Differential transcriptional regulation of the two vascular endothelial growth factor receptor genes. Flt-1, but not Flk-1/KDR, is up-regulated by hypoxia

The effect of Hypoxia-Inducible Factor-1a stabilization on bone regeneration during distraction osteogenesis: A systematic review of animal studies

OBJECTIVE

This systematic review described Hypoxia-Inducible Factor-1a stabilization or upregulation approaches along with underlying signaling pathways and assessed bone regeneration, angiogenesis, and consolidation time during DO in animal models.

DESIGN

A comprehensive and systematic search of electronic databases including PubMed, Scopus, and ScienceDirect was performed till December 26, 2023. The search was limited to English articles, and no time restrictions were applied.

RESULTS

A total of 14 studies met the inclusion criteria and were included for final review. Four methods have been shown to activate the HIF pathway including genetic, pharmacological, mechanical, and cell preconditioning approaches. Deferoxamine (DFO) was administered as a pharmacological hypoxia-mimicking agent in many studies reporting acceptable outcomes on bone regeneration and acceleration of bone consolation. Applying mechanical loads at the optimal rate and amplitude serves as a minimally invasive approach with acceptable results. HIF-related signaling pathways increase osteogenesis and angiogenesis during DO, potentially through VHL/HIF-1a/VEGF, Wnt/β-catenin, and Mesenchymal-Epithelial transition (MET) signaling pathways.

CONCLUSION

Activation of HIF-related signaling pathways enhances and accelerates bone regeneration during the consolidation phase of distraction osteogenesis. The most feasible approach with the least side effects must be selected for further clinical studies.

Vascular Endothelial Growth Factor Receptors in the Vascularization of Pancreatic Tumors: Implications for Prognosis and Therapy

In pancreatic cancer (PC), vascular endothelial growth factor (VEGF) and its primary receptor, vascular endothelial growth factor receptor (VEGFR)-2, are central drivers of angiogenesis and metastasis, with their overexpression strongly associated with poor prognosis. In some PC patients, VEGF levels correlate with disease stage, tumor burden, and survival outcomes. However, therapies targeting VEGF and VEGFR-2, including tyrosine kinase inhibitors (TKIs) and monoclonal antibodies, have demonstrated limited efficacy, partly due to the emergence of resistance mechanisms. Resistance appears to stem from the activation of alternative vascularization pathways. This review explores the multifaceted roles of VEGFRs in pancreatic cancer, including VEGFR-1 and VEGFR-3. Potential strategies to improve VEGFR-targeting therapies, such as combination treatments, the development of more selective inhibitors, and the use of biomarkers, are discussed as promising approaches to enhance treatment efficacy and outcomes.

The effects of young and aged, male and female megakaryocyte conditioned media on angiogenic properties of endothelial cells

With aging, the risk of fractures and compromised healing increases. Angiogenesis plays a significant role in bone healing and is impaired with aging. We have previously shown the impact of megakaryocytes (MKs) in regulating bone healing. Notably, MKs produce factors known to promote angiogenesis. We examined the effects of conditioned media (CM) generated from MKs derived from young (3-4-month-old) and aged (22-24-month-old), male and female C57BL/6J mice on bone marrow endothelial cell (BMEC) growth and function. Female MK CM, regardless of age, caused a >65% increase in BMEC proliferation and improved vessel formation by >115%. Likewise, young male MK CM increased vessel formation by 160%. Although aged male MK CM resulted in >150% increases in the formation of vascular nodes and meshes, 62% fewer vessels formed compared to young male MK CM treatment. Aged female MK CM improved migration by over 2500%. However, aged female and male MK CM caused less wound closure. MK CM treatments also significantly altered the expression of several genes including PDGFRβ, CXCR4, and CD36 relative to controls and between ages. Further testing of mechanisms responsible for age-associated differences may allow for novel strategies to improve MK-mediated angiogenesis and bone healing, particularly within the aging population.

Protective and Regenerative Effects of Reconstituted HDL on Human Rotator Cuff Fibroblasts under Hypoxia: An In Vitro Study

Hypoxia and hypo-high-density lipoproteinemia (hypo-HDLemia) are proposed risk factors for rotator cuff tear. HDL is recognized for its potential benefits in ischemia-driven angiogenesis and wound healing. Nevertheless, research on the potential benefits of reconstituted HDL (rHDL) on human rotator cuff fibroblasts (RCFs) under hypoxia is limited. This study investigates the cytoprotective and regenerative effects of rHDL, as well as N-acetylcysteine (NAC), vitamin C (Vit C), and HDL on human RCFs under hypoxic conditions. Sixth-passage human RCFs were divided into normoxia, hypoxia, and hypoxia groups pretreated with antioxidants (NAC, Vit C, rHDL, HDL). Hypoxia was induced by 1000 µM CoCl2. In the hypoxia group compared to the normoxia group, there were significant increases in hypoxia-inducible factor-1α (HIF-1α), heme oxygenase-1 (HO-1), and Bcl-2/E1B-19kDa interacting protein 3 (BNIP3) expressions, along with reduced cell viability, elevated reactive oxygen species (ROS) production, apoptosis rate, expressions of cleaved caspase-3, cleaved poly ADP-ribose polymerase-1 (PARP-1), vascular endothelial growth factors (VEGF), and matrix metalloproteinase-2 (MMP-2), as well as decreased collagen I and III production, and markedly lower cell proliferative activity (p ≤ 0.039). These responses were significantly mitigated by pretreatment with rHDL (p ≤ 0.046). This study suggests that rHDL can enhance cell proliferation and collagen I and III production while reducing apoptosis in human RCFs under hypoxic conditions.

A defined clathrin-mediated trafficking pathway regulates sFLT1/VEGFR1 secretion from endothelial cells

FLT1/VEGFR1 negatively regulates VEGF-A signaling and is required for proper vessel morphogenesis during vascular development and vessel homeostasis. Although a soluble isoform, sFLT1, is often mis-regulated in disease and aging, how sFLT1 is trafficked and secreted from endothelial cells is not well understood. Here we define requirements for constitutive sFLT1 trafficking and secretion in endothelial cells from the Golgi to the plasma membrane, and we show that sFLT1 secretion requires clathrin at or near the Golgi. Perturbations that affect sFLT1 trafficking blunted endothelial cell secretion and promoted intracellular mis-localization in cells and zebrafish embryos. siRNA-mediated depletion of specific trafficking components revealed requirements for RAB27A, VAMP3, and STX3 for post-Golgi vesicle trafficking and sFLT1 secretion, while STX6, ARF1, and AP1 were required at the Golgi. Live-imaging of temporally controlled sFLT1 release from the endoplasmic reticulum showed clathrin-dependent sFLT1 trafficking at the Golgi into secretory vesicles that then trafficked to the plasma membrane. Depletion of STX6 altered vessel sprouting in 3D, suggesting that endothelial cell sFLT1 secretion influences proper vessel sprouting. Thus, specific trafficking components provide a secretory path from the Golgi to the plasma membrane for sFLT1 in endothelial cells that utilizes a specialized clathrin-dependent intermediate, suggesting novel therapeutic targets.

Diabetes and the Microvasculature of the Bone and Marrow

PURPOSE OF REVIEW

The purpose of this review is to highlight the evidence of microvascular dysfunction in bone and marrow and its relation to poor skeletal outcomes in diabetes mellitus.

RECENT FINDINGS

Diabetes mellitus is characterized by chronic hyperglycemia, which may lead to microangiopathy and macroangiopathy. Micro- and macroangiopathy have been diagnosed in Type 1 and Type 2 diabetes, coinciding with osteopenia, osteoporosis, enhanced fracture risk and delayed fracture healing. Microangiopathy has been reported in the skeleton, correlating with reduced blood flow and perfusion, vasomotor dysfunction, microvascular rarefaction, reduced angiogenic capabilities, and augmented vascular permeability. Microangiopathy within the skeleton may be detrimental to bone and manifest as, among other clinical abnormalities, reduced mass, enhanced fracture risk, and delayed fracture healing. More investigations are required to elucidate the various mechanisms by which diabetic microvascular dysfunction impacts the skeleton.

