Recent research has shown that enhanced focal adhesion between cells and extracellular matrix (ECM) and intracellular actin polymerization can accelerate cellular functions like proliferation and differentiation. It is a desirable and necessary technique to modulate cellular functions in the desired lineage in tissue engineering. Previously, we have shown that topographical effects of micropatterns on a cell culture substrate promoted osteogenic differentiation of mesenchymal stem cells (MSCs) without administration of osteogenic growth factors. In this study, bone marrow mesenchymal stem cells from rats were cultured with combined biophysical stimuli, such as surface topography of biomaterials and uniaxial tensile stress and induced osteogenic differentiation. We evaluated MSCs by assessment of alkaline phosphatase (ALP). We demonstrated that a polydimethylsiloxane substrate with microgroove patterns (2 μm of ridge thickness, 1 μm of depth and 1 μm of groove distance) could suppress osteogenic differentiation compared to a flat substrate. Changes of cell adhesion and shape were observed at microgroove substrates by immunofluorescence staining of focal adhesion and actin filaments. We showed that to apply the stretching force promoted differentiation at microgroove substrates but inhibited differentiation at the flat surface. Through this study, a more efficient method to control cellular fate is expected to be established for tissue regeneration in vitro.

The early-stage of knee osteoarthritis (OA) is usually asymptomatic. However, timely detection of osteoarthritis can prevent further cartilage degeneration via appropriate exercise prescription and behavioral change. In this article, a noninvasive method to diagnose the OA of a knee recording the knee vibroarthrographic (VAG) signals over the mid-patella during the standing movement is proposed. A method that combines empirical mode decomposition (EMD) and wavelet transform is developed to analyze the nonstationary VAG signals. The least squares support vector machine algorithm (LSSVM) that is a type of support vector machine is used to classify the knee joint VAG signals (26 normal and 25 abnormal) collected from healthy subjects and patients suffering from the knee OA using the Kellgren and Lawrence grading system III and IV (KLGS III and IV). The LSSVM classifier achieves an accuracy of 86.67% in differentiating the normal and abnormal subjects that proves the effectiveness of the autocorrelation function features and continuous wavelet transform (CWT) features. Therefore, the VAG signals can be clinically significant for the classification of healthy and OA subjects.

In this paper, we apply an oscillating shear flow to a dilute capsule suspension and report its viscoelastic properties. We analyze the complex viscosity under different capillary numbers and viscosity ratios, which is a viscosity contrast inside and outside the capsules. For all viscosity ratios, the real part of complex viscosity η′ monotonically decreases with the frequency of the applied oscillating shear, while the imaginary part η′′ shows the maximum value at an intermediate frequency. In general, the capsule with a larger viscosity ratio gives larger η′, while that of smaller viscosity ratio gives larger η′′. At high frequencies, the capsule that has higher (lower) inner viscosity contributes to increase (decrease) the viscosity of the solutions. In order to separately discuss the contributions of the membrane elasticity and internal fluid viscosity, we analyse the first term and second term of the particle stress tensor. The first term, which is called elastic stress in this paper, represents particle stress that arises from the capsule deformation. The amplitude of elastic stress is nearly constant at low frequencies, while it is inversely proportional to the applied frequency at high frequencies. The phase of elastic stress shifts from the shear to strain phases when the frequency increases. These tendencies of elastic stress do not depend on the viscosity ratio, and the qualitative trends are the same for all viscosity ratios. The second term, which is called viscous stress in this paper, represents particle stress that arises from the viscosity ratio, and the trend is drastically different by the viscosity ratio. The viscous stress contributes to increase (decrease) the viscosity and decrease (increase) the elasticity, when the capsule inner viscosity is higher (lower). Finally, we evaluate the effect of the capillary number. At low frequencies, both the capillary number and viscosity ratio are important factors for the rheology. On the other hand, the viscosity ratio becomes the only governing factor at high frequencies because the membrane elasticity has a negligible effect.

Osteocyte plays a central role as a commander in the bone to modulate bone remodeling processes. While the osteocyte is known to be differentiated from osteoblasts, understanding in mechanism of the osteocyte differentiation remained still poor. The aim of this study is to elucidate the osteocyte differentiation capability using three-dimensional (3D) cell culture technique. We first fabricated a self-organized spheroid reconstructed by mouse osteoblast-like cells by adjusting the number of subcultured cells in the round-bottom well. Compared to a conventional two-dimensional (2D) monolayer model, the 3D spheroid exerted greater osteocyte gene expressions in vitro within 2 days. As a result of the size-dependent experiment, there might be an appropriate cell-cell and cell-ECM interaction for osteoblast-like cells to induce the osteocytogenesis in the form of 3D spheroid culture. Moreover, the present model showed that the spheroid further exerted the prolonged osteocyte differentiation capability after a long period of incubation, 7 days. In conclusion, we characterized the self-organized osteocytic spheroids reconstructed by osteoblast-like cells and further suggested the potential application of the spheroid as a new in vitro tissue-engineered osteocytic model.