Subchondral cyst development and MMP-1 expression during progression of osteoarthritis: an immunohistochemical study

Relationship between DXA measured systemic bone mineral density and subchondral bone cysts in postmenopausal female patients with knee osteoarthritis: a cross-sectional study : Osteoarthritis cysts and bone mineral density

BACKGROUND

Individuals with high systemic bone mineral density (BMD) may have an increased risk of incident knee osteoarthritis (OA). Besides that, radiographic osteophytes are strongly associated with BMD. Because of these reasons, the aim of the study was to investigate the possible association between radiological subchondral bone cyst (SBC) grade and systemic BMD and vitamin D status in the postmenopausal female patients with knee OA in a crosss-sectional study.

METHODS

This study included of 48 osteoporosis treatment-free postmenopausal patients diagnosed with symptomatic medial compartment knee OA. BMD analysis was performed using dual-energy X-ray absorptiometry (DXA) and serum vitamin D levels were measured after recording patients' findings. Each knee was scanned using computed tomography (CT), and categorical SBC scores were graded for the medial and lateral tibiofemoral (TF) and patellofemoral (PF) compartments and further calculated as compartmental total, total TF and grand total of both TF compartments. SBC scores were analysed with correlation analysis.

RESULTS

The patient population was characterized by radiographic joint space narrowing, obesity and low vitamin D status. Median medial total and grand total TF SBC scores were significantly different between the patient groups according to the Kellgren-Lawrence (KL) radiographic grading (p = 0.006 and p = 0.007, respectively). There were no correlations between femoral BMD values and SBC scores. However, positive correlations were detected significantly between L1 - 4 DXA values and TF SBC scores, but not with PF SBC scores (p = 0.005 for the correlation between L1 - 4 BMD and medial compartments total TF SBC score, p = 0.021 for the correlation between L1 - 4 BMD and grand total TF SBC score). No significant correlations were found with Vitamin D levels.

CONCLUSIONS

Development of TF OA high-grade SBCs may be linked to systemic bone mass as represented by trabecular bone-rich lumbar vertebrae. The relationship might point to the importance of bone stiffness as an acting factor in knee OA possibly with mechanical energy transfer to the joint.

Subchondral Bone Cyst Development in Osteoarthritis: From Pathophysiology to Bone Microarchitecture Changes and Clinical Implementations

Osteoarthritis is a degenerative joint disease affecting middle-aged and elderly patients. It mainly involves weight-bearing joints such as the hip, knee and spine as well as the basilar joint of the thumb, causing dysfunction and painful symptoms. Often, joint arthritis is accompanied by cartilage defects, joint space narrowing, osteophytes, bone sclerosis and subchondral bone cysts (SBC). The aim of the present study was to explore the pathophysiology responsible for the development of SBCs as well as the association between SBCs and disease progress, the level of clinical symptoms and their impact on postoperative outcomes and risk of possible complications following joint replacements if left untreated. A literature review on PubMed articles was conducted to retrieve and evaluate all available evidence related to the main objective mentioned above. A few theories have been put forth to explain the formation process of SBCs. These involve MMPs secretion, angiogenesis, and enhanced bone turnover as a biological response to abnormal mechanical loads causing repeated injuries on cartilage and subchondral tissue during the development of arthritis. However, the application of novel therapeutics, celecoxib-coated microspheres, local administration of IGF-1 and activated chondrocytes following surgical debridement of SBCs hinders the expansion of SBCs and prevents the progression of osteoarthritis.

Structural features of subchondral bone cysts and adjacent tissues in hip osteoarthritis

OBJECTIVE

Focal lesions within the subchondral bone, termed subchondral bone cysts (SBCs), are clinically accepted radiographic markers of advanced osteoarthritis (OA), but their etiology in the hip is not well understood.

DESIGN

This study used micro-computed tomography (μCT), and histological and immunocytological analysis to examine the prevalence, size, location, and morphological and cellular features of SBCs found within 34 femoral heads (14 male, 20 female; age range = 43-80 years) obtained from total hip arthroplasty procedures.

RESULTS

SBCs were common-present in 91% of the femoral heads examined-and frequently commuted with the surface of the femoral head, but otherwise showed no preferred anatomical location. Few associations were found between SBC features and patient characteristics such as BMI, age and sex. SBCs were also heterogenous in composition, ranging from fibrous (most common) to predominantly fatty (least common) and often containing vasculature, nerve fibers, cartilage islands, and bony spicules. Despite this heterogeneity, focal abnormalities in bone density and cartilage thickness were consistently observed. Bone adjacent to SBCs was denser than that in the primary compressive group, and cartilage thickness in regions overlying SBCs was lower than in non-overlying regions. In contrast to these local bony changes, μCT-based finite element analyses indicated that the stiffness of the primary compressive group was only mildly affected by SBCs.

CONCLUSIONS

These findings indicate that SBCs in the femoral head involve extensive perturbations in cellular activity, culminating in myriad skeletal tissue types and spatially heterogenous changes in bone and cartilage morphology that are likely to affect OA progression.

