A standardized protocol for the isolation and culture of normal and arthritogenic murine synovial fibroblasts

Rheumatoid arthritis (RA) is a chronic inflammatory disease affecting mainly the synovial joints. The chronic phase of disease is characterized by the hyperproliferation of synovial tissue and formation of pannus, resulting in the progressive erosion of cartilage and bone tissue and leading to disability. Despite the uncertainties on the autoimmune versus autoinflammatory nature of RA, the requirement of non-immune cell function such as synovial fibroblasts (SFs) in the loss of tissue integrity has been widely accepted (1). SFs are CD45-negative cells of mesenchymal origin involved in supporting and lubricating the joint by providing nutrients and proteoglycans (2). Interestingly, it was shown that human RA-SFs are activated and contribute to hyperplasia and destruction (3) and mixed populations of human synoviocytes when implanted into Severe Combined Immuno-Deficiency (SCID) mice retain their ability to destroy cartilage in the absence of a functioning immune system (4). Indeed, cells from arthritic joints in culture show increased invasiveness, matrix degradation and increased cell adhesion (5).