Matrix metalloproteinases and matrikines in angiogenesis

Angiogenesis and Re-endothelialization in decellularized scaffolds: Recent advances and current challenges in tissue engineering

Decellularization of tissues and organs has recently become a promising approach in tissue engineering and regenerative medicine to circumvent the challenges of organ donation and complications of transplantations. However, one main obstacle to reaching this goal is acellular vasculature angiogenesis and endothelialization. Achieving an intact and functional vascular structure as a vital pathway for supplying oxygen and nutrients remains the decisive challenge in the decellularization/re-endothelialization procedure. In order to better understand and overcome this issue, complete and appropriate knowledge of endothelialization and its determining variables is required. Decellularization methods and their effectiveness, biological and mechanical characteristics of acellular scaffolds, artificial and biological bioreactors, and their possible applications, extracellular matrix surface modification, and different types of utilized cells are factors affecting endothelialization consequences. This review focuses on the characteristics of endothelialization and how to optimize them, as well as discussing recent developments in the process of re-endothelialization.

Real and Simulated Microgravity: Focus on Mammalian Extracellular Matrix

The lack of gravitational loading is a pivotal risk factor during space flights. Biomedical studies indicate that because of the prolonged effect of microgravity, humans experience bone mass loss, muscle atrophy, cardiovascular insufficiency, and sensory motor coordination disorders. These findings demonstrate the essential role of gravity in human health quality. The physiological and pathophysiological mechanisms of an acute response to microgravity at various levels (molecular, cellular, tissue, and physiological) and subsequent adaptation are intensively studied. Under the permanent gravity of the Earth, multicellular organisms have developed a multi-component tissue mechanosensitive system which includes cellular (nucleo- and cytoskeleton) and extracellular (extracellular matrix, ECM) “mechanosensory” elements. These compartments are coordinated due to specialized integrin-based protein complexes, forming a distinctive mechanosensitive unit. Under the lack of continuous gravitational loading, this unit becomes a substrate for adaptation processes, acting as a gravisensitive unit. Since the space flight conditions limit large-scale research in space, simulation models on Earth are of particular importance for elucidating the mechanisms that provide a response to microgravity. This review describes current state of art concerning mammalian ECM as a gravisensitive unit component under real and simulated microgravity and discusses the directions of further research in this field.

Investigating the vascularization capacity of a decellularized dental pulp matrix seeded with human dental pulp stem cells: in vitro and preliminary in vivo evaluations

AIM

To investigate the vascularization capacity of a decellularized dental pulp matrix (DDP) of bovine origin seeded with human dental pulp stem cells (hDPSCs) in vitro and to present preliminary in vivo findings.

METHODOLOGY

Bovine dental pulps were decellularized and then analysed using histological staining and DNA quantification. The resultant DDPs were characterized using immunohistochemical staining for the retention of vascular endothelial growth factor A (VEGF-A) and fibroblast growth factor 2 (FGF-2). Furthermore, DDPs were recellularized with hDPSCs and analysed histologically. The expression of markers involved in angiogenesis by hDPSCs colonizing the DDPs was assessed in vitro. A preliminary in vivo study was then conducted in which hDPSCs-seeded and unseeded DDPs were inserted in debrided human premolars root slices and implanted subcutaneously in immunodeficient mice. Samples were retrieved after 30 days and analysed using histological and immunohistochemical staining. The independent samples t-test, analysis of variance and a Kruskal-Wallis test were used to analyse the quantitative data statistically depending on the group numbers and normality of data distribution. The difference between the groups was considered significant when the P-value was less than 0.05.

RESULTS

Acellular dental pulp matrices were generated following bovine dental pulp decellularization. Evaluation of the developed DDPs revealed a significant DNA reduction (P < 0.0001) with preservation of the native histoarchitecture and vasculature and retention of VEGF-A and FGF-2. Upon recellularization of the DDPs with hDPSCs, the in vitro analyses revealed cell engraftment with progressive repopulation of DDPs' matrices and vasculature and with enhanced expression of markers involved in angiogenesis. In vivo implantation of root slices with hDPSCs-seeded DDPs revealed apparent vascularization enhancement as compared to the unseeded DDP group (P < 0.0001).

CONCLUSIONS

The developed decellularized dental pulp matrix had pro-angiogenic properties characterized by the retention of native vasculature and angiogenic growth factors. Seeding of hDPSCs into the DDP led to progressive repopulation of the vasculature, enhanced expression of markers involved in angiogenesis in hDPSCs and improved in vivo vascularization capacity. The se suggest that a combination of DDP and hDPSCs have the potential to provide a promising vascularization promoting strategy for dental pulp regeneration.

Important role of annexin A2 (ANXA2) in new blood vessel development in vivo and human triple negative breast cancer (TNBC) growth

Development of new blood vessels in the tumor microenvironment is an essential component of tumor progression during which newly formed blood vessels nourish tumor cells and play a critical role in rapid tumor growth, invasion and metastasis. Nevertheless, how tumor cells develop new blood vessels in the tumor microenvironment (TME) have been enigmatic. Previously, we have shown specific overexpression of ANX A2 in TNBC cells regulates plasmin generation and suspected a role in neoangiogenesis. In this report, we used Matrigel plug model of in vivo angiogenesis and confirmed its role in new blood vessel development. Next, we tested if blocking of ANX A2 in aggressive human breast TME can inhibit angiogenesis and tumor growth in vivo. We showed that aggressive human breast tumor cells growing in nude mice can induce intense neoangiogenesis in the tumor mass. Blocking of ANXA2 significantly inhibited neoangiogenesis and resulted in inhibition of tumor growth. Interestingly, we identified that blocking of ANXA2 significantly inhibited tyrosine phosphorylation (Tyr-P) of ANXA2 implying its involvement in tyrosine signaling pathway and suggesting it may regulate angiogenesis. Taken together, our experimental evidence suggests that ANX A2 could be a novel strategy for disruption of tyrosine signaling and inhibition of neoangiogenesis in breast tumor.

Does sympathetic nervous system modulate tumor progression? A narrative review of the literature

Objective

The role of the sympathetic nervous system (SNS) in tumor development, progression and metastasis is studied for more than half a century and is attracting more attention during the last years. In this narrative review, we aim to a chronological and methodological presentation of the most interesting and pioneering studies on the subject.

Methods

The complexity of the autonomic nervous system’s interaction with the immune system, its direct and indirect effects on tumors and their surrounding tissues, plus the diversity and heterogeneity in the design and methodology of the studies, provide hard-to-interpret data and, at times, controversial findings. Studies are categorized into four main groups regarding the distribution of sympathetic nerve fibers inside the tumor, the effect of sympathectomy on cancer progression, the role of neurotransmitters on tumor growth and the impact of sympathetic adrenergic signaling on the anti-tumor immune response.

