Effect of calcineurin inhibitors on extracellular matrix turnover in isolated human glomeruli

Although chronic cyclosporine toxicity is mainly characterized by tubular atrophy and interstitial fibrosis, glomerular injury with expansion of mesangial matrix and sclerosis is not uncommon. Tacrolimus is a newer calcineurin inhibitor that has been used in renal transplant recipients as primary or rescue therapy. Clinical trials suggest an improved long-term graft survival among patients treated with tacrolimus. Recently we have shown that tacrolimus and cyclosporine have similar effects on extracellular matrix turnover in cultured cells. The present study was performed to investigate the effects of the calcineurin inhibitors on whole glomeruli extracellular matrix turnover.

Human glomeruli isolated from kidney biopsies just before transplantation were incubated with culture media containing either cyclosporine (200 ng/mL) or tacrolimus (10 ng/mL) for 24 hours. Glomeruli incubated only with culture medium were used as control.

The expressions of (alpha2)IV collagen, metalloprotease 9 (MMP9), tissue inhibitors of metalloproteases 2 (TIMP-2), and TGFbeta were evaluated by in situ reverse transcription and polymerase chain reactions (RT-PCR). beta-actin was used as a control gene. Cyclosporine (but not tacrolimus) increased the expression of (alpha2)IV collagen and TIMP2 in isolated glomeruli. TGF-beta was markedly increased by cyclosporine. MMP9 expression was not affected by the calcineurin inhibitors. By light microscopy kidney biopsies did not show pathologic changes.

Cyclosporine treatment modulates extracellular matrix turnover in isolated human glomeruli, inducing an imbalance between synthesis and degradation. This effect, not observed in tacrolimus-treated human glomeruli, may induce the extracellular matrix deposition and sclerosis characteristic of chronic cyclosporine toxicity.