Inflammation and ischemia-induced lung angiogenesis

Pulmonary Vascular Dysfunctions in Cystic Fibrosis

Cystic fibrosis (CF) is an inherited disorder caused by a deleterious mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Given that the CFTR protein is a chloride channel expressed on a variety of cells throughout the human body, mutations in this gene impact several organs, particularly the lungs. For this very reason, research regarding CF disease and CFTR function has historically focused on the lung airway epithelium. Nevertheless, it was discovered more than two decades ago that CFTR is also expressed and functional on endothelial cells. Despite the great strides that have been made in understanding the role of CFTR in the airway epithelium, the role of CFTR in the endothelium remains unclear. Considering that the airway epithelium and endothelium work in tandem to allow gas exchange, it becomes very crucial to understand how a defective CFTR protein can impact the pulmonary vasculature and overall lung function. Fortunately, more recent research has been dedicated to elucidating the role of CFTR in the endothelium. As a result, several vascular dysfunctions associated with CF disease have come to light. Here, we summarize the current knowledge on pulmonary vascular dysfunctions in CF and discuss applicable therapies.

B-cells in pulmonary arterial hypertension: friend, foe or bystander?

There is an unmet need for new therapeutic strategies that target alternative pathways to improve the prognosis of patients with pulmonary arterial hypertension (PAH). As immunity has been involved in the development and progression of vascular lesions in PAH, we review the potential contribution of B-cells in its pathogenesis and evaluate the relevance of B-cell-targeted therapies. Circulating B-cell homeostasis is altered in PAH patients, with total B-cell lymphopenia, abnormal subset distribution (expansion of naïve and antibody-secreting cells, reduction of memory B-cells) and chronic activation. B-cells are recruited to the lungs through local chemokine secretion, and activated by several mechanisms: 1) interaction with lung vascular autoantigens through cognate B-cell receptors; 2) costimulatory signals provided by T follicular helper cells (interleukin (IL)-21), type 2 T helper cells and mast cells (IL-4, IL-6 and IL-13); and 3) increased survival signals provided by B-cell activating factor pathways. This activity results in the formation of germinal centres within perivascular tertiary lymphoid organs and in the local production of pathogenic autoantibodies that target the pulmonary vasculature and vascular stabilisation factors (including angiotensin-II/endothelin-1 receptors and bone morphogenetic protein receptors). B-cells also mediate their effects through enhanced production of pro-inflammatory cytokines, reduced anti-inflammatory properties by regulatory B-cells, immunoglobulin (Ig)G-induced complement activation, and IgE-induced mast cell activation. Precision-medicine approaches targeting B-cell immunity are a promising direction for select PAH conditions, as suggested by the efficacy of anti-CD20 therapy in experimental models and a trial of rituximab in systemic sclerosis-associated PAH.

Alteration of intestinal microbiota is associated with diabetic retinopathy and its severity: Samples collected from southeast coast Chinese

BACKGROUND

Current approaches for the therapy of diabetic retinopathy (DR), which was one of leading causes of visual impairment, have their limitations. Animal experiments revealed that restructuring of intestinal microbiota can prevent retinopathy.

AIM

To explore the relationship between intestinal microbiota and DR among patients in the southeast coast of China, and provide clues for novel ways to prevention and treatment methods of DR.

METHODS

The fecal samples of non-diabetics (Group C, n = 15) and diabetics (Group DM, n = 30), including 15 samples with DR (Group DR) and 15 samples without DR (Group D), were analyzed by 16S rRNA sequencing. Intestinal microbiota compositions were compared between Group C and Group DM, Group DR and Group D, as well as patients with proliferative diabetic retinopathy (PDR) (Group PDR, n = 8) and patients without PDR (Group NPDR, n = 7). Spearman correlation analyses were performed to explore the associations between intestinal microbiota and clinical indicators.

RESULTS

The alpha and beta diversity did not differ significantly between Group DR and Group D as well as Group PDR and Group NPDR. At the family level, Fusobacteriaceae, Desulfovibrionaceae and Pseudomonadaceae were significantly increased in Group DR than in Group D (P < 0.05, respectively). At the genera level, Fusobacterium, Pseudomonas, and Adlercreutzia were increased in Group DR than Group D while Senegalimassilia was decreased (P < 0.05, respectively). Pseudomonas was negatively correlated with NK cell count (r = -0.39, P = 0.03). Further, the abundance of genera Eubacterium (P < 0.01), Peptococcus, Desulfovibrio, Acetanaerobacterium and Negativibacillus (P < 0.05, respectively) were higher in Group PDR compared to Group NPDR, while Pseudomonas, Alloprevotella and Tyzzerella (P < 0.05, respectively) were lower. Acetanaerobacterium and Desulfovibrio were positively correlated with fasting insulin (r = 0.53 and 0.61, respectively, P < 0.05), when Negativibacillus was negatively correlated with B cell count (r = -0.67, P < 0.01).

CONCLUSION

Our findings indicated that the alteration of gut microbiota was associated with DR and its severity among patients in the southeast coast of China, probably by multiple mechanisms such as producing short-chain fatty acids, influencing permeability of blood vessels, affecting levels of vascular cell adhesion molecule-1, hypoxia-inducible factor-1, B cell and insulin. Modulating gut microbiota composition might be a novel strategy for prevention of DR, particularly PDR in population above.

Extract of Murraya koenigii selectively causes genomic instability by altering redox-status via targeting PI3K/AKT/Nrf2/caspase-3 signaling pathway in human non-small cell lung cancer

BACKGROUND

Lung cancer is the leading cause of cancer-related death worldwide. Dietary bioactives have been used as alternative therapeutics to overcome various adverse effects caused by chemotherapeutics. Curry leaves are a widely used culinary spice and different parts of this plant have been used in traditional medicines. Curry leaves are a rich source of multiple bioactives, especially polyphenols and alkaloids. Therefore, extraction processes play a key role in obtaining the optimum yield of bioactives and their efficacy.

