Stimulatory effects of insulin and insulin-like growth factor I on migration and tube formation by vascular endothelial cells

Profound Properties of Protein-Rich, Platelet-Rich Plasma Matrices as Novel, Multi-Purpose Biological Platforms in Tissue Repair, Regeneration, and Wound Healing

Autologous platelet-rich plasma (PRP) preparations are prepared at the point of care. Centrifugation cellular density separation sequesters a fresh unit of blood into three main fractions: a platelet-poor plasma (PPP) fraction, a stratum rich in platelets (platelet concentrate), and variable leukocyte bioformulation and erythrocyte fractions. The employment of autologous platelet concentrates facilitates the biological potential to accelerate and support numerous cellular activities that can lead to tissue repair, tissue regeneration, wound healing, and, ultimately, functional and structural repair. Normally, after PRP preparation, the PPP fraction is discarded. One of the less well-known but equally important features of PPP is that particular growth factors (GFs) are not abundantly present in PRP, as they reside outside of the platelet alpha granules. Precisely, insulin-like growth factor-1 (IGF-1) and hepatocyte growth factor (HGF) are mainly present in the PPP fraction. In addition to their roles as angiogenesis activators, these plasma-based GFs are also known to inhibit inflammation and fibrosis, and they promote keratinocyte migration and support tissue repair and wound healing. Additionally, PPP is known for the presence of exosomes and other macrovesicles, exerting cell-cell communication and cell signaling. Newly developed ultrafiltration technologies incorporate PPP processing methods by eliminating, in a fast and efficient manner, plasma water, cytokines, molecules, and plasma proteins with a molecular mass (weight) less than the pore size of the fibers. Consequently, a viable and viscous protein concentrate of functional total proteins, like fibrinogen, albumin, and alpha-2-macroglobulin is created. Consolidating a small volume of high platelet concentrate with a small volume of highly concentrated protein-rich PPP creates a protein-rich, platelet-rich plasma (PR-PRP) biological preparation. After the activation of proteins, mainly fibrinogen, the PR-PRP matrix retains and facilitates interactions between invading resident cells, like macrophages, fibroblast, and mesenchymal stem cells (MSCs), as well as the embedded concentrated PRP cells and molecules. The administered PR-PRP biologic will ultimately undergo fibrinolysis, leading to a sustained release of concentrated cells and molecules that have been retained in the PR-PRP matrix until the matrix is dissolved. We will discuss the unique biological and tissue reparative and regenerative properties of the PR-PRP matrix.

Insulin-like growth factor-binding protein 7 (IGFBP7): A microenvironment-dependent regulator of angiogenesis and vascular remodeling

Insulin-like Growth Factor-Binding Protein 7 (IGFBP7) is an extracellular matrix (ECM) glycoprotein, highly enriched in activated vasculature during development, physiological and pathological tissue remodeling. Despite decades of research, its role in tissue (re-)vascularization is highly ambiguous, exhibiting pro- and anti-angiogenic properties in different tissue remodeling states. IGFBP7 has multiple binding partners, including structural ECM components, cytokines, chemokines, as well as several receptors. Based on current evidence, it is suggested that IGFBP7's bioactivity is strongly dependent on the microenvironment it is embedded in. Current studies indicate that during physiological angiogenesis, IGFBP7 promotes endothelial cell attachment, luminogenesis, vessel stabilization and maturation. Its effects on other stages of angiogenesis and vessel function remain to be determined. IGFBP7 also modulates the pro-angiogenic properties of other signaling factors, such as VEGF-A and IGF, and potentially acts as a growth factor reservoir, while its actual effects on the factors' signaling may depend on the environment IGFBP7 is embedded in. Besides (re-)vascularization, IGFBP7 clearly promotes progenitor and stem cell commitment and may exhibit anti-inflammatory and anti-fibrotic properties. Nonetheless, its role in inflammation, immunomodulation, fibrosis and cellular senescence is again likely to be context-dependent. Future studies are required to shed more light on the intricate functioning of IGFBP7.

Identifying transcriptomic profiles of iron-quercetin complex treated peripheral blood mononuclear cells from healthy volunteers and diabetic patients

Peripheral blood is an alternative source of stem/progenitor cells for regenerative medicine owing to its ease of retrieval and blood bank storage. Previous in vitro studies indicated that the conditioned medium derived from peripheral blood mononuclear cells (PBMCs) treated with the iron-quercetin complex (IronQ) contains potent angiogenesis and wound-healing properties. This study aims to unveil the intricate regulatory mechanisms governing the effects of IronQ on the transcriptome profiles of human PBMCs from healthy volunteers and those with diabetes mellitus (DM) using RNA sequencing analysis. Our findings revealed 3741 and 2204 differentially expressed genes (DEGs) when treating healthy and DM PBMCs with IronQ, respectively. Functional enrichment analyses underscored the biological processes shared by the DEGs in both conditions, including inflammatory responses, cell migration, cellular stress responses, and angiogenesis. A comprehensive exploration of these molecular alterations exposed a network of 20 hub genes essential in response to stimuli, cell migration, immune processes, and the mitogen-activated protein kinase (MAPK) pathway. The activation of these pathways enabled PBMCs to potentiate angiogenesis and tissue repair. Corroborating this, quantitative real-time polymerase chain reaction (qRT-PCR) and cell phenotyping confirmed the upregulation of candidate genes associated with anti-inflammatory, pro-angiogenesis, and tissue repair processes in IronQ-treated PBMCs. In summary, combining IronQ and PBMCs brings about substantial shifts in gene expression profiles and activates pathways that are crucial for tissue repair and immune response, which is promising for the enhancement of the therapeutic potential of PBMCs, especially in diabetic wound healing.

Estimating the impact of drug addiction causes heart damage

To date, few studies have investigated the toxicological effects of the combined use of amphetamine and heroin in the heart. Hence, the aim of this study was to identify indicators for clinical evaluation and prevention of cardiac injury induced by the combined use of amphetamine and heroin. Four different groups were analyzed: (1) normal group (n＝25；average age＝35 ± 6.8); (2) heart disease group (n＝25；average age＝58 ± 17.2); (3) drug abusers (n = 27; average age = 37 ± 7.7); (4) drug abstainers (previous amphetamine-heroin users who had been drug-free for more than two weeks; n = 22; average age = 35 ± 5.6). The activity of MMPs, and levels of TNF-α, IL-6, GH, IGF-I, and several serum biomarkers were examined to evaluate the impact of drug abuse on the heart. The selected plasma biomarkers and classic cardiac biomarkers were significantly increased compared to the normal group. The zymography data showed the changes in cardiac-remodeling enzymes MMP-9 and MMP-2 among combined users of amphetamine and heroin. The levels of TNF-α and IL-6 only increased in the heart disease group. Growth hormone was increased; however, IGF-I level decreased with drug abuse and the level was not restored by abstinence. We speculated that the amphetamine-heroin users might pose risk to initiate heart disease even though the users abstained for more than two weeks. The activity change of MMP-9 and MMP-2 can be a direct reason affecting heart function. The indirect reason may be related to liver damage by drug abuse reduce IGF-1 production to protect heart function.

The Efficacy of Transplanting Human Umbilical Cord Mesenchymal Stem Cell Sheets in the Treatment of Myocardial Infarction in Mice

The transplantation of mesenchymal stem cell (MSC) sheets derived from human umbilical cords (hUCs) was investigated in this study as a potential application in treating myocardial infarction (MI). Two groups of hUC-MSC sheets were formed by populating LunaGelTM, which are 3D scaffolds of photo-crosslinkable gelatin-based hydrogel with two different cell densities. An MI model was created by ligating the left anterior descending coronary artery of healthy BALB/c mice. After two weeks, the cell sheets were applied directly to the MI area and the efficacy of the treatment was evaluated over the next two weeks by monitoring the mice's weight, evaluating the left ventricle ejection fraction, and assessing the histology of the heart tissue at the end of the experiment. Higher cell density showed significantly greater efficiency in MI mice treatment in terms of weight gain and the recovery of ejection fraction. The heart tissue of the groups receiving cell sheets showed human-CD44-positive staining and reduced fibrosis and apoptosis. In conclusion, the hUC-MSC sheets ameliorated heart MI injury in mice and the efficacy of the cell sheets improved as the number of cells increased.