Strategy to Estimate Sample Sizes to Justify the Association between MMP1 SNP and Osteoarthritis

Background: the impact of knee osteoarthritis (OA) poses a formidable challenge to older adults. Studies have reported that genetic factors, such as MMP1, are one of important risk factors for knee OA. Although the relationship between the genetic polymorphism of MMP1 rs1799750 and the risk of knee OA has been explored, conclusions have been nonunanimous and pending due to research sample sizes, one of determinants in studying genetic polymorphisms associated with disease. Objective: to establish a model to assess whether the genetic polymorphism of MMP1 rs1799750 is associated with knee OA based on an estimation of sample sizes. Methods: samples were collected from a case−control and meta-analysis study. In the case−control study, patients who underwent knee X-ray examinations based on the Kellgren−Lawrence Grading System (KL) as diagnostic criteria were recruited at the Health Examination Center of the Tri-Service General Hospital from 2015 to 2019. Gene sequencing was conducted using iPLEX Gold. Those with unsuccessful gene sequencing were excluded. Finally, there were 569 patients in the knee OA group (KL ≥ 2) and 534 participants in the control group (KL < 2). In the meta-analysis, we used the databases PubMed, EMBASE, and Cochrane to search for studies on the relationship between MMP1 rs1799750 and knee OA. Next, we adopted the trial sequential analysis (TSA) method to assess whether sample sizes were sufficient or not to determine the risk of the genetic polymorphism of MMP1 rs1799750 on knee OA in Caucasians and Asians. Results: in Caucasians, the MMP1 rs1799750 was not significantly associated with knee OA with an odds ratios (OR) of 1.10 (95% confidence interval, CI: 0.45−2.68). Some extra 8559 samples were needed to conclude this relationship in Caucasians by the TSA model. In Asians, neither our case−control study results (n = 1103) nor a combination of samples from the case−control and meta-analysis results showed an association between MMP1 rs1799750 and knee OA. The OR (95% CI) was 1.10 (0.81−1.49) in a combination of Asian samples. Some extra 5517 samples were needed to justify this relationship in Asians by the TSA model. Conclusions: this research shows that an extra 8559 and 5517 samples are needed in Caucasians and Asians, respectively, in order to justify the association between MMP1 rs1799750 and knee OA.

Sex, but not age and bone mass index positively impact on the development of osteochondral micro‐defects and the accompanying cellular alterations during osteoarthritis progression

Background

Osteoarthritis (ΟΑ) is characterized by cartilage breakdown and subchondral sclerosis. Micro‐fractures of the calcified tissues have been, also, detected, but their exact role has not been elucidated yet. This study was to examine the frequency of cracks during OA progression and to correlate them with the underlying cellular modifications and matrix metalloproteinase‐2 (MMP‐2) expression using histological/immunohistological methods.

Methods

Overall, 20 patients and 3 controls (9 specimens per patient), aged 60–89 years, diagnosed with hip/knee OA were included. The development of cracks was examined in 138 sections, whereas the expression of MMP‐2 was examined in 69 additional sections.

Results

Based on Mankin score, three groups of OA severity were analyzed: Group I (mild) was constituted of sections with score 1–5 while Groups II (moderate) and III (severe) with score 6–7 and greater or equal to 8, respectively. Demographic characteristics did not reveal any association between the number of microdefects and age or body mass index (BMI). Cartilage micro‐cracks were increased during moderate and severe OA, while bone cracks were increased during mild and severe OA. In knee OA, cartilage cracks were not correlated with Mankin score, whereas in hip OA they appeared association with severity score. Bone cracks were positively correlated with matrix apoptotic osteocytes and osteoblastic cells, but not with osteoclasts. MMP‐2 immunostaining was increasing by OA severity in the osteochondral unit. Similarly, MMP‐2 was expressed on the microcracks’ wall mainly in Group III.

Conclusion

Our data displayed that bone cracks during primary OA stages, represent an early adaptative mechanism aiming to maintain cartilage integrity. Accumulation of bone defects and concomitant increase of apoptotic osteocytes activated an abnormal remodeling due to osteoblastic activity, in which MMP‐2 played a pivotal role, leading to subchondral sclerosis promoting further osteochondral deformities.

Magnetic Resonance Imaging-Assessed Subchondral Cysts and Incident Knee Pain and Knee Osteoarthritis: Data From the Multicenter Osteoarthritis Study

OBJECTIVE

To examine whether knee subchondral cysts, measured on magnetic resonance imaging (MRI), are associated with incident knee osteoarthritis (OA) outcomes.

METHODS

We used longitudinal data from the Multicenter Osteoarthritis Study, a community-based cohort of subjects with risk factors for knee OA. Participants without a history of knee surgery and/or inflammatory arthritis (i.e., rheumatoid arthritis and gout) were followed up for 84 months for the following incident outcomes: 1) radiographic knee OA (Kellgren/Lawrence grade ≥2), 2) symptomatic radiographic knee OA (radiographic knee OA and frequent knee pain), and 3) frequent knee pain (with or without radiographic knee OA). In a subset of participants, subchondral cysts were scored on baseline MRIs of 1 knee. Multiple logistic regression, with adjustment for participant characteristics and other baseline knee MRI findings, was used to assess whether subchondral cysts were predictive of incident outcomes.