PURPOSE

We aim to select an extraction process that achieves the optimum yield of bioactives in curry leaves crude extract (CLCE) with minimum solvent usage and in a shorter time. Further, to investigate the anticancer properties of CLCE and its mechanism against lung cancer.

METHODS

Different extraction processes were performed and analyzed polyphenol content. The bioactives and essential oils present in curry leaves were identified through LC-MS/MS and GC-MS analysis. The cytotoxicity of microwave-assisted CLCE (MA-CLCE) was investigated through MTT and colony-forming assays. The DNA damage was observed by comet assay. The apoptotic mechanisms of MA-CLCE were investigated by estimating ROS production, depolarization of mitochondrial membrane potential (MMP), and apoptotic proteins. The glutathione assay estimated the antioxidant potential of MA-CLCE in normal cells.

RESULTS

Generally, conventional extraction methods require high temperatures, extra energy input, and time. Recently, green extraction processes are getting wider attention as alternative extraction methods. This study compared different extraction processes and found that the microwave-assisted extraction (MAE) method yields the highest polyphenols from curry leaves among other extraction processes with minimum processing. The MA-CLCE functions as an antioxidant under normal physiological conditions but pro-oxidant to cancer cells. MA-CLCE scavenges free radicals and enhances the intracellular GSH level in alveolar macrophages in situ. We found that MA-CLCE selectively inhibits cell proliferation and induces apoptosis in cancer cells by altering cellular redox status. MA-CLCE induces chromatin condensation and genotoxicity through ROS-induced depolarization of MMP. The depolarization of MMP causes the release of cytochrome c into the cytosol and activates the apoptotic pathway in lung cancer cells. However, pretreatment with ascorbic acid, an antioxidant, inhibits the MA-CLCE-induced apoptosis by reducing ROS production, which impedes mitochondrial membrane disruption, preventing BAX/BCL-2 expression alteration. Simultaneously, MA-CLCE downregulates the expression of survival signaling regulator PI3K/AKT, which modulates Nrf-2. MA-CLCE also diminishes intracellular antioxidant proficiency by suppressing Nrf-2 expression, followed by HO-1 expressions.

CONCLUSION

Among several extraction methods, MA-CLCE is rich in several bioactives, especially polyphenols, alkaloids, and essential oils. Here, we reported for the first time that MA-CLCE functions as a pro-oxidant to lung cancer cells and acts as an antioxidant to normal cells by regulating different cellular programs and signaling pathways. Therefore, it can be further developed as a promising phytomedicine against lung cancer.

Cell-Seeded Biomaterial Scaffolds: The Urgent Need for Unanswered Accelerated Angiogenesis

One of the most arduous challenges in tissue engineering is neovascularization, without which there is a lack of nutrients delivered to a target tissue. Angiogenesis should be completed at an optimal density and within an appropriate period of time to prevent cell necrosis. Failure to meet this challenge brings about poor functionality for the tissue in comparison with the native tissue, extensively reducing cell viability. Prior studies devoted to angiogenesis have provided researchers with some biomaterial scaffolds and cell choices for angiogenesis. For example, while most current angiogenesis approaches require a variety of stimulatory factors ranging from biomechanical to biomolecular to cellular, some other promising stimulatory factors have been underdeveloped (such as electrical, topographical, and magnetic). When it comes to choosing biomaterial scaffolds in tissue engineering for angiogenesis, key traits rush to mind including biocompatibility, appropriate physical and mechanical properties (adhesion strength, shear stress, and malleability), as well as identifying the appropriate biomaterial in terms of stability and degradation profile, all of which may leave essential trace materials behind adversely influencing angiogenesis. Nevertheless, the selection of the best biomaterial and cells still remains an area of hot dispute as such previous studies have not sufficiently classified, integrated, or compared approaches. To address the aforementioned need, this review article summarizes a variety of natural and synthetic scaffolds including hydrogels that support angiogenesis. Furthermore, we review a variety of cell sources utilized for cell seeding and influential factors used for angiogenesis with a concentrated focus on biomechanical factors, with unique stimulatory factors. Lastly, we provide a bottom-to-up overview of angiogenic biomaterials and cell selection, highlighting parameters that need to be addressed in future studies.

The protective role of prolyl oligopeptidase (POP) inhibition in acute lung injury induced by intestinal ischemia-reperfusion

Intestinal ischemia-reperfusion (II/R) develops when the blood flow to the intestines decreases, followed by the reestablishment of the blood supply to the ischemic tissue, resulting in intestinal mucosal barrier dysfunction, with consequent severe local and systemic inflammation. Acute lung injury (ALI) represents the most serious complication after II/R. KYP-2047 is a selective inhibitor of prolyl oligopeptidase (POP), a serine protease involved in the release of pro-angiogenic and inflammatory molecules. The aim of the present study is to assess the effects of POP-inhibition mediated by KYP-2047 treatment in the pathophysiology of ALI following II/R. An in vivo model of II/R was performed and mice were subjected to KYP-2047 treatment (intraperitoneal, 1, 2.5 and 5 mg/kg). Histological analysis, Masson’s trichrome staining, immunohistochemical, immunofluorescence, biochemical and western blots analysis were performed on ileum and lung samples. KYP-2047 treatment ameliorated histological alteration in ileum and lung, reduced collagen amount and lowered inflammatory protein levels. Moreover, TGF-β1, eNOS, VEGF and CD34 positive staining has been modulated; also, a reduction in apoptosis expression was confirmed. This research revealed the strong anti-inflammatory potential of KYP-2047 associated to its modulatory role on angiogenesis and apoptosis, suggesting POP as a novel therapeutic target for ALI after II/R.