Expression and localization of vascular endothelial growth factor and its receptors in the pig uterus during peri-implantation and determination of the in vitro effect of the angiogenesis inhibitor SU5416 on VEGF system expression

The aim of this work was to determine endometrial mRNA expression and uterine protein localization of vascular endothelial growth factor (VEGF) and its receptors VEGFR1 and VEGFR2 during the estrous cycle and peri-implantation period in sows. Uterine tissues were collected from pregnant sows on days 12, 14, 16, and 18 after artificial insemination and from non-pregnant animals on days 2 and 12 of the estrous cycle (day 0 = day of estrus). Using immunohistochemistry, a positive signal for VEGF and its receptor VEGFR2 was found in uterine luminal epithelial cells, endometrial glands, stroma, blood vessels, and myometrium. A VEGFR1 signal was only found in endometrial and myometrial blood vessels and stroma. By day 18 of gestation, the mRNA expression levels of VEGF, VEGFR1, and VEGFR2 were higher than those observed on days 2 and 12 of the estrous cycle and on days 12, 14, and 16 of gestation. Then, a primary culture of sow endometrial epithelial cells was established to define the potential of the selective inhibition of VEGFR2 after treatment with inhibitor SU5416 and determine its effects on the expression pattern of the VEGF system. The endometrial epithelial cells treated with SU5416 showed a dose-dependent decrease in VEGFR1 and VEGFR2 mRNA expression. The present study provides additional evidence on the importance of the VEGF system during peri-implantation, as well as on the specific inhibitory activity of SU5416 in epithelial cells, which, as demonstrated, express the protein and mRNA of VEGF and its receptors VEGFR1 and VEGFR2.

Adipose-Derived Stem Cells Improve Angiogenesis and Lymphangiogenesis in a Hypoxic Dermal Regeneration Model In Vitro

Background and Objectives: Impaired wound healing represents an unsolved medical issue with a high impact on patients’ quality of life and global health care. Even though hypoxia is a significant limiting factor for wound healing, it reveals stimulating effects in gene and protein expression at cellular levels. In particular, hypoxically treated human adipose tissue-derived stem cells (ASCs) have previously been used to stimulate tissue regeneration. Therefore, we hypothesized that they could promote lymphangiogenesis or angiogenesis. Materials and Methods: Dermal regeneration matrices were seeded with human umbilical vein endothelial cells (HUVECs) or human dermal lymphatic endothelial cells (LECs) that were merged with ASCs. Cultures were maintained for 24 h and 7 days under normoxic or hypoxic conditions. Finally, gene and protein expression were measured regarding subtypes of VEGF, corresponding receptors, and intracellular signaling pathways, especially hypoxia-inducible factor-mediated pathways using multiplex-RT-qPCR and ELISA assays. Results: All cell types reacted to hypoxia with an alteration of gene expression. In particular, vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor B (VEGFB), vascular endothelial growth factor C (VEGFC), vascular endothelial growth factor receptor 1 (VEGFR1/FLT1), vascular endothelial growth factor receptor 2 (VEGFR2/KDR), vascular endothelial growth factor receptor 3 (VEGFR3/FLT4), and prospero homeobox 1 (PROX1) were overexpressed significantly depending on upregulation of hypoxia-inducible factor 1 alpha (HIF-1a). Moreover, co-cultures with ASCs showed a more intense change in gene and protein expression profiles and gained enhanced angiogenic and lymphangiogenic potential. In particular, long-term hypoxia led to continuous stimulation of HUVECs by ASCs. Conclusions: Our findings demonstrated the benefit of hypoxic conditioned ASCs in dermal regeneration concerning angiogenesis and lymphangiogenesis. Even a short hypoxic treatment of 24 h led to the stimulation of LECs and HUVECs in an ASC-co-culture. Long-term hypoxia showed a continuous influence on gene expressions. Therefore, this work emphasizes the supporting effects of hypoxia-conditioned-ASC-loaded collagen scaffolds on wound healing in dermal regeneration.

The vascular endothelial growth factor (VEGF) system as a key regulator of ovarian follicle angiogenesis and growth

The vascular endothelial growth factor-A (VEGFA) system is a complex set of proteins, with multiple isoforms and receptors, including both angiogenic (VEGFxxx, VEGFR2) and antiangiogenic members (VEGFxxxb, VEGFR1 and soluble forms of VEGFR). The members of the VEGF system affect the proliferation, survival, and migration of endothelial and nonendothelial cells and are involved in the regulation of follicular angiogenesis and development. The production of VEGF by secondary follicles stimulates preantral follicular development by directly affecting follicular cells and promoting the acquisition of the follicular vasculature and downstream antrum formation. Additionally, the pattern of expression of the components of the VEGF system may provide a proangiogenic milieu capable of triggering angiogenesis and stimulating follicular cells to promote antral follicle growth, whereas, during atresia, this milieu becomes antiangiogenic and blocks follicular development.

Comparative transcriptomic analysis and genome-wide characterization of the Semaphorin family reveal the potential mechanism of angiogenesis around embryo in ovoviviparous black rockfish (Sebastes schlegelii)

To guarantee the quality and survival rate of their offspring, ovoviviparous teleost evolved special characteristics of in vivo fertilization and embryo development. Maternal black rockfish, having over 50 thousand embryos developing within the ovary simultaneously, provided around 40% nutrition throughout oocyte development, while the capillaries around each embryo contributed the rest 60% during pregnancy. Since fertilization, capillaries started to proliferate and developed into a placenta-like structure that covered over half of each embryo. Aimed to characterize the potential mechanism behind, comparative transcriptome analysis of samples collected according to the process of pregnancy. Three important time point in the process, including mature oocyte stage, fertilization and sarcomere period, were chosen for the transcriptome sequencing. Our study identified key pathways and genes involved in the cell cycle as well as DNA replication and repair, cell migration and adhesion, immune, and metabolic functions. Notably, several of the semaphoring gene family members were differently expressed. To confirm the accuracy of these genes, total of 32 sema genes were identified from the whole genome and distinct expression pattern of sema genes was observed in different pregnant stages. Our results revealed a novel insight for further investigating the functions of sema genes in reproduction physiology and embryo processes in ovoviviparous teleost.

Hyperoxia Disrupts Lung Lymphatic Homeostasis in Neonatal Mice

Inflammation causes bronchopulmonary dysplasia (BPD), a common lung disease of preterm infants. One reason this disease lacks specific therapies is the paucity of information on the mechanisms regulating inflammation in developing lungs. We address this gap by characterizing the lymphatic phenotype in an experimental BPD model because lymphatics are major regulators of immune homeostasis. We hypothesized that hyperoxia (HO), a major risk factor for experimental and human BPD, disrupts lymphatic endothelial homeostasis using neonatal mice and human dermal lymphatic endothelial cells (HDLECs). Exposure to 70% O2 for 24-72 h decreased the expression of prospero homeobox 1 (Prox1) and vascular endothelial growth factor c (Vegf-c) and increased the expression of heme oxygenase 1 and NAD(P)H dehydrogenase [quinone]1 in HDLECs, and reduced their tubule formation ability. Next, we determined Prox1 and Vegf-c mRNA levels on postnatal days (P) 7 and 14 in neonatal murine lungs. The mRNA levels of these genes increased from P7 to P14, and 70% O2 exposure for 14 d (HO) attenuated this physiological increase in pro-lymphatic factors. Further, HO exposure decreased VEGFR3+ and podoplanin+ lymphatic vessel density and lymphatic function in neonatal murine lungs. Collectively, our results validate the hypothesis that HO disrupts lymphatic endothelial homeostasis.

A defined clathrin-mediated trafficking pathway regulates sFLT1/VEGFR1 secretion from endothelial cells

FLT1/VEGFR1 negatively regulates VEGF-A signaling and is required for proper vessel morphogenesis during vascular development and vessel homeostasis. Although a soluble isoform, sFLT1, is often mis-regulated in disease and aging, how sFLT1 is trafficked and secreted from endothelial cells is not well understood. Here we define requirements for constitutive sFLT1 trafficking and secretion in endothelial cells from the Golgi to the plasma membrane, and we show that sFLT1 secretion requires clathrin at or near the Golgi. Perturbations that affect sFLT1 trafficking blunted endothelial cell secretion and promoted intracellular mis-localization in cells and zebrafish embryos. siRNA-mediated depletion of specific trafficking components revealed requirements for RAB27A, VAMP3, and STX3 for post-Golgi vesicle trafficking and sFLT1 secretion, while STX6, ARF1, and AP1 were required at the Golgi. Depletion of STX6 altered vessel sprouting in a 3D angiogenesis model, indicating that endothelial cell sFLT1 secretion is important for proper vessel sprouting. Thus, specific trafficking components provide a secretory path from the Golgi to the plasma membrane for sFLT1 in endothelial cells that utilizes a specialized clathrin-dependent intermediate, suggesting novel therapeutic targets.

