Recapitulating monocyte extravasation to the synovium in an organotypic microfluidic model of the articular joint

Carlotta Mondadori,Roberta Visone,Giuseppe Talò,Marco Rasponi,Matteo Moretti,Alberto Redaelli,Shima Salehi,Silvia Palombella,Silvia Lopa,Valerio Sansone

doi:10.1088/1758-5090/ac0c5e

Abstract

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.

Highlights

Osteoarthritis (OA) is the most common type of arthritis and the fastest growing cause of disability worldwide [1, 2]
Synovium and cartilage were modeled by hydrogel-embedded OA synovial fibroblasts and articular chondrocytes separated by a synovial fluid channel
OA synovium can show pathological changes, such as an abnormal infiltration of macrophages [6, 7] that originate from circulating monocytes and sustain inflammatory processes [1, 8, 9]

Summary

Introduction

Osteoarthritis (OA) is the most common type of arthritis and the fastest growing cause of disability worldwide [1, 2]. Articular cartilage has long been considered the only relevant tissue in OA, a more recent approach defines OA as a whole-joint disease [3, 4], recognizing synovial inflammation as an active component of OA [5, 6]. Targeting the excessive recruitment of monocytes to synovium may represent a suitable strategy to prevent the negative effects of macrophage accumulation, as proposed for other diseases [11]. To this aim, a deeper understanding of monocyte extravasation in the context of OA is crucial to identify specific chemokine-signaling axes involved in monocyte recruitment and test molecules antagonizing this event

Objectives

Results

Discussion

Conclusion