REVERSE GENETIC ANALYSIS IN TISSUE INJURY

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Tissue responds to damage with an early reflux of polymorphonuclear cells and subsequent influx of monocytes/macrophages into the wound area. Mitogenic factors derived from macrophages have not only been recognized as essential to normal wound-healing, but have also been implicated in the fibrosis that can occur with chronic inflammation. Transforming growth factor-beta (TGFbeta), a mitogenic factor that plays a strong role in tissue regulation, has been shown to be secreted by platelets and activated macrophages. Although TGFbeta is thought to play its strong regulatory role primarily through effects on other growth factors and the extracellular matrix (resulting in its overall increase), the in vivo role of TGFbeta is poorly understood. The goal of this project is to study the effects of TGFbeta in vivo by preparing a mutant TGFbeta that is not only inactive, but also will inactivate wild-type TGFbeta when it forms a heterodimer with the mutant. This takes advantage of the fact that TGFbeta is translated as a prepro-form and is processed to an active protein. The dominant TGFbeta mutant gene will be linked to a promoter that is only active in activated macrophages (visna virus long terminal repeat), and this construct will be used to develop a transgenic model. It is the eventual goal of the principal investigator to examine the role of macrophage-derived TGFbeta in chronic inflammation, primarily in the lung. With this transgenic model, various experimental methods could be used to produce lung damage, providing information not only on the role of macrophage-derived TGFbeta in chronic inflammation but also on its role in normal wound-healing.