Mechanical remodeling of normally sized mammalian cells under a gravity vector

Abstract

Translocation of the dense nucleus along a gravity vector initiates mechanical remodeling of a cell, but the underlying mechanisms of cytoskeletal network and focal adhesion complex (FAC) reorganization in a mammalian cell remain unclear. We quantified the remodeling of an MC3T3-E1 cell placed in upward-, downward-, or edgeon-orientated substrate. Nucleus longitudinal translocation presents a high value in downward orientation at 24 h or in edge-on orientation at 72 h, which is consistent with orientation-dependent distribution of perinuclear actin stress fibers and vimentin cords. Redistribution of total FAC area and fractionized super mature adhesion number coordinates this dependence at short duration. This orientation-dependent remodeling is associated with nucleus flattering and lamin A/C phosphorylation. Actin depolymerization or Rho-associated protein kinase signaling inhibition abolishes the orientation dependence of nucleus translocation, whereas tubulin polymerization inhibition or vimentin disruption reserves the dependence. A biomechanical model is therefore proposed for integrating the mechanosensing of nucleus translocation with cytoskeletal remodeling and FAC reorganization induced by a gravity vector.-Zhang, C., Zhou, L., Zhang, F., Lü, D., Li, N., Zheng, L., Xu, Y., Li, Z., Sun, S., Long, M. Mechanical remodeling of normally-sized mammalian cells under gravity vector. FASEB J. 31, 000-000 (2017). www.fasebj.org KEY WORDS: gravity-directed • mechanosensing • nucleus translocation • cytoskeletal remodeling • FAC reorganization Cells on Earth are subject to a variety of mechanical forces, including gravity. Statolith, or amyloplast, has long been assumed to be a gravity receptor for plant species to sense, transduce, and respond to altered gravity (1); however, little is known about mechanisms that underlie gravisensing and gravitransduction in mammalian cells, even though a body of evidence confirms the effect of gravity on their biological responses (2). Conceptual studies have indicated that the spreading and mitosis of normally sized (;10 1 mm) mammalian cells are sensitive to the change in gravity vector. For example, randomizing the direction of gravity has no effect on the division orientation of Chinese hamster ovary cells that are point-attached in a vertical plane (3). Inversion of culture substrate cannot alter the number and function of attached osteoblasts, even though an immediate response-diminished viable osteoblast number-is observed in sparse, early cultures (4). Cell area, nucleus translocation, cell cycle, and F-actin reorganization vary significantly in a duration-dependent manner when Ros 17/2.8 cells make up a monolayer and are spread on downward-or edge-on-orientated substrate compared with those on an upward orientation (5). More quantitative analysis is observed in large-sized Xenopus oocytes (;1 mm), where the nucleolus sedimentation is dominant compared with the thermal fluctuation at gravity potential . thermal energy scale (6), which implies that the sediment...

Microgravity‐induced hepatogenic differentiation of rBMSCs on board the SJ‐10 satellite

“…Exposure to space microgravity for 3 d leads to a significant increase of vimentin expression ( Fig. 5I-L, O), which is in agreement with previous studies via clinostat (19) and, more likely, applied to strengthen the cytoskeletal network via vimentin cord, as observed under a varied-gravity vector (20).…”

“…5I, J) but yielded disperse distribution over the entire cell on the ground (Fig. 5K, L), as predicted previously (20,31). Quantifying those expressions between space and ground samples, total expressions of actin ( Fig.…”

“…In addition to those biochemical factors, the mechanical factors originating from space microgravity could play a role in directing rBMSCs into HLCs via mechanosensation, which is induced by cell adhesion onto the substrate and by force transmission through cytoskeletons (20,31,44). In this work, a stem cell phenotype-related adhesive molecule, CD34, maintained the similar expression, but other conventional adhesive molecules of CD44, ICAM-1, and VCAM-1 yieldedreduced expressions in space (Fig.…”

“…It is well known that modified gravity not only affects the organism as a whole but also modulates the molecular processes in individual cells (19,20). We proposed that gravity could influence the hepatogenic differentiation of MSCs.…”

An integration design of gas exchange, bubble separation, and flow control in a space cell culture system on board the SJ-10 satellite

“…To investigate the mechanobiological coupling mechanisms of cellular responses to altered gravity, [8][9][10][11] a cell biomechanics experiment was performed on board the SJ-10 satellite, which is a recoverable scientific experimental satellite that launched on 6th April and recovered on 18th April 2016. 12 Taking all the above technical considerations, a novel space cell culture system (SCCS) was designed to conduct the experiment under space microgravity and within the technical constraints of the SJ-10 satellite platform.…”