SAT0055 Simulating the pathogenesis of arthritis in vitro by developing a human-based multicomponent 3d joint model

Background Our ultimate goal is to develop a valid human in vitro 3D joint model to simulate the pathogenesis of arthritis. The in vitro 3D joint model consists of different components including an1 osteogenic and2 chondrogenic part,3 the synovial fluid and4 the synovial membrane and contains all involved cell types and thus, to allow interactions between cells by cell contacts and signalling molecules. As an alternative experimental setup for animal models, our in vitro 3D joint model will enable us to study the influence and efficacy of drug treatment. Currently, there is no valid 3D model which is able to mimic an arthritic joint. Objectives Here, we aim to mimic the1 osteogenic and2 chondrogenic part,3 the joint space with synovial fluid and4 the synovial membrane. Methods For the osteogenic component of the 3D joint model, we populated β-tricalcium phosphate (TCP) – mimicking the mineral bony part – with osteogenic pre-differentiated human bone marrow-derived mesenchymal stromal cells (hMSC) and coated the particles with an hMSC monolayer cell-sheet to get a compact bony component. Survival, adhesion and structural integrity of the cells were evaluated by Scanning Electron Microscopy (SEM), LIVE/DEAD staining and cellular release of LDH. Osteogenic differentiation was analysed by µCT for mineralization and on gene expression level using qRT-PCR. To mimic the chondrogenic part, a scaffold-free 3D cartilage construct was generated by chondrogenic differentiation of hMSC under hypoxia with intermittent mechanical stimulation. Constructs were analysed by histology and qRT-PCR. Simulating the synovial fluid, hyaluronic acid was applied to the osteochondral model. To model the synovial membrane, a confluent monolayer of hMSC was formed on a polycarbonate membrane and visualised by hemacolor staining. Results We developed an in vitro 3D bone model by successfully seeding pre-differentiated hMSC on a β-TCP scaffold. Cells consistently adhere onto the scaffold for up to 3 weeks as observed by SEM. The analysis of cell viability via LDH detection and LIVE/DEAD staining showed no toxic effects on the cells even after 3 weeks of incubation as compared to the corresponding control. mRNA expression of bone-related genes such as RUNX2, SPP1 and COL1A1 as well as µCT analysis confirmed the osteogenic phenotypic of hMSC grown in 3D. Mimicking the articular cartilage component, we verified its chondrogenic phenotype by HE and Alcian Blue staining as well as by the reduced mRNA expression of COL1A1 and an abundant expression of COL2A1. Interestingly, co-cultivation of the osteogenic and chondrogenic part for up to 3 weeks demonstrated successful colonisation, connectivity and initial calcification implying a functional transitional bridging area. Modelling the synovial membrane, we successfully and reproducibly created a confluent monolayer of hMSC, which is easily transferable to the model. Conclusions First steps towards the in vitro simulation of an arthritic joint based on a multi-component model confirm good cell vitality and phenotypic stability which indicates successful progression. To finalise the development of healthy joint model, we will combine the established parts to provide a suitable 3D multi-component joint model which enables us to study the efficacy of drug treatment in vitro. Disclosure of Interest None declared