Use of the mouse aortic ring assay to study angiogenesis

Smad3 promotes adverse cardiovascular remodeling and dysfunction in doxorubicin-treated hearts

Many anticancer therapies cause serious cardiovascular complications that degrade quality of life and cause early mortality in treated patients. Specifically, doxorubicin is known as an effective anticancer agent that causes cardiomyopathy in treated patients. There has been growing interest in defining the role of endothelial cells in cardiac damage by doxorubicin. We have shown in the present study that endothelial nuclei accumulate more intravenously administered doxorubicin than other cardiac cell types. Doxorubicin enhanced cardiac production of the transforming growth factor-β (TGF-β) ligands and nuclear translocation of phospho-Smad3 in both cultured and in vivo cardiac endothelial cells. To examine the role of the TGF-β/mothers against decapentaplegic homolog 3 (Smad3) pathway in cardiac damage by doxorubicin, we used both Smad3 shRNA stable endothelial cell lines and Smad3-knockout mice. We demonstrated using endothelial transcriptome analysis that upregulation of the TGF-β and inflammatory cytokine/cytokine receptor pathways, as well as suppression of cell cycle and angiogenesis by doxorubicin, were alleviated in Smad3-deficient endothelial cells. The results of transcriptomic analysis were validated using qPCR, immunoblotting, and ex vivo aortic ring sprouting assays. Similarly, increased cardiac expression of cytokines and chemokines observed in treated wild-type mice was diminished in treated Smad3-knockout animals. We also detected increased end-diastolic diameter and depressed systolic function in doxorubicin-treated wild-type but not Smad3-knockout mice. This work provides evidence for the critical role of the canonical TGF-β/Smad3 pathway in cardiac damage by doxorubicin.NEW & NOTEWORTHY Microvascular endothelial cells in the heart accumulate more intravenously administered doxorubicin than nonendothelial cardiac cell types. The treatment enhanced the TGF-β/Smad3 pathway and elicited endothelial cell senescence and inflammatory responses followed by adverse cardiac remodeling and dysfunction in wild-type but not Smad3-deficient animals. Our study suggests that the TGF-β/Smad3 pathway contributes to the development of doxorubicin cardiomyopathy and the potential value of novel approaches to ameliorate cardiotoxicity by targeting the Smad3 transcription factor.

Remarkable consistency of spinal cord microvasculature in highly adapted diving odontocetes

Odontocetes are breath-hold divers with a suite of physiological, anatomical, and behavioral adaptations that are highly derived and vastly different from those of their terrestrial counterparts. Because of these adaptations for diving, odontocetes were originally thought to be exempt from the harms of nitrogen gas embolism while diving. However, recent studies have shown that these mammals may alter their dive behavior in response to anthropogenic sound, leading to the potential for nitrogen supersaturation and bubble formation which may cause decompression sickness in the central nervous system (CNS). We examined the degree of interface between blood, gases, and neural tissues in the spinal cord by quantifying its microvascular characteristics in five species of odontocetes (Tursiops truncatus, Delphinus delphis, Grampus griseus, Kogia breviceps, and Mesoplodon europaeus) and a model terrestrial species (the pig-Sus scrofa domesticus) for comparison. This approach allowed us to compare microvascular characteristics (microvascular density, branching, and diameter) at several positions (cervical, thoracic, and lumbar) along the spinal cord from odontocetes that are known to be either deep or shallow divers. We found no significant differences (p < 0.05 for all comparisons) in microvessel density (9.30-11.18%), microvessel branching (1.60-2.12 branches/vessel), or microvessel diameter (11.83-16.079 µm) between odontocetes and the pig, or between deep and shallow diving odontocete species. This similarity of spinal cord microvasculature anatomy in several species of odontocetes as compared to the terrestrial mammal is in contrast to the wide array of remarkable physio-anatomical adaptations marine mammals have evolved within their circulatory system to cope with the physiological demands of diving. These results, and other studies on CNS lipids, indicate that the spinal cords of odontocetes do not have specialized features that might serve to protect them from Type II DCS.

Intrapericardial cardiosphere-derived cells hinder epicardial dense scar expansion and promote electrical homogeneity in a porcine post-infarction model

The arrhythmic substrate of ventricular tachycardias in many structural heart diseases is located in the epicardium, often resulting in poor outcomes with currently available therapies. Cardiosphere-derived cells (CDCs) have been shown to modify myocardial scarring. A total of 19 Large White pigs were infarcted by occlusion of the mid-left anterior descending coronary artery for 150 min. Baseline cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement sequences was obtained 4 weeks post-infarction and pigs were randomized to a treatment group (intrapericardial administration of 300,000 allogeneic CDCs/kg), (n = 10) and to a control group (n = 9). A second CMR and high-density endocardial electroanatomical mapping were performed at 16 weeks post-infarction. After the electrophysiological study, pigs were sacrificed and epicardial optical mapping and histological studies of the heterogeneous tissue of the endocardial and epicardial scars were performed. In comparison with control conditions, intrapericardial CDCs reduced the growth of epicardial dense scar and epicardial electrical heterogeneity. The relative differences in conduction velocity and action potential duration between healthy myocardium and heterogeneous tissue were significantly smaller in the CDC-treated group than in the control group. The lower electrical heterogeneity coincides with heterogeneous tissue with less fibrosis, better cardiomyocyte viability, and a greater quantity and better polarity of connexin 43. At the endocardial level, no differences were detected between groups. Intrapericardial CDCs produce anatomical and functional changes in the epicardial arrhythmic substrate, which could have an anti-arrhythmic effect.

Anti-PTK7 Monoclonal Antibodies Inhibit Angiogenesis by Suppressing PTK7 Function

Simple Summary

PTK7 is a catalytically defective receptor protein tyrosine kinase. We previously demonstrated that PTK7 enhances angiogenesis by interacting with KDR, a vascular endothelial growth factor (VEGF) receptor important for angiogenesis, and activating it through oligomerization. To control angiogenesis by inhibiting PTK7 function, we developed anti-PTK7 monoclonal antibodies (mAbs). The selected PTK7 mAbs reduced VEGF-induced angiogenic phenotypes of endothelial cells and angiogenesis ex vivo and in vivo. The PTK7 mAbs also inhibited VEGF-induced KDR activation in endothelial cells and its downstream signaling and PTK7–KDR interaction. Our results show that the PTK7 mAbs inhibit angiogenesis by blocking PTK7 function. Therefore, PTK7 mAbs could be applied as therapeutics to control angiogenesis-associated diseases such as metastatic cancers.

Abstract

PTK7, a catalytically defective receptor protein tyrosine kinase, promotes angiogenesis by activating KDR through direct interaction and induction of KDR oligomerization. This study developed anti-PTK7 monoclonal antibodies (mAbs) to regulate angiogenesis by inhibiting PTK7 function. The effect of anti-PTK7 mAbs on vascular endothelial growth factor (VEGF)-induced angiogenic phenotypes in human umbilical vascular endothelial cells (HUVECs) was examined. Analysis of mAb binding with PTK7 deletion mutants revealed that mAb-43 and mAb-52 recognize immunoglobulin (Ig) domain 2 of PTK7, whereas mAb-32 and mAb-50 recognize Ig domains 6–7. Anti-PTK7 mAbs inhibited VEGF-induced adhesion and wound healing in HUVECs. mAb-32, mAb-43, and mAb-52 dose-dependently mitigated VEGF-induced migration and invasion in HUVECs without exerting cytotoxic effects. Additionally, mAb-32, mAb-43, and mAb-52 inhibited capillary-like tube formation in HUVECs, and mAb-32 and mAb-43 suppressed angiogenesis ex vivo (aortic ring assay) and in vivo (Matrigel plug assay). Furthermore, mAb-32 and mAb-43 downregulated VEGF-induced KDR activation and downstream signaling and inhibited PTK7–KDR interaction in PTK7-overexpressing and KDR-overexpressing HEK293 cells. Thus, anti-PTK7 mAbs inhibit angiogenic phenotypes by blocking PTK7–KDR interaction. These findings indicate that anti-PTK7 mAbs that neutralize PTK7 function can alleviate impaired angiogenesis-associated pathological conditions, such as cancer metastasis.

Stearoyl-CoA Desaturase Regulates Angiogenesis and Energy Metabolism in Ischemic Cardiomyocytes

New blood vessel formation is a key component of the cardiac repair process after myocardial infarction (MI). Hypoxia following MI is a major driver of angiogenesis in the myocardium. Hypoxia-inducible factor 1α (HIF1α) is the key regulator of proangiogenic signaling. The present study found that stearoyl-CoA desaturase (SCD) significantly contributed to the induction of angiogenesis in the hypoxic myocardium independently of HIF1α expression. The pharmacological inhibition of SCD activity in HL-1 cardiomyocytes and SCD knockout in an animal model disturbed the expression and secretion of proangiogenic factors including vascular endothelial growth factor-A, proinflammatory cytokines (interleukin-1β, interleukin-6, tumor necrosis factor α, monocyte chemoattractant protein-1, and Rantes), metalloproteinase-9, and platelet-derived growth factor in ischemic cardiomyocytes. These disturbances affected the proangiogenic potential of ischemic cardiomyocytes after SCD depletion. Together with the most abundant SCD1 isoform, the heart-specific SCD4 isoform emerged as an important regulator of new blood vessel formation in the murine post-MI myocardium. We also provide evidence that SCD shapes energy metabolism of the ischemic heart by maintaining the shift from fatty acids to glucose as the substrate that is used for adenosine triphosphate production. Furthermore, we propose that the regulation of the proangiogenic properties of hypoxic cardiomyocytes by key modulators of metabolic signaling such as adenosine monophosphate kinase, protein kinase B (AKT), and peroxisome-proliferator-activated receptor-γ coactivator 1α/peroxisome proliferator-activated receptor α depends on SCD to some extent. Thus, our results reveal a novel mechanism that links SCD to cardiac repair processes after MI.

