ApoA-I Nanotherapy Rescues Postischemic Vascular Maladaptation by Modulating Endothelial Cell and Macrophage Phenotypes in Type 2 Diabetic Mice

BACKGROUND

Diabetes is a major risk factor for peripheral arterial disease. Clinical and preclinical studies suggest an impaired collateral remodeling and angiogenesis in response to atherosclerotic arterial occlusion in diabetic conditions, although the underlying mechanisms are poorly understood.

OBJECTIVE

To clarify the cellular and molecular mechanisms underlying impaired postischemic adaptive vascular responses and to evaluate rHDL (reconstituted HDL)-ApoA-I nanotherapy to rescue the defect in type 2 diabetic mouse model of hindlimb ischemia.

METHODS AND RESULTS

Hindlimb ischemia was induced by unilateral femoral artery ligation. Collateral and capillary parameters together with blood flow recovery were analyzed from normoxic adductor and ischemic gastrocnemius muscles, respectively, at day 3 and 7 post-ligation. In response to femoral artery ligation, collateral lumen area was significantly reduced in normoxic adductor muscles. Distally, ischemic gastrocnemius muscles displayed impaired perfusion recovery and angiogenesis paralleled with persistent inflammation. Muscle-specific mRNA sequencing revealed differential expression of genes critical for smooth muscle proliferation and sprouting angiogenesis in normoxic adductor and ischemic gastrocnemius, respectively, at day 7 post-ligation. Genes typical for macrophage (Mϕ) subsets were differentially expressed across both muscle types. Cell-specific gene expression, flow cytometry, and immunohistochemistry revealed persistent IFN-I response gene upregulation in arterial endothelial cells, ECs and Mϕs from T2DM mice associated with impaired collateral remodeling, angiogenesis and perfusion recovery. Furthermore, rHDL nanotherapy rescued impaired collateral remodeling and angiogenesis through dampening EC and Mϕ inflammation in T2DM mice.

CONCLUSIONS

Our results suggest that an impaired collateral remodeling and sprouting angiogenesis in T2DM mice is associated with persistent IFN-I response in ECs and Mϕs. Dampening persistent inflammation and skewing ECs and Mϕ phenotype toward less inflammatory ones using rHDL nanotherapy may serve as a potential therapeutic target for T2DM peripheral arterial disease.

Endothelial cells and angiogenesis in the horse in health and disease-A review

The cardiovascular system is the first functional organ in the embryo, and its blood vessels form a widespread conductive network within the organism. Blood vessels develop de novo, by the differentiation of endothelial progenitor cells (vasculogenesis) or by angiogenesis, which is the formation of new blood vessels from existing ones. This review presents an overview of the current knowledge on physiological and pathological angiogenesis in the horse including studies on equine endothelial cells. Principal study fields in equine angiogenesis research were identified: equine endothelial progenitor cells; equine endothelial cells and angiogenesis (heterogeneity, markers and assessment); endothelial regulatory molecules in equine angiogenesis; angiogenesis research in equine reproduction (ovary, uterus, placenta and conceptus, testis); angiogenesis research in pathological conditions (tumours, ocular pathologies, equine wound healing, musculoskeletal system and laminitis). The review also includes a table that summarizes in vitro studies on equine endothelial cells, either describing the isolation procedure or using previously isolated endothelial cells. A particular challenge of the review was that results published are fragmentary and sometimes even contradictory, raising more questions than they answer. In conclusion, angiogenesis is a major factor in several diseases frequently occurring in horses, but relatively few studies focus on angiogenesis in the horse. The challenge for the future is therefore to continue exploring new therapeutic angiogenesis strategies for horses to fill in the missing pieces of the puzzle.