Angiogenesis and Tissue Repair Depend on Platelet Dosing and Bioformulation Strategies Following Orthobiological Platelet-Rich Plasma Procedures: A Narrative Review

Angiogenesis is the formation of new blood vessel from existing vessels and is a critical first step in tissue repair following chronic disturbances in healing and degenerative tissues. Chronic pathoanatomic tissues are characterized by a high number of inflammatory cells; an overexpression of inflammatory mediators; such as tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1); the presence of mast cells, T cells, reactive oxygen species, and matrix metalloproteinases; and a decreased angiogenic capacity. Multiple studies have demonstrated that autologous orthobiological cellular preparations (e.g., platelet-rich plasma (PRP)) improve tissue repair and regenerate tissues. There are many PRP devices on the market. Unfortunately, they differ greatly in platelet numbers, cellular composition, and bioformulation. PRP is a platelet concentrate consisting of a high concentration of platelets, with or without certain leukocytes, platelet-derived growth factors (PGFs), cytokines, molecules, and signaling cells. Several PRP products have immunomodulatory capacities that can influence resident cells in a diseased microenvironment, inducing tissue repair or regeneration. Generally, PRP is a blood-derived product, regardless of its platelet number and bioformulation, and the literature indicates both positive and negative patient treatment outcomes. Strangely, the literature does not designate specific PRP preparation qualifications that can potentially contribute to tissue repair. Moreover, the literature scarcely addresses the impact of platelets and leukocytes in PRP on (neo)angiogenesis, other than a general one-size-fits-all statement that "PRP has angiogenic capabilities". Here, we review the cellular composition of all PRP constituents, including leukocytes, and describe the importance of platelet dosing and bioformulation strategies in orthobiological applications to initiate angiogenic pathways that re-establish microvasculature networks, facilitating the supply of oxygen and nutrients to impaired tissues.

Liver insulin-like growth factor-1 mediates effects of low-intensity vibration on wound healing in diabetic mice

Chronic wounds in diabetic patients are associated with significant morbidity and mortality; however, few therapies are available to improve healing of diabetic wounds. Our group previously reported that low-intensity vibration (LIV) could improve angiogenesis and wound healing in diabetic mice. The purpose of this study was to begin to elucidate the mechanisms underlying LIV-enhanced healing. We first demonstrate that LIV-enhanced wound healing in db/db mice is associated with increased IGF1 protein levels in liver, blood, and wounds. The increase in insulin-like growth factor (IGF) 1 protein in wounds is associated with increased Igf1 mRNA expression both in liver and wounds, but the increase in protein levels preceded the increase in mRNA expression in wounds. Since our previous study demonstrated that liver was a primary source of IGF1 in skin wounds, we used inducible ablation of IGF1 in the liver of high-fat diet (HFD)-fed mice to determine whether liver IGF1 mediated the effects of LIV on wound healing. We demonstrate that knockdown of IGF1 in liver blunts LIV-induced improvements in wound healing in HFD-fed mice, particularly increased angiogenesis and granulation tissue formation, and inhibits the resolution of inflammation. This and our previous studies indicate that LIV may promote skin wound healing at least in part via crosstalk between the liver and wound. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

New insights on the cardiovascular effects of IGF-1

INTRODUCTION

Cardiovascular (CV) disorders are steadily increasing, making them the world's most prevalent health issue. New research highlights the importance of insulin-like growth factor 1 (IGF-1) for maintaining CV health.

METHODS

We searched PubMed and MEDLINE for English and non-English articles with English abstracts published between 1957 (when the first report on IGF-1 identification was published) and 2022. The top search terms were: IGF-1, cardiovascular disease, IGF-1 receptors, IGF-1 and microRNAs, therapeutic interventions with IGF-1, IGF-1 and diabetes, IGF-1 and cardiovascular disease. The search retrieved original peer-reviewed articles, which were further analyzed, focusing on the role of IGF-1 in pathophysiological conditions. We specifically focused on including the most recent findings published in the past five years.

RESULTS

IGF-1, an anabolic growth factor, regulates cell division, proliferation, and survival. In addition to its well-known growth-promoting and metabolic effects, there is mounting evidence that IGF-1 plays a specialized role in the complex activities that underpin CV function. IGF-1 promotes cardiac development and improves cardiac output, stroke volume, contractility, and ejection fraction. Furthermore, IGF-1 mediates many growth hormones (GH) actions. IGF-1 stimulates contractility and tissue remodeling in humans to improve heart function after myocardial infarction. IGF-1 also improves the lipid profile, lowers insulin levels, increases insulin sensitivity, and promotes glucose metabolism. These findings point to the intriguing medicinal potential of IGF-1. Human studies associate low serum levels of free or total IGF-1 with an increased risk of CV and cerebrovascular illness. Extensive human trials are being conducted to investigate the therapeutic efficacy and outcomes of IGF-1-related therapy.

DISCUSSION

We anticipate the development of novel IGF-1-related therapy with minimal side effects. This review discusses recent findings on the role of IGF-1 in the cardiovascular (CVD) system, including both normal and pathological conditions. We also discuss progress in therapeutic interventions aimed at targeting the IGF axis and provide insights into the epigenetic regulation of IGF-1 mediated by microRNAs.

Extracellular vesicles produced by human-induced pluripotent stem cell-derived endothelial cells can prevent arterial stenosis in mice via autophagy regulation

Intravascular transplantation of human-induced pluripotent stem cells (hiPSCs) demonstrated a significant therapeutic effect in the treatment of restenosis by the paracrine function of extracellular vesicles (EVs). However, the risk of tumorigenicity and poor cell survival limits its clinical applications. In this study, we for the first time applied a highly efficient and robust three-dimensional (3D) protocol for hiPSC differentiation into endothelial cells (ECs) with subsequent isolation of EVs from the derived hiPSC-EC (ECs differentiated from hiPSCs), and validated their therapeutic effect in intimal hyperplasia (IH) models. We found that intravenously (iv) injected EVs could accumulate on the carotid artery endothelium and significantly alleviate the intimal thickening induced by the carotid artery ligation. To elucidate the mechanism of this endothelial protection, we performed miRNA expression profiling and found out that among the most conserved endothelial miRNAs, miR-126 was the most abundant in hiPSC-EC-produced EVs (hiPSC-EC-EV). MiR-126 depletion from hiPSC-EC-EV can hinder its protective effect on human umbilical vein endothelial cells (HUVECs) in an inflammatory process. A variety of functional in vitro studies revealed that miR-126 was able to prevent endothelial apoptosis after inflammatory stimulation, as well as promote EC migration and tube formation through autophagy upregulation. The latter was supported by in vivo studies demonstrating that treatment with hiPSC-EC-EV can upregulate autophagy in mouse carotid artery ECs, thereby preventing IH and modulating vascular homeostasis via remodeling of the vascular intima. Our findings suggest a regulatory mechanism for the therapeutic effect on arterial restenosis by autophagy regulation, and provide a potential strategy for clinical treatment of the disease.

Dose Response of Bumetanide on Aquaporins and Angiogenesis Biomarkers in Human Retinal Endothelial Cells Exposed to Intermittent Hypoxia

Aquaporins (AQPs) are important for regulating cellular water, solute transport, and balance. Recently, AQPs have also been recognized as playing a key role in cell migration and angiogenesis. In the retina, hypoxia induces vascular endothelial growth factor (VEGF), a potent angiogenic and vascular permeability factor, resulting in retinal edema, which is facilitated by AQPs. Bumetanide is a diuretic agent and AQP 1–4 blocker. We tested the hypothesis that bumetanide suppression of AQPs ameliorates intermittent hypoxia (IH)-induced angiogenesis and oxidative stress in human microvascular retinal endothelial cells (HMRECs). HMRECs were treated with a low-dose (0.05 µg/mL) or high-dose (0.2 µg/mL) of bumetanide and were exposed to normoxia (Nx), hyperoxia (50% O₂), or IH (50% O₂ with brief hypoxia 5% O₂) for 24, 48, and 72 h. Angiogenesis and oxidative stress biomarkers were determined in the culture media, and the cells were assessed for tube formation capacity and AQP-1 and -4 expression. Both doses of bumetanide significantly decreased oxidative stress and angiogenesis biomarkers. This response was reflected by reductions in tube formation capacity and AQP expression. These findings confirm the role of AQPs in retinal angiogenesis. Therapeutic targeting of AQPs with bumetanide may be advantageous for IH-induced aberrant retinal development.

Vitamin D3 induces mesenchymal-to-endothelial transition and promotes a proangiogenic niche through IGF-1 signaling

Although vitamin D3 (VitD3) prevents angiogenesis in cancer, VitD3 deficiency is associated with greater incidence of cardiovascular events in patients. We examined the influence of VitD3 on the angiogenic potential of mesenchymal stem cells (MSCs). VitD3 treatment increased the expression of proangiogenic molecules in MSCs, which exhibited an endothelial cell-like phenotype and promoted vascularization in vitro and in vivo. VitD3 activated the IGF-1 promoter and boosted IGF-1 receptor (IGF-1R) signaling, which was essential for the mesenchymal-to-endothelial transition (MEndoT) of MSCs. VitD3-treated MSCs created a proangiogenic microenvironment for co-cultured arterial endothelial cells, as well as aortic rings. The induction of MEndoT and angiogenesis promotion by VitD3-stimulated MSCs was attenuated by IGF-1R inhibitor picropodophyllin. We conclude that VitD3 promotes MEndoT in MSCs, and VitD3-treated MSCs augment vascularization by producing a proangiogenic niche through continued IGF-1 secretion. These results suggest a potential therapeutic role of VitD3 toward enhancing MSC-induced angiogenesis.

