Griffin Maureen A, Sen Shamik, Sweeney H Lee, Discher Dennis E
Biophysical Engineering Laboratory, 112 Towne Building, and Pennsylvania Muscle Institute, University of Pennsylvania, D-700 Richards Building, 3700 Hamilton Walk, Philadelphia, PA 19104, USA.
J Cell Sci. 2004 Nov 15;117(Pt 24):5855-63. doi: 10.1242/jcs.01496. Epub 2004 Nov 2.
Tissue cells generally pull on their matrix attachments and balance a quasi-static contractility against adequate adhesion, but any correlation with and/or influence on phenotype are not yet understood. Here, we begin to demonstrate how differentiation state couples to actomyosin-based contractility through adhesion and substrate compliance. Myotubes are differentiated from myoblasts on collagen-patterned coverslips that allow linear fusion but prevent classic myotube branching. Post-fusion, myotubes adhere to the micro-strips but lock into a stress fiber-rich state and do not differentiate significantly further. In contrast, myotubes grown on top of such cells do progress through differentiation, exhibiting actomyosin striations within one week. A compliant adhesion to these lower cells is suggested to couple to contractility and accommodate the reorganization needed for upper cell striation. Contractility is assessed in these adherent cells by mechanically detaching one end of the myotubes. All myotubes, whether striated or not, shorten with an exponential decay. The cell-on-cell myotubes relax more, which implies a greater contractile stress. The non-muscle myosin II inhibitor blebbistatin inhibits relaxation for either case. Myotubes in culture are thus clearly prestressed by myosin II, and this contractility couples to substrate compliance and ultimately influences actomyosin striation.
组织细胞通常会牵拉其与基质的附着点，并在适度的黏附力作用下平衡准静态收缩力，但目前尚未明确其与细胞表型之间的任何关联及/或影响。在此，我们开始证明分化状态如何通过黏附作用和底物顺应性与基于肌动球蛋白的收缩力相互耦合。肌管是由成肌细胞在胶原图案化的盖玻片上分化而来，这种盖玻片允许线性融合，但能防止经典的肌管分支。融合后，肌管附着在微条上，但会锁定在富含应力纤维的状态，且不会进一步显著分化。相比之下，生长在这些细胞之上的肌管确实会经历分化过程，在一周内呈现出肌动球蛋白条纹。推测与这些下层细胞的顺应性黏附作用与收缩力相互耦合，并适应上层细胞形成条纹所需的重组过程。通过机械分离肌管的一端来评估这些贴壁细胞的收缩力。所有肌管，无论是否有条纹，都会以指数衰减的方式缩短。细胞间肌管的松弛程度更大，这意味着收缩应力更大。非肌肉肌球蛋白II抑制剂blebbistatin会抑制两种情况下的松弛。因此，培养中的肌管显然受到肌球蛋白II的预应激作用，这种收缩力与底物顺应性相互耦合，并最终影响肌动球蛋白条纹的形成。
