Genetic predisposition for glomerulonephritis-induced glomerulosclerosis in rats is linked to chromosome 1.

Genetic factors influence renal disease progression, and several loci have been linked to the spontaneous development of proteinuria and glomerulosclerosis in animal models. However, the role of genetic susceptibility in glomerulonephritis-induced progressive glomerulosclerosis is unknown. In a rat model of mesangial proliferative glomerulonephritis, anti-Thy-1 glomerulonephritis (antiThy1GN), Lewis/Maastricht (Lew/Maa) rats exhibit progression to glomerulosclerosis, whereas in genetically related Lewis/Møllegard (Lew/Moll) rats, glomerular lesions are repaired within 3 wk. The genetic factors underlying this strain-related difference are not known. To identify novel quantitative trait loci (QTL) involved in progression or repair in Lewis rats, 145 female backcross rats [F1(Lew/Maa x Lew/Moll) x Lew/Maa] were studied. After induction of antiThy1GN proteinuria, we determined mesangial activation, the percentage of microaneurysms, and the glomerular damage score for each animal; a genome scan using 187 microsatellite markers was performed. QTL mapping revealed a significant QTL for glomerular damage score on chromosome 1 with a logarithm of odds (LOD) score of 3.9. Homozygosity for Lew/Maa DNA in this region was associated with a higher percentage of damaged glomeruli on day 21. Furthermore, suggestive linkage was found for the percentage of glomeruli with microaneurysms on day 3 on chromosome 1, 6, and 11; for mesangial activation on day 7 on chromosome 18, while proteinuria was suggestively linked to chromosome 5 (day 0), 4 (day 3), and 6 (day 7). This study identifies a QTL on rat chromosome 1 that is significantly linked to progressive glomerulosclerosis after acute glomerulonephritis.

Genes expressed by the kidney, but not by bone marrow-derived cells, underlie the genetic predisposition to progressive glomerulosclerosis after mesangial injury.

Progressive renal failure is accompanied by uncontrolled accumulation of extracellular matrix in glomeruli and tubulointerstitium, eventually resulting in glomerulosclerosis. Although glomerulosclerosis occurs secondary to various renal diseases, the fact that not all patients develop progressive glomerulosclerosis suggests that genetic factors may underlie the tendency to progress, or not to progress. Identified were two Lewis rat substrains with small genetic differences but with considerable difference in resolution of glomerulonephritis after anti-Thy-1 administration. In the Lewis/Møllegard rat strain, anti-Thy-1 glomerulonephritis spontaneously resolves within 4 wk. In contrast, Lewis/Maastricht rats develop progressive glomerulosclerosis after induction of this disease. The involvement of bone marrow-derived cells and kidney cells in the development of glomerulosclerosis was determined. In the first study, exchange of bone marrow between these substrains did not affect the course of anti-Thy-1 nephritis. Lewis/Møllegard rats recovered rapidly, but Lewis/Maastricht rats showed progressive disease regardless of the genotype of the bone marrow they received. In the second study, kidneys were exchanged between the substrains. After transplantation, anti-Thy-1 nephritis was induced and glomerular damage assessed at day 21. Severe damage was observed in Lewis/Maastricht glomeruli independent of whether the kidney had been transplanted or not. Similarly, Lewis/Møllegard glomeruli, whether transplanted or not, revealed no residual histopathologic abnormalities. The inherited differences between the two substrains with regard to their insusceptibility to develop progressive glomerulosclerosis after mesangial injury are governed by genes expressed by the kidney, but not by bone marrow-derived cells.