A novel system for investigating the ability of smooth muscle cells and fibroblasts to regulate adhesion of flowing leukocytes to endothelial cells

Stromal cells may contribute to the inflammatory processes which lead to th e recruitment of circulating leukocytes. Here, we describe a multicellular model in which chosen cellular elements of tissue can be cocultured with en dothelial cells (EC). Cocultures can be incorporated into a novel parallel plate flow chamber to determine if stromal cells influence the patterns of leukocyte adhesion to the EC. As an example relevant to the pathology of at herosclerosis, EC were cultured with arterial smooth muscle cells (SMC) of the 'secretory' phenotype. EC and secretory SMC were cultured on the opposi te faces of commercially available porous polyethylene terepthalate (PET) c ulture inserts, which fitted into a parallel plate flow chamber. Binding of flowing purified lymphocytes, labelled with the fluorochrome calcein-AM, t o cocultured EC was assessed by fluorescence microscopy. Lymphocyte adhesio n was negligible on unstimulated EC cultured alone or cocultured with SMC. However, when tumour necrosis factor-a (TNF) was added to cocultures, the E C supported greatly increased levels of lymphocyte adhesion compared to TNF -treated EC cultured alone. Additionally, cocultured EC responded to TNF at concentrations far below those at which EC cultured alone responded. This priming was specific in that skin fibroblasts cocultured with EC did not mo dify lymphocyte adhesion induced by TNF. Thus, we have developed a cocultur e model to determine the ability of tissue stromal cells to modify leukocyt e recruitment. This may have wide applications in the study of the cellular pathology of inflammation by allowing the contribution of the local microe nvironment to be assessed. (C) 2001 Elsevier Science B.V. All rights reserv ed.