Systemic sclerosis stimulates angiogenesis in the chick embryo chorioallantoic membrane

Enhanced angiogenic potency of monocytic endothelial progenitor cells in patients with systemic sclerosis

Introduction

Microvasculopathy is one of the characteristic features in patients with systemic sclerosis (SSc), but underlying mechanisms still remain uncertain. In this study, we evaluated the potential involvement of monocytic endothelial progenitor cells (EPCs) in pathogenic processes of SSc vasculopathy, by determining their number and contribution to blood vessel formation through angiogenesis and vasculogenesis.

Methods

Monocytic EPCs were enriched and enumerated using a culture of peripheral blood mononuclear cells and platelets on fibronectin in 23 patients with SSc, 22 patients with rheumatoid arthritis (RA), and 21 healthy controls. To assess the capacity of monocytic EPCs to promote vascular formation and the contribution of vasculogenesis to this process, we used an in vitro co-culture system with human umbilical vein endothelial cells (HUVECs) on Matrigel^® and an in vivo murine tumor neovascularization model.

Results

Monocytic EPCs were significantly increased in SSc patients than in RA patients or healthy controls (P = 0.01 for both comparisons). Monocytic EPCs derived from SSc patients promoted tubular formation in Matrigel^® cultures more than those from healthy controls (P = 0.007). Transplantation of monocytic EPCs into immunodeficient mice resulted in promotion of tumor growth and blood vessel formation, and these properties were more prominent in SSc than healthy monocytic EPCs (P = 0.03 for both comparisons). In contrast, incorporation of SSc monocytic EPCs into the tubular structure was less efficient in vitro and in vivo, compared with healthy monocytic EPCs.

Conclusions

SSc patients have high numbers of aberrant circulating monocytic EPCs that exert enhanced angiogenesis but are impaired in vasculogenesis. However, these cells apparently cannot overcome the anti-angiogenic environment that characterizes SSc-affected tissues.

CD105 is a marker of tumour vasculature and a potential target for the treatment of head and neck squamous cell carcinoma

BACKGROUND

The importance of angiogenesis in solid tumour growth is well recognised. Tumour angiogenesis is considered the result of an imbalance between pro- and anti-angiogenic factors produced by both the malignancy and normal cells. Endoglin (CD105) is a proliferation-associated, hypoxia-inducible glycoprotein that seems to be clinically superior to other pan-endothelial markers in the selective evaluation of tumour angiogenesis. Several studies have revealed CD105 up-regulation in a wide range of tumour endothelia. Since 2002, endothelial CD105 expression has also been retrospectively investigated in patients with head and neck squamous cell carcinoma (HNSCC).

METHODS

An exhaustive literature review was performed to investigate available evidence on CD105 expression and its biological role and therapeutic potential in HNSCC.

RESULTS

The available evidence supports the hypothesis that CD105 expression in HNSCC may be a valuable parameter for pinpointing patients at greater risk of recurrent malignancy and with a worse prognosis. A high CD105 expression in HNSCC was associated with metastatic lymph nodes in most of the studies.

CONCLUSIONS

Prospective studies are mandatory to confirm that CD105 expression is a significant prognostic hallmark in HNSCC. The results of prospective studies could be relevant for the adoption of stricter follow-up protocols and/or alternative therapeutic regimens for patients with a high CD105 expression in HNSCC. Great interest is currently being focused on vascular targeting for therapeutic purposes. Preclinical studies on appropriate animal models resembling HNSCC to investigate the effects of inhibiting CD105 may show the efficacy of combined treatment strategies associating angiogenic-targeted with conventional therapies for HNSCC.