RESULTS

Among the participants with knees eligible for analyses of outcomes over 84 months, incident radiographic knee OA occurred in 22.8% of knees with no baseline radiographic knee OA, symptomatic radiographic knee OA occurred in 17.0% of knees with no baseline symptomatic radiographic knee OA, and frequent knee pain (with or without radiographic knee OA) occurred in 28.8% of knees with no baseline radiographic knee OA and 43.7% of knees with baseline radiographic knee OA. With adjustment for age, sex, and body mass index, the presence of subchondral cysts was not associated with incident radiographic knee OA but was associated with increased odds of incident symptomatic radiographic knee OA (odds ratio 1.92 [95% confidence interval 1.16-3.19]) and increased odds of incident frequent knee pain in those who had radiographic knee OA at baseline (odds ratio 2.11 [95% confidence interval 0.87-5.12]). Stronger and significant associations were observed for outcomes based on consistent reports of frequent knee pain within ~1 month of the study visit.

CONCLUSION

Subchondral cysts are likely to be a secondary phenomenon, rather than a primary trigger, of radiographic knee OA, and may predict symptoms in knees with existing disease.

Association of Matrix Metalloproteinase (MMP) Gene Polymorphisms With Knee Osteoarthritis: A Review of the Literature

Progressive matrix metalloproteinase (MMP)-induced degradation of the extracellular matrix (ECM) of the articular cartilage is one of the major pathogenic osteoarthritis (OA) events. Several single nucleotide polymorphisms (SNPs) in genes encoding MMPs have been identified as affecting MMP expression, production, and enzymatic activity. This study systematically reviews the literature regarding the association between the SNPs of genes encoding MMPs and the risk of knee OA. An electronic search in the PubMed and Web of Science databases from conception to January 2021 was performed addressing studies relating MMPs genetic polymorphisms with the risk of knee OA. We included case-control studies that used validated genotyping methods to detect the SNPs’ association in MMP genes with primary knee OA risk. Ten studies were finally included in this systematic review, evaluating different SNPs in six MMP genes in terms of knee OA pathogenesis: MMP-1 (3 SNPs), MMP-2 (1 SNP), MMP-3 (9 SNPs), MMP-8 (10 SNPs), MMP-9 (6 SNPs), and MMP-13 (1 SNP). Among them, nine SNPs of four MMP genes have been associated with knee OA: (a) MMP-1 -1607 1G/2G (Turkish, Chinese), (b) MMP-3 rs650108, rs650108, rs520540, rs602128, rs679620 (Chinese), (c) MMP-8 rs1940475 and rs376520 (Finnish), and (d) MMP-13 77A/ (rs2252070) (Chinese). The present review summarizes all known SNPs of MMP genes related to a higher risk of knee OA. There are at least nine SNPs in four MMP genes associated with knee OA. No solid correlation between MMP genotype and knee OA phenotype exists. More high-quality studies and modern genetic testing methods are needed to fully elucidate the role of polymorphisms of MMP genes in knee OA pathogenesis.

Bleeding with iron deposition and vascular remodelling in subchondral cysts: A newly discovered feature unique to haemophilic arthropathy

INTRODUCTION

Joint iron accumulation is the incendiary factor triggering osteochondral destruction, synovial hypertrophy, inflammation, and vascular remodelling in haemophilic arthropathy (HA). Hemosiderin depositions have been described in synovium and, more recently, in cartilage. Clinical observations also suggest hemosiderin accumulation in subchondral cysts, implying cyst bleeding.

AIM

We explored associations between cystic iron accumulation, vascular remodelling and HA status to determine if cystic bleeding may contribute to HA progression.

METHODS

Thirty-six haemophilic joints (16 knees, 10 ankles, and 10 elbows; 31 adult patients with haemophilia A/B) were evaluated by magnetic resonance imaging (MRI) for subchondral cysts and hemosiderin. Cyst score (WORMS) and hemosiderin presence were compared between haemophilic and osteoarthritic knees, matched for the degree of arthritis (Kellgren-Lawrence score). Cystic iron accumulation, vascular remodelling and macrophage cell counts were also compared by immunohistochemistry in explanted joint tissues. In haemophilic knees, cyst number and extent of hemosiderin deposition were correlated with haemophilia joint health scores (HJHS).

RESULTS

Cystic hemosiderin was detected in 78% of haemophilic joints. Cyst score and presence of hemosiderin were significantly higher in haemophilic compared to osteoarthritic knees. Cyst score and presence of hemosiderin strongly correlated with HJHS. Moreover, iron deposition and vascular remodelling were significantly more pronounced within cysts in haemophilic compared to osteoarthritic knees, with similar total cell and macrophage count.

CONCLUSION

These findings suggest the presence of subchondral bleeding in haemophilia, contributing to poor joint health outcomes. Observations of bleeding into osseous structures are novel and should inform investigations of new therapies.