Significance of Cellular Cross-Talk in Stromal Vascular Fraction of Adipose Tissue in Neovascularization

Adult stem cell-based therapy has been regarded as a promising treatment for tissue ischemia because of its ability to promote new blood vessel formation. Bone marrow-derived mesenchymal stem cells are the most used angiogenic cells for therapeutic neovascularization, yet the side effects and low efficacy have limited their clinical application. Adipose stromal vascular fraction is an easily accessible, heterogeneous cell system comprised of endothelial, stromal, and hematopoietic cell lineages, which has been shown to spontaneously form robust, patent, and functional vasculatures in vivo. However, the characteristics of each cell population and their specific roles in neovascularization remain an area of ongoing investigation. In this review, we summarize the functional capabilities of various stromal vascular fraction constituents during the process of neovascularization and attempt to analyze whether the cross-talk between these constituents generates a synergetic effect, thus contributing to the development of new potential therapeutic strategies to promote neovascularization.

Endothelial C-Type Natriuretic Peptide Is a Critical Regulator of Angiogenesis and Vascular Remodeling

BACKGROUND

Angiogenesis and vascular remodeling are complementary, innate responses to ischemic cardiovascular events, including peripheral artery disease and myocardial infarction, which restore tissue blood supply and oxygenation; the endothelium plays a critical function in these intrinsic protective processes. C-type natriuretic peptide (CNP) is a fundamental endothelial signaling species that coordinates vascular homeostasis. Herein, we sought to delineate a central role for CNP in angiogenesis and vascular remodeling in response to ischemia.

METHODS

The in vitro angiogenic capacity of CNP was examined in pulmonary microvascular endothelial cells and aortic rings isolated from wild-type, endothelium-specific CNP^-/-, global natriuretic peptide receptor (NPR)-B^-/- and NPR-C^-/- animals, and human umbilical vein endothelial cells. These studies were complemented by in vivo investigation of neovascularization and vascular remodeling after ischemia or vessel injury, and CNP/NPR-C expression and localization in tissue from patients with peripheral artery disease.

RESULTS

Clinical vascular ischemia is associated with reduced levels of CNP and its cognate NPR-C. Moreover, genetic or pharmacological inhibition of CNP and NPR-C, but not NPR-B, reduces the angiogenic potential of pulmonary microvascular endothelial cells, human umbilical vein endothelial cells, and isolated vessels ex vivo. Angiogenesis and remodeling are impaired in vivo in endothelium-specific CNP^-/- and NPR-C^-/-, but not NPR-B^-/-, mice; the detrimental phenotype caused by genetic deletion of endothelial CNP, but not NPR-C, can be rescued by pharmacological administration of CNP. The proangiogenic effect of CNP/NPR-C is dependent on activation of G_i, ERK1/2, and phosphoinositide 3-kinase γ/Akt at a molecular level.

CONCLUSIONS

These data define a central (patho)physiological role for CNP in angiogenesis and vascular remodeling in response to ischemia and provide the rationale for pharmacological activation of NPR-C as an innovative approach to treating peripheral artery disease and ischemic cardiovascular disorders.

TBX20 Regulates Angiogenesis Through the Prokineticin 2-Prokineticin Receptor 1 Pathway

BACKGROUND

Angiogenesis is integral for embryogenesis, and targeting angiogenesis improves the outcome of many pathological conditions in patients. TBX20 is a crucial transcription factor for embryonic development, and its deficiency is associated with congenital heart disease. However, the role of TBX20 in angiogenesis has not been described.

METHODS

Loss- and gain-of-function approaches were used to explore the role of TBX20 in angiogenesis both in vitro and in vivo. Angiogenesis gene array was used to identify key downstream targets of TBX20.

RESULTS

Unbiased gene array survey showed that TBX20 knockdown profoundly reduced angiogenesis-associated PROK2 (prokineticin 2) gene expression. Indeed, loss of TBX20 hindered endothelial cell migration and in vitro angiogenesis. In a murine angiogenesis model using subcutaneously implanted Matrigel plugs, we observed that TBX20 deficiency markedly reduced PROK2 expression and restricted intraplug angiogenesis. Furthermore, recombinant PROK2 administration enhanced angiogenesis and blood flow recovery in murine hind-limb ischemia. In zebrafish, transient knockdown of tbx20 by morpholino antisense oligos or genetic disruption of tbx20 by CRISPR/Cas9 impaired angiogenesis. Furthermore, loss of prok2 or its cognate receptor prokr1a also limited angiogenesis. In contrast, overexpression of prok2 or prokr1a rescued the impaired angiogenesis in tbx20-deficient animals.