Cellular and molecular aspects of vascular dysfunction in systemic sclerosis

Systemic sclerosis (SSc) is characterized by vascular alterations, activation of the immune system and tissue fibrosis. Vascular insufficiency manifests early in the disease, and although there is evidence of an active repair process, capillaries deteriorate and regress. Factors that contribute to the failure of vascular regeneration might include persistent injury, an imbalance between proangiogenic and antiangiogenic mediators, intrinsic abnormal properties of the cellular components of the vessels, and the presence of fibroblast-derived antiangiogenic factors. In addition, circulating dysfunctional endothelial progenitor cells might further exacerbate vessel deterioration. Abnormal expression of transcription factors, including Fra2 and Fli1, has been proposed to contribute to SSc vasculopathy. Fli1 regulates genes that are involved in vessel maturation and stabilization, suggesting that reduced levels of Fli1 in SSc vasculature could contribute to the development of unstable vessels that are prone to regression. Conversely, proliferating endothelial cells and pericytes, in the presence of an appropriate stimulus, might transdifferentiate into collagen-producing cells, and thus contribute to the initiation of fibrosis. Despite progress in treating the symptoms of vascular disease in SSc, the underlying mechanisms remain poorly understood. An improved knowledge of the molecular and cellular pathways that contribute to SSc vasculopathy could help in the design of effective therapies in the future.

Mechanisms in the loss of capillaries in systemic sclerosis: angiogenesis versus vasculogenesis

Systemic sclerosis (SSc, scleroderma) is a chronic, multisystem connective tissue disorder affecting the skin and various internal organs. Although the disease is characterized by a triad of widespread microangiopathy, fibrosis and autoimmunity, increasing evidence indicates that vascular damage is a primary event in the pathogenesis of SSc. The progressive vascular injury includes persistent endothelial cell activation/damage and apoptosis, intimal thickening, delamination, vessel narrowing and obliteration. These profound vascular changes lead to vascular tone dysfunction and reduced capillary blood flow, with consequent tissue ischemia and severe clinical manifestations, such as digital ulceration or amputation, pulmonary arterial hypertension and scleroderma renal crisis. The resulting tissue hypoxia induces complex cellular and molecular mechanisms in the attempt to recover endothelial cell function and tissue perfusion. Nevertheless, in SSc patients there is no evidence of significant angiogenesis and the disease evolves towards chronic tissue ischemia, with progressive and irreversible structural changes in multiple vascular beds culminating in the loss of capillaries. A severe imbalance between pro-angiogenic and angiostatic factors may also lead to impaired angiogenic response during SSc. Besides insufficient angiogenesis, defective vasculogenesis with altered numbers and functional defects of bone marrow-derived endothelial progenitor cells may contribute to the vascular pathogenesis of SSc. The purpose of this article is to review the contribution of recent studies to the understanding of the complex mechanisms of impaired vascular repair in SSc. Indeed, understanding the pathophysiology of SSc-associated vascular disease may be the key in dissecting the disease pathogenesis and developing novel therapies. Either angiogenic or vasculogenic mechanisms may potentially become in the future the target of therapeutic strategies to promote capillary regeneration in SSc.

Bone marrow endothelial progenitors are defective in systemic sclerosis

OBJECTIVE

Vascular abnormalities represent the main component of the pathobiology of systemic sclerosis (SSc), progressing from structural derangements of the microcirculation with abortive neoangiogenesis to final vessel loss. Since circulating endothelial progenitor cells (EPCs) are important in the vascular repair process, we undertook this study to examine their numbers in the peripheral blood (PB) of SSc patients and to evaluate whether their status is related to impaired quantitative and/or qualitative aspects of the bone marrow (BM) microenvironment.

METHODS

Circulating EPCs from 62 SSc patients were evaluated by flow cytometry and characterized as CD45 negative and CD133 positive. BM EPCs, identified as CD133 positive, were isolated from 14 SSc patients and grown to induce endothelial differentiation. In addition, progenitor numbers and functional properties of hematopoietic and stromal compartments were analyzed by various assays.

RESULTS

We found that EPCs were detectable in the PB of patients with SSc, and their number was significantly increased in patients with early-stage disease but not in those with late-stage disease. All of the examined BM samples contained reduced numbers of EPCs and stromal cells, both of which were functionally impaired. Both endothelial and stromal progenitors expressed vascular endothelial growth factor receptor, indicating that BM is strongly induced to differentiate into the endothelial lineage; furthermore, only BM EPCs from patients with early disease led to endothelial differentiation in vitro.