Celastrol inhibits laser-induced choroidal neovascularization by decreasing VEGF induced proliferation and migration

AIM

To evaluate celastrol's effect on choroidal neovascularization (CNV).

METHODS

In this study, neovascular formation in vitro (tube formation and aortic ring culture) and in vivo (laser induced neovascular in mice) was treated with celastrol to evaluate this natural compound's impact on CNV. Western blot was applied to explore the possible mechanism for it. For in vitro assay, triplicate for each group was repeated at least three times. For in vivo assay, each group contains 5 mice.

RESULTS

Celastrol supressed tube formation and aortic ring sprout neovascularization. In vitro assay exhibited that celastrol inhibiting vascular endothelial growth factor (VEGF)-induced proliferation and migration of human umbilical vein endothelial cells and human choroidal endothelial cells, and by blocking VEGF signaling. Furthermore, intraperitoneal administration of celastrol significantly reduced the area of laser-induced CNV in an in vivo mouse model. By day 14, the area of CNV had decreased by 49.15% and 80.26% in the 0.1 mg/kg celastrol-treated group (n=5) and in the 0.5 mg/kg celastrol treated group (n=5), respectively, compared to the vehicle-treated group (n=5).

CONCLUSION

Celastrol inhibits CNV by inhibiting VEGF-induced proliferation and migration of vascular endothelial cells, indicating that celastrol is a potent, natural therapeutic compound for the prevention of CNV.

Effects of lifelong spontaneous exercise on skeletal muscle and angiogenesis in super-aged mice

There has been an increasing awareness of sarcopenia, which is characterized by a concomitant decrease in skeletal muscle mass and quality due to aging. Resistance exercise is considered more effective than aerobic exercise in terms of therapeutic exercise. To confirm the effect of long-term aerobic exercise in preventing sarcopenia, we evaluated the skeletal muscle mass, quality, and angiogenic capacity of super-aged mice that had undergone lifelong spontaneous exercise (LSE) through various experiments. Our findings show that LSE could maintain skeletal muscle mass, quality, and fitness levels in super-aged mice. In addition, ex vivo experiments showed that the angiogenic capacity was maintained at a high level. However, these results were not consistent with the related changes in the expression of genes and/or proteins involved in protein synthesis or angiogenesis. Based on the results of previous studies, it seems certain that the expression at the molecular level does not represent the phenotypes of skeletal muscle and angiogenesis. This is because aging and long-term exercise are variables that can affect both protein synthesis and the expression patterns of angiogenesis-related genes and proteins. Therefore, in aging and exercise-related research, various physical fitness and angiogenesis variables and phenotypes should be analyzed. In conclusion, LSE appears to maintain the potential of angiogenesis and slow the aging process to maintain skeletal muscle mass and quality. Aerobic exercise may thus be effective for the prevention of sarcopenia.

Comparison of mechanisms of angiostasis caused by the anti-inflammatory steroid 5α-tetrahydrocorticosterone versus conventional glucocorticoids

5α-Tetrahydrocorticosterone (5αTHB) is an effective topical anti-inflammatory agent in mouse, with less propensity to cause skin thinning and impede new blood vessel growth compared with corticosterone. Its anti-inflammatory effects were not prevented by RU38486, a glucocorticoid receptor antagonist, suggesting alternative mechanisms. The hypothesis that 5αTHB directly inhibits angiogenesis to a lesser extent than hydrocortisone was tested, focussing on glucocorticoid receptor mediated actions. New vessel growth from aortae from C57BL/6 male mice was monitored in culture, in the presence of 5αTHB, hydrocortisone (mixed glucocorticoid/mineralocorticoid receptor agonist) or the selective glucocorticoid receptor agonist dexamethasone. Transcript profiles were studied, as was the role of the glucocorticoid receptor, using the antagonist, RU38486. Ex vivo, 5αTHB suppressed vessel growth from aortic rings, but was less potent than hydrocortisone (EC50 2512 nM 5αTHB, versus 762 nM hydrocortisone). In contrast to conventional glucocorticoids, 5αTHB did not alter expression of genes related to extracellular matrix integrity or inflammatory signalling, but caused a small increase in Per1 transcript, and decreased transcript abundance of Pecam1 gene. RU38486 did not antagonise the residual effects of 5αTHB to suppress vessel growth or regulate gene expression, but modified effects of dexamethasone. 5αTHB did not alter expression of glucocorticoid-regulated genes Fkbp51 and Hsd11b1, unlike hydrocortisone and dexamethasone. In conclusion, compared with hydrocortisone, 5αTHB exhibits limited suppression of angiogenesis, at least directly in blood vessels and probably independent of the glucocorticoid receptor. Discriminating the mechanisms employed by 5αTHB may provide the basis for the development of novel safer anti-inflammatory drugs for topical use.

Hypoxia‐induced ELF3 promotes tumor angiogenesis through IGF1/IGF1R

Epithelial ovarian cancer (EOC) is one of the most lethal gynecological cancers despite a relatively low incidence. Angiogenesis, one of the hallmarks of cancer, is essential for the pathogenesis of EOC, which is related to the induction of angiogenic factors. We found that ELF3 was highly expressed in EOCs under hypoxia and functioned as a transcription factor for IGF1. The ELF3‐mediated increase in the secretion of IGF1 and VEGF promoted endothelial cell proliferation, migration, and EOC angiogenesis. Although this situation was much exaggerated under hypoxia, ELF3 silencing under hypoxia significantly attenuated angiogenic activity in endothelial cells by reducing the expression and secretion of IGF1 and VEGF. ELF3 silencing attenuated angiogenesis and tumorigenesis in ex vivo and xenograft mouse models. Consequently, ELF3 plays an important role in the induction of angiogenesis and tumorigenesis in EOC as a transcription factor of IGF1. A detailed understanding of the biological mechanism of ELF3 may both improve current antiangiogenic therapies and have anticancer effects for EOC.

Aldehyde dehydrogenase 2 augments adiponectin signaling in coronary angiogenesis in HFpEF associated with diabetes

4-hydroxy-2-nonenal (4HNE), an oxidative stress byproduct, is elevated in diabetes which decreases coronary angiogenesis, and this was rescued by the 4HNE detoxifying enzyme, aldehyde dehydrogenase 2 (ALDH2). Adiponectin (APN), an adipocytokine, has pro-angiogenic properties and its loss of function is critical in diabetes and its complications. Coronary endothelial cell (CEC) damage is the initiating step of diabetes-mediated heart failure with preserved ejection fraction (HFpEF) pathogenesis. Thus, we hypothesize that ALDH2 restores 4HNE-induced downregulation of APN signaling in CECs and subsequent coronary angiogenesis in diabetic HFpEF. Treatment with disulfiram, an ALDH2 inhibitor, exacerbated 4HNE-mediated decreases in APN-induced increased coronary angiogenesis and APN-signaling cascades, whereas pretreatment with alda1, an ALDH2 activator, rescued the effect of 4HNE. We employed control mice (db/m), spontaneous type-2 diabetic mice (db/db), ALDH2*2 knock-in mutant mice with intrinsic low ALDH2 activity (AL), and diabetic mice with intrinsic low ALDH2 activity (AF) mice that were created by crossing db/db and AL mice to test our hypothesis in vivo. AF mice exhibited heart failure with preserved ejection fraction (HFpEF)/severe diastolic dysfunction at 6 months with a preserved systolic function compared with db/db mice as well as 3 months of their age. Decreased APN-mediated coronary angiogenesis, along with increased circulatory APN levels and decreased cardiac APN signaling (index of APN resistance) were higher in AF mice relative to db/db mice. Alda1 treatment improved APN-mediated angiogenesis in AF and db/db mice. In summary, 4HNE-induces APN resistance and a subsequent decrease in coronary angiogenesis in diabetic mouse heart which was rescued by ALDH2.

Exercise promotes angiogenesis by enhancing endothelial cell fatty acid utilization via liver-derived extracellular vesicle miR-122-5p

BACKGROUND

Angiogenesis constitutes a major mechanism responsible for exercise-induced beneficial effects. Our previous study identified a cluster of differentially expressed extracellular vesicle microRNAs (miRNAs) after exercise and found that some of them act as exerkines. However, whether these extracellular vesicle miRNAs mediate the exercise-induced angiogenesis remains unknown.

METHODS

A 9-day treadmill training was used as an exercise model in C57BL/6 mice. Liver-specific adeno-associated virus 8 was used to knock down microRNA-122-5p (miR-122-5p). Human umbilical vein endothelial cells were used in vitro.

RESULTS

Among these differentially expressed extracellular vesicle miRNAs, miR-122-5p was identified as a potent pro-angiogenic factor that activated vascular endothelial growth factor signaling and promoted angiogenesis both in vivo and in vitro. Exercise increased circulating levels of miR-122-5p, which was produced mainly by the liver and shuttled by extracellular vesicles in mice. Inhibition of circulating miR-122-5p or liver-specific knockdown of miR-122-5p significantly abolished the exercise-induced pro-angiogenic effect in skeletal muscles, and exercise-improved muscle performance in mice. Mechanistically, miR-122-5p promoted angiogenesis through shifting substrate preference to fatty acids in endothelial cells, and miR-122-5p upregulated endothelial cell fatty-acid utilization by targeting 1-acyl-sn-glycerol-3-phosphate acyltransferase (AGPAT1). In addition, miR-122-5p increased capillary density in perilesional skin tissues and accelerated wound healing in mice.

