The NAD-Dependent Deacetylase Sirtuin-1 Regulates the Expression of Osteogenic Transcriptional Activator Runt-Related Transcription Factor 2 (Runx2) and Production of Matrix Metalloproteinase (MMP)-13 in Chondrocytes in Osteoarthritis

Abstract

Aging is one of the major pathologic factors associated with osteoarthritis (OA). Recently, numerous reports have demonstrated the impact of sirtuin-1 (Sirt1), which is the NAD-dependent deacetylase, on human aging. It has been demonstrated that Sirt1 induces osteogenic and chondrogenic differentiation of mesenchymal stem cells. However, the role of Sirt1 in the OA chondrocytes still remains unknown. We postulated that Sirt1 regulates a hypertrophic chondrocyte lineage and degeneration of articular cartilage through the activation of osteogenic transcriptional activator Runx2 and matrix metalloproteinase (MMP)-13 in OA chondrocytes. To verify whether sirtuin-1 (Sirt1) regulates chondrocyte activity in OA, we studied expressions of Sirt1, Runx2 and production of MMP-13, and their associations in human OA chondrocytes. The expression of Sirt1 was ubiquitously observed in osteoarthritic chondrocytes; in contrast, Runx2 expressed in the osteophyte region in patients with OA and OA model mice. OA relating catabolic factor IL-1βincreased the expression of Runx2 in OA chondrocytes. OA chondrocytes, which were pretreated with Sirt1 inhibitor, inhibited the IL-1β-induced expression of Runx2 compared to the control. Since the Runx2 is a promotor of MMP-13 expression, Sirt1 inactivation may inhibit the Runx2 expression and the resultant down-regulation of MMP-13 production in chondrocytes. Our findings suggest thatSirt1 may regulate the expression of Runx2, which is the osteogenic transcription factor, and the production of MMP-13 from chondrocytes in OA. Since Sirt1 activity is known to be affected by several stresses, including inflammation and oxidative stress, as well as aging, SIRT may be involved in the development of OA.

The Nicotinamide Adenine Dinucleotide (NAD)-Dependent Deacetylase Sirtuin-1 Regulates Chondrocyte Energy Metabolism through the Modulation of Adenosine Monophosphate-Activated Protein Kinase (AMPK) in Osteoarthritis(OA)

“…These findings indicate that Sirt-1 activity, which is downregulated by several cellular stresses, may directly influence the expression of Runx2 in chondrocytes, affecting the enzymatic degeneration of articular cartilage and osteophyte formation in OA. We concluded that Sirt-1-regulated-Runx2 expression could control the production of MMP-13 and osteophyte formation by OA chondrocytes [18]. We postulate that Sirt1 activity in chondrocytes could be an important contributing factor in the pathogenesis and pathophysiology of OA.…”

“…Articular cartilage explants were cut into small pieces, washed with phosphate-buffered saline (PBS) and digested with 1.5 mg/mL collagenase B (Sigma, St. Louis, MO, USA) in Dulbecco's modified Eagle's medium (DMEM) (Sigma) overnight on a shaking platform at 37°C. Isolated chondrocytes were collected following centrifugation, washed three times with PBS, resuspended and cultured in DMEM supplemented with 10% heat-inactivated foetal calf serum (FCS), 2 mM L-glutamine, 25 mM HEPES (2[4-(2-hydroxyethyl)-1-piperazinyl] ethane sulfonic acid), and 100 U/mL penicillin and streptomycin at 37°C in a humidified atmosphere of 95% air and 5% CO 2 as previously reported [18]. …”

“…In addition, Runx2 is known to promote activation of the cartilage-degrading enzyme MMP-13 in chondrocytes [32]. Interestingly, our previous study demonstrated that Sirt-1 inactivation inhibited both Runx2 expression and the IL-1β-accelerated production of MMP-13 in chondrocytes [18]. These findings indicate that Sirt-1 activity, which is downregulated by several cellular stresses, may directly influence the expression of Runx2 in chondrocytes, affecting the enzymatic degeneration of articular cartilage and osteophyte formation in OA.…”

“…We and other groups have already demonstrated that sirtuin-1 (Sirt-1) has a functional role and is a key regulator of many molecules in both catabolic and anabolic pathways in OA chondrocytes [18][19][20][21][22][23]. Sirt-1 has been reported to participate in stress responses by regulating cell death and cellular metabolism through the deacetylation of target proteins in chondrocytes [19,20,22].…”

“…More recently, we have demonstrated that Sirt-1 regulates the expression of the osteogenic transcription factor Runt-related transcription factor 2 (Runx2) and production of the cartilage matrixdegrading enzyme, matrix metalloproteinase (MMP)-13, in osteoarthritic chondrocytes [18]. It is well known that MMP-13 contributes to OA cartilage degradation [3][4][5].…”