CONCLUSION

This study provides the first demonstration that in SSc, there is a complex impairment in the BM microenvironment involving both the endothelial and mesenchymal stem cell compartments and that this impairment might play a role in defective vasculogenesis in scleroderma.

Differential kinetics of plasma CD105 and transforming growth factor beta expression early in human acute pancreatitis

OBJECTIVES

The interaction of transforming growth factor beta (TGF-beta) with CD105 (endoglin) is an essential step in the maintenance of endothelial cell quiescence. The importance of this interaction during the critical early phases of acute pancreatitis is unknown. This study explores patterns of expression of CD105 and TGF-beta in plasma during human acute pancreatitis.

METHODS

Forty-one patients with a clinical diagnosis of acute pancreatitis constitute the study population. Venous blood samples were taken at admission and on the fifth day. Enzyme-linked immunosorbent assay was performed for CD105, TGF-beta1, TGF-beta3, CD105/TGF-beta1, and CD105/TGF-beta3 complexes.

RESULTS

TGF-beta1 levels were significantly elevated on admission in the acute pancreatitis group compared with controls and were further elevated in delayed samples. In contrast, admission CD105 levels were similar to those in controls, but in delayed samples, there was a significant reduction in CD105. Levels of TGF-beta3, CD105/TGF-beta1, and CD105/TGF-beta3 did not differ between groups.

CONCLUSIONS

This is the first report to investigate the interplay between plasma expression of CD105, TGF-beta1, TGF-beta3, and ligand complexes in acute pancreatitis. The results of this study confirm previous findings that increased expression of TGF-beta1 is a feature of severe acute pancreatitis. The absence of a parallel elevation in CD105 or CD105/TGF-beta ligand complexes is previously unreported and may suggest that angiogenesis mediated by the interaction between CD105 and TGF-beta is not an early feature of this disease.

Matrix metalloproteinase 12-dependent cleavage of urokinase receptor in systemic sclerosis microvascular endothelial cells results in impaired angiogenesis

OBJECTIVE

Defective angiogenesis, resulting in tissue ischemia, is particularly prominent in the diffuse form of systemic sclerosis (SSc). The present study was undertaken to identify possible differences between normal and SSc microvascular endothelial cells (MVECs) in the expression of the cell-associated urokinase-type plasminogen activator (uPA)/uPA receptor (uPAR) system, which is critical in the angiogenic process.

METHODS

MVECs were isolated from the dermis of healthy individuals and from the dermis of patients with diffuse SSc. The uPA/uPAR system was examined at the protein and messenger RNA levels. Angiogenesis was assayed on Matrigel-coated porous filters and plates to evaluate cell proliferation, invasion, and capillary morphogenesis. Cleavage of uPAR and the activity of matrix metalloproteinase 12 (MMP-12) were evaluated by Western blotting.

RESULTS

Compared with MVECs from healthy skin, MVECs from SSc patients showed higher expression of uPAR. However, in SSc MVECs, uPAR undergoes truncation between domain 1 and domain 2, as shown by flow cytometry, enzyme-linked immunosorbent assay, and Western blotting, a cleavage that is known to impair uPAR functions. These properties of SSc MVECs were associated with poor spontaneous and uPA-dependent invasion, proliferation, and capillary morphogenesis. The uPAR cleavage occurring in SSc MVECs was associated with overexpression of MMP-12. SSc MVEC-conditioned medium impaired uPA-dependent proliferation and invasion as well as capillary morphogenesis in normal MVECs in vitro. Both a general hydroxamate inhibitor of MMP activity and anti-MMP-12 antibodies restored this SSc MVEC-induced impaired functioning.

CONCLUSION

Overproduction of MMP-12 by SSc MVECs accounts for the cleavage of uPAR and the impairment of angiogenesis in vitro and may contribute to reduced angiogenesis in SSc patients.

