Original title: Internal geometries regulate the symmetry of defect configurations in cell populations confined to domains with a negative Euler characteristic
Mina Kamao, Hiroyuki Miyoshi, Takaaki Nara, Hiroki Miyazako · September 2026
Living cells often line up together like tiny swimming rods, but tight spaces can disrupt this order. In biological tissues, cells frequently wrap around holes or solid obstacles. This forces spots called defects to form, where the cells cannot agree on which way to point. Scientists wanted to see how the geometry of internal obstacles controls these patterns. They grew muscle cells inside a chamber containing two round obstacles of different sizes. Because of the space's topology, two special defects with a value of -1/2 had to appear. The team discovered that changing the diameter of the obstacles directly alters where these defects sit. As the obstacles grow larger, the most stable defect pattern shifts steadily from a horizontal line, through a tilted angle, to a vertical alignment. The sizes of obstacles control the symmetry of cell arrangements, explaining how physical borders shape cellular forces.
Imagine organizing people to all face north in a room with pillars blocking the way. People near the pillars might face east or south, creating spots where the facing direction is inconsistent. In this paper, cells are like people, pillars are obstacles, and those inconsistent spots are defects. The size of the pillars changes how these defects are arranged.
This reveals how holes in biological tissues can change cell alignment patterns. Such knowledge helps understand organ development and movement during growth.
The study focuses only on domains with two circular obstacles and one cell type, so it may not generalize to other shapes or tissues. The agreement between theory and experiment is within 60 μm, which might not capture all biological variability.
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Internal geometries regulate the symmetry of defect configurations in cell populations confined to domains with a negative Euler characteristic — Mina Kamao, Hiroyuki Miyoshi, Takaaki Nara et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.