Association between the MMP-1-1607 1G/2G Polymorphism and Osteoarthritis Risk: A Systematic Review and Meta-Analysis

Background

Osteoarthritis (OA) is a common disease characterized by articular cartilage degeneration and secondary hyperosteogenesis. Genetic factors are associated with the occurrence of OA. While several studies have shown that the matrix metalloproteinase-1- (MMP-1-) 1607 1G/2G (rs1799750) polymorphism may be related to the occurrence and development of OA, there is inconsistency in the literature. To better estimate the relationship between the MMP-1 gene polymorphism and OA, a comprehensive meta-analysis of relevant literature was carried out.

Results

In total, seven studies comprising 1245 OA patients and 1230 controls were included in this meta-analysis. The combined results revealed no significant association between the MMP-1-1607 1G/2G polymorphism and risk of OA in the five genetic models. However, after Bonferroni correction, the results of subgroup analysis revealed a significant correlation between the MMP-1-1607 1G/2G polymorphism and OA susceptibility in the temporomandibular joint (TMJ) OA subgroup (allelic: 2G vs. 1G: OR = 1.575, 95%CI = 1.259–1.972, P < 0.01; recessive: 2G2G vs. 1G1G+1G2G: OR = 2.411, 95%CI = 1.658–3.504, P < 0.01; and homozygote: 2G2G vs. 1G1G: OR = 2.313, 95%CI = 1.341, 3.991, P = 0.003), the younger subgroup (aged less than 60 years; allelic: 2G vs. 1G: OR = 1.635, 95%CI = 1.354, 1.974, P < 0.01; dominant: 2G1G+2G2G vs. 1G1G: OR = 1.622, 95%CI = 1.158, 2.271, P = 0.005; recessive: 2G2G vs. 1G1G+1G2G: OR = 2.209, 95%CI = 1.718, 2.840, P < 0.01; and homozygote: 2G2G vs. 1G1G: OR = 2.578, 95%CI = 1.798, 3.696, P < 0.01), the larger subgroup (N > 300), and the hospital-based case-control study (HCC) subgroup. The sensitivity analysis suggested that the results of the meta-analysis were stable and reliable. Begg's funnel plot and Egger's test indicated that there was no publication bias in this study.

Conclusion

Our meta-analysis indicated that although the MMP-1-1607 1G/2G polymorphism was not significantly associated with OA susceptibility among the whole sample, it played a key role in the etiology and development of TMJ OA and OA in people aged less than 60 years.

Expression profile of matrix metalloproteinases in the labrum of femoroacetabular impingement

Aims

Femoroacetabular impingement (FAI) is a potential cause of hip osteoarthritis (OA). The purpose of this study was to investigate the expression profile of matrix metalloproteinases (MMPs) in the labral tissue with FAI pathology.

Methods

In this study, labral tissues were collected from four FAI patients arthroscopically and from three normal hips of deceased donors. Proteins extracted from the FAI and normal labrums were separately applied for MMP array to screen the expression of seven MMPs and three tissue inhibitors of metalloproteinases (TIMPs). The expression of individual MMPs and TIMPs was quantified by densitometry and compared between the FAI and normal labral groups. The expression of selected MMPs and TIMPs was validated and localized in the labrum with immunohistochemistry.

Results

On MMP arrays, most of the targeted MMPs and TIMPs were detected in the FAI and normal labral proteins. After data normalization, in comparison with the normal labral proteins, expression of MMP-1 and MMP-2 in the FAI group was increased and expression of TIMP-1 reduced. The histology of the FAI labrum showed disorderly cell distribution and altered composition of thick and thin collagen fibres. The labral cells expressing MMP-1 and MMP-2 were localized and their percentages were increased in the FAI labrum. Immunohistochemistry confirmed that the percentage of TIMP-1 positive cells was reduced in the FAI labrum.

Conclusion

This study established an expression profile of MMPs and TIMPs in the FAI labrum. The increased expression of MMP-1 and MMP-2 and reduced expression of TIMP-1 in the FAI labrum are indicative of a pathogenic role of FAI in hip OA development.

Cite this article:Bone Joint Res. 2020;9(4):173–181.

Leonurine Exerts Anti-Catabolic and Anti-Apoptotic Effects via Nuclear Factor kappa B (NF-κB) and Mitogen-Activated Protein Kinase (MAPK) Signaling Pathways in Chondrocytes

Background

Leonurine confers neuroprotection, inhibits myocardial apoptosis, ameliorates endothelial dysfunction, and shows anti-inflammatory effects, and may be beneficial for clinical applications. However, the effects of leonurine on chondrocytes remain unknown. Here, we investigated the protective role of leonurine in rat chondrocytes.

Material/Methods

To explore the potential therapeutic effect of leonurine against osteoarthritis (OA), rat chondrocytes were treated with IL-1β along with different concentrations of leonurine in vitro. The levels of matrix metalloproteinases (MMPs), ADAMTS, Bax, and Bcl-2 were measured by PCR, ELISA, and Western blotting. Caspase-3 activity in chondrocytes was determined using a caspase-3 activity assay. Western blotting was also performed to examine activation of the NF-κB and mitogen-activated protein kinase (MAPK) pathways to elucidate the likely regulatory mechanisms.

