ADVERTISEMENT Osteoarthritis (OA) commonly affects horses, yet available therapies have only limited effect on clinical signs and disease progression. In fact, some even block healing mechanisms. Bone-marrow-derived macrophages, a type of white blood cell that produce the anti-inflammatory mediator interleukin-10 (IL-10), however, show promise as a novel OA treatment approach, said Bruno Menarim, DVM, PhD, during his presentation at the 2020 American Association of Equine Practitioners’ Convention, held virtually. Menarim, currently at the University of Kentucky’s Gluck Equine Research Center, in Lexington, reminded his audience that inflammation of the joint’s inner lining, or synovitis, is a hallmark of OA. In the face of acute inflammation, macrophages residing in the joint proliferate and recruit more macrophages from marrow of the long bones nearby to respond to injury. Among other activities, these macrophages (especially the bone marrow macrophages) produce IL-10, resolve joint inflammation, and restore joint homeostasis by helping rebuild damaged tissues.