CONCLUSIONS

Our study identifies TBX20 as a novel transcription factor regulating angiogenesis through the PROK2-PROKR1 (prokineticin receptor 1) pathway in both development and disease and reveals a novel mode of angiogenic regulation whereby the TBX20-PROK2-PROKR1 signaling cascade may act as a "biological capacitor" to relay and sustain the proangiogenic effect of vascular endothelial growth factor. This pathway may be a therapeutic target in the treatment of diseases with dysregulated angiogenesis.

A cortical microvascular structure in vascular dementia, Alzheimer's disease, frontotemporal lobar degeneration and nondemented controls: a sign of angiogenesis due to brain ischaemia?

Aims

We observed a microvascular structure in the cerebral cortex that has not, to our knowledge, been previously described. We have termed the structure a ‘raspberry’, referring to its appearance under a bright‐field microscope. We hypothesized that raspberries form through angiogenesis due to some form of brain ischaemia or hypoperfusion. The aims of this study were to quantify raspberry frequency within the cerebral cortex according to diagnosis (vascular dementia, Alzheimer's disease, frontotemporal lobar degeneration and nondemented controls) and brain regions (frontal, temporal, parietal and occipital cortices, regardless of diagnosis).

Materials and methods

In each of 10 age‐matched subjects per group, a 20‐mm section of the cerebral cortex was examined in haematoxylin‐and‐eosin‐stained sections of the frontal, temporal and parietal, and/or occipital lobes. Tests were performed to validate the haematoxylin‐and‐eosin‐based identification of relative differences between the groups, and to investigate inter‐rater variability.

Results

Raspberry frequency was highest in subjects with vascular dementia, followed by those with frontotemporal lobar degeneration, Alzheimer's disease and last, nondemented controls. The frequency of raspberries in subjects with vascular dementia differed from that of all other groups at a statistically significant level. In the cerebral lobes, there was a statistically significant difference between the frontal and occipital cortices.

Conclusions

We believe the results support the hypothesis that raspberries are a sign of angiogenesis in the adult brain. It is pertinent to discuss possible proangiogenic stimuli, including brain ischaemia (such as mild hypoperfusion due to a combination of small vessel disease and transient hypotension), neuroinflammation and protein pathology.

Metastasis-Associated 1 (MTA1) Gene Expression Promotes Angiogenesis in Mouse Xenografts from Human Non-Small Cell Lung Cancer (NSCLC) Cells

BACKGROUND This study aimed to investigate the effects of metastasis-associated 1 (MTA1) gene expression and gene silencing in human non-small cell lung cancer (NSCLC) cells in vitro and on angiogenesis in tumor xenografts in vivo in nude mice. MATERIAL AND METHODS Human H460 and H1299 NSCLC cell lines underwent transfection with lentiviral transfer plasmids (lenti) and short-interfering RNA (si-RNA) and included a control group, a lenti-MTA1 group, a lenti-si-MTA1 group, a lenti control group, and a si-RNA control group. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to detect MTA1 gene expression after cell transfection. MTA1 transfection was more effective in H460 cells, which were selected for further in vivo studies. Sixty Balb/c nude mice, containing human H460 cell tumor xenografts, included a control group (N=20), a lenti-MTA1 group (N=20), and a lenti-si-MTA1 group (N=20). Tumor tissue immunohistochemistry was used to detect the expression of MTA1 protein and microvessel density (MVD) using CD31. Western blot was used to quantify the expression of cyclooxygenase-2 (COX-2), angiopoietin 1/2 (Ang1/2), hypoxia-inducible factor 1-a (HIF-1a), and vascular endothelial growth factor (VEGF). RESULTS MTA1 silencing with si-RNA significantly reduced the tumor growth rate in nude mice (p<0.01), reduced tumor MVD, and 70% of mice survived for more than 30 days. MTA1 overexpression resulted in the death of all mice at 30 days after tumor inoculation and upregulated the expression of COX-2, Ang1/2, HIF-1a and VEGF, which were down-regulated by MTA1 silencing. CONCLUSIONS MTA1 gene expression promoted angiogenesis in mouse xenografts from human NSCLC cells.

