Effects of Mycophenolic Acid and Rapamycin on PDGF-induced Mesangial Cell Proliferation and Extracellular Matrix Production

Purpose: Excess proliferation and extracellular matrix (ECM) accumulation of mesenchymal cells such as vascular smooth muscle cells (VSMC) and glomerular mesangial cells cause chronic allograft nephropathy showing transplant vascular sclerosis and glomerulosclerosis. Mycophenolic acid (MPA) and rapamycin (RPM) are well known as strong inhibitors of VSMC proliferation, but their effects on the glomerular mesangial cells are not yet clearly understood. This study examined the effects of MPA or RPM on PDGF-induced proliferation and ECM accumulation in rat glomerular mesangial cells. Methods: Mesangial cells isolated from the glomeruli of Sprague-Dawley rats were cultured with DMEM containing 20% fetal bovine serum. Growth arrested and synchronized cells were administered with test drugs (MPA10 nM~10microM , RPM 0.1 nM~1microM) before the addition of PDGF 10 ng/mL. Cell proliferation was assessed by [3H]thymidine incorporation, collagen by [3H]proline incorporation, and fibronectin, ERK, and p38 MAPK by Western blot analysis. Results: PDGF increased mesangial cell proliferation by 4.64-fold. Compared to stimulated control, MPA above 500 nM and RPM above 10 nM showed a significant inhibitory effect in a dose- dependent manner. The IC50 of MPA and RPM against PDGF-induced mesangial cell proliferation were around 500 nM and 100 nM, respectively. The collagen synthesis was also inhibited by MPA and RPM, but the fibronectin secretion was inhibited by MPA alone. The proliferation of mesangial cell correlated with activation of ERK and p38 MAPK. MPA, but not RPM, inhibited ERK and p38 MAPK activation. Conclusion: This study demonstrated that MPA and RPM significantly inhibited PDGF-induced proliferation and ECM production in rat glomerular mesangial cells. The inhibitory effects of MPA, but not RPM, are correlated with ERK and p38 MAPK.ope