Interleukin-37 Ameliorates Articular Cartilage Damage in Two Murine Models of Osteoarthritis.

<h3>Background and Objectives</h3> Osteophyte formation is an important hallmark of osteoarthritis (OA) causing limited joint movement and pain. There is increasing belief that synovial activation contributes to OA pathology. As shown recently in our lab, alarmins S100A8 and S100A9 (major products of synovial macrophages) are involved in cartilage degradation and synovial activation during human and murine OA. In the current study, we explored the involvement of S100A8/A9 in osteophyte formation in experimental OA. <h3>Methods</h3> Experimental OA was elicited in C57Bl/6 (WT) mice and S100A9^-/- mice, which also lack functional S100A8. Collagenase induced OA (CIOA) was induced by two times intra-articular injection of 1U collagenase, DMM was induced by transsection of the medial anterior meniscotibial ligament leading to destabilisation of the medial meniscus (DMM). Osteophyte size was assessed by a blind observer using Leica Application Suite (LAS) imaging software. Chondrogenesis was induced by bringing human foetal mesenchymal stem cells (MSCs) in pellet and stimulating for 5 days with BMP-2 and TGFβ1, with or without human recombinant S100A8. Proteoglycan content was quantified using the LAS imaging software on SafO stained sections. <h3>Results</h3> First, we measured osteophyte size in S100A9^-/- mice at day 42 of CIOA. Synovial activation is high in CIOA and this is significantly reduced in S100A9^-/- mice. Osteophyte size was dramatically reduced in the S100A9^-/- compared to WT in the medial collateral ligament (92.5% reduction) but also significantly at the medial side of both tibia and femur (68.2% and 64.6% reduction) (n = 10). One explanation for the reduced osteophyte size in S100A9^-/- mice may be a direct effect of S100-proteins on chondrogenesis. To investigate this, we stimulated MSCs in pellet culture with BMP-2 and TGFβ1, supplemented with 1 and 5 µg/ml S100A8. Proteoglycan deposition as measured by redness in SafO staining was increased 27% and 71% respectively, indicating that S100A8 stimulates chondrogenesis. Finally, we determined osteophyte size in the DMM model, in which synovial involvement is very low. At day 56, we observed no significant differences in osteophyte size between the S100A9^-/- and WT at the medial femur and tibia (105% and 136% of WT, n = 8). This confirms the importance of the synovium in the S100-effect on osteophyte development. <h3>Conclusions</h3> S100A8/S100A9 play a crucial role in osteophyte formation in an OA model that shows clear synovial involvement, probably by stimulating chondrogenesis. Considering also the deleterious effect of S100A8/A9 on joint destruction in OA, targeting these alarmins during OA may be very promising.

The recent paper “Multimodal imaging demonstrates concomitant changes in bone and cartilage after destabilization of the medial meniscus and increased joint laxity”

BackgroundThere is increasing evidence that synovial activation contributes to osteoarthritis (OA) pathology and that it is present in a large subset of OA patients. Previously, we found that alarmins S100A8...

To date, the use of biomarkers for assessing individual severity of osteoarthritis (OA) is limited, and the correlation of histological scores with biomarkers for individual animals in the destabilization of the medial meniscus (DMM) model of OA has not been well investigated. Accordingly, this study investigated how well representative biomarkers in the DMM model reflected specific changes in individual animals. Rats were randomly divided into the OA group and the sham group. OA model was established by destabilization of the medial meniscus (DMM). After 2,4,6,8,10 and 12 weeks (n=14, each week), the concentrations of CTXII, COMP, C2C, and OC in serum were measured, and cartilage degeneration, osteophytes, and synovial membrane inflammation, typical of OA, were scored using Osteoarthritis Research Society International (OARSI) scoring system. Additionally, the correlation between each biomarker and the specific changes in osteoarthritis was analyzed for individual animals using the Generalized Estimating Equation (GEE). Statistical analysis showed a low correlation between CTXII and osteophyte score of the medial femur (coefficient = -0.0088, p= 0.0103), COMP and osteophyte score of the medial tibia (coefficient = -0.0911, p= 0.0003), and C2C and synovial membrane inflammation scores of the medial femoral (coefficient = 0.054, p= 0.0131). These results suggest that representative OA bio- markers in individual animals in the DMM model did not reflect histological scores well.

