Background/Purpose: Joint pain is one of the most significant clinical hallmarks of knee osteoarthritis (OA). Knee OA is a chronic degenerative disease of the joints characterized by the breakdown of articular cartilage, changes in the subchondral bone (sclerosis) and synovium (synovitis). Uncovering the mechanisms and circuits underlying pain in knee OA remains a major challenge to finding effective and disease-modifying therapy. The synovium is heavily innervated by sensory nerve terminals potentially enabling communication between synovial fibroblasts (sFBs), the predominant cells of the synovium and knee afferents. The aim of this study is to explore mechanisms by which sFBs communicate with knee afferents and how this communication impacts sensory neuron sensitivity in OA knee joints using a microfluidic coculture system.

Methods: In a pilot and feasibility studies, we pioneered a compartmentalized microfluidic system, in which we integrated human iPSCs-derived sensory neurons (SNs) and human sFBs and tested the effects of various stimuli, known to be released by FBs on neurite outgrowth, activity and pain signaling pathways.

Results: Using a two-compartment microfluidic device, we found that hiPSCs–SNs were able to grow neurites towards sFBs within 7 days, where they form extensive connections with cocultured hsFBs. Real time monitoring of the changes in intracellular calcium levels in hiPSC-SNs cocultured with sFBs revealed a dynamic interplay between neuronal activity and sFBs. For example, we have used this system for targeting specific signaling pathways or receptors such as NGF and MRGPRD and study the effects on neurite growth and sensitivity. Similarly, calcium imaging studies in hsFBs from OA patients revealed that the number of FBs with higher baseline signal was significantly increased compared to sFBs from heathy individuals, indicating altered calcium homeostasis, which can impact various cellular processes, including the release of various factors that can activate nociceptors.

Conclusion: This human relevant platform with hiPSCs and hsFBs can be used to explore mechanisms and accelerate the identification of targets for analgesic therapy in joint pain in various health conditions such as in OA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/modeling-osteoarthritis-knee-joint-in-a-compartmentalized-microfluidic-system-using-ipsc-derived-sensory-neurons-and-human-synovial-fibroblasts/