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Vitamin D3 (VitD3) treatment induces IGF-1 in mesenchymal stem cells (MSCs)

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VitD3 promotes mesenchymal-to-endothelial transition in MSCs via IGF-1 signaling

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Continued IGF-1 secretion by VitD3-treated MSCs creates a proangiogenic niche

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VitD3 may enhance MSC-induced angiogenesis through dual mechanisms

Diagnostic and Prognostic Biomarkers for Myocardial Infarction

The incidence of myocardial infarction (MI) increases every year worldwide. Better diagnostic and prognostic biomarkers for clinical applications are the consistent pursuit of MI research. In addition to electrocardiogram, echocardiography, coronary angiography, etc., circulating biomarkers are essential for the diagnosis, prognosis, and treatment effect monitoring of MI patients. In this review, we assessed both strength and weakness of MI circulating biomarkers including: (1) originated from damaged myocardial tissues including current golden standard cardiac troponin, (2) released from non-myocardial tissues due to MI-induced systems reactions, and (3) preexisted in blood circulation before the occurrence of MI event. We also summarized newly reported MI biomarkers. We proposed that the biomarkers preexisting in blood circulation before MI incidents should be emphasized in research and development for MI prevention in near future.

Combinatorial intranasal delivery of bone marrow mesenchymal stem cells and insulin-like growth factor-1 improves neurovascularization and functional outcomes following focal cerebral ischemia in mice

Bone marrow mesenchymal stem cell (BMSC) transplantation is a promising treatment for ischemic stroke that carries a severe mortality and disability burden amongst the adult population globally. Thus far, BMSC transplantation has been insufficient for ameliorating neurological deficits resulting from cerebral ischemia. This shortcoming may be an outcome due to poor homing and viability of grafted cells in ischemic brain that limit the potential therapeutic benefits of BMSC transplantation. Insulin-like growth factor-1 (IGF-1), a potent anti-apoptotic agent, exerts neuroprotective effects in ischemic stroke as well as rescuing neuronal death in vitro. We hypothesized that IGF-1 could also protect BMSCs from apoptotic death, and examined whether the combination of BMSCs with IGF-1 can enhance functional recovery outcomes in mice following cerebral ischemia. Intranasal administration of BMSCs with IGF-1 was applied in a mouse focal ischemic stroke model. Our in vitro results indicated that BMSCs treated with IGF-1 exhibited less apoptotic death induced by oxygen-glucose deprivation (OGD), and an improved migratory capacity. At 14 days after ischemic insult, the combination of BMSCs with IGF-1 resulted in a larger number of NeuN/BrdU and Glut-1/BrdU co-labeled cells in the areas contiguous to the ischemic core than IGF-1 or BMSC treatment alone. Western blot assays demonstrated that the protein levels of BDNF, VEGF and Ang-1 were significantly upregulated in the peri-infarct region in the combination treatment group compared with single IGF- 1 or BMSC treatment. Co-administration of BMSCs and IGF-1 markedly increases local cerebral blood flow and promoted better functional behavior outcomes. These data suggest that intranasal delivery of BMSCs in conjunction with IGF-1 strengthened functional recovery following ischemia via increasing neurogenesis and angiogenesis, providing a novel optimized strategy for improving the therapeutic efficacy of BMSC transplantation for ischemia.

IGF1, serum glucose, and retinopathy of prematurity in extremely preterm infants

BACKGROUND

Hyperglycemia, insulin insensitivity, and low IGF1 levels in extremely preterm infants are associated with an increased risk of retinopathy of prematurity (ROP), but the interactions are incompletely understood.

METHODS

In 117 extremely preterm infants, serum glucose levels and parenteral glucose intake were recoded daily in the first postnatal week. Serum IGF1 levels were measured weekly. Mice with oxygen-induced retinopathy alone versus oxygen-induced retinopathy plus streptozotocin-induced hyperglycemia/hypoinsulinemia were assessed for glucose, insulin, IGF1, IGFBP1, and IGFBP3 in blood and liver. Recombinant human IGF1 was injected to assess the effect on glucose and retinopathy.

RESULTS

The highest mean plasma glucose tertile of infants positively correlated with parenteral glucose intake [r₍₃₉₎ = 0.67, P < 0.0001]. IGF1 plasma levels were lower in the high tertile compared with those in low and intermediate tertiles at day 28 (P = 0.038 and P = 0.03). In high versus lower glucose tertiles, ROP was more prevalent (34 of 39 versus 19 of 39) and more severe (ROP stage 3 or higher; 71% versus 32%). In oxygen-induced retinopathy, hyperglycemia/hypoinsulinemia decreased liver IGF1 expression (P < 0.0001); rh-IGF1 treatment improved normal vascular regrowth (P = 0.027) and reduced neovascularization (P < 0.0001).

CONCLUSION

In extremely preterm infants, high early postnatal plasma glucose levels and signs of insulin insensitivity were associated with lower IGF1 levels and increased ROP severity. In a hyperglycemia retinopathy mouse model, decreased insulin signaling suppressed liver IGF1 production, lowered serum IGF1 levels, and increased neovascularization. IGF1 supplementation improved retinal revascularization and decreased pathological neovascularization. The data support IGF1 as a potential treatment for prevention of ROP.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02760472 (Donna Mega).

FUNDING

This study has been supported by the Swedish Medical Research Council (14940, 4732, 20144-01-3, and 21144-01-3), a Swedish government grant (ALFGB2770), Lund medical faculty grants (ALFL, 11615 and 11601), the Skåne Council Foundation for Research and Development, the Linnéa and Josef Carlsson Foundation, the Knut and Alice Wallenberg Foundation, the NIH/National Eye Institute (EY022275, EY017017, EY017017-13S1, and P01 HD18655), European Commission FP7 project 305485 PREVENT-ROP, Deutsche Forschungsgemeinschaft (CA-1940/1-1), and Stiftelsen De Blindas Vänner.

In extremely preterm infants, high early postnatal plasma glucose levels and signs of insulin insensitivity were associated with lower IGF1 levels and increased retinopathy of prematurity severity.

Development of novel human in vitro vascularized adipose tissue model with functional macrophages

Inflammation has been proven significant factor in development of type 2 diabetes. So far, most of the adipose tissue related research has been performed in animals, mainly rodent models. The relevance of translation of animal results to humans is questionable. However, in vitro model with relevant human cell source, such as human adipose tissue stromal cells (hASC), can be developed and should be utilized for human adipose tissue research. We developed in vitro models of human adipose tissue utilizing hASC, endothelial cells and monocytes/macrophages. By isolating endothelial cells and macrophages from same adipose tissue as hASC, we were able to provide method for constructing personalized models of adipose tissue. With these models, we studied the effect of macrophages on adipogenesis and protein secretion, with and without vasculature. The models were analyzed for immunocytochemical markers, cell number, triglyceride accumulation and protein secretion. We found that lipid accumulation was greater in adipocytes in the presence of macrophages. Interferon gamma increased this difference between adipocyte culture and Adipocyte-Macrophage co-culture. Protein secretion was affected more by macrophages when vasculature was not present compared to the mild effect when vasculature was present. The vascularized adipose model with macrophages is valuable tool for human adipose tissue research, especially for the personalized medicine approaches; for choosing the right treatments and for studying rare medical conditions.

A Comprehensive Review of Concentrated Growth Factors and Their Novel Applications in Facial Reconstructive and Regenerative Medicine

BACKGROUND

Concentrated growth factors (CGFs) are the latest generation of platelet concentrates. The objective of developing CGF is to increase therapeutic efficacy. However, few studies have supported the superiority of CGF in composition and efficacy. The reconstruction and regeneration process is complicated and long term, whereas bioactivity of CGF is not durable. The purpose of this review is threefold. The first is to recommend more comparative studies between CGF and other platelet concentrates. The second is to constitute a continuous drug delivery system by combining CGF with other biomaterials. Finally, the novel use of CGF in facial regenerative and reconstructive medicine will be highlighted.

METHODS

A comprehensive review of literature regarding the use of CGF in facial regenerative and reconstructive medicine was performed. Based on the inclusion and exclusion criteria, a total of 135 articles were included.

RESULTS

The use of CGF involving facial rejuvenation, cartilage grafting, facial bone defects, facial peripheral nerve injury and wounding is reviewed. The reconstructive and regenerative principles lie in firm fibrin scaffolds and continuous in situ delivery of multiple growth factors.

CONCLUSIONS

CGF represents an advance in personalized medicine concept. However, the current scientific evidences about the use of CGF are limited. More basic and clinical studies should be conducted to understand the characteristics and clinical application of CGF.