A MicroRNA93-Interferon Regulatory Factor-9-Immunoresponsive Gene-1-Itaconic Acid Pathway Modulates M2-Like Macrophage Polarization to Revascularize Ischemic Muscle

BACKGROUND

Currently, no therapies exist for treating and improving outcomes in patients with severe peripheral artery disease (PAD). MicroRNA93 (miR93) has been shown to favorably modulate angiogenesis and to reduce tissue loss in genetic PAD models. However, the cell-specific function, downstream mechanisms, or signaling involved in miR93-mediated ischemic muscle neovascularization is not clear. Macrophages were best known to modulate arteriogenic response in PAD, and the extent of arteriogenic response induced by macrophages is dependent on greater M2 to M1 activation/polarization state. In the present study, we identified a novel mechanism by which miR93 regulates macrophage polarization to promote angiogenesis and arteriogenesis to revascularize ischemic muscle in experimental PAD.

METHODS

In vitro (macrophages, endothelial cells, skeletal muscle cells under normal and hypoxia serum starvation conditions) and in vivo experiments in preclinical PAD models (unilateral femoral artery ligation and resection) were conducted to examine the role of miR93-interferon regulatory factor-9-immunoresponsive gene-1 (IRG1)-itaconic acid pathway in macrophage polarization, angiogenesis, arteriogenesis, and perfusion recovery.

RESULTS

In vivo, compared with wild-type controls, miR106b-93-25 cluster-deficient mice (miR106b-93-25^-/-) showed decreased angiogenesis and arteriogenesis correlating with increased M1-like macrophages after experimental PAD. Intramuscular delivery of miR93 in miR106b-93-25^-/- PAD mice increased angiogenesis, arteriogenesis, and the extent of perfusion, which correlated with more M2-like macrophages in the proximal and distal hind-limb muscles. In vitro, miR93 promotes and sustains M2-like polarization even under M1-like polarizing conditions (hypoxia serum starvation). Delivery of bone marrow-derived macrophages from miR106b-93-25^-/- to wild-type ischemic muscle decreased angiogenesis, arteriogenesis, and perfusion, whereas transfer of wild-type macrophages to miR106b-93-25^-/- had the opposite effect. Systematic analysis of top differentially upregulated genes from RNA sequencing between miR106b-93-25^-/- and wild-type ischemic muscle showed that miR93 regulates IRG1 function to modulate itaconic acid production and macrophage polarization. The 3' untranslated region luciferase assays performed to determine whether IRG1 is a direct target of miR93 revealed that IRG1 is not an miR93 target but that interferon regulatory factor-9, which can regulate IRG1 expression, is an miR93 target. In vitro, increased expression of interferon regulatory factor-9 and IRG1 and itaconic acid treatment significantly decreased endothelial angiogenic potential.

CONCLUSIONS

miR93 inhibits interferon regulatory factor-9 to decrease IRG1-itaconic acid production to induce M2-like polarization in ischemic muscle to enhance angiogenesis, arteriogenesis, and perfusion recovery in experimental PAD.

Long Noncoding RNA MANTIS Facilitates Endothelial Angiogenic Function

Supplemental Digital Content is available in the text.

Background:

The angiogenic function of endothelial cells is regulated by numerous mechanisms, but the impact of long noncoding RNAs (lncRNAs) has hardly been studied. We set out to identify novel and functionally important endothelial lncRNAs.

Methods:

Epigenetically controlled lncRNAs in human umbilical vein endothelial cells were searched by exon-array analysis after knockdown of the histone demethylase JARID1B. Molecular mechanisms were investigated by RNA pulldown and immunoprecipitation, mass spectrometry, microarray, several knockdown approaches, CRISPR-Cas9, assay for transposase-accessible chromatin sequencing, and chromatin immunoprecipitation in human umbilical vein endothelial cells. Patient samples from lung and tumors were studied for MANTIS expression.

