I’m an old fart…heck, I was born an old fart. So, you won’t be seeing me in da club. But if I ever go, I’ll be reassured knowing that bouncers kick the knuckleheads out and keep the crowd to a safe limit. Though they may be beefy tough guys, bouncers are clearly getting their cues from epithelial cells, which extrude both dying and healthy cells when overcrowded, according to a recent paper.
Cell extrusion is the process in which epithelial cells get rid of apoptotic, or dying, cells. By getting rid of dying cells, the epithelial sheet can maintain its tight barrier function for the tissue or organ. A recent paper shows that epithelial sheets can also extrude healthy, living cells. According to Eisenhoffer and colleagues, an epithelial sheet overcrowded with cells will extrude living cells in order to maintain tissue homeostasis. This mechanism was found in human, canine, and zebrafish epithelial cells, and could be induced by overcrowding epithelial cells in a stretched, then released, chamber in the lab. Cells are extruding in the images of human colon epithelial tissue above. A dying cell in the process of extruding (right) shows caspase-3 staining (green, arrow), a marker for apoptosis, while a living cell extruding (left, arrowhead) does not.
Eisenhoffer, G., Loftus, P., Yoshigi, M., Otsuna, H., Chien, C., Morcos, P., & Rosenblatt, J. (2012). Crowding induces live cell extrusion to maintain homeostatic cell numbers in epithelia Nature, 484 (7395), 546-549 DOI: 10.1038/nature10999
Adapted by permission from Macmillan Publishers Ltd, copyright ©2012