Mechanical forces play an increasingly recognized role in modulating cell function. This report demonstrates mechanosensing by T cells, using polyacrylamide gels presenting ligands to CD3 and CD28. Naive CD4 T cells exhibited stronger activation, as measured by attachment and secretion of IL-2, with increasing substrate elastic modulus over the range of 10-200 kPa. By presenting these ligands on different surfaces, this report further demonstrates that mechanosensing is more strongly associated with CD3 rather than CD28 signaling. Finally, phospho-specific staining for Zap70 and Src family kinase proteins suggests that sensing of substrate rigidity occurs at least in part by processes downstream of T-cell receptor activation. The ability of T cells to quantitatively respond to substrate rigidly provides an intriguing new model for mechanobiology.

Chopra A, Tabdanov E, Patel H, Janmey PA, Kresh JY. Cardiac myocyte remodeling mediated by N-cadherin-dependent mechanosensing. Am J Physiol Heart Circ Physiol 300: H1252-H1266, 2011. First published January 21, 2011 doi:10.1152 doi:10. /ajpheart.00515.2010 adhesions are crucial in maintaining the structural and functional integrity of cardiac cells. Little is known about the mechanosensitivity and mechanotransduction of cell-to-cell interactions. Most studies of cardiac mechanotransduction and myofibrillogenesis have focused on cell-extracellular matrix (ECM)-specific interactions. This study assesses the direct role of intercellular adhesion, specifically that of N-cadherin-mediated mechanotransduction, on the morphology and internal organization of neonatal ventricular cardiac myocytes. The results show that cadherin-mediated cell attachments are capable of eliciting a cytoskeletal network response similar to that of integrinmediated force response and transmission, affecting myofibrillar organization, myocyte shape, and cortical stiffness. Traction forces mediated by N-cadherin were shown to be comparable to those sustained by ECM. The directional changes in predicted traction forces as a function of imposed loads (gel stiffness) provide the added evidence that N-cadherin is a mechanoresponsive adhesion receptor. Strikingly, the mechanical sensitivity response (gain) in terms of the measured cell-spread area as a function of imposed load (adhesive substrate rigidity) was consistently higher for N-cadherin-coated surfaces compared with ECM protein-coated surfaces. In addition, the cytoskeletal architecture of myocytes on an N-cadherin adhesive microenvironment was characteristically different from that on an ECM environment, suggesting that the two mechanotransductive cell adhesion systems may play both independent and complementary roles in myocyte cytoskeletal spatial organization. These results indicate that cell-to-cell-mediated force perception and transmission are involved in the organization and development of cardiac structure and function.cell-to-cell interaction; myofibrillogenesis; extracellular matrix; cell biomechanics NUMEROUS STUDIES IN CELL MECHANOBIOLOGY have shown that the stiffness of the material on which or within which cells grow has sizeable, specific effects on cell morphology, cytoskeletal structure, motility, differentiation, and proliferation (16,39,43,50,62). Mechanical cues, which can act together with or in opposition to chemical stimuli, are potentially associated with pathological conditions that occur in cancer, fibrotic disease, abnormal wound healing, and cardiac remodeling. The mechanical microenvironment of the cell in vivo is defined by its attachment to the extracellular matrix (ECM) and to other cells via forces generated and transmitted across cell-to-cell junctions constituting a network assembly of cells. Nearly all studies of cell mechanobiology in vitro have focused on the attachment of subconfluent cells to ECM ligands such as fibronectin, collagen, and laminin. ...

SUMMARYCancer cell migration through and away from tumors is driven in part by migration along aligned extracellular matrix, a process known as contact guidance (CG). To concurrently study the influence of architectural and mechanical regulators of CG sensing, we developed a set of CG platforms. Using flat and nanotextured substrates with variable architectures and stiffness, we show that CG sensing is regulated by substrate stiffness and define a mechanical role for microtubules and actomyosin-microtubule interactions during CG sensing. Furthermore, we show that Arp2/3-dependent lamellipodia dynamics can compete with aligned protrusions to diminish the CG response and define Arp2/3- and Formins-dependent actin architectures that regulate microtu-bule-dependent protrusions, which promote the CG response. Thus, our work represents a comprehen-sive examination of the physical mechanisms influ-encing CG sensing.