Molecular Mechanisms and Future Implications of VEGF/VEGFR in Cancer Therapy

Angiogenesis, the sprouting of new blood vessels from existing vessels, is one of six known mechanisms employed by solid tumors to recruit blood vessels necessary for their initiation, growth, and metastatic spread. The vascular network within the tumor facilitates the transport of nutrients, oxygen, and immune cells and is regulated by pro- and anti-angiogenic factors. Nearly four decades ago, VEGF was identified as a critical factor promoting vascular permeability and angiogenesis, followed by identification of VEGF family ligands and their receptors (VEGFR). Since then, over a dozen drugs targeting the VEGF/VEGFR pathway have been approved for approximately 20 solid tumor types, usually in combination with other therapies. Initially designed to starve tumors, these agents transiently "normalize" tumor vessels in preclinical and clinical studies, and in the clinic, increased tumor blood perfusion or oxygenation in response to these agents is associated with improved outcomes. Nevertheless, the survival benefit has been modest in most tumor types, and there are currently no biomarkers in routine clinical use for identifying which patients are most likely to benefit from treatment. However, the ability of these agents to reprogram the immunosuppressive tumor microenvironment into an immunostimulatory milieu has rekindled interest and has led to the FDA approval of seven different combinations of VEGF/VEGFR pathway inhibitors with immune checkpoint blockers for many solid tumors in the past 3 years. In this review, we discuss our understanding of the mechanisms of response and resistance to blocking VEGF/VEGFR, and potential strategies to develop more effective therapeutic approaches.

The VEGF/VEGFR Axis Revisited: Implications for Cancer Therapy

The vascular endothelial growth factor (VEGF)/vascular endothelial growth factor receptor (VEGFR) axis is indispensable in the process of angiogenesis and has been implicated as a key driver of tumor vascularization. Consequently, several strategies that target VEGF and its cognate receptors, VEGFR-1 and VEGFR-2, have been designed to treat cancer. While therapies targeting full-length VEGF have resulted in an improvement in both overall survival and progression-free survival in various cancers, these benefits have been modest. In addition, the inhibition of VEGFRs is associated with undesirable off-target effects. Moreover, VEGF splice variants that modulate sprouting and non-sprouting angiogenesis have been identified in recent years. Cues within the tumor microenvironment determine the expression patterns of these variants. Noteworthy is that the mechanisms of action of these variants challenge the established norm of VEGF signaling. Furthermore, the aberrant expression of some of these variants has been observed in several cancers. Herein, developments in the understanding of the VEGF/VEGFR axis and the splice products of these molecules, as well as the environmental cues that regulate these variants are reviewed. Furthermore, strategies that incorporate the targeting of VEGF variants to enhance the effectiveness of antiangiogenic therapies in the clinical setting are discussed.

Hypoxia-Inducible Factor-1: A Novel Therapeutic Target for the Management of Cancer, Drug Resistance, and Cancer-Related Pain

Hypoxia-inducible factor-1 (HIF-1) is a key transcription factor that regulates the transcription of many genes that are responsible for the adaptation and survival of tumor cells in hypoxic environments. Over the past few decades, tremendous efforts have been made to comprehensively understand the role of HIF-1 in tumor progression. Based on the pivotal roles of HIF-1 in tumor biology, many HIF-1 inhibitors interrupting expression, stabilization, DNA binding properties, or transcriptional activity have been identified as potential therapeutic agents for various cancers, yet none of these inhibitors have yet been successfully translated into clinically available cancer treatments. In this review, we briefly introduce the regulation of the HIF-1 pathway and summarize its roles in tumor cell proliferation, angiogenesis, and metastasis. In addition, we explore the implications of HIF-1 in the development of drug resistance and cancer-related pain: the most commonly encountered obstacles during conventional anticancer therapies. Finally, the current status of HIF-1 inhibitors in clinical trials and their perspectives are highlighted, along with their modes of action. This review provides new insights into novel anticancer drug development targeting HIF-1. HIF-1 inhibitors may be promising combinational therapeutic interventions to improve the efficacy of current cancer treatments and reduce drug resistance and cancer-related pain.

Retinal and Choroidal Neovascularization Antivascular Endothelial Growth Factor Treatments: The Role of Gene Therapy

Neovascularization in ocular vessels causes a major disease burden. The most common causes of choroidal neovascularization (CNV) are age-related macular degeneration and diabetic retinopathy, which are the leading causes of irreversible vision loss in the adult population. Vascular endothelial growth factor (VEGF) is critical for the formation of new vessels and is the main regulator in ocular angiogenesis and vascular permeability through its receptors. Laser therapy and antiangiogenic factors have been used for CNV treatment. Bevacizumab, ranibizumab, and aflibercept are commonly used anti-VEGF agents; however, high costs and the need for frequent intraocular injections are major drawbacks of anti-VEGF drugs. Gene therapy, given the potency of one-time treatment and no need for frequent injections offers the real possibility of such a lasting treatment, with fewer adverse effects and higher patient quality of life. Herein, we reviewed the role of gene therapy in the CNV treatment. In addition, we discuss the advantages and challenges of current treatments compared with gene therapy.

NK Cells Under Hypoxia: The Two Faces of Vascularization in Tumor and Pregnancy

Environmental conditions greatly shape the phenotype and function of immune cells. Specifically, hypoxic conditions that exist within tissues and organs have been reported to affect both the adaptive and the innate immune system. Natural killer (NK) cells belong to the innate immune system. They are among the first immune cells responding to infections and are involved in tumor surveillance. NK cells produce cytokines that shape other innate and adaptive immune cells, and they produce cytolytic molecules leading to target cell killing. Therefore, they are not only involved in steady state tissue homeostasis, but also in pathogen and tumor clearance. Hence, understanding the role of NK cells in pathological and physiological immune biology is an emerging field. To date, it remains incompletely understood how the tissue microenvironment shapes NK cell phenotype and function. In particular, the impact of low oxygen concentrations in tissues on NK cell reactivity has not been systematically dissected. Here, we present a comprehensive review focusing on two highly compelling hypoxic tissue environments, the tumor microenvironment (pathological) and the decidua (physiological) and compare their impact on NK cell reactivity.

Chrysin promotes angiogenesis in rat hindlimb ischemia: Impact on PI3K/Akt/mTOR signaling pathway and autophagy

Limb ischemia occurs due to obstruction of blood perfusion to lower limbs, a manifestation that is associated with peripheral artery disease (PAD). Angiogenesis is important for adequate oxygen delivery. The present study investigated a potential role for chrysin, a naturally occurring flavonoid, in promoting angiogenesis in hindlimb ischemia (HLI) rat model. Rats were allocated into four groups: (1) sham-operated control, (2) HLI: subjected to unilateral femoral artery ligation, (3) HLI + chrysin: received 100 mg/kg, i.p. chrysin immediately after HLI, and (4) HLI + chrysin + rapamycin: received 6 mg/kg/day rapamycin i.p. for 5 days then subjected to HLI and dosed with 100 mg/kg chrysin, i.p. Rats were killed 18 h later and gastrocnemius muscles were collected and divided into parts for (1) immunohistochemistry detection of CD31 and CD105, (2) qRT-PCR analysis of eNOS and VEGFR2, (3) colorimetric analysis of NO, (4) ELISA estimation of TGF-β, VEGF, ATG5 and Beclin-1, and (5) Western blot analysis of p-PI3K, PI3K, p-Akt, Akt, p-mTOR, mTOR, and HIF-1α. Chrysin significantly enhanced microvessels growth in HLI muscles as indicated by increased CD31 and CD105 levels and decreased TGF-β. Chrysin's proangiogenic effect is potentially mediated by increased VEGF, VEGFR2 and activation of PI3K/AKT/mTOR pathway, which promoted eNOS and NO levels as it was reversed by the mTOR inhibitor, rapamycin. Chrysin also inhibited autophagy as it decreased ATG5 and Beclin-1. The current study shows that chrysin possesses a proangiogenic effect in HLI rats and might be useful in patients with PAD.

Mitochondrial Dysfunction in the Pathogenesis of Preeclampsia

PURPOSE OF REVIEW

Preeclampsia complicates 5-10% of all pregnancies and is a leading cause of maternal and perinatal mortality and morbidity. The placenta plays a pivotal role in determining pregnancy outcome by supplying the fetus with oxygen and nutrients and by synthesizing hormones. Placental function is highly dependent on energy supplied by mitochondria. It is well-known that preeclampsia is originated from placental dysfunction, although the etiology of it remains elusive.

