In vitro modelling of human proprioceptive sensory neurons in the neuromuscular system.

Proprioceptive sensory neurons (pSN) are an essential and undervalued part of the neuromuscular circuit. A protocol to differentiate healthy and amyotrophic lateral sclerosis (ALS) human neural stem cells (hNSC) into pSN, and their comparison with the motor neuron (MN) differentiation process from the same hNSC sources, facilitated the development of in vitro co-culture platforms. The obtained pSN spheroids cultured interact with human skeletal myocytes showing the formation of annulospiral wrapping-like structures between TrkC + neurons and a multinucleated muscle fibre, presenting synaptic bouton-like structures in the contact point. The comparative analysis of the genetic profile performed in healthy and sporadic ALS hNSC differentiated to pSN suggested that basal levels of ETV1, critical for motor feedback from pSN, were much lower for ALS samples and that the differences between healthy and ALS samples, suggest the involvement of pSN in ALS pathology development and progression.

Will microfluidics enable functionally integrated biohybrid robots?

The next robotics frontier will be led by biohybrids. Capable biohybrid robots require microfluidics to sustain, improve, and scale the architectural complexity of their core ingredient: biological tissues. Advances in microfluidics have already revolutionized disease modeling and drug development, and are positioned to impact regenerative medicine but have yet to apply to biohybrids. Fusing microfluidics with living materials will improve tissue perfusion and maturation, and enable precise patterning of sensing, processing, and control elements. This perspective suggests future developments in advanced biohybrids.

Lectin Staining of Microvascular Glycocalyx in Microfluidic Cancer Cell Extravasation Assays.

The endothelial glycocalyx forms the inner-most lining of human microvasculature. It ensures the physiological function of blood vessels and plays a crucial role in the occurrence and progression of microvascular diseases. The present communication aims to highlight the usefulness of high-resolution imaging of lectin (Bandeiraea Simplicifolia) stained endothelial glycocalyx in 3-dimensional microfluidic cell cultures. The microfluidic system allowed visualizing cancer cell extravasation, which is a key event in metastasis formation in cancer pathologies. In brief, microvascular networks were created through spontaneous vasculogenesis. This occurred from 3 dimensional (3D) suspensions of human umbilical vein endothelial cells (HUVECs) in hydrogels confined within microfluidic devices. Extravasation of MDA-MB-231 breast cancer cells from perfusable endothelial lumens was observed with confocal imaging of lectin-stained microvascular networks. The present work provides guidance towards optimizing the methodology used to elucidate the role of the endothelial glycocalyx during cancer cell extravasation. In particular, a high-resolution view of the endothelial glycocalyx at the site of extravasation is presented. The occurrence of glycocalyx defects is well aligned with the contemporary notion in the field that glycocalyx shedding precedes cancer cell extravasation.

3D Self-Organized Human Blood-Brain Barrier in a Microfluidic Chip.

A preclinical blood-brain barrier (BBB) model is important for the study of fundamental transport mechanisms and in accessing the delivery of small molecules and antibodies that target brain. Transwell assays for BBB models are easy to create and use but lack the true 3D anatomy of the brain microvasculature and also often the cell-cell and cell-matrix interactions that are important in ensuring a tight BBB. Here we describe the formation of a BBB that expresses neurovascular membrane transporters, tight junction, and extracellular matrix proteins using the coculture of human-induced pluripotent stem cell-derived endothelial cells (iPSC-EC), brain pericytes (PC), and astrocytes (AC) in a microfluidic device. The BBB model recapitulates human brain vascular permeability with values that are lower than conventional in vitro models and are comparable to in vivo measurements in rat brain. This in vitro BBB model can therefore be used to screen for brain-targeting drugs or to study neurovascular functions.

Modeling Nanocarrier Transport across a 3D In Vitro Human Blood-Brain-Barrier Microvasculature.

