascade. The protean effects of lncRNAs are dependent, in part, on their subcellular localization. For instance, lncRNAs enriched in the nucleus can act as epigenetic modifiers of gene expression in the vascular endothelium. Of great interest to genetic disease, they are undergoing rapid evolution and show extensive inter- and intra-species heterogeneity. In this review, we describe endothelial-enriched lncRNAs that have robust effects in angiogenesis.

Targeting tumor vascularization: promising strategies for vascular normalization

Tumor recurrence after the clinical cure of tumor often results from the presence of an abnormal microenvironment, including an aberrant vasculature. The tumor microenvironment is rich in pro-angiogenic factors but lacks pro-maturation factors. Pro-angiogenic conditions in the tumor microenvironment, such as hypoxia, are double-edged swords, promoting both the repair of normal tissues and the development of an abnormal blood vessel network. The coexistence of perfusion and hypoxic zones and uneven blood vessel distribution in tumor tissues profoundly influence tumor deterioration, recurrence, and metastasis. Traditional anti-angiogenic therapies have shown limited efficacy, and promote drug resistance, and even metastasis. In contrast, vascular normalization therapy induces a more physiological-like state, leading to better outcomes and fewer side effects. Vascular normalization entails modifying the tumor vascular system to improve tumor oxygenation and substance transport, thereby contributing to improving the efficacy of radiotherapy, chemotherapy, and immunotherapy. This review mainly focuses on the process of tumor vascularization; potential therapeutic targets, including cells, metabolism, signaling pathways, and angiogenesis-related genes; and possible strategies to normalize blood vessels through regulating tumor vessel generation, the development of tumor vessels, and blood vessel fusion and pruning.

Reactive Oxygen Species-Induced TRPM2-Mediated Ca2+ Signalling in Endothelial Cells

Endothelial cells form the innermost layer of blood vessels with a fundamental role as the physical barrier. While regulation of endothelial cell function by reactive oxygen species (ROS) is critical in physiological processes such as angiogenesis, endothelial function is a major target for interruption by oxidative stress resulting from generation of high levels of ROS in endothelial cells by various pathological factors and also release of ROS by neutrophils. TRPM2 is a ROS-sensitive Ca²⁺-permeable channel expressed in endothelial cells of various vascular beds. In this review, we provide an overview of the TRPM2 channel and its role in mediating ROS-induced Ca²⁺ signaling in endothelial cells. We discuss the TRPM2-mediated Ca²⁺ signaling in vascular endothelial growth factor-induced angiogenesis and in post-ischemic neovascularization. In particular, we examine the accumulative evidence that supports the role of TRPM2-mediated Ca²⁺ signaling in endothelial cell dysfunction caused by various oxidative stress-inducing factors that are associated with tissue inflammation, obesity and diabetes, as well as air pollution. These findings provide new, mechanistic insights into ROS-mediated regulation of endothelial cells in physiology and diseases.

Macrophage-Mediated Tissue Vascularization: Similarities and Differences Between Cornea and Skin

Macrophages are critical mediators of tissue vascularization both in health and disease. In multiple tissues, macrophages have been identified as important regulators of both blood and lymphatic vessel growth, specifically following tissue injury and in pathological inflammatory responses. In development, macrophages have also been implicated in limiting vascular growth. Hence, macrophages provide an important therapeutic target to modulate tissue vascularization in the clinic. However, the molecular mechanisms how macrophages mediate tissue vascularization are still not entirely resolved. Furthermore, mechanisms might also vary among different tissues. Here we review the role of macrophages in tissue vascularization with a focus on their role in blood and lymphatic vessel formation in the barrier tissues cornea and skin. Comparing mechanisms of macrophage-mediated hem- and lymphangiogenesis in the angiogenically privileged cornea and the physiologically vascularized skin provides an opportunity to highlight similarities but also tissue-specific differences, and to understand how macrophage-mediated hem- and lymphangiogenesis can be exploited for the treatment of disease, including corneal wound healing after injury, graft rejection after corneal transplantation or pathological vascularization of the skin.

Targeting Intercellular Communication in the Bone Microenvironment to Prevent Disseminated Tumor Cell Escape from Dormancy and Bone Metastatic Tumor Growth

Metastasis to the bone is a common feature of many cancers including those of the breast, prostate, lung, thyroid and kidney. Once tumors metastasize to the bone, they are essentially incurable. Bone metastasis is a complex process involving not only intravasation of tumor cells from the primary tumor into circulation, but extravasation from circulation into the bone where they meet an environment that is generally suppressive of their growth. The bone microenvironment can inhibit the growth of disseminated tumor cells (DTC) by inducing dormancy of the DTC directly and later on following formation of a micrometastatic tumour mass by inhibiting metastatic processes including angiogenesis, bone remodeling and immunosuppressive cell functions. In this review we will highlight some of the mechanisms mediating DTC dormancy and the complex relationships which occur between tumor cells and bone resident cells in the bone metastatic microenvironment. These inter-cellular interactions may be important targets to consider for development of novel effective therapies for the prevention or treatment of bone metastases.