RECENT FINDINGS

During the last three decades, substantial evidence suggests that mitochondrial abnormality is a major contributor to placental dysfunction. In addition, mitochondrial damage caused by circulating bioactive factors released from the placenta may cause endothelial dysfunction and subsequent elevation in maternal blood pressure. In this review, we summarize the current knowledge of mitochondrial abnormality in the pathogenesis of preeclampsia and discuss therapeutic approaches targeting mitochondria for treatment of preeclampsia.

Biomaterials-Based Regenerative Strategies for Skin Tissue Wound Healing

Skin tissue wound healing proceeds through four major stages, including hematoma formation, inflammation, and neo-tissue formation, and culminates with tissue remodeling. These four steps significantly overlap with each other and are aided by various factors such as cells, cytokines (both anti- and pro-inflammatory), and growth factors that aid in the neo-tissue formation. In all these stages, advanced biomaterials provide several functional advantages, such as removing wound exudates, providing cover, transporting oxygen to the wound site, and preventing infection from microbes. In addition, advanced biomaterials serve as vehicles to carry proteins/drug molecules/growth factors and/or antimicrobial agents to the target wound site. In this review, we report recent advancements in biomaterials-based regenerative strategies that augment the skin tissue wound healing process. In conjunction with other medical sciences, designing nanoengineered biomaterials is gaining significant attention for providing numerous functionalities to trigger wound repair. In this regard, we highlight the advent of nanomaterial-based constructs for wound healing, especially those that are being evaluated in clinical settings. Herein, we also emphasize the competence and versatility of the three-dimensional (3D) bioprinting technique for advanced wound management. Finally, we discuss the challenges and clinical perspective of various biomaterial-based wound dressings, along with prospective future directions. With regenerative strategies that utilize a cocktail of cell sources, antimicrobial agents, drugs, and/or growth factors, it is expected that significant patient-specific strategies will be developed in the near future, resulting in complete wound healing with no scar tissue formation.

Advances in Immunomodulation and Immune Engineering Approaches to Improve Healing of Extremity Wounds

Delayed healing of traumatic wounds often stems from a dysregulated immune response initiated or exacerbated by existing comorbidities, multiple tissue injury or wound contamination. Over decades, approaches towards alleviating wound inflammation have been centered on interventions capable of a collective dampening of various inflammatory factors and/or cells. However, a progressive understanding of immune physiology has rendered deeper knowledge on the dynamic interplay of secreted factors and effector cells following an acute injury. There is a wide body of literature, both in vitro and in vivo, abstracted on the immunomodulatory approaches to control inflammation. Recently, targeted modulation of the immune response via biotechnological approaches and biomaterials has gained attention as a means to restore the pro-healing phenotype and promote tissue regeneration. In order to fully realize the potential of these approaches in traumatic wounds, a critical and nuanced understanding of the relationships between immune dysregulation and healing outcomes is needed. This review provides an insight on paradigm shift towards interventional approaches to control exacerbated immune response following a traumatic injury from an agonistic to a targeted path. We address such a need by (1) providing a targeted discussion of the wound healing processes to assist in the identification of novel therapeutic targets and (2) highlighting emerging technologies and interventions that utilize an immunoengineering-based approach. In addition, we have underscored the importance of immune engineering as an emerging tool to provide precision medicine as an option to modulate acute immune response following a traumatic injury. Finally, an overview is provided on how an intervention can follow through a successful clinical application and regulatory pathway following laboratory and animal model evaluation.

The Role of Angiogenesis and Arteriogenesisin Myocardial Infarction and Coronary Revascularization

Surgical myocardial revascularization is associated with long-term survival benefit in patients with multivessel coronary artery disease. However, the exact biological mechanisms underlying the clinical benefits of myocardial revascularization have not been elucidated yet. Angiogenesis and arteriogenesis biologically leading to vascular collateralization are considered one of the endogenous mechanisms to preserve myocardial viability during ischemia, and the presence of coronary collateralization has been regarded as one of the predictors of long-term survival in patients with coronary artery disease (CAD). Some experimental studies and indirect clinical evidence on chronic CAD confirmed an angiogenetic response induced by myocardial revascularization and suggested that revascularization procedures could constitute an angiogenetic trigger per se. In this review, the clinical and basic science evidence regarding arteriogenesis and angiogenesis in both CAD and coronary revascularization is analyzed with the aim to better elucidate their significance in the clinical arena and potential therapeutic use.

Pre-Conditioning with IFN-γ and Hypoxia Enhances the Angiogenic Potential of iPSC-Derived MSC Secretome

Induced pluripotent stem cell (iPSC) derived mesenchymal stem cells (iMSCs) represent a promising source of progenitor cells for approaches in the field of bone regeneration. Bone formation is a multi-step process in which osteogenesis and angiogenesis are both involved. Many reports show that the secretome of mesenchymal stromal stem cells (MSCs) influences the microenvironment upon injury, promoting cytoprotection, angiogenesis, and tissue repair of the damaged area. However, the effects of iPSC-derived MSCs secretome on angiogenesis have seldom been investigated. In the present study, the angiogenic properties of IFN-γ pre-conditioned iMSC secretomes were analyzed. We detected a higher expression of the pro-angiogenic genes and proteins of iMSCs and their secretome under IFN-γ and hypoxic stimulation (IFN-H). Tube formation and wound healing assays revealed a higher angiogenic potential of HUVECs in the presence of IFN-γ conditioned iMSC secretome. Sprouting assays demonstrated that within Coll/HA scaffolds, HUVECs spheroids formed significantly more and longer sprouts in the presence of IFN-γ conditioned iMSC secretome. Through gene expression analyses, pro-angiogenic genes (FLT-1, KDR, MET, TIMP-1, HIF-1α, IL-8, and VCAM-1) in HUVECs showed a significant up-regulation and down-regulation of two anti-angiogenic genes (TIMP-4 and IGFBP-1) compared to the data obtained in the other groups. Our results demonstrate that the iMSC secretome, pre-conditioned under inflammatory and hypoxic conditions, induced the highest angiogenic properties of HUVECs. We conclude that pre-activated iMSCs enhance their efficacy and represent a suitable cell source for collagen/hydroxyapatite with angiogenic properties.

Hypoxia and chronic kidney disease

Hypoxia is an inherent pathophysiological characteristic of chronic kidney disease (CKD), which is closely associated with the development of renal inflammation and fibrosis, as well as CKD-related complications such as anaemia, cardiovascular events, and sarcopenia. This review outlined the characteristics of oxygen supply in the kidney, changes in oxygen metabolism and factors leading to hypoxia in CKD. Mechanistically, we discussed how hypoxia contributes to renal injury as well as complications associated with CKD. Furthermore, we also discussed the potential therapeutic approaches that target chronic hypoxia, as well as the challenges in the study of oxygen homeostasis imbalance in CKD.

An integrated model of preeclampsia: a multifaceted syndrome of the maternal cardiovascular-placental-fetal array

