Mechanisms of varicose vein formation: valve dysfunction and wall dilation

Cell death pattern of a varicose vein organ culture model

The study aimed to investigate the viability of a varicose vein (VV) organ culture model by assessing cell death pattern. To assess pattern of cell death with time, VV organ cultures were incubated for up to 14 days with regular medium changed. To assess viability, cell death of VV organ cultures treated with sodium azide and their untreated counterparts was assayed. Increased cell death was measured in VV organ cultures from day 0 to 2. Cell death decreased gradually after day 2 and plateaued from day 8 to 14.VV organ cultures treated with sodium azide demonstrated significantly more cell death in tissue (P = 0.001). Cell death measured in cultures treated with sodium azide continued to increase until day 7. In conclusion, this study demonstrated the viability of a VV organ culture model with most cell death occurred within the first two days and then declined to a relatively low level.

Sex steroid hormones are not altered in great saphenous veins after varicose vein treatment in male patients

OBJECTIVE

The objective of this study was to assess differences in blood samples (sex steroid hormone levels and blood counts) before and after surgical treatment of incompetent great saphenous veins (GSV) in males.

METHODS

Antecubital vein and GSV blood samples were taken from 11 men with varicose veins and GSV reflux before and after treatment. Six patients were treated with high ligation, stripping and phlebectomy. Five patients were treated with endoluminal radiofrequency ablation and phlebectomy. After a four-year follow-up period (FU) cubital vein and GSV blood samples were taken again.

RESULTS

In men with varicose veins, significantly higher (P < 0.05) serum testosterone (median 25.18 nmol/L, range 8.82-225.1) and oestradiol (median 179 pmol/L, range 79-941) levels were found in the saphenous vein samples before and after the FU (testosterone 18.8 nmol/L, range 7.96-83.1, oestradiol 171 pmol/L range 125-304) compared with the cubital vein samples before therapy (testosterone 15.72 nmol/L, range 8.36-23.29; oestradiol 84 pmol/L, range 41-147) and after the FU (testosterone 14.5 nmol/L, range 6.10-22.2, oestradiol 117 pmol/L, range 95-165). After the FU, one patient demonstrated recurrent varicose veins with groin neovascularization. Another presented with axial reflux of the anterior accessory saphenous vein. Further differences in blood counts and serum androstenedione levels between the upper and lower extremities were not detected.

CONCLUSION

The differences between testosterone and oestradiol levels in the leg veins compared with the cubital veins persist after treating men with refluxing saphenous veins. These results suggest that local hormone regulation may be different between leg and arm veins in men with varicose veins.

Absence of venous valves in mice lacking Connexin37

Venous valves play a crucial role in blood circulation, promoting the one-way movement of blood from superficial and deep veins towards the heart. By preventing retrograde flow, venous valves spare capillaries and venules from being subjected to damaging elevations in pressure, especially during skeletal muscle contraction. Pathologically, valvular incompetence or absence of valves are common features of venous disorders such as chronic venous insufficiency and varicose veins. The underlying causes of these conditions are not well understood, but congenital venous valve aplasia or agenesis may play a role in some cases. Despite progress in the study of cardiac and lymphatic valve morphogenesis, the molecular mechanisms controlling the development and maintenance of venous valves remain poorly understood. Here, we show that in valved veins of the mouse, three gap junction proteins (Connexins, Cxs), Cx37, Cx43, and Cx47, are expressed exclusively in the valves in a highly polarized fashion, with Cx43 on the upstream side of the valve leaflet and Cx37 on the downstream side. Surprisingly, Cx43 expression is strongly induced in the non-valve venous endothelium in superficial veins following wounding of the overlying skin. Moreover, we show that in Cx37-deficient mice, venous valves are entirely absent. Thus, Cx37, a protein involved in cell-cell communication, is one of only a few proteins identified so far as critical for the development or maintenance of venous valves. Because Cxs are necessary for the development of valves in lymphatic vessels as well, our results support the notion of common molecular pathways controlling valve development in veins and lymphatic vessels.

How Does the Pathophysiology Influence the Treatment of Pelvic Congestion Syndrome and is the Result Long-lasting?

The objectives of this study are to consider the influence of pathophysiology in the treatment of pelvic congestion syndrome (PCS) and to determine the criteria which impact on the long-term results. A classification of venous pathology including three types of pathophysiological conditions, independent of the location of the pelvic venous pathology, is developed and illustrated. These types, diagnosed by cross-sectional imaging and confirmed by phlebography, are associated with a specific therapeutic plan. The long-term results are dependent on the quality of the initial Phlebographic mapping that must be selective and complete, the angiographic findings, in particular the study of collaterals feeding the venous anomalies, the treatment of all venous anomalies, the respect of contraindications, the use of appropriate materials and the occurrence of new pregnancies. In conclusion, the feasibility and satisfactory short-term results of endovascular treatment of PCS are admitted. Questions remain regarding the effectiveness of the different embolic agents and the long-term results of this treatment.

What is the Medical Rationale for the Treatment of Varicose Veins?

