Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
Department of Internal Medicine, University of Nebraska Medical Center and VA Nebraska-Western Iowa Health Care System, Omaha, NE, 68105, USA.
Biochem Biophys Res Commun. 2022 May 28;606:42-48. doi: 10.1016/j.bbrc.2022.03.078. Epub 2022 Mar 17.
It is increasingly recognized that interaction of adipose cells with extracellular mechanophysical milieus may play a role in regulating adipogenesis and differentiated adipocyte function and such interaction can be mediated by the mechanics of adipose cells. We measured the stiffness and traction force of adipose cells and examined the role of Rho/ROCK, the upstream effector of actin cytoskeletal contractility, in affecting these mechanical properties. Cellular Young's modulus obtained from atomic force microscopy (AFM) was significantly reduced by ROCK inhibitor (Y-27632) but elevated by Rho activator (CN01), for both preadipocytes and differentiated adipocytes. Immunofluorescent imaging suggested this could be attributed to the changes in Rho/ROCK-induced stressed actin filament formation. AFM also confirmed that differentiated adipocytes had higher stiffness than preadipocytes. On the other hand, traction force microscopy (TFM) revealed differentiated adipocytes exerted lower traction forces than preadipocytes. Traction forces of both preadipocytes and adipocytes were decreased by ROCK inhibition, but not significantly altered by Rho activation. Notably, an increasing trend of traction force with respect to cell spreading area was detected, and this trend was substantially amplified by Rho activation. Such traction force-cell area correlation was an order-of-magnitude smaller for differentiated adipocytes relative to preadipocytes, potentially due to disrupted force transmission through cytoskeleton-focal adhesion linkage by lipid droplets. Our work provides new data evidencing the Rho/ROCK control in adipose cell mechanics, laying the groundwork for adipocyte mechanotransduction studies on adipogenesis and adipose tissue remodeling.
人们越来越认识到，脂肪细胞与细胞外机械环境的相互作用可能在调节脂肪生成和分化的脂肪细胞功能中发挥作用，这种相互作用可以通过脂肪细胞的力学来介导。我们测量了脂肪细胞的硬度和牵引力，并研究了 Rho/ROCK（肌动球蛋白细胞骨架收缩性的上游效应物）在影响这些机械特性中的作用。原子力显微镜（AFM）获得的细胞杨氏模量通过 ROCK 抑制剂（Y-27632）显著降低，但通过 Rho 激活剂（CN01）升高，对于前体脂肪细胞和分化的脂肪细胞都是如此。免疫荧光成像表明，这可能归因于 Rho/ROCK 诱导的应激肌动蛋白丝形成的变化。AFM 还证实，分化的脂肪细胞比前体脂肪细胞具有更高的硬度。另一方面，牵引力显微镜（TFM）显示分化的脂肪细胞施加的牵引力低于前体脂肪细胞。ROCK 抑制降低了前体脂肪细胞和脂肪细胞的牵引力，但 Rho 激活对其没有明显影响。值得注意的是，检测到牵引力随细胞扩展面积的增加而呈上升趋势，而这种趋势通过 Rho 激活被大大放大。对于分化的脂肪细胞相对于前体脂肪细胞，这种牵引力-细胞面积的相关性要小一个数量级，这可能是由于脂滴通过细胞骨架-黏附连接破坏了力的传递。我们的工作提供了新的数据，证明了 Rho/ROCK 对脂肪细胞力学的控制，为脂肪生成和脂肪组织重塑的脂肪细胞机械转导研究奠定了基础。