Results

Studies from all four categories converge to a common point. There is strong evidence that SNS function plays a role in the development and progression of tumors and subsequently the modification of SNS function, locally or diffusely, can affect the course of tumor growth.

Conclusion

The impact of SNS function on cancer behavior may be exerted in two ways, directly via the sympathetic nerve fibers or through widely distributed neurotransmitters. Modification of them, combined or not with treatments altering the immune function, could be the target for future therapeutic implications.

A type IV collagenase inhibitor, N-hydroxy-3-phenyl-2-(4-phenylbenzenesulfonamido) propanamide (BiPS), suppresses skin injury induced by sulfur mustard

Sulfur mustard (SM) is a highly toxic blistering agent thought to mediate its action, in part, by activating matrix metalloproteinases (MMPs) in the skin and disrupting components of the basement membrane zone (BMZ). Type IV collagenases (MMP-9) degrade type IV collagen in the skin, a major component of the BMZ at the dermal-epidermal junction. In the present studies, a type IV collagenase inhibitor, N-hydroxy-3-phenyl-2-(4-phenylbenzenesulfonamido) propanamide (BiPS), was tested for its ability to protect the skin against injury induced by SM in the mouse ear vesicant model. SM induced inflammation, epidermal hyperplasia and microblistering at the dermal/epidermal junction of mouse ears 24-168 h post-exposure. This was associated with upregulation of MMP-9 mRNA and protein in the skin. Dual immunofluorescence labeling showed increases in MMP-9 in the epidermis and in the adjacent dermal matrix of the SM injured skin, as well as breakdown of type IV collagen in the basement membrane. Pretreatment of the skin with BiPS reduced signs of SM-induced cutaneous toxicity; expression of MMP-9 mRNA and protein was also downregulated in the skin by BiPS. Following BiPS pretreatment, type IV collagen appeared intact and was similar to control skin. These results demonstrate that inhibiting type IV collagenases in the skin improves basement membrane integrity after exposure to SM. BiPS may hold promise as a potential protective agent to mitigate SM induced skin injury.

Matrix Metalloproteinases' Role in Tumor Microenvironment

Cancer cells evolve in the tumor microenvironment (TME) by the acquisition of characteristics that allow them to initiate their passage through a series of events that constitute the metastatic cascade. For this purpose, tumor cells maintain a crosstalk with TME non-neoplastic cells transforming them into their allies. "Corrupted" cells such as cancer-associated fibroblasts (CAFs), tumor-associated macrophages (TAMs), and tumor-associated neutrophils (TANs) as well as neoplastic cells express and secrete matrix metalloproteinases (MMPs). Moreover, TME metabolic conditions such as hypoxia and acidification induce MMPs' synthesis in both cancer and stromal cells. MMPs' participation in TME consists in promoting events, for example, epithelial-mesenchymal transition (EMT), apoptosis resistance, angiogenesis, and lymphangiogenesis. MMPs also facilitate tumor cell migration through the basement membrane (BM) and extracellular matrix (ECM). The aim of the present chapter is to discuss MMPs' contribution to the evolution of cancer cells, their cellular origin, and their influence in the main processes that take place in the TME.

Therapeutic potential of curcumin in eye diseases

Curcumin (diferuloylmethane) derived from the rhizome of Curcuma longa L. has been used for thousands of years in traditional Chinese medicine and Ayurvedic medicine in Asian countries to treat liver diseases, rheumatoid diseases, diabetes, atherosclerosis, infectious diseases and cancer. It exhibits a wide range of pharmacological properties, which include antioxidant, anti-inflammatory, antimutagenic, antimicrobial and anticancer activity. Herein the mechanisms of curcumin impact on oxidative stress, angiogenesis and inflammatory processes are described indicating that curcumin use may inhibit those pathological conditions and restore body homeostasis. Its effectiveness was also proved for major eye diseases. In this review, the influence of curcumin on eye diseases, such as glaucoma, cataract, age-related macular degeneration, diabetic retinopathy, corneal neovascularization, corneal wound healing, dry eye disease, conjunctivitis, pterygium, anterior uveitis are reported. The analysis of a number of clinical and preclinical investigations indicates that curcumin may be used as a therapeutic agent in the treatment of various eye disorders.

Matrix metalloproteinases participation in the metastatic process and their diagnostic and therapeutic applications in cancer

Matrix metalloproteinases (MMPs) participate from the initial phases of cancer onset to the settlement of a metastatic niche in a second organ. Their role in cancer progression is related to their involvement in the extracellular matrix (ECM) degradation and in the regulation and processing of adhesion and cytoskeletal proteins, growth factors, chemokines and cytokines. MMPs participation in cancer progression makes them an attractive target for cancer therapy. MMPs have also been used for theranostic purposes in the detection of primary tumor and metastatic tissue in which a particular MMP is overexpressed, to follow up on therapy responses, and in the activation of cancer cytotoxic pro-drugs as part of nano-delivery-systems that increase drug concentration in a specific tumor target. Herein, we review MMPs molecular characteristics, their synthesis regulation and enzymatic activity, their participation in the metastatic process, and how their functions have been used to improve cancer treatment.

Folic acid inhibits colorectal cancer cell migration

We recently showed that folic acid (FA) could decrease the proliferation rate of colorectal cancer cells in vitro and reduce the volume of COLO-205 tumor in vivo. Since cancer cell proliferation and migration are two major events during cancer development, we further examined whether FA could also affect the migration of colorectal cancer cells. Transwell invasion assays demonstrated that FA reduced the invasion ability of colorectal cancer cell lines, COLO-205, LoVo and HT-29. Using COLO-205 as a cell model, we further delineated the molecular mechanism underlying FA-inhibited colorectal cancer cell invasion. Western blot analyses showed that FA (10 μM) activated cSrc, ERK1/2, NFκB, and p27 at serine 10 (Ser10), and up-regulated p53, p27, and KIS protein. Subcellular fractionation illustrated that FA treatment increased cytosolic translocation of p27, formation of the p27-RhoA complex, and RhoA degradation. The FA-induced migration inhibition in COLO-205 was abolished by blockade of the cSrc or ERK1/2 activity, knockdown of p27 or KIS using the siRNA technique, or over-expression of a constitutive active RhoA cDNA. Our results suggest that FA up-regulated p27 through increasing the cSrc/ERK1/2/NFκB/p53-mediated pathway. In the nucleus, FA up-regulated KIS, which in turn increased p27 phosphorylation at serine 10 (Ser10), subsequently resulting in cytosolic translocation of p27 and forming the p27-RhoA complex, thereby causing RhoA degradation, and eventually inhibited COLO-205 cell migration. Together with our previous findings suggest that FA reduced colorectal cancer development through inhibiting colorectal cancer cell proliferation and migration.