Results

Leonurine counteracted IL-1β-induced production of MMP-1, MMP-13, ADAMTS-4, and ADAMTS-5. Leonurine treatment reduced both the mRNA and protein levels of Bax and increased the level of Bcl-2. Leonurine also inhibited the activity of caspase-3 in IL-1β-induced chondrocytes. Furthermore, the activation of MAPK and phosphorylation of p65 were suppressed by leonurine.

Conclusions

The results of this study indicate that leonurine exerts anti-catabolic and anti-apoptotic effects in chondrocytes in vitro via suppression of the NF-κB and MAPK signaling pathways.

Effects of MMP-1 1G/2G polymorphism on osteoarthritis: A meta-analysis study

Objective

The aim of this meta-analysis was to clarify the role of Matrix metalloproteinase 1 (MMP-1) -1607 1G/2G (rs1799750) polymorphism on the osteoarthritis (OA) risk.

Methods

Articles were selected by retrieving the Web of Science, Embase and Pubmed. The strength of the association between -1607 1G/2G polymorphism and OA risk was assessed by odds ratios (ORs) with the corresponding 95% confidence interval (CI) for each study.

Results

No significant association between -1607 1G/2G polymorphism and OA risk was found in all the models overall (2G2G vs 1G1G, OR (95%CI) = 0.69 (0.36–1.32), P = 0.54; 2G2G + 2G1G vs 1G1G, OR (95%CI) = 0.88 (0.47–1.63), P = 0.69; 2G2G vs 2G1G + 1G1G, OR (95%CI) = 1.30 (0.68–2.47), P = 0.41; 2 G vs 1G, OR (95%CI) = 0.90 (0.86–1.54), P = 0.66). By subgroup analysis, significant association was found in the “< 60 years” group (2G2G vs 1G1G, OR (95%CI) = 3.46 (2.13–5.62), P = 0.00; 2G2G + 2G1G vs 1G1G, OR (95%CI) = 0.49 (0.31–0.79), P = 0.00; 2G2G vs 2G1G + 1G1G, OR (95%CI) = 2.74 (1.80–4.16, P = 0.00; 2 G vs 1G, OR (95%CI) = 0.56 (0.35–0.89), P = 0.01).

Conclusions

This meta-analysis showed that -1607 1G/2G polymorphism may increase the susceptibility to OA among the younger populations (<60 years). More studies with detailed information are needed to validate our conclusion.

Level of Evidence

Level I Diagnostic Study.

Mechanistic insight into hyaluronic acid and platelet-rich plasma-mediated anti-inflammatory and anti-apoptotic activities in osteoarthritic mice

Osteoarthritis (OA) poses a major clinical challenges owing to limited regenerative ability of diseased or traumatized chondrocytes in articular cartilage. Previous studies have determined the individual therapeutic efficacies of hyaluronic acid (HA) and platelet-rich plasma (PRP) on OA; however, the underlying mechanism is still lacking. Therefore, we investigated mechanistic approach of HA+PRP therapy on chondrocyte apoptosis in IL-1β+TNF-α (I+T) treated in vitro OA model, in addition to in vivo anterior cruciate ligament transection-OA mice model. MTT assay showed an enhanced chondrocyte proliferation and viability in HA+PRP-treated group, compared to I+T, I+T/HA, I+T/PRP, I+T/HA+PRP groups. Further, HA+PRP also significantly suppressed ROS, apoptotic cleaved caspase-3 and PARP, p53 and p21 and MMP-1; whereas, cell cycle modulatory proteins including p-ERK, cyclin B1, D1, and E2 were upregulated. The sub-G1 population and TUNEL assay confirmed the higher abundance of healthy chondrocytes in HA+PRP group. A significantly decreased ARS staining in HA+PRP group was also noted, indicating reduced cartilaginous matrix mineralization compared to other groups. Conclusively, compared to HA or PRP, the combined HA+PRP might be a promising therapy for articular cartilage regeneration in osteoarthritic pathology, possibly via augmented anti-inflammatory, anti-oxidative chondrocyte proliferation and inhibited MMP-1 activity and matrix calcification.

The association between MMP-1 gene rs1799750 polymorphism and knee osteoarthritis risk

Matrix metalloproteinase 1 (MMP-1) degrades cartilage, which may result in osteoarthritis (OA) development. Several studies have explored the association between MMP-1 gene rs1799750 polymorphism and OA in different populations. However, the results are inconsistent. The aim of this case–control study was to investigate the association between MMP-1 gene rs1799750 polymorphism and knee OA in a Chinese population. The present study included 308 cases and 404 controls. Genotyping was performed using standard polymerase chain reaction and restriction fragment length polymorphism. The present study found that 2G2G genotype (2G2G vs 1G1G: OR & 95% CI, 2.28 (1.47–3.53), P<0.001; 2G2G + 1G2G vs 1G1G: OR & 95% CI, 1.61 (1.15–2.24), P=0.005; 2G2G vs 1G2G + 1G1G: OR & 95% CI, 1.84 (1.26–2.68), P=0.002) or 2G allele carriers (2G vs 1G: OR & 95% CI, 1.48 (1.20–1.83), P<0.001) of MMP-1 gene rs1799750 polymorphism increased the risk of OA. In conclusion, this case–control study confirms that MMP-1 gene rs1799750 polymorphism increases the risk of knee OA in Chinese Han population.

