You are interested in epithelial tissue formation and work in a lab studying Madin-Darby canine kidney (MDCK) cells. MDCK cells spontaneously form hollow epithelial vesicles. Staining these vesicles with an anti-actin antibody demonstrates the existence of apical microvilli near the central cavity of the vesicle. A new postdoctoral fellow in the lab comes to you in a panic. You had given her some dissociated MDCK cells that have been cultured as single cells in a collagen matrix. Because the cells did not look obviously polarized to her, she stained the dissociated MDCK cells to visualize the microvilli and she does not see any signs of polarized microvilli localization in these cells. Explain why you are confident that you did not give her the wrong cell line.