Luteolin inhibits angiogenesis of the M2‑like TAMs via the downregulation of hypoxia inducible factor‑1α and the STAT3 signalling pathway under hypoxia

The imbalance between angiogenic inducers and inhibitors appears to be a critical factor in tumour pathogenesis. Angiogenesis serves a key role in the occurrence, invasion and metastasis of tumours. Macrophages are a major cellular component of human and rodent tumours, where they are usually termed tumour‑associated macrophages (TAMs). In malignant tumours, TAMs tend to resemble alternatively activated macrophages (M2‑like), promote TA angiogenesis, strengthen tumour migration and invasive abilities, and simultaneously inhibit antitumor immune responses. In our previous study, luteolin, commonly found in a wide variety of plants, had a strong antitumor effect under normoxia; however, it is unknown whether luteolin serves a similar role under hypoxia. In the present study, cobalt chloride (CoCl2) was used to simulate hypoxia. Hypoxia‑inducible factor‑1α (HIF‑1α), which is difficult to detect under normoxic conditions, was significantly increased. Additionally, vascular endothelial growth factor (VEGF) was also significantly increased in response to CoCl2 treatment. Subsequently, luteolin was applied with CoCl2 to examine the effects of luteolin. Luteolin decreased the expression of VEGF and matrix metalloproteinase‑9, which promote angiogenesis. In addition, luteolin also suppressed the activation of HIF‑1 and phosphorylated‑signal transducer and activator of transcription 3 (STAT3) signalling, particularly within the M2‑like TAMs. The results of the present study provide novel evidence that luteolin, under hypoxic conditions, has a strong anticancer effect via the HIF‑1α and STAT3 signalling pathways.

Scarring vs. functional healing: Matrix-based strategies to regulate tissue repair

All vertebrates possess mechanisms to restore damaged tissues with outcomes ranging from regeneration to scarring. Unfortunately, the mammalian response to tissue injury most often culminates in scar formation. Accounting for nearly 45% of deaths in the developed world, fibrosis is a process that stands diametrically opposed to functional tissue regeneration. Strategies to improve wound healing outcomes therefore require methods to limit fibrosis. Wound healing is guided by precise spatiotemporal deposition and remodelling of the extracellular matrix (ECM). The ECM, comprising the non-cellular component of tissues, is a signalling depot that is differentially regulated in scarring and regenerative healing. This Review focuses on the importance of the native matrix components during mammalian wound healing alongside a comparison to scar-free healing and then presents an overview of matrix-based strategies that attempt to exploit the role of the ECM to improve wound healing outcomes.

Decellularized Adipose Tissue Scaffolds for Soft Tissue Regeneration and Adipose-Derived Stem/Stromal Cell Delivery

Surgically discarded adipose tissue is not only an abundant source of multipotent adipose-derived stem/stromal cells (ASCs) but can also be decellularized to obtain a biomimetic microenvironment for tissue engineering applications. The decellularization methods involve processing excised fat through a series of chemical, mechanical, and enzymatic treatment stages designed to extract cells, cellular components, and lipid from the tissues. This process yields a complex 3D bioscaffold enriched in collagens that mimics the biochemical and biomechanical properties of the native extracellular matrix (ECM). For ASC culture and delivery, decellularized adipose tissue (DAT) provides a cell-supportive platform that is conducive to adipogenesis. While DAT can be applied in its intact form as an off-the-shelf adipogenic matrix, it can also be used as an ECM source for the fabrication of an array of other scaffold formats including adipose ECM-derived microcarriers and porous foams. In this chapter, we describe the methods developed in our lab to decellularize human adipose tissue and to further process it into a variety of scaffolding materials for a range of applications in soft tissue regeneration, wound healing, and cell culture.

Vascularisation for cardiac tissue engineering: the extracellular matrix

Cardiovascular diseases present a major socio-economic burden. One major problem underlying most cardiovascular and congenital heart diseases is the irreversible loss of contractile heart muscle cells, the cardiomyocytes. To reverse damage incurred by myocardial infarction or by surgical correction of cardiac malformations, the loss of cardiac tissue with a thickness of a few millimetres needs to be compensated. A promising approach to this issue is cardiac tissue engineering. In this review we focus on the problem of in vitro vascularisation as implantation of cardiac patches consisting of more than three layers of cardiomyocytes (> 100 μm thick) already results in necrosis. We explain the need for vascularisation and elaborate on the importance to include non-myocytes in order to generate functional vascularised cardiac tissue. We discuss the potential of extracellular matrix molecules in promoting vascularisation and introduce nephronectin as an example of a new promising candidate. Finally, we discuss current biomaterial- based approaches including micropatterning, electrospinning, 3D micro-manufacturing technology and porogens. Collectively, the current literature supports the notion that cardiac tissue engineering is a realistic option for future treatment of paediatric and adult patients with cardiac disease.

Fragments generated upon extracellular matrix remodeling: Biological regulators and potential drugs

The remodeling of the extracellular matrix (ECM) by several protease families releases a number of bioactive fragments, which regulate numerous biological processes such as autophagy, angiogenesis, adipogenesis, fibrosis, tumor growth, metastasis and wound healing. We review here the proteases which generate bioactive ECM fragments, their ECM substrates, the major bioactive ECM fragments, together with their biological properties and their receptors. The translation of ECM fragments into drugs is challenging and would take advantage of an integrative approach to optimize the design of pre-clinical and clinical studies. This could be done by building the contextualized interaction network of the ECM fragment repertoire including their parent proteins, remodeling proteinases, and their receptors, and by using mathematical disease models.

Cell Based Therapeutic Approach in Vascular Surgery: Application and Review

Multipotent stem cells - such as mesenchymal stem/stromal cells and stem cells derived from different sources like vascular wall are intensely studied to try to rapidly translate their discovered features from bench to bedside. Vascular wall resident stem cells recruitment, differentiation, survival, proliferation, growth factor production, and signaling pathways transduced were analyzed. We studied biological properties of vascular resident stem cells and explored the relationship from several factors as Matrix Metalloproteinases (MMPs) and regulations of biological, translational and clinical features of these cells. In this review we described a translational and clinical approach to Adult Vascular Wall Resident Multipotent Vascular Stem Cells (VW-SCs) and reported their involvement in alternative clinical approach as cells based therapy in vascular disease like arterial aneurysms or peripheral arterial obstructive disease.

