Effects of interleukin‐1 on fibroblast extracellular matrix, using a 3‐dimensional culture system

Abstract

This study describes the alterations induced by Interleukin‐1α and ‐β (IL‐1α and IL‐1β) on fibroblast‐synthesized extracellular matrix. Fibroblasts were grown between pieces of dentin or in collagen‐coated Terasaki wells for 3 or 6–9 weeks to create 3‐dimensional cell‐containing matrices constituted primarily of proteoglycans and collagens, respectively. Following incubation with IL‐1α or IL‐1β (10⁻⁹ M) at 37°C for 24 or 72 hr, samples were prepared for light and electron microscopy. Both IL‐1α and IL‐1β induced collapse of the extracellular matrix by 72 hr, as manifested by a decrease of the cross‐sectional area and an increased density of the matrices. Three‐week matrices were reduced 26% and 45% by using IL‐1α and IL‐1β, respectively. Comparable values obtained by using 6‐week matrices were 14% and 30%. Cells within the matrix, normally stellate in shape with numerous extended processes, attained a more rounded or spindle shape with few and reduced processes and showed apparent alterations at cell matrix attachment sites and rearrangement of the cytoskeleton. Elongated cells at the top of the matrix appeared more compressed. The alterations were more pronounced in cultures incubated with IL‐β than with IL‐1α. Immunocytochemistry of extracellular matrix components revealed a decrease in staining intensity of chondroitin and dermatan sulfate in the 3‐week matrix following IL‐1β incubation. There was also a decrease in collagen type I staining of 9‐week matrices treated with IL‐1α or IL‐1β. These studies show that IL‐1 has an effect on fibroblast‐synthesized extracellular matrix and indicate that the effects of IL‐1α and IL‐1β may differ. The resulting collapse of the matrix appears at least in part to be due to changes in proteoglycans and collagens.