Mesenchymal target cell specificity of egg granuloma-derived fibroblast growth factor in schistosomiasis

We previously demonstrated that egg granulomas isolated from the liver of mice infected with Schistosoma mansoni secrete factors that stimulate fibroblast proliferation in vitro. Because this growth factor also stimulated thymocyte proliferation, we further investigated the mesenchymal target cell specificity of this factor. We now report that granulomas also secrete material that promotes growth of aortic smooth muscle and endothelial cells. We found that the activities that stimulate fibroblast and smooth muscle cell growth share similar physicochemical properties (Mr, 30-40 kilodaltons [kDa]; pI, approximately 6.5), a result suggesting that they are the same or related molecules. In contrast, fractions (Mr, less than 10 kDa; pI, 6.7-7.5) that maximally stimulated endothelial cells had minimal or no effects on the other two cell types. We postulate that soluble granuloma products might also stimulate in vivo proliferation of vascular smooth muscle and endothelial cells and contribute to the pathology of the intrahepatic vessels in schistosomiasis.