Selective loss of extracellular matrix proteins is linked to biophysical properties of varicose veins assessed by ultrasonography

Morphological study of incompetent saphenous veins: apoptosis and ultrastructural changes of smooth muscle cells

BACKGROUND

Varicose veins affect approximately 25% of people in industrialized countries.

METHODS

The study aimed at detecting apoptotic cells and histopathological changes in varicose vein walls. Patients (N.=41) with varicose veins and 30 control group patients were divided into two groups according to their age (younger and older than 50 years). Apoptosis was determined by the TUNEL assay, elastin and collagen IV expression by immunohistochemistry and ultrastructural changes by transmission electron microscopy.

RESULTS

The results show that the number of apoptotic cells in the layers of varicose veins increased, in particular in a group of patients aged over 50 years. In the varicose veins as compared to control veins the elastic fibers were found to be thinner, more fragmented and disorderly arranged. Elastin and collagen IV expression was found to decline in the intima and the media of varicose veins in both age groups. Electron microscopy demonstrated hypertrophy and degeneration of smooth muscle cells. Furthermore, cells with ultrastructural feature of apoptosis were noted. In the disorganized and expanded extracellular matrix membrane-bound vesicles, ghost bodies with different size and electron density were observed. Ghost bodies seem to bud off from smooth muscle cells and are likely to be involved in extracellular matrix remodeling as they are seen in close contact with collagen fibers.

CONCLUSIONS

The study demonstrates increase of apoptotic cells in the wall of varicose veins along with vein wall structural abnormalities including alterations of smooth muscle cells and decline of elastin and collagen IV expression.

What is the relationship of varicose vein pathogenesis with collagen fibers?

Aims and Background

In this study, the densities of collagen 1 and collagen 4, which are an effective vascular component in the remodelling of varicose veins, were investigated.

Materials and Methods

The study included primary varicose vein samples of 20 patients and vein samples of 20 healthy controls. Immunohistochemical staining was performed using collagen 1 and collagen 4 antibodies. Histochemical staining was performed using Masson Trichrome.

Results

In the immunohistochemical analysis of varicose samples, collagen 1 immunostaining was negative in 17 cases (85%) and positive in 3 cases (15%). In healthy venous tissue samples, collagen 1 immunostaining was negative in 12 cases (60%) and positive in 8 cases (40%). There was no statistically significant difference between both groups concerning collagen 1 immunostaining (p > 0.05). In varicose samples, collagen 4 immunostaining was negative in 4 cases (20%) and positive in 16 cases (80%). In healthy venous tissue samples, collagen 4 immunostaining was negative in 13 cases (65%) and positive in 7 cases (35%). Statistical comparison of healthy veins and varicose veins concerning collagen 4 immunostaining showed a significant difference (p = 0.03). In the histochemical analysis of varicose samples, Masson Trichrome staining was negative in 4 cases (20%) and positive in 16 cases (80%). In healthy venous tissue samples, Masson Trichrome staining was negative in 18 cases (90%) and positive in 2 cases (10%). Statistical comparison of healthy veins and varicose veins concerning collagen 4 immunostaining showed a significant difference (p = 0.01).

Conclusion

The change in the density of collagen types plays an important role in vein wall remodeling.

Contribution of the Elastic Component and Venous Wall Arterialization in Patients with Venous Reflux

Chronic venous disease (CVeD) is defined as a set of disorders affecting the venous system mainly manifested in the form of varicose veins. CVeD is characterized by a sustained venous hypertension, leading to a plethora of functional and structural changes in the vein that may cause valve incompetence and pathologic reflux. In turn, venous reflux aggravates the venous hypertension and enhances the progression of CVeD into the most advanced stages. Previous studies have proposed that there are several alterations in the venous wall preceding the valve dysfunction and venous reflux. Besides, it has also been identified that young patients with CVeD present premature aging and changes in the venous wall composition that may be related to the presence of venous reflux. In this context, the aim of the present study is to examine the possible pathophysiological role of elastic fibers and their precursors in the venous wall of patients with reflux in comparison to those without reflux, considering the variable age in both groups (<50 years and ≥50 years). We performed immunohistochemical and quantitative polymerase chain reaction (PCR) in order to assess the protein and gene expression of tropoelastin, fibrillin-1, fibulins 4 and 5, lysyl oxidase and lysyl oxidase like 1, respectively. In parallel, we assessed the elastin content through histological techniques (orcein stain) in this group of patients. Our results show significant changes in elastic fibers and their precursors in young patients with pathologic reflux when compared with elder patients with reflux and young patients without reflux. These variations suggest that the venous system of young patients with venous reflux appears to present an enhanced dynamism and arterialization of the venous wall, which may be associated with a premature aging and pathological environment of the tissue.