LEVEL OF EVIDENCE V

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Regulation of VEGFR2 trafficking and signaling by Rab GTPase-activating proteins

Vascular endothelial growth factor receptor-2 (VEGFR2) and its ligands (VEGFs) are crucial players in vasculogenesis and angiogenesis. General blocking of this signaling system with antibodies or small molecule inhibitors is an established strategy to treat cancer and age-related macular degeneration. Nevertheless, the activated receptor can signal to discrete downstream signaling pathways and the equilibrium between these pathways is modulated by coreceptors and distinct isoforms of VEGF. Here we investigated the influence of Rab GTPase activating proteins (RabGAPs) on VEGFR2 signaling, tube formation, and migration of endothelial cells. We demonstrate that members of the TBC1D10 subfamily of RabGAPs have opposite effects. Whereas TBC1D10A leads to increased Erk1/2 signaling, TBC1D10B lowered Erk1/2 and p38 signaling and reduced tube formation in vitro. TBC1D10A is a RabGAP acting on RAB13 that was shown before to play a role in angiogenesis and we could indeed show colocalization of these two proteins with VEGFR2 in activated cells. In addition, we observed that cells expressing TBC1D10B show lower expression of VEGFR2 and NRP1 on filopodia of activated cells. Taken together, our systematic analysis of influence of RabGAPs on VEGFR2 signaling identifies the TBC1D10 subfamily members as modulators of angiogenesis.

Insulin like growth factor 1 is linked to higher cardiovascular risk score in adults with type 2 diabetes mellitus and chronic kidney disease

INTRODUCTION

Insulin-like growth factor-1 (IGF-1) is a peptide that shares sequence homology with insulin and has endocrine, paracrine and autocrine functions, acts on endothelial cells, and stimulates angiogenesis. IGF1 also affects renal hemodynamics both directly and indirectly by interacting with the renin-angiotensin system.

OBJECTIVE

The study aimed at detecting a relation between age-adjusted IGF1 (AAIGF1) and cardiovascular risk score in adults with type 2 diabetes mellitus and chronic kidney disease.

DESIGN

Patients were 90 females and 42 males with different stages of CKD ranging from 0 to 4. After taking a consent, serum IGF1 was recorded and adjusted for the age of the patient using the IGF1 score equation: {[(log IGF-1 + 0.00625xage)-2.555]/0.104}. Both univariate and multivariate regression analyses of AAIGF1 to different metabolic parameters and microvascular complications of type 2 DM were done. A ROC curve for CV risk score was issued.

RESULTS

AAIGF1 showed a significant bidirectional change with the stage of CKD. Univariate analysis was done including cardiovascular parameters in relations to AAIGF1. A significant positive correlation was found between AAIGF1 and CV risk score (B = 0.036, p = 0.003), SBP (B = 0.030, P = 0.004) and DBP (B = 0.071, P = 0.000), with a reciprocal relation to EF (B = -0.050, P = 0.016). Multivariate regression showed a significant correlation between AAIGF1 and age, HOMAIR, HOMAB, Uric acid. A ROC curve with AUC of 0.675, P = 0.003, showed that AAIGF1 of approximately -1.7 is a cut off for intermediate CV risk (10 year risk score >7.5%).

CONCLUSION

AAIGF1 shows a bidirectional relation to the grade of chronic kidney disease in adults with type 2 DM. A cut off point for AAIGF1 was set to indicate intermediate CV risk score, which can encourage using AAIGF1 as a prognostic marker for higher CV risk score. Medications that modulate IGF1 level can affect CV risk.

Improved angiogenic activity of endothelial progenitor cell in diabetic patients treated with insulin plus metformin

Type 2 diabetes (T2DM) is associated with an increased vascular disease. Moreover, endothelial progenitor cell (EPC) function is impaired in diabetic patients. Decreased EPC number plays a critical role in reduced endothelial repair and development of the vascular disorder. To determine the effect of metformin and insulin plus metformin on functional activity of EPCs, 130 participants were divided into three groups (group 1: healthy control; group 2: metformin; group 3: insulin plus metformin). The concentration of EPCs in the circulation was first quantified. Thereafter, circulating EPCs (cEPCs) were harvested and the biological features of these cells including proliferative, clonogenicity, tubulogenic, and migratory properties were analyzed after expansion. The serum protein levels of some proangiogenic factors were also measured. Our results showed greater numbers of cEPCs in control and in diabetic patients treated with insulin plus metformin than in metformin-treated patients. Insulin plus metformin therapy was associated with augmented proliferative, clonogenicity, migratory, and tubulogenic activity of cEPCs in patients with T2DM. Increased serum concentrations of angiogenic factors were also observed in patients treated with insulin plus metformin. Western blot analysis showed increased protein levels of pTie-2/Tie2 and Pakt/AKT in cEPCs harvested from T2DM, treated with insulin metformin plus. This study showed that treatment with insulin plus metformin in diabetic patients is associated with increased mobilization of EPCs into the circulation, with potential beneficial effect in vascular protection in diabetic patients.

IGF-1 and cardiovascular disease

Atherosclerosis is an inflammatory arterial pathogenic condition, which leads to ischemic cardiovascular diseases, such as coronary artery disease and myocardial infarction, stroke, and peripheral arterial disease. Atherosclerosis is a multifactorial disorder and its pathophysiology is highly complex. Changes in expression of multiple genes coupled with environmental and lifestyle factors initiate cascades of adverse events involving multiple types of cells (e.g. vascular endothelial cells, smooth muscle cells, and macrophages). IGF-1 is a pleiotropic factor, which is found in the circulation (endocrine IGF-1) and is also produced locally in arteries (endothelial cells and smooth muscle cells). IGF-1 exerts a variety of effects on these cell types in the context of the pathogenesis of atherosclerosis. In fact, there is an increasing body of evidence suggesting that IGF-1 has beneficial effects on the biology of atherosclerosis. This review will discuss recent findings relating to clinical investigations on the relation between IGF-1 and cardiovascular disease and basic research using animal models of atherosclerosis that have elucidated some of the mechanisms underlying atheroprotective effects of IGF-1.

IGF2 and IGF1R identified as novel tip cell genes in primary microvascular endothelial cell monolayers

Tip cells, the leading cells of angiogenic sprouts, were identified in cultures of human umbilical vein endothelial cells (HUVECs) by using CD34 as a marker. Here, we show that tip cells are also present in primary human microvascular endothelial cells (hMVECs), a more relevant endothelial cell type for angiogenesis. By means of flow cytometry, immunocytochemistry, and qPCR, it is shown that endothelial cell cultures contain a dynamic population of CD34⁺ cells with many hallmarks of tip cells, including filopodia-like extensions, elevated mRNA levels of known tip cell genes, and responsiveness to stimulation with VEGF and inhibition by DLL4. Furthermore, we demonstrate that our in vitro tip cell model can be exploited to investigate cellular and molecular mechanisms in tip cells and to discover novel targets for anti-angiogenesis therapy in patients. Small interfering RNA (siRNA) was used to knockdown gene expression of the known tip cell genes angiopoietin 2 (ANGPT2) and tyrosine kinase with immunoglobulin-like and EGF-like domains 1 (TIE1), which resulted in similar effects on tip cells and sprouting as compared to inhibition of tip cells in vivo. Finally, we identified two novel tip cell-specific genes in CD34⁺ tip cells in vitro: insulin-like growth factor 2 (IGF2) and IGF-1-receptor (IGF1R). Knockdown of these genes resulted in a significant decrease in the fraction of tip cells and in the extent of sprouting in vitro and in vivo. In conclusion, this study shows that by using our in vitro tip cell model, two novel essential tip cells genes are identified.

Enhancing engineered vascular networks in vitro and in vivo: The effects of IGF1 on vascular development and durability

OBJECTIVES

Creation of functional, durable vasculature remains an important goal within the field of regenerative medicine. Engineered biological vasculature has the potential to restore or improve human tissue function. We hypothesized that the pleotropic effects of insulin-like growth factor 1 (IGF1) would enhance the engineering of capillary-like vasculature.

MATERIALS AND METHODS

The impact of IGF1 upon vasculogenesis was examined in in vitro cultures for a period of up to 40 days and as subcutaneous implants within immunodeficient mice. Co-cultures of human umbilical vein endothelial cells and human bone marrow-derived mesenchymal stem cells in collagen-fibronectin hydrogels were supplemented with either recombinant IGF1 protein or genetically engineered cells to provide sustained IGF1. Morphometric analysis was performed on the vascular networks that formed in four concentrations of IGF1.

RESULTS

IGF1 supplementation significantly enhanced de novo vasculogenesis both in vitro and in vivo. Effects were long-term as they lasted the duration of the study period, and included network density, vessel length, and diameter. Bifurcation density was not affected. However, the highest concentrations of IGF1 tested were either ineffective or even deleterious. Sustained IGF1 delivery was required in vivo as the inclusion of recombinant IGF1 protein had minimal impact.

