Microengineering Approaches for Regenerative Medicine

Stem cells, especially human pluripotent stem cells (hPSCs), hold significant promise for modeling developmental and disease processes, drug and toxicology screening, and cell-based regenerative medicine. Most hPSC studies have so far focused on identifying extrinsic soluble factors, intracellular signaling pathways, and transcriptional regulatory networks involved in regulating hPSC behaviors. We focus on the development and applications of some novel synthetic micromechanical systems to understand the mechano-sensitive and -responsive properties of hPSCs and their functional regulation of self-renewal, directed differentiation, and survival of hPSCs. First, we have demonstrated that rigid PDMS micropost arrays (PMAs) support the maintenance of pluripotency of hPSCs. Blocking cytoskeleton contractility by blebbistatin and inhibiting E-cadherin functions by DECMA-1 antibody both impair mechanoresponsive self-renewal of hPSCs on rigid substrates. We have further achieved efficient neuroepithelial induction, caudalization, and motor neuron differentiation from hPSCs combining soft PMAs (Eeff \u3c 5kPa) with dual Smad inhibition. The purity and yield of functional motor neurons derived from hPSCs within 23 days of culture using soft PMAs were improved four- and twelve-fold, respectively, compared to coverslips or rigid PMAs. Our mechanistic work has helped reveal for the first time that biomechanical cues, including intracellular contractile forces and cell shape, converge and reinforce signal integration of TGF-β, Wnt, Hippo/YAP, Rho GTPase, and the actomyosin cytoskeleton to regulate the neural plate specification. We also developed a novel acoustic tweezing cytometry (ATC) utilizing ultrasound pulses to actuate functionalized lipid-encapsulated microbubbles (MBs) targeted to cell surface integrin receptors to exert subcellular mechanical forces in the pN - nN range. ATC can robustly induce cell traction force changes through acoustic radiation forces and bubble cavitation induced shear stresses. Importantly, ATC stimulations increased the survival rate and cloning efficiency of hESCs by 3-fold, suggesting its potential application in large-scale expansion of hPSCs

Microengineered synthetic cellular microenvironment for stem cells

Stem cells possess the ability of self‐renewal and differentiation into specific cell types. Therefore, stem cells have great potentials in fundamental biology studies and clinical applications. The most urgent desire for stem cell research is to generate appropriate artificial stem cell culture system, which can mimic the dynamic complexity and precise regulation of the in vivo biochemical and biomechanical signals, to regulate and direct stem cell behaviors. Precise control and regulation of the biochemical and biomechanical stimuli to stem cells have been successfully achieved using emerging micro/nanoengineering techniques. This review provides insights into how these micro/nanoengineering approaches, particularly microcontact printing and elastomeric micropost array, are applied to create dynamic and complex environment for stem cells culture. WIREs Nanomed Nanobiotechnol 2012, 4:414–427. doi: 10.1002/wnan.1175 For further resources related to this article, please visit the WIREs website .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92053/1/1175_ftp.pd

Forcing Stem Cells to Behave: Dissecting the Mechanobiology of Human Pluripotent Stem Cells Using Microengineering Approaches.