Angiogenic response induced by acellular brain scaffolds grafted onto the chick embryo chorioallantoic membrane

The repair and regeneration of injured tissues and organs depend on the re-establishment of the blood flow needed for cellular infiltration and metabolic support. Among the various materials used in tissue reconstruction, acellular scaffolds have recently been utilized. In this study, we investigated the angiogenic response induced by acellular brain scaffolds implanted in vivo onto the chick embryo chorioallantoic membrane (CAM), a useful model for such investigations. The results show that acellular brain scaffolds are able to induce a strong angiogenic response, comparable to that of fibroblast growth factor-2 (FGF-2), a well known angiogenic cytokine. The response may be considered dependent on a direct angiogenic effect exerted by the scaffold, because no inflammatory infiltrate was detectable in CAM's mesenchyme beneath the implant. Acellular brain scaffolds might induce the release of endogenous angiogenic factors, such as FGF-2 and vascular endothelial growth factor (VEGF) released from the extracellular matrix of the developing CAM. In addition, the angiogenic response may depend, in part, also on the presence in the acellular matrix of transforming growth factor beta 1 (TGFbeta1).

Disease-associated increased HIF-1, alphavbeta3 integrin, and Flt-1 do not suffice to compensate the damage-inducing loss of blood vessels in inflammatory myopathies

OBJECTIVE

To analyze the microvascular network in skeletal muscle biopsies from patients with dermatomyositis (DM) and systemic sclerosis (SSc) compared to polymyositis (PM) and systemic lupus erythematosus (SLE), and non-inflammatory myopathies, and to clarify whether reparative angiogenesis-related factors are expressed in parallel to blood vessel damage.

METHODS

Immunohistochemical staining of muscle biopsies (10 DM, 10 SSc, 10 PM, 10 SLE, and 10 non-inflammatory myopathies) with antibodies against von Willebrand factor (vWF), hypoxia-inducible factor-1beta (HIF-1beta), beta3 integrin subunit, and vascular endothelial growth factor receptor-1 (VEGFR-1). The TechMate staining robot and biotin-streptavidin protocol were used.

RESULTS

DM and SSc muscles were characterized by endothelial damage and reduction of blood vessel network. Expression of angiogenesis-related factors (HIF-1beta, beta3, VEGFR-1) was also found in the same biopsies. In contrast, in PM and SLE muscles, vascular networks were apparently not affected and angiogenic stimuli were less expressed if at all.

CONCLUSIONS

This work demonstrates that in inflamed muscles hypoxia/ischemia induces increased expression of angiogenic factors, yet their impact is insufficient to repair disease-associated reduction of the capillary network. This leads to questions considering the usefulness of angiogenic factors in the treatment of ischemic inflammatory myopathies in DM and SSc.

CD105 is important for angiogenesis: evidence and potential applications

Angiogenesis is the propelling force for tumor growth and metastasis, and antiangiogenic therapy represents one of the most promising modalities for cancer treatment. CD105 (endoglin) is a proliferation-associated and hypoxia-inducible protein abundantly expressed in angiogenic endothelial cells (EC). It is a receptor for transforming growth factor (TGF) -beta1 and -beta3 and modulates TGF-beta signaling by interacting with TGF-beta receptors I and/or II. Immunohistochemistry studies have revealed that CD105 is strongly expressed in blood vessels of tumor tissues. Intratumoral microvessel density (MVD) determined using antibodies to CD105 has been found to be an independent prognostic indicator, wherein increased MVD correlates with shorter survival. CD105 is able to be shed into the circulation, with elevated levels detected in patients with various types of cancer and positively correlated with tumor metastasis. Tangible evidence of its proangiogenic role comes from knockout studies in which CD105 null mice die in utero as a result of impaired angiogenesis in the yolk sac and heart defects. The potential usefulness of CD105 for tumor imaging has been evaluated in tumor-bearing mice and dogs that have shown the rapid accumulation of radiolabeled anti-CD105 monoclonal antibody in the tumors with a high tumor-to-background ratio. The anti-CD105 antibody conjugated with immunotoxins and immunoradioisotopes efficiently suppressed/abrogated tumor growth in murine models bearing breast and colon carcinoma without any significant systemic side effects. Immunoscintigraphy in patients with renal cell carcinomas has shown specific localization of 99Tcm-labeled CD105 mab in tumor endothelial cells. Thus, CD105 is a promising vascular target that can be used for tumor imaging, prognosis, and bears therapeutic potential in patients with solid tumors and other angiogenic diseases.

