Microtopographies control the development of basal protrusions in epithelial sheets

Abstract

Cells are able to develop various types of membrane protrusions that modulate their adhesive, migratory, or functional properties. However, their ability to form basal protrusions, particularly in the context of epithelial sheets, is not widely characterized. The authors built hexagonal lattices to probe systematically the microtopography-induced formation of epithelial cell protrusions. Lattices of hexagons of various sizes (from 1.5 to 19 μm) and 5-10 μm height were generated by two-photon photopolymerization in NOA61 or poly(ethylene glycol) diacrylate derivatives. The authors found that cells generated numerous, extensive, and deep basal protrusions for hexagons inferior to cell size (3-10 μm) while maintaining a continuous epithelial layer above structures. They characterized the kinetics of protrusion formation depending on scaffold geometry and size. The reported formation of extensive protrusions in 3D microtopography could be beneficial to develop new biomaterials with increased adhesive properties or to improve tissue engineering.

Dynamics of Endothelial Engagement and Filopodia Formation in Complex 3D Microscaffolds

“…We studied cell behaviours in 3D geometries derived from hexagonal patterns. We previously described simple 3D hexagonal lattices for the generation of deep epithelial protrusions strongly increasing cell basal surface area [ 37 ], and we were interested in testing the behaviour of endothelial cells on these scaffolds, referred to here as «closed» structures ( Figure 1 a). However, the physiological microenvironment of endothelial cells is not compact, but composed of extracellular matrix fibres, whose fibrillary characteristics play a key role in their adhesive behaviour, and in particular in guidance events during angiogenesis.…”

“…Microstructures were realized with NOA61 (Norland Optical Adhesive) by two-photon polymerization. ( a ) Hexagonal lattices previously described [ 37 ] are referred to here as “closed” microstructures. ( b , c ) “Open” microstructures were realized by building hexagons on pillars, with a total height H of 7 µm (including the typical pillar height of 2–4 µm), and variable horizontal dimensions.…”

“…The vertical engagement is also expected to depend on the horizontal mesh size [37]. Therefore, we studied the engagement of HUVECs on open regular structures of different dimensions D, from 13.5 µm to 4.5 µm (Figure 4c-g To summarize, HUVECs formed a monolayer in the top of every microstructure studied, but was able to engage nuclei vertically from this monolayer only for large enough and open structures (Figure 4h).…”

High‐Throughput Scaffold System for Studying the Effect of Local Geometry and Topology on the Development and Orientation of Sprouting Blood Vessels

“…This is of particular relevance for creating microvascular networks that resemble intricate native structures, like those irrigating the nephron or hepatic units, which currently remain a great challenge . We suggest that by combining our two‐step seeding protocol with precise scaffold fabrication techniques, such as 3D jet writing, stereolithography, or microextrusion‐based 3D printing, it is possible to recreate the complex features of such intricate structures.…”

“…However, these works did not elucidate the dynamics affecting vascular network decisions regarding sprouting origin and vessel orientation within 3D structures. Understanding these results is imperative, especially with the rapid increase of scaffold fabrication techniques that permit fabrication of scaffolds with micrometer‐scale precision, such as 3D jet writing, extrusion‐based 3D printing, and stereolithography . This knowledge could help researchers design 3D environments that better suit their requirements for recreating a specific target tissue.…”