Varicose veins occur in up to one-third of Western populations and are associated with clinical manifestations ranging from asymptomatic, isolated varicose veins (C2 disease) to venous ulceration. While the development of less invasive treatment options, such as endovenous ablation and sclerotherapy, have been well accepted by patients they have led to increased utilization of scarce healthcare resources. While few would argue with the treatment of acute complications such as superficial venous thrombosis and variceal haemorrhage, the role of interventional treatment in the management of lifestyle limiting symptoms and the prevention of disease progression may be debatable. Good-quality evidence does suggest that surgical management of varicose veins is associated with improved quality of life at costs below the thresholds of many Western healthcare systems. However, the progression of isolated C2 disease to advanced chronic venous insufficiency occurs infrequently and the role of treatment to prevent such progression remains undefined at present.

Oral doxycycline with topical tacrolimus for treatment of stasis dermatitis due to chronic venous insufficiency: A pilot study

Objectives:

Chronic venous insufficiency (CVI) in lower limbs manifest as stasis dermatitis. The anti-collagenase, anti-inflammatory and immunomodulatory effects of doxycycline and the T-cell inhibitory effects of tacrolimus could theoretically modify the disease pathophysiology. This study was undertaken to evaluate the efficacy and safety of four weeks combination therapy of oral doxycycline 100 mg with topical tacrolimus 0.1% for stasis dermatitis associated with CVI.

Materials and Methods:

A single-arm, interventional pilot study was conducted on subjects with CVI of C4 to C6 category (CEAP classification: clinical, etiology, anatomical, pathophysiology). Treatment duration was four weeks with fortnightly follow-ups. Primary efficacy was assessed as changes from baseline of pigmentation, erythema, edema, itching and hair loss of the affected area evaluated on Likert scale scores. Secondary efficacy parameters were percentage improvement of the dermatitis area and changes in ulcer dimensions (maximum length and breadth), if present. Safety evaluation included all treatment emergent clinical signs and symptoms reported by the patients and/or observed by the physician.

Results:

Out of 19 recruited subjects, 15 completed the study for analysis. Significant (P<0.01) improvement in pain, edema, pigmentation, erythema and exudation were observed. Reduction of ulcer dimensions was also statistically significant (P<0.01). 86.6% showed improvement of the dermatitis area, 6.7% patients failed to show any improvement and 6.7% showed worsening. Adverse effects were observed in only two subjects.

Conclusion:

This pilot study suggests efficacy of this combination therapy in controlling features of stasis dermatitis but further studies are needed for validation.

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.

Endothelium-dependent nitric oxide and hyperpolarization-mediated venous relaxation pathways in rat inferior vena cava

INTRODUCTION

The vascular endothelium plays a major role in the control of arterial tone; however, its role in venous tissues is less clear. The purpose of this study was to determine the role of endothelium in the control of venous function and the relaxation pathways involved.

METHODS

Circular segments of inferior vena cava (IVC) from male Sprague-Dawley rats were suspended between two wires and isometric contraction to phenylephrine (Phe; 10(-5)M) and 96 mM KCl was measured. Acetylcholine (Ach; 10(-10) to 10(-5)M) was added and the percentage of venous relaxation was measured. To determine the role of nitric oxide (NO) and prostacyclin (PGI(2)), vein relaxation was measured in the presence of the nitric oxide synthase inhibitor N(ω)-nitro-L-arginine methyl ester (L-NAME; 3 × 10(-4) M) and the cyclooxygenase inhibitor indomethacin (10(-5) M). To measure the role of hyperpolarization, vein relaxation was measured in the presence of K(+) channel activator cromakalim (10(-11) to 10(-6) M), and the nonselective K(+) channel blocker tetraethylammonium (TEA; 10(-3) M). To test for the contribution of a specific K(+) channel, the effects of K(+) channel blockers: glibenclamide (adenosine triphosphate [ATP]-sensitive K(ATP), 10(-5) M), 4-aminopyridine (4-AP; voltage-dependent K(v), 10(-3) M), apamin (small conductance Ca(2+)-dependent SK(Ca), 10(-7) M), and iberiotoxin (large conductance Ca(2+)-dependent BK(Ca), 10(-8) M) on Ach-induced relaxation were tested.

RESULTS

Ach caused concentration-dependent relaxation of Phe contraction (maximum 49.9 ± 4.9%). Removal of endothelium abolished Ach-induced relaxation. IVC treatment with L-NAME partially reduced Ach relaxation (32.8 ± 4.9%). In IVC treated with L-NAME plus indomethacin, significant Ach-induced relaxation (33.6 ± 3.2%) could still be observed, suggesting a role of endothelium-derived hyperpolarizing factor (EDHF). In IVC treated with L-NAME, indomethacin and TEA, Ach relaxation was abolished, supporting a role of EDHF. In veins stimulated with high KCl, Ach caused relaxation (maximum 59.5 ± 3.5%) that was abolished in the presence of L-NAME and indomethacin suggesting that any Ach-induced EDHF is blocked in the presence of high KCl depolarizing solution, which does not favor outward movement of K(+) ion and membrane hyperpolarization. Cromakalim, an activator of K(ATP), caused significant IVC relaxation when applied alone or on top of maximal Ach-induced relaxation, suggesting that the Ach response may not involve K(ATP). Ach-induced relaxation was not inhibited by glibenclamide, 4-AP, or apamin, suggesting little role of K(ATP), K(v) or SK(Ca), respectively. In contrast, iberiotoxin significantly inhibited Ach-induced relaxation, suggesting a role of BK(Ca).