Regulating the Polarization of Macrophages: A Promising Approach to Vascular Dermatosis

Macrophages, a kind of innate immune cells, derive from monocytes in circulation and play a crucial role in the innate and adaptive immunity. Under the stimulation of the signals from local microenvironment, macrophages generally tend to differentiate into two main functional phenotypes depending on their high plasticity and heterogeneity, namely, classically activated macrophage (M1) and alternatively activated macrophage (M2). This phenomenon is often called macrophage polarization. In pathological conditions, chronic persistent inflammation could induce an aberrant response of macrophage and cause a shift in their phenotypes. Moreover, this shift would result in the alteration of macrophage polarization in some vascular dermatoses; e.g., an increase in proinflammatory M1 emerges from Behcet's disease (BD), psoriasis, and systemic lupus erythematosus (SLE), whereas an enhancement in anti-inflammatory M2 appears in infantile hemangioma (IH). Individual polarized phenotypes and their complicated cytokine networks may crucially mediate in the pathological processes of some vascular diseases (vascular dermatosis in particular) by activation of T cell subsets (such as Th1, Th2, Th17, and Treg cells), deterioration of oxidative stress damage, and induction of angiogenesis, but the specific mechanism remains ambiguous. Therefore, in this review, we discuss the possible role of macrophage polarization in the pathological processes of vascular skin diseases. In addition, it is proposed that regulation of macrophage polarization may become a potential strategy for controlling these disorders.

Resistance Mechanisms to Anti-angiogenic Therapies in Cancer

Tumor growth and metastasis rely on tumor vascular network for the adequate supply of oxygen and nutrients. Tumor angiogenesis relies on a highly complex program of growth factor signaling, endothelial cell (EC) proliferation, extracellular matrix (ECM) remodeling, and stromal cell interactions. Numerous pro-angiogenic drivers have been identified, the most important of which is the vascular endothelial growth factor (VEGF). The importance of pro-angiogenic inducers in tumor growth, invasion and extravasation make them an excellent therapeutic target in several types of cancers. Hence, the number of anti-angiogenic agents developed for cancer treatment has risen over the past decade, with at least eighty drugs being investigated in preclinical studies and phase I-III clinical trials. To date, the most common approaches to the inhibition of the VEGF axis include the blockade of VEGF receptors (VEGFRs) or ligands by neutralizing antibodies, as well as the inhibition of receptor tyrosine kinase (RTK) enzymes. Despite promising preclinical results, anti-angiogenic monotherapies led only to mild clinical benefits. The minimal benefits could be secondary to primary or acquired resistance, through the activation of alternative mechanisms that sustain tumor vascularization and growth. Mechanisms of resistance are categorized into VEGF-dependent alterations, non-VEGF pathways and stromal cell interactions. Thus, complementary approaches such as the combination of these inhibitors with agents targeting alternative mechanisms of blood vessel formation are urgently needed. This review provides an updated overview on the pathophysiology of angiogenesis during tumor growth. It also sheds light on the different pro-angiogenic and anti-angiogenic agents that have been developed to date. Finally, it highlights the preclinical evidence for mechanisms of angiogenic resistance and suggests novel therapeutic approaches that might be exploited with the ultimate aim of overcoming resistance and improving clinical outcomes for patients with cancer.

Salvianolic acid B regulates macrophage polarization in ischemic/reperfused hearts by inhibiting mTORC1-induced glycolysis

Macrophages play important roles in the healing and remodeling of cardiac tissues after myocardial ischemia/reperfusion (MI/R) injury. Here we investigated the potential effects of salvianolic acid B (SalB), one of the abundant and bioactive compounds extracted from Chinese herb Salvia Miltiorrhiza (Danshen), on macrophage-mediated inflammation after MI/R and the underlying mechanisms. In primary cultured bone marrow-derived macrophages (BMDMs), SalB attenuated lipopolysaccharide (LPS)-induced M1 biomarkers (IL-6, iNOS, CCL2 and TNF-α) mRNA expression in a concentration-dependent manner. In contrast, M2 biomarkers (Arg1, Clec10a and Mrc) mRNA levels following interleukinin-4 (IL-4) stimulation were significantly upregulated by SalB. In addition, LPS stimulation potently induced transcriptional upregulation of RagD, an important activation factor of mammalian target of rapamycin complex 1 (mTORC1). Interestingly, SalB inhibited RagD upregulation and mTORC1 activation, decreased glycolysis, and reduced inflammatory cytokine production in LPS-stimulated macrophages, all of which were blunted in RagD knockdown macrophages. In mice subjected to MI/R, SalB treatment decreased cardiac M1-macrophages and increased M2-macrophages at 3 days post-MI/R, followed by decreased collagen deposition and ameliorated cardiac dysfunction at 7 days post-MI/R. Collectively, our data have shown that SalB decreases M1-polarized macrophages in MI/R hearts via inhibiting mTORC1-dependent glycolysis, which might contribute to alleviated inflammation and improved cardiac dysfunction afforded by SalB after MI/R.

