Supplementary Material for: Extracellular Matrix Mediates BMP-2 in a Model of Temporomandibular Joint Osteoarthritis

<p>Temporomandibular joint (TMJ) osteoarthritis (OA) is a complex disease that affects both cartilage and subchondral bone. It is accompanied by loss of extracellular matrix (ECM) and may be controlled by bone morphogenetic protein-2 (BMP-2). We analyzed the effect of BMP-2 in both cartilage and subchondral bone in a TMJ-OA animal model that is deficient in biglycan (Bgn) and fibromodulin (Fmod) (<i>Bgn</i><sup><i>-/-</i></sup><i>Fmod</i><sup><i>-/-</i></sup>). Whole mandibles were dissected from 3-week-old wild-type (WT) and <i>Bgn</i><sup><i>-/-</i></sup><i>Fmod</i><sup><i>-/-</i></sup> mice and incubated with and without 250 µg/mL BMP-2 for 2 days using an explant culture system. Condyle growth was measured by microCT and the expression levels of cartilage and bone-related genes were analyzed using RT-PCR or by immunohistochemistry from condyles that contained an intact cartilage/subchondral bone interface. Osteoclast activity was estimated by tartrate-resistant acid phosphatase (TRAP) staining and by <i>TRAP</i>,<i> Rankl</i>, and <i>Adamts4</i> mRNA expression levels. Our results showed that most parameters examined were slightly up-regulated in WT samples treated with BMP-2, and this up-regulation was significantly enhanced in the <i>Bgn</i><sup><i>-/-</i></sup><i>Fmod</i><sup><i>-/-</i></sup> mice. The up-regulation of both catabolic and anabolic agents did not appear to positively affect the overall growth of <i>Bgn</i><sup><i>-/-</i></sup><i>Fmod</i><sup><i>-/-</i></sup> condyles compared to WT controls. In summary, the up-regulation of both anabolic and catabolic genes in the WT and <i>Bgn</i><sup><i>-/-</i></sup><i>Fmod</i><sup><i>-/-</i></sup> TMJs treated with BMP-2 suggests that BMP increases matrix turnover in the condyle, and, further, that Bgn and Fmod could have protective roles in regulating this process.</p>