Vertebral Endplate Cyst as a Predictor of Nonunion After Lumbar Interbody Fusion: Comparison of Titanium and Polyetheretherketone Cages

STUDY DESIGN

The bone union rate after lumbar interbody fusion (LIF) using titanium (Ti) or polyetheretherketone (PEEK) cages was investigated retrospectively.

OBJECTIVE

To assess whether the PEEK cage is superior to the Ti cage in terms of bone union after LIF.

SUMMARY OF BACKGROUND DATA

We previously reported that the formation of vertebral endplate cysts is useful for predicting nonunion after LIF using Ti cages.

METHODS

We examined 144 levels in 117 patients treated from March 2005 to July 2012 with transforaminal LIF using Ti (93 levels in 77 patients) or PEEK cages (51 levels in 40 patients) with pedicle screw fixation. Using computed tomography, vertebral endplate cyst (cyst sign) was evaluated at 3 months, and bone union status was evaluated at 1 and 2 years postoperatively. The relationship between cyst sign and union status was analyzed statistically. The bone union rate and the accuracy of the cyst sign were compared between the two groups.

RESULTS

The postoperative bone union rate was 75.2% and 74.5% at 1 year, and 82.8% and 80.4% at 2 years for Ti and PEEK groups, respectively. The rate of positive cyst sign was 17.2% and 13.7%, respectively. The nonunion rate with positive cyst sign was 100% and 100% at 1 year, and 56.2% and 71.4% at 2 years, respectively. Calculated for the cyst sign and union status, the sensitivity was 69.6% and 53.8%, and the specificity was 100% and 100%, respectively. There were no significant differences in bone union rate, rate of positive cyst sign, nonunion rate with positive cyst sign, sensitivity, and specificity between the two groups.

CONCLUSION

The cyst sign was useful for predicting nonunion after LIF using PEEK or Ti cages. The bone union rate after LIF did not differ significantly between the two groups.

LEVEL OF EVIDENCE

3.

Recent advances in the understanding of molecular mechanisms of cartilage degeneration, synovitis and subchondral bone changes in osteoarthritis

Osteoarthritis (OA), the most common form of degenerative joint disease, is linked to high morbidity. It is predicted to be the single greatest cause of disability in the general population by 2030. The development of disease-modifying therapy for OA currently face great obstacle mainly because the onset and development of the disease involve complex molecular mechanisms. In this review, we will comprehensively summarize biological and pathological mechanisms of three key aspects: degeneration of articular cartilage, synovial immunopathogenesis, and changes in subchondral bone. For each tissue, we will focus on the molecular receptors, cytokines, peptidases, related cell, and signal pathways. Agents that specifically block mechanisms involved in synovial inflammation, degeneration of articular cartilage, and subchondral bone remodeling can potentially be exploited to produce targeted therapy for OA. Such new comprehensive agents will benefit affected patients and bring exciting new hope for the treatment of OA.

Pyrroloquinoline Quinone Slows Down the Progression of Osteoarthritis by Inhibiting Nitric Oxide Production and Metalloproteinase Synthesis

Osteoarthritis (OA) is the most common arthritis and also one of the major causes of joint pain in elderly people. The aim of this study was to investigate the effects of pyrroloquinoline quinone (PQQ) on degenerated-related changes in osteoarthritis (OA). SW1353 cells were stimulated with IL-1β to establish the chondrocyte injury model in vitro. PQQ was administrated into SW1353 cultures 1 h before IL-1β treatment. Amounts of MMP-1, MMP-13, P65, IκBα, ERK, p-ERK, P38, and p-P38 were measured via western blot. The production of NO was determined by Griess reaction assay and reflected by the iNOS level. Meniscal-ligamentous injury (MLI) was performed on 8-week-old rats to establish the OA rat model. PQQ was injected intraperitoneally 3 days before MLI and consecutively until harvest, and the arthritis cartilage degeneration level was assessed. The expressions of MMP-1 and MMP-13 were significantly downregulated after PQQ treatment compared with that in IL-1β alone group. NO production and iNOS expression were decreased by PQQ treatment compared with control group. Amounts of nucleus P65 were upregulated in SW1353 after stimulated with IL-1β, while PQQ significantly inhibited the translocation. In rat OA model, treatment with PQQ markedly decelerated the degeneration of articular cartilage. These findings suggested that PQQ could inhibit OA-related catabolic proteins MMPs expression, NO production, and thus, slow down the articular cartilage degeneration and OA progression. Owing to its beneficial effects, PQQ is expected to be a novel pharmacological application in OA clinical prevention and treatment in the near future.

Histone deacetylase inhibition activates Nrf2 and protects against osteoarthritis

Introduction

Osteoarthritis (OA) is a common joint disease that can cause gradual disability among the aging population. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a key transcription factor that regulates the expression of phase II antioxidant enzymes that provide protection against oxidative stress and tissue damage. The use of histone deacetylase inhibitors (HDACi) has emerged as a potential therapeutic strategy for various diseases. They have displayed chondroprotective effects in various animal models of arthritis. Previous studies have established that Nrf2 acetylation enhances Nrf2 functions. Here we explore the role of Nrf2 in the development of OA and the involvement of Nrf2 acetylation in HDACi protection of OA.