Osteoarthritis (OA) is a multifactorial disease affecting both the cartilage and the subchondral bone. However, animal models of OA cannot represent both of the changes and show variations depending on induction methods and animal species/strains. This study first investigated subchondral bone changes and its correlation with cartilage degeneration in two different OA models in C57Bl/6 mice. Experimental OA was produced by type II collagenase-induced osteoarthritis (CIOA) and destabilization of the medial meniscus (DMM). The subchondral plate and trabecular bone of the tibia were analyzed by micro-computed tomography and cartilage degeneration was analyzed histologically after safranin-O staining at 2, 4, 6 and 8 weeks. In the DMM model, cartilage degeneration was induced reproducibly and progressively with time. Progressive increase in subchondral bone volume, but not in bone thickness, was also observed in both subchondral bone plate and subchondral trabecular bone in the medial tibial area. The changes in subchondral bone volume correlated well with the histological cartilage degeneration (R2=0.7870). In contrast, in the CIOA model, cartilage degeneration was relatively unstable, increasing only until 4 weeks and decreasing thereafter. No significant changes in subchondral bone were observed in all areas at all time points. These results suggest that the DMM OA mouse model is more reliable and useful than the CIOA model by virtue of its better representation of cartilage degeneration and subchondral bone change with high correlation coefficient.

BackgroundMany osteoarthritis (OA) patients show synovial activation, which is suggested to be involved in joint destruction. Previously, we found strong upregulation of Wnt2b and Wnt16 in the synovium of two...

BackgroundObesity and hyperinsulinemia are of increasing importance in the Western society. Both obesity and insulin resistance lead to changes in expression of adipokines such as adiponectin, visfatin or leptin, which...

IL-6/STAT3 signalling blockade protects against experimental osteoarthritis in mice

Immediate effects of varus bracing on knee mechanics in people with predominant lateral knee osteoarthritis and valgus malalignment, 12 years after anterior cruciate ligament reconstruction

The surgical destabilization of the medial meniscus (DMM) model of osteoarthritis in the 129/SvEv mouse

Cartilage injury regulates nerve growth factor (NGF) in vitro and in vivo and drives painful behaviour in murine OA

TGF-β/Smad2 signaling is considered to be one of the important pathways involved in osteoarthritis (OA) and protein phosphatase magnesium-dependent 1A (PPM1A) functions as an exclusive phosphatase of Smad2 and regulates TGF-β signaling, here, we investigated the functional role of PPM1A in OA pathogenesis.PPM1A expressions in both human OA cartilage and experimental OA mice chondrocytes were analyzed immunohistochemically. Besides, the mRNA and protein expression of PPM1A induced by IL-1β treatment were also detected by q-PCR and immunofluorescence in vitro. OA was induced in PPM1A knockout (KO) mice by destabilization of the medial meniscus (DMM), and histopathological examination was performed. OA was also induced in wild-type (WT) mice, which were then treated with an intra-articular injection of a selective PPM1A inhibitor for 8 weeks.PPM1A protein expressions were increased in both human OA cartilage and experimental OA mice chondrocytes. We also found that treatment with IL-1β in mouse primary chondrocytes significantly increased both mRNA and protein expression of PPM1A in vitro. Importantly, our data showed that PPM1A deletion could substantially protect against surgically induced OA. Concretely, the average OARSI score and quantification of BV/TV of subchondral bone in KO mice were significantly lower than that in WT mice 8 weeks after DMM surgery. Besides, TUNEL staining revealed a significant decrease in apoptotic chondrocytes in PPM1A-KO mice with DMM operation. With OA induction, the rates of chondrocytes positive for Mmp-13 and Adamts-5 in KO mice were also significantly lower than those in WT mice. Moreover, compared with WT mice, the phosphorylation of Smad2 in chondrocytes was increased in KO mice underwent DMM surgery. However, articular-injection with SD-208, a selective inhibitor of TGF-β/Smad2 signaling could significantly abolish the chondroprotective phenotypes in PPM1A-KO mice. Additionally, both cartilage degeneration and subchondral bone subchondral bone sclerosis in DMM model were blunted following intra-articular injection with BC-21, a small-molecule inhibitor for PPM1A.Our study demonstrated that PPM1A inhibition attenuates OA by regulating TGF-β/Smad2 signaling. Furthermore, PPM1A is a potential target for OA treatment and BC-21 may be employed as alternative therapeutic agents for the management of OA.