Stem cells, especially human pluripotent stem cells (hPSCs), hold significant promise for modeling developmental and disease processes, drug and toxicology screening, and cell-based regenerative medicine. Most hPSC studies have so far focused on identifying extrinsic soluble factors, intracellular signaling pathways, and transcriptional regulatory networks involved in regulating hPSC behaviors. This thesis focuses on the development and application of some novel synthetic micromechanical systems to understand the mechano-sensitive and -responsive properties of hPSCs and their functional regulation of self-renewal, directed differentiation, and survival of hPSCs. First, we have demonstrated that rigid PDMS micropost arrays (PMAs, Young’s modulus Eeff = 1MPa) support the maintenance of pluripotency of hPSCs. Blocking cytoskeleton contractility by blebbistatin and inhibiting E-cadherin functions by DECMA-1 antibody both impair mechanoresponsive self-renewal of hPSCs on rigid substrates. We have further achieved efficient neuroepithelial induction, caudalization, and motor neuron differentiation from hPSCs combing soft PMAs (Eeff < 5kPa) with dual Smad inhibition. The purity and yield of functional motor neurons derived from hPSCs within 23 days of culture using soft PMAs were improved four- and twelve-fold, respectively, compared to coverslips or rigid PMAs. Our mechanistic work has helped reveal for the first time that biomechanical cues, including intracellular contractile forces and cell shape, converge and reinforce signal integration of TGF-β, Wnt, Hippo/YAP, Rho GTPase, and the actomyosin cytoskeleton to regulate the neural plate specification. The last part of this thesis focuses on a novel acoustic tweezing cytometry (ATC) utilizing ultrasound pulses to actuate functionalized lipid-encapsulated microbubbles (MBs) targeted to cell surface integrin receptors to exert subcellular mechanical forces in the pN - nN range. ATC can robustly induce cell traction force changes through acoustic radiation forces and bubble cavitation induced shear stresses. Importantly, ATC stimulations increased the survival rate and cloning efficiency of hESCs by 3-fold, suggesting its potential application in large-scale expansion of hPSCs that is critical for future hPSC-based regenerative therapies and disease modeling.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/113638/1/ybsun_1.pd

Generalized parton distributions of Δ\Delta resonance in a diquark spectator approach

The generalized parton distributions (GPDs) for the spin-3/2 $\Delta^+$ resonance are studied numerically by using a diquark spectator approach. Our results show that symmetric constraints from time reversal on GPDs are satisfied. The axial vector form factors of the system are also provided and compared with the lattice QCD calculation. Furthermore, the structure functions are obtained from GPDs in the forward limit. The evolution of structure functions to the scales up to 4 GeV are carried out as predictions for the possible lattice QCD calculations

EFFECTS OF TWO TYPES OF CONTROLLABLE DEFORMATION ON ENERGY EXTRACTION OF A FLEXIBLE HYDROFOIL

Energy extraction capacity of controllably flexible hydrofoil was studied under two identified deformation modes. Deformation modes, flexure parameters (flexure amplitude and flexure coefficient ) and motion parameters (reduced frequency f* and pitching amplitude 0) were investigated to understand the effects of controllably flexible deformation on energy extraction. The results reveal that deformation modes affect the effective angle of attack and vortex structure, which influence hydrodynamic performance. The energy extraction capacity improves from the deformation mode 2 to the rigid hydrofoil and then to the deformation mode 1. Under the deformation mode 1, lift, moment and power coefficients are increased obviously with the increase of , while they increase slightly with . Power coefficients and efficiency are sensitive to , which influences the development of leading-edge vortices. The flexible coefficient affects the wake structure, which has less impact on variation of force coefficient. As the increase in f*, averaged power coefficients firstly increase and then decrease. Further, the optimal f* is subjected to 0. Interestingly, a critical reduced frequency f*s, which is generally increase with increasing 0, was found under three modes. The condition that f* > f*s. is a prerequisite for subsequent adjustments of flexure modes and parameters according to different requirement of power coefficient under different tidal currents. The range of high efficiency () is: deformation mode 1 (36.1% rigid hydrofoils (34.2% deformation mode 2 (26.9%<<30.3%)

Condensation tendency and planar isotropic actin gradient induce radial alignment in confined monolayers

