Ultraviolet light-irradiated collagen III modulates expression of cytoskeletal and surface adhesion molecules in rat aortic smooth muscle cells in vitro

Systemic and pulmonary hypertension is characterised by structural reconstruction of the vascular wall which includes hypertrophy and hyperplasia of vascular smooth muscle cells (VSMCs) and fibroproduction. We hypothesise that these changes are stimulated by nonenzymatic modification of collagen molecules in the injured vascular wall by radicals. We exposed collagen III to ultraviolet (UV) light irradiation which, as indicated by fluorescence and electrophoretic analyses, resulted in its fragmentation. Both irradiated and control unmodified collagen were adsorbed on culture dishes and seeded with VSMCs derived from the rat thoracic aorta. During the first week after seeding, the cells on the modified collagen attained significantly higher population density (by 15-83%), higher mitotic index (by 31-135%) and higher BrdU labelling index (by 32%). However, these cells were less resistant to spontaneous and trypsin-mediated detachment from the growth support. As revealed using enzyme-linked immunosorbent assay in 3-day-old cultures, the cells growing on the irradiated collagen exhibited a lower concentration of beta-1 integrins (-10%, measured per milligram of protein), vinculin (-18%), talin (-6%) and vimentin (-15%). Immunofluorescence staining showed that these molecules were distributed more diffusely and less organised into focal adhesion plaques or cytoskeletal fibres. The concentration of two adhesion molecules of immunoglobulin type, ICAM-1 and VCAM-1, was increased by 11% and 16%, respectively. The concentration of alpha-v integrins and alpha-actin was unchanged, the latter, however, formed fewer distinct microfilament bundles in cells on the modified collagen. Our results suggest that the VSMCs growing on UV-modified collagen are more prone to escape the growth control mediated by cell-extracellular matrix contact and can bind the cells of the immune system.