Regulation of Matrix Metalloproteinase in the Pathogenesis of Diabetic Retinopathy

Diabetic retinopathy, a progressive disease, is the major cause of acquired blindness in the developed countries. Despite cutting-edge research in the field, the exact mechanism of this multifactorial disease remains elusive. Matrix metalloproteinases (MMPs) degrade extracellular matrix and play significant role in regulating intracellular homeostasis. In the pathogenesis of diabetic retinopathy, activation of gelatinase MMPs (MMP-2 and MMP-9) in the retina is an early event, and activated MMPs damage the mitochondria and augment retinal capillary cell apoptosis, a phenomenon which is observed before histopathology characteristic of diabetic retinopathy can be seen. MMPs are regulated by a number of different mechanisms including cleavage of their zymogens, regulation of their tissue inhibitors, and their gene expressions by transcriptional factors and epigenetic modifications. This chapter reviews the current literature about the role of MMPs in the development of diabetic retinopathy, and describes different mechanisms to regulate their activation. With evolving research implicating MMPs in both preneovascularization and neovascularization stages of diabetic retinopathy, they could be an attractive target to inhibit the development/progression of diabetic retinopathy, a disease which has potential to rob vision during the most productive years of a diabetic patient's life.

Niclosamide inhibits the inflammatory and angiogenic activation of human umbilical vein endothelial cells

OBJECTIVE

Niclosamide is known to have anti-cancer and anti-inflammatory activities; however, its therapeutic mechanism has not been defined. In this study, to explain the therapeutic mechanism of niclosamide, we examined the effect of niclosamide on endothelial cell activation,leukocyte integration, proliferation, migration and angiogenesis in vitro.

METHODS

Endothelia-leukocyte adhesion assays were used to assess primary cultures of human umbilical vein endothelial cells’ (HUVECs) activation following TNF-α treatment. Each step of angiogenesis was evaluatedin vitro, including endothelial cell proliferation, migration and tube formation. Proliferation was examined using EdU assays, while wound migration assays and transwell assays were used to evaluate cell migration; cord like structure formation assays on Matrigel were used to assess tube formation. In vivo matrigel plug assay was used to assess angiogenesis. The protein expression was measured using western blot.

RESULTS

Niclosamide reduced the adhesion of human monocyte cells to HUVECs. Niclosamide also reduced protein expression of VCAM-1 and ICAM1 in HUVECs.Niclosamide significantly inhibited HUVEC proliferation,migration and cord-like structure formation. Niclosamide also suppresses VEGF-induced angiogenesis in vivo.Niclosamide attenuated IKK-mediated activation of NF-κB pathway in TNFα-induced endothelial cells. Niclosamide also suppresses VEGF-induced endothelial VEGFR2 activation and downstream P-AKT, P-mTOR and P-p70S6K.

CONCLUSIONS

Niclosamide exerted a potent effect on HUVECs activation, suggesting that it might function via an endothelia-based mechanism in the treatment of various diseases, including rheumatoid arthritis and cancer.

PDIA6 regulation of ADAM17 shedding activity and EGFR-mediated migration and invasion of glioblastoma cells

OBJECTIVE

In patients with glioblastoma, local invasion of tumor cells causes recurrence and shortens survival. The goal of this study was to determine whether protein disulfide isomerase (PDI) A6 regulates migration and invasion of glioblastoma cells and the associated factors.

METHODS

U87MG cells were treated with either PDIA6 or ADAM17 small interfering RNA (siRNA) fragments or with both types of siRNA fragments, and expression was confirmed by reverse transcription–polymerase chain reaction and Western blot. Migration and invasion were assessed using a wound-healing assay, a Matrigel assay, and an organotypic culture system. After the U87MG cells were treated with siRNAs and epidermal growth factor receptor (EGFR) inhibitors, the expression of matrix metalloproteinase–2 (MMP-2), membrane Type 1-matrix metalloproteinase (MT1-MMP), integrin, phosphorylated focal adhesion kinase (pFAK), and phosphorylated EGFR (pEGFR) was detected by Western blotting and zymography.

RESULTS

U87MG cell migration and invasion increased significantly after inhibition of PDIA6. The MMP-2 activation ratio and ADAM17 activity (as a sheddase of the proligand) increased, and expression of pEGFR, pFAK, integrin α5β3, and MT1-MMP was induced, compared with control levels. Furthermore, heparin-binding epidermal growth factor (EGFR signaling ligand) was highly expressed in PDIA6-knockdown cells. After siPDIA6-transfected U87MG cells were treated with EGFR signaling inhibitors, expression of pFAK, MMP-2, and MT1-MMP decreased and invasion decreased significantly. Simultaneous double-knockdown of PDIA6 and ADAM17 reduced pEGFR and pFAK expression, compared with control levels.

CONCLUSIONS

The authors propose that inhibiting PDIA6 could transduce EGFR signaling by activating and inducing ADAM17 during migration and invasion of U87MG glioblastoma cells. The results of this study suggest that PDIA6 is an important component of EGFR-mediated migration and invasion of U87MG cells. This is the first report of the effects of PDIA6 on migration and invasion in glioblastoma.

The Elastin Receptor Complex: A Unique Matricellular Receptor with High Anti-tumoral Potential

Elastin, one of the longest-lived proteins, confers elasticity to tissues with high mechanical constraints. During aging or pathophysiological conditions such as cancer progression, this insoluble polymer of tropoelastin undergoes an important degradation leading to the release of bioactive elastin-derived peptides (EDPs), named elastokines. EDP exhibit several biological functions able to drive tumor development by regulating cell proliferation, invasion, survival, angiogenesis, and matrix metalloproteinase expression in various tumor and stromal cells. Although, several receptors have been suggested to bind elastokines (α_vβ₃ and α_vβ₅ integrins, galectin-3), their main receptor remains the elastin receptor complex (ERC). This heterotrimer comprises a peripheral subunit, named elastin binding protein (EBP), associated to the protective protein/cathepsin A (PPCA). The latter is bound to a membrane-associated protein called Neuraminidase-1 (Neu-1). The pro-tumoral effects of elastokines have been linked to their binding onto EBP. Additionally, Neu-1 sialidase activity is essential for their signal transduction. Consistently, EDP-EBP interaction and Neu-1 activity emerge as original anti-tumoral targets. Interestingly, besides its direct involvement in cancer progression, the ERC also regulates diabetes outcome and thrombosis, an important risk factor for cancer development and a vascular process highly increased in patients suffering from cancer. In this review, we will describe ERC and elastokines involvement in cancer development suggesting that this unique receptor would be a promising therapeutic target. We will also discuss the pharmacological concepts aiming at blocking its pro-tumoral activities. Finally, its emerging role in cancer-associated complications and pathologies such as diabetes and thrombotic events will be also considered.