CONCLUSIONS

Thus, endothelium-dependent venous relaxation plays a major role in the control of venous function. In addition to NO, an EDHF pathway involving BK(Ca) may play a role in endothelium-dependent venous relaxation.

Associations of NF-kappaB and bax with apoptosis in varicose veins of women of different age groups

The study aimed at detecting apoptotic endothelial cells (ECs) and smooth muscle cells (SMCs) together with determining expression of NF-kappaB (p105/p50) and Bax in varicose vein walls. Women (n = 35) undergoing the excision of varicose veins were divided into 3 groups: younger than 35 years (I), 36–50 years (II), and older than 50 years (III). Apoptosis was determined by the TUNEL method, NF-kappaB and Bax expression by immunohistochemistry. The percentage of apoptotic ECs and SMCs in the layers of varicose vein wall increased in groups II and III. NF-kappaB expression had the lowest level in Group II with particularly low level in the media. Contrariwise, Bax expression levels in Group II were increased. The study revealed that in varicose veins ECs and SMCs apoptosis increased with advancing age. If increase in apoptosis during earlier stages of varicosities is probably regulated by intrinsic pathway, then in older patients other signaling pathways may be involved.

The ostial valve of the great saphenous vein

Background

Venous valves have been classified into parietal (PVs) and ostial valves (OVs). PVs are located within the lumen of veins, whereas the OVs are located directly at the confluence of two veins. In the common femoral vein (CFV), the most prominent PVs are the suprasaphenic and infrasaphenic valve. The terminal valve (often designated as ‘valvule ostiale’ in the relevant literature in French) defined as that lying between the orifice of the great saphenous vein (GSV) and the most proximal of the major superficial tributary veins and the preterminal valve represent the most important PVs in the GSV. While PVs are well studied, there is not much literature on the OVs of the superficial venous system, especially of the GSV.

Objective

In order to investigate the presence of OVs (defined strictly as valves located at the entrance of a tributary vein) in the GSV, we carried out studies on specimens obtained from bodies bequested to the Division of Clinical and Functional Anatomy of Innsbruck Medical University.

Methods

Ninety-eight specimens consisting of the CFV and the attached tributary veins including the GSV were investigated.

Results

In five of these (5.1%), a single-cusped OV, in six (6.1%) a two-cusped OV and in 10 (10.2%) remnants of an OV were identified. Thus, OVs do not seem to be primarily present in all GSVs.

Conclusion

The distinction between PVs and OVs is not always clear in literature, and as a consequence misinterpretations may occur. Very often the terminal valve of the GSV, which is in fact a PV, is designated as an ‘ostial valve’. In view of its widespread use, we suggest that the term ‘ostial valve’ together with its clear description be included in the consensus documents of the ‘Union Internationale de Phlébologie’.

Progression of reflux patterns in saphenous veins of women with chronic venous valvular insufficiency

Background

Venous ultrasonography identifies reflux patterns of the great and small saphenous veins (GSV, SSV), allowing evaluation of lower extremities for treatment planning and patient follow-up.

Objective

To determine progression of saphenous vein reflux patterns in women with primary venous valvular insufficiency.

Methods

Venous ultrasonography was performed in the extremities of 92 women, 43 ± 12 (23–77) years old, CEAP (clinical, aetiological, anatomical and pathological elements) clinical classes C1–C2. Two examinations were performed 33 ± 19 (8–89) months apart in patients without saphenous vein treatment. GSV and SSV reflux patterns were classified as segmental, multisegmental, distal, proximal, diffuse and normal. Prevalence was determined for each examination, separately for right and left extremities, and jointly. Prevalence was compared using χ2 statistics.

Results

Reflux prevalence was higher for the GSV, 89% (164/184) and 88% ( n = 162), than for the SSV, 24% ( n = 45) and 30% ( n = 56), respectively for first and second examinations ( P < 0.001). Reflux pattern prevalence was not significantly different in the right and left extremities (1.0 > P > 0.14). Most prevalent patterns were (a) GSV segmental reflux initially, 41% (76/184), decreasing to 28% (52/184) ( P = 0.009), and (b) GSV multisegmental reflux at the second examination, increasing from 26% (48/184) to 40% (73/184) ( P = 0.006). Prevalence of other GSV or SSV reflux patterns did not change significantly (0.88 > P > 0.19).

Conclusions

We documented early findings and venous reflux progression in a specific population of women with varicose veins, reticular veins and telangiectasias. GSV segmental reflux was most prevalent initially, progressing to GSV multisegmental reflux.

Ca(2+)-dependent contraction by the saponoside escin in rat vena cava: implications in venotonic treatment of varicose veins

BACKGROUND

Saponosides (horse chestnut seed extract, escin) and flavonoids (diosmin, Daflon 500, Servier, France) exhibit venotonic properties that have been utilized in treatment of varicose veins. However, the cellular mechanisms underlying the venotonic properties of escin and diosmin are unclear. Because Ca(2+) is a major regulator of venous smooth muscle (VSM) function, we tested the hypothesis that escin and diosmin promote Ca(2+)-dependent venous contraction.

