Lowered angiogeneic capability of peripheral blood lymphocytes in progressive systemic sclerosis (scleroderma)

Systemic Sclerosis Sera Impair Angiogenic Performance of Dermal Microvascular Endothelial Cells: Therapeutic Implications of Cyclophosphamide

In systemic sclerosis (SSc), dermal capillaries are progressively lost with consequent chronic tissue hypoxia insufficiently compensated by angiogenesis. Clinical studies reported that intravenous cyclophosphamide (CYC) may improve SSc-related peripheral microvascular damage. Recently, we showed that CYC treatment may normalize SSc sera-induced abnormalities in endothelial cell-matrix interactions. Our objective was to evaluate in vitro the effects of sera from treatment-naïve or CYC-treated SSc patients on dermal blood microvascular endothelial cell (dMVEC) angiogenesis, migration, proliferation and apoptosis. dMVECs were challenged with sera from 21 SSc patients, treatment-naïve (n = 8) or under CYC treatment (n = 13), and 8 healthy controls. Capillary morphogenesis on Geltrex matrix was significantly reduced upon challenge with sera from naïve SSc patients compared with healthy controls. When dMVECs were challenged with sera from CYC-treated SSc patients, their angiogenic capacity was comparable to that of cells treated with healthy sera. Wound healing capacity and chemotaxis in Boyden chamber were both significantly decreased in the presence either of naïve or CYC-treated SSc sera compared with healthy sera. WST-1 assay revealed that cell proliferation was significantly decreased in dMVECs challenged with sera from naïve SSc patients compared with healthy sera. Conversely, dMVEC proliferation was not impaired in the presence of sera from CYC-treated SSc patients. Accordingly, the percentage of TUNEL-positive apoptotic dMVECs was significantly higher in the presence of sera from naïve SSc patients than healthy controls, while CYC-treated SSc sera did not induce dMVEC apoptosis. Levels of the angiostatic mediators endostatin, pentraxin 3, angiostatin and matrix metalloproteinase-12 were all significantly elevated in sera from naïve SSc patients compared with sera from both healthy controls and CYC-treated SSc patients. In SSc, CYC treatment might boost angiogenesis and consequently improve peripheral microangiopathy through the normalization of the endothelial cell-matrix interactions, reduction of endothelial cell apoptosis and rebalance of dysregulated angiostatic factors.

The pathogenesis of systemic sclerosis

Systemic sclerosis (SSc), also known as scleroderma, is a rare connective tissue disease characterized by vascular and immune dysfunction, leading to fibrosis that can damage multiple organs. Its pathogenesis is complex and poorly understood. Two major clinical subtypes are the limited and diffuse forms. Research into SSc has been hampered by its rarity, its clinical heterogeneity, and the lack of mouse models that accurately recapitulate the disease. Clinical and basic studies have yielded some mechanistic clues regarding pathogenesis. Recent insights gained through the use of microarrays have revealed distinctive subsets of SSc within and beyond the limited and diffuse subsets. In this review, we discuss potential mechanisms underlying the vascular, autoimmune, and fibrotic points of dysregulation. Proper categorization of SSc patients for research studies by use of microarrays or other biomarkers is critical, as disease heterogeneity may explain some of the inconsistencies of prior studies.

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.

Correlation of endostatin and tissue inhibitor of metalloproteinases 2 (TIMP2) serum levels with cardiovascular involvement in systemic sclerosis patients

Fibrosis of oesophagus, lungs, heart, and kidney in the course of systemic sclerosis (SSc) may lead to dysfunction of the above organs or even patients death. Recent studies point out the role of angiogenesis and fibrosis disturbances in the pathogenesis of SSc. Heart fibrosis is one of the most important prognostic factors in SSc patients. So, the aim of our study was to examine cardiovascular dysfunction in SSc patients and its correlation with serum levels of vascular endothelial growth factor (VEGF), endostatin, and tissue inhibitor of metalloproteinase 2 (TIMP2). The study group comprised 34 patients (19 with limited scleroderma (lSSc) and 15 with diffuse scleroderma (dSSc)). The control group consisted of 20 healthy persons, age and sex matched. Internal organ involvement was assessed on the basis of specialist procedures. Serum VEGF, endostatin, and TIMP2 levels were evaluated by ELISA. We found cardiovascular changes in 15 patients with SSc (8 with lSSc and 7 with dSSc). The observed symptoms were of different characters and also coexisted with each other. Higher endostatin serum levels in all systemic sclerosis patients in comparison to the control group were demonstrated (P < .05). Also higher serum levels of endostatin and TIMP2 were observed in patients with cardiovascular changes in comparison to the patients without such changes (P < .05). The obtained results support the notion that angiogenesis and fibrosis disturbances may play an important role in SSc. Evaluation of endostatin and TIMP2 serum levels seems to be one of the noninvasive, helpful examinations of heart involvement in the course of systemic sclerosis.

