Inter-regulated balance between gelatinases and tissue inhibitor (TIMP-1) in isolated human glomeruli

Leukocyte infiltration inside glomeruli necessitates basement membrane collagen i.v. breakdown and leads to mesangiolysis, cell proliferation and extracellular matrix synthesis during the repair process as observed in the course of acute glomerulonephritis, vasculitis and acute graft rejection. Two matrix metalloproteinases, MMP-2 and MMP-9 gelatinases, 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 i.v. deposition. Using a conventional double mesh sieving method, pure populations of glomeruli were isolated from fresh human cortex specimen and maintained in short-term cultures. ELISA, zymography and immunoblotting of conditioned serum-free media revealed glomerular MMP-2, MMP-9 and TIMP-1 secretion and activity while reverse transcription-polymerase chain reaction amplification of cellular RNA demonstrated glomerular transcripts coding for these enzymes and their inhibitor. When purified neutrophils were allowed to adhere onto Transwell apparatus in contact with glomerular suspensions, neutrophil 92 kDa gelatinase seemed apparently inhibited mainly because the production of TIMP-1 was enhanced on both sides of the insert. Glomerular 72 kDa and 92 kDa gelatinases were activated shortly (1 to 6 h) after neutrophils had interacted with glomeruli and furthermore upon activation by inflammatory or vasoactive mediators such as phorbol. Decreased neutrophil MMP-9 activity together with reduced MMP-9 mRNA levels and protracted TIMP-1 transcription and secretion during cell-cell interaction could participate to cell detachment from degraded basement membranes and to increased collagen i.v. deposition leading to glomerulosclerosis after initial glomerular injury by inflammatory cells.