Cytoskeletal Disassembly and Cell Rounding Promotes Adipogenesis from ES Cells

Abstract

Biomechanical signals such as cell shape and spreading play an important role in controlling stem cell commitment. Cell shape, adhesion and spreading are also affected by calreticulin, a multifunctional calcium-binding protein, which influences several cellular processes, including adipogenesis. Here we show that cytoskeletal disruption in mouse embryonic stem cells using cytochalasin D or nocodazole promotes adipogenesis. While cytochalasin D disrupts stress fibres and inhibits focal adhesion formation, nocodazole depolymerises microtubules and promotes focal adhesion formation. Furthermore, cytochalasin D increases the levels of both total and activated calcium/calmodulin-dependent protein kinase II, whereas nocodazole decreases it. Nevertheless, both treatments significantly increase the adipogenic potential of embryonic stem cells in vitro. Both cytochalasin D and nocodazole exposure caused cell rounding suggesting that it is cell shape that causes the switch towards the adipogenic programme. Calreticulin-containing embryonic stem cells, under baseline conditions, show low adipogenic potential, have low activity of signalling via calcium/calmodulin-dependent protein kinase II and display normal adhesive properties and cellular spreading in comparison to the highly adipogenic but poorly spread calreticulin-deficient ES cells. We conclude that forced cell rounding via cytoskeletal disruption overrides the effects of calreticulin, an ER chaperone, thus negatively regulating adipogenesis via focal adhesion-mediated cell spreading.

Factor XIII-A transglutaminase acts as a switch between preadipocyte proliferation and differentiation

“…[47][48][49][50] An examination of cytoskeletal dynamics in NC9-treated preadipocytes plated on FN under serum-free conditions showed that the inhibitor dramatically reduced actin stress fiber formation and increased cortical actin assembly compared with control cells. This was also associated with reduced focal adhesion assembly as seen by a lack of vinculin colocalization with actin stress fibers ( Figure 4A).…”

Topographically and Chemically Modified Surfaces for Expansion or Differentiation of Embryonic Stem Cells

“…This response is mediated by modulation of focal adhesion length and myosin II activity (Engler et al, 2006). The finding that disruption of cytoskeletal structures manipulated cell morphology and specifically directed the cells towards an adipogenic fate (Feng et al, 2010) also supports an involvement of cytoskeletal tension in regulation of hES cell differentiation state. Besides externally imposed mechanical cues like matrix stiffness also cyclic biaxial strain affects the differentiation state of hES cells (Saha et al, 2006).…”

“…Our work highlights the important effects of defined micro-topography on ES-cell-colony formation and morphology. Since cell shape (Feng et al, 2010) and colony morphology (Lee et al, 2009) are linked to ES-cell differentiation, topography offers an extra level of possibilities for directing ES-cell fate through modulation of cell and colony morphology. Furthermore, the BSSA approach has been applied to other cell types as well, thereby facilitating immediate comparison between cell types over the same topographical patterns and ranges produced in the same material (Kolind et al, 2010;Lovmand et al, 2009).…”

Simvastatin enhances Rho/actin/cell rigidity pathway contributing to mesenchymal stem cells’ osteogenic differentiation

“…23,24 In addition, disrupting cytoskeleton or decreasing cell rigidity reduces the expression of osteoblastic gene, including alkaline phosphatase (ALP) and osteopontin, 25,26 and further promotes adipogenic differentiation by increasing peroxisome proliferator-activated receptor (PPAR) gamma. 18,20,27 The cytoskeletal organization and myosin-mediated cytoskeleton tension are regulated by RhoA and its effector, Rho-associated protein kinase (ROCK). Activation of RhoA causes human MSCs to undergo osteogenic differentiation by upregulating the expression of Runx2 gene; however, inactivation of RhoA causes cells to undergo adipogenic differentiation by increasing expression of the adipogenic marker gene PPAR gamma.…”