Pathological angiogenesis and inflammation in tissues

The role of angiogenesis in the growth of organs and tumors is widely recognized. Vascular-organ interaction is a key mechanism and a concept that enables an understanding of all biological phenomena and normal physiology that is essential for human survival under pathological conditions. Recently, vascular endothelial cells have been classified as a type of innate immune cells that are dependent on the pathological situations. Moreover, inflammatory cytokines and signaling regulators activated upon exposure to infection or various stresses play crucial roles in the pathological function of parenchymal cells, peripheral immune cells, stromal cells, and cancer cells in tissues. Therefore, vascular-organ interactions as a vascular microenvironment or tissue microenvironment under physiological and pathological conditions are gaining popularity as an interesting research topic. Here, we review vascular contribution as a major factor in microenvironment homeostasis in the pathogenesis of normal as well as cancerous tissues. Furthermore, we suggest that the normalization strategy of pathological angiogenesis could be a promising therapeutic target for various diseases, including cancer.

Death or resolution: the "natural history" of pulmonary hypertension in bronchopulmonary dysplasia

OBJECTIVES

The primary objective was to describe the early "natural history" of pulmonary hypertension (PH) in the premature population. The secondary objective was to describe factors associated with poor outcomes in the premature population with PH at 36 weeks post-menstrual age (PMA).

STUDY DESIGN

Retrospective chart review of patients followed at our institution from 2000 to 2017 with echocardiographic (ECHO) evidence of PH at 36 weeks PMA, and born ≤ 32 weeks estimated gestational age (GA). Cox regression was used for survival analysis.

RESULTS

Sixty-one patients with PH (26.5 ± 1.5 weeks at birth) were included. All PH patients had bronchopulmonary dysplasia (BPD), with 89% considered severe; 38% were small for gestational age. Necrotizing enterocolitis requiring surgery was common (25%). Use of post-natal steroids (HR 11.02, p = 0.01) and increased severity of PH (HR 1.05, p < 0.001) were associated with mortality. Pulmonary vein stenosis (PVS) was documented in 26% of the PH cohort, but not associated with increased mortality. ECHO estimation of pulmonary artery pressure (PAP) was available in 84%. PAP was higher in those who died (sPAP/sBP ratio 1.09 ± 27 vs 0.83 ± 20 %, p = 0.0002). At follow-up (mean 250 ± 186 weeks PMA), 72% of the PH cohort was alive. Most survivors (66%) had resolution of their PH on their most recent ECHO; 31% remained on PH therapy.

CONCLUSION

PH resolved in most survivors in this study population. Mortality in those with BPD-PH was associated with male sex, post-natal steroid use, and increased severity of PH, but not with PVS.

Urokinase Attenuates Pulmonary Thromboembolism in an Animal Model by Inhibition of Inflammatory Response

Inflammatory response is an important determining factor for the mortality of patients with pulmonary thromboembolism. Inflammatory mediators can promote thrombus formation and increase hemodynamic instability. Urokinase is a commonly used drug for the treatment of PTE. The effect of urokinase on inflammatory reaction in PTE is still unclear. Our study was aimed at evaluating the effects of the intervention of urokinase and urokinase combined with aspirin in PTE rats. Results revealed that a large amount of infiltrated inflammatory cells surrounding the bronchus, vessels, and pulmonary mesenchyme, and even pulmonary abscess were observed in the PTE rats. CX3CL1/CX3CR1 coexpression, CX3CL1/NF-κB coexpression, and TXA2 were significantly higher. After treatment with urokinase, pulmonary embolism was partially dissolved and inflammatory cell infiltration was significantly reduced. The expression of TNNI3, BNP, D2D, PASP, PADP, PAMP, and TXA2, as well as CX3CL1/CX3CR1 coexpression and CX3CL1/NF-κB coexpression were significantly lowered. Aspirin showed no synergistic action. Therefore, these findings suggested the occurrence of inflammation during the process of PTE in rats. Urokinase treatment reduced the inflammatory response.

Effector T Cells and Ischemia-Induced Systemic Angiogenesis in the Lung

Lymphocytes have been shown to modulate angiogenesis. Our previous work showed that T regulatory (Treg) cell depletion prevented angiogenesis. In the present study, we sought to examine T-cell populations during lung angiogenesis and subsequent angiostasis. In a mouse model of ischemia-induced systemic angiogenesis in the lung, we examined the time course (0-35 d) of neovascularization and T-cell phenotypes within the lung after left pulmonary artery ligation (LPAL). T cells increased and reached a maximum by 10 days after LPAL and then progressively decreased, suggestive of a modulatory role during the early phase of new vessel growth. Because others have shown IFN-γ to be angiostatic in tumor models, we focused on this effector T-cell cytokine to control the magnitude of angiogenesis. Results showed that IFN-γ protein is secreted at low levels after LPAL and that mice required Treg depletion to see the full effect of effector T cells. Using Foxp3(DTR) and diphtheria toxin to deplete T regulatory cells, increased numbers of effector T cells (CD8(+)) and/or increased capacity to secrete the prominent angiostatic cytokine IFN-γ (CD4(+)) were seen. In vitro culture of mouse systemic and pulmonary microvascular endothelial cells with IFN-γ showed increased endothelial cell apoptosis. CD8(-/-) mice and IFN-γR(-/-) mice showed enhanced angiogenesis compared with wild-type mice, confirming that, in this model, IFN-γ limits the extent of systemic neovascularization in the lung.

