Thrombospondin-2 therapy ameliorates experimental glomerulonephritis via inhibition of cell proliferation, inflammation, and TGF-beta activation.

We recently identified thrombospondin-2 (TSP-2) as an endogenous regulator of matrix remodelling and inflammation in experimental kidney disease by studying TSP-2-deficient mice. In this study, we asked whether systemic TSP-2 overexpression via thigh muscle transfection is able to ameliorate the time course of the anti-Thy1 glomerulonephritis model. After induction of anti-Thy1 nephritis, rats were transfected either with an overexpression plasmid for TSP-2 or lacZ as a control. Biopsies, urine, and blood samples were taken on days 1, 3, and 6 after disease induction. Muscular overexpression of TSP-2 reduced glomerular transforming growth factor (TGF)-beta activation and glomerular extracellular matrix formation as determined by collagen IV and fibronectin. In addition, activation of mesangial cells to the myofibroblast-like phenotype was also significantly decreased in TSP-2-overexpressing animals. TSP-2 overexpression inhibited both glomerular endothelial and mesangial cell proliferation, resulting in a reduced glomerular cell number and glomerular tuft area. The inflammatory response, as monitored by T cells and antigen-presenting cells, was reduced significantly by TSP-2 overexpression, but influx of macrophages was unchanged. These data demonstrate TSP-2 as a potential therapeutic agent to inhibit the glomerular proliferative and inflammatory response as well as TGF-beta activation and extracellular matrix accumulation in experimental mesangial proliferative glomerulonephritis.