Nck adapter proteins promote podosome biogenesis facilitating extracellular matrix degradation and cancer invasion

Background

Podosomes are membrane‐bound adhesive structures formed by actin remodeling. They are capable of extracellular matrix (ECM) degradation, which is a prerequisite for cancer cell invasion and metastasis. The signaling mechanism of podosome formation is still unknown in cancer. We previously reported that Nck adaptors regulate directional cell migration and endothelial lumen formation by actin remodeling, while deficiency of Nck reduces cancer metastasis. This study evaluated the role of Nck adaptors in podosome biogenesis and cancer invasion.

Methods

This study was conducted in vitro using both healthy cells (Human Umbilical Vein Endothelial Cell, 3T3 fibroblasts) and cancer cells (prostate cancer cell line; PC3, breast cancer cell line; MDA‐MB‐231). Confocal and TIRF imaging of cells expressing Green Fluorescence Protein (GFP)  mutant under altered levels of Nck or downstream of kinase 1 (Dok1) was used to evaluate the podosome formation and fluorescent gelatin matrix degradation. Levels of Nck in human breast carcinoma tissue sections were detected by immune histochemistry using Nck polyclonal antibody. Biochemical interaction of Nck/Dok1 was detected in podosome forming cells using immune precipitation and far‐western blotting.

Results

This study demonstrates that ectopic expression of Nck1 and Nck2 can induce the endothelial podosome formation in vitro. Nck silencing by short‐hairpin RNA blocked podosome biogenesis and ECM degradation in cSrc‐Y530F transformed endothelial cells in this study. Immunohistochemical analysis revealed the Nck overexpression in human breast carcinoma tissue sections. Immunoprecipitation and far‐western blotting revealed the biochemical interaction of Nck/p62Dok in podosome forming cells.

Conclusions

Nck adaptors in interaction with Dok1 induce podosome biogenesis and ECM degradation facilitating cancer cell invasion, and therefore a bona fide target of cancer therapy.

Emerging role of glycosylation in the polarization of tumor-associated macrophages

Tumors are formed by several cell types interacting in a complex environment of soluble and matrix molecules. The crosstalk between the cells and extracellular components control tumor fate. Macrophages are highly plastic and diverse immune cells that are known to be key regulators of this complex network, which is mostly because they can adjust their metabolism and reprogram their phenotype and effector function. Here, we review the studies that disclose the central role of metabolism and tumor microenvironment in shaping the phenotype and function of macrophages, highlighting the importance of the hexosamine biosynthetic pathway. We further discuss growing evidence of nutrient-sensitive protein modifications such as O-GlcNAcylation and extracellular glycosylation in the function and polarization of tumor-associated macrophages.

Recruited bone marrow derived cells, local stromal cells and IL-17 at the front line of resistance development to anti-VEGF targeted therapies

Although anti-angiogenic agents targeting VEGF have shown affordable beneficial outcomes in several human cancer types, in most pre-clinical and clinical studies, these effects are transient and followed by rapid relapse and tumor regrowth. Recently, it has been suggested that recruited bone marrow derived cells (BMDCs) to the tumor-microenvironment together with stromal cells play an important role in development of resistance to anti-VEGF therapies. Additionally, acquired resistance to anti-VEGF therapies has shown to be mediated partly through overexpression of different pro-angiogenic cytokines and growth factors including G-CSF, IL-6, IL-8, VEGF and FGF by these cells. Alongside, IL-17, a pro-inflammatory cytokine, mostly secreted by infiltrated CD4⁺ T helper cells, has shown to mediate resistance to anti-VEGF therapies, through recruiting BMDCs and modulating stromal cells activities including endothelial cells, tumor associated macrophages and cancer associated fibroblasts. Here, we examined the role of BMDCs, tumor stromal cells, IL-17 and their negotiation in development of resistance to anti-VEGF targeted therapies.

Development and translation of novel therapeutics targeting tumor-associated macrophages

Tumor-associated macrophages (TAMs) regulate an array of tumor functions and have critical roles in both the progression and the eradication of cancer. Numerous therapies targeting TAMs are under development in cancer and many have demonstrated success at the preclinical and clinical levels. Most of these therapies fall within 3 main categories: systemic depletion of TAMs, inhibition of TAM recruitment and polarization, and promoting the antitumor functions of TAMs. In this article, the rationale behind these various therapies and approaches is reviewed along with supporting preclinical and clinical data.