Results:

A search for epigenetically controlled endothelial lncRNAs yielded lncRNA n342419, here termed MANTIS, as the most strongly regulated lncRNA. Controlled by the histone demethylase JARID1B, MANTIS was downregulated in patients with idiopathic pulmonary arterial hypertension and in rats treated with monocrotaline, whereas it was upregulated in carotid arteries of Macaca fascicularis subjected to atherosclerosis regression diet, and in endothelial cells isolated from human glioblastoma patients. CRISPR/Cas9-mediated deletion or silencing of MANTIS with small interfering RNAs or GapmeRs inhibited angiogenic sprouting and alignment of endothelial cells in response to shear stress. Mechanistically, the nuclear-localized MANTIS lncRNA interacted with BRG1, the catalytic subunit of the switch/sucrose nonfermentable chromatin-remodeling complex. This interaction was required for nucleosome remodeling by keeping the ATPase function of BRG1 active. Thereby, the transcription of key endothelial genes such as SOX18, SMAD6, and COUP-TFII was regulated by ensuring efficient RNA polymerase II machinery binding.

Conclusion:

MANTIS is a differentially regulated novel lncRNA facilitating endothelial angiogenic function.

Selective Targeting of a Novel Epsin-VEGFR2 Interaction Promotes VEGF-Mediated Angiogenesis

RATIONALE

We previously reported that vascular endothelial growth factor (VEGF)-induced binding of VEGF receptor 2 (VEGFR2) to epsins 1 and 2 triggers VEGFR2 degradation and attenuates VEGF signaling. The epsin ubiquitin interacting motif (UIM) was shown to be required for the interaction with VEGFR2. However, the molecular determinants that govern how epsin specifically interacts with and regulates VEGFR2 were unknown.

OBJECTIVE

The goals for the present study were as follows: (1) to identify critical molecular determinants that drive the specificity of the epsin and VEGFR2 interaction and (2) to ascertain whether such determinants were critical for physiological angiogenesis in vivo.

METHODS AND RESULTS

Structural modeling uncovered 2 novel binding surfaces within VEGFR2 that mediate specific interactions with epsin UIM. Three glutamic acid residues in epsin UIM were found to interact with residues in VEGFR2. Furthermore, we found that the VEGF-induced VEGFR2-epsin interaction promoted casitas B-lineage lymphoma-mediated ubiquitination of epsin, and uncovered a previously unappreciated ubiquitin-binding surface within VEGFR2. Mutational analysis revealed that the VEGFR2-epsin interaction is supported by VEGFR2 interacting specifically with the UIM and with ubiquitinated epsin. An epsin UIM peptide, but not a mutant UIM peptide, potentiated endothelial cell proliferation, migration and angiogenic properties in vitro, increased postnatal retinal angiogenesis, and enhanced VEGF-induced physiological angiogenesis and wound healing.

CONCLUSIONS

Distinct residues in the epsin UIM and VEGFR2 mediate specific interactions between epsin and VEGFR2, in addition to UIM recognition of ubiquitin moieties on VEGFR2. These novel interactions are critical for pathophysiological angiogenesis, suggesting that these sites could be selectively targeted by therapeutics to modulate angiogenesis.

Myeloid-Epithelial-Reproductive Receptor Tyrosine Kinase and Milk Fat Globule Epidermal Growth Factor 8 Coordinately Improve Remodeling After Myocardial Infarction via Local Delivery of Vascular Endothelial Growth Factor

BACKGROUND

In infarcted heart, improper clearance of dying cells by activated neighboring phagocytes may precipitate the transition to heart failure. We analyzed the coordinated role of 2 major mediators of efferocytosis, the myeloid-epithelial-reproductive protein tyrosine kinase (Mertk) and the milk fat globule epidermal growth factor (Mfge8), in directing cardiac remodeling by skewing the inflammatory response after myocardial infarction.