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.

Interleukin-12 inhibits angiogenesis induced by human tumor cell lines in vivo

Tumor cell-induced angiogenesis, i.e., new blood vessel formation within tumor tissue, is an essential requirement for the growth of solid neoplasms. Interleukin-12 (IL-12) inhibits growth of a variety of experimental tumors in vivo. We tested whether antitumor activity of IL-12 is related to the inhibition of angiogenesis induced by tumor cell lines. Angiogenesis was induced in x-ray immunosuppressed Balb/c mice by intradermal injection of the following human tumor cells: T47D, originating from mammary carcinoma; A431, derived from vulval carcinoma; and Skv, established from bowenoid papulosis, Systemic treatment of the mice with murine IL-12 significantly decreased angiogenesis induced by human tumor cells in a time-and dose-dependent manner. Preincubation of human cells in vitro with IL-12 did not inhibit tumor cell-induced angiogenesis, suggesting that the antiangiogenic capacity of IL-12 is restricted to in vivo conditions. Treatment of the mice with rat antibody against murine interferon-gamma (IFN-gamma) resulted in counteracting the antiangiogenic effect of murine IL-12. Furthermore, human IFN-gamma inhibited the angiogenic activity of human tumor cell lines. This indicates that IFN-gamma is a mediator of the antiangiogenic effect of IL-12. The results show that the mechanism of antitumor action of IL-12 may depend not only on the immunostimulatory activity of this cytokine but also on its effect on tumor cell-induced angiogenesis. IL-12 should be considered as a potential candidate for the treatment of angiogenesis-dependent malignancies.

Decreased monocyte-mediated angiogenesis in scleroderma

Scleroderma is a disease characterized by proliferative vascular lesions in which monocytes/macrophages may play a key role. Monocytes were isolated from 14 scleroderma patients and 11 normal controls and cultured with or without lipopolysaccharide (LPS) (5 micrograms/ml). Monocyte-conditioned medium was assayed in the rat corneal bioassay for angiogenesis. Conditioned medium from normal monocytes was nonangiogenic, as was conditioned medium from scleroderma monocytes. While conditioned medium from LPS-activated normal monocytes was potently angiogenic in 11/13 corneas, conditioned medium from LPS-activated scleroderma monocytes was angiogenic in only 3/14 corneas. Levels of the angiogenic cytokine tumor necrosis factor-alpha (TNF-alpha) were measured in conditioned medium from scleroderma and normal monocytes. TNF-alpha levels were not significantly different in patient and control groups and thus do not account for the decreased angiogenic activity exhibited by scleroderma monocytes. As monocytes require activation to produce angiogenic activity, we determined the cell surface binding of monoclonal antibodies to activation-related (HLA-DR, 3D8, and 8D7) and other (Leu-M5) markers on monocytes by radioimmunoassay. Monocytes were cultured alone, with LPS (5 micrograms/ml), or with interferon-gamma (IFN) (200 units/ml). The usual increase in binding of anti-HLA-DR on stimulation of scleroderma monocytes with IFN was slightly less than that of controls. IFN-stimulated monocytes bound less anti-8D7 than controls. Anti-3D8 and anti-Leu-M5 binding was comparable in both groups. These results suggest that scleroderma monocytes do not produce normal levels of angiogenic activity with LPS stimulation, have some altered markers of activation on their cell surfaces, and may thus contribute to the aberrant vascular proliferation found in this disease.

Assays for angiogenesis: a review

Accurate, reliable quantitation of the neovascular (angiogenic) response, both in vitro and in vivo, is an essential requirement for the study of new blood vessel growth. Over many years, ingenious ways have been developed for measuring this process, and they have contributed much to our present understanding of the vasculogenesis and angiogenesis that accompany normal embryonic development, lactation and wound healing, as well as tumor growth and a variety of other disease states ranging from diabetic retinopathy to autoimmune vasculitis. In this review we describe and evaluate the methodology and specific features of some of the most frequently used of these assays.