Surface topography and hydrophilicity regulate macrophage phenotype in milled microfluidic systems

Micromilling is an underutilized technique for fabricating microfluidic platforms that is well-suited for the diverse needs of the biologic community. This technique, however, produces culture surfaces that are considerably rougher than in commercially available culture platforms and the hydrophilicity of these surfaces can vary considerably depending on the choice of material. In this study, we evaluated the impact of surface topography and hydrophilicity in milled microfluidic devices on the cellular phenotype and function of primary human macrophages. We found that the rough culture surface within micromilled systems affected the phenotype of macrophages cultured in these devices. However, the presence, type, and magnitude of this effect was dependent on the surface hydrophilicity as well as exposure to chemical polarization signals. These findings confirm that while milled microfluidic systems are an effective platform for culture and analysis of primary macrophages, the topography and hydrophilicity of the culture surface within these systems should be considered in the planning and analysis of any macrophage experiments in which phenotype is relevant.

Cancer Inflammation and Cytokines

Chronic inflammation is a well-recognized tumor-enabling capability, which allows nascent tumors to escape immunosurveillance. A number of soluble and cellular inflammatory mediators take part in the various phases of cancer initiation and progression, giving rise to a fatal conspiracy, which is difficult to efficiently overcome. Tumor-associated macrophages (TAMs) are pivotal players of the tumor microenvironment and, because of their characteristic plasticity, can acquire a number of distinct phenotypes and contribute in different ways to the various phases of cancerogenesis. Tumor-associated neutrophils (TANs) are also emerging as important components of the tumor microenvironment, given their unexpected heterogeneity and plasticity. TAMs and TANs are both integrated in cancer-related inflammation and an ever better understanding of their functions can be useful to tailor the use of anticancer therapeutic approaches and patient follow-up.

Stromal Infiltration of Tumor-Associated Macrophages Conferring Poor Prognosis of Patients with Basal-Like Breast Carcinoma

Aims: Tumor associated macrophages (TAMs) play a critical role in the initiation and progression of breast cancer. However, their prognostic significance in the molecular subtype of basal-like breast cancer (BLBC) is poorly understood. The aim of this study was to investigate the extent and patterns of TAMs in BLBC and their associations with clinicopathological features and patient survival. Methods and Results: We evaluated TAMs in 200 cases of BLBC by immunohistochemistry using the M2 macrophage marker CD163 and the pan-macrophage marker CD68 in tumor nest and stroma, and assessed their prognostic significance. The study demonstrated that infiltration of CD163⁺ and CD68⁺ macrophages in tumor stroma was of clinical relevance in BLBC, but not those in tumor nest. Increased stromal infiltration of CD68⁺ or CD163⁺ macrophages correlated with larger tumor size, higher histological grade, higher 5-year recurrence and 5-year breast cancer mortality. Although both of CD68⁺ and CD163⁺ macrophages in tumor stroma were associated with poor recurrence-free survival (RFS) and overall survival (OS), multivariate analysis demonstrated that only CD163⁺ macrophage was an independent predictor of RFS and OS. Conclusions: Our results highlight the prognostic importance of TAMs' location in BLBC. CD163, a highly specific biomarker for M2 macrophages, is an independent prognostic marker for BLBC patients, and may serve as an indicator or potential target of macrophage-centred therapeutic strategies.

The caveolar membrane system in endothelium: From cell signaling to vascular pathology

Caveolae are 50- to 100-nm cholesterol and glycosphingolipid-rich flask-shaped invaginations commonly observed in many terminally differentiated cells. These organelles have been described in many cell types and are particularly abundant in endothelial cells, where they have been involved in the regulation of certain signaling pathways. Specific scaffolding proteins termed caveolins, along with the more recently discovered members of the cavin family, represent the major protein components during caveolae biogenesis. In addition, multiple studies aimed to investigate the expression and the regulation of these proteins significantly contributed to elucidate the role of caveolae and caveolins in endothelial cell physiology and disease. The aim of this review is to survey recent evidence of the involvement of the caveolar network in endothelial cell biology and endothelial cell dysfunction.

Peptides derived from the histidine–proline rich glycoprotein bind copper ions and exhibit anti-angiogenic properties

A peptide belonging to the histidine–proline rich glycoprotein binds copper(ii), inhibiting metal angiogenic responses in endothelial cells.

Gene expression profiles of brain endothelial cells during embryonic development at bulk and single-cell levels

The blood-brain barrier is a dynamic interface that separates the brain from the circulatory system, and it is formed by highly specialized endothelial cells. To explore the molecular mechanisms defining the unique nature of vascular development and differentiation in the brain, we generated high-resolution gene expression profiles of mouse embryonic brain endothelial cells using translating ribosome affinity purification and single-cell RNA sequencing. We compared the brain vascular translatome with the vascular translatomes of other organs and analyzed the vascular translatomes of the brain at different time points during embryonic development. Because canonical Wnt signaling is implicated in the formation of the blood-brain barrier, we also compared the brain endothelial translatome of wild-type mice with that of mice lacking the transcriptional cofactor β-catenin (Ctnnb1). Our analysis revealed extensive molecular changes during the embryonic development of the brain endothelium. We identified genes encoding brain endothelium-specific transcription factors (Foxf2, Foxl2, Foxq1, Lef1, Ppard, Zfp551, and Zic3) that are associated with maturation of the blood-brain barrier and act downstream of the Wnt-β-catenin signaling pathway. Profiling of individual brain endothelial cells revealed substantial heterogeneity in the population. Nevertheless, the high abundance of Foxf2, Foxq1, Ppard, or Zic3 transcripts correlated with the increased expression of genes encoding markers of brain endothelial cell differentiation. Expression of Foxf2 and Zic3 in human umbilical vein endothelial cells induced the production of blood-brain barrier differentiation markers. This comprehensive data set may help to improve the engineering of in vitro blood-brain barrier models.