The NC11 domain of human collagen XVI induces vasculogenic mimicry in oral squamous cell carcinoma cells

Collagen XVI, a fibril-associated collagen with interrupted triple helix (FACIT) collagen, is involved in oral squamous cell carcinoma (OSCC) and glioblastoma progression. The NC11 domain of collagen XVI has been described previously with a strong implication in physiological processes. We detected the non-collagenous (NC) 11-domain in supernatants of OSCC cells after recombinant expression of full-length collagen XVI and in sera from OSCC patients and healthy individuals. Stable expression of NC11-green fluorescent protein (GFP) fusion protein in OSCC cells initiated proliferation control and block of anchorage-independent growth. Moreover, the NC11 domain triggered the generation of tubular-like net structures on laminin-rich matrix in contrast to mock-GFP control cells and cells expressing full-length collagen XVI. Taqman® quantitative PCR and diaminobenzidine staining in 2D- and 3D cell culture revealed a significantly increased gene and protein expression of VEGFR1, VEGFR2 and uPAR in recombinant NC11-GFP-expressing cells. Specific VEGF receptor inhibition with Axitinib or fetal calf serum heat inactivation prevented formation of tubular-like net structures. Accordantly, NC11-GFP coated culture slides led to an increase of focal adhesion contact formation and the upregulation of VEGFR1 and uPAR in three different non-transfected OSCC cell lines. In summary, we suggest that the NC11 domain of collagen XVI is a potential biomarker for OSCC and triggers vasculogenic mimicry via upregulation of endothelial receptors VEGFR1, VEGFR2 and uPAR in 2D- and 3D OSCC cell culture conditions.

Angiomodulatory properties of Rhodiola spp. and other natural antioxidants

Disturbances of angiogenesis and oxidative stress can lead to many serious diseases such as cancer, diabetes or ischemic heart disease. Substances neutralizing oxidative stress are known as antioxidants. They can affect angiogenesis process also, and thus, they modulate therapy results. Antioxidants become more and more frequently used in order to maintain homeostasis of the organism and diminish the risk of disease. Herein, we introduce some antioxidant preparations of natural plant origin (Rhodiola, Aloe vera, Resveratrol, Echinacea, Plumbagin) and antioxidant supplements (Padma 28, Reumaherb, Resvega). Analyses of their angiogenic properties, their multidirectional molecular effect on angiogenesis as well as medical application are within the scope of this review. Most of presented preparations down regulate neovascularization. They can be safely administered to patients with abnormally high angiogenesis. Rhodiola modulates, and Echinacea, Aloe vera and Plumbagin inhibit tumour-related angiogenesis in vitro and in vivo (animal models). Resveratrol and Resvega reduce neovascularization in the eye and may be applicable in eye disorders. Padma 28 preparation exhibits angioregulatory activity, decreasing high angiogenesis of cancer cells and increasing physiological angiogenesis, therefore can be used in therapy of patients with various disturbances of angiogenesis. Antioxidant application in the case of angiogenesis-related diseases should take into consideration angiogenic status of the patient.

The use of urinary bladder matrix in the treatment of trauma and combat casualty wound care

Treatment of combat injuries and resulting wounds can be difficult to treat due to compromised and evolving tissue necrosis, environmental contaminants, multidrug resistant microbacterial and/or fungal infections, coupled with microvascular damage and/or hypovascularized exposed vital structures. Our group has developed surgical care algorithms with identifiable salvage techniques to achieve stable, definitive wound coverage often with the aid of certain regenerative medicine biologic scaffold materials and advanced wound care to facilitate tissue coverage and healing. This case series reports on the role of urinary bladder matrix scaffolds in the wound care and reconstruction of traumatic and combat wounds. Urinary bladder matrix was found to facilitate definitive soft tissue reconstruction by establishing a neovascularized soft tissue base acceptable for second stage wound and skin coverage options within traumatic and combat-related wounds.

Adult vascular wall resident multipotent vascular stem cells, matrix metalloproteinases, and arterial aneurysms

Evidences have shown the presence of multipotent stem cells (SCs) at sites of arterial aneurysms: they can differentiate into smooth muscle cells (SMCs) and are activated after residing in a quiescent state in the vascular wall. Recent studies have implicated the role of matrix metalloproteinases in the pathogenesis of arterial aneurysms: in fact the increased synthesis of MMPs by arterial SMCs is thought to be a pivotal mechanism in aneurysm formation. The factors and signaling pathways involved in regulating wall resident SC recruitment, survival, proliferation, growth factor production, and differentiation may be also related to selective expression of different MMPs. This review explores the relationship between adult vascular wall resident multipotent vascular SCs, MMPs, and arterial aneurysms.

Pericellular proteolysis in cancer

Pericellular proteases have long been associated with cancer invasion and metastasis due to their ability to degrade extracellular matrix components. Recent studies demonstrate that proteases also modulate tumor progression and metastasis through highly regulated and complex processes involving cleavage, processing, or shedding of cell adhesion molecules, growth factors, cytokines, and kinases. In this review, we address how cancer cells, together with their surrounding microenvironment, regulate pericellular proteolysis. We dissect the multitude of mechanisms by which pericellular proteases contribute to cancer progression and discuss how this knowledge can be integrated into therapeutic opportunities.

Effects of ephrinB2 gene siRNA on the biological behavior of human colorectal cancer cells

Colorectal cancer (CRC) is a common gastrointestinal malignancy worldwide and is a lethal and aggressive malignancy with a dismal prognosis. EphrinB2 is a membrane-bound ligand and has an intracellular domain that also possesses an intrinsic signaling capacity called 'reverse signaling'. In the present study, CRC cell lines were screened for high expression of ephrinB2. Small interfering RNA (siRNA) knockdown of ephrinB2 was performed in human SW480 CRC cells. The levels of expression of ephrinB2, VEGF, CD105 and matrix metalloproteinase 9 (MMP9) protein were measured by western blotting, and messenger RNA (mRNA) levels were measured using real-time PCR. Apoptosis and cell cycle distribution were determined using flow cytometry. Cell proliferation was measured by a methyl thiazole tetrazolium (MTT) test and a scratch healing experiment was used to measure the extent of cell migration. A Transwell assay was used to detect the extent of cell invasion. The results showed that RNA interference (RNAi) of ephrinB2 effectively silenced the ephrinB2 gene at both the mRNA and protein levels in SW480 cells and inhibited the proliferation, invasion, migration and angiogenesis and induced apoptosis in SW480 cells. These effects may be attributed to VEGF and MMP9 regulation.

