Mesangial Cells Connected by the N-Cadherin-Catenin System in the Rat Kidney

Background/Aims: Mesangial cells bear the tensional forces generated in the glomerular capillary wall. Not only mesangial cells per se, but also their intercellular junctions should be physically stable against the tensional forces; this prompted the search for actin filament-reinforced adherens junctions of mesangial cells. We previously reported α- and β-catenins localized at the cell-cell contact sites of mesangial cells in the rat. Classical cadherin expressed by mesangial cells, however, remains to be elucidated. Methods: Expression of classical cadherins, especially N-cadherin, was examined in rat glomeruli by ribonuclease protection assay, Western blot analysis and immunofluorescence and immunoelectron microscopy. Results: Ribonuclease protection assay detected significant expression of N-cadherin in rat glomeruli. Western blot analysis showed that rabbit and murine antibodies against N-cadherin reacted with a specific band in isolated glomeruli. Immunofluorescence microscopy revealed that both antibodies reacted only with the mesangium in glomeruli. Immunoelectron microscopy demonstrated that the immunogold particles for N-cadherin were found predominantly at cell-cell contact sites of mesangial cells where actin filaments concentrated. Conclusion: N-cadherin interconnects mesangial cells, suggesting that the cadherin-catenin-actin filament system in the mesangium may play a role in the counteraction of the hydraulic pressure gradient across the capillary wall.