Genetics of varicose veins of the lower extremities

Global Expression Profiling Identifies a Novel Hyaluronan Synthases 2 Gene in the Pathogenesis of Lower Extremity Varicose Veins

Lower extremities varicose veins (VV) are among the most easily recognized venous abnormalities. The genetic mechanism of VV is largely unknown. In this study, we sought to explore the global expressional change of VV and identify novel genes that might play a role in VV. We used next-generation ribonucleic acid (RNA) sequence (RNA seq) technology to study the global messenger RNA expressional change in the venous samples of five diseased and five control patients. We identified several differentially expressed genes, which were further confirmed by conventional reverse transcription polymerase chain reaction (RT-PCR). Using these significant genes we performed in silico pathway analyses and found distinct transcriptional networks, such as angiogenesis, cell adhesion, vascular injury, and carbohydrate metabolisms that might be involved in the mechanism of VV. Among these significant genes, we also found hyaluronan synthases 2 gene (HAS2) played a pivotal role and governed all these pathways. We further confirmed that HAS2 expression was decreased in the venous samples of patients with VV. Finally, we used a zebrafish model with fluorescence emitting vasculature and red blood cells to see the morphological changes of the venous system and blood flow. We found that HAS2 knockdown in zebrafish resulted in dilated venous structural with static venous flow. HAS2 may modulate the transcriptional networks of angiogenesis, cell adhesion, vascular injury, and carbohydrate metabolisms in venous tissues and downregulation of HAS2 may underlie the mechanism of VV.

Pelvic congestion syndrome: etiology of pain, diagnosis, and clinical management

Pelvic congestion syndrome is associated with pelvic varicosities that result in chronic pelvic pain, especially in the setting of prolonged standing, coitus, menstruation, and pregnancy. Although the underlying pathophysiology of pelvic congestion syndrome is unclear, it probably results from a combination of dysfunctional venous valves, retrograde blood flow, venous hypertension, and dilatation. Asymptomatic women may also have pelvic varicosities, making pelvic congestion syndrome difficult to diagnose. This article explores the etiologies of pain, use of imaging techniques, and clinical management of pelvic congestion syndrome. Possible explanations for the spectrum of pain among women with pelvic varicosities are also discussed.

A genetic study of chronic venous insufficiency

BACKGROUND

Chronic venous insufficiency (CVI) is an important cause of morbidity in Western countries. The aim of this study is to demonstrate the heredity of CVI, focusing on molecular and genetic aspects of the disease.

METHODS

The study depended on the recruitment of informative families, accurate determination of the phenotype of each family member, and blood sample for DNA extraction for genetic analysis. Each family member was invited to attend a vascular consultation. A genealogical tree for each recruited family was composed. Then, a peripheral blood sample for DNA extraction from each member of the recruited families was obtained for genetic evaluation.

RESULTS

By the evaluation of genealogical trees, it was evident that CVI segregates, in all families studied, in an autosomal dominant mode with incomplete penetrance. In nine families studied, varicose veins were linked to the candidate marker D16S520 on chromosome 16q24, which may account for the linkage to FOXC2.

CONCLUSION

In our study, in families with affected patients with the D16S520 marker, there was evidence of saphenofemoral junction reflux. The fact that there is linkage to a candidate marker for the FOXC2 gene suggests there is a functional variant within, or in the vicinity of, which predisposes to varicose veins. Further studies are necessary to identify genes and mechanism so as to achieve better understanding of the genetic basis of CVI.

Linkage to the FOXC2 region of chromosome 16 for varicose veins in otherwise healthy, unselected sibling pairs

BACKGROUND

The FOXC2 gene on 16q24 is mutated in lymphoedema distichiasis (LD), in which varicose veins (VV) are a common feature. We hypothesised that this gene might be implicated in the development of VV in the normal population, therefore, after performing a classical twin study, we tested for linkage and association in white women. We also tested for linkage with haemorrhoids (H), as a separate venous anomaly at the same locus.

METHODS

A total of 2060 complete female twin pairs aged 18-80 years from the St Thomas' Adult UK Twin registry replied to questions on VV and H as part of a broader postal survey of 6600 twins (62% response rate). Dizygotic female twin pairs were tested for linkage and association to the candidate marker D16S520 (1903 individuals genotyped), which is located about 80 kb from FOXC2.