CONCLUSION

IGF1 supplementation can be used to produce neovasculature with significantly enhanced network density and durability. Its use is a promising methodology for engineering de novo vasculature to support regeneration of functional tissue.

Effect of combined farnesoid X receptor agonist and angiotensin II type 1 receptor blocker on hepatic fibrosis

The farnesoid X receptor (FXR) agonist, a bile acid‐activated nuclear receptor, has been shown to improve the histologic features of nonalcoholic steatohepatitis (NASH); however, a satisfactory effect on hepatic fibrosis has not been achieved. We aimed to investigate the combined effect of FXR agonist and angiotensin II type 1 receptor blocker on hepatic fibrogenesis in rat models of NASH. For 8 weeks, two rat models of NASH were developed. Otsuka Long‐Evans Tokushima Fatty (OLETF) rats were administered intraperitoneal injections of 1 mL/kg pig serum (PS) twice a week, whereas Fischer‐344 rats were fed a choline‐deficient, L‐amino acid‐defined diet (CDAA). The in vitro and in vivo effects of an FXR agonist (INT747) and an angiotensin II type 1 receptor blocker (losartan) on hepatic fibrogenesis were evaluated. In PS‐administered OLETF rats, INT747 and losartan had potent inhibitory effects on hepatic fibrogenesis with suppression of hepatic stellate cell (HSC) activation and expression of transforming growth factor β1 and toll‐like receptor 4. INT747 decreased intestinal permeability by ameliorating zonula occuludens‐1 disruption, whereas losartan directly suppressed activated‐HSC (Ac‐HSC) regulation. The in vitro inhibitory effects of INT747 and losartan on messenger RNA expressions of transforming growth factor β1, toll‐like receptor 4, and myeloid differentiation factor 88 and phosphorylation of nuclear factor‐κB and mothers against decapentaplegic homolog 3 in Ac‐HSC were almost in parallel. Losartan directly inhibited the regulation of Ac‐HSC. Likewise, INT747 in combination with losartan was beneficial on hepatic fibrogenesis in rats fed with CDAA diet. The therapeutic effects of these agents were almost comparable between PS‐administered OLETF and CDAA‐treated rats. Conclusion: INT747 and losartan synergistically suppressed hepatic fibrogenesis by reversing gut barrier dysfunction and inhibiting Ac‐HSC proliferation. Combined therapy may represent a promising novel approach for NASH. (Hepatology Communications 2017;1:928–945)

Acute Ethanol Increases IGF-I-Induced Phosphorylation of ERKs by Enhancing Recruitment of p52-Shc to the Grb2/Shc Complex

Ethanol plays a detrimental role in the development of the brain. Multiple studies have shown that ethanol inhibits insulin-like growth factor I receptor (IGF-IR) function. Because the IGF-IR contributes to brain development by supporting neural growth, survival, and differentiation, we sought to determine the molecular mechanism(s) involved in ethanol's effects on this membrane-associated tyrosine kinase. Using multiple neuronal cell types, we performed Western blot, immunoprecipitation, and GST-pulldowns following acute (1-24 h) or chronic (3 weeks) treatment with ethanol. Surprisingly, exposure of multiple neuronal cell types to acute (up to 24 h) ethanol (50 mM) enhanced IGF-I-induced phosphorylation of extracellular regulated kinases (ERKs), without affecting IGF-IR tyrosine phosphorylation itself, or Akt phosphorylation. This acute increase in ERKs phosphorylation was followed by the expected inhibition of the IGF-IR signaling following 3-week ethanol exposure. We then expressed a GFP-tagged IGF-IR construct in PC12 cells and used them to perform fluorescence recovery after photobleaching (FRAP) analysis. Using these fluorescently labeled cells, we determined that 50 mM ethanol decreased the half-time of the IGF-IR-associated FRAP, which implied that cell membrane-associated signaling events could be affected. Indeed, co-immunoprecipitation and GST-pulldown studies demonstrated that the acute ethanol exposure increased the recruitment of p52-Shc to the Grb2-Shc complex, which is known to engage the Ras-Raf-ERKs pathway following IGF-1 stimulation. These experiments indicate that even a short and low-dose exposure to ethanol may dysregulate function of the receptor, which plays a critical role in brain development. J. Cell. Physiol. 232: 1275-1286, 2017. © 2016 Wiley Periodicals, Inc.

Insulin-like growth factor axis targeting in cancer and tumour angiogenesis - the missing link

Numerous molecular players in the process of tumour angiogenesis have been shown to offer potential for therapeutic targeting. Initially denoted to be involved in malignant transformation and tumour progression, the insulin-like growth factor (IGF) signalling axis has been subject to therapeutic interference, albeit with limited clinical success. More recently, IGFs and their receptors have received attention for their contribution to tumour angiogenesis, which offers novel therapeutic opportunities. Here we review the contribution of this signalling axis to tumour angiogenesis, the mechanisms of resistance to therapy and the interplay with other pro-angiogenic pathways, to offer insight in the renewed interest in the application of IGF axis targeting agents in anti-cancer combination therapies.

Estrogen-IGF-1 interactions in neuroprotection: ischemic stroke as a case study

The steroid hormone 17b-estradiol and the peptide hormone insulin-like growth factor (IGF)-1 independently exert neuroprotective actions in neurologic diseases such as stroke. Only a few studies have directly addressed the interaction between the two hormone systems, however, there is a large literature that indicates potentially greater interactions between the 17b-estradiol and IGF-1 systems. The present review focuses on key issues related to this interaction including IGF-1 and sex differences and common activation of second messenger systems. Using ischemic stroke as a case study, this review also focuses on independent and cooperative actions of estrogen and IGF-1 on neuroprotection, blood brain barrier integrity, angiogenesis, inflammation and post-stroke epilepsy. Finally, the review also focuses on the astrocyte, a key mediator of post stroke repair, as a local source of 17b-estradiol and IGF-1. This review thus highlights areas where significant new research is needed to clarify the interactions between these two neuroprotectants.

Differential regulation of orphan nuclear receptor TR3 transcript variants by novel vascular growth factor signaling pathways

Angiogenesis is a hallmark of many diseases, including cancer, ischemic heart disease, inflammation, and others. It is well known that vascular endothelial growth factor (VEGF) is the most important angiogenic factor. Recently, we demonstrated that orphan nuclear receptor TR3 (mouse Nur77 and rat NGFI-B) plays critical roles in tumor growth and angiogenesis induced by VEGF-A in vitro and in vivo. However, the signaling pathways that mediate the expression of TR3 induced by VEGF are still not completely understood. Here we reported that 3 TR3 transcript variants (TR3-TVs) are expressed at differential levels, and regulated differentially in endothelial cells. While the expression of TR3-TV1 is relatively low, the expression of TR3-TV2 is up-regulated markedly, and the expression of TR3-TV3 is up-regulated moderately in endothelial cells induced by VEGF-A. The kinetics of the induction of these TR3-TVs is different. We also found that several signaling pathways, including calcium-PLC-PKC-PKD1 pathway, NF-κB pathway, and MAP kinase (ERK, p38, and JNK) pathways are important for VEGF-A-induced TR3-TV2 and TR3-TV3 mRNA induction. More important, we found that VEGF-A or VEGF-E, but not VEGF-B, nor placenta growth factor (PlGF), induces the phosphorylation of insulin-like growth factor-1 receptor (IGF-1R) and the interaction of VEGF receptor 2/kinase insert domain receptor (VEGFR2/KDR) with IGF-1R, which mediates the expression of TR3-TV2, but not TR3-TV3. Taking together, we demonstrate that TR3-TVs are differentially regulated by VEGF-A and identify a novel signaling pathway by which VEGF-A and VEGF-E, but neither VEGF-B, nor PlGF, induce the interaction of VEGFR2/KDR with IGF-1R, resulting in IGF-1R transactivation to induce the high level expression of TR3-TV2. Our data not only elucidate the signaling pathways by which TR3-TVs are regulated, but extend the molecular mechanism, by which VEGF-A-induced angiogenesis. These studies should permit the development of screening assays for compounds that inhibit VEGF signaling.

Macrophages in cardiac homeostasis, injury responses and progenitor cell mobilisation

Macrophages are an immune cell type found in every organ of the body. Classically, macrophages are recognised as housekeeping cells involved in the detection of foreign antigens and danger signatures, and the clearance of tissue debris. However, macrophages are increasingly recognised as a highly versatile cell type with a diverse range of functions that are important for tissue homeostasis and injury responses. Recent research findings suggest that macrophages contribute to tissue regeneration and may play a role in the activation and mobilisation of stem cells. This review describes recent advances in our understanding of the role played by macrophages in cardiac tissue maintenance and repair following injury. We examine the involvement of exogenous and resident tissue macrophages in cardiac inflammatory responses and their potential activity in regulating cardiac regeneration.

