Insights from a novel three-dimensional in vitro model of Lyme arthritis: Standardized analysis of cellular and molecular interactions betweenBorrelia burgdorferi and synovial explants and fibroblasts

Abstract

Objective To develop a novel 3‐dimensional (3‐D) in vitro model of Lyme arthritis to use in the study of the interactions between Borrelia burgdorferi (Bb) and human synovial host cells with respect to phagocytosis and potential persistence of Bb as well as the induction of proinflammatory cytokines and chemokines. Methods Two distinct culture systems, consisting of synovial membrane explants or interactive synovial cells embedded in 3‐D fibrin matrices, were chosen. Both systems were artificially infected with Bb, and the interactions between Bb and synovial tissue/cells were studied by histology, immunohistochemistry, and electron microscopy. Functional analyses included the induction/secretion of cytokines by Bb in the model system. Results Both culture systems proved to be stable and reproducible. The host cells and spirochetes showed high levels of viability and maintained their physiologic shape for >3 weeks. Bb invaded the synovial tissue and the artifical matrix in a time‐dependent manner. Host cells were activated by Bb, as indicated by the induction of interleukin‐1β and tumor necrosis factor α. Electron microscopic analysis revealed Bb intracellularly within macrophages as well as synovial fibroblasts, suggesting that not only professional phagocytes, but also resident synovial cells are capable of phagocytosing Bb. Most interestingly, the uptake of the spirochetes appeared to cause severe damage of the synovial fibroblasts, since the majority of these cells displayed ultrastructural features of disintegration. Conclusion A novel 3‐D in vitro model has been established that allows the study of distinct aspects of Lyme arthritis under conditions that resemble the pathologic condition in humans. This reproducible, standardized model supplements animal studies and conventional 2‐D cultures. The disintegration of synovial fibroblasts containing Bb or Bb fragments challenges the concept of an intracellular persistence of Bb and may instead reflect a mechanism that contributes to the inflammatory processes characteristic of Lyme arthritis.

Evaluation of RevA, a Fibronectin-Binding Protein of Borrelia burgdorferi, as a Potential Vaccine Candidate for Lyme Disease

“…B. burgdorferi is frequently found associated with connective tissues (12,13,14,15) and is often detected in and isolated from infected cartilaginous or membranous tissues, such as skin and joints. This suggests specific interactions between the pathogen and host skin tissues (5,16,17,18).…”

Interaction of a Neurotropic Strain ofBorrelia turicataewith the Cerebral Microcirculation System

“…Spirochetal binding of plasminogen or other host proteases may facilitate this (17,24,38). However, borrelias have also been observed intracellularly in endothelial cells (33) and fibroblasts (20). Examination of the interaction of serotype 1 with BMEC by immunofluorescence showed only extracellular spirochetes.…”

Lyme Arthritis

“…Although it is possible that live spirochetes might be protected from antibiotics and survive in the joint, such as intracellularly in Type 1 or 2 synovial cells, by antigenic drift, or by some immunodeficiency of the host, there is little data to support that this occurs in humans (Fikrig et al, 1995;Girschick et al, 1996;Franz et al, 2001). After appropriate treatment, PCR results for B. burgdorferi DNA become negative in the synovial fluid as well as in synovial tissue samples of patients who underwent synovectomy.…”