Maternal tolerance of the semiallogenic fetus necessitates conciliation of competing interests. Viviparity evolved with a placenta to mediate the needs of the fetus and maternal adaptation to the demands of pregnancy and to ensure optimal survival for both entities. The maternal-fetal interface is imagined as a 2-dimensional porous barrier between the mother and fetus, when in fact it is an intricate multidimensional array of tissues and resident and circulating factors at play, encompassing the developing fetus, the growing placenta, the changing decidua, and the dynamic maternal cardiovascular system. Pregnancy triggers dramatic changes to maternal hemodynamics to meet the growing demands of the developing fetus. Nearly a century of extensive research into the development and function of the placenta has revealed the role of placental dysfunction in the great obstetrical syndromes, among them preeclampsia. Recently, a debate has arisen questioning the primacy of the placenta in the etiology of preeclampsia, asserting that the maternal cardiovascular system is the instigator of the disorder. It was the clinical observation of the high rate of preeclampsia in hydatidiform mole that initiated the focus on the placenta in the etiology of the disease. Over many years of research, shallow trophoblast invasion with deficient remodeling of the maternal spiral arteries into vessels of higher capacitance and lower resistance has been recognized as hallmarks of the preeclamptic milieu. The lack of the normal decrease in uterine artery resistance is likewise predictive of preeclampsia. In abdominal pregnancies, however, an extrauterine pregnancy develops without remodeling of the spiral arteries, yet there is reduced resistance in the uterine arteries and distant vessels, such as the maternal ophthalmic arteries. Proponents of the maternal cardiovascular model of preeclampsia point to the observed maternal hemodynamic adaptations to pregnancy and maladaptation in gestational hypertension and preeclampsia and how the latter resembles the changes associated with cardiac disease states. Recognition of the importance of the angiogenic-antiangiogenic balance between placental-derived growth factor and its receptor soluble fms-like tyrosine kinase-1 and disturbance in this balance by an excess of a circulating isoform, soluble fms-like tyrosine kinase-1, which competes for and disrupts the proangiogenic receptor binding of the vascular endothelial growth factor and placental-derived growth factor, opened new avenues of research into the pathways to normal adaptation of the maternal cardiovascular and other systems to pregnancy and maladaptation in preeclampsia. The significance of the "placenta vs heart" debate goes beyond the academic: understanding the mutuality of placental and maternal cardiac etiologies of preeclampsia has far-reaching clinical implications for designing prevention strategies, such as aspirin therapy, prediction and surveillance through maternal hemodynamic studies or serum placental-derived growth factor and soluble fms-like tyrosine kinase-1 testing, and possible treatments to attenuate the effects of insipient preeclampsia on women and their fetuses, such as RNAi therapy to counteract excess soluble fms-like tyrosine kinase-1 produced by the placenta. In this review, we will present an integrated model of the maternal-placental-fetal array that delineates the commensality among the constituent parts, showing how a disruption in any component or nexus may lead to the multifaceted syndrome of preeclampsia.

Effects of diet, BMP-2 treatment, and femoral skeletal injury on endothelial cells derived from the ipsilateral and contralateral limbs

Type 2 diabetes (T2D) results in physiological and structural changes in bone, contributing to poor fracture healing. T2D compromises microvascular performance, which can negatively impact bone regeneration as angiogenesis is required for new bone formation. We examined the effects of bone morphogenetic protein-2 (BMP-2) administered locally at the time of femoral segmental bone defect (SBD) surgery, and its angiogenic impacts on endothelial cells (ECs) isolated from the ipsilateral or contralateral tibia in T2D mice. Male C57BL/6 mice were fed either a low-fat diet (LFD) or high-fat diet (HFD) starting at 8 weeks. After 12 weeks, the T2D phenotype in HFD mice was confirmed via glucose and insulin tolerance testing and echoMRI, and all mice underwent SBD surgery. Mice were treated with BMP-2 (5 µg) or saline at the time of surgery. Three weeks postsurgery, bone marrow ECs were isolated from ipsilateral and contralateral tibias, and proliferation, angiogenic potential, and gene expression of the cells was analyzed. BMP-2 treatment increased EC proliferation by two fold compared with saline in LFD contralateral tibia ECs, but no changes were seen in surgical tibia EC proliferation. BMP-2 treatment enhanced vessel-like structure formation in HFD mice whereas, the opposite was observed in LFD mice. Still, in BMP-2 treated LFD mice, ipsilateral tibia ECs increased expression of CD31, FLT-1, ANGPT1, and ANGPT2. These data suggest that the modulating effects of T2D and BMP-2 on the microenvironment of bone marrow ECs may differentially influence angiogenic properties at the fractured limb versus the contralateral limb.

Retinopathy of prematurity shows alterations in Vegfa164 isoform expression

BACKGROUND

Pathologic ocular neovascularization in retinopathy of prematurity (ROP) and other proliferative retinopathies are characterized by dysregulation of vascular endothelial growth factor-A (VEGF-A). A study of Vegfa isoform expression during oxygen-induced ischemic retinopathy (OIR) may enhance our understanding of Vegf dysregulation.

METHODS

Following induction of OIR, immunohistochemistry and polymerase chain reaction (PCR) was performed on room air (RA) and OIR mice.

RESULTS

Total Vegfa messenger RNA (mRNA) expression was stable in RA mice, but increased in OIR mice with a peak at postnatal day 17 (P17), before returning to RA levels. Vegfa_164a expression was similar in both OIR and RA mice at P10 (Phase 1 OIR), but 2.4-fold higher in OIR mice compared to RA mice at P16 (Phase 2 OIR). At P10, Vegfa_164b mRNA was similar in OIR vs RA mice, but was expressed 2.5-fold higher in OIR mice compared to RA mice at P16. At P10 and P16, Vegfr2/Vegfr1 expression was increased in OIR mice compared to RA mice. Increased activation of microglia was seen in OIR mice.

CONCLUSIONS

Vegfa_164a, Vegfa_164b, and Vegfr1 were overexpressed in OIR mice, leading to abnormal signaling and angiogenesis. Further studies of mechanisms of Vegf dysregulation may lead to novel therapies for ROP and other proliferative retinopathies.

IMPACT

Vegfa₁₆₄ has two major isoforms, a proangiogenic, Vegfa_164a, and an antiangiogenic, Vegfa_164b, with opposing receptors, inhibitory Vegfr1, and stimulatory Vegfr2, but their role in OIR is unclear. In Phase 1 OIR, both isoforms and receptors are expressed similarly. In Phase 2 OIR, both isoforms are overexpressed, with an increased ratio of inhibitory Vegfr1. Modulation of angiogenesis by Vegf regulation enables pruning of excess angiogenesis during physiology, but results in ineffective angiogenesis during OIR. Knowledge of VEGF dysregulation may have novel therapeutic implications in the management of ROP and retinal proliferative diseases.

Hypoxia-inducible factor-1β is essential for upregulation of the hypoxia-induced FLT1 gene in placental trophoblasts

Placental hypoxia and increased levels of maternal blood anti-angiogenic protein, soluble fms-like tyrosine kinase-1 (sFLT1), are associated with the pathogenesis of pre-eclampsia. We have demonstrated that hypoxia-inducible factor (HIF)-2α mediates the upregulation of the hypoxia-induced FLT1 gene in trophoblasts and their cell lines. Here, we investigated the involvement of HIF-1β, which acts as a dimerization partner for HIF-α, in the upregulation of the FLT1 gene via hypoxia. We confirmed the interactions between HIF-1β and HIF-2α in the nuclei of BeWo, JAR and JEG-3 cells under hypoxia via co-immunoprecipitation. We found that hypoxia-induced upregulation of the FLT1 gene in BeWo cells and secretion of sFLT1 in human primary trophoblasts were significantly reduced by siRNAs targeting HIF-1β. Moreover, the upregulation of the FLT1 gene in BeWo cells induced by dimethyloxaloylglycine (DMOG) was also inhibited by silencing either HIF-2α or HIF-1β mRNA. It was recently shown that DNA demethylation increases both basal and hypoxia-induced expression levels of the FLT1 gene in three trophoblast-derived cell lines. In the demethylated BeWo cells, siRNAs targeting HIF-2α and HIF-1β suppressed the further increase in the expression levels of the FLT1 gene due to hypoxia or treatment with DMOG. However, luciferase reporter assays and bisulfite sequencing revealed that a hypoxia response element (-966 to -962) of the FLT1 gene is not involved in hypoxia or DMOG-induced upregulation of the FLT1 gene. These findings suggest that HIF-1β is essential for the elevated production of sFLT1 in the hypoxic trophoblasts and that the HIF-2α/HIF-1β complex may be a crucial therapeutic target for pre-eclampsia.

Angiogenic Potential of VEGF Mimetic Peptides for the Biofunctionalization of Collagen/Hydroxyapatite Composites

Currently, the focus on bioinspired concepts for the development of tissue engineering constructs is increasing. For this purpose, the combination of collagen (Coll) and hydroxyapatite (HA) comes closest to the natural composition of the bone. In order to confer angiogenic properties to the scaffold material, vascular endothelial growth factor (VEGF) is frequently used. In the present study, we used a VEGF mimetic peptide (QK) and a modified QK-peptide with a poly-glutamic acid tag (E7-QK) to enhance binding to HA, and analyzed in detail binding efficiency and angiogenic properties. We detected a significantly higher binding efficiency of E7-QK peptides to hydroxyapatite particles compared to the unmodified QK-peptide. Tube formation assays revealed similar angiogenic functions of E7-QK peptide (1µM) as induced by the entire VEGF protein. Analyses of gene expression of angiogenic factors and their receptors (FLT-1, KDR, HGF, MET, IL-8, HIF-1α, MMP-1, IGFBP-1, IGFBP-2, VCAM-1, and ANGPT-1) showed higher expression levels in HUVECs cultured in the presence of 1 µM E7-QK and VEGF compared to those detected in the negative control group without any angiogenic stimuli. In contrast, the expression of the anti-angiogenic gene TIMP-1 showed lower mRNA levels in HUVECs cultured with E7-QK and VEGF. Sprouting assays with HUVEC spheroids within Coll/HA/E7-QK scaffolds showed significantly longer sprouts compared to those induced within Coll/HA/QK or Coll/HA scaffolds. Our results demonstrate a significantly better functionality of the E7-QK peptide, electrostatically bound to hydroxyapatite particles compared to that of unmodified QK peptide. We conclude that the used E7-QK peptide represents an excellently suited biomolecule for the generation of collagen/hydroxyapatite composites with angiogenic properties.