METHODS AND RESULTS

We generated double-deficient mice for Mertk and Mfge8 (Mertk(-/-)/Mfge8(-/-)) and challenged them with acute coronary ligature. Compared with wild-type, Mertk-deficient (Mertk(-/-)), or Mfge8-deficient (Mfge8(-/-)) animals, Mertk(-/-)/Mfge8(-/-) mice displayed greater alteration in cardiac function and remodeling. Mertk and Mfge8 were expressed mainly by cardiac Ly6C(High and Low) monocytes and macrophages. In parallel, Mertk(-/-)/Mfge8(-/-) bone marrow chimeras manifested increased accumulation of apoptotic cells, enhanced fibrotic area, and larger infarct size, as well as reduced angiogenesis. We found that the abrogation of efferocytosis affected neither the ability of circulating monocytes to infiltrate cardiac tissue nor the number of resident Ly6C(High) and Ly6C(How) monocytes/macrophages populating the infarcted milieu. In contrast, combined Mertk and Mfge8 deficiency in Ly6C(High)/Ly6C(Low) monocytes/macrophages either obtained from in vitro differentiation of bone marrow cells or isolated from infarcted hearts altered their capacity of efferocytosis and subsequently blunted vascular endothelial growth factor A (VEGFA) release. Using LysMCre(+)/VEGFA(fl/fl) mice, we further identified an important role for myeloid-derived VEGFA in improving cardiac function and angiogenesis.

CONCLUSIONS

After myocardial infarction, Mertk- and Mfge8-expressing monocyte/macrophages synergistically engage the clearance of injured cardiomyocytes, favoring the secretion of VEGFA to locally repair the dysfunctional heart.

CD34-positive stem cells: in the treatment of heart and vascular disease in human beings

Bone marrow-derived CD34(+) cells are a well-characterized population of stem cells that have traditionally been used clinically to reconstitute the hematopoietic system after radiation or chemotherapy. More recently, CD34(+) cells have also been shown to induce therapeutic angiogenesis in animal models of myocardial, peripheral, and cerebral ischemia. The mechanism by which CD34(+) cells promote therapeutic angiogenesis is not completely understood, although evidence supports both direct incorporation of the cells into the expanding vasculature and paracrine secretion of angiogenic growth factors that support the developing microvasculature. Phase I and phase II clinical trials have explored the usefulness of CD34(+) cells in the treatment of ischemic conditions in human patients. As the population of patients diagnosed with some form of ischemic cardiovascular disease expands, the need for more effective treatments also grows, especially in patients who are refractory to standard pharmacologic or revascularization treatment. As phase III trials begin, CD34(+) cells will be definitively tested as a novel treatment for myocardial and peripheral ischemia. This review will discuss what is known about the CD34 antigen and the cells that harbor it, the preclinical evidence supporting the therapeutic potential of CD34(+) cells in ischemic models, and, last, the current evidence for the clinical usefulness of CD34(+) cells in the treatment of human ischemic disease.

Degradable PLGA scaffolds with basic fibroblast growth factor: experimental studies in myocardial revascularization

Our goal was to investigate the efficacy of degradable poly(D,L-lactic-coglycolic acid) (PLGA) scaffolds loaded with basic fibroblast growth factor (bFGF) in inducing cardiac neovascularization, increasing perfusion, and improving cardiac function.For ease of scaffold implantation into the ventricular wall, we developed a channel-producing device. Mini-swine, established as the animal model, were grouped as follows: channels-alone (control) group, channels and blank scaffolds (CBS) group, and channels and bFGF-incorporating scaffolds (CFS) group. Two scaffolds were implanted in each animal in the CBS and CFS groups. Six weeks postoperatively, endothelial cells were immunohistologically stained for von Willebrand factor, and proliferating cells for Ki-67 antigen. The density of new vessels was counted by image-analysis software. Left ventricular function and myocardial perfusion were documented by echocardiography and nuclear scanning, respectively, before implantation and 6 weeks postoperatively.The combined application of PLGA and bFGF ensured sustained release of growth factor in the target region. In the CFS group, Ki-67-positively stained cells, vascular density, and perfusion-defect percentage all showed significant improvement (P < 0.001), compared with the control and CBS groups, which did not. Moreover, the left ventricular fractional shortening percentage in the CFS group (28.98% +/- 1.24%) showed a significant increase, compared with the control group (26.57% +/- 1.92%, P = 0.009) and the CBS group (27.11% +/- 0.71%, P = 0.033), neither of which showed a difference (P = 0.508).The bFGF-incorporating PLGA scaffold can promote neovascular formation, enhance blood-flow perfusion, and improve myocardial function, although the original scaffold lumina were eventually occluded by inflammatory cells and scar tissue.