METHODS

Rings of inferior vena cava (IVC) from male rats were suspended in a tissue bath for measurement of isometric contraction. Following control contraction to 96 mM KCl, the effects of escin and diosmin (10(-10) to 10(-4) M) on vein contraction were measured. To test the role of intracellular Ca(2+) release, the vein response to escin and diosmin was measured in Ca(2+)-free (2mM EGTA) Krebs. To test for Ca(2+)-dependent effects, IVC segments were pretreated with escin or diosmin (10(-4) M) in 0 Ca(2+) Krebs, then extracellular CaCl(2) (0.1, 0.3, 0.6, 1, 2.5 mM) was added and the [Ca(2+)](e)-contraction relationship was constructed. To test for synergistic effects of diosmin, IVC segments were pretreated with diosmin (10(-4) M), then stimulated with KCl (16-96 mM) or escin (10(-10) to 10(-4) M) and vein contraction was measured. Contraction data were presented as mg/mg tissue (means ± SEM).

RESULTS

In IVC segments incubated in normal Krebs (2.5 mM Ca(2+)), escin caused concentration-dependent contraction (max 104.3 ± 19.6 at 10(-4) M). Escin-induced contraction was not a rigor state, because after washing with Krebs, the veins returned to a relaxed state. In Ca(2+)-free Krebs, there was essentially no contraction to escin. In escin-treated veins incubated in 0 Ca(2+) Krebs, stepwise addition of extracellular CaCl(2) caused corresponding increases in contraction (max 80.0 ± 11.1 at 2.5 mM). In the absence of escin, the α-adrenergic agonist phenylephrine (PHE, 10(-5) M), angiotensin II (AngII, 10(-6) M), and membrane depolarization by KCl (96 mM) caused significant contraction (122.5 ± 45.1, 114.2 ± 12.2 and 221.7 ± 35.4, respectively). In IVC segments pretreated with escin (10(-4) M), the contractile response to PHE (9.7 ± 2.6), AngII (36.0 ± 9.1), and KCl (82.3 ± 10.2) was significantly reduced. Diosmin (10(-4) M) caused small contractions in normal Krebs (11.7 ± 1.9) and Ca(2+)-free Krebs (4.2 ± 2.2). In diosmin-treated veins incubated in 0 Ca(2+) Krebs, addition of extracellular CaCl(2) caused minimal contraction. Diosmin did not enhance the IVC contraction to PHE, AngII, or escin, but enhanced the contractile response to KCl (24-51 mM).

CONCLUSION

In rat IVC, escin induces extracellular Ca(2+)-dependent contraction, but disrupts α-adrenergic and AT(1)R receptor-mediated pathways and depolarization-induced contraction. The initial venotonic benefits of escin may be offset by disruption of vein response to endogenous venoconstrictors, limiting its long-term therapeutic benefits in varicose veins. Diosmin does not cause venous contraction or potentiate the venotonic effects of endogenous venoconstrictors or escin ex vivo, and its use as venotonic may need to be further evaluated.

Pharmacological treatment of primary chronic venous disease: rationale, results and unanswered questions

AIM

The aim of this article was first to review the complex pathophysiological mechanisms responsible for symptoms and signs of primary chronic venous disease (CVD) that allow the identification of targets for pharmacological treatment. The results of CVD treatment with venoactive drugs (VADs) were emphasised and presented in the form of recommendations. The last section raises key questions to be answered to improve protocols for good clinical trials and to draw up future guidelines on these agents.

METHODS

The literature has been reviewed here using PubMed and Embase.

RESULTS

Venous hypertension appears to underlie all clinical manifestations of primary CVD. Inflammation is key in wall remodelling, valve failure and subsequent venous hypertension. Changes in the haemodynamics of veins are transmitted to the microcirculation, resulting in capillary alteration leading to oedema, skin changes and eventually venous ulceration. Venous symptoms may be the result of interplays between pro-inflammatory mediators and nerve fibres located in the venous wall. Therefore, venous inflammation constitutes a promising therapeutic target for pharmacological intervention, and some available VADs could attenuate various elements of venous inflammation. Based on recent studies, reviews and guidelines, tentative recommendations for the use of VADs were proposed and strong recommendations were given to two of them (micronised purified flavonoid fraction and oxerutins).

CONCLUSION

VADs should be accorded a better role in the management of CVD. However, larger and more definitive clinical trials are needed to improve the existing recommendations.

Prolonged mechanical stretch is associated with upregulation of hypoxia-inducible factors and reduced contraction in rat inferior vena cava

BACKGROUND

Decreased venous tone and vein wall dilation may contribute to varicose vein formation. We have shown that prolonged vein wall stretch is associated with upregulation of matrix metalloproteases (MMPs) and decreased contraction. Because hypoxia-inducible factors (HIFs) expression also increases with mechanical stretch, this study tested whether upregulation of HIFs is an intermediary mechanism linking prolonged vein wall stretch to the changes in MMP expression and venous contraction.