Altitude, Exercise, and Skeletal Muscle Angio-Adaptive Responses to Hypoxia: A Complex Story

Hypoxia, defined as a reduced oxygen availability, can be observed in many tissues in response to various physiological and pathological conditions. As a hallmark of the altitude environment, ambient hypoxia results from a drop in the oxygen pressure in the atmosphere with elevation. A hypoxic stress can also occur at the cellular level when the oxygen supply through the local microcirculation cannot match the cells’ metabolic needs. This has been suggested in contracting skeletal myofibers during physical exercise. Regardless of its origin, ambient or exercise-induced, muscle hypoxia triggers complex angio-adaptive responses in the skeletal muscle tissue. These can result in the expression of a plethora of angio-adaptive molecules, ultimately leading to the growth, stabilization, or regression of muscle capillaries. This remarkable plasticity of the capillary network is referred to as angio-adaptation. It can alter the capillary-to-myofiber interface, which represent an important determinant of skeletal muscle function. These angio-adaptive molecules can also be released in the circulation as myokines to act on distant tissues. This review addresses the respective and combined potency of ambient hypoxia and exercise to generate a cellular hypoxic stress in skeletal muscle. The major skeletal muscle angio-adaptive responses to hypoxia so far described in this context will be discussed, including existing controversies in the field. Finally, this review will highlight the molecular complexity of the skeletal muscle angio-adaptive response to hypoxia and identify current gaps of knowledges in this field of exercise and environmental physiology.

Angiogenesis induction in breast cancer: A paracrine paradigm

Breast cancer is the most prevalent type of cancer among women globally. Angiogenesis contributes significantly to breast cancer progression and dissemination. Neovascularization is concurrent with the progression and growth of breast cancer. Breast cancer cells control angiogenesis by secreting pro-angiogenic factors like fibroblast growth factor, vascular endothelial growth factor, interleukin, transforming growth factor-β, platelet-derived growth factor and several others. These pro-angiogenic factors trigger neovascularization, and thereby lead to breast cancer development and metastasis. The hypoxia-inducible factor (HIF)-regulated angiogenesis cascade is a crucial underlying factor in breast cancer growth and metastasis. To that end, several efforts have been made to identify druggable targets within the HIF-angiogenesis components. However, escape pathways are a major hindrance for targeted therapies against angiogenesis. Thus, understanding the key factors that trigger breast cancer angiogenesis is critical in elucidating ways to inhibit breast cancer. The current review provides an overview of the key growth factors that trigger breast cancer angiogenesis.

VEGFR1 signaling in retinal angiogenesis and microinflammation

Five vascular endothelial growth factor receptor (VEGFR) ligands (VEGF-A, -B, -C, -D, and placental growth factor [PlGF]) constitute the VEGF family. VEGF-A binds VEGF receptors 1 and 2 (VEGFR1/2), whereas VEGF-B and PlGF only bind VEGFR1. Although much research has been conducted on VEGFR2 to elucidate its key role in retinal diseases, recent efforts have shown the importance and involvement of VEGFR1 and its family of ligands in angiogenesis, vascular permeability, and microinflammatory cascades within the retina. Expression of VEGFR1 depends on the microenvironment, is differentially regulated under hypoxic and inflammatory conditions, and it has been detected in retinal and choroidal endothelial cells, pericytes, retinal and choroidal mononuclear phagocytes (including microglia), Müller cells, photoreceptor cells, and the retinal pigment epithelium. Whilst the VEGF-A decoy function of VEGFR1 is well established, consequences of its direct signaling are less clear. VEGFR1 activation can affect vascular permeability and induce macrophage and microglia production of proinflammatory and proangiogenic mediators. However the ability of the VEGFR1 ligands (VEGF-A, PlGF, and VEGF-B) to compete against each other for receptor binding and to heterodimerize complicates our understanding of the relative contribution of VEGFR1 signaling alone toward the pathologic processes seen in diabetic retinopathy, retinal vascular occlusions, retinopathy of prematurity, and age-related macular degeneration. Clinically, anti-VEGF drugs have proven transformational in these pathologies and their impact on modulation of VEGFR1 signaling is still an opportunity-rich field for further research.

Hypoxia Pathway Proteins and Their Impact on the Blood Vasculature

Every cell in the body requires oxygen for its functioning, in virtually every animal, and a tightly regulated system that balances oxygen supply and demand is therefore fundamental. The vascular network is one of the first systems to sense oxygen, and deprived oxygen (hypoxia) conditions automatically lead to a cascade of cellular signals that serve to circumvent the negative effects of hypoxia, such as angiogenesis associated with inflammation, tumor development, or vascular disorders. This vascular signaling is driven by central transcription factors, namely the hypoxia inducible factors (HIFs), which determine the expression of a growing number of genes in endothelial cells and pericytes. HIF functions are tightly regulated by oxygen sensors known as the HIF-prolyl hydroxylase domain proteins (PHDs), which are enzymes that hydroxylate HIFs for eventual proteasomal degradation. HIFs, as well as PHDs, represent attractive therapeutic targets under various pathological settings, including those involving vascular (dys)function. We focus on the characteristics and mechanisms by which vascular cells respond to hypoxia under a variety of conditions.

Carbonic anhydrase IX and hypoxia-inducible factor 1 attenuate cardiac dysfunction after myocardial infarction

Myocardial infarction (MI) is one of the leading causes of death worldwide. Prognosis and mortality rate are directly related to infarct size and post-infarction pathological heart remodeling, which can lead to heart failure. Hypoxic MI-affected areas increase the expression of hypoxia-inducible factor (HIF-1), inducing infarct size reduction and improving cardiac function. Hypoxia translocates HIF-1 to the nucleus, activating carbonic anhydrase IX (CAIX) transcription. CAIX regulates myocardial intracellular pH, critical for heart performance. Our objective was to investigate CAIX participation and relation with sodium bicarbonate transporters 1 (NBC1) and HIF-1 in cardiac remodeling after MI. We analyzed this pathway in an "in vivo" rat coronary artery ligation model and isolated cardiomyocytes maintained under hypoxia. Immunohistochemical studies revealed an increase in HIF-1 levels after 2 h of infarction. Similar results were observed in 2-h infarcted cardiac tissue (immunoblotting) and in hypoxic cardiomyocytes with a nuclear distribution (confocal microscopy). Immunohistochemical studies showed an increase CAIX in the infarcted area at 2 h, mainly distributed throughout the cell and localized in the plasma membrane at 24 h. Similar results were observed in 2 h in infarcted cardiac tissue (immunoblotting) and in hypoxic cardiomyocytes (confocal microscopy). NBC1 expression increased in cardiac tissue after 2 h of infarction (immunoblotting). CAIX and NBC1 interaction increases in cardiac tissue subjected to MI for 2h when CAIX is present (immunoprecipitation). These results suggest that CAIX interacts with NBC1 in our infarct model as a mechanism to prevent acidic damage in hypoxic tissue, making it a promising therapeutic target.

Impact of Hypoxia over Human Viral Infections and Key Cellular Processes

Oxygen is essential for aerobic cells, and thus its sensing is critical for the optimal maintenance of vital cellular and tissue processes such as metabolism, pH homeostasis, and angiogenesis, among others. Hypoxia-inducible factors (HIFs) play central roles in oxygen sensing. Under hypoxic conditions, the α subunit of HIFs is stabilized and forms active heterodimers that translocate to the nucleus and regulate the expression of important sets of genes. This process, in turn, will induce several physiological changes intended to adapt to these new and adverse conditions. Over the last decades, numerous studies have reported a close relationship between viral infections and hypoxia. Interestingly, this relation is somewhat bidirectional, with some viruses inducing a hypoxic response to promote their replication, while others inhibit hypoxic cellular responses. Here, we review and discuss the cellular responses to hypoxia and discuss how HIFs can promote a wide range of physiological and transcriptional changes in the cell that modulate numerous human viral infections.

