Actomyosin, vimentin and LINC complex pull on osteosarcoma nuclei to deform on micropillar topography

Abstract

Cell deformation occurs in many critical biological processes, including cell extravasation during immune response and cancer metastasis. These cells deform the nucleus, its largest and stiffest organelle, while passing through narrow constrictions in vivo and the underlying mechanisms still remain elusive. It is unclear which biochemical actors are responsible and whether the nucleus is pushed or pulled (or both) during deformation. Herein we use an easily-tunable poly-L-lactic acid micropillar topography, mimicking in vivo constrictions to determine the mechanisms responsible for nucleus deformation. Using biochemical tools, we determine that actomyosin contractility, vimentin and nucleo-cytoskeletal connections play essential roles in nuclear deformation, but not A-type lamins. We chemically tune the adhesiveness of the micropillars to show that pulling forces are predominantly responsible for the deformation of the nucleus. We confirm these results using an in silico cell model and propose a comprehensive mechanism for cellular and nuclear deformation during confinement. These results indicate that microstructured biomaterials are extremely versatile tools to understand how forces are exerted in biological systems and can be useful to dissect and mimic complex in vivo behaviour.

Nuclear mechanosensing controls MSC osteogenic potential through HDAC epigenetic remodeling

“…The cytoskeleton, LINC complex, and the physical attachment to nuclear lamins have been shown to be highly important in nuclear integrity, chromatin remodeling, and subsequent differentiation or cell reprogramming ( 34 , 35 ). Multiple mechanisms have been suggested for Lamin A/C contribution to transcriptional changes.…”

Mechanical and Non‐Mechanical Functions of Filamentous and Non‐Filamentous Vimentin

“…[ 69,70 ] One model for this behavior is that contractile forces generated by apical stress fibers push down on the nucleus, compressing it. [ 70–72 ] Several studies have now shown that disruption or deletion of the VIF network results in changes to nuclear shape, [ 22,73 ] even when the F‐actin network remains unchanged. [ 74 ] In the absence of VIF, the nucleus rounds up and is no longer compressed.…”

“…The exact mechanism by which VIFs apply forces to the nuclear envelope remains unclear, but it seems to require the LINC complex. [ 22 ] Another possibility is through vimentin's crosslinks with actomyosin filaments where cutting these links by removing VIFs would decrease the force felt by the nucleus.…”

Mechanical Adaptations of Epithelial Cells on Various Protruded Convex Geometries

“…It has been widely known that 2D geometry can affect diverse cellular responses such as cell shape, proliferation, differentiation, mechanoresponsive marker expression, and underlying mechanism has been suggested that confined adhesive area which can be tuned by geometry of 2D patterns cause interfacial tension at the boundary [6,12]. As both topography and adhesiveness of the surface may play essential roles in cellular behavior [43], we treat the whole surface of the 3D geometry to be adhesive so that we can elucidate the roles of 3D geometry independent of chemical adhesiveness.…”