Subcellular details of early events of differentiation induced by retinoic acid in human neuroblastoma cells detected by atomic force microscope.

Atomic force microscopy (AFM) is gaining ever-increasing attention in biology as it allows us to achieve very high resolution both in air and in liquid. Recently, this technique has been employed for the observation of dynamic phenomena of cells in their culture medium. We employed this technology for comparing different morphologies, neuronal and substrate-adherent type, of cell lines of human neuroblastoma, a tumor derived from neuroectodermal tissue. The AFM image allows to confirm and enrich the information given by optical microscopes adding further details especially on the neural protrusions. Furthermore, we took advantage of the possibility to perform the observation of the cells in their culture medium for studying the neuroblastoma cell differentiation. For the first time, we detected the very early events of the outgrowth of neurite-like structures induced by retinoic acid. A time-course experiment has showed that the acid induces changes in the cellular membrane and dramatic modifications in the cytoskeleton already within 2 h.