THE LONG AND SHORT OF IT: The epithelium of the cervix consists of both flattened squamous cells (left, top), which occur in many layers and slough off as they are replaced by cells beneath them, and columnar cells (left, bottom), which form a mucus-secreting monolayer covered in microvilli.© P.M. MOTTA & S. MAKABE/SCIENCE SOURCE IMAGES
In 1998, University of Bath biologist David Tosh had a eureka moment. He noticed that some of the rat pancreatic exocrine cells he was working with had become unusually large and flat. After further testing, he identified the cause of the abnormality: the cells, which belonged to an established line called AR42j, were no longer pancreatic cells at all; they were hepatocytes, the principal cell type of the liver. The cells had changed their identity simply under the influence of the synthetic hormone dexamethasone, which had been added to the medium to enhance endocrine cell secretions.1
This wasn’t the first demonstration that cells could change type. Pathologists had long reported the transformation of one cell type into another in humans, a normally harmless process known ...
