Role of fibroblast growth factor signaling in vascular formation and maintenance: orchestrating signaling networks as an integrated system

The effect of fibroblast growth factor 2 on neovascular vessels depends on the stage of angiogenesis

Objective

The exact relationship between fibroblast growth factor 2 (FGF2) and choroidal neovascularization (CNV) remains unclear. In this study, using optical coherence tomography angiography (OCTA) and FGF2-tg mice which are transgenic mice with a rhodopsin promoter/FGF2 gene fusion, we aimed to investigate the dynamics of FGF2's role in angiogenesis over time.

Methods

We developed laser-induced CNV models of FGF2-tg and wild-type (WT) mice and then separated them into two groups using different laser photocoagulation (PC) conditions. The first group received 3 intense PC shots (1st PC) altogether (one-time PC group), while the other group received 3 intense PC shots (1st PC) followed by 6 additional weak PC shots (2 nd PC) on the 7th day after 1st PC (two-times PC group).

Results

Using OCTA to observe vessel changes within the same individual over time, there was no difference in the timing of vessel transition from the CNV development phase to the CNV regression phase between FGF2-tg and WT mice in the one-time PC group. In contrast, the neovascular vessels in the two-times PC group of FGF2-tg mice were maintained at least 28 days post-2nd PC without regression. In addition, mature vessels surrounded by PDGFRβ positive pericytes and α-SMA positive smooth muscle cells were observed. Real-time qPCR showed a substantial increase in apelin mRNA expression in the one-time PC group of FGF2-tg, rather than VEGF-A (p < 0.05, n = 5 or 6). Moreover, the expression levels of PDGFRβ, apelin, and Ang1 were significantly higher in FGF2-tg mice of two-times PC group than in WT mice (p < 0.05, n = 5 or 6).

Conclusions

FGF2 not only promotes neovascularization via the apelin/APJ system, which is independent of VEGF signaling pathway, but also helps maintain and stabilize pre-existing neovascular vessels by stimulating PDGFRβ and Ang1. The effect of FGF2 on the neovascular vessels depends on the stage of angiogenesis.

Effectiveness of topical administration of platelet-rich plasma on the healing of methicillin-resistant Staphylococcus aureus-infected full-thickness wound model

This study aimed to investigate the wound-healing activity of animal platelet-rich plasma (PRP) in wounds infected with methicillin-resistant Staphylococcus aureus (MRSA) in rats. After wound induction, the rats were divided into three groups: noninfected animals treated with PRP (PRP group), MRSA-infected animals treated with mupirocin (standard control group), and MRSA-infected animals treated with PRP (MRSA+PRP group). Scratch assays, MTT test, and live/dead cells were also investigated. Total bacterial count, parameters of wound area, histopathological assessment, and expressions of IL-1β, TNF-α, iNOS, PDGF, FGF-2, and TGF-β mRNA levels and immunofluorescent staining of CD31 and collagen type 1 were assessed. The results showed that culture with PRP increased migration. PRP only showed cytotoxicity in a concentration of 100%. Topical application of PRP (50 µL) reduced the wound area and total bacterial count compared with the control group (P<0.05). The mRNA levels of IL-1β, TNF-α, and iNOS expression on days 7 and 14 (P<0.05) decreased in the treated groups compared with control rats. The mRNA levels of PDGF and TGF-β expression (P<0.05) increased in the treatment groups compared with control rats on days 3 and 7 (P<0.05). FGF-2 expression was significantly higher in the treated groups compared with the control group on days 7 and 14 (P<0.05). Moreover, positive expressions of macrophage colony-stimulating factor (M-CSF), CD31, collagen type 1 and cytokeratin proteins keratinocyte proliferation, and re-epithelization were significantly (P<0.05) increased in both PRP and MRSA+PRP-treated groups compared with the control groups on days 7 and 14. Topical administration of PRP accelerated the wound healing in MRSA-infected wound by decreasing the inflammation and improving the proliferative phase.