Ghrelin Decreases Angiogenesis, HIF-1α and VEGF Protein Levels in Chronic Hypoxia in Lung Tissue of Male Rats

PURPOSE

Hypoxia is a condition of decreased availability of oxygen. When cells are exposed to a low oxygen environment, they impel the hypoxia responses to adapt to new situation. The hypoxia response leads to the activation of various cellular signaling pathways. The aim of this study was to evaluate the effect of ghrelin on angiogenesis, Hypoxia-Inducible-Factor-1α (HIF-1) and Vascular endothelial growth factor (VEGF) levels in normobaric hypoxia situation.

METHODS

Twenty four animals were divided into 4 groups (n=6): control (C), ghrelin (Gh), hypoxia (H), and hypoxic animals that received ghrelin (H+Gh). Hypoxia (11%) was induced by an Environmental Chamber System GO2 Altitude. Animals in ghrelin groups received a subcutaneous injection of ghrelin (150 μg/kg/day) for 14 days.

RESULTS

Our results showed that hypoxia significantly (p<0.05) increased angiogenesis without any significant changes on HIF-1 and VEGF levels, whereas ghrelin significantly (p<0.05) decreased angiogenesis, expression of HIF-1 and VEGF in this condition. Ghrelin administration did not show any significant changes in normal conditions.

CONCLUSION

Ghrelin had no effect on angiogenesis, expression of HIF-1 and VEGF in normal oxygen conditions but it reduced angiogenesis process in lung tissue with reducing the level of HIF and VEGF in hypoxic condition. Therefore, effect of ghrelin on angiogenesis could be related to blood oxygen level.

Lung Angiogenesis Requires CD4(+) Forkhead Homeobox Protein-3(+) Regulatory T Cells

Angiogenesis in ischemic organs is modulated by immune cells. Systemic neovascularization of the ischemic lung requires macrophages, with chemokines playing a central role in new vessel growth. Because regulatory T (Treg) cells modulate tumor-induced neovascularization, we questioned whether this CD4(+) lymphocyte subset impacts blood vessel growth during ischemia. In a model of left lung ischemia, an increase in CD4(+) CD25(+) forkhead homeobox protein-3 (Foxp3)(+) cells was observed 3-5 days after the onset of ischemia in wild-type C57Bl/6 mice. Using transgenic mice where Foxp3(+) Treg cells can be depleted with diphtheria toxin (DT; Foxp3(DTR)), we unexpectedly found that Foxp3(+) Treg depletion led to markedly reduced lung angiogenesis (90% reduction from Foxp3(gfp) controls). Adoptive transfer studies using CD4(+) CD25(+) splenocytes from congenic CD45.1 mice into Foxp3(+) Treg-depleted mice showed an almost complete recovery of the angiogenic phenotype (80% of Foxp3(gfp) controls). A survey of lung gene expression of angiogenic (lipopolysaccharide-induced CXC chemokine [LIX], IL-6, IL-17) and angiostatic (IFN-γ, transforming growth factor-β, IL-10) cytokines showed Treg-dependent differences only in LIX (CXCL5) and IL-6. Protein confirmation demonstrated a significant reduction in LIX in Treg-deficient mice compared with controls 5 days after the onset of ischemia. Phenotyping other inflammatory cells in the lung by multicolor flow cytometry demonstrated a significantly reduced number of macrophages (major histocombatibility complex class II [MHCII](int), CD11C(+)) in Treg-deficient lungs compared with Treg-sufficient lungs. Treg cells are essential for maximal systemic angiogenesis after pulmonary ischemia. One likely mechanism responsible for the decrease in angiogenesis in Treg-depleted mice was the decline in the essential CXC chemokine, LIX.

A deficiency in the prostaglandin D2 receptor CRTH2 exacerbates adjuvant-induced joint inflammation

Although the cyclooxygenase metabolites PGs are known to be involved in the progression of arthritis, the role of PGD2 remains unclear. In this study, we evaluated the contribution of signaling mediated through a PGD2 receptor, chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), in the progression of adjuvant-induced joint inflammation. Injection of CFA into the ankle joint stimulated PGD2 production and induced paw swelling in both CRTH2-naive (WT) and CRTH2(-/-) mice. CRTH2(-/-) mice presented more severe arthritic manifestations than did WT mice. Through bone marrow transplantation experiments between WT and CRTH2(-/-) mice, we showed that CRTH2 deficiency in bone marrow-derived immune cells is involved in disease progression. Morphological studies showed that CRTH2 deficiency accelerated the infiltration of macrophages into the inflamed paw. Consistent with this finding, we observed that treatment with the macrophage inactivator GdCl3 or the macrophage-depleting agent liposomal clodronate improved arthritis symptoms in CRTH2(-/-) mice. Adoptive transfer of CRTH2(-/-) macrophages exacerbated joint inflammation in WT mice. In addition, CRTH2 deficiency accelerated, whereas CRTH2 agonism inhibited, the expression of a macrophage-activating cytokine (GM-CSF) and a chemokine receptor (CXCR2) in CFA-treated peritoneal macrophages. Together, these observations demonstrate that PGD2-CRTH2 signaling plays a protective role in joint inflammation by attenuating the infiltration of macrophages.