CONCLUSION

These findings demonstrated that exercise promotes angiogenesis through upregulation of liver-derived extracellular vesicle miR-122-5p, which enhances fatty acid utilization by targeting AGPAT1 in endothelial cells, highlighting the therapeutic potential of miR-122-5p in tissue repair.

IL-10 promotes endothelial progenitor cell infiltration and wound healing via STAT3

Endothelial progenitor cells (EPCs) contribute to de novo angiogenesis, tissue regeneration, and remodeling. Interleukin 10 (IL-10), an anti-inflammatory cytokine that primarily signals via STAT3, has been shown to drive EPC recruitment to injured tissues. Our previous work demonstrated that overexpression of IL-10 in dermal wounds promotes regenerative tissue repair via STAT3-dependent regulation of fibroblast-specific hyaluronan synthesis. However, IL-10's role and specific mode of action on EPC recruitment, particularly in dermal wound healing and neovascularization in both normal and diabetic wounds, remain to be defined. Therefore, inducible skin-specific STAT3 knockdown mice were studied to determine IL-10's impact on EPCs, dermal wound neovascularization and healing, and whether it is STAT3-dependent. We show that IL-10 overexpression significantly elevated EPC counts in the granulating wound bed, which was associated with robust capillary lumen density and enhanced re-epithelialization of both control and diabetic (db/db) wounds at day 7. We noted increased VEGF and high C-X-C motif chemokine 12 (CXCL12) levels in wounds and a favorable CXCL12 gradient at day 3 that may support EPC mobilization and infiltration from bone marrow to wounds, an effect that was abrogated in STAT3 knockdown wounds. These findings were supported in vitro. IL-10 promoted VEGF and CXCL12 synthesis in primary murine dermal fibroblasts, with blunted VEGF expression upon blocking CXCL12 in the media by antibody binding. IL-10-conditioned fibroblast media also significantly promoted endothelial sprouting and network formation. In conclusion, these studies demonstrate that overexpression of IL-10 in dermal wounds recruits EPCs and leads to increased vascular structures and faster re-epithelialization.

Glycation of Tie-2 Inhibits Angiopoietin-1 Signaling Activation and Angiopoietin-1-Induced Angiogenesis

The impairment of the angiopoietin-1 (Ang-1)/Tie-2 signaling pathway has been thought to play a critical role in diabetic complications. However, the underlying mechanisms remain unclear. The present study aims to investigate the effects of Tie-2 glycation on Ang-1 signaling activation and Ang-1-induced angiogenesis. We identified that Tie-2 was modified by advanced glycation end products (AGEs) in aortae derived from high fat diet (HFD)-fed mice and in methylglyoxal (MGO)-treated human umbilical vein endothelial cells (HUVECs). MGO-induced Tie-2 glycation significantly inhibited Ang-1-evoked Tie-2 and Akt phosphorylation and Ang-1-regulated endothelial cell migration and tube formation, whereas the blockade of AGE formation by aminoguanidine remarkably rescued Ang-1 signaling activation and Ang-1-induced angiogenesis in vitro. Furthermore, MGO treatment markedly increased AGE cross-linking of Tie-2 in cultured aortae ex vivo and MGO-induced Tie-2 glycation also significantly decreased Ang-1-induced vessel outgrow from aortic rings. Collectively, these data suggest that Tie-2 may be modified by AGEs in diabetes mellitus and that Tie-2 glycation inhibits Ang-1 signaling activation and Ang-1-induced angiogenesis. This may provide a novel mechanism for Ang-1/Tie-2 signal dysfunction and angiogenesis failure in diabetic ischaemic diseases.

EPCR-PAR1 biased signaling regulates perfusion recovery and neovascularization in peripheral ischemia

Blood clot formation initiates ischemic events, but coagulation roles during postischemic tissue repair are poorly understood. The endothelial protein C receptor (EPCR) regulates coagulation, as well as immune and vascular signaling, by protease activated receptors (PARs). Here, we show that endothelial EPCR-PAR1 signaling supports reperfusion and neovascularization in hindlimb ischemia in mice. Whereas deletion of PAR2 or PAR4 did not impair angiogenesis, EPCR and PAR1 deficiency or PAR1 resistance to cleavage by activated protein C caused markedly reduced postischemic reperfusion in vivo and angiogenesis in vitro. These findings were corroborated by biased PAR1 agonism in isolated primary endothelial cells. Loss of EPCR-PAR1 signaling upregulated hemoglobin expression and reduced endothelial nitric oxide (NO) bioavailability. Defective angiogenic sprouting was rescued by the NO donor DETA-NO, whereas NO scavenging increased hemoglobin and mesenchymal marker expression in human and mouse endothelial cells. Vascular specimens from patients with ischemic peripheral artery disease exhibited increased hemoglobin expression, and soluble EPCR and NO levels were reduced in plasma. Our data implicate endothelial EPCR-PAR1 signaling in the hypoxic response of endothelial cells and identify suppression of hemoglobin expression as an unexpected link between coagulation signaling, preservation of endothelial cell NO bioavailability, support of neovascularization, and prevention of fibrosis.

Gatekeeping role of Nf2/Merlin in vascular tip EC induction through suppression of VEGFR2 internalization

In sprouting angiogenesis, the precise mechanisms underlying how intracellular vascular endothelial growth factor receptor 2 (VEGFR2) signaling is higher in one endothelial cell (EC) compared with its neighbor and acquires the tip EC phenotype under a similar external cue are elusive. Here, we show that Merlin, encoded by the neurofibromatosis type 2 (NF2) gene, suppresses VEGFR2 internalization depending on VE-cadherin density and inhibits tip EC induction. Accordingly, endothelial Nf2 depletion promotes tip EC induction with excessive filopodia by enhancing VEGFR2 internalization in both the growing and matured vessels. Mechanistically, Merlin binds to the VEGFR2-VE-cadherin complex at cell-cell junctions and reduces VEGFR2 internalization-induced downstream signaling during tip EC induction. As a consequence, nonfunctional excessive sprouting occurs during tumor angiogenesis in EC-specific Nf2-deleted mice, leading to delayed tumor growth. Together, Nf2/Merlin is a crucial molecular gatekeeper for tip EC induction, capillary integrity, and proper tumor angiogenesis by suppressing VEGFR2 internalization.

Endothelial PRMT5 plays a crucial role in angiogenesis after acute ischemic injury

Arginine methylation mediated by protein arginine methyltransferases (PRMTs) has been shown to be an important posttranslational mechanism involved in various biological processes. Herein, we sought to investigate whether PRMT5, a major type II enzyme, is involved in pathological angiogenesis and, if so, to elucidate the molecular mechanism involved. Our results show that PRMT5 expression is significantly upregulated in ischemic tissues and hypoxic endothelial cells (ECs). Endothelial-specific Prmt5-KO mice were generated to define the role of PRMT5 in hindlimb ischemia-induced angiogenesis. We found that these mice exhibited impaired recovery of blood perfusion and motor function of the lower limbs, an impairment that was accompanied by decreased vascular density and increased necrosis as compared with their WT littermates. Furthermore, both pharmacological and genetic inhibition of PRMT5 significantly attenuated EC proliferation, migration, tube formation, and aortic ring sprouting. Mechanistically, we showed that inhibition of PRMT5 markedly attenuated hypoxia-induced factor 1-α (HIF-1α) protein stability and vascular endothelial growth factor-induced (VEGF-induced) signaling pathways in ECs. Our results provide compelling evidence demonstrating a crucial role of PRMT5 in hypoxia-induced angiogenesis and suggest that inhibition of PRMT5 may provide novel therapeutic strategies for the treatment of abnormal angiogenesis-related diseases, such as cancer and diabetic retinopathy.

Bone marrow-independent adventitial macrophage progenitor cells contribute to angiogenesis

Pathological angiogenesis promotes tumor growth, metastasis, and atherosclerotic plaque rupture. Macrophages are key players in these processes. However, whether these macrophages differentiate from bone marrow-derived monocytes or from local vascular wall-resident stem and progenitor cells (VW-SCs) is an unresolved issue of angiogenesis. To answer this question, we analyzed vascular sprouting and alterations in aortic cell populations in mouse aortic ring assays (ARA). ARA culture leads to the generation of large numbers of macrophages, especially within the aortic adventitia. Using immunohistochemical fate-mapping and genetic in vivo-labeling approaches we show that 60% of these macrophages differentiate from bone marrow-independent Ly6c⁺/Sca-1⁺ adventitial progenitor cells. Analysis of the NCX^−/− mouse model that genetically lacks embryonic circulation and yolk sac perfusion indicates that at least some of those progenitor cells arise yolk sac-independent. Macrophages represent the main source of VEGF in ARA that vice versa promotes the generation of additional macrophages thereby creating a pro-angiogenetic feedforward loop. Additionally, macrophage-derived VEGF activates CD34⁺ progenitor cells within the adventitial vasculogenic zone to differentiate into CD31⁺ endothelial cells. Consequently, depletion of macrophages and VEGFR2 antagonism drastically reduce vascular sprouting activity in ARA. In summary, we show that angiogenic activation induces differentiation of macrophages from bone marrow-derived as well as from bone marrow-independent VW-SCs. The latter ones are at least partially yolk sac-independent, too. Those VW-SC-derived macrophages critically contribute to angiogenesis, making them an attractive target to interfere with pathological angiogenesis in cancer and atherosclerosis as well as with regenerative angiogenesis in ischemic cardiovascular disorders.

