Analysis of collagen and elastin content in primary varicose veins

Abstract

We read with interest the article by Gandhi et al. 1Gandhi RH Irizarry E Nackman GB Halpern VJ Mulcare RJ Tilson MD Analysis of the connective tissue matrix and proteolytic activity of primary varicose veins.J VASC SURG. 1993; 18: 814-820Abstract Full Text Full Text PDF PubMed Scopus (141) Google Scholar regarding the evaluation of the connective tissue constituents of greater saphenous varicosities, and we want to report our experience. Both elastin and collagen are known to play an important role in maintaining the structural integrity of blood vessel walls. When the wall is stretched, elastin generates a shortening force that opposes the traction exerted by the side branches and perivascular connective tissue and the lengthening force caused by pressure in the lumen. Type I collagen is believed to confer tensile strength on the vessel wall, whereas type III may be involved in its extensibility. The amount of collagen and elastin was studied biochemically and histologically in two homogeneous groups of human saphenous veins. Twenty primary varicose veins were obtained from patients during surgical procedures (stripping, segmental resections), and 20 normal veins were obtained from patients scheduled for coronary artery bypass (control group). For each varicose vein two portions were examined: one segment that appeared to be macroscopically healthy and one dilated segment. Elastin and collagen content was determined in approximately 100 mg of tissue as described by Todorovich-Hunter et al., 2Todorovich-Hunter L Johnson DJ Ranger P et al.Altered elastin and collagen synthesis associated with progressive pulmonary hypertension induced by monocrotaline.Lab Invest. 1988; 58: 184-185PubMed Google Scholar treating the tissue with cyanogen bromide. The relative proportion of type I and III collagen was determined in approximately 100 mg of tissue after cyanogen bromide cleavage as described by Laurent et al. 3Laurent GJ Cockerill P McAnulty RJ et al.A simplified method for quantitation of the relative amounts of type I and type III collagen in small tissue samples.Anal Biochem. 1981; 113: 301-312Crossref PubMed Scopus (112) Google Scholar Regarding the histologic assay, paraffin blocks of formalin-fixed veins were sectioned at a thickness of 5 μm to obtain a cross section of the vein wall. These sections were stained with the Picrosirius red technique for collagen 4Montes GS Junqueira LCU Histochemical localization of collagen and proteoglycans in tissue. In: Nimni ME, ed.Collagen Boca Raton: CRC Press. 1988; 2: 41-72Google Scholar and Hart's technique for elastin 5Luna LG. Manual of histologic staining methods of the armed forces institute of pathology.in: 3rd ed. McGraw-Hill, New York1968: 79-80Google Scholar and examined with a polarizing microscope, determining also the fibers and type of collagen. Collagen content, assessed by biochemical method, was significantly increased in both dilated and morphologically normal segments of varicose veins as compared with normal veins; type I collagen was always present in greater amount than type III. Varicose veins contained more type I and type III collagen than normal veins. The elastin content was significantly reduced in the dilated segments of varicose veins when compared with both normal veins and normal segments of varicose veins; no significant difference in elastin content was noted between the morphologically normal segments of varicose veins and normal veins. At microscopic evaluation, the ratio of collagen to elastin appeared to be significantly increased in the dilated segments of varicose veins. Elastic fibers were markedly decreased, and individual elastic fibers were more thickened and tortuous. In the morphologically normal segments of varicose veins, the ratio of collagen to elastic fibers appeared to be moderately increased. The results of our study show that the wall of varicose veins has a higher collagen content compared with normal veins, whereas the elastin content is reduced only in the dilated segments of varicose veins. These findings tend to emphasize the important role of elastin in providing retractile force that opposes the development of dilation and tortuosity of the vein wall.