RESULTS

Casewise concordance rates were significantly higher for monozygotic than dizygotic twins for both phenotypes (VV 67% v 45%; p = 2.2x10(-6); H 68% v 59%; p = 0.01; H including during pregnancy 73% v 64%; p = 2.1x10(-4)), corresponding to additive genetic heritabilities in liability of 86% (95% confidence interval (CI) 73% to 99%) for VV and 56-61% for H (95% CI 43% to 73%). The presence of VV and H were significantly correlated. We found significant evidence of linkage to the marker for VV (MLS(ASP) = 1.37, p = 0.01; GLM(ASP/DSP) Z = 3.17 p = 0.002), but no association. Both linkage and association tests were negative for H. The combined phenotype of having VV and H did not show any evidence of linkage or association.

CONCLUSION

These results demonstrate VV and H to be heritable, related conditions, and the data strongly suggest FOXC2 to be implicated in the development of VV in the general population.

Chronic venous insufficiency: the genetic influence

Many contributing factors are involved in the genesis of varicose disease of the lower limbs such as age, sex, heredity, sedentary life style among others. For physicians the decisive role played by heredity leaves no doubt. Few studies have, however, attempted to prove the importance of the hereditary factor on a clinical level, and no study has been conducted in molecular genetics. The impact of the hereditary factor is variably estimated and its nature is open to discussion. Despite the numerous limits of the research focusing on the hereditary aspect of varicose disease, the authors can nevertheless claim that the genetic factor definitively exists and has a great impact. There are few studies conducted among twins. The data collected in these studies point to the reality of various types of heredity. With the predominant impact of the hereditary factor, and despite the role played by environmental factors, it can be supposed that a single genetic anomaly may be the determining factor of the disease in a given family. Thus we have conducted an original study in order to identify one or several mutations predisposing to varicose disease, based on the approach called "reverse genetic" and linkage study. The study of a first family whose varicose disease segregates in an autosomal dominant manner allowed us to identify 3 potential loci, if we accept the hypothesis of 2 or 3 phenocopies. No candidate gene has been singled out in these regions in the first analysis. The study of a second family whose phenotype of the varicose disease is particularly homogeneous and segregates in an autosomal dominant manner did not confirm any of the previously identified loci, probably related to a genetic heterogeneity of the varicose disease. As a consequence, the second part of this study was devoted to determining the complete genotype of each individual within this family, in order to identify new loci of interest. A potential locus has just been identified. The third part of this research, currently being pursued, is devoted to the sequencing of potential genes. In parallel, the analysis of new large families is underway. The presentation will include an update on the hereditary and genetic aspects of varicose disease, and secondly identify the limits and difficulties of the genetic study of the families.

Assessment of wall structure and composition of varicose veins with reference to collagen, elastin and smooth muscle content

OBJECTIVES

To compare collagen, elastin and smooth muscle contents of varicose and control long saphenous veins.

DESIGN

Collagen, elastin and muscle were estimated stereologically using random sampling and histological staining.

MATERIALS

Varicose vein samples were collected from nine patients (mean age 52 years, range 34-64 years) undergoing vein stripping, sample sites being saphenofemoral junction and knee. Control samples were taken from five patients (mean age 58 years, range 38-76 years) presenting for femoral-popliteal bypass at equivalent levels.

METHODS

Veins were fixed, sectioned transversely, and stained with Picric Acid Sirius Red. Analysis of samples was performed using point and intersection counting on vertically projected images.

RESULTS

Using two way analysis of variance tests, varicose saphenous veins had significantly larger wall areas (p < 0.01) and higher amounts of collagen (p < 0.01). Collagen content and wall area were significantly larger proximally compared to distally in both control and varicose veins (p < 0.05) with a higher content of smooth muscle and elastin in varicose veins proximally compared to distally (p < 0.05). There was no difference in wall thickness or elastin content between the two groups.

CONCLUSIONS

This suggests that varicose veins are a dynamic response to venous hypertension and are not thin walled structures as previously thought.

Importance of the familial factor in varicose disease. Clinical study of 134 families

BACKGROUND

The role of heredity in the development of varicose veins of the lower limbs has been raised many times in the literature. When evaluating this role, most authors only question the patients, without examining their relatives. As shown in other papers, the subjectivity of this type of data throws doubt on the results.

OBJECTIVE

This problem was evaluated by means of a prospective study based on clinical examination of all immediate family members.

