An ultrastructural study of rat glomerular epithelial cells in culture

Cultured, rat glomerular podocytes were examined by electron microscopy and immunohistochemistry in order to determine their origin. The outgrowth of polygonal cells was noted first. Large arboroid cells were occasionally observed around the polygonal cells. Immunostaining of these large arboroid cells for the intermediate filament proteins showed an intensely positive reaction for vimentin, whereas cytokeratin was not detected. In the polygonal cells, however, both cytokeratin and vimentin were sometimes detected. Although scanning electron microscopy did not detect any specific irregularities in podocytes on the surface of the glomerulus, developing polygonal cells were observed. Both transmission and scanning electron microscopies revealed the polygonal cells to be similar to Bowman's capsule epithelial cellsin situ. The vascular poles of the cultured glomeruli were always in contact with the culture dish. A residual Bowman's capsule was also observed. These results suggest that polygonal cells originate from the epithelial cells of the residual Bowman's capsule, whereas large arboroid cells arise from podocytes. This study was presented at the 25th Annual Meeting of the Clinical Electron Microscopy Society of Japan, Matsumoto, September 28–30, 1993.