A scanning electron microscope study of normal and SV40-infected human keratinocytes

We have studied the changes in the surface ultrastructure of human epidermal keratinocytes after infection by the oncogenic virus, SV40. The surfaces of uninfected cells show patterns of dense microvilli and microridges in varying proportion with microridges predominating in the center of the developing keratinocyte colony and on the fully mature keratinocytes (squames) and the microvilli being more prevalent on the immature proliferative cells at the colony periphery. As the transformation process progressed over time highly microridged surfaces became less numerous. After many months in culture cell surfaces were found to exhibit more sparse, predominantly villous ultrastructure. The surface characteristics of the infected cells in long term culture were similar to those observed in a cell line derived from a squamous cell carcinoma.