Real-time cellular impedance monitoring and imaging of biological barriers in a dual-flow membrane bioreactor.

The generation of physiologically relevant in-vitro models of biological barriers can play a key role in understanding human diseases and in the development of more predictive methods for assessing toxicity and drug or nutrient absorption. Here, we present an advanced cell culture system able to mimic the dynamic environment of biological barriers while monitoring cell behaviour through real-time impedance measurements and imaging. It consists of a fluidic device with an apical and a basal flow compartment separated by a semi-permeable membrane. The main features of the device are the integration of sensing through transepithelial electrical impedance (TEEI) measurements and transparent windows for optical monitoring within a dual flow system. Caco-2 cells were cultured in the TEEI bioreactor under both flow and static conditions. Although no differences in the expression of peripheral actin and occludin were visible, the cells in dynamic conditions developed higher impedance values at low frequencies, indicative of a higher paracellular electrical impedance with respect to the static cultures. TEEI measurements at high frequency also enabled monitoring monolayer formation, which can be correlated with the observation of an RC behaviour in the impedance spectra. In particular, the cells subject to flow showed accelerated barrier formation and increased vitality with respect to the static controls, again highlighting the importance of dynamic conditions for epithelial cells.

Impaired Neurite Contact Guidance in Ubiquitin Ligase E3a (Ube3a)-Deficient Hippocampal Neurons on Nanostructured Substrates.

Recent discoveries indicate that during neuronal development the signaling processes that regulate extracellular sensing (e.g., adhesion, cytoskeletal dynamics) are important targets for ubiquitination-dependent regulation, in particular through E3 ubiquitin ligases. Among these, Ubiquitin E3a ligase (UBE3A) has a key role in brain functioning, but its function and how its deficiency results in the neurodevelopmental disorder Angelman syndrome is still unclear. Here, the role of UBE3A is investigated in neurite contact guidance during neuronal development, in vitro. The microtopography sensing of wild-type and Ube3a-deficient hippocampal neurons is studied by exploiting gratings with different topographical characteristics, with the aim to compare their capabilities to read and follow physical directional stimuli. It is shown that neuronal contact guidance is defective in Ube3a-deficient neurons, and this behavior is linked to an impaired activation of the focal adhesion signaling pathway. Taken together, the results suggest that the neuronal contact sensing machinery might be affected in Angelman syndrome.

Sub-micron lateral topography affects endothelial migration by modulation of focal adhesion dynamics.

Through the interaction with topographical features, endothelial cells tune their ability to populate target substrates, both in vivo and in vitro. Basal textures interfere with the establishment and maturation of focal adhesions (FAs) thus inducing specific cell-polarization patterns and regulating a plethora of cell activities that govern the overall endothelial function. In this study, we analyze the effect of topographical features on FAs in primary human endothelial cells. Reported data demonstrate a functional link between FA dynamics and cell polarization and spreading on structured substrates presenting variable lateral feature size. Our results reveal that gratings with 2 µm lateral periodicity maximize contact guidance. The effect is linked to the dynamical state of FAs. We argue that these results are readily applicable to the rational design of active surfaces at the interface with the blood stream.

Wharton's Jelly human mesenchymal stem cell contact guidance by noisy nanotopographies.

The development of biomaterials ensuring proper cell adhesion, polarization, migration and differentiation represents a true enabler for successful tissue-engineering applications. Surface nanostructuring was suggested as a promising method for improving cell-substrate interaction. Here, we study Wharton's Jelly human Mesenchymal Stem Cells (WJ-hMSC) interacting with nanogratings (NGs) having a controlled amount of nanotopographical noise (nTN). Our data demonstrate that unperturbed NGs induce cell polarization, alignment and migration along NG lines. The introduction of nTN dramatically modifies this behavior and leads to a marked loss of cell polarization and directional migration, even at low noise levels. High-resolution focal adhesions (FAs) imaging showed that this behavior is caused by the release of the geometrical vinculum imposed by the NGs to FA shaping and maturation. We argue that highly anisotropic nanopatterned scaffolds can be successfully exploited to drive stem cell migration in regenerative medicine protocols and discuss the impact of scaffold alterations or wear.