ADAMTS-4 and biglycan are expressed at high levels and co-localize to podosomes during endothelial cell tubulogenesis in vitro

Proteolysis of the extracellular matrix influences vascular growth. We examined the expression of ADAMTS-1, -4, and -5 metalloproteinases and their proteoglycan substrates versican, decorin, and biglycan as human umbilical vein endothelial cells (HUVECs) formed tubes within type I collagen gels in vitro. Tubulogenic and control HUVEC cultures expressed low levels of ADAMTS-1 and -5 mRNAs, but ADAMTS-4 mRNA was relatively abundant and was significantly elevated (as was ADAMTS-4 protein) in tubulogenic cultures versus controls. Immunocytochemistry revealed ADAMTS-4 in f-actin- and cortactin-positive podosome-like puncta in single cells and mature tubes. Tubulogenic and control cultures expressed low levels of versican and decorin mRNAs; however, peak levels of biglycan mRNA were 400- and 16,000-fold that of versican and decorin, respectively. Biglycan mRNA was highest at 3 hr, declined steadily through day 7 and, at 12 hr and beyond, was significantly lower in tubulogenic cultures than in controls. Western blots of extracellular matrix from tubulogenic cultures contained bands corresponding to biglycan and its cleavage products. By immunocytochemistry, biglycan was found in the pericellular matrix surrounding endothelial tubes and in cell-associated puncta that co-localized with ADAMTS-4 and cortactin. Collectively, our results suggest that ADAMTS-4 and its substrate biglycan are involved in tubulogenesis by endothelial cells.

Interactions of the Extracellular Matrix and Progenitor Cells in Cutaneous Wound Healing

SIGNIFICANCE

Both chronic wounds and excessive scar formation after cutaneous injury create a formidable clinical problem resulting in considerable morbidity and healthcare expenditure. The deposition and remodeling of extracellular matrix (ECM) components are critical processes in cutaneous healing. Understanding the role of the ECM in directing progenitor and reparative cell fate and activities during wound repair is required to improve wound-care strategies.

RECENT ADVANCES

In addition to providing structural integrity, the ECM is recognized to play critical roles in regulating progenitor and reparative cell behaviors such as migration, differentiation, proliferation, and survival. The ECM dictates these activities through its binding of adhesion receptors as well as its ability to regulate growth factor bioavailability and signaling. More recently, a key role for mechanical control of cell fate through interaction with the ECM has emerged.

CRITICAL ISSUES

Despite significant advances in understanding the pathophysiology of cutaneous wound repair, problematic wounds remain a significant healthcare challenge. Regenerative medical strategies that either target endogenous stem cells or utilize applications of exogenous stem cell populations have emerged as promising approaches to pathologic wounds. However, the identification of smart biomaterials and matrices may allow for further optimization of such therapies.

FUTURE DIRECTIONS

An efficient and appropriate healing response in the skin postinjury is regulated by a fine balance of the quantity and quality of ECM proteins. A more complete understanding of ECM regulation of the cell fate and activities during cutaneous wound repair is vital for the development of novel treatment strategies for improvement of cutaneous healing.

Thy-1-induced migration inhibition in vascular endothelial cells through reducing the RhoA activity

Our previous study indicated that Thy-1, which is expressed on blood vessel endothelium in settings of pathological and a specific of physiological, but not during embryonic, angiogenesis, may be used as a marker for angiogenesis. However, the function of Thy-1 during angiogenesis is still not clear. Here, we demonstrate that knock-down of the endogenous Thy-1 expression by Thy-1 siRNA transfection promoted the migration of human umbilical vein endothelial cells (HUVEC). In contrast, treatment with interleukin-1β (IL-1β) or phorbol-12-myristate-13-acetate (PMA) increased the level of Thy-1 protein and reduced the migration of HUVEC. These effects were abolished by pre-transfection of HUVEC with Thy-1 siRNA to knock-down the expression of Thy-1. Moreover, over-expression of Thy-1 by transfection of HUVEC with Thy-1 pcDNA3.1 decreased the activity of RhoA and Rac-1 and inhibited the adhesion, migration and capillary-like tube formation of these cells. These effects were prevented by co-transfection of the cell with constitutively active RhoA construct (RhoA V14). On the other hand, pre-treatment with a ROCK (a kinase associated with RhoA for transducing RhoA signaling) inhibitor, Y27632, abolished the RhoA V14-induced prevention effect on the Thy-1-induced inhibition of endothelial cell migration and tube formation. Taken together, these results indicate that suppression of the RhoA-mediated pathway might participate in the Thy-1-induced migration inhibition in HUVEC. In the present study, we uncover a completely novel role of Thy-1 in endothelial cell behaviors.

Luteolin inhibits human prostate tumor growth by suppressing vascular endothelial growth factor receptor 2-mediated angiogenesis

Angiogenesis, the formation of new blood vessels from pre-existing vascular beds, is essential for tumor growth, invasion, and metastasis. Luteolin is a common dietary flavonoid found in fruits and vegetables. We studied the antiangiogenic activity of luteolin using in vitro, ex vivo, and in vivo models. In vitro studies using rat aortic ring assay showed that luteolin at non-toxic concentrations significantly inhibited microvessel sprouting and proliferation, migration, invasion and tube formation of endothelial cells, which are key events in the process of angiogenesis. Luteolin also inhibited ex vivo angiogenesis as revealed by chicken egg chorioallantoic membrane assay (CAM) and matrigel plug assay. Gelatin zymographic analysis demonstrated the inhibitory effect of luteolin on the activation of matrix metalloproteinases MMP-2 and MMP-9. Western blot analysis showed that luteolin suppressed VEGF induced phosphorylation of VEGF receptor 2 and their downstream protein kinases AKT, ERK, mTOR, P70S6K, MMP-2, and MMP-9 in HUVECs. Proinflammatory cytokines such as IL-1β, IL-6, IL-8, and TNF-α level were significantly reduced by the treatment of luteolin in PC-3 cells. Luteolin (10 mg/kg/d) significantly reduced the volume and the weight of solid tumors in prostate xenograft mouse model, indicating that luteolin inhibited tumorigenesis by targeting angiogenesis. CD31 and CD34 immunohistochemical staining further revealed that the microvessel density could be remarkably suppressed by luteolin. Moreover, luteolin reduced cell viability and induced apoptosis in prostate cancer cells, which were correlated with the downregulation of AKT, ERK, mTOR, P70S6K, MMP-2, and MMP-9 expressions. Taken together, our findings demonstrate that luteolin inhibits human prostate tumor growth by suppressing vascular endothelial growth factor receptor 2-mediated angiogenesis.

