ASSESSMENT OF 72-KILODALTON GELATINASE AND TIMP-1 GENE-EXPRESSION IN NORMAL AND SCLEROTIC MURINE GLOMERULI

Mice transgenic for bovine growth hormone (bGH) develop progressive di ffuse glomerulosclerosis. Because murine mesangial cells in vitro were found to express the genes for 72-kd gelatinase and the metalloprotei nase inhibitor TIMP-1, the expression of these genes in vivo in isolat ed whole glomeruli from bGH mice and normal control littermates was ex amined. Intact glomeruli were isolated by microdissec tion and subject ed to reverse transcription. TIMP-1 cDNA was not detected by standard polymerase chain reaction (PCR) in glomeruli from bGH or control mice. In contrast, cDNA for 72-kd gelatinase was detected by standard PCR i n both bGH and control mice, and the level was subsequently measured b y quantitative competitive PCR. The gelatinase cDNA lever was 14.7 +/- 2.8 x 10(-4) attomoles/glomerulus in 2-to 3-month-old control mice an d was unchanged in 6-month-old controls. The bGH mice had 3.5-fold and 4.5-fold higher cDNA levels at 2 to 3 months and 6 months of age, res pectively. Finally, zymography of glomerular extracts revealed increas ed levels of 72-kd and 96 to 100-kd gelatinase activity in bGH glomeru li in comparison to that in controls. In summary, whereas the genes fo r both TIMP-1 and 72-kd gelatinase are expressed in vitro in cultured mesangial cells, only the gelatinase gene appeared to be expressed in vivo in intact glomeruli. In addition, there was an up-regulation in t he glomerular expression of the 72-kd gelatinase in bGH mice, a murine model of glomerulosclerosis.