Is tendinitis an inflammatory disease initiated and driven by pro-inflammatory cytokines such as interleukin 1β?

Tendonitis and tendinitis are terms used to describe an inflamed and painful tendon. Tendinopathy, is a descriptive term for describing clinical conditions arising from tendon injury and overuse both within and around tendons. The aim of this mini-review is to explore the role of pro-inflammatory cytokines, particularly interleukin-1 beta (IL-1 beta) in tendon disorders. A number of investigators including our group have proposed that pro-inflammatory cytokines such as IL-1 beta are initiators of tendinopathies, stimulating inflammation, apoptosis and extracellular matrix (ECM) degradation. This is one of the reasons why IL-1 beta is frequently used in culture models of tendon inflammation to study the inflammatory and catabolic responses of tenocytes. However, some researchers oppose this view and suggest that although IL-1 beta may play a role in rheumatoid arthritis (RA) and osteoarthritis (OA), the involvement of IL-1 beta in the development of tendinopathy is questionable. This mini-review discusses the relevant papers published in this area and summarises the evidence for and against the involvement of pro-inflammatory cytokines such as IL-1 beta in tendonitis. Reaching a consensus will be important for the development and refinement of biomimetic models of tendon inflammation and the formulation of new therapeutic strategies for the treatment of tendon injuries.