Objective: To examine the role of an interaction between fibroblasts and mononuclear infiltrates through CD40-CD154 engagement in the development of tissue fibrosis.
Methods: Cultured dermal fibroblasts derived from healthy skin were induced to express CD40 by adenoviral gene transfer, stimulated with soluble CD154, and evaluated for proliferation, gene expression, and protein expression in vitro. The skin of mice with bleomycin-induced skin sclerosis, a model for systemic sclerosis (SSc), was assessed for CD40 and CD154 expression, in vivo fibroblast proliferation, and the expression of specific genes. The effects of an anti-CD154 monoclonal antibody on bleomycin-induced skin sclerosis were also examined.
Results: Upon stimulation with soluble CD154, cultured fibroblasts induced to express CD40 by adenoviral gene transfer proliferated and showed up-regulation of the genes for intercellular adhesion molecule 1, interleukin-6 (IL-6), IL-8, monocyte chemoattractant protein 1 (MCP-1), and RANTES, as well as up-regulation of their proteins. In the skin from bleomycin-treated mice, dermal fibroblasts expressed CD40, and mast cells and CD4+ T cells expressed CD154. Electron microscopic analysis revealed fibroblasts attached to mast cells and T cells with primitive contacts. The proliferation of fibroblasts and the up-regulated MCP-1 gene expression preceded thickening of the dermis. Finally, the anti-CD154 antibody inhibited the bleomycin-induced skin sclerosis by suppressing fibroblast proliferation and down-regulating MCP-1 expression.
Conclusion: The interaction between fibroblasts and mast cells or T cells through CD40-CD154 signaling is critical for fibroblast activation early in the course of fibrosis. Blockade of the CD40-CD154 signal may be a novel therapeutic strategy for human fibrotic diseases, such as SSc.