Statin prevents chondrocyte aging and degeneration of articular cartilage in osteoarthritis (OA)

Abstract

Recent reports have shown that statin (HMG-CoA reductase inhibitors) may have the potential to inhibit inflammatory arthritis. More recently, the idea that chondrocyte aging is closely associated with the progression of cartilage degeneration has been promulgated. Here, we demonstrate the potential of statin as protective agents against chondrocyte aging and degeneration of articular cartilage during the progression of osteoarthritis (OA), both in vitro and in vivo. The OA-related catabolic factor, IL-1β induced marked downregulation of cellular activity, expression of a senescent biomarker, specific senescence-associated β-galactosidase activity and shortening of the cellular lifespan in chondrocytes. In contrast, treatment with statin inhibited the IL-1β-induced production of cartilage matrix degrading .enzymes (metalloprotease-1 and -13) and cellular senescence in of chondrocytes in vitro. In addition, this statin accelerated the production of cartilage matrix proteoglycan in chondrocytes. The in vivo study was performed on the STR/OrtCrlj mouse, an experimental model which spontaneously develops an osteoarthritic process. In this mouse model, treatment with statin significantly reduced the degeneration of articular cartilage, while the control knee joints showed progressive cartilage degeneration over time. These findings suggest that statin may have the potential to prevent the catabolic stress-induced chondrocyte disability and aging observed in articular cartilage. Our results indicate that statin are potential therapeutic agents for protection of articular cartilage against the progression of OA.

Figure 1.. Effect of statn on chondrocyte aging in vitro.

Chondrocyte senescence was measured by the senescence-associated β-galactosidase (SA-β-Gal) activity assay. The chondrocytes were cultured with IL-1β (10 ng/ml) in the presence or absence of statin (1.0, 10.0 μM) for 5 days. (A-F) Representative images of SA-β-Gal staining, (A) control (medium only), (B) IL-1β-treated group, (C) statin (1.0 μM)-treated group, (D) IL-1β + sratin (1.0 μM)-treated group, (E) statin (10.0 μM)-treated group, (F) IL-1β + sratin (10.0 μM)-treated group. As shown in the representative images, whereas IL-1β stimulated the expression of SA-β-Gal in chondrocytes, treatment with statin markedly inhibited the expression of SA-β-Gal even in the presence of IL-1β stimulation. (G) Treatment with statin significantly inhibited the IL-1β-enhanced SA-β-Gal activity in the chondrocytes.

Figure 2.. Effects of statin on the production of matrix degrading enzymes and proteo-glycan in chondrocytes.

Chondrocytes were incubated with catabolic factor, IL-1β (10 ng/ml) in the presence or absence of statin (1.0, 10.0 μM). After 48 hour-incubation, the concentrations of matrix degrading enzymes and proteoglycan were analyzed by ELISA (A: MMP1, B: MMP-3, C: MMP-13, D: proteoglycan). IL-1β stimulated the production of MMP-1, -3, and -13 by chondrocytes in control cultures (* p< 0.05 compared to each control). Statin at 10.0 μM significantly decreased the IL-1β- induced excess production of MMP-1 and -13, but not MMP-3, from chondrocytes (** p< 0.01, compared to IL-1β-stimulated group). IL-1β showed a tendency to decrease the production of proteoglycan by chondrocytes. Statin at 10.0 μM cancelled the IL-1βinduced decreases of proteoglycan production from chondrocytes in both culture conditions (** p< 0.0, compared to IL-1β-stimulated group). Data from four independent experiments were analyzed.

Figure 3.. Representative images of cartilage degeneration in OA model mouse.

(A) At 12 weeks, the cartilage in the control group showed a progression of following cartilage degeneration: chondrocyte clustering, abnormal deposition of chondrocytes, and a decreased cell density with cartilage thinning. The cartilage in the statin-treated mice showed less severe in contrast to the control group. (B) After 24-week treatment, most of the control cartilage showed decrease in thickness, marked loss of proteoglycan, chondrocyte clustering, cell death and severe degeneration of cartilage structure, whereas treatment with statin markedly inhibited the degeneration of articular cartilage in the OA mouse model.

Figure 4.. Therapeutic effect statin in OA mouse model.

Each cartilage sample was evaluated histologically for the degree of degeneration, loss of Safranin-O green staining, chondrocyte loss, cartilage structure, according to a modified Mankin grading system (Table 2). At 12 and 24 weeks, severe damage in articular cartilage was observed in each control joint. Treatment with statin induced a significant reduction of cartilage degeneration in comparison with control (* p< 0.05, ** p< 0.01).