METHODS

In the case-control study, the female or male patients had to satisfy the following criteria: 1. Varicose veins in their legs. 2. Age between 30 and 40 years (meaning that, in most cases, their parents were still alive). 3. No history of deep vein thrombosis. To limit the influence of certain confusing factors (diet, life-style), the control group was composed of the patients' spouses, who were not suffering from varicose veins. The parents of the cases and the parents of the controls were also examined. For each case-control couple and for the four parents, we recorded the history of venous disease, the life-style, and the results of clinical examination, including the results of palpation and percussion of the various varicose vein territories.

RESULTS

One hundred and thirty-four families were examined: 67 patients and their parents and 67 controls and their parents. A total of 402 subjects were examined. The results demonstrated a prominent role of heredity in the development of varicose veins (P < .001). The risk of developing varicose veins for the children was 90% when both parents suffered from this disease, 25% for males and 62% for females when one parent was affected, and 20% when neither parent was affected.

The load of genetic and partially genetic diseases in man. II. Some selected common multifactorial diseases: estimates of population prevalence and of detriment in terms of years of lost and impaired life

This paper presents epidemiological data on the prevalence of 26 common (i.e., having a lifetime prevalence of more than 1 per 10(4) individuals in the population) multifactorial diseases in Hungary and estimates of detriment associated with them. The detriment is expressed using 3 indicators, namely years of lost life (LL), potentially impaired life (PIL) and actually impaired life (AIL). The total prevalence of these diseases in Hungary has been estimated to be about 6500 per 10(4) individuals in the population. This estimate is in agreement with published data for other parts of the world. On the basis of clinical severity, these diseases have been split into 3 groups, namely (1) very severe (schizophrenia, multiple sclerosis, epilepsy, acute myocardial infarction and related conditions, and systemic lupus erythematosus); (2) moderately severe and/or episodal or seasonal (15 entities including Graves' disease, diabetes mellitus, gout, affective psychoses, essential hypertension, peptic ulcers, asthma, etc.); and (3) less severe than those in the first 2 groups (varicose veins, allergic rhinitis, atopic dermatitis, Scheuermann disease and adolescent idiopathic scoliosis). The essential clinical and genetic aspects of these diseases are briefly discussed. With the exception of epilepsy, none of the diseases included in our list causes mortality between ages 0 and 19. However, they are among the leading causes of death between ages 20 and 69 and thereafter. A sizeable proportion of those with essential hypertension, diabetes mellitus, rheumatoid arthritis, etc. survive to 70 years and beyond, as do those with gout, glaucoma, allergic rhinitis, psoriasis, etc. Overall, about 16% of all deaths that occur in Hungary every year (all age groups) can be attributed to these diseases. The mean number of years of PIL covers a wide range (about 20-40, 12-70 and 40-60 for groups 1, 2 and 3, respectively), the overall mean being about 24 years. However, the nature and degree of impairment and the impact on the life quality of those afflicted differ for the different diseases. Likewise, the mean number of years of AIL (for which the interval between the mean age at premature retirement and mean age at death was used as a rough index) also spans a wide range from 16 to 45, and the overall mean is about 20 years. At the population level, the diseases considered in this paper cause about 2700 years of LL, 96,000 years of PIL and about 5800 years of AIL per 10(4) individuals in the population. Relative to Mendelian diseases as a whole, these multifactorial diseases are associated with much greater detriment (LL: 1.4 X; PIL: 30 X and AIL: 3.9 X).

Comparative study of the distribution of venous valves in the lower extremities of black Africans and Caucasians: pathogenetic correlates of prevalence of primary varicose veins in the two races

The incidence of valves in the major veins of the lower extremities of Africans and Caucasians was studied. Valves are absent in the inferior vena cava in both races. In the common iliac veins, 1-7% of Caucasians and 1% of Africans have rudimentary valves. Normal valves exist in the following veins: the external iliac veins--22-33% of Caucasians and 9% of Africans; the femoral vein segment above the saphenofemoral junction--67-81% of Caucasians and 93% of Africans; the 3-cm-length of the femoral vein below the profundofemoral junction--90% of Caucasians and 100% of Africans; the terminal 3 cm of the great saphenous vein--100% Caucasians and 98% Africans. The lower incidence in the number of valves in Caucasians may account for the high prevalence (10-18%) of varicose veins in Caucasians; the reverse of this relationship is suggested for the low prevalence (1-2%) of the condition in Africans. Factors influencing the development of incompetent valves are discussed.