Activation of the GPR35 pathway drives angiogenesis in the tumour microenvironment

OBJECTIVE

Primary sclerosing cholangitis (PSC) is in 70% of cases associated with inflammatory bowel disease. The hypermorphic T108M variant of the orphan G protein-coupled receptor GPR35 increases risk for PSC and ulcerative colitis (UC), conditions strongly predisposing for inflammation-associated liver and colon cancer. Lack of GPR35 reduces tumour numbers in mouse models of spontaneous and colitis associated cancer. The tumour microenvironment substantially determines tumour growth, and tumour-associated macrophages are crucial for neovascularisation. We aim to understand the role of the GPR35 pathway in the tumour microenvironment of spontaneous and colitis-associated colon cancers.

DESIGN

Mice lacking GPR35 on their macrophages underwent models of spontaneous colon cancer or colitis-associated cancer. The role of tumour-associated macrophages was then assessed in biochemical and functional assays.

RESULTS

Here, we show that GPR35 on macrophages is a potent amplifier of tumour growth by stimulating neoangiogenesis and tumour tissue remodelling. Deletion of Gpr35 in macrophages profoundly reduces tumour growth in inflammation-associated and spontaneous tumour models caused by mutant tumour suppressor adenomatous polyposis coli. Neoangiogenesis and matrix metalloproteinase activity is promoted by GPR35 via Na/K-ATPase-dependent ion pumping and Src activation, and is selectively inhibited by a GPR35-specific pepducin. Supernatants from human inducible-pluripotent-stem-cell derived macrophages carrying the UC and PSC risk variant stimulate tube formation by enhancing the release of angiogenic factors.

CONCLUSIONS

Activation of the GPR35 pathway promotes tumour growth via two separate routes, by directly augmenting proliferation in epithelial cells that express the receptor, and by coordinating macrophages' ability to create a tumour-permissive environment.

Ginger Constituent 6-Shogaol Inhibits Inflammation- and Angiogenesis-Related Cell Functions in Primary Human Endothelial Cells

Rhizomes from Zingiber officinale Roscoe are traditionally used for the treatment of a plethora of pathophysiological conditions such as diarrhea, nausea, or rheumatoid arthritis. While 6-gingerol is the pungent principle in fresh ginger, in dried rhizomes, 6-gingerol is dehydrated to 6-shogaol. 6-Shogaol has been demonstrated to exhibit anticancer, antioxidative, and anti-inflammatory actions more effectively than 6-gingerol due to the presence of an electrophilic Michael acceptor moiety. In vitro, 6-shogaol exhibits anti-inflammatory actions in a variety of cell types, including leukocytes. Our study focused on the effects of 6-shogaol on activated endothelial cells. We found that 6-shogaol significantly reduced the adhesion of leukocytes onto lipopolysaccharide (LPS)-activated human umbilical vein endothelial cells (HUVECs), resulting in a significantly reduced transmigration of THP-1 cells through an endothelial cell monolayer. Analyzing the mediators of endothelial cell–leukocyte interactions, we found that 30 µM of 6-shogaol blocked the LPS-triggered mRNA and protein expression of cell adhesion molecules. In concert with this, our study demonstrates that the LPS-induced nuclear factor κB (NFκB) promoter activity was significantly reduced upon treatment with 6-shogaol. Interestingly, the nuclear translocation of p65 was slightly decreased, and protein levels of the LPS receptor Toll-like receptor 4 remained unimpaired. Analyzing the impact of 6-shogaol on angiogenesis-related cell functions in vitro, we found that 6-shogaol attenuated the proliferation as well as the directed and undirected migration of HUVECs. Of note, 6-shogaol also strongly reduced the chemotactic migration of endothelial cells in the direction of a serum gradient. Moreover, 30 µM of 6-shogaol blocked the formation of vascular endothelial growth factor (VEGF)-induced endothelial sprouts from HUVEC spheroids and from murine aortic rings. Importantly, this study shows for the first time that 6-shogaol exhibits a vascular-disruptive impact on angiogenic sprouts from murine aortae. Our study demonstrates that the main bioactive ingredient in dried ginger, 6-shogaol, exhibits beneficial characteristics as an inhibitor of inflammation- and angiogenesis-related processes in vascular endothelial cells.

DIX domain containing 1 (DIXDC1) modulates VEGFR2 level in vasculatures to regulate embryonic and postnatal retina angiogenesis

Background

In sprouting angiogenesis, VEGFR2 level is regulated via a fine-tuned process involving various signaling pathways. Other than VEGF/VEGFR2 signaling pathway, Wnt/ β-catenin signaling is also important in vascular development. However, the crosstalk between these two signaling pathways is still unknown to date. In this study, we aimed to investigate the role of DIX domain containing 1 (DIXDC1) in vasculature, facilitating the crosstalk between VEGF/VEGFR2 and Wnt/ β-catenin signaling pathways.

Results

In mice, DIXDC1 deficiency delayed angiogenesis at the embryonic stage and suppressed neovascularization at the neonatal stage. DIXDC1 knockdown inhibited VEGF-induced angiogenesis in endothelial cells in vitro by downregulating VEGFR2 expression. DIXDC1 bound Dishevelled Segment Polarity Protein 2 (Dvl2) and polymerized Dvl2 stabilizing VEGFR2 protein via its direct interaction. The complex formation and stability of VEGFR2 was potentiated by Wnt signaling. Moreover, hypoxia elevated DIXDC1 expression and likely modulated both canonical Wnt/β-catenin signaling and VEGFR2 stability in vasculatures. Pathological angiogenesis in DIXDC1 knockout mice was decreased significantly in oxygen-induced retinopathy (OIR) and in wound healing models. These results suggest that DIXDC1 is an important factor in developmental and pathological angiogenesis.

Conclusion

We have identified DIXDC1 as an important factor in early vascular development. These results suggest that DIXDC1 represents a novel regulator of sprouting angiogenesis that links Wnt signaling and VEGFR2 stability and may have a potential role in pathological neovascularization.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01240-3.

A New Approach to Inhibiting Triple-Negative Breast Cancer: In Vitro, Ex Vivo and In Vivo Antiangiogenic Effect of BthTx-II, a PLA2-Asp-49 from Bothrops jararacussu Venom

Phospholipases A2 (PLA2) represent a superfamily of enzymes widely distributed in living organisms, with a broad spectrum of pharmacological activities and therapeutic potential. Anti-angiogenic strategies have become one of the main tools in fighting cancer. In this sense, the present work reports the inhibition of tumor angiogenesis induced by Asp-49 BthTX-II using in vitro, ex vivo and in vivo approaches. We demonstrate that BthTx-II inhibited cell adhesion, proliferation, and migration of human umbilical vein endothelial cells (HUVEC), as well as caused a reduction in the levels of endothelial growth factor (VEGF) during in vitro angiogenesis assays. BthTx-II was also able to inhibit the sprouting angiogenic process, by the ex vivo germination assay of the aortic ring; in addition, this toxin inhibited the migration and proliferation of HUVEC in co-culture with triple-negative breast cancer cells (e.g., MDA-MB-231 cells). Finally, in vivo tumor suppression and anti-angiogenic activities were analyzed using MDA-MB-231 cells with Matrigel injected into the chorioallantoic membrane of chicken embryo (CAM) for 7 days treatment with BthTx-II, showing a considerable reduction in vessel caliber, on the size and weight of tumors. Together, these results suggest an important antiangiogenic and antitumor role for BthTx-II, as a potential prototype for the development of new tools and antitumor drugs in cancer therapy.

Notch activation suppresses endothelial cell migration and sprouting via miR-223-3p targeting Fbxw7

Angiogenesis involves temporo-spatially coordinated endothelial cell (EC) proliferation, differentiation, migration, and sprouting. Notch signaling is essential in regulating EC behaviors during angiogenesis, but its downstream mechanisms remain incompletely defined. In the current study, we show that miR-223-3p is a downstream molecule of Notch signaling and mediates the role of Notch signaling in regulating EC migration and sprouting. In human umbilical vein endothelial cells (HUVECs), Notch activation by immobilized Dll4, a Notch ligand, upregulated miR-223-3p, and Notch activation-mediated miR-223-3p upregulation could be blocked by a γ-secretase inhibitor (DAPT). miR-223-3p overexpression apparently repressed HUVEC migration, leading to attenuated lumen formation and sprouting capacities. Transcriptome comparison and subsequent qRT-PCR validation further indicated that miR-223-3p downregulated the expression of multiple genes involved in EC migration, axon guidance, extracellular matrix remodeling, and angiogenesis. In addition, miR-223-3p antagonist transfection abolished Notch-mediated repression of EC migration and sprouting. By quantitative reverse transcription-polymerase chain reaction (qRT-PCR), western blotting, and reporter assay analysis, we confirmed that miR-223-3p directly targeted F-box and WD repeat domain-containing 7 (Fbxw7). Meanwhile, Fbxw7 overexpression could efficiently rescue the impaired migration capacity of ECs under miR-223-3p overexpression. In summary, these results identify that Notch activation-induced miR-223-3p suppresses EC migration and sprouting via Fbxw7.