Tissue remodelling and increased DNA damage in patients with incompetent valves in chronic venous insufficiency

Chronic venous insufficiency (CVI), in which blood return to the heart is impaired, is a prevalent condition worldwide. Valve incompetence is a complication of CVI that results in blood reflux, thereby aggravating venous hypertension. While CVI has a complex course and is known to produce alterations in the vein wall, the underlying pathological mechanisms remain unclear. This study examined the presence of DNA damage, pro‐inflammatory cytokines and extracellular matrix remodelling in CVI‐related valve incompetence. One hundred and ten patients with CVI were reviewed and divided into four groups according to age (<50 and ≥50 years) and a clinical diagnosis of venous reflux indicating venous system valve incompetence (R) (n = 81) or no reflux (NR) (n = 29). In vein specimens (greater saphenous vein) from each group, PARP, IL‐17, COL‐I, COL‐III, MMP‐2 and TIMP‐2 expression levels were determined by RT‐qPCR and immunohistochemistry. The younger patients with valve incompetence showed significantly higher PARP, IL‐17, COL‐I, COL‐III, MMP‐2 and reduced TIMP‐2 expression levels and a higher COL‐I/III ratio. Young CVI patients with venous reflux suffer chronic DNA damage, with consequences at both the local tissue and systemic levels, possibly associated with ageing.

Noninvasive measurement of venous wall deformation induced by changes in transmural pressure shows altered viscoelasticity in patients with chronic venous disease

OBJECTIVE

The noninvasive measurement of venous wall deformation induced by changes in transmural pressure could allow for the assessment of viscoelasticity and differentiating normal from diseased veins.

METHODS

In 57 patients with limbs in the C1s (telangiectasia or reticular veins and symptoms), C3 (edema), or C5 (healed venous ulcer) CEAP (clinical, etiologic, anatomic, pathophysiologic) category of chronic venous disease and 54 matched healthy controls, we measured the changes in the cross-sectional area of the small saphenous vein and a deep calf vein in the supine and standing positions and under compression with an ultrasound probe using ultrasonography.

RESULTS

The small saphenous vein, but not the deep calf vein, cross-sectional area was smaller in the limbs of the controls than in the limbs with C3 or C5 disease but was not different from that in C1s limbs. When changing from the supine to the standing position, a greater force was required to collapse the leg veins. Their cross-sectional area increased in most subjects but decreased in 31.5% of them as for the small saphenous veins and 40.5% for the deep calf vein. The small saphenous vein area vs compression force function followed a hysteresis loop, demonstrating viscoelastic features. Its area, which represents the viscosity component, was greater (P < .001) in the pooled C3 and C5 limbs (median, 2.40 N⋅mm²; lower quartile [Q1] to upper quartile [Q3], 1.65-3.88 N⋅mm²) than in the controls (median, 1.24 N⋅mm²; Q1-Q3, 0.64-2.14 N⋅mm²) and C1s limbs (median, 1.15 N⋅mm²; Q1-Q3, 0.71-2.97 N⋅mm²). The area increased (P < .0001) in the standing position in all groups.

CONCLUSIONS

Postural changes in the cross-sectional area of the leg veins were highly diverse among patients with chronic venous disease and among healthy subjects and appear unsuitable for pathophysiologic characterization. In contrast, small saphenous vein viscoelasticity increased consistently in the standing position and the viscosity was greater in limbs with C3 and C5 CEAP disease than in controls.

Role of fibronectin in chronic venous diseases: A review

Fibronectin (FN) circulating in the blood and produced by cells provides the basis of the extracellular matrix (ECM) formed in healing acute wounds. The time-dependent deposition of FN by macrophages, its synthesis by fibroblasts and myofibroblasts, and later degradation in the remodeled granulation tissue are a prerequisite for successful healing of wounds. However, the pattern of FN expression and deposition in skin lesions is disturbed. The degradation of the ECM components including FN in varicose veins prevails over ECM synthesis and deposition. FN is inconspicuous in the fibrotic lesions in lipodermatosclerosis, while tenascin-C containing FN-like peptide sequences are prominent. FN is produced in large amounts by fibroblasts at the edge of venous ulcers but FN deposition at the wound bed is impaired. Both the proteolytic environment in the wounds and the changed function of the ulcer fibroblasts may be responsible for the poor healing of venous ulcers. The aim of this review is to describe the current knowledge of FN pathophysiology in chronic venous diseases. In view of the fact that FN plays a crucial role in organizing the ECM, further research focused on FN metabolism in venous diseases may bring results applicable to the treatment of the diseases.

Altered elastase-alpha1-antitrypsin balance in the blood of patients with chronic venous disease

OBJECTIVES

Although leukocyte elastase is suspected to be involved in the damage of vein wall during chronic venous disease, the equilibrium between this protease and its inhibitor, alpha1-antitrypsin, has not yet been evaluated. The aim of the present study was to determine the relationship between leukocyte elastase and alpha1-antitrypsin, in the blood of patients with chronic venous disease.

PATIENTS AND METHODS

The concentration and the activity of leukocyte elastase along with the activity of alpha1-antitrypsin were evaluated in the blood of 55 chronic venous disease patients. The results were compared with those obtained in 33 healthy age and sex-matched volunteers.

RESULTS

A significant decrease in the leukocyte elastase activity that correlated with an increased alpha1-antitrypsin activity was observed in the serum of patients with mild clinical symptoms of chronic venous disease.