METHODS

Segments of rat inferior vena cava (IVC) were suspended in tissue bath under 0.5-g basal tension for 1 hour, and a control contraction to phenylephrine (PHE, 10(-5)M) and KCl (96 mM) was elicited. The veins were then exposed to prolonged 18 hours of tension at 0.5 g, 2 g, 2 g plus HIF inhibitor U0126 (10(-5)M), 17-[2-(dimethylamino)ethyl] amino-17-desmethoxygeldanamycin (17-DMAG, 10(-5)M), or echinomycin (10(-6)M), or 2 g plus dimethyloxallyl glycine (DMOG; 10(-4)M), a prolyl-hydroxylase inhibitor that stabilizes HIF. The fold-change in PHE and KCl contraction was compared with the control contraction at 0.5-g tension for 1 hour. Vein tissue homogenates were analyzed for HIF-1α, HIF-2α, MMP-2, and MMP-9 messenger RNA (mRNA) and protein amount using real-time reverse transcription polymerase chain reaction and Western blots.

RESULTS

Compared with control IVC contraction at 0.5-g tension for 1 hour, the PHE and KCl contraction after prolonged 0.5-g tension was 2.0 ± 0.35 and 1.1 ± 0.06, respectively. Vein contraction to PHE and KCl after prolonged 2-g tension was significantly reduced (0.87 ± 0.13 and 0.72 ± 0.05, respectively). PHE-induced contraction was restored in IVC exposed to prolonged 2-g tension plus the HIF inhibitor U0126 (1.38 ± 0.15) or echinomycin (1.99 ± 0.40). U0126 and echinomycin also restored KCl-induced contraction in IVC exposed to prolonged 2-g tension (1.14 ± 0.05 and 1.11 ± 0.15, respectively). Treatment with DMOG further reduced PHE- and KCl-induced contraction in veins subjected to prolonged 2-g tension (0.47 ± 0.06 and 0.57 ± 0.01, respectively). HIF-1α and HIF-2α mRNA were overexpressed in IVC exposed to prolonged 2-g tension, and the overexpression was reversed by U0126. The overexpression of HIF-1α and HIF-2α in stretched IVC was associated with increased MMP-2 and MMP-9 mRNA. The protein amount of HIF-1α, HIF-2α, MMP-2, and MMP-9 was also increased in IVC exposed to prolonged 2-g wall tension.

CONCLUSIONS

Prolonged increases in vein wall tension are associated with overexpression of HIF-1α and HIF-2α, increased MMP-2 and MMP-9 expression, and reduced venous contraction in rat IVC. Together with our report that MMP-2 and MMP-9 inhibit IVC contraction, the data suggest that increased vein wall tension induces HIF overexpression and causes an increase in MMP expression and reduction of venous contraction, leading to progressive venous dilation and varicose vein formation.

Acute venous occlusion enhances matrix metalloprotease activity: Implications on endothelial dysfunction

Venous hypertension is associated with microvascular inflammation, restructuring, and apoptosis, but the cellular and molecular mechanisms underlying these events remain uncertain. In the present study, we tested the hypothesis that elevated venous pressure and reduction of shear stress induce elevated enzymatic activity. This activity in turn may affect endothelial surface receptors and promote their dysfunction. Using a rodent model for venous hypertension using acute venular occlusion, microzymographic techniques for enzyme detection, and immunohistochemistry for receptor labeling, we found increased activity of the matrix metalloproteases (MMPs) -1, -8, and -9 and tissue inhibitors of metalloproteases (TIMPs) -1 and -2 in both high- and low-pressure regions. In this short time frame, we also observed that elevated venule pressure led to two different fates for the vascular endothelial growth factor receptor-2 (VEGFR2); in higher-pressure upstream regions, some animals exhibited higher VEGFR2 expression, while others displayed lower levels upstream compared to their downstream counterparts with lower pressure. VEGFR2 expression was, on average, more pronounced upon application of MMP inhibitor, suggesting possible cleavage of the receptor by activated enzymes in this model. We conclude that venous pressure elevation increases enzymatic activity which may contribute to inflammation and endothelial dysfunction associated with this disease by influencing critical surface receptors.

Estrogen receptor-mediated enhancement of venous relaxation in female rat: implications in sex-related differences in varicose veins

BACKGROUND

A greater incidence of varicose veins has been reported in premenopausal women than in men. We hypothesized that the sex differences in venous function reflect reduced constriction and enhanced venous dilation in women due to direct venous relaxation effects of estrogen on specific estrogen receptors (ER).

METHODS

Circular segments of inferior vena cava (IVC) from male and female Sprague-Dawley rats were suspended between two wires, and isometric contraction (in mg/mg tissue) to phenylephrine, angiotensin II (AngII), and 96 mM KCl was measured. To investigate sex differences in venous smooth muscle, Ca(2+) release from the intracellular stores, and Ca(2+) entry from the extracellular space, the transient phenylephrine contraction in 0 Ca(2+) Krebs was measured. Extracellular CaCl(2) (0.1, 0.3, 0.6, 1, 2.5 mM) was added, and the [Ca(2+)](e)-dependent contraction was measured. To investigate sex differences in venous endothelial function, acetylcholine-induced relaxation was measured. To test the role of specific ERs, the amount of venous tissue ERs was measured using Western blots, and the venous relaxation in response to 17beta-estradiol (E2, activator of most ERs), 4,4,'4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)-tris-phenol (PPT; ERalpha agonist), 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN; ERbeta agonist), and ICI 182,780 (ERalpha/ERbeta antagonist, and G protein-coupled receptor 30 [GPR30] agonist) was measured in IVC segments nontreated or treated with the nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME).

