Symmetries of the Umbrella Cell Surface

The outer layer of cells that lines the urinary tract are called umbrella cells. These are large, well-shaped cells that not infrequently contain more than one nuclei. The umbrella cells are sewn together like a patchwork with tiny but numerous proteins creating what is called tight junctions. The tight junctions make the patchwork impermeable to water and ions and other dissolved molecules, and also protect underlying structures against pathogens like bacteria.

I have for many years been fascinated by symmetries of nature and when i was reading this scientific article about the urothelium the other day I saw a beautiful photo. It was an image, created by a scanning electron microscope, showing the surface of an umbrella cell with great magnification.

On the surface of the umbrella cell there are raised ridges and deep valleys. In the valleys there are most beautiful structures called plaques that consist of so-called AUM particles. The AUM particles, in turn, is thought to be built up by a type of proteins called uroplakins. Anywho, these AUM particles exhibit a beautiful six-fold symmetry shown on the image above. One plaque consist of approx 1000-3000 AUM particles!

The plaques and AUM particles have been known for some time, but their function is not well understood. One speculation is that they modulate the surface area of the umbrella cell during filling and voiding of the bladder.

Something to think about next time you answer the call of nature..