Targeting tumor micro-environment for design and development of novel anti-angiogenic agents arresting tumor growth

Angiogenesis: a process of generation of new blood vessels has been proved to be necessary for sustained tumor growth and cancer progression. Inhibiting angiogenesis pathway has long been remained a significant hope for the development of novel, effective and target orientated antitumor agents arresting the tumor proliferation and metastasis. The process of neoangiogenesis as a biological process is regulated by several pro- and anti-angiogenic factors, especially vascular endothelial growth factor, fibroblast growth factor, epidermal growth factor, hypoxia inducible factor 1 and transforming growth factor. Every endothelial cell destined for vessel formation is equipped with receptors for these angiogenic peptides. Moreover, numerous other angiogenic cytokines such as platelet derived growth factor (PGDF), placenta growth factor (PGF), nerve growth factor (NGF), stem-cell factor (SCF), and interleukins-2, 4, 6 etc. These molecular players performs critical role in regulating the angiogenic switch. Couple of decade's research in molecular aspects of tumor biology has unraveled numerous structural and functional mysteries of these angiogenic peptides. In present article, a detailed update on the functional and structural peculiarities of the various angiogenic peptides is described focusing on structural opportunities made available that has potential to be used to modulate function of these angiogenic peptides in developing therapeutic agents targeting neoplastic angiogenesis. The data may be useful in the mainstream of developing novel anticancer agents targeting tumor angiogenesis. We also discuss major therapeutic agents that are currently used in angiogenesis associated therapies as well as those are subject of active research or are in clinical trials.

Age-related macular degeneration-associated silent polymorphisms in HtrA1 impair its ability to antagonize insulin-like growth factor 1

Synonymous single nucleotide polymorphisms (SNPs) within a transcript's coding region produce no change in the amino acid sequence of the protein product and are therefore intuitively assumed to have a neutral effect on protein function. We report that two common variants of high-temperature requirement A1 (HTRA1) that increase the inherited risk of neovascular age-related macular degeneration (NvAMD) harbor synonymous SNPs within exon 1 of HTRA1 that convert common codons for Ala34 and Gly36 to less frequently used codons. The frequent-to-rare codon conversion reduced the mRNA translation rate and appeared to compromise HtrA1's conformation and function. The protein product generated from the SNP-containing cDNA displayed enhanced susceptibility to proteolysis and a reduced affinity for an anti-HtrA1 antibody. The NvAMD-associated synonymous polymorphisms lie within HtrA1's putative insulin-like growth factor 1 (IGF-1) binding domain. They reduced HtrA1's abilities to associate with IGF-1 and to ameliorate IGF-1-stimulated signaling events and cellular responses. These observations highlight the relevance of synonymous codon usage to protein function and implicate homeostatic protein quality control mechanisms that may go awry in NvAMD.

An abundant tissue macrophage population in the adult murine heart with a distinct alternatively-activated macrophage profile

Cardiac tissue macrophages (cTMs) are a previously uncharacterised cell type that we have identified and characterise here as an abundant GFP(+) population within the adult Cx(3)cr1(GFP/+) knock-in mouse heart. They comprise the predominant myeloid cell population in the myocardium, and are found throughout myocardial interstitial spaces interacting directly with capillary endothelial cells and cardiomyocytes. Flow cytometry-based immunophenotyping shows that cTMs exhibit canonical macrophage markers. Gene expression analysis shows that cTMs (CD45(+)CD11b(+)GFP(+)) are distinct from mononuclear CD45(+)CD11b(+)GFP(+) cells sorted from the spleen and brain of adult Cx(3)cr1(GFP/+) mice. Gene expression profiling reveals that cTMs closely resemble alternatively-activated anti-inflammatory M2 macrophages, expressing a number of M2 markers, including Mrc1, CD163, and Lyve-1. While cTMs perform normal tissue macrophage homeostatic functions, they also exhibit a distinct phenotype, involving secretion of salutary factors (including IGF-1) and immune modulation. In summary, the characterisation of cTMs at the cellular and molecular level defines a potentially important role for these cells in cardiac homeostasis.

Insulin-like growth factors promote vasculogenesis in embryonic stem cells

The ability of embryonic stem cells to differentiate into endothelium and form functional blood vessels has been well established and can potentially be harnessed for therapeutic angiogenesis. However, after almost two decades of investigation in this field, limited knowledge exists for directing endothelial differentiation. A better understanding of the cellular mechanisms regulating vasculogenesis is required for the development of embryonic stem cell-based models and therapies. In this study, we elucidated the mechanistic role of insulin-like growth factors (IGF1 and 2) and IGF receptors (IGFR1 and 2) in endothelial differentiation using an embryonic stem cell embryoid body model. Both IGF1 or IGF2 predisposed embryonic stem to differentiate towards a mesodermal lineage, the endothelial precursor germ layer, as well as increased the generation of significantly more endothelial cells at later stages. Inhibition of IGFR1 signaling using neutralizing antibody or a pharmacological inhibitor, picropodophyllin, significantly reduced IGF-induced mesoderm and endothelial precursor cell formation. We confirmed that IGF-IGFR1 signaling stabilizes HIF1α and leads to up-regulation of VEGF during vasculogenesis in embryoid bodies. Understanding the mechanisms that are critical for vasculogenesis in various models will bring us one step closer to enabling cell based therapies for neovascularization.

Characterization and modulation of fibroblast/endothelial cell co-cultures for the in vitro preformation of three-dimensional tubular networks

Various assays of different complexity are used in research on angiogenesis in health and disease. The results of these assays increasingly impact the field of tissue engineering because preformed microvascular networks may connect and conduct to the vascular system of the host, thereby helping us to support the survival of implanted cells and tissue constructs. An interesting model that supports the formation of EC (endothelial cells) tubular structures in vitro is based on co-culturing them with fibroblasts. Our initial multilayer approach was recently transferred into a three-dimensional spheroid model using HUVEC (human umbilical vein endothelial cells) as model cells. The aim of the present study is to further characterize, extend and validate this fibroblast/EC spheroid co-culture system. We have evaluated the model with a maximum size of 600-650 μm attained on day 3 from inoculation of 4×104 fibroblasts with 1×104 EC. Cell count and spheroid diameter significantly decreased as a function of time, but the EC network that developed over a period of 14 days in culture was clearly visible and viable, and central cell death was excluded. We successfully included HMVEC (human microvascular endothelial cells) of dermal origin in the system and replaced FBS (fetal bovine serum) with human AB serum, which positively impacted the EC network formation at optimized concentrations. The need for exogenous growth factors [VEGF (vascular endothelial growth factor), EGF (epithelial growth factor), bFGF (basic fibroblast growth factor) and IGF-1 (insulin-like growth factor-1)] routinely added to classical EC media was also assessed. The behaviour of both fibroblasts and EC in response to a combination of these exogenous growth factors differed critically in fibroblast/EC spheroid co-cultures compared with the same cells in the multilayer approach. VEGF was the most relevant exogenous factor for EC network formation in fibroblast/EC multilayers, but was ineffective in the spheroid system. IGF-1 was found, in general, to be dispensable; however, while it had a negative impact on EC networking in the presence of bFGF and EGF in the multilayer, it did not in the spheroid approach. We conclude that the critical determinants of EC network formation and cell survival are not universal, but have to be specifically optimized for each culture model.

Insulin-like growth factor-1 receptor activation prevents hydrogen peroxide-induced oxidative stress, mitochondrial dysfunction and apoptosis

Vascular disease is the leading cause of morbidity and mortality. Oxidative stress can cause endothelial cell apoptosis. Low insulin like growth factor-1 (IGF-1) has been linked to adverse risk profile and increased vascular disease incidence. Since IGF-1 acts as an important survival factor for multiple cell types, we undertook this study to investigate whether IGF-1 favorably affects oxidative-stress mediated apoptosis of vascular endothelial cells. Exposure to hydrogen peroxide induced apoptotic changes (e.g. DNA fragmentation, altered mitochondrial membrane potential and caspase-3 activity) in human umbilical vein endothelial cells (HUVECs) in a time dependent manner. Addition of IGF-1 blocked the oxidative-stress effect parallel to IGF-1 receptor (IGF-1R) expression, and silencing the IGF-1R with small interference RNA attenuated the IGF-1 influence. Our findings show that enhanced IGF-1 signaling inhibits oxidative-stress induced apoptosis in HUVECs by reducing mitochondrial dysfunction. Specifically the protective mechanism of IGF-1 involves preserving the mitochondrial membrane potential, maintaining the mitochondrial retention of cytochrome-c, and reducing caspase-3 activity. These results may have therapeutic implications in preventing/reducing vascular disease associated endothelial dysfunction.