RESULTS

Phenylephrine caused concentration-dependent contraction that was less in female (max 104.2 +/- 16.2) than male IVC (172.4 +/- 20.4). AngII (10(-6))-induced contraction was also less in female (81.0 +/- 11.1) than male IVC (122.5 +/- 15.0). Phenylephrine contraction in 0 Ca(2+) Krebs was insignificantly less in female (4.8 +/- 1.8) than male IVC (7.2 +/- 1.7), suggesting little difference in the intracellular Ca(2+) release mechanism. In contrast, the [Ca(2+)](e)-dependent contraction was significantly reduced in female than male IVC. Also, contraction to membrane depolarization by 96 mM KCl, which stimulates Ca(2+) influx, was less in female (129.7 +/- 16.7) than male IVC (319.7 +/- 30.4), supporting sex differences in Ca(2+) entry. Acetylcholine relaxation was greater in female (max 80.6% +/- 4.1%) than male IVC (max 48.0% +/- 6.1%), suggesting sex differences in the endothelium-dependent relaxation pathway. Western blots revealed greater amounts of ERalpha, ERbeta, and GPR30 in female than male IVC. ER agonists caused concentration-dependent relaxation of phenylephrine contraction in female IVC. E2-induced relaxation (max 76.5% +/- 3.4%) was more than DPN (74.8% +/- 9.1%), PPT (71.4% +/- 12.5%), and ICI 182,780 (67.4% +/- 7.8%), and was similar in L-NAME-treated and nontreated IVC.

CONCLUSION

The reduced alpha-adrenergic, AngII, depolarization-induced, and [Ca(2+)](e)-dependent venous contraction in female rats is consistent with sex differences in the Ca(2+) entry mechanisms, possibly due to enhanced endothelium-dependent vasodilation and increased ER expression/activity in female rats. E2/ER-mediated venous relaxation in female rats is not prevented by NOS blockade, suggesting activation of an NO-independent relaxation pathway. The decreased venous contraction and enhanced E2/ER-mediated venous relaxation would lead to more distensible veins in female rats.

Functional adaptation of venous smooth muscle response to vasoconstriction in proximal, distal, and varix segments of varicose veins

BACKGROUND

Varicose veins (VarVs) are a common disorder of venous dilation and tortuosity with unclear mechanism. The functional integrity and the ability of various regions of the VarVs to constrict is unclear. This study tested the hypothesis that the different degrees of venodilation in different VarV regions reflect segmental differences in the responsiveness to receptor-dependent vasoconstrictive stimuli and/or in the postreceptor signaling mechanisms of vasoconstriction.

METHODS

Varix segments and adjacent proximal and distal segments were obtained from patients undergoing VarV stripping. Control great saphenous vein specimens were obtained from patients undergoing lower extremity arterial bypass and coronary artery bypass grafting. Circular vein segments were equilibrated under 2 g of tension in a tissue bath, and changes in isometric constriction in response to angiotensin II (AngII, 10(-11)-10(-7) M), phenylephrine (PHE, 10(-9)-10(-4) M), and KCl (96 mM) were recorded. The amount of angiotensin type 1 receptor (AT(1)R) was measured in vein tissue homogenate.

RESULTS

AngII caused concentration-dependent constriction in control vein (max 35.3 +/- 9.6 mg/mg tissue, pED(50) 8.48 +/- 0.34). AngII caused less contraction and was less potent in proximal (max 7.9 +/- 2.5, pED(50) 6.85 +/- 0.61), distal (max 5.7 +/- 1.2, pED(50) 6.74 +/- 0.68), and varix segments of VarV (max 7.2 +/- 2.0, pED(50) 7.11 +/- 0.50), suggesting reduced AT(1)R-mediated contractile mechanisms. VarVs and control veins had similar amounts of AT(1)R. alpha-adrenergic receptor stimulation with PHE caused concentration-dependent constriction in control veins (max 73.0 +/- 13.9 mg/mg tissue, pED(50) 5.48 +/- 0.12) exceeding that of AngII. PHE produced similar constriction and was equally potent in varix and distal segments but produced less constriction and was less potent in proximal segments of VarVs (max 32.1 +/- 6.4 mg/mg tissue, pED(50) 4.89 +/- 0.13) vs control veins. Membrane depolarization by 96 mM KCl, a receptor-independent Ca(2+)-dependent response, produced significant constriction in control veins and similar contractile response in proximal, distal, and varix VarV segments, indicating tissue viability and intact Ca(2+)-dependent contraction mechanisms.

CONCLUSIONS

Compared with control veins, different regions of VarV display reduced AngII-mediated venoconstriction, which may be involved in the progressive dilation in VarVs. Postreceptor Ca(2+)-dependent contraction mechanisms remain functional in VarVs. The maintained alpha-adrenergic responses in distal and varix segments, and the reduced constriction in the upstream proximal segments, may represent a compensatory adaptation of human venous smooth muscle to facilitate venous return from the dilated varix segments of VarV.

