COLLAGEN SYNTHESIS IN INFLAMMATION

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Degenerative and inflammatory joint diseases are characterized by disturbances in the remodeling of the extracellular matrix of joint tissues, including cartilage, bone, and synovium. Collagen is a major constituent of these connective tissues, and the overall goal of this proposal is to define the cellular and molecular mechanisms underlying the altered collagen synthesis that accompanies the defective repair processes in arthritis. In this proposal we will continue studies that have focused on cytokines that regulate the tissue-specific patterns of expression of collagen types by connective tissue cells. We have established human cell culture models of normal and/or immortalized human synovial and dermal fibroblasts, articular and costal chondrocytes, and osteoblast-like cells. These studies focus on the expression of the type I collagen gene. We have begun to characterize the expression of type I collagen by these cells in response to interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma), cytokines implicated in the pathological connective tissue remodeling associated with inflammatory disorders, and to define the feedback modulatory role of prostaglandin (PGE2). Binding of these cytokines and prostaglandins to specific cell-surface receptors induces responses in each type that are probably mediated by distinct signaling events and induction or modulation cell-specific transcription factors. The Specific Aims are: (1) Further characterize and develop immortalized human cell lines as models for studying cell-specific responses to cytokines. (2) Determine the molecular mechanisms underlying the differential responses of human connective tissue cells of IL-1, TNF- alpha, IFN-gamma, and PGE2. (3) Determine whether known transcription factor are involved in regulating collagen gene expression in response to IL-1, TNF-alpha, IFN-gamma and PGE2 and define interactions among cytokine-responsive and tissue-specific regulators. (4) Identify unique gene(s) that determine cell-specific cytokine responses in these models by differential cloning techniques and identify and characterize the novel gene product(s). The proposed studies will provide new information about how cytokines and prostaglandins prevent appropriate repair of joint tissues in rheumatic diseases. This approach could permit targeting of specific signaling pathways and associated transcription factors with pharmacological agents in order to dissociate the beneficial effects of cytokines and prostaglandins from their detrimental effects on joint inflammation and degradation.