Loss of lymphatic vessels and regional lipid accumulation is associated with great saphenous vein incompetence

ObjectiveRecent studies suggest that biologic changes in the vein wall associated with varicose veins (VVs) occur not only in valvular tissue but also in nonvalvular regions. We previously used imaging mass spectrometry (IMS) to determine the distribution of lipid molecules in incompetent valve tissue. In this study, we used IMS to analyze incompetent great saphenous veins (GSVs) in patients with varicose vein (VV) to assess the distribution of lipid molecules.MethodsWe obtained GSV tissue from 38 VV patients (50 limbs) who underwent GSV stripping. For the control veins (CV), we obtained GSV samples from 10 patients undergoing infrainguinal bypass with reversed GSV grafting for peripheral artery occlusive disease (10 limbs). Conventional and immunofluorescence staining were performed for histopathologic examination. The total lipid content in the homogenized vein tissue was determined. The localization of each lipid molecule in the vein wall was assessed by IMS.ResultsThe histologic examination showed the VV walls were significantly thicker than the CV walls, and only the VV adventitia was positive for lipid staining. The VV wall had higher concentrations of phospholipids and triglycerides than the CV wall. IMS revealed an abnormal accumulation of lysophosphatidylcholine (LPC; 1-acyl 16:0) and phosphatidylcholine (diacyl 16:0/20:4) in the VV intima and media. Triglyceride was found only in VV adventitia. The number of lymphatic vessels, as measured by staining with D2-40, a lymphatic vessel-specific marker, was significantly lower in the VV adventitia than in the CV adventitia. Lymphatic vessel reduction may be associated with insufficient lymphatic drainage in the VV adventitia causing histologic changes in VV tissue.ConclusionsThe accumulation of LPC (1-acyl 16:0) and PC (diacyl 16:0/20:4) in the VV intima and media may be associated with chronic inflammation, leading to VV tissue degeneration. Furthermore, insufficient lipid drainage by lymphatic vessel may be responsible for accumulation of lipid molecules and subsequent vein wall degeneration.Clinical RelevanceAbnormal distribution of lipid molecules in varicose vein (VV) tissue in patients at CEAP class C2-3 and C4-5 suggests that VV-associated accumulation of lipid molecules begins in the early clinical stages of the disease and continues through the advanced stages. In particular, the accumulation of both lysophosphatidylcholine (1-acyl 16:0) and phosphatidylcholine (diacyl 16:0/20:4) in the media was significantly higher in VV tissue from patients in advanced clinical stages, suggesting an association between lipid accumulation and chronic inflammation of skin and subcutaneous tissues. Further study is needed to clarify the effect of lymph stasis on VVs and chronic inflammation. The mechanism whereby adventitial lymphatic vessels are damaged is also unknown. Consistent venous hypertension and subsequent overload to the lymphatics may account for the lymphatic damage. In addition, accumulation of possible proinflammatory lipid molecules in VV walls may further damage the adventitial lymphatic vessels