Methods

Two OA models—monosodium iodoacetate (MIA) articular injection and destabilization of the medial meniscus (DMM)—were used with wild-type (WT) and Nrf2-knockout (Nrf2-KO) mice to demonstrate the role of Nrf2 in OA progression. A pan-HDACi, trichostatin A (TSA), was administered to examine the effectiveness of HDACi on protection from cartilage damage. The histological sections were scored. The expression of OA-associated matrix metalloproteinases (MMPs) 1, 3, and 13 and proinflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 were assayed. The effectiveness of HDACi on OA protection was compared between WT and Nrf2-KO mice.

Results

Nrf2-KO mice displayed more severe cartilage damage in both the MIA and DMM models. TSA promoted the induction of Nrf2 downstream proteins in SW1353 chondrosarcoma cells and in mouse joint tissues. TSA also reduced the expression of OA-associated proteins MMP1, MMP3, and MMP13 and proinflammatory cytokines TNF-α, IL-1β, and IL-6. TSA markedly reduced the cartilage damage in both OA models but offered no significant protection in Nrf2-KO mice.

Conclusions

Nrf2 has a major chondroprotective role in progression of OA and is a critical molecule in HDACi-mediated OA protection.

Macrophage-specific metalloelastase (MMP-12) immunoexpression in the osteochondral unit in osteoarthritis correlates with BMI and disease severity

BACKGROUND

Metalloproteinase 12 (MMP-12) is induced in chondrocytes during fetal development and malignant transformation.

OBJECTIVES

The aim of our study is to examine the expression of MMP-12 in the cartilage and the subchondral bone of patients with osteoarthritis (OA) and to correlate its expression with disease severity and anthropometric characteristics.

METHODS

Overall, 60 sections from 20 patients with idiopathic OA, were examined for the immunolocalization of MMP-12. As controls, we used the femoral heads of 4 patients treated with seniarthroplasty after fracture. Demographic characteristics and Body Mass Index (BMI) were calculated for all subjects.

RESULTS

Specimens were divided into four groups based on the Mankin histological severity score. The immunohistochemical study showed MMP-12 expression in the cartilage and subchonral bone of OA patients, while there was no expression in normal controls. At the moderate OA changes (Mankin score: 6-7), MMP-12 was detected mainly at the matrix of fibrocartilage tissue. During disease progression, MMP-12 was expressed at the sides of the cartilage and bone erosion and in the bone cysts. Furthermore, it was traced in the osteocytes of the subchondral bone. Osteoblast-like cells and bone lining cells express MMP-12 during the stage of severe OA (Mankin: ≥8). Osteoclasts expressing MMP-12 were also detected in the group of severe OA. Interestingly, MMP-12 expression was positively correlated with the age and the BMI of OA patients.

CONCLUSION

The increased expression of MMP-12 in the bone-cartilage unit of OA patients suggests a possible role in OA pathogenesis and progression.

LEVEL OF EVIDENCE

III, prospective comparative study.

The role of cyclooxygenase-2, interleukin-1β and fibroblast growth factor-2 in the activation of matrix metalloproteinase-1 in sheared-chondrocytes and articular cartilage

MMP-1 expression is detected in fluid shear stress (20 dyn/cm²)-activated and osteoarthritic human chondrocytes, however, the precise mechanisms underlying shear-induced MMP-1 synthesis remain unknown. Using primary chondrocytes and T/C-28a2 chondrocytic cells as model systems, we report that prolonged application of high fluid shear to human chondrocytes induced the synthesis of cyclooxygenase-2 (COX-2), interleukin-1β (IL-1β) and fibroblast growth factor-2 (FGF-2), which led to a marked increase in MMP-1 expression. IL-1β, COX-2-dependent PGE₂ activated the PI3-K/AKT and p38 signaling pathways, which were in turn responsible for MMP-1 synthesis via NF-κB- and c-Jun-transactivating pathways. Prolonged shear stress exposure (>12 h) induced 15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) synthesis. Although 15d-PGJ₂ suppressed PI3-K/AKT and p38 signaling pathways, it stimulated MMP-1 expression via activating heme oxygenase 1 (HO-1). The critical role of COX-2 in regulating MMP-1 expression in articular cartilage in vivo was demonstrated using COX-2^+/− transgenic mice in the absence or presence of rofecoxib oral administration. These findings provide novel insights for developing therapeutic strategies to combat OA.

