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Cultured rat mesangial cells have features of immune effector cells that may contribute to the derangements in glomerulonephritis. Recent reports have demonstrated that mesangial cells produce a cytokine similar to interleukin 1 (IL 1). We predicted rat mesangial cells could express a gene homologous to murine macrophage IL 1. Mesangial cells were cultured by explant and were used in the fourth through sixth passages. Antibodies to desmin and fibronectin but not cytokeratin stained the cytoskeleton of all mesangial cells examined; no Ia+, leukocyte common antigen+ mononuclear phagocytes were present. RNA from mesangial cells and P388D macrophages hybridized in dot blots with a 32P-probe nick-translated from the murine IL 1 cDNA. Mesangial cells but not Swiss 3T3 fibroblasts contained IL 1 mRNA transcripts that co-migrated with the 2.0 kb message from murine P388D macrophages by Northern analysis of poly(A) RNA. In situ hybridization of cultured cells demonstrated specific hybridization of 3H-IL 1 probe to cells with the morphology of contractile mesangial cells and P388D cells but not 3T3 cells. IL 1 release is an important mediator of local inflammation and injury. Therefore we compared the expression of the IL 1 gene in total RNA from kidneys of rats with immune complex glomerulonephritis with that extracted from kidneys of healthy rats. Glomerulonephritic kidneys contain a twofold to threefold increase in IL 1 mRNA compared with normals. We conclude that rat mesangial cells express mRNA with significant homology to murine macrophage IL 1 mRNA and further suggest that local production of the potent phlogistic mediator IL 1 may be important in the pathogenesis of glomerulonephritis.
Werber et al. (Fri,) studied this question.