Bioactive scaffolds with enhanced supramolecular motion promote recovery from spinal cord injury

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Inhibition of FGF-FGFR and VEGF-VEGFR signalling in cancer treatment

The sites of targeted therapy are limited and need to be expanded. The FGF‐FGFR signalling plays pivotal roles in the oncogenic process, and FGF/FGFR inhibitors are a promising method to treat FGFR‐altered tumours. The VEGF‐VEGFR signalling is the most crucial pathway to induce angiogenesis, and inhibiting this cascade has already got success in treating tumours. While both their efficacy and antitumour spectrum are limited, combining FGF/FGFR inhibitors with VEGF/VEGFR inhibitors are an excellent way to optimize the curative effect and expand the antitumour range because their combination can target both tumour cells and the tumour microenvironment. In addition, biomarkers need to be developed to predict the efficacy, and combination with immune checkpoint inhibitors is a promising direction in the future. The article will discuss the FGF‐FGFR signalling pathway, the VEGF‐VEGFR signalling pathway, the rationale of combining these two signalling pathways and recent small‐molecule FGFR/VEGFR inhibitors based on clinical trials.

Knockdown of the KINDLIN-2 Gene and Reduced Expression of Kindlin-2 Affects Vascular Permeability in Angiogenesis in a Mouse Model of Wound Healing

Background

Angiogenesis is an important component of wound healing and tissue repair. Kindlin-2 is an integrin-associated protein, encoded by the KINDLIN-2 gene, which has been shown to affect cell adhesion and migration of cells, including endothelial cells. The aim of this study was to use a mouse model of wound healing to evaluate the effects of expression of KINDLIN-2 on angiogenesis in wound healing in vivo.

Material/Methods

Thirty-six male C57BL/6 mice were studied in an established model that used a wound created on the back. Mice were divided randomly into three groups: the normal group (n=12) received injections of normal (0.9%) saline; the KINDLIN-2(−) group (n=12) received injections of adeno-associated virus with small interfering (si)RNA targeting the KINDLIN-2 gene (AAV-KINDLIN-2-siRNA); and the control (group (n=12) received injections of adeno-associated virus containing a scrambled RNA sequence (AAV-control-RNA). Wound healing was analyzed by biochemical examination of the exudates and histology. Evans blue dye was injected into the caudal vein of each mouse, two weeks after wound healing to assess neovascular permeability.

Results

Wound healing was significantly delayed in the KINDLIN-2 gene knockdown mice (AAV-KINDLIN-2-siRNA) compared with that of the normal group and the control group, and neovascular permeability was increased. In the AAV-KINDLIN-2-siRNA group, blood vessels were shorter and thinner compared with the normal group and the control group.

Conclusions

In a mouse model of wound healing, KINDLIN-2 gene knockdown inhibited wound healing, and increased neovascular permeability in vivo.

Mimicking the Bioactivity of Fibroblast Growth Factor-2 Using Supramolecular Nanoribbons

Fibroblast growth factor (FGF-2) is a multifunctional growth factor that has pleiotropic effects in different tissues and organs. In particular, FGF-2 has a special role in angiogenesis, an important process in development, wound healing, cell survival, and differentiation. Therefore, incorporating biological agents like FGF-2 within therapeutic biomaterials is a potential strategy to create angiogenic bioactivity for the repair of damaged tissue caused by trauma or complications that arise from age and/or disease. However, the use of growth factors as therapeutic agents can be costly and does not always bring about efficient tissue repair due to rapid clearance from the targeted site. An alternative would be a stable supramolecular nanostructure with the capacity to activate the FGF-2 receptor that can also assemble into a scaffold deliverable to tissue. We report here on peptide amphiphiles that incorporate a peptide known to activate the FGF-2 receptor and peptide domains that drive its self-assembly into supramolecular nanoribbons. These FGF2-PA nanoribbons displayed the ability to increase the proliferation and migration of the human umbilical vein endothelial cells (HUVECs) in vitro to the same extent as the native FGF-2 protein at certain concentrations. We confirmed that this activity was specific to the FGFR1 signaling pathway by tracking the phosphorylation of downstream signaling effectors such ERK1/2 and pH3. These results indicated the specificity of FGF2-PA nanoribbons in activating the FGF-2 signaling pathway and its potential application as a supramolecular scaffold that can be used in vivo as an alternative to the encapsulation and delivery of the native FGF-2 protein.

