Fibroblast growth and synthetic activities during degradation and regeneration of connective tissues are regulated by various polypeptide hormones found in the surrounding fluids. Among these are platelet-derived growth factor, fibroblast growth factor, and the interleukins. Interleukin-1 (IL-1), a central mediator of inflammation, has been shown to influence both extracellular matrix turnover and mitogenesis. The goal of this project is to elucidate the role of IL-1 in connective tissue remodeling and wound healing. Since cell reaction are greatly influenced by the surrounding extracellular matrix, we propose to use primarily a 3-dimensional matrix synthesized in vitro and inhabited by fibroblasts. This system simulates closely tissue regeneration and healing in vivo, yet it is sufficiently simple to permit detailed analyses and interpretation of the results. The cells deposit a matrix consisting of proteoglycans, glycoproteins such as fibronectin, and collagens found in tissue, and manifest morphologic features comparable to cells in vivo. Our pilot studies demonstrate that exposure to IL-1 results in collapse of the matrix, with alterations in its organization and composition, in cell morphology, and in cell-matrix interactions. We propose to treat cultures with IL-1 beta, and determine the effect on the molecular composition and organization of proteoglycans and collagens in the extracellular matrix. In addition, we will analyze morphologic alterations of resident cells, including effects on intracellular filaments, as well as changes in molecular organization of cell-matrix attachment sites. The studies will include light and electron microscopy, immunocytochemistry, radiochemical labeling, and biochemical analyses. We will also investigate the mechanism by which these changes occur, by attempting to block the effect with specific enzyme inhibitors. Subsequently, we will determine fibroblast mitogenesis induced by IL-1 beta in monolayers and within 3-dimensional matrices, and determine the interrelationship of matrix and cell alterations with cell proliferation. These studies will help clarify the relationship between the immune system and connective tissue degradation and regeneration.