Topical application of TAK1 inhibitor encapsulated by gelatin particle alleviates corneal neovascularization

Rationale: Corneal neovascularization (CoNV) is a severe complication of various types of corneal diseases, that leads to permanent visual impairment. Current treatments for CoNV, such as steroids or anti-vascular endothelial growth factor agents, are argued over their therapeutic efficacy and adverse effects. Here, we demonstrate that transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1) plays an important role in the pathogenesis of CoNV. Methods: Angiogenic activities were assessed in ex vivo and in vitro models subjected to TAK1 inhibition by 5Z-7-oxozeaenol, a selective inhibitor of TAK1. RNA-Seq was used to examine pathways that could be potentially affected by TAK1 inhibition. A gelatin-nanoparticles-encapsulated 5Z-7-oxozeaenol was developed as the eyedrop to treat CoNV in a rodent model. Results: We showed that 5Z-7-oxozeaenol reduced angiogenic processes through impeding cell proliferation. Transcriptome analysis suggested 5Z-7-oxozeaenol principally suppresses cell cycle and DNA replication, thereby restraining cell proliferation. In addition, inhibition of TAK1 by 5Z-7-oxozeaenol blocked TNFα-mediated NFκB signalling, and its downstream genes related to angiogenesis and inflammation. 5Z-7-oxozeaenol also ameliorated pro-angiogenic activity, including endothelial migration and tube formation. Furthermore, topical administration of the gelatin-nanoparticles-encapsulated 5Z-7-oxozeaenol led to significantly greater suppression of CoNV in a mouse model compared to the free form of 5Z-7-oxozeaenol, likely due to extended retention of 5Z-7-oxozeaenol in the cornea. Conclusion: Our study shows the potential of TAK1 as a therapeutic target for pathological angiogenesis, and the gelatin nanoparticle coupled with 5Z-7-oxozeaenol as a promising new eyedrop administration model in treatment of CoNV.

KIF13B-mediated VEGFR2 trafficking is essential for vascular leakage and metastasis in vivo

VEGF-A induces vascular leakage and angiogenesis via activating the cell surface localized receptor VEGF receptor 2 (VEGFR2). The amount of available VEGFR2 at the cell surface is however tightly regulated by trafficking of VEGFR2 by kinesin family 13 B (KIF13B), a plus-end kinesin motor, to the plasma membrane of endothelial cells (ECs). Competitive inhibition of interaction between VEGFR2 and KIF13B by a peptide kinesin-derived angiogenesis inhibitor (KAI) prevented pathological angiogenesis in models of cancer and eye disease associated with defective angiogenesis. Here, we show the protective effects of KAI in VEGF-A-induced vascular leakage and cancer metastasis. Using an EC-specific KIF13B knockout (Kif13b iECKO ) mouse model, we demonstrated the function of EC expressed KIF13B in mediating VEGF-A-induced vascular leakage, angiogenesis, tumor growth, and cancer metastasis. Thus, KIF13B-mediated trafficking of VEGFR2 to the endothelial surface has an essential role in pathological angiogenesis induced by VEGF-A, and is therefore a potential therapeutic target.

The anti-inflammatory peptide Catestatin blocks chemotaxis

Increased levels of the anti‐inflammatory peptide Catestatin (CST), a cleavage product of the pro‐hormone chromogranin A, correlate with less severe outcomes in hypertension, colitis, and diabetes. However, it is unknown how CST reduces the infiltration of monocytes and macrophages (Mϕs) in inflamed tissues. Here, it is reported that CST blocks leukocyte migration toward inflammatory chemokines. By in vitro and in vivo migration assays, it is shown that although CST itself is chemotactic, it blocks migration of monocytes and neutrophils to inflammatory attracting factor CC‐chemokine ligand 2 (CCL2) and C‐X‐C motif chemokine ligand 2 (CXCL2). Moreover, it directs CX₃CR1⁺ Mϕs away from pancreatic islets. These findings suggest that the anti‐inflammatory actions of CST are partly caused by its regulation of chemotaxis.

Proangiogenic Effect of Affinin and an Ethanolic Extract from Heliopsis longipes Roots: Ex Vivo and In Vivo Evidence

Angiogenesis, the formation of new blood vessels, underlies tissue development and repair. Some medicinal plant-derived compounds can modulate the angiogenic response. Heliopsis longipes, a Mexican medicinal plant, is widely used because of its effects on pain and inflammation. The main bioactive phytochemicals from H. longipes roots are alkamides, where affinin is the most abundant. Scientific studies show various medical effects of organic extracts of H. longipes roots and affinin that share some molecular pathways with the angiogenesis process, with the vasodilation mechanism of action being the most recent. This study investigates whether pure affinin and the ethanolic extract from Heliopsis longipes roots (HLEE) promote angiogenesis. Using the aortic ring rat assay (ex vivo method) and the direct in vivo angiogenesis assay, where angioreactors were implanted in CD1 female mice, showed that affinin and the HLEE increased vascular growth in a dose-dependent manner in both bioassays. This is the first study showing the proangiogenic effect of H. longipes. Further studies should focus on the mechanism of action and its possible therapeutic use in diseases characterized by insufficient angiogenesis.

SIRT1-mediated deacetylation of FOXO3a transcription factor supports pro-angiogenic activity of interferon-deficient tumor-associated neutrophils

Angiogenesis plays an important role during tumor growth and metastasis. We could previously show that Type I interferon (IFN)-deficient tumor-associated neutrophils (TANs) show strong pro-angiogenic activity, and stimulate tumor angiogenesis and growth. However, the exact mechanism responsible for their pro-angiogenic shift is not clear. Here, we set out to delineate the molecular mechanism and factors regulating pro-angiogenic properties of neutrophils in the context of Type I IFN availability. We demonstrate that neutrophils from IFN-deficient (Ifnar1^-/- ) mice efficiently release pro-angiogenic factors, such as VEGF, MMP9 or BV8, and thus significantly support the vascular normalization of tumors by increasing the maturation of perivascular cells. Mechanistically, we could show here that the expression of pro-angiogenic factors in neutrophils is controlled by the transcription factor forkhead box protein O3a (FOXO3a), which activity depends on its post-translational modifications, such as deacetylation or phosphorylation. In TANs isolated from Ifnar1^-/- mice, we observe significantly elevated SIRT1, resulting in SIRT1-mediated deacetylation of FOXO3a, its nuclear retention and activation. Activated FOXO3a supports in turn the transcription of pro-angiogenic genes in TANs. In the absence of SIRT1, or after its inhibition in neutrophils, elevated kinase MEK/ERK and PI3K/AKT activity is observed, leading to FOXO3a phosphorylation, cytoplasmic transfer and inactivation. In summary, we have found that FOXO3a is a key transcription factor controlling the angiogenic switch of neutrophils. Post-translational FOXO3a modifications regulate its transcriptional activity and, as a result, the expression of pro-angiogenic factors supporting development of vascular network in growing tumors. Therefore, targeting FOXO3a activity could provide a novel strategy of antiangiogenic targeted therapy for cancer.

Neurovascular dysfunction and neuroinflammation in a Cockayne syndrome mouse model

Cockayne syndrome (CS) is a rare, autosomal genetic disorder characterized by premature aging-like features, such as cachectic dwarfism, retinal atrophy, and progressive neurodegeneration. The molecular defect in CS lies in genes associated with the transcription-coupled branch of the nucleotide excision DNA repair (NER) pathway, though it is not yet clear how DNA repair deficiency leads to the multiorgan dysfunction symptoms of CS. In this work, we used a mouse model of severe CS with complete loss of NER (Csa-/-/Xpa-/-), which recapitulates several CS-related phenotypes, resulting in premature death of these mice at approximately 20 weeks of age. Although this CS model exhibits a severe progeroid phenotype, we found no evidence of in vitro endothelial cell dysfunction, as assessed by measuring population doubling time, migration capacity, and ICAM-1 expression. Furthermore, aortas from CX mice did not exhibit early senescence nor reduced angiogenesis capacity. Despite these observations, CX mice presented blood brain barrier disruption and increased senescence of brain endothelial cells. This was accompanied by an upregulation of inflammatory markers in the brains of CX mice, such as ICAM-1, TNFα, p-p65, and glial cell activation. Inhibition of neovascularization did not exacerbate neither astro- nor microgliosis, suggesting that the pro-inflammatory phenotype is independent of the neurovascular dysfunction present in CX mice. These findings have implications for the etiology of this disease and could contribute to the study of novel therapeutic targets for treating Cockayne syndrome patients.

Tissues with Patterned Vessels or Protein Release Induce Vascular Chemotaxis in an In Vitro Platform

Engineered tissues designed for translational applications in regenerative medicine require vascular networks to deliver oxygen and nutrients rapidly to the implanted cells. A limiting factor of in vivo translation is the rapid and successful inosculation, or connection, of host and implanted vascular networks and subsequent perfusion of the implant. An approach gaining favor in vascular tissue engineering is to provide instructive cues from the engineered tissue to enhance host vascular penetration and connection with the implant. Here, we use a novel in vitro platform based on the aortic ring assay to evaluate the impact of patterned, endothelialized vessels or growth factor release from engineered constructs on preinosculative vascular cell outgrowth from surrogate host tissue in a controlled, defined environment, and introduce robust tools for evaluating vascular morphogenesis and chemotaxis. We demonstrate the creation of engineered vessels at the arteriole scale, which develop basement membrane, exhibit tight junctions, and actively sprout into the surrounding bulk hydrogel. Vessel-containing constructs are co-cultured adjacent to rodent aortic rings, and the resulting heterocellular outgrowth is quantified. Cells originating from the aortic ring migrate preferentially toward constructs containing engineered vessels with 1.5-fold faster outgrowth kinetics, 2.5-fold increased cellular density, and 1.6-fold greater network formation versus control (no endothelial cells and growth factor-reduced culture medium). Growth factor release from constructs with nonendothelialized channels and in reduced factor medium equivalently stimulates sustained vascular outgrowth distance, cellular density, and network formation, akin to engineered vessels in endothelial growth medium 2 (EGM-2) medium. In conclusion, we show that three-dimensional endothelialized patterned vessels or growth factor release stimulate a robust, host-derived vascular cell chemotactic response at early time points critical for instructive angiogenic cues. Further, we developed robust, unbiased tools to quantify metrics of vascular morphogenesis and preinosculative heterocellular outgrowth from rat aortic rings and demonstrated the utility of our complex, controlled environment, heterocellular in vitro platform. Impact statement Using a novel in vitro platform, we show that engineered constructs with patterned vessels or angiogenic growth factor release, two methods of instructing host revascularization responses, equivalently improve early host-derived vascular outgrowth. Our platform leverages the aortic ring assay in a tissue engineering context to study preinosculative vascular cell chemotaxis from surrogate host vascular cells in response to paracrine cues from co-cultured engineered tissues using robust, open-source quantification tools. Our accessible and flexible platform enables translationally focused studies in revascularization using implantable therapeutics containing prepatterned vessels with greater environmental control than in vivo studies to advance vascular tissue engineering.