CONCLUSIONS

The results of the study did not confirm a hypothesis about an important role of proteolytic activity of leukocyte elastase in the vein wall injury mechanism. They show that the leukocyte elastase-alpha1-antitrypsin balance is rather shifted toward antiprotease activity, especially in an early stage of chronic venous disease.

Cellular and molecular basis of Venous insufficiency

Chronic venous disease (CVD) has a range of clinical presentations, including tortuous, distended veins in lower extremities, increasing skin pigmentation, and in severe cases ulceration of the affected skin. Venous insufficiency, a precursor to CVD characterized by improper return of blood from the lower extremities to the heart, must be studied in its earliest stages at a time when preventative measures could be applied in man. This underscores the need for basic research into biomarkers and genetic predisposing factors affecting the progression of venous disease. Investigation over the past decade has yielded insight into these specific genetic, cellular and molecular mechanisms underlying the development of venous disease. Among the many advances include the elucidation of an increasing role for matrix metalloproteinases as important mediators of the degenerative process involved with venous insufficiency. This may be preceded by an inflammatory process which further contributes to venular degeneration and endothelial dysfunction seen in advanced presentation of disease. Furthermore, genomic analyses have shed light upon temporal expression patterns of matrix remodeling proteins in diseased tissue samples. In this review we examine some of the current findings surrounding cellular, molecular and genetic advances in delineating the etiology of chronic venous disease.

Vascular wall extracellular matrix proteins and vascular diseases

Extracellular matrix proteins form the basic structure of blood vessels. Along with providing basic structural support to blood vessels, matrix proteins interact with different sets of vascular cells via cell surface integrin or non-integrin receptors. Such interactions induce vascular cell de novo synthesis of new matrix proteins during blood vessel development or remodeling. Under pathological conditions, vascular matrix proteins undergo proteolytic processing, yielding bioactive fragments to influence vascular wall matrix remodeling. Vascular cells also produce alternatively spliced variants that induce vascular cell production of different matrix proteins to interrupt matrix homeostasis, leading to increased blood vessel stiffness; vascular cell migration, proliferation, or death; or vascular wall leakage and rupture. Destruction of vascular matrix proteins leads to vascular cell or blood-borne leukocyte accumulation, proliferation, and neointima formation within the vascular wall; blood vessels prone to uncontrolled enlargement during blood flow diastole; tortuous vein development; and neovascularization from existing pathological tissue microvessels. Here we summarize discoveries related to blood vessel matrix proteins within the past decade from basic and clinical studies in humans and animals - from expression to cross-linking, assembly, and degradation under physiological and vascular pathological conditions, including atherosclerosis, aortic aneurysms, varicose veins, and hypertension.

Varicose veins: role of mechanotransduction of venous hypertension

Varicose veins affect approximately one-third of the adult population and result in significant psychological, physical, and financial burden. Nevertheless, the molecular pathogenesis of varicose vein formation remains unidentified. Venous hypertension exerted on veins of the lower extremity is considered the principal factor in varicose vein formation. The role of mechanotransduction of the high venous pressure in the pathogenesis of varicose vein formation has not been adequately investigated despite a good progress in understanding the mechanomolecular mechanisms involved in transduction of high blood pressure in the arterial wall. Understanding the nature of the mechanical forces, the mechanosensors and mechanotransducers in the vein wall, and the downstream signaling pathways will provide new molecular targets for the prevention and treatment of varicose veins. This paper summarized the current understanding of mechano-molecular pathways involved in transduction of hemodynamic forces induced by blood pressure and tries to relate this information to setting of venous hypertension in varicose veins.

Pathogenesis of primary varicose veins

BACKGROUND

Valvular incompetence and reflux are common features of primary varicose veins, and have long been thought to be their cause. Recent evidence, however, suggests that changes in the vein wall may precede valvular dysfunction.

METHODS

A literature search was performed using PubMed and Ovid using the keywords 'varicose vein wall changes', 'pathogenesis', 'aetiology' and 'valvular dysfunction'. Articles discussing the pathophysiology of complications of varicose veins, such as ulceration, recurrence, thrombophlebitis and lipodermatosclerosis, were excluded.

RESULTS AND CONCLUSION

Positive family history, age, sex and pregnancy are important risk factors for varicose vein formation. Areas of intimal hyperplasia and smooth muscle cell proliferation are often noted in varicose veins, although regions of atrophy are also present. The total elastin content in varicose as opposed to non-varicose veins is reduced; changes in overall collagen content are uncertain. Matrix metalloproteinases (MMPs), including MMP-1, MMP-2, MMP-3, MMP-7 and MMP-9, and tissue inhibitor of metalloproteinase (TIMP) 1 and TIMP-3 are upregulated in varicose veins. Activation of the endothelium stimulates the recruitment of leucocytes and the release of growth factors, leading to smooth muscle cell proliferation and migration. Dysregulated apoptosis has also been demonstrated in varicose veins. An understanding of the pathophysiology of varicose veins is important in the identification of potential therapeutic targets and treatment strategies.