Features of cultured primary (P0) and cells expanded in Epilife medium to passage 5 (P5).

<p>Normal karyotype of P0 hAEC was retained at P5 (<b>A</b>). Transmission electron micrograph of P0 hAEC showed intercellular junctions (IJ), a multiloculated peripheral appearance compared to P5 hAEC. P5 cells had extensive rough endoplasmic reticulum (rER) and fewer cell surface projections. P0 and P5 cells showed high nuclear (N) to cytoplasmic ratio (<b>B</b>). P0 hAEC seeded at low density formed clonal colonies unlike P5 hAEC (<b>C</b>). hAEC lacked alkaline phosphatase activity unlike human embryonal carcinoma (hEC) cell line used as a positive control (<b>D</b>). Scale bars = 100 µm (<b>A–B</b>); 5 µm and 1 µm (<b>C</b>).