Artesunate Suppresses Choroidal Melanoma Vasculogenic Mimicry Formation and Angiogenesis via the Wnt/CaMKII Signaling Axis

Angiogenesis and vasculogenic mimicry (VM) are considered to be the main processes to ensure tumor blood supply during the proliferation and metastasis of choroidal melanoma (CM). The traditional antimalarial drug artesunate (ART) has some potential anti-CM effects; however, the underlying mechanisms remain unclarified. Recent studies have shown that the Wnt5a/calmodulin-dependent kinase II (CaMKII) signaling pathway has a close correlation with angiogenesis and VM formation. This study demonstrated that ART eliminated VM formation by inhibiting the aforementioned signaling pathway in CM cells. The microvessel sprouting of the mouse aortic rings and the microvessel density of chicken chorioallantoic membrane (CAM) decreased significantly after ART treatment. VM formation assay and periodic acid schiff (PAS) staining revealed that ART inhibited VM formation in CM. Moreover, ART downregulated the expression levels of the angiogenesis-related proteins vascular endothelial growth factor receptor (VEGFR) 2, platelet-derived growth factor receptor (PDGFR) and vascular endothelial growth factor (VEGF) A, and VM-related proteins ephrin type-A receptor (EphA) 2 and vascular endothelial (VE)-cadherin. The expression of hypoxia-inducible factor (HIF)-1α, Wnt5a, and phosphorylated CaMKII was also downregulated after ART treatment. In addition, we further demonstrated that ART inhibited the proliferation, migration, and invasion of OCM-1 and C918 cells. Collectively, our results suggested that ART inhibited angiogenesis and VM formation of choroidal melanoma likely by regulating the Wnt5a/CaMKII signaling pathway. These findings further supported the feasibility of ART for cancer therapy.

Pro-angiogenic effects of pregnancy-specific glycoproteins in endothelial and extravillous trophoblast cells

We previously reported that binding to heparan sulfate (HS) is required for the ability of the placentally secreted pregnancy-specific glycoprotein 1 (PSG1) to induce endothelial tubulogenesis. PSG1 is composed of four immunoglobulin-like domains but which domains of the protein bind to HS remains unknown. To analyze the interaction of PSG1 with HS, we generated several recombinant proteins, including the individual domains, chimeric proteins between two PSG1 domains, and mutants. Using flow cytometric and surface plasmon resonance studies, we determined that the B2 domain of PSG1 binds to HS and that the positively charged amino acids encompassed between amino acids 43-59 are required for this interaction. Furthermore, we showed that the B2 domain of PSG1 is required for the increase in the formation of tubes by endothelial cells (EC) including a human endometrial EC line and two extravillous trophoblast (EVT) cell lines and for the pro-angiogenic activity of PSG1 observed in an aortic ring assay. PSG1 enhanced the migration of ECs while it increased the expression of matrix metalloproteinase-2 in EVTs, indicating that the pro-angiogenic effect of PSG1 on these two cell types may be mediated by different mechanisms. Despite differences in amino acid sequence, we observed that all human PSGs bound to HS proteoglycans and confirmed that at least two other members of the family, PSG6 and PSG9, induce tube formation. These findings contribute to a better understanding of the pro-angiogenic activity of human PSGs and strongly suggest conservation of this function among all PSG family members.

Lysyl oxidase interactions with transforming growth factor-β during angiogenesis are mediated by endothelin 1

Crosstalk between multiple components underlies the formation of mature vessels. Although the players involved in angiogenesis have been identified, mechanisms underlying the crosstalk between them are still unclear. Using the ex vivo aortic ring assay, we set out to dissect the interactions between two key angiogenic signaling pathways, vascular endothelial growth factor (VEGF) and transforming growth factor β (TGFβ), with members of the lysyl oxidase (LOX) family of matrix modifying enzymes. We find an interplay between VEGF, TGFβ, and the LOXs is essential for the formation of mature vascular smooth muscle cells (vSMC)-coated vessels. RNA sequencing analysis further identified an interaction with the endothelin-1 pathway. Our work implicates endothelin-1 downstream of TGFβ in vascular maturation and demonstrate the complexity of processes involved in generating vSMC-coated vessels.

Endothelial Insulin Receptors Promote VEGF-A Signaling via ERK1/2 and Sprouting Angiogenesis

Endothelial insulin receptors (Insr) promote sprouting angiogenesis, although the underpinning cellular and molecular mechanisms are unknown. Comparing mice with whole-body insulin receptor haploinsufficiency (Insr+/-) against littermate controls, we found impaired limb perfusion and muscle capillary density after inducing hind-limb ischemia; this was in spite of increased expression of the proangiogenic growth factor Vegfa. Insr+/- neonatal retinas exhibited reduced tip cell number and branching complexity during developmental angiogenesis, which was also found in separate studies of mice with endothelium-restricted Insr haploinsufficiency. Functional responses to vascular endothelial growth factor A (VEGF-A), including in vitro angiogenesis, were also impaired in aortic rings and pulmonary endothelial cells from Insr+/- mice. Human umbilical vein endothelial cells with shRNA-mediated knockdown of Insr also demonstrated impaired functional angiogenic responses to VEGF-A. VEGF-A signaling to Akt and endothelial nitric oxide synthase was intact, but downstream signaling to extracellular signal-reduced kinase 1/2 (ERK1/2) was impaired, as was VEGF receptor-2 (VEGFR-2) internalization, which is required specifically for signaling to ERK1/2. Hence, endothelial insulin receptors facilitate the functional response to VEGF-A during angiogenic sprouting and are required for appropriate signal transduction from VEGFR-2 to ERK1/2.

Phosphorylation of pericyte FAK-Y861 affects tumour cell apoptosis and tumour blood vessel regression

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that is overexpressed in many cancer types and in vivo studies have shown that vascular endothelial cell FAK expression and FAK-phosphorylation at tyrosine (Y) 397, and subsequently FAK-Y861, are important in tumour angiogenesis. Pericytes also play a vital role in regulating tumour blood vessel stabilisation, but the specific involvement of pericyte FAK-Y397 and FAK-Y861 phosphorylation in tumour blood vessels is unknown. Using PdgfrβCre + ;FAKWT/WT, PdgfrβCre + ;FAKY397F/Y397F and PdgfrβCre + ;FAKY861F/Y861F mice, our data demonstrate that Lewis lung carcinoma tumour growth, tumour blood vessel density, blood vessel perfusion and pericyte coverage were affected only in late stage tumours in PdgfrβCre + ;FAKY861F/Y861F but not PdgfrβCre + ;FAKY397F/Y397F mice. Further examination indicates a dual role for pericyte FAK-Y861 phosphorylation in the regulation of tumour vessel regression and also in the control of pericyte derived signals that influence apoptosis in cancer cells. Overall this study identifies the role of pericyte FAK-Y861 in the regulation of tumour vessel regression and tumour growth control and that non-phosphorylatable FAK-Y861F in pericytes reduces tumour growth and blood vessel density.

F4, a collagen XIX-derived peptide, inhibits tumor angiogenesis through αvβ3 and α5β1 integrin interaction

We previously demonstrated that F4 peptide (CNPEDCLYPVSHAHQR) from collagen XIX was able to inhibit melanoma cell migrationin vitro and cancer progression in a mouse melanoma model. The aim of the present work was to study the anti-angiogenic properties of F4 peptide. We demonstrated that F4 peptide inhibited VEGF-induced pseudo-tube formation on Matrigel by endothelial cells and endothelial sprouting in a rat aortic ring assay. By affinity chromatography, we identified αvβ3 and α5β1 integrins as potential receptors for F4 peptide on endothelial cell surface. Using solid phase assays, we proved the direct interaction between F4 and both integrins. Taken together, our results demonstrate that F4 peptide is a potent antitumor agent inhibiting both angiogenesis and tumor cell migration.

Tumour microenvironment 3D-modelling: simplicity to complexity and back again

Tumours are surrounded by a host of noncancerous cells that fulfil both supportive and suppressive roles within the tumour microenvironment (TME). The drive to understand the biology behind each of these components has led to a rapid expansion in the number and use of 3D in vitro models, as researchers find ways to incorporate multiple cell types into physiomimetic configurations. The use and increasing complexity of these models does however demand many considerations. In this review we discuss approaches adopted to recapitulate complex tumour biology in tractable 3D models. We consider how these cell types can be sourced and combined and examine methods for the deconvolution of complex multicellular models into manageable and informative outputs.

Interleukin-17A Triggers the Release of Platelet-Derived Factors Driving Vascular Endothelial Cells toward a Pro-Angiogenic State

Platelets comprise a highly interactive immune cell subset of the circulatory system traditionally known for their unique haemostatic properties. Although platelets are considered as a vault of growth factors, cytokines and chemokines with pivotal role in vascular regeneration and angiogenesis, the exact mechanisms by which they influence vascular endothelial cells (ECs) function remain underappreciated. In the present study, we examined the role of human IL-17A/IL-17RA axis in platelet-mediated pro-angiogenic responses. We reveal that IL-17A receptor (IL-17RA) mRNA is present in platelets transcriptome and a profound increase is documented on the surface of activated platelets. By quantifying the protein levels of several factors, involved in angiogenesis, we identified that IL-17A/IL17RA axis selectively induces the release of vascular endothelial growth factor, interleukin -2 and -4, as well as monocyte chemoattractant protein -1 from treated platelets. However, IL-17A exerted no effect on the release of IL-10, an anti-inflammatory factor with potentially anti-angiogenic properties, from platelets. Treatment of human endothelial cell two-dimensional tubule networks or three-dimensional spheroid and mouse aortic ring structures with IL-17A-induced platelet releasate evoked pro-angiogenic responses of ECs. Our findings suggest that IL-17A may critically affect platelet release of pro-angiogenic factors driving ECs towards a pro-angiogenic state.