Polymer nanoparticles (NPs), due to their small size and surface functionalization potential have demonstrated effective drug transport across the blood-brain-barrier (BBB). Currently, the lack of in vitro BBB models that closely recapitulate complex human brain microenvironments contributes to high failure rates of neuropharmaceutical clinical trials. In this work, a previously established microfluidic 3D in vitro human BBB model, formed by the self-assembly of human-induced pluripotent stem cell-derived endothelial cells, primary brain pericytes, and astrocytes in triculture within a 3D fibrin hydrogel is exploited to quantify polymer NP permeability, as a function of size and surface chemistry. Microvasculature are perfused with commercially available 100-400 nm fluorescent polystyrene (PS) NPs, and newly synthesized 100 nm rhodamine-labeled polyurethane (PU) NPs. Confocal images are taken at different timepoints and computationally analyzed to quantify fluorescence intensity inside/outside the microvasculature, to determine NP spatial distribution and permeability in 3D. Results show similar permeability of PS and PU NPs, which increases after surface-functionalization with brain-associated ligand holo-transferrin. Compared to conventional transwell models, the method enables rapid analysis of NP permeability in a physiologically relevant human BBB set-up. Therefore, this work demonstrates a new methodology to preclinically assess NP ability to cross the human BBB.

A combined microfluidic-transcriptomic approach to characterize the extravasation potential of cancer cells.

The reciprocal interaction between circulating tumor cells (CTCs) and tissue-specific cells is influential for the progression of metastases. In particular, the process of extravasation relies on the complex cross-talk between cancer cells and other cellular players such as the endothelium and the secondary tissue. However, most in vitro studies only focus on one heterotypic cell-cell interaction and often lack of physiological relevance. In this project, we investigated both CTC-endothelium and CTC-secondary site interactions during cancer cell extravasation. We first used a microarray analysis of extravasated MDA-MB-231 breast cancer cells to identify key markers involved in extravasation. Then, we developed a tri-culture microfluidic platform combining cancer cells, endothelium and a bone-mimicking (BMi) microenvironment to assess how organ tropism influences the extravasation potential of cancer cells from different tissues. Through the microarray analyses of extravasated cancer cells we found that extravasation is associated with upregulation of late-metastatic markers along with specific proteases, such as matrix metalloprotease (MMP), a-disintegrin and metalloprotease (ADAM) and a-disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) family members, which are all involved in endothelium glycocalyx shedding. Through the microfluidic extravasation assay, we found that the bone-like microenvironment increased invasion and motility of breast, bladder and ovarian cancer cell (MDA-MB-231, T24 and OVCAR-3). Among the three cell types, ovarian cancer cells presented the lowest migration rate and bladder cancer cells the highest, hence recapitulating their different level of bone tropism observed in vivo. Taken together, our results shed light on the importance of intercellular communication between CTCs and other non-tumor cells essential for promoting cancer cell extravasation.

Corrigendum: Characterizing the Role of Monocytes in T Cell Cancer Immunotherapy Using a 3D Microfluidic Model.

[This corrects the article DOI: 10.3389/fimmu.2018.00416.].

Characterizing the Role of Monocytes in T Cell Cancer Immunotherapy Using a 3D Microfluidic Model.

In the hepatitis B virus (HBV)-related hepatocellular carcinoma tumor microenvironment (TME), monocytes reportedly impede natural T cell functions via PD-L1/PD-1 signaling. However, it remains unclear if T cell receptor-redirected T cells (TCR T cells) are similarly inhibited. Hence, we developed a 3D intrahepatic TME microfluidic model to investigate the immunosuppressive potential of monocytes toward HBV-specific TCR T cells and the role of PD-L1/PD-1 signaling. Interestingly, in our 3D static microfluidic model, we observed that monocytes suppressed only retrovirally transduced (Tdx) TCR T cell cytotoxicity toward cancer cells via PD-L1/PD-1, while mRNA electroporated (EP) TCR T cell cytotoxicity was not affected by the presence of monocytes. Importantly, when co-cultured in 2D, both Tdx and EP TCR T cell cytotoxicity toward cancer cells were not suppressed by monocytes, suggesting our 3D model as a superior tool compared to standard 2D assays for predicting TCR T cell efficacy in a preclinical setting, which can thus be used to improve current immunotherapy strategies.