In situ hybridization in the study of remodeling in proliferative glomerulonephritis

In situ hybridization combined with immunohistochemistry provides a powerful tool to study the temporal and spatial relationships between cellular sources of mRNA and localization of translated protein in normal biologic and pathologic processes. In this symposium, techniques in probe selection for the detection of mRNA in normal kidney and renal disease were discussed. Examples of the application of in situ hybridization in the study of renal disease were demonstrated using a model of proliferative glomerulonephritis induced by habu snake venom. This model follows an accelerated course of remodeling involving mesangial cell migration, proliferation, and extracellular matrix synthesis. The cellular sources and temporal expression of 2 adhesive proteins, fibronectin and thrombospondin, known to have a role in cell remodeling during embryogenesis and wound healing, were examined and compared to mesangial cell behaviors during the course of habu venom-induced glomerulonephritis. Mesangial cell migration in early lesions was associated with thrombospondin and fibronectin derived from platelets or macrophages. Thrombospondin mRNA and protein peaked at 48 hr after habu venom and were associated with mesangial cell proliferation; but thrombospondin mRNA and protein declined at 72 hr when expression of collagen type IV and laminin mRNA and protein peaked. Mesangial cell expression of fibronectin first appeared at 48 hr, and peaked at 72 hr after habu venom. Thus, mesangial cell migration was associated with exogenous fibronectin and thrombospondin derived from platelets or macrophages. Mesangial cell expression of thrombospondin was associated with migration and proliferation, whereas, expression of fibronectin was associated with proliferation and matrix synthesis. These results suggest distinctive temporal and spatial roles for thrombospondin and fibronectin in remodeling during glomerulonephritis and illustrate the utility of in situ hybridization and immunohistochemistry in the detection of cellular sources of translated proteins.