Allograft adipose matrix increases interleukin-10 and transforming growth factor-β1 concentrations in impinged fat pads of the knee

Background: Fat pads of the knee both help the patella smoothly track during knee flexion and protect the patella through release of anti-inflammatory, anabolic cytokines, growth factors, and stem cells.When impingement of fat pads occurs, pro-inflammatory adipokines, lipids, cytokines, and chemokines are released, worsening osteoarthritis (OA).Treatments that help restore fat pad volume may delay OA progression.Allograft adipose matrix (AAM) is an J o u r n a l P r e -p r o o f acellular, inert matrix that retains collagens and various growth factors promoting cellular infiltration and restore volume of native adipose tissue that could potentially be used in treatment of fat pad impingement.We sought to determine effects AAM on gene expression and protein concentrations in osteoarthritic tissues and cells. Methods:The cartilage and fat pads were collected from 20 patients undergoing total knee arthroplasty.The tissues were used to create explants or digested to isolate the chondrocytes and adipocytes for cell culture.Explants and cells were then cultured in media containing AAM.After 48 hours, the tissues and cells were measured for extracellular matrix (ECM), metalloproteinase (MMP), and adipokine gene expression and for MMP, inflammatory cytokine, and growth factor concentrations.Results: IL-10 concentrations were increased in fat pad explants, while concentrations of the growth factor TGF-1 were increased in fat pad/cartilage explant co-cultures.TGF-1 concentrations were decreased in adipocyte/chondrocyte co-cultures.ECM, MMP, and adipokine gene expression was unaltered, but TIMP-2 expression was significantly downregulated.MMP-3 and -13 concentrations were also unaffected.Conclusions: AAM increases IL-10 and TGF-1 in osteoarthritic adipocytes and chondrocytes isolated from the knee joint.