MOUSE GLOMERULAR EPITHELIAL-CELLS IN CULTURE WITH FEATURES OF PODOCYTES IN-VIVO EXPRESS AMINOPEPTIDASE-A AND ANGIOTENSINOGEN BUT NOT OTHER COMPONENTS OF THE RENIN-ANGIOTENSIN SYSTEM

The binding of antibodies to podocytic antigens such as the Heymann an tigen or aminopeptidase A may lead to the induction of a membranous gl omerulonephritis in several species. To study the possible future inte ractions of antibodies with antigens on these podocytes, epithelial ce lls from isolated mouse glomeruli were cultured. By indirect immunoflu orescence, the cells were positive for cytokeratin, vimentin, desmin, and the ZO-1 protein, a component of the tight junction complex. When rat monoclonal antibodies were used, the cells were also positive for the hydrolases aminopeptidase A and dipeptidyl peptidase IV, and they stained with ASD-33, a monoclonal antibody that recognized an epitope only present on the cell membranes of mouse podocytes. They were negat ive for the von Willebrand factor and did not stain with a monoclonal antibody (ASD-13) that binds to endothelial cells of glomeruli and per itubular capillaries. By electron microscopy, the cells showed tight j unctions but lacked Weibel Palade bodies (endothelium), desmosome, and cilia (parietal epithelium). The mRNA expression of several component s of the renin-angiotensin system was also examined, and some factors indirectly coupled to the renin-angiotensin system component angiotens in II in this podocytic culture by RT-PCR analysis. mRNA Expression fo r the angiotensin II degrading hydrolase aminopeptidase A and angioten sinogen was found, but this was not found for any other component of t his system, such as renin, angiotensin-converting enzyme, or the angio tensin II receptors AT1a, AT1b, and AT2. Low mRNA expression for dipep tidyl peptidase IV was observed. In addition, expression of the growth factors transforming growth factor-beta and interleukin-7, and the ex tracellular matrix components fibronectin, laminin B2, perlecan, and c ollagen IV alpha 1, was observed. Given these characteristics, a glome rular epithelial cell culture with features of podocytes in vivo that will allow future studies on the interaction of anti-aminopeptidase A monoclonal antibodies and angiotensin II with aminopeptidase A was est ablished. This is of interest in light of the observation that injecti on of mice with anti-aminopeptidase A antibodies causes an acute album inuria.