Folic acid inhibits endothelial cell migration through inhibiting the RhoA activity mediated by activating the folic acid receptor/cSrc/p190RhoGAP-signaling pathway

Previously, our in vivo studies demonstrated that folic acid (FA) could inhibit angiogenesis and in vitro studies showed that FA reduced vascular endothelial cell proliferation through activating the cSrc/ERK-2/NFκB/p53 pathway mediated by FA receptor (FR). Here, we further examined the effect of FA on endothelial cell migration. Our results showed that FA (10 μM) inhibited the formation of lamellipodia, migration and capillary-like tube formation of human umbilical venous endothelial cells (HUVEC). These inhibition effects induced by FA treatment were not due to reduction of cell survival and cell adhesion on the collagen-coated plate. Treatment of HUVEC with FA (10 μM) increased the activity of cSrc and p190RhoGAP and decreased the activity of RhoA. Over-expression of the constitutively active RhoA construct (RhoA V14) prevented the FA-induced inhibition of migration and capillary-like tube formation in HUVEC. However, these preventive effects were abolished by pretreatment of HUVEC with a ROCK inhibitor, Y27632. Pretreatment with a cSrc inhibitor, PP2, prevented the FA-induced activation of p190GAP, reduction of the RhoA activity and migration inhibition in HUVEC. Moreover, pre-transfection with p190RhoGAP siRNA abolished the FA-induced reduction in the RhoA activity and migration inhibition in HUVEC. Taken together, our results suggest that FA might inhibit endothelial cell migration through inhibiting the RhoA activity mediated by activating the FR/cSrc/p190RhoGAP-signaling pathway. These findings further support the anti-angiogenic activity of FA.

Endostatin Gene Therapy for Endometriosis in Rats

Objective:

Endostatin gene therapy for endometriosis was studied in an experimental autotransplantation model in rats.

Methods:

Endometriotic lesions were transfected by intralesional injection of the plasmid lipofectamine-endostatinpBud (group 1), lipofectamine-pBud (empty vector; group 2) or phosphatebuffered saline (group 3). Endostatin mRNA and protein levels in lesions were evaluated by quantitative real-time reverse transcription-polymerase chain reaction and Western blot analysis. Endostatin and vascular endothelial growth factor (VEGF) protein levels in serum, and microvessel density (MVD) and matrix metalloproteinase (MMP)-2 protein levels in endometriotic lesions, were also determined.

Results:

Lipofectamine- endostatin-pBud injection increased endostatin mRNA and protein levels in lesions. Lesions were significantly smaller, and serum VEGF levels significantly lower, in group 1 versus controls. Serum VEGF was significantly and negatively correlated with serum endostatin. In group 1, MMP-2 levels and MVD were significantly lower versus controls. MMP-2 level was negatively correlated with endostatin.

Conclusions:

Gene therapy with endostatin appears to be an effective treatment for endometriosis. Restoration of endostatin gene expression by gene transfer in vivo might be a potential gene therapy approach for human endometriosis.

Novel cardiac-specific biomarkers and the cardiovascular continuum

The concept of the cardiovascular continuum, introduced during the early 1990s, created a holistic view of the chain of events connecting cardiovascular-related risk factors with the progressive development of pathological-related tissue remodelling and ultimately, heart failure and death. Understanding of the tissue-specific changes, and new technologies developed over the last 25-30 years, enabled tissue remodelling events to be monitored in vivo and cardiovascular disease to be diagnosed more reliably than before. The tangible product of this evolution was the introduction of a number of biochemical markers such as troponin I and T, which are now commonly used in clinics to measure myocardial damage. However, biomarkers that can detect specific earlier stages of the cardiovascular continuum have yet to be generated and utilised. The majority of the existing markers are useful only in the end stages of the disease where few successful intervention options exist. Since a large number of patients experience a transient underlying developing pathology long before the signs or symptoms of cardiovascular disease become apparent, the requirement for new markers that can describe the early tissue-specific, matrix remodelling process which ultimately leads to disease is evident. This review highlights the importance of relating cardiac biochemical markers with specific time points along the cardiovascular continuum, especially during the early transient phase of pathology progression where none of the existing markers aid diagnosis.

Endometriosis, angiogenesis and tissue factor

Tissue factor (TF), is a cellular receptor that binds the factor VII/VIIa to initiate the blood coagulation cascade. In addition to its role as the initiator of the hemostatic cascade, TF is known to be involved in angiogenesis via intracellular signaling that utilizes the protease activated receptor-2 (PAR-2). We now review the physiologic expression of TF in the endometrium and its altered expression in multiple cell types derived from eutopic and ectopic endometrium from women with endometriosis compared with normal endometrium. Our findings suggest that TF might be an ideal target for therapeutic intervention in endometriosis. We have employed a novel immunoconjugate molecule known as Icon and were able to eradicate endometrial lesions in a mouse model of endometriosis without affecting fertility. These findings have major implications for potential treatment in humans.

Integrin-mediated cell-matrix interaction in physiological and pathological blood vessel formation

Physiological as well as pathological blood vessel formation are fundamentally dependent on cell-matrix interaction. Integrins, a family of major cell adhesion receptors, play a pivotal role in development, maintenance, and remodeling of the vasculature. Cell migration, invasion, and remodeling of the extracellular matrix (ECM) are integrin-regulated processes, and the expression of certain integrins also correlates with tumor progression. Recent advances in the understanding of how integrins are involved in the regulation of blood vessel formation and remodeling during tumor progression are highlighted. The increasing knowledge of integrin function at the molecular level, together with the growing repertoire of integrin inhibitors which allow their selective pharmacological manipulation, makes integrins suited as potential diagnostic markers and therapeutic targets.

Dermal substitute-assisted healing: enhancing stem cell therapy with novel biomaterial design

The use of dermal substitutes is increasingly widespread but the outcomes of substitute-assisted healing remain functionally deficient. Presently, the most successful scaffolds are acellular polymer matrices, prepared through lyophilization and phase separation techniques, designed to mimic the dermal extracellular matrix. The application of scaffolds containing viable cells has proven to be problematic due to short shelf-life, high cost and death of transplanted cells as a result of immune rejection and apoptosis. Recent advances in biomaterial science have made new techniques available capable of increasing scaffold complexity, allowing the creation of 3D microenvironments that actively control cell behaviour. Importantly, it may be possible through these sophisticated novel techniques, including bio-printing and electrospinning, to accurately direct stem cell behaviour. This complex proposal involves the incorporation of cell-matrix, cell-cell, mechanical cues and soluble factors delivered in a spatially and temporally pertinent manner. This requires accurate modelling of three-dimensional stem cell interactions within niche environments to identify key signalling molecules and mechanisms. The application of stem cells within substitutes containing such environments may result in greatly improved transplanted cell viability. Ultimately this may increase cellular organization and complexity of skin substitutes. This review discusses progress made in improving the efficacy of cellular dermal substitutes for the treatment of cutaneous defects and the potential of evolving new technology to improve current results.