Histopathological features of hypertrophic bone mass of temporomandibular joint ankylosis (TMJA): An explanation of pathogenesis of TMJA

Temporomandibular joint ankylosis (TMJA) is a severe organic disease with progressive limitation of the mouth opening. Histopathologically, a residual joint space is reported to consist of fibrous tissue and/or cartilage, indicating two types of interface (osteo-fibrous and osteo-chondral) of residual joint space. It is well known that adverse mechanical stress results in pathological changes of osteoarthritis and enthesopathy in these interfaces. What would happen pathologically in these interfaces of TMJA under repeated mandible movement has not been elucidated. Fourteen tissue samples of residual joint space and temporal and condylar bone were stained with hematoxylin and eosin and evaluated by collagen I and II immunohistochemistry. A pathological study of 14 TMJA patients showed that the residual joint space presented a fibrocartilage entheses structure and an articular cartilage structure. Moreover, these two structures were associated with pathological alterations of both osteoarthritis and enthesopathy, including degenerated and necrotized tissue, chondrocyte cloning, crack and fissure, various bone scleroses, and inflammatory granulation tissue. It is suggested that the pathological alterations of both osteoarthritis and enthesopathy occurred in TMJA, which hints at mechanical stress on TMJA development.

Association of MMP-1 -1607 1G/2G (rs1799750) polymorphism with primary knee osteoarthritis in the Greek population

Osteoarthritis is the most common form of arthritis with still unknown pathogenic etiology and considerable contribution of genetic factors. One of the mechanisms of cartilage degradation in osteoarthritis is enzymatic proteolysis of the extracellular matrix by metalloproteinases. MMP-1, produced by chondrocytes and synovial cells, is a major proteinase of the MMPs family. The present study aims at evaluating the association of MMP1 gene -1607 1G/2G (rs1799750) polymorphism with primary knee osteoarthritis in the Greek population. One hundred fifty five patients with primary symptomatic knee osteoarthritis participated in the study along with 139 controls. Genotypes were determined using PCR-RLFP technique. Allelic and genotypic frequencies were compared between both study groups. There was no significant association between MMP1 -1607 1G/2G polymorphism and knee osteoarthritis, in crude analysis; however, after multiple logistic regression analysis, 1G/2G was associated with reduced odds of knee osteoarthritis by 75% in males, compared to genotypes 1G/1G + 2G/2G, adjusting for age and BMI (adjusted OR: 0.25, 95% CI: 0.069, 0.910, p = 0.035). The present study shows that MMP1 -1607 1G/2G (rs1799750) polymorphism might be a risk factor for knee osteoarthritis susceptibility in the Greek population. Further investigations are needed to confirm this association in the pathogenesis of osteoarthritis.

Destabilization of the medial meniscus leads to subchondral bone defects and site-specific cartilage degeneration in an experimental rat model

OBJECTIVE

This study aimed to investigate subchondral bone changes using micro-computed tomography (micro-CT) and regional differences in articular cartilage degeneration, focusing on changes of cartilage covered by menisci, in the early phase using a destabilization of the medial meniscus (DMM) model.

METHOD

The DMM model was created as an experimental rat osteoarthritis (OA) model (12 weeks old; n = 24). At 1, 2, and 4 weeks after surgery, the rats were sacrificed, and knee joints were scanned using a Micro-CT system. Histological sections of the medial tibial plateau, which was divided into inner, middle, and outer regions, were prepared and scored using the modified OARSI scoring system. The cartilage thickness was also calculated, and matrix metalloproteinase 13 (MMP13), Col2-3/4c, and vascular endothelial growth factor (VEGF) expression was assessed immunohistochemically.

RESULTS

Subchondral bone defects were observed in the middle region, in which the cartilage thickness decreased over time after surgery, and these defects were filled with MMP13- and VEGF-expressing fibrous tissue. The OARSI score increased over time in the middle region, and the score was significantly higher in the middle region than in the inner and outer regions at 1, 2, and 4 weeks after surgery. Col2-3/4c and MMP13 expression was observed primarily in the meniscus-covered outer region, in which the cartilage thickness increased over time.

CONCLUSION

Loss of meniscal function caused cartilage degeneration and subchondral bone defects in the early phase site-specifically in the middle region. Furthermore, our results might indicate cartilage covered by menisci is easily degraded resulting in osmotic swelling of the cartilage in early OA.

The role of changes in extracellular matrix of cartilage in the presence of inflammation on the pathology of osteoarthritis

Osteoarthritis (OA) is a degenerative disease that affects various tissues surrounding joints such as articular cartilage, subchondral bone, synovial membrane, and ligaments. No therapy is currently available to completely prevent the initiation or progression of the disease partly due to poor understanding of the mechanisms of the disease pathology. Cartilage is the main tissue afflicted by OA, and chondrocytes, the sole cellular component in the tissue, actively participate in the degeneration process. Multiple factors affect the development and progression of OA including inflammation that is sustained during the progression of the disease and alteration in biomechanical conditions due to wear and tear or trauma in cartilage. During the progression of OA, extracellular matrix (ECM) of cartilage is actively remodeled by chondrocytes under inflammatory conditions. This alteration of ECM, in turn, changes the biomechanical environment of chondrocytes, which further drives the progression of the disease in the presence of inflammation. The changes in ECM composition and structure also prevent participation of mesenchymal stem cells in the repair process by inhibiting their chondrogenic differentiation. This review focuses on how inflammation-induced ECM remodeling disturbs cellular activities to prevent self-regeneration of cartilage in the pathology of OA.