Beyond organoids: In vitro vasculogenesis and angiogenesis using cells from mammals and zebrafish

The ability to culture complex organs is currently an important goal in biomedical research. It is possible to grow organoids (3D organ-like structures) in vitro; however, a major limitation of organoids, and other 3D culture systems, is the lack of a vascular network. Protocols developed for establishing in vitro vascular networks typically use human or rodent cells. A major technical challenge is the culture of functional (perfused) networks. In this rapidly advancing field, some microfluidic devices are now getting close to the goal of an artificially perfused vascular network. Another development is the emergence of the zebrafish as a complementary model to mammals. In this review, we discuss the culture of endothelial cells and vascular networks from mammalian cells, and examine the prospects for using zebrafish cells for this objective. We also look into the future and consider how vascular networks in vitro might be successfully perfused using microfluidic technology.

PDGFRβ Regulates Adipose Tissue Expansion and Glucose Metabolism via Vascular Remodeling in Diet-Induced Obesity

Platelet-derived growth factor (PDGF) is a key factor in angiogenesis; however, its role in adult obesity remains unclear. In order to clarify its pathophysiological role, we investigated the significance of PDGF receptor β (PDGFRβ) in adipose tissue expansion and glucose metabolism. Mature vessels in the epididymal white adipose tissue (eWAT) were tightly wrapped with pericytes in normal mice. Pericyte desorption from vessels and the subsequent proliferation of endothelial cells were markedly increased in the eWAT of diet-induced obese mice. Analyses with flow cytometry and adipose tissue cultures indicated that PDGF-B caused the detachment of pericytes from vessels in a concentration-dependent manner. M1-macrophages were a major type of cells expressing PDGF-B in obese adipose tissue. In contrast, pericyte detachment was attenuated and vascularity within eWAT was reduced in tamoxifen-inducible conditional Pdgfrb-knockout mice with decreases in adipocyte size and chronic inflammation. Furthermore, Pdgfrb-knockout mice showed enhanced energy expenditure. Consequently, diet-induced obesity and the associated deterioration of glucose metabolism in wild-type mice were absent in Pdgfrb-knockout mice. Therefore, PDGF-B-PDGFRβ signaling plays a significant role in the development of adipose tissue neovascularization and appears to be a fundamental target for the prevention of obesity and type 2 diabetes.

Effect of THP-1 Cells on the Formation of Vascular Tubes by Endothelial EA.hy926 Cells in the Presence of Placenta Secretory Products

We studied the effect of THP-1 cells on the formation of vessel-like structures by endothelial cells in the presence of placenta-conditioned media. Addition of THP-1 cells to endothelial cells cultured in the presence of media conditioned by first-trimester placentas led to an increase in the length of cell tubes and reduced their number in comparison with endothelial cell monoculture. In the presence of media conditioned by third-trimester placentas, THP-1 cells did not affect the length and number of cell tubes formed by endothelial cells. When evaluating the formation of vessel-like structures by endothelial cells in co-culture, marked decrease in the length of cell tubes in the presence of media conditioned by first-trimester placentas vs. third-trimester placentas was noted. No differences in the length and number of cell tubes formed by endothelial cells co-cultured with THP-1 cells in the presence of placental factors from women with preeclampsia and uncomplicated pregnancy were found. These findings can reflect the peculiarities of the influence of macrophages on the formation of blood vessels by endothelial cells in the placenta.

Pharmacological Modulation of Proton Channel Hv1 in Cancer Therapy: Future Perspectives

The pharmacological modulation of the immunosuppressive tumor microenvironment has emerged as a relevant component for cancer therapy. Several approaches aiming to deplete innate and adaptive suppressive populations, to circumvent the impairment in antigen presentation, and to ultimately increase the frequency of activated tumor-specific T cells are currently being explored. In this review, we address the potentiality of targeting the voltage-gated proton channel, Hv1, as a novel strategy to modulate the tumor microenvironment. The function of Hv1 in immune cells such as macrophages, neutrophils, dendritic cells, and T cells has been associated with the maintenance of NADPH oxidase activity and the generation of reactive oxygen species, which are required for the host defense against pathogens. We discuss evidence suggesting that the Hv1 proton channel could also be important for the function of these cells within the tumor microenvironment. Furthermore, as summarized here, tumor cells express Hv1 as a primary mechanism to extrude the increased amount of protons generated metabolically, thus maintaining physiologic values for the intracellular pH. Therefore, because this channel might be relevant for both tumor cells and immune cells supporting tumor growth, the pharmacological inhibition of Hv1 could be an innovative approach for cancer therapy. With that focus, we analyzed the available compounds that inhibit Hv1, highlighted the need to develop better drugs suitable for patients, and commented on the future perspectives of targeting Hv1 in the context of cancer therapy.