Biologics and their delivery systems: Trends in myocardial infarction

Cardiovascular disease is the leading cause of death around the world, in which myocardial infarction (MI) is a precipitating event. However, current therapies do not adequately address the multiple dysregulated systems following MI. Consequently, recent studies have developed novel biologic delivery systems to more effectively address these maladies. This review utilizes a scientometric summary of the recent literature to identify trends among biologic delivery systems designed to treat MI. Emphasis is placed on sustained or targeted release of biologics (e.g. growth factors, nucleic acids, stem cells, chemokines) from common delivery systems (e.g. microparticles, nanocarriers, injectable hydrogels, implantable patches). We also evaluate biologic delivery system trends in the entire regenerative medicine field to identify emerging approaches that may translate to the treatment of MI. Future developments include immune system targeting through soluble factor or chemokine delivery, and the development of advanced delivery systems that facilitate the synergistic delivery of biologics.

Targeting neovascularization and respiration of tumor grafts grown on chick embryo chorioallantoic membranes

Since growing tumors stimulate angiogenesis, via vascular endothelial growth factor (VEGF), angiogenesis inhibitors (AIs, blockers of the VEGF signaling pathway) have been introduced to cancer therapy. However, AIs often yielded only modest and short-lived gains in cancer patients and more invasive tumor phenotypes in animal models. Combining anti-VEGF strategies with lactate uptake blockers may boost both efficacy and safety of AIs. We assessed this hypothesis by using the ex ovo chorioallantoic membrane (CAM) assay. We show that AI-based monotherapy (Avastin®, AVA) increases tumor hypoxia in human CAM cancer cell xenografts and cell spread in human as well as canine CAM cancer cell xenografts. In contrast, combining AVA treatment with lactate importer MCT1 inhibitors (α-cyano-4-hydroxycinnamic acid (CHC) or AZD3965 (AZD)) reduced both tumor growth and cell dissemination of human and canine explants. Moreover, combining AVA+AZD diminished blood perfusion and tumor hypoxia in human explants. Thus, the ex ovo CAM assay as an easy, fast and cheap experimental setup is useful for pre-clinical cancer research. Moreover, as an animal-free experimental setup the CAM assay can reduce the high number of laboratory animals used in pre-clinical cancer research.

Cupriferous Silver Peroxysulfite Superpyramids as a Universal and Long-Lasting Agent to Eradicate Multidrug-Resistant Bacteria and Promote Wound Healing

Because of the emergent evolution of multidrug-resistant (MDR) bacteria, resistance to traditional antibiotics has been increasingly causing public health concerns that it can rapidly overcome the development of antibacterial agents. Here, we demonstrated a facile electrodeposition method to prepare silver peroxysulfite (Ag₇O₈HSO₄, AOHS) superpyramids on band-aids with extraordinary antibacterial performance. The porous structure and the sharp apex of AOHS superpyramids could facilitate the release of high-valence silver ions, which possess highly efficient MDR bacteria-killing effect and keep long-term antibacterial activity (>99% killing efficiency, recycle at least 4 times) because of their superior destruction capability of the membrane of the bacteria. A layer of copper was further evaporated onto the AOHS pyramids decorated on a band-aid, which could promote wound tissue angiogenesis and prohibit bacterial infection simultaneously, and finally accelerate the healing process in MDR bacteria-infected wound in vivo. The simple and low-cost fabrication process, as well as the outstanding antibacterial performance, make AOHS pyramids have promising applications in bacterial infection and practical sterilization fields, especially toward multidrug-resistant bacteria.

The effects of high fat diet, bone healing, and BMP-2 treatment on endothelial cell growth and function

Angiogenesis is a vital process during the regeneration of bone tissue. The aim of this study was to investigate angiogenesis at the fracture site as well as at distal locations from obesity-induced type 2 diabetic mice that were treated with bone morphogenetic protein-2 (BMP-2, local administration at the time of surgery) to heal a femoral critical sized defect (CSD) or saline as a control. Mice were fed a high fat diet (HFD) to induce a type 2 diabetic-like phenotype while low fat diet (LFD) animals served as controls. Endothelial cells (ECs) were isolated from the lungs (LECs) and bone marrow (BMECs) 3 weeks post-surgery, and the fractured femurs were also examined. Our studies demonstrate that local administration of BMP-2 at the fracture site in a CSD model results in complete bone healing within 3 weeks for all HFD mice and 66.7% of LFD mice, whereas those treated with saline remain unhealed. At the fracture site, vessel parameters and adipocyte numbers were significantly increased in BMP-2 treated femurs, irrespective of diet. At distal sites, LEC and BMEC proliferation was not altered by diet or BMP-2 treatment. HFD increased the tube formation ability of both LECs and BMECs. Interestingly, BMP-2 treatment at the time of surgery reduced tube formation in LECs and humeri BMECs. However, migration of BMECs from HFD mice treated with BMP-2 was increased compared to BMECs from HFD mice treated with saline. BMP-2 treatment significantly increased the expression of CD31, FLT-1, and ANGPT2 in LECs and BMECs in LFD mice, but reduced the expression of these same genes in HFD mice. To date, this is the first study that depicts the systemic influence of fracture surgery and local BMP-2 treatment on the proliferation and angiogenic potential of ECs derived from the bone marrow and lungs.

Clinical implications of placenta-derived angiogenic/anti-angiogenic biomarkers in pre-eclampsia

Pre-eclampsia (PE) is a devastating systemic disease which results in maternal hypertension with multi-organ failure due to angiogenic imbalance, characterized by lack of circulating pro-angiogenic factors and excess of anti-angiogenic factors. These factors are crucial for understanding the pathophysiology of PE since they serve as a critical link from placental dysfunction to the clinical syndrome of systemic endothelial dysfunction in the disease. Moreover, utilizing these angiogenic/anti-angiogenic biomarkers can be helpful in risk stratifying and the early detection of PE, which allows for timely intervention to improve maternal and neonatal outcomes. In this review, we summarize updated perspectives of the angiogenic imbalance in PE with detailed characterization of key factors involved in the pathogenesis and how the developed biomarkers can be used in clinical settings as diagnostic tools and as possible therapeutic targets of PE.

The role of mediating factors involved in angiogenesis during implantation

Angiogenesis is a critical component of normal implantation and placentation and underlines the importance of vascularization in early pregnancy. Differentiated expression of angiogenesis factors in different decision tissues during different stages of implantation, indicates their involvement in the regulation of vascular remodeling and angiogenesis. Disorders in vascular development may play a role in the pathogenesis of recurrent abortions. The success of implantation, placentation and subsequent pregnancy evolution requires coordination of vascular development and adaptations at both sides of the maternal–fetal interface. The human implantation process is a continuous process, which begins with the apposition and attachment of the blastocyst to the apical surface of the luminal endometrial epithelium and continues throughout the first trimester of pregnancy until the extravillous trophoblast invades and remodels maternal vascularization. Numerous regulatory molecules play functional roles in many processes, including preparation of the endometrial stroma (decidualization), epithelium for implantation, control of trophoblastic adhesion and invasion. These regulatory molecules include cytokines, chemokines, and proteases, many of which are expressed by different cell types, having slightly different functions as the implant progresses

Influence of VEGF-A, VEGFR-1-3, and neuropilin 1-2 on progression-free: and overall survival in WHO grade II and III meningioma patients

Higher grade meningiomas tend to recur. We aimed to evaluate protein levels of vascular endothelial growth factor (VEGF)-A with the VEGF-receptors 1-3 and the co-receptors Neuropilin (NRP)-1 and -2 in WHO grade II and III meningiomas to elucidate the rationale for targeted treatments. We investigated 232 specimens of 147 patients suffering from cranial meningioma, including recurrent tumors. Immunohistochemistry for VEGF-A, VEGFR-1-3, and NRP-1/-2 was performed on tissue micro arrays. We applied a semiquantitative score (staining intensity x frequency). VEGF-A, VEGFR-1-3, and NRP-1 were heterogeneously expressed. NRP-2 was mainly absent. We demonstrated a significant increase of VEGF-A levels on tumor cells in WHO grade III meningiomas (p = 0.0098). We found a positive correlation between expression levels of VEGF-A and VEGFR-1 on tumor cells and vessels (p < 0.0001). In addition, there was a positive correlation of VEGF-A and VEGFR-3 expression on tumor vessels (p = 0.0034). VEGFR-2 expression was positively associated with progression-free survival (p = 0.0340). VEGF-A on tumor cells was negatively correlated with overall survival (p = 0.0084). The VEGF-A-driven system of tumor angiogenesis might still present a suitable target for adjuvant therapy in malignant meningioma disease. However, its role in malignant tumor progression may not be as crucial as expected. The value of comprehensive testing of the ligand and all receptors prior to administration of anti-angiogenic therapy needs to be evaluated in clinical trials.