ObjectiveJoint instability and meniscal dysfunction contribute to the onset and progression of knee osteoarthritis (OA). In the destabilization of the medial meniscus (DMM) model, secondary OA occurs due to the rotational instability and increases compressive stress resulting from the meniscal dysfunction. We created a new controlled abnormal tibial rotation (CATR) model that reduces the rotational instability that occurs in the DMM model. So, we aimed to investigate whether rotational instability affects articular cartilage degeneration using the DMM and CATR models, as confirmed using histology and immunohistochemistry.DesignTwelve-week-old male mice were randomized into 3 groups: DMM group, CATR group, and INTACT group (right knee of the DMM group). After 8 and 12 weeks, we performed the tibial rotational test, safranin-O/fast green staining, and immunohistochemical staining for tumor necrosis factor (TNF)-α and metalloproteinase (MMP)-13.ResultsThe rotational instability in the DMM group was significantly higher than that of the other groups. And articular cartilage degeneration was higher in the DMM group than in the other groups. However, meniscal degeneration was observed in both DMM and CATR groups. The TNF-α and MMP-13 positive cell rates in the articular cartilage of the CATR group were lower than those in the DMM group.ConclusionsWe found that the articular cartilage degeneration was delayed by controlling the rotational instability caused by meniscal dysfunction. These findings suggest that suppression of rotational instability in the knee joint may be an effective therapeutic measure for preventing OA progression.

ObjectivesAlarmins S100A8/A9 regulate pathology in experimental osteoarthritis (OA). Paquinimod is an immunomodulatory compound preventing S100A9 binding to TLR-4. We investigated the effect of paquinimod on experimental OA and human OA...

Objective To investigate the expression of Periostin (Postn) in osteoarthritic cartilage and explore its influence and machanism in cartilage degeneration. Methods C57/BL6 mice were randomly divided into two groups: experimental group and control group, the right knee joints of experimental gruop were underwent destabilization of the medial meniscus (DMM) surgery, while that of control group were only incised skin and joint capsule. Safranin O-fast green and Toluidine Blue staining were used to examinate the change of articular cartilage, and immunohistochemistry staining was used to detect the expression of Postn in articular cartilage. We induced ATDC5 mouse chondrogenic cells to osteoarthritis with interleukin (IL)-1β, and real-time quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) was used to detect the levels of osteoarthritic related factors after silencing Postn gene via small interfering RNA (siRNA) oligo. Results In animal experiments, the thickness of articular cartilage was obviously decreased (DMM 4 w vs. Sham 4 w, P=0.000; DMM 8 w vs. Sham 8 w, P=0.001), International Society for the study of osteoarthritis (OARSI) scoring was obviously increased (DMM 4 w vs. Sham 4 w, P=0.005; DMM 8 w vs. Sham 8 w, P=0.002) and the rates of Postn positive cells were obviously increased in DMM groups compared to Sham groups (DMM 4 w vs. Sham 4 w, P=0.000; DMM 8 w vs. Sham 8 w, P=0.004). In vivo experiment, Postn (1.65±0.23, P=0.008), matrix metalloproteinase-13 (MMP-13, 1.75±0.24, P=0.005), a disintegrin and metalloproteinase with thrombospondin motifs 5 protein (ADAMTS-5, 4.63±1.58, P=0.017), vascular endothelial growth factor (VEGF, 6.24±0.90, P=0.001) and Runt related transcription factor 2 protein (Runx2, 1.54±0.14, P=0.003) were up-regulated in IL-1β+ siScramble group compared to NC group, while no statistics difference was observed in collagen type X, alpha 1 (COL10a1, 1.12±0.12, P=0.161). Postn (0.51±0.17, P=0.002), MMP-13 (0.79±0.09, P=0.003), ADAMTS-5 (0.90±0.11, P=0.015), VEGF (1.04±0.62, P=0.001), Runx2 (0.82±0.14, P=0.003), COL10a1 (0.77±0.11, P=0.020) were differently down-regulated in IL-1β+ siPostn group compared to IL-1β+ siScramble group. Conclusion Postn was elevated in osteoarthritic articular cartilage in DMM model. Silencing Postn gene in ATDC5 chondrogenic cells could attenuate cartilage degeneration. Key words: Osteoarhtitis; Postn; Small interfering RNA; Articular cartilage