ALTERED STEADY-STATE LEVELS OF MESSENGER-RNA CODING FOR EXTRACELLULAR MATRICES IN RENAL TISSUES OF DDY MICE, AN ANIMAL-MODEL FOR IGA NEPHROPATHY

Correlations between the steady-state mRNA levels of extracellular matrices using specific cDNA probes for the alpha-1 chain of type IV collagen (alpha-1 (IV) chain); laminin A, B1, and B2 chains; and heparan sulfate proteoglycan (HSPG); and glomerular injuries in ddY mice were evaluated. Eight-, sixteen- and forty-week-old ddY mice were used in this study. ICR mice of the same age served as control. Extracted total RNA of pooled kidneys was fixed on a filter and then hybridized with the cDNA probes. Renal cryostat sections were incubated with rabbit anti-mouse type IV collagen, laminin, and HSPG antisera and then stained with FITC-labeled goat anti-rabbit IgG antiserum. The sections were also stained with FITC-labeled goat anti-mouse IgA, IgM, IgG, and C3 antisera. In light microscopy, the average number of glomerular cells was calculated at each age. Increased expression of extracellular matrices genes for the alpha-1 (IV) chain; laminin A, B1, and B2 chains; and HSPG was found in renal tissues of ddY mice. Staining of type IV collagen, laminin, and HSPG was observed in renal tissues of ddY mice at each age. Increased proteinuria in 40-week-old ddY mice might be related to the decrease in glomerular basement membrane HSPG which acts as the anionic sites in such areas. Marked proliferation and/or expansion of glomerular cells and mesangial matrices were observed in 40 week-old-ddY mice. The intensity of IgA and C3 deposits in the glomeruli was parallel to the levels of mRNA for such components. It appears that increased mRNA levels for such matrices coincided with the development of renal injuries in ddY mice. It is concluded that evaluation of steady-state mRNA levels of the extracellular matrices in renal tissues of ddY mice is useful in determining progressive mechanisms in patients with IgA nephropathy.