Focal adhesion kinase inhibitors are potent anti-angiogenic agents

Focal adhesion kinase (FAK), a cytoplasmic tyrosine kinase and scaffold protein localized to focal adhesions, is uniquely positioned at the convergence point of integrin and receptor tyrosine kinase signal transduction pathways. FAK is overexpressed in many tumor cells, hence various inhibitors targeting its activity have been tested for anti-tumor activity. However, the direct effects of these pharmacologic agents on the endothelial cells of the vasculature have not been examined. Using primary human umbilical vein endothelial cells (HUVEC), we characterized the effects of two FAK inhibitors, PF-573,228 and FAK Inhibitor 14 on essential processes for angiogenesis, such as migration, proliferation, viability and endothelial cell tube formation. We observed that treatment with either FAK Inhibitor 14 or PF-573,228 resulted in reduced HUVEC viability, migration and tube formation in response to vascular endothelial growth factor (VEGF). Furthermore, we found that PF-573,228 had the added ability to induce apoptosis of endothelial cells within 36 h post-drug administration even in the continued presence of VEGF stimulation. FAK inhibitors also resulted in modification of the actin cytoskeleton within HUVEC, with observed increased stress fiber formation in the presence of drug. Given that endothelial cells were sensitive to FAK inhibitors at concentrations well below those reported to inhibit tumor cell migration, we confirmed their ability to inhibit endothelial-derived FAK autophosphorylation and FAK-mediated phosphorylation of recombinant paxillin at these doses. Taken together, our data indicate that small molecule inhibitors of FAK are potent anti-angiogenic agents and suggest their utility in combinatorial therapeutic approaches targeting tumor angiogenesis.

Intrauterine growth restriction decreases pulmonary alveolar and vessel growth and causes pulmonary artery endothelial cell dysfunction in vitro in fetal sheep

Intrauterine growth restriction (IUGR) increases the risk for bronchopulmonary dysplasia (BPD). Abnormal lung structure has been noted in animal models of IUGR, but whether IUGR adversely impacts fetal pulmonary vascular development and pulmonary artery endothelial cell (PAEC) function is unknown. We hypothesized that IUGR would decrease fetal pulmonary alveolarization, vascular growth, and in vitro PAEC function. Studies were performed in an established model of severe placental insufficiency and IUGR induced by exposing pregnant sheep to elevated temperatures. Alveolarization, quantified by radial alveolar counts, was decreased 20% (P < 0.005) in IUGR fetuses. Pulmonary vessel density was decreased 44% (P < 0.01) in IUGR fetuses. In vitro, insulin increased control PAEC migration, tube formation, and nitric oxide (NO) production. This response was absent in IUGR PAECs. VEGFA stimulated tube formation, and NO production also was absent. In control PAECs, insulin increased cell growth by 68% (P < 0.0001). Cell growth was reduced in IUGR PAECs by 29% at baseline (P < 0.01), and the response to insulin was attenuated (P < 0.005). Despite increased basal and insulin-stimulated Akt phosphorylation in IUGR PAECs, endothelial NO synthase (eNOS) protein expression as well as basal and insulin-stimulated eNOS phosphorylation were decreased in IUGR PAECs. Both VEGFA and VEGFR2 also were decreased in IUGR PAECs. We conclude that fetuses with IUGR are characterized by decreased alveolar and vascular growth and PAEC dysfunction in vitro. This may contribute to the increased risk for adverse respiratory outcomes and BPD in infants with IUGR.

Insulin-like growth factor 1-coated sutures improve anastomotic healing in an experimental model of colitis

BACKGROUND

: Exogenously applied insulin-like growth factor (rhIGF-1) may improve normal intestinal healing. This study examined the effect of rhIGF-1-coated sutures on anastomotic healing in experimental colitis.

METHODS

: Acute colitis was induced in rats by dextran sodium sulphate (DSS). Inflammation was assessed by clinical Disease Activity Index (DAI), myeloperoxidase (MPO) measurement and histological examination. A distal colonic anastomosis was performed using sutures coated with rhIGF-1 dissolved in poly(D,L-lactide) (PDLLA) under general anaesthetic. Anastomotic healing was evaluated histologically, and by hydroxyproline measurement and bursting parameters after 1, 3 and 7 days, and compared with healthy, DSS and DSS + PDLLA controls.

RESULTS

: DAI, MPO and histological inflammation scores were significantly increased in all animals treated with DSS. Bursting occurred less often within the anastomotic line on day 3 in the IGF group than in DSS controls (three versus eight of ten). On day 7, the IGF group had significantly increased histological healing scores (mean(s.e.m.) 12.5(0.7) versus 9.2(0.8) (P < 0.050)) and hydroxyproline content (4.6(0.3) versus 3.6(0.1) mg/g tissue; P < 0.050) compared with DSS controls.

CONCLUSION

: IGF-1-coated sutures improve important aspects of anastomotic healing in rats with experimental colitis.

C-kit+ CD45- cells found in the adult human heart represent a population of endothelial progenitor cells

Although numerous reports support the existence of stem cells in the adult heart, few studies have been conducted using human cardiac tissue. Therefore, cells from human cardiac atrial biopsies were analyzed regarding progenitor properties. Expression of stem cell markers was analyzed using fluorescence-activated cell sorting. This identified a small population of C-kit+ cells, which could be further subdivided based on expression of CD45. The C-kit+ CD45+ population was determined to be of mast cell identity, while the C-kit+ CD45- population expressed mRNA of the endothelial lineage. Since the number of cells obtainable from biopsies was limited, a comparison between directly isolated and monolayer and explant cultured cells, respectively, was carried out. While both cultures retained a small population of mast cells, only monolayer culture produced a stable and relatively high percentage of C-kit+ CD45- cells. This population was found to co-express endothelial progenitor cell markers such as CD31, CD34, CXCR4, and FLK-1. The mRNA expression profile was similar to the one from directly isolated cells. When sorted cells were cultured in endothelial differentiation medium, the C-kit+ CD45- population retained its expression of endothelial markers to a large extent, but downregulated progenitor markers, indicating further differentiation into endothelial cells. We have confirmed that the human cardiac atrium contains a small C-kit+ CD45- population expressing markers commonly found on endothelial progenitor cells. The existence of an endothelial progenitor population within the heart might have future implications for developing methods of inducing neovascularization after myocardial infarction.

Regulation of vascular endothelial growth factor (VEGF) splicing from pro-angiogenic to anti-angiogenic isoforms: a novel therapeutic strategy for angiogenesis

Vascular endothelial growth factor (VEGF) is produced either as a pro-angiogenic or anti-angiogenic protein depending upon splice site choice in the terminal, eighth exon. Proximal splice site selection (PSS) in exon 8 generates pro-angiogenic isoforms such as VEGF₁₆₅, and distal splice site selection (DSS) results in anti-angiogenic isoforms such as VEGF₁₆₅b. Cellular decisions on splice site selection depend upon the activity of RNA-binding splice factors, such as ASF/SF2, which have previously been shown to regulate VEGF splice site choice. To determine the mechanism by which the pro-angiogenic splice site choice is mediated, we investigated the effect of inhibition of ASF/SF2 phosphorylation by SR protein kinases (SRPK1/2) on splice site choice in epithelial cells and in in vivo angiogenesis models. Epithelial cells treated with insulin-like growth factor-1 (IGF-1) increased PSS and produced more VEGF₁₆₅ and less VEGF₁₆₅b. This down-regulation of DSS and increased PSS was blocked by protein kinase C inhibition and SRPK1/2 inhibition. IGF-1 treatment resulted in nuclear localization of ASF/SF2, which was blocked by SPRK1/2 inhibition. Pull-down assay and RNA immunoprecipitation using VEGF mRNA sequences identified an 11-nucleotide sequence required for ASF/SF2 binding. Injection of an SRPK1/2 inhibitor reduced angiogenesis in a mouse model of retinal neovascularization, suggesting that regulation of alternative splicing could be a potential therapeutic strategy in angiogenic pathologies.

Three-dimensional power Doppler sonography of the (sub)endometrium and angiogenic cytokine concentrations

The aim of this study was to determine the correlation between three-dimensional power Doppler sonography (3D-PDS) of the (sub)endometrium and concentrations of angiogenic cytokines in patients attending an IVF programme. A total of 42 patients was included in a prospective, non-randomized clinical study. 3D-PDS of the (sub)endometrium was performed on the day of oocyte aspiration, with and without contrast agent. Quantitative assessment included the following 3D Doppler parameters: vascularization index, flow intensity, and vascularization flow index. On the same day, concentrations of oestradiol (serum only), vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF) 1, IGF-binding protein 3 (IGFBP-3) and leptin were determined in the serum and in the follicular fluid. All 3D-PDS indices were significantly higher with contrast enhancement (P < 0.05). Follicular fluid concentrations of VEGF and IGFBP-3, as well as serum concentrations of leptin, showed significant P-values when correlated with (sub)endometrial Doppler indices. A weak linear dependency appeared between flow intensity and VEGF and leptin. Furthermore, weak dependencies were apparent between 3D Doppler parameters and high follicular fluid concentrations of VEGF and IGFBP-3. It is concluded that there is only little evidence for an association between (sub)endometrial Doppler indices as assessed by 3D-PDS and concentrations of angiogenic cytokines.