Physiological and pathological angiogenesis in the adult pulmonary circulation

Angiogenesis occurs during growth and physiological adaptation in many systemic organs, for example, exercise-induced skeletal and cardiac muscle hypertrophy, ovulation, and tissue repair. Disordered angiogenesis contributes to chronic inflammatory disease processes and to tumor growth and metastasis. Although it was previously thought that the adult pulmonary circulation was incapable of supporting new vessel growth, over that past 10 years new data have shown that angiogenesis within this circulation occurs both during physiological adaptive processes and as part of the pathogenic mechanisms of lung diseases. Here we review the expression of vascular growth factors in the adult lung, their essential role in pulmonary vascular homeostasis and the changes in their expression that occur in response to physiological challenges and in disease. We consider the evidence for adaptive neovascularization in the pulmonary circulation in response to alveolar hypoxia and during lung growth following pneumonectomy in the adult lung. In addition, we review the role of disordered angiogenesis in specific lung diseases including idiopathic pulmonary fibrosis, acute adult distress syndrome and both primary and metastatic tumors of the lung. Finally, we examine recent experimental data showing that therapeutic enhancement of pulmonary angiogenesis has the potential to treat lung diseases characterized by vessel loss.

Risk factors for profuse systemic-to-pulmonary artery collateral burden in hypoplastic left heart syndrome

Risk factors for developing systemic-to-pulmonary artery collaterals (SPCs) in hypoplastic left heart syndrome (HLHS) are unknown. We performed a retrospective case-control study to identify risk factors for developing a profuse SPC burden in HLHS. Angiograms of 439 patients with HLHS (performed <2 years of age) were reviewed using a previously published angiographic grading scale to identify cases (profuse SPC burden, n = 20) and controls (no or minimal SPC burden, n = 35). In univariate analyses, profuse SPC burden was associated with mitral atresia and aortic atresia subtype (MA/AA) (65% vs 14%, p <0.0001), use of a Sano shunt (70% vs 37%, p = 0.03), longer log-transformed durations of intensive care unit stay (p = 0.02), hospital stay (p = 0.002), pleural drainage (p = 0.008) after stage 1 palliation, lower oxygen saturation at discharge after stage 1 palliation (82 ± 4 vs 85 ± 4%, p = 0.03), and a history of severe shunt obstruction (37% vs 11%, p = 0.04). In a multivariate logistic regression model, profuse SPC burden was associated with MA/AA subtype (odds ratio 6.6), Sano shunt type (odds ratio 8.6), and log-transformed duration of hospital stay after stage 1 (odds ratio 7.9, model p <0.0001, area under the curve 0.88). Nonassociated parameters included fetal aortic valve dilation, severe cyanotic episodes, number of days with open sternum or number of additional exploratory thoracotomies after stage 1 palliation, pulmonary vein stenosis, and restrictive atrial septal defect. In conclusion, in the present case-control study of patients with HLHS, the development of a profuse SPC burden was associated with MA/AA subtype, Sano shunt type, and longer duration of hospital stay after stage 1 palliation.

Strain variation in response to lung ischemia: role of MMP-12

Background

Systemic neovascularization of the lung during chronic ischemia has been observed in all mammals studied. However, the proteins that orchestrate the complex interaction of new vessel growth and tunneling through lung tissue matrix have not been described. Although previous work has demonstrated the CXC chemokines are essential growth factors in the process of angiogenesis in mice and rats, key matrix proteins have not been identified.

Methods

Since the degradation of chemokines has been shown to be dependent on metalloproteinases (MMP), we first surveyed gene expression patterns (real time RT-PCR) of several lung matrix proteins in DBA/J (D2) mice and C57Bl/6 (B6) mice, strains known to have divergent parenchymal responses in other lung disease models. We studied changes in the time course of MMP-12 activity in D2 and B6 mice. Functional angiogenesis was determined 14 days after the onset of complete left lung ischemia induced by left pulmonary artery ligation (LPAL), using fluorescent microspheres.

Results

Our results confirmed higher levels of MMP-12 gene expression in D2 mice relative to B6, which corresponded to a phenotype of minimal systemic angiogenesis in D2 mice and more robust angiogenesis in B6 mice (p < 0.01). MMP-12 activity decreased over the course of 14 days in B6 mice whereas it increased in D2 mice (p < 0.05). MMP-12 was associated largely with cells expressing the macrophage marker F4/80. Genetic deficiency of MMP-12 resulted in significantly enhanced neovascularization (p < 0.01 from B6).

Conclusion

Taken together, our results suggest macrophage-derived MMP-12 contributes to angiostasis in the ischemic lung.

A therapeutic role for mesenchymal stem cells in acute lung injury independent of hypoxia-induced mitogenic factor

Bone marrow mesenchymal stem cells (BM-MSCs) have therapeutic potential in acute lung injury (ALI). Hypoxia-induced mitogenic factor (HIMF) is a lung-specific growth factor that participates in a variety of lung diseases. In this study, we evaluated the therapeutic role of BM-MSC transplantation in lipopolysaccharide (LPS)- induced ALI and assessed the importance of HIMF in MSC transplantation. MSCs were isolated and identified, and untransduced MSCs, MSCs transduced with null vector or MSCs transduced with a vector encoding HIMF were transplanted into mice with LPS-induced ALI. Histopathological changes, cytokine expression and indices of lung inflammation and lung injury were assessed in the various experimental groups. Lentiviral transduction did not influence the biological features of MSCs. In addition, transplantation of BM-MSCs alone had significant therapeutic effects on LPS-induced ALI, although BM-MSCs expressing HIMF failed to improve the histopathological changes observed with lung injury. Unexpectedly, tumour necrosis factor α levels in lung tissues, lung oedema and leucocyte infiltration into lungs were even higher after the transplantation of MSCs expressing HIMF, followed by a significant increase in lung hydroxyproline content and α-smooth muscle actin expression on day 14, as compared to treatment with untransduced MSCs. BM-MSC transplantation improved LPS-induced lung injury independent of HIMF.

