Glomerular mesangial cell migration in response to platelet-derived growth factor

Platelet-derived growth factor (PDGF) is a potent mitogenic and chemotactic protein for a variety of cell types. Glomerular mesangial cells also respond to PDGF in terms of proliferation, but, to date, have not been examined for migratory behavior in response to a specific growth factor. Here, we examine the ability of isolated rat mesangial cells to migrate toward gradients of purified PDGF. Chemotaxis assays were performed in two-compartment blind well chambers, each compartment separated by a 14-microns porous filter membrane. Human PDGF was added to 200 microliters of RPMI 1640 medium in the lower compartment beneath the filters to make incremental concentrations from 2.5 to 50 units/ml. Control compartments received diluent without PDGF. Mesangial cells in RPMI 1640 medium were added to the upper compartments and the chambers were incubated for 8 hours at 37 degrees C. After fixation, the number of cells on the underside of the filter were counted by scanning electron microscopy. A linear dose response of mesangial cell migration toward increasing concentrations of PDGF was observed, achieving cell numbers of 9-fold over controls at 50 units/ml. Migratory cells were verified as mesangial cells by fluorescence expression of actin, myosin, and desmin and absence of expression of leukocyte common antigen and Ia antigen. Addition of equimolar concentrations of PDGF on both sides of the filter or addition of anti-PDGF antibody to the lower chamber containing PDGF negated the chemotactic response. These studies indicate that mesangial cells migrate in response to PDGF. This mechanism may, in part, play a role in some forms of mesangial proliferative glomerular disease.