Hydrogen Sulfide Mitigates Myocardial Infarction via Promotion of Mitochondrial Biogenesis-Dependent M2 Polarization of Macrophages

AIMS

Macrophages are of key importance for tissue repair after myocardial infarction (MI). Hydrogen sulfide (H2S) has been shown to exert cardioprotective effects in MI. However, the mechanisms by which H2S modulates cardiac remodeling and repair post-MI remain to be clarified.

RESULTS

In our current study, we showed that H2S supplementation ameliorated pathological remodeling and dysfunction post-MI in wild-type (WT) and CSE KO mice, resulting in decreased infarct size and mortality, accompanied by an increase in the number of M2-polarized macrophages at the early stage of MI. Strikingly, adoptive transfer of NaHS-treated bone marrow-derived macrophages into WT and CSE KO mice with depleted macrophages also ameliorated MI-induced cardiac functional deterioration. Further mechanistic studies demonstrated that NaHS-induced M2 polarization was achieved by enhanced mitochondrial biogenesis and fatty acid oxidation.

INNOVATION AND CONCLUSION

Our study shows (for the first time) that H2S may have the potential as a therapeutic agent for MI via promotion of M2 macrophage polarization. Rebound Track: This work was rejected during standard peer review and rescued by Rebound Peer Review (Antioxid Redox Signal 16:293-296, 2012) with the following serving as open reviewers: Hideo Kimura, Chaoshu Tang, Xiaoli Tian, and Kenneth Olson. Antioxid. Redox Signal. 25, 268-281.

"Decoding" Angiogenesis: New Facets Controlling Endothelial Cell Behavior

Angiogenesis, the formation of new blood vessels, is a unique and crucial biological process occurring during both development and adulthood. A better understanding of the mechanisms that regulates such process is mandatory to intervene in pathophysiological conditions. Here we highlight some recent argument on new players that are critical in endothelial cells, by summarizing novel discoveries that regulate notorious vascular pathways such as Vascular Endothelial Growth Factor (VEGF), Notch and Planar Cell Polarity (PCP), and by discussing more recent findings that put metabolism, redox signaling and hemodynamic forces as novel unforeseen facets in angiogenesis. These new aspects, that critically regulate angiogenesis and vascular homeostasis in health and diseased, represent unforeseen new ground to develop anti-angiogenic therapies.

Effect of Factors Secreted by the Placenta on Phenotype of THP-1 Cells Cultured on a 3D Scaffold

We studied the effects of secretory products of the placenta obtained from women with normal pregnancy and preeclampsia on the expression of surface markers by THP-1 cells cultured on a 3D Matrigel scaffold. Secretory products of third trimester placentas obtained from women with normal pregnancy reduced the relative number of THP-1 cells expressing CD54 and CD14 molecules and expression of CD14 and CD95 molecules by THP-1 cells in comparison with the effect of secretory products first trimester placentas. In parallel, the intensity of CD49d expression by THP-1 cells increased in the presence of secretory products of third trimester placentas in comparison with the first trimester. No differences in the expression of the studied molecules by THP-1 cells under the effect of placentas from women with physiological pregnancy and patients with preeclampsia were found.

Macrophages Mediate the Repair of Brain Vascular Rupture through Direct Physical Adhesion and Mechanical Traction

Hemorrhagic stroke and brain microbleeds are caused by cerebrovascular ruptures. Fast repair of such ruptures is the most promising therapeutic approach. Due to a lack of high-resolution in vivo real-time studies, the dynamic cellular events involved in cerebrovascular repair remain unknown. Here, we have developed a cerebrovascular rupture system in zebrafish by using multi-photon laser, which generates a lesion with two endothelial ends. In vivo time-lapse imaging showed that a macrophage arrived at the lesion and extended filopodia or lamellipodia to physically adhere to both endothelial ends. This macrophage generated mechanical traction forces to pull the endothelial ends and facilitate their ligation, thus mediating the repair of the rupture. Both depolymerization of microfilaments and inhibition of phosphatidylinositide 3-kinase or Rac1 activity disrupted macrophage-endothelial adhesion and impaired cerebrovascular repair. Our study reveals a hitherto unexpected role for macrophages in mediating repair of cerebrovascular ruptures through direct physical adhesion and mechanical traction.

