Hypergravity-induced multicellular spheroid generation with different morphological patterns precisely controlled on a centrifugal microfluidic platform.

In living tissue, cells exist in three-dimensional (3D) microenvironments with intricate cell-cell interactions. To model these cellular environments, numerous techniques for generating cell spheroids have been proposed and improved. However, previously reported methods still have limitations in uniformity, reproducibility, scalability, throughput, etc. Here, we present a centrifugal microfluidic-based spheroid (CMS) formation method for generating both co-culture and mono-culture 3D spheroids in a highly controlled manner. We designed circularly arrayed microwells to allow the even distribution of cells introduced at the center of a rotating platform and to provide identical hypergravity conditions at each well by the centrifugal forces generated. Compared with conventional well plate-based spheroid formation, the CMS formation method significantly promotes sphericity and consistency in both size and shape with high production yields. In addition to mono-culture spheroids, we successfully generated co-culture spheroids in concentric, Janus, and sandwich shapes using human adipose-derived stem cells and human lung fibroblasts, demonstrating the versatility of our CMS formation method. We believe that our new method for generating 3D spheroids will become one of the essential technologies in the field of 3D cell culture. We also expect that we are providing an innovative means to assess cellular responses, including cell motility under different hypergravity conditions.

Concomitant differentiation of a population of mouse embryonic stem cells into neuron-like cells and schwann cell-like cells in a slow-flow microfluidic device.

BACKGROUND: To send meaningful information to the brain, an inner ear cochlear implant (CI) must become closely coupled to as large and healthy a population of remaining spiral ganglion neurons (SGN) as possible. Inner ear gangliogenesis depends on macrophage migration inhibitory factor (MIF), a directionally attractant neurotrophic cytokine made by both Schwann and supporting cells (Bank et al., 2012). MIF-induced mouse embryonic stem cell (mESC)-derived "neurons" could potentially substitute for lost or damaged SGN. mESC-derived "Schwann cells" produce MIF, as do all Schwann cells (Huang et al., a; Roth et al., 2007; Roth et al., 2008) and could attract SGN to a "cell-coated" implant. RESULTS: Neuron- and Schwann cell-like cells were produced from a common population of mESCs in an ultra-slow-flow microfluidic device. As the populations interacted, "neurons" grew over the "Schwann cell" lawn, and early events in myelination were documented. Blocking MIF on the Schwann cell side greatly reduced directional neurite outgrowth. MIF-expressing "Schwann cells" were used to coat a CI: Mouse SGN and MIF-induced "neurons" grew directionally to the CI and to a wild-type but not MIF-knockout organ of Corti explant. CONCLUSIONS: Two novel stem cell-based approaches for treating the problem of sensorineural hearing loss are described. Developmental Dynamics 246:7-27, 2017. © 2016 Wiley Periodicals, Inc.

Estimation of saline-mixed tissue conductivity and ablation lesion size.

In radiofrequency ablation (RFA), saline infusion is beneficial for enhancing electrical conductivity, which allows more energy dissipation into target tissue, resulting in increased lesion size. Computational simulation has been a popular method to estimate lesion size from RFA treatment, but it has not been used effectively for saline-infused RFA, for lack of methods to address the conductivity properties of saline-tissue mixtures. To fill this gap, we propose a microscopic mixture model to derive the effective temperature-dependent conductivities of a saline-tissue mixture. We modeled a small block of 6% hypertonic saline-infused liver tissue as a 1 × 1 × 1 cm cube, which was divided into 64-1000 elements, with each element representing either liver tissue or saline. A 1:1 mixing of saline and liver tissue was assumed to calculate the effective conductivities at 30, 50, 70, and 90°C. Different mixing conditions (2:1 and 1:2 of saline to liver tissue) were also tested to observe the effect of mixing ratio on the resulting data. Then, the derived conductivities were applied for 3D hypertonic saline-infused RFA simulation. The results matched our previous experimental measurements within 13%. The proposed model is customizable in constructing mixtures of multiple components, and can thus be expanded to include the effects of various anatomical microstructures and materials.

Pseudo-organ boundary conditions applied to a computational fluid dynamics model of the human aorta.

In three-dimensional numerical studies of the aorta, it is difficult to apply proper boundary conditions at the end of each major aortic branch because of interactions between blood and organs. Organs and body parts were assumed to be likened to cylindrically shaped porous media, so-called pseudo-organs, and treated in the computational domain as forms of hemodynamic resistance. Permeability functions were determined from two-dimensional axisymmetric computations of each aortic branch and these functions were then used in an unsteady three-dimensional simulation of the complete aorta. Substantially accurate cardiac output (5.91 L/min) and blood distributions to the major branches were predicted.