Modulatory effect of sera from scleroderma patients on lymphocyte-induced angiogenesis. II. Effector cells for the enhancing effect of acroscleroderma patients' sera

In our previous study, using the modified lymphocyte-induced angiogenesis assay, we found that incubation of normal human peripheral blood mononuclear cells (PBMCs) with sera from patients with acroscleroderma, but not with diffuse scleroderma, markedly enhanced their angiogenic capability. The results of the present work suggest that this enhancement is mediated by lymphocytes bearing receptors for the Fc portion of IgG and belonging mainly to the CD4+ T-cell subset.

Theophylline-resistant and theophylline-sensitive "active" and "total" E rosette-forming lymphocytes in patients with systemic scleroderma

Using the E rosette test and its modification with theophylline, we have studied T regulatory lymphocytes in various forms of systemic scleroderma. Mean percentages of active rosette-forming cells (ARFC) as well as the fraction resistant to theophylline incubation (ARFC-res) were significantly decreased, irrespective of the variety of the disease, compared to the age-matched controls. Late ("cold") rosette-forming fractions were unimpaired. The theophylline-sensitive fraction of total rosette-forming cells (TRFC-sens), which contains mainly cells from the suppressor circuit, was found to be lowered in all patients groups studied, whereas the ARFC-sens fraction was significantly decreased only in patients with diffuse scleroderma over 50 years of age, in whom there was a tendency to a more severe course, as manifested by pronounced systemic organ involvement. The lowered values of E rosette tests were found in a majority of SSc patients and were correlated with the appearance in the sera of factors capable of inhibiting ARFC formation by normal human peripheral blood T lymphocytes. Normal values of the E rosette test were related to the presence in the patients' sera of factors stimulating ARFC formation by normal lymphocytes. We surmise from the results that in SSc patients the T-cell defect is not only restricted to T suppressor cells but also refers to the active theophylline-resistant fraction containing mainly T inducer and T cytotoxic cells.

Partial defects of cell-mediated immunity in patients with epidermodysplasia verruciformis

Different parameters of cell-mediated immunity, including natural cytotoxic reactions, were studied in nine patients with epidermodysplasia verruciformis with or without cutaneous malignancy. We found decreased total number of T lymphocytes and T-helper cells in peripheral blood of the patients, and normal T-suppressor cell number, as detected by monoclonal antibody typing and functional E-rosette test with the use of theophylline. This decrease was found both in active and in late rosette-forming cell subpopulations. Natural killer cell activity of peripheral blood mononuclear cells was found to be increased in four of nine patients with epidermodysplasia verruciformis, whereas antibody-dependent cellular cytotoxicity was within the normal range in all patients studied. Lymphocyte-induced angiogenesis assay, which is a sensitive test for the estimation of the immunocompetence of lymphoid cells, revealed increased angiogenic capability of peripheral blood mononuclear cells in the majority of the patients. Our results suggest that cellular defects in patients with epidermodysplasia verruciformis did not relate to all functions of the immune system.

Enhanced angiogenic capability of monocyte-enriched mononuclear cell suspensions from patients with systemic scleroderma

Different subsets of peripheral blood mononuclear cells (MNC) from 15 patients with systemic scleroderma were tested for their ability to evoke angiogenesis in a xenogenic system. The angiogenic capability of total MNC from patients with systemic scleroderma was lower than that of normal human cells, irrespective of the form of the disease. However, the capability of a monocyte-enriched subset of MNC from patients with scleroderma was found to be increased, as compared with their total MNC and with that of the corresponding subset from healthy individuals. This might be due to the activation of monocytes in the disease.

Modulatory effect of sera from scleroderma patients on lymphocyte-induced angiogenesis

Sera from 22 patients with progressive systemic sclerosis were tested for the ability to modify the angiogenic capability of normal human mononuclear cells. The sera from patients with acrosclerosis, including the abortive form (CREST syndrome: calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasias), markedly enhanced this capability compared with sera from both healthy donors and patients with severe acrosclerosis and diffuse scleroderma. The enhancing effect of sera from patients with acrosclerosis decreased and/or disappeared in cases where the patient's acrosclerosis was chronic and severe. Thus, this test may be of diagnostic value in distinguishing various subgroups of systemic sclerosis.