An integrated approach to quantitative modelling in angiogenesis research

Angiogenesis, the process by which new vessels form from existing ones, plays an important role in many developmental processes and pathological conditions. We study angiogenesis in the context of a highly controllable experimental environment: the cornea micropocket assay. Using a multidisciplinary approach that combines experiments, image processing and analysis, and mathematical modelling, we aim to provide mechanistic insight into the action of two angiogenic factors, vascular endothelial growth factor A (VEGF-A) and basic fibroblast growth factor (bFGF). We use image analysis techniques to extract quantitative data, which are both spatially and temporally resolved, from experimental images, and we develop a mathematical model, in which the corneal vasculature evolves in response to both VEGF-A and bFGF. The experimental data are used for model parametrization, while the mathematical model is used to assess the utility of the cornea micropocket assay and to characterize proposed synergies between VEGF-A and bFGF.

Phenotype-dependent alteration of pathways and networks reveals a pure synergistic mechanism for compounds treating mouse cerebral ischemia

AIM

Our previous studies have showed that ursodeoxycholic acid (UA) and jasminoidin (JA) effectively reduce cerebral infarct volume in mice. In this study we explored the pure synergistic mechanism of these compounds in treatment of mouse cerebral ischemia, which was defined as synergistic actions specific for phenotype variations after excluding interference from ineffective compounds.

METHODS

Mice with focal cerebral ischemia were treated with UA, JA or a combination JA and UA (JU). Concha margaritifera (CM) was taken as ineffective compound. Cerebral infarct volume of the mice was determined, and the hippocampi were taken for microarray analysis. Particular signaling pathways and biological functions were enriched based on differentially expressed genes, and corresponding networks were constructed through Ingenuity Pathway Analysis.

RESULTS

In phenotype analysis, UA, JA, and JU significantly reduced the ischemic infarct volume with JU being superior to UA or JA alone, while CM was ineffective. As a result, 4 pathways enriched in CM were excluded. Core pathways in the phenotype-positive groups (UA or JA) were involved in neuronal homeostasis and neuropathology. JU-contributing pathways included all UA-contributing and the majority (71.7%) of JA-contributing pathways, and 10 new core pathways whose effects included inflammatory immunity, apoptosis and nervous system development. The functions of JU group included all functions of JA group, the majority (93.1%) of UA-contributing functions, and 3 new core functions, which focused on physiological system development and function.

CONCLUSION

The pure synergism between UA and JA underlies 10 new core pathways and 3 new core functions, which are involved in inflammation, immune responses, apoptosis and nervous system development.

Endothelial cell FGF signaling is required for injury response but not for vascular homeostasis

Endothelial cells (ECs) express fibroblast growth factor receptors (FGFRs) and are exquisitely sensitive to FGF signals. However, whether the EC or another vascular cell type requires FGF signaling during development, homeostasis, and response to injury is not known. Here, we show that Flk1-Cre or Tie2-Cre mediated deletion of FGFR1 and FGFR2 (Fgfr1/2(Flk1-Cre) or Fgfr1/2(Tie2-Cre) mice), which results in deletion in endothelial and hematopoietic cells, is compatible with normal embryonic development. As adults, Fgfr1/2(Flk1-Cre) mice maintain normal blood pressure and vascular reactivity and integrity under homeostatic conditions. However, neovascularization after skin or eye injury was significantly impaired in both Fgfr1/2(Flk1-Cre) and Fgfr1/2(Tie2-Cre) mice, independent of either hematopoietic cell loss of FGFR1/2 or vascular endothelial growth factor receptor 2 (Vegfr2) haploinsufficiency. Also, impaired neovascularization was associated with delayed cutaneous wound healing. These findings reveal a key requirement for cell-autonomous EC FGFR signaling in injury-induced angiogenesis, but not for vascular homeostasis, identifying the EC FGFR signaling pathway as a target for diseases associated with aberrant vascular proliferation, such as age-related macular degeneration, and for modulating wound healing without the potential toxicity associated with direct manipulation of systemic FGF or VEGF activity.