A monolayer of highly motile cells can establish long-range orientational order, which can be explained by hydrodynamic theory of active gels and fluids. However, it is less clear how cell shape changes and rearrangement are governed when the monolayer is in mechanical equilibrium states when cell motility diminishes. In this work, we report that rat embryonic fibroblasts (REF), when confined in circular mesoscale patterns on rigid substrates, can transition from the spindle shapes to more compact morphologies. Cells align radially only at the pattern boundary when they are in the mechanical equilibrium. This radial alignment disappears when cell contractility or cell-cell adhesion is reduced. Unlike monolayers of spindle-like cells such as NIH-3T3 fibroblasts with minimal intercellular interactions or epithelial cells like Madin-Darby canine kidney (MDCK) with strong cortical actin network, confined REF monolayers present an actin gradient with isotropic meshwork, suggesting the existence of a stiffness gradient. In addition, the REF cells tend to condense on soft substrates, a collective cell behavior we refer to as the ‘condensation tendency’. This condensation tendency, together with geometrical confinement, induces tensile prestretch (i.e. an isotropic stretch that causes tissue to contract when released) to the confined monolayer. By developing a Voronoi-cell model, we demonstrate that the combined global tissue prestretch and cell stiffness differential between the inner and boundary cells can sufficiently define the cell radial alignment at the pattern boundary

Intelligent Technology Analysis in Electronic Engineering Automation Control

The reason why human society will develop more and more civilized and intelligent is because human beings are becoming more and more intelligent and their demand for scientific and technological intelligence is increasing. It is precisely because of human’s continuous pursuit of superior artificial intelligence that the improvement and development of China’s electronic engineering automation system has been promoted. Intelligent technology is also gradually applied to the automation system of electronic engineering, which brings great convenience to electric power engineering. The wide application of intelligent technology in electronic automation system is conducive to the improvement of the control level of electric power system in China and the improvement of people’s living standard. This paper mainly analyzes the intelligent technology in the electronic engineering automation control, and narrates its advantages, characteristics, present situation and application for your reference

Biomechanical microenvironment regulates fusogenicity of breast cancer cells

Fusion of cancer cells is thought to contribute to tumor development and drug resistance. The low frequency of cell fusion events and the instability of fused cells have hindered our ability to understand the molecular mechanisms that govern cell fusion. We have demonstrated that several breast cancer cell lines can fuse into multinucleated giant cells in vitro, and the initiation and longevity of fused cells can be regulated solely by biophysical factors. Dynamically tuning the adhesive area of the patterned substrates, reducing cytoskeletal tensions pharmacologically, altering matrix stiffness, and modulating pattern curvature all supported the spontaneous fusion and stability of these multinucleated giant cells. These observations highlight that the biomechanical microenvironment of cancer cells, including the matrix rigidity and interfacial curvature, can directly modulate their fusogenicity, an unexplored mechanism through which biophysical cues regulate tumor progression

Imaging and detecting intercellular tensile forces in spheroids and embryoid bodies using lipid-modified DNA probes

Cells continuously experience and respond to different physical forces that are used to regulate their physiology and functions. Our ability to measure these mechanical cues is essential for understanding the bases of various mechanosensing and mechanotransduction processes. While multiple strategies have been developed to study mechanical forces within two-dimensional (2D) cell culture monolayers, the force measurement at cell-cell junctions in real three-dimensional (3D) cell models is still pretty rare. Considering that in real biological systems, cells are exposed to forces from 3D directions, measuring these molecular forces in their native environment is thus highly critical for the better understanding of different development and disease processes. We have recently developed a type of DNA-based molecular probe for measuring intercellular tensile forces in 2D cell models. Herein, we will report the further development and first-time usage of these molecular tension probes to visualize and detect mechanical forces within 3D spheroids and embryoid bodies (EBs). These probes can spontaneously anchor onto live cell membranes via the attached lipid moieties. By varying the concentrations of these DNA probes and their incubation time, we have first characterized the kinetics and efficiency of probe penetration and loading onto tumor spheroids and stem cell EBs of different sizes. After optimization, we have further imaged and measured E-cadherin-mediated forces in these 3D spheroids and EBs for the first time. Our results indicated that these DNA-based molecular tension probes can be used to study the spatiotemporal distributions of target mechanotransduction processes. These powerful imaging tools may be potentially applied to fill the gap between ongoing research of biomechanics in 2D systems and that in real 3D cell complexes