High Local Curvature Reduces Migration Rate of Multi-Layer Tissues

Development involves the migration of tissues composed of multiple cell layers. The mechanics of these motions remains largely unknown despite significant progress in understanding the migration of confluent monolayers. Thus, we investigate differences in spreading rate in multi-layer, X. laevis tissue explants, ranging in area from 0.12mm² to 2.63mm². The average spreading rate increases with initial size, from 22±5µm/hr to 45±5µm/hr. Since size affects both edge curvature and the number of cells, either could increase the spreading rate. Changes in curvature could affect the distribution of forces along the explant’s edge. However, since larger explants have more cells, the difference can also be explained by active tissue rearrangements, such as cell intercalation and programmed cell height changes. To distinguish between these models, we investigate the local spreading rate in explants with multiple curvatures, e.g. triangles. In these explants, spreading rate is lowest for regions of high curvature, even when the distance, and thus number of cells, is greater between the edge and the center of the explant. Our results indicate that the local rate of tissue migration depends on the initial curvature.