Flt23k nanoparticles offer additive benefit in graft survival and anti-angiogenic effects when combined with triamcinolone

PURPOSE

To determine if nanoparticles delivering plasmids expressing Flt23k (an anti-VEGF intraceptor) can enhance murine cornea transplant survival and whether their effect is synergistic with steroid therapy.

METHODS

Biodegradable PLGA Flt23k loaded or blank nanoparticles were prepared using the emulsion solvent evaporation

METHOD

Graft survival, corneal neovascularization, and corneal lymphangiogenesis were compared among the Flt23k nanoparticles, blank nanoparticles, triamcinolone acetonide, and PBS groups following subconjunctival injection in mice that underwent penetrating keratoplasty. Graft survival, corneal neovascularization, and corneal lymphangiogenesis in a group treated with both nanoparticles and steroid therapy were also analyzed.

RESULTS

The Flt23k nanoparticle group showed less neovascularization, lymphangiogenesis, and graft failure compared with the PBS control group (P < 0.01). The 2-month graft survival rate was 20% in the Flt23k nanoparticle group with no grafts surviving in the PBS group. When the Flt23k nanoparticle was combined with steroid therapy, a significant increase in graft survival was seen compared with both steroid treatment alone (P < 0.05) and steroid combined with blank nanoparticle treatment (P < 0.05). The 2-month graft survival rate was 91.6% in the combination group compared with 47.6% in the triamcinolone-only group and 42.4% in the triamcinolone plus blank nanoparticle group.

CONCLUSIONS

Anti-VEGF nanoparticles (Flt23k) have a significant effect on decreasing neovascularization and lymphangiogenesis, resulting in increased graft survival in penetrating keratoplasty. This beneficial effect is synergistically enhanced with steroid treatment.

Effects of ischemia on lung macrophages

Angiogenesis after pulmonary ischemia is initiated by reactive O(2) species and is dependent on CXC chemokine growth factors, and its magnitude is correlated with the number of lavaged macrophages. After complete obstruction of the left pulmonary artery in mice, the left lung is isolated from the peripheral circulation until 5-7 days later, when a new systemic vasculature invades the lung parenchyma. Consequently, this model offers a unique opportunity to study the differentiation and/or proliferation of monocyte-derived cells within the lung. In this study, we questioned whether macrophage subpopulations were differentially expressed and which subset contributed to growth factor release. We characterized the change in number of all macrophages (MHCII(int), CD11C+), alveolar macrophages (MHCII(int), CD11C+, CD11B-) and mature lung macrophages (MHCII(int), CD11C+, CD11B+) in left lungs from mice immediately (0 h) or 24 h after left pulmonary artery ligation (LPAL). In left lung homogenates, only lung macrophages increased 24 h after LPAL (vs. 0 h; p<0.05). No changes in proliferation were seen in any subset by PCNA expression (0 h vs. 24 h lungs). When the number of monocytic cells was reduced with clodronate liposomes, systemic blood flow to the left lung 14 days after LPAL decreased by 42% (p<0.01) compared to vehicle controls. Furthermore, when alveolar macrophages and lung macrophages were sorted and studied in vitro, only lung macrophages secreted the chemokine MIP-2α (ELISA). These data suggest that ischemic stress within the lung contributes to the differentiation of immature monocytes to lung macrophages within the first 24 h after LPAL. Lung macrophages but not alveolar macrophages increase and secrete the proangiogenic chemokine MIP-2α. Overall, an increase in the number of lung macrophages appears to be critical for neovascularization in the lung, since clodronate treatment decreased their number and attenuated functional angiogenesis.

Overexpression of catalase in myeloid cells causes impaired postischemic neovascularization

OBJECTIVE

Myeloid lineage cells (MLCs) such as macrophages are known to play a key role in postischemic neovascularization. However, the role of MLC-derived reactive oxygen species in this process and their specific chemical identity remain unknown.

METHODS AND RESULTS

Transgenic mice with MLC-specific overexpression of catalase (Tg(Cat-MLC) mice) were created on a C57BL/6 background. Macrophage catalase activity was increased 3.4-fold compared with wild-type mice. After femoral artery ligation, laser Doppler perfusion imaging revealed impaired perfusion recovery in Tg(Cat-MLC) mice. This was associated with fewer collateral vessels, as assessed by microcomputed tomography angiography, and decreased capillary density. Impaired functional recovery of the ischemic limb was also evidenced by a 50% reduction in spontaneous running activity. The deficient neovascularization was associated with a blunted inflammatory response, characterized by decreased macrophage infiltration of ischemic tissues, and lower mRNA levels of inflammatory markers, such as tumor necrosis factor-α, osteopontin, and matrix mettaloproteinase-9. In vitro macrophage migration was impaired in Tg(Cat-MLC) mice, suggesting a role for H(2)O(2) in regulating the ability of macrophages to infiltrate ischemic tissues.

CONCLUSIONS

MLC-derived H(2)O(2) plays a key role in promoting neovascularization in response to ischemia and is a necessary factor for the development of ischemia-induced inflammation.

Role of endothelial injury in disease mechanisms and contribution of progenitor cells in mediating endothelial repair

Recent research on the endothelium demonstrates complex interactions of endothelial cells with circulating immune cells, mediators such as cytokines, hormones and growth factors, and with the underlying parenchymal cells. These disparate interactions are involved in promotion of vascular development; maintenance of tissue homeostasis; and regulation of vascular repair. Injury to the endothelial monolayer is the sine qua non of organ dysfunction with endothelial repair the necessary first step needed for recovery. Thus, the capacity of the endothelium to regenerate itself is a key determinant of organ repair and survival after injury. Using the example of the lung, we will review the current state of knowledge regarding the importance of endothelium in the above mentioned processes with a focus on the role of stem cells, both endogenous (i.e., localized within the vessel wall) as well as exogenous (i.e., arriving in the vessel wall from distant sites such as the bone marrow) in promoting endothelial repair and regeneration. The subject of endothelial regeneration and the ways in which stem and progenitor cells contribute to this process has promise in treating vascular diseases. As we will highlight in this review, some questions have been addressed but many more remain and need to be addressed before cell-based therapies become a viable option.

