(A) Through passage 4, all substrates studied showed cells with the “cobblestone” appearance suggestive of undifferentiated podocytes. (B) At passage 5, cultures contained cells that had a differentiated podocyte cell morphology with arborization, processes extended from cell bodies, and a large cytoplasmic to nuclear volume ratio. (C) Renal ECM contained cells with an undifferentiated podocyte morphology through all passages (1 through 5) (20x, bar = 100 μm).