Contribution of runt-related transcription factor 2 to the pathogenesis of osteoarthritis in mice after induction of knee joint instability

Faculty of Medicine, University of Tokyo, Tokyo, Japan.
Arthritis & Rheumatology (Impact Factor: 7.76). 08/2006; 54(8):2462-70. DOI: 10.1002/art.22041
Source: PubMed


By producing instability in mouse knee joints, we attempted to determine the involvement of runt-related transcription factor 2 (RUNX-2), which is required for chondrocyte hypertrophy, in the development of osteoarthritis (OA).
An experimental mouse OA model was created by surgical transection of the medial collateral ligament and resection of the medial meniscus of the knee joints of heterozygous RUNX-2-deficient (Runx2+/-) mice and wild-type littermates. Cartilage destruction and osteophyte formation in the medial tibial cartilage were compared by histologic and radiographic analyses. Localization of type X collagen and matrix metalloproteinase 13 (MMP-13) was examined by immunohistochemistry. Localization of RUNX-2 was determined by X-Gal staining in heterozygous RUNX-2-deficient mice with the lacZ gene insertion at the Runx2-deletion site (Runx2+/lacZ). Messenger RNA levels of type X collagen, MMP-13, and RUNX-2 were examined by real-time reverse transcriptase-polymerase chain reaction analysis.
RUNX-2 was induced in the articular cartilage of wild-type mice at the early stage of OA, almost simultaneously with type X collagen but earlier than MMP-13. Runx2+/- and Runx2+/lacZ mice showed normal skeletal development and articular cartilage; however, after induction of knee joint instability, they exhibited decreased cartilage destruction and osteophyte formation, along with reduced type X collagen and MMP-13 expression, as compared with wild-type mice.
RUNX-2 contributes to the pathogenesis of OA through chondrocyte hypertrophy and matrix breakdown after the induction of joint instability.

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    • "During endochondral ossification, cartilage degradation is induced by matrix metallopeptidases (MMPs), which are expressed by hypertrophic chondrocytes. Similar to this process, cartilage degradation in OA is mediated by MMPs [14-16]. Our interest in the present study was to evaluate the role of Ihh in OA development by specifically knocking down Ihh in chondrocytes to obtain more direct evidence that Ihh signaling is critical to OA progression. "
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    • "We found that the phenotype markers were remarkably well-conserved in the three models, with only COL6A1 and RUNX2 differentially expressed. The disruption of RUNX2, as seen in the type II collagen hydrogel, has been shown to block chondrocyte hypertrophy and the progression of osteoarthritis [22]. Two commonly used indicators of articular cartilage phenotype, the COL2A1/COL1A1 and COL2A1/COL10A1 ratios, were statistically similar (p > 0.05) in the different chondrogenesis models at all time points. "
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    Full-text · Article · Nov 2013 · PLoS ONE
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    • "In recent years many factors that are able to influence, or correlate with, the development of osteoarthritis have been revealed. These include, but are not limited to, bone morphogenetic proteins (BMPs) [2,3], canonical wingless-type MMTV integration site family members (WNTs) [4,5], Hedgehog [6], interleukins [7,8], parathyroid hormone-related peptide (PTHrP) [9] and the transcription factors HIF2A [10] and RunX2 [11]. Of these factors, BMPs [12], WNT [13], Indian hedgehog (IHH) [14], HIF2A [15] and RunX2 [16] have also been identified as prohypertrophic factors. "
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