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The dysregulation of the immune system plays a crucial role in the pathogenesis of manyfold diseases, among which we find rheumatoid arthritis (RA), an autoimmune disease characterized by chronic inflammation in synovial joints, leading to pain and disability. Immune cells such as pro-inflammatory macrophages and T helper 1 (Th1) cells drive the inflammatory cascade. Thus, including immune system in in vitro models is pivotal to recapitulate and better understand the complex interactions between these immune cell subsets and their secreted mediators. Here, a compartmentalized microfluidic platform is presented, for precise confinement of circulating immune cells in organs-on-chip. The integration of innovative normally-closed sieving valves allows, through minimal waste of biological material, to co-culture different immune cell types (e.g. macrophages and Th1). Moreover, the platform allows to stimulate cell subsets separately, and to assess their cross-talk at desired time points. Functional validation of the platform demonstrates its ability to create stable chemotactic gradients, allowing for induction and evaluation of Th1 cells migration. In a proof-of-concept study, the platform allowed to assess Th1 T cells migration towards pro-inflammatory macrophages, thus replicating a characteristic interaction among immune cells triggered during RA onset. These results thus support the suitability of the platform to study immune cells cross-talk and migration phenomena, being potentially applicable to a manyfold immune cell mechanisms, both involved in RA progression and in different immune-mediated pathologies., (Creative Commons Attribution license.)

The synovium of osteoarthritis (OA) patients can be characterized by an abnormal accumulation of macrophages originating from extravasated monocytes. Since targeting monocyte extravasation may represent a promising therapeutic strategy, our aim was to develop an organotypic microfluidic model recapitulating this process. Synovium and cartilage were modeled by hydrogel-embedded OA synovial fibroblasts and articular chondrocytes separated by a synovial fluid channel. The synovium compartment included a perfusable endothelialized channel dedicated to monocyte injection. Monocyte extravasation in response to chemokines and OA synovial fluid was quantified. The efficacy of chemokine receptor antagonists, RS-504393 (CCR2 antagonist) and Cenicriviroc (CCR2/CCR5 antagonist) in inhibiting extravasation was tested pre-incubating monocytes with the antagonists before injection. After designing and fabricating the chip, culture conditions were optimized to achieve an organotypic model including synovial fibroblasts, articular chondrocytes, and a continuous endothelial monolayer expressing intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. A significantly higher number of monocytes extravasated in response to the chemokine mix ( p < 0.01) and OA synovial fluid ( p < 0.01), compared to a control condition. In both cases, endothelium pre-activation enhanced monocyte extravasation. The simultaneous blocking of CCR2 and CCR5 proved to be more effective ( p < 0.001) in inhibiting monocyte extravasation in response to OA synovial fluid than blocking of CCR2 only ( p < 0.01). The study of extravasation in the model provided direct evidence that OA synovial fluid induces monocytes to cross the endothelium and invade the synovial compartment. The model can be exploited either to test molecules antagonizing this process or to investigate the effect of extravasated monocytes on synovium and cartilage cells., (Creative Commons Attribution license.)

Cardiac toxicity still represents a common adverse outcome causing drug attrition and post-marketing withdrawal. The development of relevant in vitro models resembling the human heart recently opened the path towards a more accurate detection of drug-induced human cardiac toxicity early in the drug development process. Organs-on-chip have been proposed as promising tools to recapitulate in vitro the key aspects of the in vivo cardiac physiology and to provide a means to directly analyze functional readouts. In this scenario, a new device capable of continuous monitoring of electrophysiological signals from functional in vitro human hearts-on-chip is here presented. The development of cardiac microtissues was achieved through a recently published method to control the mechanical environment, while the introduction of a technology consisting in micro-electrode coaxial guides allowed to conduct direct and non-destructive electrophysiology studies. The generated human cardiac microtissues exhibited synchronous spontaneous beating, as demonstrated by multi-point and continuous acquisition of cardiac field potential, and expression of relevant genes encoding for cardiac ion-channels. A proof-of-concept pharmacological validation on three drugs proved the proposed model to potentially be a powerful tool to evaluate functional cardiac toxicity., (Creative Commons Attribution license.)