For some, this approach may not suffice, and other injectable solutions have been proposed, including the use of platelet-rich-plasma injections. The platelet-rich component is thought to contain numerous growth factors that help heal injuries. The technique has been popularized by its use in star athletes, such as Tiger Woods and Rafael Nadal, although the data demonstrating its efficacy are lacking.6
Do Entheses Hold the Clue to Spondyloarthritis (SpA)?
Over the past decade, nothing in the field of tendon biology has captivated the minds of rheumatologists as much as the enthesis, the intricate fibrocartilaginous structure comprising the bone–tendon interface. Unlike the rest of the tendon, it is rich in type II collagen, produced by chondrocyte-like cells not found in other tendon regions.5 The enthesis has been considered to be a key target in SpA.
A fascinating study in a mouse model of ankylosing spondylitis described the potential role of IL-23 and entheseal-resident T cells in the pathogenesis of SpA.7 Recall that HLA-B27 has a tendency to misfold, and this misfolding results in the production of IL-23. IL-23 is also produced in response to the endoplasmic reticulum stress response that is triggered by Chlamydia trachomatis, a bacterium that is associated with the reactive arthritis subtype of SpA. Taken together, these observations suggest that overproduction of, or heightened sensitivity to, IL-23 may be central to the pathogenesis of SpA.
Various pathways may lead to elevated IL-23 expression, which can activate a previously unidentified population of resident T cells within the enthesis. These activated T cells can then promote local inflammation and bone remodeling through a variety of effector mediators, including IL-17 and IL-22. The net result of these actions is the typical ankylosed appearance of the spine.
In this study, investigators also detected inflammatory changes in the aortic root and valve, which are structurally similar to the entheses and some mice developed psoriatiform skin lesions. Why the enthesis has the potential to serve as a potent site for inflammation, particularly in SpA, remains an enigma. Could IL-23 be the link that binds immunity to our body’s scaffolding?
Why Tendons Matter
Defining the source of musculoskeletal pain is at the heart of what we do as rheumatologists. Patients seek answers and solutions to their ailments. Too often, their complaints of pain, stiffness and soreness are either ignored or lumped together by various practitioners who have a tendency to overuse the moniker, arthritis. Sorry, there’s not much we can do about your arthritis pain, you just have to live with it.