Mechanical buckling of veins under internal pressure

Venous tortuosity is associated with multiple disease states and is often thought to be a consequence of venous hypertension and chronic venous disease. However, the underlying mechanisms of vein tortuosity are unclear. We hypothesized that increased pressure causes vein buckling that leads to a tortuous appearance. The specific aim of this study was to determine the critical buckling pressure of veins. We determined the buckling pressure of porcine jugular veins and measured the mechanical properties of these veins. Our results showed that the veins buckle when the transmural pressure exceeds a critical pressure that is strongly related to the axial stretch ratio in the veins. The critical pressures of the eight veins tested were 14.2 +/- 5.4 and 26.4 +/- 9.0 mmHg at axial stretch ratio 1.5 and 1.7, respectively. In conclusion, veins buckle into a tortuous shape at high lumen pressures or reduced axial stretch ratios. Our results are useful in understanding the development of venous tortuosity associated with varicose veins, venous valvular insufficiency, diabetic retinopathy, and vein grafts.

Elevated sex steroid hormones in great saphenous veins in men

INTRODUCTION

High serum levels of estradiol are associated with clinical evidence of varicose veins in women; however, the relationship between serum sex steroid hormones and varicose veins in men is unclear. To address this issue, serum levels of testosterone, estradiol, and androstenedione were determined in the great saphenous (GSV) and cubital veins of men with varicose veins. Messenger RNA (mRNA) expression of sex steroid hormones, metabolizing enzymes, and their receptors was investigated in tissue samples of leg veins.

METHODS

This prospective study included 40 men, comprising 20 with varicose veins and reflux of the GSV (VM) and 20 with healthy veins (HM). All limbs were assessed by duplex ultrasound scanning of selected superficial and deep leg veins. Blood samples were taken from the cubital vein and from the GSV. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) analysis for sex steroid hormones, their metabolizing enzymes, and receptors in saphenous veins was performed in tissue samples of varicose (n = 6) and healthy veins (n = 6).

RESULTS

The VM group had significantly higher (P < .001) mean levels for serum testosterone (44.9 nmol/L; range, 8.8-225.1) and estradiol (242.2 pmol/L; range, 79-941) in varicose saphenous veins compared with cubital veins (testosterone, 15.5 nmol/L; range, 8.4-23.3; estradiol, 93.2 pmol/L; range, 31-147). Moreover, significantly (P < .001) higher mean serum estradiol levels (133.2 pmol/L; range, 63-239) were detected in the saphenous veins of the HM group compared with cubital veins (88.15 pmol/L; range, 37-153). Both groups had similar blood counts and serum androstenedione levels in the upper and lower extremity. Interestingly, qRT-PCR revealed that the mRNA expression of 5alpha-reductase type 1, 5alpha-reductase type 2, 17, 20 lyase, 17beta-hydroxysteroid dehydrogenase (17beta-HSD), aromatase and 3beta-HSD type 2, androgen and estrogen receptor 1 was down-regulated (P < .05) in all samples of varicose veins vs veins obtained from healthy men.

CONCLUSION

Elevated serum estradiol and testosterone levels were detected in men with varicose veins and reflux in the GSV compared with the patient's own arm veins. Enzymes and hormonal receptors involved in steroid metabolism were down-regulated in patients with GSV reflux and varicose veins, suggestive of a negative feedback regulation. These data support the notion of a possible causal relationship between sex steroids and varicose veins in men.

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.

Sex-related decrease in [Ca2+]i signaling and Ca2+-dependent contraction in inferior vena cava of female rat

Sex differences in the incidence of varicose veins have been suggested; however, the venous mechanisms involved are unclear. We hypothesized sex-related differences in venous function and underlying distinctions in intracellular free calcium, [Ca(2+)](i), signaling and Ca(2+)-dependent mechanisms of venous contraction. Circular segments of inferior vena cava (IVC) from male and female Sprague-Dawley rats were suspended between two hooks, labeled with fura-2, and placed in a cuvet inside a spectrofluorometer for simultaneous measurement of isometric contraction and the 340/380 fluorescence ratio (indicative of [Ca(2+)](i)). In male IVC, phenylephrine (PHE; 10(-5) M) caused significant increase in contraction and [Ca(2+)](i). In female IVC, PHE-induced contraction was significantly reduced, but [Ca(2+)](i) did not differ significantly from males. Membrane depolarization by KCl (96 mM), which stimulates Ca(2+) influx, caused parallel increases in contraction and [Ca(2+)](i) in male IVC, and the KCl-induced contraction was significantly reduced in parallel with [Ca(2+)](i) in female IVC. In male IVC stimulated with 0 Ca(2+) KCl solution, the addition of increasing concentrations of extracellular Ca(2+) ([Ca(2+)](e)) (0.1, 0.3, 0.6, 1, and 2.5 mM) caused stepwise increases in contraction and [Ca(2+)](i), and both the KCl-induced [Ca(2+)](e)-contraction curve and the [Ca(2+)](e)-[Ca(2+)](i) curve were reduced in female IVC, suggesting reduced Ca(2+) entry via voltage-gated channels. The PHE-induced [Ca(2+)](e)-contraction curve was significantly reduced in females, but the [Ca(2+)](e)-[Ca(2+)](i) curve was similar in female and male IVC, suggesting the involvement of other mechanisms in addition to Ca(2+) entry. The [Ca(2+)](e)-contraction and [Ca(2+)](e)-[Ca(2+)](i) curves were used to construct the [Ca(2+)](i)-contraction relationship. The KCl-induced [Ca(2+)](i)-contraction relationship was superimposed in male and female IVC. In contrast, the PHE-induced [Ca(2+)](i)-contraction relationship was reduced and located to the right in female compared with male IVC, suggesting reduced [Ca(2+)](i) sensitivity of the venous contractile myofilaments. The reduced contraction, [Ca(2+)](i), and [Ca(2+)](i) sensitivity in female veins render them more prone to dilation. These sex-specific reductions in venous function, if they also occur in human veins, may play a role in the greater incidence of varicose veins in females.