Host immune cellular reactions in corneal neovascularization

Corneal neovascularization (CNV) is a global important cause of visual impairment. The immune mechanisms leading to corneal heme- and lymphangiogenesis have been extensively studied over the past years as more attempts were made to develop better prophylactic and therapeutic measures. This article aims to discuss immune cells of particular relevance to CNV, with a focus on macrophages, Th17 cells, dendritic cells and the underlying immunology of common pathologies involving neovascularization of the cornea. Hopefully, a thorough understanding of these topics would propel the efforts to halt the detrimental effects of CNV.

Engineering macrophages to control the inflammatory response and angiogenesis

Macrophage (MΦ) dysregulation is increasingly becoming recognized as a risk factor for a number of inflammatory complications including atherosclerosis, cancer, and the host response elicited by biomedical devices. It is still unclear what roles the pro-inflammatory (M1) MΦ and pro-healing (M2) MΦ phenotypes play during the healing process. However, it has been shown that a local overabundance of M1 MΦs can potentially lead to a chronically inflamed state of the tissue; while a local over-exuberant M2 MΦ response can lead to tissue fibrosis and even promote tumorigenesis. These notions strengthen the argument that the tight temporal regulation of this phenotype balance is necessary to promote inflammatory resolution that leads to tissue homeostasis. In this study, we have engineered pro-inflammatory MΦs, MΦ-cTLR4 cells, which can be activated to a M1-like MΦ phenotype with a small molecule, the chemical inducer of dimerization (CID) drug. The MΦ-cTLR4 cells when activated with the CID drug, express increased levels of TNFα, IL-6, and iNOS. Activated MΦ-cTLR4 cells stay stimulated for at least 48h; once the CID drug is withdrawn, the MΦ-cTLR4 cells return to baseline state within 18h. Further, in vitro CID-activated MΦ-cTLR4 cells induce upregulation of VCAM-1 and ICAM-1 on endothelial cells (EC) in a TNFα-dependent manner. With the ability to specifically modulate the MФ-cTLR4 cells with the presence or absence of a small molecule, we now have the tool necessary to observe a primarily M1 MФ response during inflammation. By isolating this phase of the wound healing response, it may be possible to determine conditions for ideal healing.

The great escape; the hallmarks of resistance to antiangiogenic therapy

The concept of antiangiogenic therapy in cancer treatment has led to the approval of different agents, most of them targeting the well known vascular endothelial growth factor pathway. Despite promising results in preclinical studies, the efficacy of antiangiogenic therapy in the clinical setting remains limited. Recently, awareness has emerged on resistance to antiangiogenic therapies. It has become apparent that the intricate complex interplay between tumors and stromal cells, including endothelial cells and associated mural cells, allows for escape mechanisms to arise that counteract the effects of these targeted therapeutics. Here, we review and discuss known and novel mechanisms that contribute to resistance against antiangiogenic therapy and provide an outlook to possible improvements in therapeutic approaches.

Hypoxia-induced expression of phosducin-like 3 regulates expression of VEGFR-2 and promotes angiogenesis

Expression and activation of vascular endothelial growth factor receptor 2 (VEGFR-2) by VEGF ligands are the main events in the stimulation of pathological angiogenesis. VEGFR-2 expression is generally low in the healthy adult blood vessels, but its expression is markedly increased in the pathological angiogenesis. In this report, we demonstrate that phosducin-like 3 (PDCL3), a recently identified chaperone protein involved in the regulation of VEGFR-2 expression, is required for angiogenesis in zebrafish and mouse. PDCL3 undergoes N-terminal methionine acetylation, and this modification affects PDCL3 expression and its interaction with VEGFR-2. Expression of PDCL3 is regulated by hypoxia, the known stimulator of angiogenesis. The mutant PDCL3 that is unable to undergo N-terminal methionine acetylation was refractory to the effect of hypoxia. The siRNA-mediated silencing of PDCL3 decreased VEGFR-2 expression resulting in a decrease in VEGF-induced VEGFR-2 phosphorylation, whereas PDCL3 over-expression increased VEGFR-2 protein. Furthermore, we show that PDCL3 protects VEGFR-2 from misfolding and aggregation. The data provide new insights for the chaperone function of PDCL3 in angiogenesis and the roles of hypoxia and N-terminal methionine acetylation in PDCL3 expression and its effect on VEGFR-2.

Tumor-induced myeloid deviation: when myeloid-derived suppressor cells meet tumor-associated macrophages

The generation of an inflammatory environment is favorable and often decisive for the growth of both primary tumors and metastases. Tumor cells either express membrane molecules or release tumor-derived soluble factors able to alter myelopoiesis. Tumor-reprogrammed myeloid cells not only create a tolerogenic environment by blocking T cell functions and proliferation, but also directly drive tumor growth by promoting cancer stemness, angiogenesis, stroma deposition, epithelial-to-mesenchymal transition, and metastasis formation. In this Review, we discuss the interplay between immunosuppressive and protumoral myeloid cells and detail their immune-regulatory mechanisms, the molecular pathways involved in their differentiation, as well as their potential role as prognostic and diagnostic biomarkers and prospective targets for innovative approaches to treat tumor-bearing hosts.