Bioactive peptides derived from vascular endothelial cell extracellular matrices promote microvascular morphogenesis and wound healing in vitro

Studies in our laboratory indicate that collagenase from Clostridium histolyticum promotes endothelial cell and keratinocyte responses to injury in vitro and wound healing in vivo. We postulate that matrix degradation by Clostridial collagenase creates bioactive fragments that can stimulate cellular responses to injury and angiogenesis. To test this hypothesis, we performed limited digestion of defined capillary-endothelial-derived extracellular matrices using purified human or bacterial collagenases. Immunoprecipitation with antibodies recognizing collagens I, II, III, IV, and V, followed by mass spectrometry reveals the presence of unique fragments in bacterial, but not human-enzyme-digested matrix. Results show that there are several bioactive peptides liberated from Clostridial collagenase-treated matrices, which facilitate endothelial responses to injury, and accelerate microvascular remodeling in vitro. Fragments of collagen IV, fibrillin-1, tenascin X, and a novel peptide created by combining specific amino acids contained within fibrillin 1 and tenascin X each have profound proangiogenic properties. The peptides used at 10-100 nM increase rates of microvascular endothelial cell proliferation by up to 47% and in vitro angiogenesis by 200% when compared with serum-stimulated controls. Current studies are aimed at revealing the molecular mechanisms regulating peptide-induced wound healing while extending these in vitro observations using animal modeling.

The clinical effectiveness in wound healing with extracellular matrix derived from porcine urinary bladder matrix: a case series on severe chronic wounds

A study involving 3 patients was performed to evaluate the efficacy of Matristem, an extracellular matrix scaffold derived from the porcine urinary bladder matrix (UBM), to promote natural healing in patients with severe, chronic wounds that did not respond well to standard wound management. In all cases, the wounds closed after only a few weeks of repeated treatments with UBM, with all patients showing complete epithelialization of the wound with limited formation of scar tissue by 13 weeks after first treatment. These initial results suggest that UBM warrants further investigation for treatment of chronic nonhealing ulcers that are recalcitrant to standard wound therapies.

Effects of major human antiprotease alpha-1-antitrypsin on the motility and proliferation of stromal cells from human exfoliated deciduous teeth

AIM

Intrinsic tissue regeneration mechanisms are still not fully understood. The destruction/reconstruction processes are usually in fine balance; however, this can be easily destroyed, for example in the environment of chronic inflammation. One of the major proteins present at the inflammatory sites is the multifunctional protein alpha-1-antitrypsin (AAT). In this study, potential therapeutic effects of this major human antiprotease on progenitor cells are assessed.

MATERIALS & METHODS

Stromal cells from human exfoliated deciduous teeth (SHEDs) were used, which are similar to the mesenchymal stromal cells isolated from other tissues. SHEDs were cultivated in the presence of subphysiological, physiological and inflammatory concentrations of AAT, and their proliferation and motility traits were assayed. Some intracellular signaling pathways, AAT internalization by SHEDs and their matrix metalloprotease profile were studied in parallel.

RESULTS

Physiologic and inflammatory concentrations of AAT significantly increased the cell proliferation rate, induced phosphorylation of several key protein kinases and increased the amount of secreted active gelatinases. Moreover, cells exposed to physiologic and inflammatory levels of AAT were able to invade and migrate more efficiently. Subphysiologic AAT levels did not change cell behavior significantly.

CONCLUSION

AAT at physiologic and inflammatory concentrations positively modulates the proliferation and motility of SHEDs in vitro. These results suggest the importance of AAT in the maintenance and regulation of tissue progenitor cells in vivo.

Ocular angiogenesis: mechanisms and recent advances in therapy

Ocular angiogenesis, the formation of new blood vessels from the existing vascular tree, is an important cause for severe loss of vision. It can occur in a spectrum of ocular disorders such as age-related macular degeneration (AMD), diabetic retinopathy, retinal artery or vein occlusion, and retinopathy of prematurity (ROP). One of the underlying causes of vision loss in proliferative retinal diseases is the increased vascular permeability leading to retinal edema, vascular fragility resulting in hemorrhage, or fibrovascular proliferation with tractional and rhegmatogenous retinal detachment. Pro- and antiangiogenic factors regulate an "angiogenic switch," which when turned on, leads to the pathogenesis of the above ocular diseases. Although neovascularization tends to occur at a relatively late stage in the course of many ocular disorders, it is an attractive target for therapeutic intervention, since it represents a final common pathway in processes that are multifactorial in etiology and is the event that typically leads directly to visual loss. Identification of these angiogenesis regulators has enabled the development of novel therapeutic approaches. In this light, antibodies directed against common markers of neovasculature, expressed in different diseases, may open up a very general and widely applicable approach for diagnostic and therapeutic interventions. Local gene transfer, that is, the intraocular delivery of recombinant viruses carrying genes encoding angiostatic proteins and small interfering RNA (siRNA) against vascular endothelial growth factor (VEGF) and VEGF receptors, offers the possibility of targeted, sustained, and regulatable delivery of angiostatic proteins and other angiogenic regulators to the retina. Recent progress has enabled the planning of clinical trials of gene therapy for ocular neovascularization.

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.

Angiogenesis in Balb/c mice under beta-carotene supplementation in diet

Angiogenesis is a process of new blood vessel formation from pre-existing ones. The most important steps in angiogenesis include detachment, proliferation, migration, homing and differentiation of vascular wall cells, which are mainly endothelial cells and their progenitors. The study focused on the effect of beta-carotene (BC) supplementation (12,000 mg/kg) in the diet on angiogenesis in Balb/c mice. Female Balb/c mice were fed for 5 weeks with two different diets: with BC or without BC supplementation. After 4 weeks of feeding, Balb/c mice were injected subcutaneously with two matrigel plugs with or without basic fibroblast growth factor (bFGF). Six days later, the animals were killed, and the matrigel plugs were used for immunohistochemical staining with CD31 antibody and for gene expression analysis. Microarray and Real-Time PCR data showed down-regulation of genes involved in proliferation and up-regulation of genes encoding inhibitors of apoptosis, proteins regulating cell adhesion, matrix-degrading enzymes and proteins involved in the VEGF pathway. The results of this study demonstrated that BC proangiogenic activity (with or without bFGF) in vivo seemed to be more significantly associated with cells' protection from apoptosis and their stimulation of chemotaxis/homing than cell proliferation.

Chemoattraction of progenitor cells by remodeling extracellular matrix scaffolds

The chemotactic properties of a biologic scaffold composed of extracellular matrix (ECM) and subjected to in vivo degradation and remodeling were evaluated in a mouse model of Achilles tendon reconstruction. Following a segmental resection of the Achilles tendon in both C57BL/6 and MRL/MpJ mice, the defect was repaired with either an ECM scaffold composed of urinary bladder matrix (UBM) or resected autologous tendon. The surgically repaired and the contralateral tendons were harvested at 3, 7, and 14 days following surgery from each animal. Chemotaxis of multipotential progenitor cells toward the harvested tissue was quantified using a fluorescent-based cell migration assay. Results showed greater migration of progenitor cells toward tendons repaired with UBM-ECM scaffold compared to both the tendons repaired with autologous tissue and the normal contralateral tendon in both the MRL/MpJ and C57BL/6 mice. The magnitude and temporal pattern of the chemotactic response differed between the two mouse strains.