Defective vasculogenesis in systemic sclerosis

doi:10.1016/S0140-6736(04)16853-0

The Lancet

Volume 364, Issue 9434, 14–20 August 2004, Pages 603-610

https://doi.org/10.1016/S0140-6736(04)16853-0 Get rights and content

Summary

Background

Typical vascular features of systemic sclerosis include low capillary density and vascular obliteration. The formation and repair of blood vessels in adults involve vasculogenesis, which is mediated through the recruitment of bone-marrow-derived circulating endothelial precursors (CEP). We investigated whether vasculogenesis is impaired in patients with systemic sclerosis.

Methods

Peripheral blood was obtained from 11 patients with systemic sclerosis, 11 with rheumatoid arthritis, and 11 healthy controls. Factors potentially affecting the CEP number were matched among the three groups. CEP (identified as circulating cells positive for CD34, CD133, and the type 2 receptor for vascular endothelial growth factor) were quantified by cell sorting and three-colour flow cytometry. The circulating concentrations of angiogenic factors were measured by ELISA. The potential of CEP to differentiate into endothelial cells was assessed by the upregulation of von Willebrand factor after in-vitro maturation treatment.

Findings

The absolute number of CEP was much lower in patients with systemic sclerosis than in patients with rheumatoid arthritis or healthy controls (median 274 [IQR 178–395] vs 1154[653–1524] and 1074 [713–1186] per 20 mL peripheral blood, respectively; p<0·0001 by Kruskal-Wallis test. Paradoxically, circulating concentrations of most angiogenic factors were significantly higher in patients with systemic sclerosis than in healthy controls. The proportion of CEP that differentiated into endothelial cells was significantly lower in patients with systemic sclerosis than in healthy controls (p<0·0001, Mann-Whitney test).

Interpretation

Insufficient vascular repair machinery due to defective vasculogenesis might contribute to vasculopathy in systemic sclerosis.

Relevance to practice

As well as providing an important insight into the pathogenesis of this disorder, these findings suggest that dysregulated vasculogenesis might be important in other disorders with abnormalities in vascular formation, including those with excessive formation of new vessels such as cancer and those with deficient vessel formation such as atherosclerosis. Circulating endothelial precursors could be a novel target for therapeutic strategies for ischaemic complications in patients with systemic sclerosis.

Introduction

Systemic sclerosis (or scleroderma) is a multiorgan disease characterised by excessive fibrosis and microvascular abnormalities.¹ The vasculopathy in the disorder mainly affects small arteries and capillaries and causes reduced blood flow and tissue ischaemia, which lead to clinical manifestations, such as Raynaud's syndrome, fingertip ulcers, and gangrene.¹ Morphological changes in the vessels of patients with this disease include lower than normal capillary density and obliteration of vessels due to intimal proliferation and fibrosis.¹ The vascular involvement in patients with systemic sclerosis is thought to be primarily induced by increased vascular injury occurring as a result of inflammatory immune processes, ischaemia-reperfusion reactions, and an imbalance between coagulation and fibrinolysis,¹ but the detailed sequence of the pathogenetic events remains unclear.

Recent studies have provided increasing evidence that the formation of new blood vessels in postnatal life does not result solely from the sprouting of pre-existing vessels (angiogenesis) but also involves the recruitment of bone-marrow-derived progenitors for endothelial cells (vasculogenesis).2, 3 These circulating endothelial precursors (CEP) have properties similar to those of embryonic angioblasts.⁴ CEP can be identified by a characteristic surface phenotype that is positive for CD34, CD133, and VEGFR-2.⁵ Postnatal vasculogenesis mainly contributes to vascular healing in response to vascular injury or ischaemia through the processes of rapid endothelialisation of denuded vessels and collateral vessel formation.2, 3, 6 In this process, CEP home to the site of injury and work in concert with existing mature endothelial cells.2, 7

In patients with systemic sclerosis, despite the reduced blood flow and tissue ischaemia, the formation of blood vessels seems to be insufficient to replace the damaged vessels.¹ The following findings support this idea: avascularity is the most prominent feature of nailfold capillaries in active disease;⁸α_Vβ₃-positive newly formed blood vessels are almost completely absent from skin;⁹ and angiography of many patients with late-stage systemic sclerosis indicates a lack of digital vessels. Therefore, we hypothesised that vasculopathy related to systemic sclerosis might be caused by defective vasculogenesis. To test this hypothesis, we have developed assay systems to assess the absolute numbers of CEP and their maturation potential, and we have used these tests to examine the quantity and function of CEP in patients with systemic sclerosis.

Section snippets

Patients

We studied 11 female patients with systemic sclerosis, all of whom met the American College of Rheumatology preliminary criteria.¹⁰ Patients with symptoms that overlapped those of other connective-tissue diseases were excluded. Controls matched for age and sex were 11 female patients with rheumatoid arthritis, as a systemic inflammatory disease control, and 11 healthy women. All patients with rheumatoid arthritis met the American College of Rheumatology classification criteria¹¹ and had

Results

The clinical characteristics of the participants are summarised in table 1. There was no difference in age at examination among the three groups. The disease duration was similar in patients with systemic sclerosis and those with rheumatoid arthritis, and both groups included patients with early and late disease. All the participants were female, and factors potentially affecting the number of CEP, including age, menstruation status, smoking, hypertension, and hypercholesterolaemia,¹⁶ were

Discussion

We found that patients with systemic sclerosis had much lower numbers of CEP than healthy controls. Patients with extremely low CEP numbers were likely to have profound vascular involvement, such as pitting scars and fingertip ulcers. An overall deficiency in CD34-positive cells and CD34-positive, CD133-positive cells in systemic sclerosis and rheumatoid arthritis suggests impairment of haemopoiesis in these connective-tissue diseases; however, a deficiency in CEP was detected in systemic

Glossary

Circulating endothelial precursors (CEP): Migratory cells with capacity to circulate, proliferate, and differentiate into mature endothelial cells, but without typical mature endothelial morphology or markers or the ability to form vascular lumen. These cells can be identified by a characteristic surface phenotype positive for CD34, CD133, and VEGFR-2.
CD34: A transmembrane glycoprotein mainly expressed on haemopoietic stem cells and endothelial cells. This molecule serves as a

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Mechanisms of DiseaseDefective vasculogenesis in systemic sclerosis

Summary

Background

Methods

Findings

Interpretation

Relevance to practice

Introduction

Section snippets

Patients

Results

Discussion

Glossary

Rheum Dis Clin North Am

Blood

Blood

Exp Hematol

Am J Med

Lancet

Blood

Blood

Blood

Am Heart J

Bone marrow origin of endothelial progenitor cells responsible for postnatal vasculogenesis in physiological and pathological neovascularization

Circ Res

Blood-borne seeding by hematopoietic and endothelial precursors from the allantois

Proc Natl Acad Sci USA

Vascular trauma induces rapid but transient mobilization of VEGFR2+AC133+ endothelial precursor cells

Circ Res

Increased but imbalanced expression of VEGF and its receptors has no positive effect on angiogenesis in systemic sclerosis skin

Clin Exp Rheumatol

Preliminary criteria for the classification of systemic sclerosis (scleroderma)

Arthritis Rheum

Mechanisms of Disease
Defective vasculogenesis in systemic sclerosis