Immunolabeling of Type IV Collagen, Laminin, and α-Smooth Muscle Actin Cells in the Intima of Normal and Varicose Saphenous Veins

Abstract

Smooth muscle cells (SMC) of normal and varicose human saphenous intima were studied on cryostat sections by immunohistochemistry with alpha-smooth muscle actin (ASMA), type IV collagen, and laminin antibodies and also by transmission electron microscopy. The findings suggest two structurally distinct subtypes of smooth muscle cells with thin and thicker external lamina. Thin external lamina SMC were characterized by laminin, type IV collagen, weaker external lamina reactivity, and intense cytoplasmic alpha-smooth muscle actin immunoreactivity. Ultrastructurally, they exhibited abundant cytoplasmic microfilaments and thin external lamina. These cells were found isolated or, more frequently, clustered in fascicles close to the subendothelium in focal or zonal cushions, or in diffuse enlargement of the intima. In contrast, thicker external lamina smooth muscle cells were intensely immunolabeled for laminin and collagen IV, showing irregular cytoplasmic ASMA reaction. Single or clustered thicker external lamina SMC were seen predominantly in zonal cushions and in intima diffuse enlargement. It is very likely that these cells secrete these matrices in a nonpolarized fashion. The thicker external lamina of these SMCs showed a fine granular amorphous aspect sometimes intermingled with microfibrils. These external lamina were interposed between neighboring cells and exposed to collagen fibrils and elastic fibers. The cells also exhibited rarefaction of the cytoplasmic filaments. Intermediary cells exhibiting both features were rarely seen. Thicker external lamina SMC should be discussed in the context of an adaptive/proliferative response leading to dysfunction of the fibroelastic properties of the vein wall.

A Journey across the Wall of Varicose Veins: What Physicians Do Not Often See with the Naked Eye

“…These fi ndings are in agreement with previous observations [3,37,41] but do not concur with the results obtained by Mashiah et al [42] , who did not observe any changes in the tunica intima of saphenous VVs using scanning electron microscopy. Whether the subendothelial and medial SMCs of VVs share the same trigger leading to the disruption of their normal function is still under investigation by our group.…”

Smooth muscle cell modulation and cytokine overproduction in varicose veins. Anin situ study

“…We observed ECM accumulation in the media contributing to the disorganization of the vein wall5, 6, 8. These alterations of SMCs, connective tissue metabolisms and basement membrane suggest the modulation of SMCs from a contractile to a synthetic phenotype11–15 and may explain the altered functional properties reported in VVs5, 16. However, few SMCs were stained for PCNA and Ki67, suggesting a low proliferative rate during varicose remodelling.…”

“…Jurukova and Milenkov have shown that these cells are structurally and functionally altered16 and Porto et al . have demonstrated the presence of two structurally distinct subtypes of SMCs15. These SMCs were intermingled with various ECM components, suggesting that they had been proliferative and synthetic and have since regained a differentiated phenotype.…”

Associations of NF-kappaB and Bax with Apoptosis in Varicose Veins of Women of Different Age Groups

“…One of the pathogenetic mechanisms of dysregulated SMC apoptosis in the varicose vein wall may be connected with SMCs dedifferentiation from a contractile phenotype to a secretory one. Several investigations [27–29] have found that fibrotic degeneration with the disruption of the elastic network seen in varicose veins may be related to the accumulation of secretory SMCs. Increased ECs apoptosis seen in older age groups of our investigation may result in a partial loss of endothelial lining that we have also described in our previous studies [5].…”