Differential regulation of pregnancy associated plasma protein-A in human coronary artery endothelial cells and smooth muscle cells

BACKGROUND

Pregnancy-associated plasma protein-A (PAPP-A), a metalloproteinase that serves to modulate local insulin-like growth factor (IGF) action, is upregulated in atherosclerotic plaque. However, little is known about the cellular mechanisms underlying this elevated PAPP-A.

OBJECTIVE

To continue study of PAPP-A expression and its regulation in human vascular cells, with a focus on endothelial cells.

DESIGN

Primary cultures of human coronary artery endothelial cells (ECs) were treated without and with cytokines, growth factors, or low density lipoprotein (LDL). PAPP-A mRNA, protein, and protease activity were assessed using real-time PCR, ultra-sensitive PAPP-A ELISA and cell-free proteolysis of IGF binding protein (IGFBP-4), respectively. In addition, vascular cell adhesion molecule (VCAM), intercellular adhesion molecule (ICAM), monocyte chemotactic protein (MCP-1), IGF-I, IGF-I receptor, and IGFBP-4 and -5 mRNA expression levels were determined.

RESULTS

ECs in culture show little basal PAPP-A expression. The pro-inflammatory cytokines, tumor necrosis factor (TNF)-alpha and interleukin (IL)-beta, stimulated PAPP-A expression (TNF-alpha>>IL-1beta), whereas there was no effect of IL-6, transforming growth factor-beta, IGF-I, insulin, fibroblast growth factor or epidermal growth factor in these cells. Stimulation of PAPP-A expression by TNF-alpha was associated with significantly increased VCAM, ICAM, and MCP-1 expression but without major changes in other IGF system components. TNF-alpha-induced VCAM, ICAM, and MCP-1 expression (4h) preceded PAPP-A expression (24h). The anti-oxidant, N-acetyl cysteine, inhibited TNF-alpha-induced PAPP-A expression without altering the induction in VCAM, ICAM, and MCP-1. Treatment with native or oxidized LDL had no effect on PAPP-A expression in ECs. Comparative results in human coronary smooth muscle cells indicated qualitative and quantitative differences in PAPP-A expression and regulation between the two vascular cell types.

CONCLUSIONS

Human coronary artery ECs express PAPP-A mRNA and functional protein when activated by the pro-inflammatory cytokine, TNF-alpha. This study complements work on PAPP-A expression in human coronary artery SMCs and human monocyte-derived macrophages and suggests an interactive model of PAPP-A regulation and action in human atherosclerotic plaque.

Adenovirus-mediated transfer of siRNA against MMP-2 mRNA results in impaired invasion and tumor-induced angiogenesis, induces apoptosis in vitro and inhibits tumor growth in vivo in glioblastoma

Invasive tumors, including gliomas, utilize proteinases to degrade extracellular matrix components and diffuse into the adjacent tissues or migrate toward distant ones. In addition, proteinase activity is required for the formation of new blood vessels within the tumor. Levels of the proteinase matrix metalloproteinase-2 (MMP-2) are highly increased in gliomas. In this study, we examined the effect of the downregulation of MMP-2 via adenovirus-mediated siRNA in gliomas. Here, we show that siRNA delivery significantly decreased levels of MMP-2 in the glioblastoma cell lines U-87 and U-251. U-87 and U-251 cells showed impaired invasion through matrigel as well as decreased migration from tumor spheroids transfected with adenoviral vector expressing siRNA against MMP-2. Additionally, tumor-induced angiogenesis was decreased in in vitro experiments in cultured human microvascular endothelial cells (HMECs) in serum-free conditioned medium of glioblastoma cells transfected with these constructs and co-cultures of glioma cells with HMECs. We also observed decreased angiogenesis in the in vivo dorsal skin-fold chamber model. Moreover, MMP-2 inhibition induced apoptotic cell death in vitro, and suppressed tumor growth of preestablished U-251 intracranial xenografts in nude mice. Thus, specific targeting of MMP-2 may provide a novel, efficient approach for the treatment of gliomas and improve the poor outcomes of patients with these brain tumors.

Mechanistic exploration of phthalimide neovascular factor 1 using network analysis tools

Neovascularization is essential for the survival and successful integration of most engineering tissues after implantation in vivo. The objective of this study was to elucidate possible mechanisms of phthalimide neovascular factor 1 (PNF1), a new synthetic small molecule proposed for therapeutic induction of angiogenesis. Complementary deoxyribonucleic acid microarray analysis was used to identify 568 transcripts in human microvascular endothelial cells (HMVECs) that were significantly regulated after 24-h stimulation with 30 muM of PNF1, previously known as SC-3-149. Network analysis tools were used to identify genetic networks of the global biological processes involved in PNF1 stimulation and to describe known molecular and cellular functions that the drug regulated most highly. Examination of the most significantly perturbed networks identified gene products associated with transforming growth factor-beta (TGF-beta), which has many known effects on angiogenesis, and related signal transduction pathways. These include molecules integral to the thrombospondin, plasminogen, fibroblast growth factor, epidermal growth factor, ephrin, Rho, and Ras signaling pathways that are essential to endothelial function. Moreover, real-time reverse-transcriptase polymerase chain reaction (RT-PCR) of select genes showed significant increases in TGF-beta-associated receptors endoglin and beta glycan. These experiments provide important insight into the pro-angiogenic mechanism of PNF1, namely, TGF-beta-associated signaling pathways, and may ultimately offer new molecular targets for directed drug discovery.

Age-dependent impairment of endothelial progenitor cells is corrected by growth-hormone-mediated increase of insulin-like growth-factor-1

Aging is associated with an increased risk for atherosclerosis. A possible cause is low numbers and dysfunction of endothelial progenitor cells (EPC) which insufficiently repair damaged vascular walls. We hypothesized that decreased levels of insulin-like growth factor-1 (IGF-1) during age contribute to dysfunctional EPC. We measured the effect of growth hormone (GH), which increases endogenous IGF-1 levels, on EPC in mice and human subjects. We compared EPC number and function in healthy middle-aged male volunteers (57.4+/-1.4 years) before and after a 10 day treatment with recombinant GH (0.4 mg/d) with that of younger and elderly male subjects (27.5+/-0.9 and 74.1+/-0.9 years). Middle-aged and elderly subjects had lower circulating CD133(+)/VEGFR-2(+) EPC with impaired function and increased senescence. GH treatment in middle-aged subjects elevated IGF-1 levels (126.0+/-7.2 ng/mL versus 241.1+/-13.8 ng/mL; P<0.0001), increased circulating EPC with improved colony forming and migratory capacity, enhanced incorporation into tube-like structures, and augmented endothelial nitric oxide synthase expression in EPC comparable to that of the younger group. EPC senescence was attenuated, whereas telomerase activity was increased after GH treatment. Treatment of aged mice with GH (7 days) or IGF-1 increased IGF-1 and EPC levels and improved EPC function, whereas a two day GH treatment did not alter IGF-1 or EPC levels. Ex vivo treatment of EPC from elderly individuals with IGF-1 improved function and attenuated cellular senescence. IGF-1 stimulated EPC differentiation, migratory capacity and the ability to incorporate into forming vascular networks in vitro via the IGF-1 receptor. IGF-1 increased telomerase activity, endothelial nitric oxide synthase expression, phosphorylation and activity in EPC in a phosphoinositide-3-kinase/Akt dependent manner. Small interference RNA-mediated knockdown of endothelial nitric oxide synthase in EPC abolished the IGF-1 effects. Growth hormone-mediated increase in IGF-1 reverses age-related EPC dysfunction and may be a novel therapeutic strategy against vascular disorders with impairment of EPC.

Insulin-like growth factors control cell migration in health and disease

Insulin-like growth factors I and II (IGF-I and IGF-II) have an ancient origin and play essential roles in fundamental biological processes. Although IGFs are principally known for their roles in regulating cell growth and survival, their ability to influence cell motility is just as significant. In the past 20 years, research has provided indisputable evidence for the regulatory role of IGFs in the migration of various cell types. Cell migration is crucial for reproduction, development, and tissue regeneration; IGFs play an important role in coordinating these processes. Moreover, studies continue to uncover the IGFs' role in stimulating cancer cell migration, invasion and metastasis. This review surveys current knowledge on the cell migration-modulating properties of IGFs and the biochemical pathways by which these peptides regulate cell movement in both physiological and pathological conditions.