The epithelium is a tissue that lines cavities and structural surfaces throughout the body. As an embryo develops, the tissues fold into complex three-dimensional shapes that lead to the organs. Epithelial cells are precisely the building blocks of this process that form, for example, the outer layer of the skin and line the blood vessels and organs of all animals.
As such, this epithelial tissue is made up of millions and millions of these tiny cells. These cells are tightly packed.
Until now, we represented epithelial tissue cells (or epithelium) as prisms, but an international team of scientists led by biology expert Luis M. Escudero from the University of Seville (Spain) has discovered that this model does not correspond to the organization of cells in epithelial tissues under the microscope, identifying a new geometric shape in the process.
It looks like a prism, but while one end of the prism has five edges, the other has six – a geometric quirk made possible by a Y-shaped split that splits one of the edges of the prism in two, creating a mini triangle.
This strange “twisted prism” may sound like one of the drawings that artist MC Escher might have experimented with, but according to the team, this shape has never been previously described in the scientific literature.
They found that, during tissue flexing, epithelial cells take on a previously undescribed shape that allows cells to minimize energy use and maximize bonding stability . They have called this new shape: escutoid, “a geometric solution for the three-dimensional packing of epithelia.”
The researchers made this finding through computer models that used Voronoi diagramming , a tool used in various fields to understand geometric organization. To his surprise, the discovered additional shape didn’t even have a name in math, so a fabulous opportunity presented itself to name a new geometric shape.
The group has named the new form “escutoid” because of its resemblance to the scutellum, the back of a thorax or midsection of an insect.
Experiments
To verify the model’s predictions, they analyzed the three-dimensional packaging of different tissues in different animals. The experimental data confirmed that the epithelial cells adopted three-dimensional organizational shapes and motifs similar to those predicted by the computational model.
Using biophysical approaches, the scientists argue that escutoids – something like a crooked prism – stabilize the three-dimensional bond and make it energy efficient.
Their findings could pave the way for understanding the three-dimensional organization of epithelial organs and lead to advances in tissue engineering.
“In addition to this fundamental aspect of morphogenesis, the ability to design tissues and organs in the future is fundamentally based on the ability to understand, and then control, the three-dimensional organization of cells,” the authors write in the published study. the journal Nature Communications.
“We have unlocked nature’s solution for efficient epithelial flexion,” the authors comment.
Reference: Pedro Gómez-Gálvez et al, Scutoids are a geometrical solution to three-dimensional packing of epithelia, Nature Communications (2018). DOI: 10.1038 / s41467-018-05376-1
