Multiscale Modeling of Tissue-Engineered Fat: Is There a Deformation-Driven Positive Feedback Loop in Adipogenesis?

Abstract

Mechanotransduction plays a role in adipose tissues by transducing the environmental mechanical signals. It is recognized that dynamic or cyclic mechanical strains suppress adipogenesis, but static strains activate the adipogenic signaling pathways. This phenomenon needs to be investigated further, given its potential use in tissue engineering of fat. We used in vitro cultures as model systems for studying differentiation and function of adipocytes. Additionally, using the finite element method, we developed here sets of multiscale models (MSM), which represent single or multiple adipocytes embedded in scaffolds, stimulated mechanically in a static regime. Based on in vitro adipocyte culture work, these models were employed to study the hypothesis that the loading state of the plasma membrane (PM) in adipocytes is influenced by neighboring cells, which could reflect positive feedback loops of en mass adipose cell differentiation. We demonstrate that under static loading, tensile strains at the PM increase with the stage of cell maturation. Furthermore, when the cell density was sufficient (above 19 cells per 100 μm(3)), progressive differentiation in some of the cells caused higher magnitudes of tensile strains in the PMs of other nearby cells. MSM are currently the only feasible means to correlate continuum (macrolevel) construct deformations to subcellular-level PM stretches in distorted cells. These macro-to-micro mechanobiology relationships, revealed through MSM, point to stimulations that promote the formation of lipid droplet accumulations and the increase of adipogenesis. Such models are a cost-effective useful platform for achieving better understanding of these deformation-driven cell processes toward optimized design of tissue-engineered fat constructs.

Ratio of total traction force to projected cell area is preserved in differentiating adipocytes

“…The forces applied by each cell on the polyacrylamide gel were calculated using constrained traction-force microscopy, 10,11 where bead-displacements in the gel (Fig. 22 The more uniform pattern of force application at the perimeters of the differentiating adipocytes likely facilitates anchoring of these non-migratory, rounded cells to the substrate. within the cell boundaries (Fig.…”

“…22 Preparing Gels CL-173) were cultured in a growth medium consisting of high-glucose (4.5 mg mL À1 ) Dulbecco's modified Eagle's medium (DMEM, Gibco, Carlsbad, CA), supplemented with 10% fetal bovine serum (Hyclone Thermo Fisher Scientific, Waltham, MA), 1% each of L-glutamine and sodium pyruvate (Biological Industries, Kibutz Beit Haemek, Israel), and 0.1% penicillin-streptomycin (Sigma).…”

“…7,8,22,23 The present study covers an additional critical mechanobiological aspect that has not been studied before: how morphology, forces and patterns of force application relate to and change during different stages of adipocyte differentiation. Specifically, we measured the forces applied by cells starting at the preadipocyte stage and progressing to maturation and adipogenesis, up to 14 days post induction of differentiation.…”

Asymmetry in traction forces produced by migrating preadipocytes is bounded to 33%

“…CL-173) in growth medium consisting of high-glucose (4.5 mg/ml) Dulbecco's modified Eagle's medium (DMEM, Gibco-Invitrogen, Carlsbad, CA), supplemented with 10% fetal bovine serum, 1% each of l -glutamine and sodium pyruvate (all from Biological Industries, Kibutz Beit Haemek, Israel), and 0.1% penicillin-streptomycin (Sigma-Aldrich, St Louis, MO). Cells were cultured and maintained in a humidified incubator at 37 °C, 5% CO 2 and were used at passages 10-20 from ATCC stock [18] .…”

Embryonic stem cells growing in 3-dimensions shift from reliance on the substrate to each other for mechanical support

“…Mechanical loading of cells through the substrate has also been shown to affect cell differentiation and development (Shoham and Gefen, 2012;Shoham et al, 2015), where stiffening of the cells themselves is also related to their function and can indicate disease states such as cancer (Gal and Weihs, 2012;Guck et al, 2005), or response of different cell types to changes in their environments (Poh et al, 2010). Those studies not only supply evidence to the significance of mechano-biology in stem cell development, but also provide important tools for controlling stem cells in vitro.…”