The vasculopathy of Raynaud's phenomenon and scleroderma

The scleroderma (SSc) disease process involves dramatic dysfunction in acute and chronic vascular regulatory mechanisms; it presents initially with heightened vasoconstrictor or vasospastic activity and progresses to structural derangement or vasculopathy of the microcirculation. This article discusses the regulatory mechanisms that contribute to this dysfunction and the vascular changes in the context of the other aspects of the SSc disease process in a novel attempt to integrate the individual pathologies of the disease process.

Angiogenesis and chemokines in rheumatoid arthritis and other systemic inflammatory rheumatic diseases

Angiogenesis, the formation of new vessels, is important in the pathogenesis of rheumatoid arthritis (RA) and other inflammatory diseases. Chemotactic cytokines termed chemokines mediate the ingress of leukocytes, including neutrophils and monocytes into the inflamed synovium. In this review, authors discuss the role of the most important angiogenic factors and angiogenesis inhibitors, as well as relevant chemokines and chemokine receptors involved in chronic inflammatory rheumatic diseases. RA was chosen as a prototype to discuss these issues, as the majority of studies on the role of angiogenesis and chemokines in inflammatory diseases were carried out in arthritis. However, other systemic inflammatory (autoimmune) diseases including systemic lupus erythematosus (SLE), systemic sclerosis (SSc), Sjögren's syndrome (SS), mixed connective tissue disease (MCTD), polymyositis/dermatomyositis (PM/DM) and systemic vasculites are also discussed in this context. As a number of chemokines may also play a role in neovascularization, this issue is also described here. Apart from discussing the pathogenic role of angiogenesis and chemokines, authors also review the regulation of angiogenesis and chemokine production by other inflammatory mediators, as well as the important relevance of neovascularization and chemokines for antirheumatic intervention.

Fisp12/mouse connective tissue growth factor mediates endothelial cell adhesion and migration through integrin alphavbeta3, promotes endothelial cell survival, and induces angiogenesis in vivo

Fisp12 was first identified as a secreted protein encoded by a growth factor-inducible immediate-early gene in mouse fibroblasts, whereas its human ortholog, CTGF (connective tissue growth factor), was identified as a mitogenic activity in conditioned media of human umbilical vein endothelial cells. Fisp12/CTGF is a member of a family of secreted proteins that includes CYR61, Nov, Elm-1, Cop-1/WISP-2, and WISP-3. Fisp12/CTGF has been shown to promote cell adhesion and mitogenesis in both fibroblasts and endothelial cells and to stimulate cell migration in fibroblasts. These findings, together with the localization of Fisp12/CTGF in angiogenic tissues, as well as in atherosclerotic plaques, suggest a possible role for Fisp12/CTGF in the regulation of vessel growth during development, wound healing, and vascular disease. In this study, we show that purified Fisp12 (mCTGF) protein promotes the adhesion of microvascular endothelial cells through the integrin receptor alphavbeta3. Furthermore, Fisp12 stimulates the migration of microvascular endothelial cells in culture, also through an integrin-alphavbeta3-dependent mechanism. In addition, the presence of Fisp12 promotes endothelial cell survival when cells are plated on laminin and deprived of growth factors, a condition that otherwise induces apoptosis. In vivo, Fisp12 induces neovascularization in rat corneal micropocket implants. These results demonstrate that Fisp12 is a novel angiogenic inducer and suggest a direct role for Fisp12 in the adhesion, migration, and survival of endothelial cells during blood vessel growth. Taken together with the recent finding that the related protein CYR61 also induces angiogenesis, we suggest that Fisp12/mCTGF and CYR61 comprise prototypes of a new family of angiogenic regulators that function, at least in part, through integrin-alphavbeta3-dependent pathways.