In vitro differences between smooth muscle cells derived from varicose veins and normal veins

OBJECTIVE

The theory of primary venous dilatation leading to secondary valvular incompetence and varicose vein formation has received more attention nowadays. Although many studies have investigated the role of the main components of the venous wall in the development of varicose veins, the leading cause remains unknown. The present study was designed to establish the role of smooth muscle cells (SMCs) of the tunica media on the pathogenesis of varicose veins by analyzing the phenotypic and functional differences between SMCs derived from varicose veins and normal veins.

METHODS

SMCs were isolated and cultured from saphenous veins of patients with varicose veins and normal veins. Cell proliferation and migration rates were compared. Expression of phenotype-dependent markers and matrix metalloproteinase-2 (MMP) production were analyzed by immunoblotting. Total collagen synthesis was evaluated by measuring the radioactivity of L-[3, 4-(3)H]proline in the media and the cell layer.

RESULTS

SMCs derived from varicose veins demonstrated increased proliferation (2-fold, P < .01), migration (3-fold, P < .001), MMP-2 production (3-fold, P < .01), and collagen synthesis (>2-fold, P < .001), with decreased expression of phenotype-dependent markers compared with SMCs derived from normal veins (P < .05).

CONCLUSION

SMCs derived from varicose veins are more dedifferentiated and demonstrate increased proliferative and synthetic capacity than SMCs derived from normal veins. These properties may contribute to the remodeling of the venous wall and the weakening of its antipressure capacity.

Prolonged increases in vein wall tension increase matrix metalloproteinases and decrease constriction in rat vena cava: Potential implications in varicose veins

BACKGROUND

Increased venous hydrostatic pressure plays a role in the pathogenesis of varicose veins. Increased expression of matrix metalloproteinases (MMPs) has been identified in varicose veins. Also, we have shown that MMP-2 inhibits venous contraction. However, the relation between venous pressure, MMP expression, and venous dysfunction is unclear. The purpose of this study was to test the hypothesis that prolonged increases in venous wall tension cause overexpression of MMPs and decreased contractility, which in turn promote venous dilation.

METHODS

Circular segments of inferior vena cava (IVC) were isolated from male Sprague-Dawley rats and suspended between two wires in Krebs solution. Preliminary vein wall tension-contraction relation showed maximal potassium chloride (KCl) (96 mmol/L) contraction at 0.5 g basal tension, which remained steady with increases in tension up to 2 g. Vein segments were subjected to either control (0.5 g) or high (2 g) basal tension for short (1 hour) or long duration (24 hours). Isometric contraction in response to phenylephrine (Phe, 10(-5) mol/L), angiotensin II (AngII, 10(-6) mol/L), and KCl was measured. The veins were frozen to determine the expression and localization of MMPs using immunoblots and immunohistochemistry.

RESULTS

In IVC segments subjected to 0.5 g tension for 1 hour, Phe and AngII produced significant contraction. At higher 2 g basal tension for 24 hours, both Phe and AngII contractions were significantly reduced. Reduction in KCl contraction was also observed at high 2 g basal tension for 24 hours, suggesting that the reduction in vein contraction is not specific to a particular receptor, and likely involves inhibition of a post-receptor contraction mechanism. In vein segments under 2 g tension for 24 hours and treated with TIMP-1, Phe, AngII, and KCl contractions were partially restored, suggesting the involvement of MMPs. IVC immunoblot analysis demonstrated prominent bands corresponding to MMP-2 and MMP-9 protein. High 2 g wall tension for 24 hours was associated with marked increase in the amount of MMP-2 and -9 relative to the housekeeping protein actin. There was a correlation between MMP expression and decreased vein contraction. Also, significant increases in MMP-2 and -9 immunostaining were observed in IVC segments subjected to high 2 g tension for 24 hours. Both MMP-2 and MMP-9 caused significant inhibition of Phe contraction in IVC segments.

CONCLUSIONS

In rat IVC, increases in magnitude and duration of wall tension is associated with reduced contraction and overexpression of MMP-2 and -9. In light of our findings that MMP-2 and -9 promote IVC relaxation, the data suggest that protracted increases in venous pressure and wall tension increase MMPs expression, which in turn reduce venous contraction and lead to progressive venous dilation.