Hemangioblastic foci in human first trimester placenta: Distribution and gestational profile

INTRODUCTION

The human placenta is a site of both hematopoiesis and vasculogenesis. There are reports of hemangioblastic foci (HAF) in the first trimester placenta, but little published information about their spatiotemporal incidence.

METHODS

We have used semi-thin sections and whole mount staining techniques on archival early pregnancy hysterectomy material as well as freshly-collected termination tissue.

RESULTS

We report a description of the distribution of HAF, their gestational profile, and some characteristics of the constituent cells. We show crypt-shaped HAF are present in villi at different levels from 4 to 11 weeks and in the chorionic plate from 4 to 9 weeks. In the villous placenta, the foci often approach closely at one end to the trophoblast basement membrane. Morphologically they show remarkable similarity to those found in the yolk sac at similar stages. In some crypts, all cells are CD34+, but CD34 and nestin progressively segregate into the endothelial lineage. Brachyury is present in less differentiated cells. The erythroid lineage is dominant, as shown by the widespread expression of CD235a/glycophorin and characteristic erythroid morphologies, indicating various degrees of differentiation. However, CD41 is also present in non-endothelial cells. Initially a discontinuous UEA-1/CD31-positive endothelium forms at the periphery of the foci. These cells appear to become integrated into the developing vasculogenic/angiogenic vessel network. We also demonstrate that, independent of HAF, vasculogenesis occurs near the tips of growing villi during the first trimester.

DISCUSSION

We suggest HAF interface with the developing vascular network, producing communication channels that allow erythrocytes to enter the placental-embryonic circulation. We speculate that the erythroid cells act as oxygen reservoirs during the period before flow of maternal blood through the intervillous space of the placenta, allowing a slow feed of oxygen-rich cells to the developing embryo.

Vascularisation of the central nervous system

The developing central nervous system (CNS) is vascularised through the angiogenic invasion of blood vessels from a perineural vascular plexus, followed by continued sprouting and remodelling until a hierarchical vascular network is formed. Remarkably, vascularisation occurs without perturbing the intricate architecture of the neurogenic niches or the emerging neural networks. We discuss the mouse hindbrain, forebrain and retina as widely used models to study developmental angiogenesis in the mammalian CNS and provide an overview of key cellular and molecular mechanisms regulating the vascularisation of these organs.

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CNS vascularisation is initiated during embryonic development.

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CNS vascularisation is studied in the mouse forebrain, hindbrain and retina models.

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Neuroglial cells interact with endothelial cells to promote angiogenesis.

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Neuroglial cells produce growth factors and matrix cues to pattern vessels.

Phagocytes as Corrupted Policemen in Cancer-Related Inflammation

Inflammation is a key component of the tumor microenvironment. Tumor-associated macrophages (TAMs) and tumor-associated neutrophils (TANs) are prototypic inflammatory cells in cancer-related inflammation. Macrophages provide a first line of resistance against infectious agents but in the ecological niche of cancer behave as corrupted policemen. TAMs promote tumor growth and metastasis by direct interactions with cancer cells, including cancer stem cells, as well as by promoting angiogenesis and tissue remodeling and suppressing effective adaptive immunity. In addition, the efficacy of chemotherapy, radiotherapy, and checkpoint blockade inhibitors is profoundly affected by regulation of TAMs. In particular, TAMs can protect and rescue tumor cells from cytotoxic therapy by orchestrating a misguided tissue repair response. Following extensive preclinical studies, there is now proof of concept that targeting tumor-promoting macrophages by diverse strategies (e.g., Trabectedin, anti-colony-stimulating factor-1 receptor antibodies) can result in antitumor activity in human cancer and further studies are ongoing. Neutrophils have long been overlooked as a minor component of the tumor microenvironment, but there is evidence for an important role of TANs in tumor progression. Targeting phagocytes (TAMs and TANs) as corrupted policemen in cancer may pave the way to innovative therapeutic strategies complementing cytoreductive therapies and immunotherapy.

Effect of Monocyte-Like THP-1 Cells on the Formation of Vascular Tubes by EA.Hy926s Endothelial Cells in the Presence of Cytokines

The interaction of endothelial cells with cells of the microenvironment, including monocytes/ macrophages, and extracellular matrix during angiogenesis is controlled by cytokines. The stimulating effect bFGF, IL-8, and VEGF on the formation of capillary-like structures by endothelial cells was demonstrated in both monoculture and in co-culture with THP-1 cells; in the latter case, the effects of bFGF and VEGF were more pronounced. IL-8 reduced branching of vascular tubes in co-culture in comparison with monoculture of endothelial cells. Placental growth factor PlGF had no effect of tube formation by endothelial cells in monoculture, but in co-culture with THP-1 cells this cytokine in high concentrations exhibited proangiogenic activity. TGFb inhibited the formation of vascular tubes by endothelial cells and its antiangiogenic potential was more pronounced in co-culture with THP-1 cells.