Unusual effects of a nanoporous gold substrate on cell adhesion and differentiation because of independent multi-branch signaling of focal adhesions.

A variety of cell behaviors, such as cell adhesion, motility, and fate, can be controlled by substrate characteristics such as surface topology and chemistry. In particular, the surface topology of substrates strongly affects cell behaviors, and the topological spacing is a critical factor in inducing cell responses. Various works have demonstrated that cell adhesion was enhanced with decreasing topological spacing although differentiation progressed slowly. However, there are exceptions, and thus, correlations between topological spacing and cell responses are still debated. We show that a nanoporous gold substrate affected cell adhesion while it neither affected osteogenic nor adipogenic differentiation. In addition, the cell adhesion was reduced with decreasing pore size. These do not agree with previous findings. A focal adhesion (FA) is an aggregate of modules comprising specific proteins such as FA kinase, talin, and vinculin. Therefore, it is suggested that because various extracellular signals can be independently branched off from the FA modules, the unusual effects of nanoporous gold substrates are related to the multi-branching of FAs.

Effects of actuation of nanoporous gold on cell orientation in a fibroblast sheet.

Mechanical stimulation such as flood flow often plays a vital role in the growth and maintenance of a living body, and it is important to investigate cell responses to mechanical stimulation. To date, cell responses to mechanical stimulation have been investigated in detail. However, the cell responses have been little known in a cell sheet. In the present study, a small cyclic strain (CS) of ~0.5% generated by a nanoporous gold actuator was loaded on a cell sheet of fibroblasts, and the effects of the CS on cell orientation were investigated. Individual cells were randomly distributed after the CS application, whereas cells were oriented in a specific direction after the CS application for the cell sheet. Thus, the CS had a different effect on the cell sheet from that on the individual cells. It is suggested that the cadherin/p-120 catenin complex played an important role in the cell response to mechanical stimulation in a cell sheet.

Grignard reagents as deprotonation agents for oxazoline-amido-phenolate ligands: structural and catalytic implications with the role of halogen ions.

In this study, various halogen-substituted Grignard reagents were assessed as deprotonating agents for the oxazoline-amido-phenolate ligand, leading to the formation of magnesium complexes. The newly synthesized complexes with halogen substituents displayed three distinct coordinative modes, all extensively characterized through crystallographic methods. The introduction of halogen substituents induced changes in the Lewis acid properties of the complexes, thereby impacting their structural attributes and catalytic behavior during the initiation and propagation of ring polymerization of cyclic esters.

Bioengineering of High Cell Density Tissues with Hierarchical Vascular Networks for Ex Vivo Whole Organs.

The development of tissue-like structures such as cell sheets, spheroids, and organoids has contributed to progress in regenerative medicine. Simultaneous achievement of scale up and high cell density of these tissues is challenging because sufficient oxygen cannot be supplied to the inside of large, high cell density tissues. Here, in vitro fabrication of vessels to supply oxygen to the inside of millimeter-sized scaffold-free tissues whose cell density is ≈200 million cells mL-1 , corresponding to those of native tissues, is shown. Hierarchical vascular networks by anastomosis of capillaries and a large vessel are essential for oxygen supply, whereas a large vessel or capillary networks alone make negligible contributions to the supply. The hierarchical vascular networks are formed by a top-down approach, which offers a new option for ex vivo whole organs without decellularization and 3D-bioprinting.

Heterogeneous role of integrins in fibroblast response to small cyclic mechanical stimulus generated by a nanoporous gold actuator.

It is important to understand the effects of mechanical stimulation on cell behaviors for homeostasis. Many studies have been performed on cell responses to mechanical stimuli, but the mechanosensing mechanism is still under debate. In the present study, experiments employing molecular dynamics (MD) simulations concerning the effects of cyclic mechanical stimulus on cell proliferation were performed based on the hypothesis that mechanosensing depends on integrin types. We used a nanoporous gold (NPG) actuator to prevent transfer of a mechanical stimulus via molecules other than integrins. Surprisingly, a small cyclic strain of only 0.5% enhanced the proliferation of fibroblasts. α5ß1 and αvß3 integrins showed high sensitivity to the mechanical stimulus, whereas α1ß1 and α2ß1 integrins exhibited low mechanosensitivity. The MD simulations showed that different conformational changes of the integrin headpiece induced by binding to the ECM led to a difference in mechanosensitivity between αI and αI-less integrin types. Thus, the present study provides evidence to support the hypothesis and suggests the mechanism for the heterogeneous roles of integrins in mechanosensing.