Contribution of Adventitia-Derived Stem and Progenitor Cells to New Vessel Formation in Tumors

Blocking tumor vascularization has not yet come to fruition to the extent it was hoped for, as angiogenesis inhibitors have shown only partial success in the clinic. We hypothesized that under-appreciated vascular wall-resident stem and progenitor cells (VW-SPCs) might be involved in tumor vascularization and influence effectiveness of anti-angiogenic therapy. Indeed, in patient samples, we observed that vascular adventitia-resident CD34⁺ VW-SPCs are recruited to tumors in situ from co-opted vessels. To elucidate this in detail, we established an ex vivo model using concomitant embedding of multi-cellular tumor spheroids (MCTS) and mouse aortic rings (ARs) into collagen gels, similar to the so-called aortic ring assay (ARA). Moreover, ARA was modified by removing the ARs’ adventitia that harbors VW-SPCs. Thus, this model enabled distinguishing the contribution of VW-SPCs from that of mature endothelial cells (ECs) to new vessel formation. Our results show that the formation of capillary-like sprouts is considerably delayed, and their number and network formation were significantly reduced by removing the adventitia. Substituting iPSC-derived neural spheroids for MCTS resulted in distinct sprouting patterns that were also strongly influenced by the presence or absence of VW-SPCs, also underlying the involvement of these cells in non-pathological vascularization. Our data suggest that more comprehensive approaches are needed in order to block all of the mechanisms contributing to tumor vascularization.

Expression and characterization of a novel single-chain anti-vascular endothelial growth factor antibody in the goat milk

Vascular endothelial growth factor (VEGF) has essential functions in angiogenesis, endothelial cell proliferation, migration, and tumor invasion. Different approaches have been developed to suppress tumor angiogenesis, which is considered a hallmark of cancer. Anti-VEGF monoclonal antibodies constitute an important strategy for cancer immunotherapy, which has been produced on several platforms. In this study, a novel single-chain anti-VEGF monoclonal antibody (scVEGFmAb) was produced in the goat mammary gland by adenoviral transduction. scVEGFmAb was purified by affinity chromatography. N-glycans were analyzed by exoglycosidase digestion and hydrophilic interaction ultra-performance liquid chromatography coupled to electrospray ionization mass spectrometry. The biological activity of scVEGFmAb was assessed by scratch and mouse aortic ring assays. scVEGFmAb was produced at 0.61 g/L in the goat milk, and its purification rendered 95 % purity. N-glycans attached to scVEGFmAb backbone were mainly neutral biantennary core fucosylated with Galβ1,4GlcNAc motif, and charged structures were capped with Neu5Ac and Neu5Gc. The chimeric molecule significantly prevented cell migration and suppressed microvessel sprouting. These results demonstrated for the first time the feasibility of producing an anti-VEGF therapeutic antibody in the milk of non-transgenic goats with the potential to counteract tumor angiogenesis.

Biofabrication of vasculature in microphysiological models of bone

Bone contains a dense network of blood vessels that are essential to its homoeostasis, endocrine function, mineral metabolism and regenerative functions. In addition, bone vasculature is implicated in a number of prominent skeletal diseases, and bone has high affinity for metastatic cancers. Despite vasculature being an integral part of bone physiology and pathophysiology, it is often ignored or oversimplified inin vitrobone models. However, 3D physiologically relevant vasculature can now be engineeredin vitro, with microphysiological systems (MPS) increasingly being used as platforms for engineering this physiologically relevant vasculature. In recent years, vascularised models of bone in MPSs systems have been reported in the literature, representing the beginning of a possible technological step change in how bone is modelledin vitro. Vascularised bone MPSs is a subfield of bone research in its nascency, however given the impact of MPSs has had inin vitroorgan modelling, and the crucial role of vasculature to bone physiology, these systems stand to have a substantial impact on bone research. However, engineering vasculature within the specific design restraints of the bone niche is significantly challenging given the different requirements for engineering bone and vasculature. With this in mind, this paper aims to serve as technical guidance for the biofabrication of vascularised bone tissue within MPS devices. We first discuss the key engineering and biological considerations for engineering more physiologically relevant vasculaturein vitrowithin the specific design constraints of the bone niche. We next explore emerging applications of vascularised bone MPSs, and conclude with a discussion on the current status of vascularised bone MPS biofabrication and suggest directions for development of next generation vascularised bone MPSs.

Exosomes secreted by hiPSC-derived cardiac cells improve recovery from myocardial infarction in swine

Cell therapy treatment of myocardial infarction (MI) is mediated, in part, by exosomes secreted from transplanted cells. Thus, we compared the efficacy of treatment with a mixture of cardiomyocytes (CMs; 10 million), endothelial cells (ECs; 5 million), and smooth muscle cells (SMCs; 5 million) derived from human induced pluripotent stem cells (hiPSCs), or with exosomes extracted from the three cell types, in pigs after MI. Female pigs received sham surgery; infarction without treatment (MI group); or infarction and treatment with hiPSC-CMs, hiPSC-ECs, and hiPSC-SMCs (MI + Cell group); with homogenized fragments from the same dose of cells administered to the MI + Cell group (MI + Fra group); or with exosomes (7.5 mg) extracted from a 2:1:1 mixture of hiPSC-CMs:hiPSC-ECs:hiPSC-SMCs (MI + Exo group). Cells and exosomes were injected into the injured myocardium. In vitro, exosomes promoted EC tube formation and microvessel sprouting from mouse aortic rings and protected hiPSC-CMs by reducing apoptosis, maintaining intracellular calcium homeostasis, and increasing adenosine 5'-triphosphate. In vivo, measurements of left ventricular ejection fraction, wall stress, myocardial bioenergetics, cardiac hypertrophy, scar size, cell apoptosis, and angiogenesis in the infarcted region were better in the MI + Cell, MI + Fra, and MI + Exo groups than in the MI group 4 weeks after infarction. The frequencies of arrhythmic events in animals from the MI, MI + Cell, and MI + Exo groups were similar. Thus, exosomes secreted by hiPSC-derived cardiac cells improved myocardial recovery without increasing the frequency of arrhythmogenic complications and may provide an acellular therapeutic option for myocardial injury.

Ras GEF Mouse Models for the Analysis of Ras Biology and Signaling

Animal models have become in recent years a crucial tool to understand the physiological and pathological roles of many cellular proteins. They allow analysis of the functional consequences of [1] complete or partial (time- or organ-limited) removal of specific proteins (knockout animals), [2] the exchange of a wild-type allele for a mutant or truncated version found in human illnesses (knock-in), or [3] the effect of overexpression of a given protein in the whole body or in specific organs (transgenic mice). In this regard, the study of phenotypes in Ras GEF animal models has allowed researchers to find specific functions for otherwise very similar proteins, uncovering their role in physiological contexts such as memory formation, lymphopoiesis, photoreception, or body homeostasis. In addition, mouse models have been used to unveil the functional role of Ras GEFs under pathological conditions, including Noonan syndrome, skin tumorigenesis, inflammatory diseases, diabetes, or ischemia among others. In the following sections, we will describe the methodological approaches employed for Ras GEF animal model analyses, as well as the main discoveries made.

Deletion of Ulk1 inhibits neointima formation by enhancing KAT2A/GCN5-mediated acetylation of TUBA/α-tubulin in vivo

ULK1 (unc-51 like autophagy activating kinase) has a central role in initiating macroautophagy/autophagy, a process that contributes to atherosclerosis and neointima hyperplasia, or excessive tissue growth that leads to vessel dysfunction. However, the role of ULK1 in neointima formation remains unclear. We aimed to determine how Ulk1 deletion affected neointima formation and to investigate the underlying mechanisms. We measured autophagy activity, vascular smooth muscle cell (VSMC) migration and neointima hyperplasia in cultured VSMCs and ligation-injured mouse carotid arteries from male wild-type (WT, C57BL/6 J) and VSMC-specific ulk1 knockout (ulk1 KO) mice. Carotid artery ligation in WT mice increased ULK1 protein expression, and concurrently increased autophagic flux and neointima formation. Treating human aortic smooth muscle cells (HASMCs) with PDGF (platelet derived growth factor) increased ULK1 expression, activated autophagy, and promoted cell migration. Further, smooth muscle cell-specific deletion of Ulk1 suppressed autophagy, inhibited VSMC migration, and impeded neointima hyperplasia. Mechanistically, Ulk1 deletion inhibited autophagic degradation of histone acetyltransferase protein KAT2A/GCN5 (K[lysine] acetyltransferase 2A), resulting in accumulation of KAT2A that directly acetylated TUBA/α-tubulin and subsequently increased protein levels of acetylated TUBA. The acetylation of TUBA increased microtubule stability and inhibited VSMC directional migration and neointima formation. Finally, local transfection of Kat2a siRNA decreased TUBA acetylation and prevented the attenuation of vascular injury-induced neointima formation in ulk1 KO mice. These findings suggest that Ulk1 deletion inhibits neointima formation by reducing autophagic degradation of KAT2A and increasing TUBA acetylation in VSMCs.Abbreviations: ACTA2/α-SMA: actin, alpha 2, smooth muscle, aorta; ACTB: actin beta; ATAT1: alpha tubulin acetyltransferase 1; ATG: autophagy related; BECN1: beclin 1; BP: blood pressure; CAL: carotid artery ligation; CQ: chloroquine diphosphate; EC: endothelial cells; EEL: external elastic layer; FBS: fetal bovine serum; GAPDH: glyceraldehyde 3-phosphate dehydrogenase; HASMCs: human aortic smooth muscle cells; HAT1: histone acetyltransferase 1; HDAC: histone deacetylase; IEL: inner elastic layer; IP: immunoprecipitation; KAT2A/GCN5: K(lysine) acetyltransferase 2A; KAT8/hMOF: lysine acetyltransferase 8; MAP1LC3: microtubule associated protein 1 light chain 3; MYH11: myosin heavy chain 11; PBS: phosphate-buffered saline; PDGF: platelet derived growth factor; PECAM1/CD31: platelet and endothelial cell adhesion molecule 1; RAC3: Rac family small GTPase 3; SIRT2: sirtuin 2; SPP1/OPN: secreted phosphoprotein 1; SQSTM1/p62: sequestosome 1; TAGLN/SM22: transgelin; TUBA: tubulin alpha; ULK1: unc-51 like autophagy activating kinase; VSMC: vascular smooth muscle cell; VVG: Verhoeff Van Gieson; WT: wild type.

