Varicose veins of lower extremities: Insights from the first large-scale genetic study

Varicose veins of lower extremities (VVs) are a common multifactorial vascular disease. Genetic factors underlying VVs development remain largely unknown. Here we report the first large-scale study of VVs performed on a freely available genetic data of 408,455 European-ancestry individuals. We identified the 12 reliably associated loci that explain 13% of the SNP-based heritability, and prioritized the most likely causal genes CASZ1, PIEZO1, PPP3R1, EBF1, STIM2, HFE, GATA2, NFATC2, and SOX9. VVs-associated variants within these loci exhibited pleiotropic effects on several phenotypes including blood pressure/hypertension and blood cell traits. Gene set enrichment analysis revealed gene categories related to abnormal vasculogenesis. Genetic correlation analysis confirmed known epidemiological associations between VVs and deep venous thrombosis, weight, rough labor, and standing job, and found a genetic overlap with multiple traits that have not been previously suspected to share common genetic background with VVs. These traits included educational attainment, fluid intelligence and prospective memory scores, walking pace (negative correlation with VVs), smoking, height, number of operations, pain, and gonarthrosis (positive correlation with VVs). Finally, Mendelian randomization analysis provided evidence for causal effects of plasma levels of MICB and CD209 proteins, and anthropometric traits such as waist and hip circumference, height, weight, and both fat and fat-free mass. Our results provide novel insight into both VVs genetics and etiology. The revealed genes and proteins can be considered as good candidates for follow-up functional studies and might be of interest as potential drug targets.

Varicose veins of lower extremities (VVs) affect about 30% of adults in developed countries and cause both cosmetic and health problems. A strong body of evidence indicates that heredity plays an important role in the etiology of this condition. However, genetic basis of VVs remains poorly understood. Here, we present the results of the first large-scale genetic study for VVs. We identified genes which are the most likely involved in VVs pathogenesis. We show that VVs are correlated at a genetic level with numerous traits and phenotypes, including those already known from prior epidemiological studies (deep venous thrombosis, body mass index, standing job, etc.) as well as with those that have not been suspected to share common genetic background with VVs (fluid intelligence and prospective memory scores, smoking, walking pace, pain all over the body, and other traits). Finally, using genetic variants as instruments, we demonstrate direct causal effects of the traits related to anthropometry, such as height and weight, and plasma levels of immune-related proteins MICB and CD209. Our study provides novel insight into both VVs genetics and etiology. The revealed genes (CASZ1, PIEZO1, PPP3R1, EBF1, STIM2, HFE, GATA2, NFATC2, and SOX9) and proteins (MICB and CD209) can be considered as good candidates for follow-up functional studies and might be of interest as potential drug targets.

Polymorphisms of genes involved in inflammation and blood vessel development influence the risk of varicose veins

Heredity plays an important role in the etiology of varicose veins (VVs). However, the genetic basis underlying this condition remains poorly understood. Our aim was to replicate top association signals from genome-wide association studies (GWASs) for VVs of lower extremities using 2 independent datasets-our sample of ethnic Russian individuals (709 cases and 278 controls) and a large cohort of British residents from UK Biobank (10 861 cases and 397 594 controls). Associations of polymorphisms rs11121615, rs6712038, rs507666, rs966562, rs7111987, rs6062618, and rs6905288 were validated in the UK Biobank individuals at a Bonferroni-corrected significance level. In Russian cohort, only rs11121615 reached a nominal significance level of P < .05. Results of original GWAS and replication studies were combined by a meta-analysis, and polymorphisms listed above as well as rs111434909 and rs4463578 passed a genome-wide significant threshold. Notably, the majority of these polymorphisms were located within or near genes involved in vascular development and remodeling, and regulation of inflammatory response. Our results confirm the role of these polymorphisms in genetic susceptibility to VVs and indicate the revealed genomic regions as good candidates for further fine-mapping studies and functional analysis. Moreover, our findings implicate inflammation and abnormal vascular architecture in VVs pathogenesis.

An in Vitro Model for the Molecular Investigation of Varicose Veins: Use of Cultured Explants of Human Long Saphenous Vein

Objective:

To develop an in vitro model from explants of human varicose veins (VVs).

Procedures:

Segments of VVs were cultured for up to 14 days with 30% fetal calf serum. At 7 and 14 days, segments were analysed for changes in intima:media thickness and by immunohistochemistry. Comparisons were made with VVs at isolation and cultured explants of normal vein.

Results:

At isolation, VVs had a significantly thicker intima than normal veins ( p<0.001). By day 7 in culture, normal veins developed a significant (smooth muscle cell-derived) ‘neo-intima’ ( p<0.006). In contrast, in VVs there was little change in the intima but a significant increase in the thickness of the media ( p<0.001). Following 14 days in culture, both the neo-intima in normal veins and thickened media in VVs had regressed. Overall, there was a reduction in the intima:media ratio in VVs by day 14 ( p<0.03).

Conclusions:

Segments of VVs can be maintained in culture for up to 14 days without developing a neo-intima and may provide a suitable model to investigate mechanisms underlying the chronic venous insufficiency of varicosity.

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.