Angiogenic activity of sera from interstitial lung disease patients in relation to pulmonary function

OBJECTIVE

Chronic inflammation and fibrosis are characteristic of interstitial lung diseases (ILD) and are accompanied by neovascularisation. The aim of this study was to examine the relationship between the angiogenic activity of sera from ILD patients and pulmonary function tests.

MATERIAL AND METHODS

Serum samples were obtained from 225 ILD patients: 83 with sarcoidosis, 31 with idiopathic pulmonary fibrosis, 29 with extrinsic allergic alveolitis, 16 with collagen vascular diseases, 13 with scleroderma with pulmonary manifestations (SCL), 14 with Wegener's granulomatosis (WG), 12 with silicosis, 12 with pulmonary Langerhans cells histiocytosis, 10 with drug-induced pulmonary fibrosis, 5 with cryptogenic organizing pneumonia, and 36 healthy volunteers. An animal model of leukocyte induced angiogenesis assay was used as an angiogenic test. In all patients spirometry, whole body plethysmography, static lung compliance, and single breath diffusing capacity of the lungs for carbon monoxide (DLco) were performed.

RESULTS

The angiogenic properties of sera from ILD differed, depending on the disease. In the examined ILD, the most important functional disturbances were decreases in static compliance and DLco. The correlation between DLco and angiogenic activity of sera was observed (P<0.05).

CONCLUSIONS

The data show that sera from ILD patients constitute a source of mediators modulating angiogenesis. Angiogenic activity of sera of ILD patients is related to DLco.

Role of ROS in ischemia-induced lung angiogenesis

Pulmonary artery obstruction and subsequent lung ischemia have been shown to induce systemic angiogenesis despite preservation of normoxia. The underlying mechanisms, however, remain poorly understood. In a mouse model of lung ischemia induced by left pulmonary artery ligation (LPAL), we showed previously, the formation of a new systemic vasculature to the ischemic lung. We hypothesize that LPAL in the mouse increases reactive oxygen species (ROS) production, and these molecules play an initiating role in subsequent lung neovascularization. We used oxidant-sensitive dyes (DHE and H(2)DCF-DA) to quantify ROS and measured the antioxidant-reduced glutathione (GSH) and its oxidized form (GSSG) as indicators of ROS levels after LPAL. The magnitude of systemic neovascularization was determined by measuring systemic blood flow to the left lung with radiolabeled microspheres 14 days after LPAL. An increase in ROS was observed early (30 min: 55% increase in H(2)DCF-DA) after LPAL, with a return to baseline by 24 h. GSH/GSSG was decreased (∼50%) 4 h after LPAL, suggesting earlier ROS upregulation. Mice treated with the antioxidant N-acetylcysteine showed attenuated angiogenesis (62% of wild-type LPAL), and mice lacking Nrf2, a transcription factor important for antioxidant synthesis, resulted in increased neovascularization (207% of wild-type LPAL). Overall, GSH/GSSG was inversely associated with the magnitude of neovascularization. These results demonstrate that LPAL induces an early and transient ROS upregulation, and ROS appear to play a role in promoting ischemia-induced angiogenesis.

Angiogenic activity of sera from extrinsic allergic alveolitis patients in relation to clinical, radiological, and functional pulmonary changes

Extrinsic allergic alveolitis (EAA) caused by inhaled organic environmental allergens can progress to a fibrotic end-stage lung disease. Neovascularization plays an important role in pathogenesis of pulmonary fibrosis. The aim of this study was to assess the effect of sera from EAA patients on the angiogenic capability of normal peripheral human mononuclear cells (MNC) in relation to the clinical, radiological, and functional changes. The study population consisted of 30 EAA patients and 16 healthy volunteers. Routine pulmonary function tests were undertaken using ERS standards. As an angiogenic test, leukocyte-induced angiogenesis assay according to Sidky and Auerbach was used. Compared with sera from healthy volunteers, sera from our EAA patients significantly stimulated angiogenesis (P < 0.001). However, sera from healthy donors also stimulated angiogenesis compared to PBS (P < 0.001). No correlation was found between serum angiogenic activity and clinical symptoms manifested by evaluated patients. A decrease in DLco and in lung compliance in EAA patients was observed but no significant correlation between pulmonary functional tests and serum angiogenic activity measured by the number of microvessels or an angiogenesis index was found. However, the proangiogenic effect of sera from EAA patients differed depending on the stage of the disease and was stronger in patients with fibrotic changes. The present study suggests that angiogenesis plays a role in the pathogenesis of EAA. It could be possible that the increase in the angiogenic activity of sera from EAA patients depends on the phase of the disease.