Protein Phosphatase 2A Mediates YAP Activation in Endothelial Cells Upon VEGF Stimulation and Matrix Stiffness

Angiogenesis is an essential process during development. Abnormal angiogenesis also contributes to many disease conditions such as tumor and retinal diseases. Previous studies have established the Hippo signaling pathway effector Yes-associated protein (YAP) as a crucial regulator of angiogenesis. In ECs, activated YAP promotes endothelial cell proliferation, migration and sprouting. YAP activity is regulated by vascular endothelial growth factor (VEGF) and mechanical cues such as extracellular matrix (ECM) stiffness. However, it is unclear how VEGF or ECM stiffness signal to YAP, especially how dephosphorylation of YAP occurs in response to VEGF stimulus or ECM stiffening. Here, we show that protein phosphatase 2A (PP2A) is required for this process. Blocking PP2A activity abolishes VEGF or ECM stiffening mediated YAP activation. Systemic administration of a PP2A inhibitor suppresses YAP activity in blood vessels in developmental and pathological angiogenesis mouse models. Consistently, PP2A inhibitor also inhibits sprouting angiogenesis. Mechanistically, PP2A directly interacts with YAP, and this interaction requires proper cytoskeleton dynamics. These findings identify PP2A as a crucial mediator of YAP activation in ECs and hence as an important regulator of angiogenesis.

Upregulated Angiogenesis Is Incompetent to Rescue Dilated Cardiomyopathy Phenotype in Mice

Dilated cardiomyopathy (DCM) is characterized by pathologic cardiac remodeling resulting in chambers enlargement and impaired heart contractility. Previous reports and our in-silico analysis support the association of DCM phenotype and impaired tissue angiogenesis. Here, we explored whether the modulation in cardiac angiogenesis partly intervenes or rescues the DCM phenotype in mice. Here, a DCM mouse model [α-tropomyosin 54 (α-TM54) mutant] was crossbred with microRNA-210 transgenic mice (210-TG) to develop microRNA-210 (miR-210) overexpressing α-TM54 mutant mice (TMx210). Contrary to wild-type (WT) and 210-TG mice, a significant increase in heart weight to body weight ratio in aged mixed-gender TMx210 and DCM mice was recorded. Histopathological analysis revealed signs of pathological cardiac remodeling such as myocardial disarray, myofibrillar loss, and interstitial fibrosis in DCM and TMx210 mice. Contrary to WT and DCM, a significant increase in angiogenic potential was observed in TMx210 and 210-TG mice hearts which is reflected by higher blood vessel density and upregulated proangiogenic vascular endothelial growth factor-A. The echocardiographic assessment showed comparable cardiac dysfunction in DCM and TMx210 mice as compared to WT and 210-TG. Overall, the present study concludes that miR-210 mediated upregulated angiogenesis is not sufficient to rescue the DCM phenotype in mice.

SARAF and Orai1 Contribute to Endothelial Cell Activation and Angiogenesis

Angiogenesis is a multistep process that controls endothelial cells (ECs) functioning to form new blood vessels from preexisting vascular beds. This process is tightly regulated by pro-angiogenic factors, such as vascular endothelial growth factor (VEGF), which promote signaling pathways involving the increase in the intracellular Ca²⁺ concentration ([Ca²⁺]_i). Recent evidence suggests that store-operated calcium entry (SOCE) might play a role in angiogenesis. However, little is known regarding the role of SARAF, SOCE-associated regulatory factor, and Orai1, the pore-forming subunit of the store-operated calcium channel (SOCC), in angiogenesis. Here, we show that SOCE inhibition with GSK-7975A blocks aorta sprouting, as well as human umbilical vein endothelial cell (HUVEC) tube formation and migration. The intraperitoneal injection of GSK-7975A also delays the development of retinal vasculature assessed at postnatal day 6 in mice, since it reduces vessel length and the number of junctions, while it increases lacunarity. Moreover, we find that SARAF and Orai1 are involved in VEGF-mediated [Ca²⁺]_i increase, and their knockdown using siRNA impairs HUVEC tube formation, proliferation, and migration. Finally, immunostaining and in situ proximity ligation assays indicate that SARAF likely interacts with Orai1 in HUVECs. Therefore, these findings show for the first time a functional interaction between SARAF and Orai1 in ECs and highlight their essential role in different steps of the angiogenesis process.

bFGF alleviates diabetes-associated endothelial impairment by downregulating inflammation via S-nitrosylation pathway

Protein S-nitrosylation is a reversible protein modification implicated in both physiological and pathophysiological regulation of protein function. However, the relationship between dysregulated S-nitrosylation homeostasis and diabetic vascular complications remains incompletely understood. Here, we demonstrate that basic fibroblast growth factor (bFGF) is a key regulatory link between S-nitrosylation homeostasis and inflammation, and alleviated endothelial dysfunction and angiogenic defects in diabetes. Subjecting human umbilical vein endothelial cells (HUVECs) to hyperglycemia and hyperlipidemia significantly decreased endogenous S-nitrosylated proteins, including S-nitrosylation of inhibitor kappa B kinase β (IKKβ^C179) and transcription factor p65 (p65^C38), which was alleviated by bFGF co-treatment. Pretreatment with carboxy-PTIO (c-PTIO), a nitric oxide scavenger, abolished bFGF-mediated S-nitrosylation increase and endothelial protection. Meanwhile, nitrosylation-resistant IKKβ^C179S and p65^C38S mutants exacerbated endothelial dysfunction in db/db mice, and in cultured HUVECs subjected to hyperglycemia and hyperlipidemia. Mechanistically, bFGF-mediated increase of S-nitrosylated IKKβ and p65 was attributed to synergistic effects of increased endothelial nitric oxide synthase (eNOS) and thioredoxin (Trx) activity. Taken together, the endothelial protective effect of bFGF under hyperglycemia and hyperlipidemia can be partially attributed to its role in suppressing inflammation via the S-nitrosylation pathway.

VE-cadherin endocytosis controls vascular integrity and patterning during development

Tissue morphogenesis requires dynamic intercellular contacts that are subsequently stabilized as tissues mature. The mechanisms governing these competing adhesive properties are not fully understood. Using gain- and loss-of-function approaches, we tested the role of p120-catenin (p120) and VE-cadherin (VE-cad) endocytosis in vascular development using mouse mutants that exhibit increased (VE-cad^GGG/GGG) or decreased (VE-cad^DEE/DEE) internalization. VE-cad^GGG/GGG mutant mice exhibited reduced VE-cad-p120 binding, reduced VE-cad levels, microvascular hemorrhaging, and decreased survival. By contrast, VE-cad^DEE/DEE mutants exhibited normal vascular permeability but displayed microvascular patterning defects. Interestingly, VE-cad^DEE/DEE mutant mice did not require endothelial p120, demonstrating that p120 is dispensable in the context of a stabilized cadherin. In vitro, VE-cadDEE mutant cells displayed defects in polarization and cell migration that were rescued by uncoupling VE-cadDEE from actin. These results indicate that cadherin endocytosis coordinates cell polarity and migration cues through actin remodeling. Collectively, our results indicate that regulated cadherin endocytosis is essential for both dynamic cell movements and establishment of stable tissue architecture.

Tissue-Resident PDGFRα+ Progenitor Cells Contribute to Fibrosis versus Healing in a Context- and Spatiotemporally Dependent Manner

PDGFRα⁺ mesenchymal progenitor cells are associated with pathological fibro-adipogenic processes. Conversely, a beneficial role for these cells during homeostasis or in response to revascularization and regeneration stimuli is suggested, but remains to be defined. We studied the molecular profile and function of PDGFRα⁺ cells in order to understand the mechanisms underlying their role in fibrosis versus regeneration. We show that PDGFRα⁺ cells are essential for tissue revascularization and restructuring through injury-stimulated remodeling of stromal and vascular components, context-dependent clonal expansion, and ultimate removal of pro-fibrotic PDGFRα⁺-derived cells. Tissue ischemia modulates the PDGFRα⁺ phenotype toward cells capable of remodeling the extracellular matrix and inducing cell-cell and cell-matrix adhesion, likely favoring tissue repair. Conversely, pathological healing occurs if PDGFRα⁺-derived cells persist as terminally differentiated mesenchymal cells. These studies support a context-dependent "yin-yang" biology of tissue-resident mesenchymal progenitor cells, which possess an innate ability to limit injury expansion while also promoting fibrosis in an unfavorable environment.