ADHESION OF BLOOD PLATELETS TO THE EXTRACELLULAR MATRIX OF CULTURED CELLS IN WHICH COLLAGEN SYNTHESIS IS IMPAIRED OR INDUCED

One of the first phenomena in the hemostatic plug formation is adhesion of platelets to the subendothelium or to the perivascular connective tissue. With a rectangular perfusion chamber (Sakariassen et al., J.Lab.Clin.Med.(1983) 102, 522-535) it is possible to study platelet adhesion in flowing blood to extracellular matrix (ECM) of cultured cells. Collegen type I and III play an important role in the adhesion of platelets. To study their role in more detail, cultured cells with changed collagen synthesis were used. For this purpose, we used fibroblasts of a patient with Osteogenesis Imperfecta type I (0.I.)(characterized by impaired collagen synthesis) cultured from a skin biopsy and used in the fourth passage. Platelet adhesion to ECM of 0.1. fibroblasts was decreased in comparison to ECM of normal fibroblasts (8% versus 17% at low shear rates (300 s™1 ) and 5% versus 24% at high shear rates (1300 s™1 ) after perfusion with whole blood for 5 min). No aggregate formation occurred on patient’s matrices, whereas small aggregates were observed on ECM of normal fibroblasts. Addition of ascorbic acid to culture medium of fibroblasts, smooth muscle cells and endothelial cells causes increased collagen synthesis with increased fibril formation. Platelet adhesion to ECM of endothelial cells showed an increased adhesion of 25% only at high wall shear rates (1300 s™1 ). Induction of collagen synthesis in smooth muscle cells resulted in a strong increase of thrombus formation on their matrices. These data indicate that platelet adhesion to the matrix of cultured cells is strongly dependent on the quantity and nature of the reactive collagens.