In vitro and in vivo evaluation of a novel nanosize hydroxyapatite particles/poly(ester-urethane) composite scaffold for bone tissue engineering

Scaffolds for bone tissue engineering should provide an osteoconductive surface to promote the ingrowth of new bone after implantation into bone defects. This may be achieved by hydroxyapatite loading of distinct scaffold biomaterials. Herein, we analyzed the in vitro and in vivo properties of a novel nanosize hydroxyapatite particles/poly(ester-urethane) (nHA/PU) composite scaffold which was prepared by a salt leaching-phase inverse process. Microtomography, scanning electron microscopy and X-ray spectroscopy analyses demonstrated the capability of the material processing to create a three-dimensional porous PU scaffold with nHA on the surface. Compared to nHA-free PU scaffolds (control), this modified scaffold type induced a significant increase in in vitro adsorption of model proteins. In vivo analysis of the inflammatory and angiogenic host tissue response to implanted nHA/PU scaffolds in the dorsal skinfold chamber model indicated that the incorporation of nHA particles into the scaffold material did not affect biocompatibility and vascularization when compared to control scaffolds. Thus, nHA/PU composite scaffolds represent a promising new type of scaffold for bone tissue engineering, combining the flexible material properties of PU with the advantage of an osteoconductive surface.

Extracellular matrix, inflammation, and the angiogenic response

Inflammation and angiogenesis are frequently coupled in pathological situations such as atherosclerosis, diabetes, and arthritis. The inflammatory response increases capillary permeability and induces endothelial activation, which, when persistent, results in capillary sprouting. This inflammation-induced angiogenesis and the subsequent remodelling steps are in large part mediated by extracellular matrix (ECM) proteins and proteases. The focal increase in capillary permeability is an early consequence of inflammation, and results in the deposition of a provisional fibrin matrix. Subsequently, ECM turnover by proteases permits an invasive program by specialized endothelial cells whose phenotype can be regulated by inflammatory stimuli. ECM activity also provides specific mechanical forces, exposes cryptic adhesion sites, and releases biologically active fragments (matrikines) and matrix-sequestered growth factors, all of which are critical for vascular morphogenesis. Further matrix remodelling and vascular regression contribute to the resolution of the inflammatory response and facilitate tissue repair.

Differential activity of pro-angiogenic CXC chemokines

We showed previously in a mouse model of lung ischemia-induced angiogenesis, enhanced expression of the three ELR+ CXC chemokines (KC, LIX, and MIP-2) and that blockade of the ligand receptor CXCR(2) limited neovascularization. The present study was undertaken to determine the relative abundance and angiogenic potential of the three CXC chemokines and whether RhoA activation explained the measured differences in potencies. We found that LIX showed the greatest absolute amount in the in vivo model 4 h after left pulmonary artery obstruction (LIX>KC>MIP-2; p<0.05). In vitro, LIX induced the greatest degree of arterial endothelial cell chemotaxis and KC was without effect. A significant increase (approximately 40%) in active RhoA was observed with both LIX and MIP-2 compared with vehicle control (p<0.05). On average, LIX induced the greatest amount of tube formation within pleural tissue in culture. Thus, the results of the present study suggest that among the three ELR+ CXC chemokines, LIX predominates in eliciting a pro-angiogenic phenotype.

Monocyte transplantation for neural and cardiovascular ischemia repair

Neovascularization is an integral process of inflammatory reactions and subsequent repair cascades in tissue injury. Monocytes/macrophages play a key role in the inflammatory process including angiogenesis as well as the defence mechanisms by exerting microbicidal and immunomodulatory activity. Current studies have demonstrated that recruited monocytes/macrophages aid in regulating angiogenesis in ischemic tissue, tumours and chronic inflammation. In terms of neovascularization followed by tissue regeneration, monocytes/macrophages should be highly attractive for cell-based therapy compared to any other stem cells due to their considerable advantages: non-oncogenic, non-teratogenic, multiple secretary functions including pro-angiogenic and growth factors, straightforward cell harvesting procedure and non-existent ethical controversy. In addition to adult origins such as bone marrow or peripheral blood, umbilical cord blood (UCB) can be a potential source for autologous or allogeneic monocytes/macrophages. Especially, UCB monocytes should be considered as the first candidate owing to their feasibility, low immune rejection and multiple characteristic advantages such as their anti-inflammatory properties by virtue of their unique immune and inflammatory immaturity, and their pro-angiogenic ability. In this review, we present general characteristics and potential of monocytes/macrophages for cell-based therapy, especially focusing on neovascularization and UCB-derived monocytes.

In vivo biocompatibility and vascularization of biodegradable porous polyurethane scaffolds for tissue engineering

Scaffolds for tissue engineering should be biocompatible and stimulate rapid blood vessel ingrowth. Herein, we analyzed in vivo the biocompatibility and vascularization of three novel types of biodegradable porous polyurethane scaffolds. The polyurethane scaffolds, i.e., PU-S, PU-M and PU-F, were implanted into dorsal skinfold chambers of BALB/c mice. Using intravital fluorescence microscopy we analyzed vascularization of the implants and venular leukocyte-endothelial cell interaction in the surrounding host tissue over a 14 day period. Incorporation of the scaffolds was analyzed by histology, and a WST-1 assay was performed to evaluate their cell biocompatibility in vitro. Our results indicate that none of the polyurethane scaffolds was cytotoxic. Accordingly, rolling and adherent leukocytes in venules of the dorsal skinfold chamber were found in a physiological range after scaffold implantation and did not significantly differ between the groups, indicating a good in vivo biocompatibility. However, the three scaffolds induced a weak angiogenic response with a microvessel density of only approximately 47-60 and approximately 3-10cm/cm(2) in the border and centre zones of the scaffolds at day 14 after implantation. Histology demonstrated that the scaffolds were incorporated in a granulation tissue, which exhibited only a few blood vessels and inflammatory cells. In conclusion, PU-S, PU-M and PU-F scaffolds may be used to generate tissue constructs which do not induce a strong inflammatory reaction after implantation into patients. However, the scaffolds should be further modified or conditioned in order to accelerate and improve the process of vascularization.