A Pre-Clinical Model of Synovitis Using Ex vivo Human Synovial Tissue with Preserved Function and Architecture

Arthritis is an inflammatory state within joints resulting in cartilage damage, pain, and loss of mobility. Recent advances in arthritis research specifically demonstrate that the joint capsule (e.g., synovium) is an important source of this inflammation, but there are no human models that replicate essential synovial architecture. To address this, the Joint Space Analysis System, or JSAS, was created. Anterior synovium was obtained intra-operatively from patients undergoing Total Knee Arthroplasty (TKA). Synovium was dissected and sectioned into 3 mm biopsy cores. Cores were placed in the upper well of a 5 µm or 0.4 µm transwell with 300 µl of DMEM with10% FBS. In the bottom well, 600 µL of media was added, and exchanged every 2-3 days. Viability was assessed up to 7 days in hyperoxic (50%), atmospheric/standard (~21%), and physiologic (5%) incubation conditions. Stimuli in the bottom well included monocyte chemoattractant protein 1 (MCP-1/CCL2), lipopolysaccharide (LPS), N-acetyl cysteine, S. aureus, and B. burgdorferi. Media was stored for ELISA, and tissue was stored for formalin fixed paraffin embedded (FFPE) analysis. In standard conditions, synovium remained fully viable for 3 days. Stimulus modified the structure and function of intimal lining and sublining synovial cells, including loss of the resident macrophage border, sublining expansion, upregulation of pathogenic fibroblasts, and production of cytokines IL-1β and TNFα. Immune cells and fibroblasts migrated to the bottom chamber (5 µm pores) per flow cytometry analysis. Mobile B. burgdorferi migrated into tissue at the 0.4 µm pore size while non-motile S. aureus did not. Relevant cytokines were expressed in sufficient quantity for ELISA. JSAS is a modular system capable of studying acute alterations to human synovium, allowing for the complexity of 3D structures in a pre-clinical model while maintaining biologically relevant structure and function.