INTER-REGULATED BALANCE BETWEEN GELATINASES AND TISSUE INHIBITOR (TIMP-1) IN ISOLATED HUMAN GLOMERULI

Leukocyte infiltration inside glomeruli necessitates basement membrane collagen IV breakdown and leads to mesangiolysis, cell proliferation and extracellular matrix synthesis during the repair process as observ ed in the course of acute glomerulonephritis, vasculitis and acute gra ft rejection. Two matrix metalloproteinases, MMP-2 and MMP-9 gelatinas es, are expressed and co-secreted in balance with the tissue inhibitor of metalloproteinases-1 (TIMP-1) by activated neutrophils as well as by glomerular cells and are aimed to control basement membrane collage n IV deposition. Using a conventional double mesh sieving method, pure populations of glomeruli were isolated from fresh human cortex specim en and maintained in short-term cultures. ELISA, zymography and immuno blotting of conditioned serum-free media revealed glomerular MMP-2, MM P-9 and TIMP-1 secretion and activity while reverse transcription-poly merase chain reaction amplification of cellular RNA demonstrated glome rular transcripts coding for these enzymes and their inhibitor. When p urified neutrophils were allowed to adhere onto Transwell apparatus in contact with glomerular suspensions, neutrophil 92 kDa gelatinase see med apparently inhibited mainly because the production of TIMP-1 was e nhanced on both sides of the insert. Glomerular 72 kDa and 92 kDa gela tinases were activated shortly (1 to 6 h) after neutrophils had intera cted with glomeruli and furthermore upon activation by inflammatory or vasoactive mediators such as phorbol. Decreased neutrophil MMP-9 acti vity together with reduced MMP-9 mRNA levels and protracted TIMP-1 tra nscription and secretion during cell-cell interaction could participat e to cell detachment from degraded basement membranes and to increased collagen IV deposition leading to glomerulosclerosis after initial gl omerular injury by inflammatory cells.