Decreased inspired oxygen stimulates de novo formation of coronary collaterals in adult heart

RATIONALE

Collateral vessels lessen myocardial ischemia when acute or chronic coronary obstruction occurs. It has long been assumed that although native (pre-existing) collaterals enlarge in obstructive disease, new collaterals do not form in the adult. However, the latter was recently shown to occur after coronary artery ligation. Understanding the signals that drive this process is challenged by the difficulty in studying collateral vessels directly and the complex milieu of signaling pathways, including cell death, induced by ligation. Herein we show that hypoxemia alone is capable of inducing collateral vessels to form and that the novel gene Rabep2 is required.

OBJECTIVE

Hypoxia stimulates angiogenesis during embryonic development and in pathological states. We hypothesized that hypoxia also stimulates collateral formation in adult heart by a process that involves RABEP2, a recently identified protein required for formation of collateral vessels during development.

METHODS AND RESULTS

Exposure of mice to reduced FiO2 induced collateral formation that resulted in smaller infarctions following LAD ligation and that reversed on return to normoxia. Deletion of Rabep2 or knockdown of Vegfa inhibited formation. Hypoxia upregulated Rabep2, Vegfa and Vegfr2 in heart and brain microvascular endothelial cells (HBMVECs). Knockdown of Rabep2 impaired migration of HBMVECs. In contrast to systemic hypoxia, deletion of Rabep2 did not affect collateral formation induced by ischemic injury caused by LAD ligation.

CONCLUSIONS

Hypoxia induced formation of coronary collaterals by a process that required VEGFA and RABEP2, proteins also required for collateral formation during development. Knockdown of Rabep2 impaired cell migration, providing one potential mechanism for RABEP2's role in collateral formation. This appears specific to hypoxia, since formation after acute ischemic injury was unaffected in Rabep2-/- mice. These findings provide a novel model for studying coronary collateral formation, and demonstrate that hypoxia alone can induce new collaterals to form in adult heart.

TRIM28 regulates sprouting angiogenesis through VEGFR-DLL4-Notch signaling circuit

Sprouting angiogenesis is a highly coordinately process controlled by vascular endothelial growth factor receptor (VEGFR)-Notch signaling. Here we investigated whether Tripartite motif-containing 28 (TRIM28), which is an epigenetic modifier implicated in gene transcription and cell differentiation, is essential to mediate sprouting angiogenesis. We observed that knockdown of TRIM28 ortholog in zebrafish resulted in developmental vascular defect with disorganized and reduced vasculatures. Consistently, TRIM28 knockdown inhibited angiogenic sprouting of cultured endothelial cells (ECs), which exhibited increased mRNA levels of VEGFR1, Delta-like (DLL) 3, and Notch2 but reduced levels of VEGFR2, DLL1, DLL4, Notch1, Notch3, and Notch4.The regulative effects of TRIM28 on these angiogenic factors were partially mediated by hypoxia-inducible factor 1 α (HIF-1α) and recombination signal-binding protein for immunoglobulin kappa J region (RBPJκ). In vitro DNA-binding assay showed that TRIM28 knockdown increased the association of RBPJκ with DNA sequences containing HIF-1α-binding sites. Moreover, the phosphorylation of TRIM28 was controlled by VEGF and Notch1 through a mechanism involving RBPJκ-dual-specificity phosphatase (DUSP)-p38 MAPK, indicating a negative feedback mechanism. These findings established TRIM28 as a crucial regulator of VEGFR-Notch signaling circuit through HIF-1α and RBPJκ in EC sprouting angiogenesis.

Gene Therapy Intervention in Neovascular Eye Disease: A Recent Update

Aberrant growth of blood vessels (neovascularization) is a key feature of severe eye diseases that can cause legal blindness, including neovascular age-related macular degeneration (nAMD) and diabetic retinopathy (DR). The development of anti-vascular endothelial growth factor (VEGF) agents has revolutionized the treatment of ocular neovascularization. Novel proangiogenic targets, such as angiopoietin and platelet-derived growth factor (PDGF), are under development for patients who respond poorly to anti-VEGF therapy and to reduce adverse effects from long-term VEGF inhibition. A rapidly advancing area is gene therapy, which may provide significant therapeutic benefits. Viral vector-mediated transgene delivery provides the potential for continuous production of antiangiogenic proteins, which would avoid the need for repeated anti-VEGF injections. Gene silencing with RNA interference to target ocular angiogenesis has been investigated in clinical trials. Proof-of-concept gene therapy studies using gene-editing tools such as CRISPR-Cas have already been shown to be effective in suppressing neovascularization in animal models, highlighting the therapeutic potential of the system for treatment of aberrant ocular angiogenesis. This review provides updates on the development of anti-VEGF agents and novel antiangiogenic targets. We also summarize current gene therapy strategies already in clinical trials and those with the latest approaches utilizing CRISPR-Cas gene editing against aberrant ocular neovascularization.

The Effect of MicroRNA-101 on Angiogenesis of Human Umbilical Vein Endothelial Cells during Hypoxia and in Mice with Myocardial Infarction

Background

Previous studies showed that recanalization and angiogenesis within the infarct region are of vital importance to the survival of myocardial cells during the treatment of acute myocardial infarction (AMI).

Methods

In this study, EdU cell proliferation assay, Transwell assay, scratch wound assay, and tube formation assay were used. Twelve bioinformatics analysis packages were used to predict the target genes of miR-101. Target genes were verified by luciferase reporter generation and assay, fluorescent quantitative PCR, and western blotting. Animal model and treatments were detected by M-mode echocardiography and immunofluorescent staining of CD31, Ki67, and α-SMA.

Results

AgomiR-101 significantly enhanced HUVEC proliferation, migration, and tube formation. A double-luciferase reporter assay revealed that the hsa-miR-101 mimic attenuated the activity of the EIF4E3′-UTR-wt type plasmid by 36%. The expression levels of HIF-1α and VEGF-A in the scrambled RNA group were significantly lower than those in the EIF4E3 siRNA and agomiR-101 groups. The left ventricular ejection fraction of the AMI+Adv-miR-101 group was significantly higher than that of the AMI+Adv-null and Sham+Adv-null groups. The proliferation of vessel cells in the peripheral infarcted myocardium was higher in the AMI+Adv-miR-101 group than that in the AMI+Adv-null and Sham+Adv-null groups.

Conclusion

MiR-101 can promote angiogenesis in the region surrounding the myocardial infarction.

Transcription factor AP2A affects sFLT1 expression and decidualization in decidual stromal cells: Implications to preeclampsia pathology

Preeclampsia (PE) yields a spectrum of phenotypic expression, leading to varying degrees of hypertension, maternal renal dysfunction and placental insufficiency with resultant maternal and neonatal morbidity. Increased sFLT1 expression contributing to angiogenic factor imbalance, placental hypoxia, failed immune adaptation to the fetus and defective decidualization are among the commonly proposed theories of PE pathogenesis. Recently researchers have focused their attention on the events that occur at the maternal fetal interface as potential contributors to PE pathogenesis. Decidual stromal cells (DSC) isolated from preeclamptic women show diminished ability to decidualize upon stimulation and reduced capacity to downregulate sFlt-1 levels. In this study, we sought to gain insight into the molecular mechanism(s) involved in the aberrant decidualization capacity of PE DSC. Our findings using qRT-PCR show that PE DSCs have 6-fold higher basal levels of transcription factor AP2A (TFAP2A) RNA compared to women without PE and that expression of TFAP2A increases during decidualization but only in DSCs of normotensive (NT) women. Silencing of TFAP2A using Trilencer siRNA upregulated sFLT1 expression only in NT-DSCs but suppressed the expression of decidualization markers PRL, IGFBP1 and their regulator FOXO1 in cells from both groups. Collectively, our observations suggest that TFAP2A acts as a repressor of sFLT1 and plays a necessary role in decidualization possibly through interacting with another factor that is aberrantly expressed in PE DSCs.