Epidemiology of osteoarthritis

Wavelength-dependent penetration depth of near infrared radiation into cartilage

Articular cartilage is a hyaline cartilage that lines the subchondral bone in the diarthrodial joints. Near infrared (NIR) spectroscopy is emerging as a nondestructive modality for the evaluation of cartilage pathology; however, studies regarding the depth of penetration of NIR radiation into cartilage are lacking. The average thickness of human cartilage is about 1-3 mm, and it becomes even thinner as OA progresses. To ensure that spectral data collected is restricted to the tissue of interest, i.e. cartilage in this case, and not from the underlying subchondral bone, it is necessary to determine the depth of penetration of NIR radiation in different wavelength (frequency) regions. In the current study, we establish how the depth of penetration varies throughout the NIR frequency range (4000-10 000 cm(-1)). NIR spectra were collected from cartilage samples of different thicknesses (0.5 mm to 5 mm) with and without polystyrene placed underneath. A separate NIR spectrum of polystyrene was collected as a reference. It was found that the depth of penetration varied from ∼1 mm to 2 mm in the 4000-5100 cm(-1) range, ∼3 mm in the 5100-7000 cm(-1) range, and ∼5 mm in the 7000-9000 cm(-1) frequency range. These findings suggest that the best NIR region to evaluate cartilage with no subchondral bone contribution is in the range of 4000-7000 cm(-1).

On the predictive utility of animal models of osteoarthritis

Animal models of osteoarthritis are extensively used for investigating disease pathways and for preclinical testing of novel therapies. Their predictive utility, however, has often been questioned, mainly because preclinical efficacy of novel therapeutics is poorly translated in clinical trials. In the current narrative review, we consider the preclinical models that were used to support undertaking clinical trials for disease-modifying osteoarthritis drugs, and compare outcomes between clinical and preclinical studies. We discuss this in light of the 1999 Food and Drug Administration draft guidelines for industry for use in the development of drugs, devices, and biological products intended for the treatment of osteoarthritis, which raised five considerations on the usefulness of osteoarthritis models. We systematically discuss what has been learnt regarding these five points since 1999, with emphasis on replicating distinct risk factors and subtypes of human osteoarthritis, and on comprehensive evaluation of the disease in animals, including pathology of all joint tissues, biomarker analysis, and assessment of pain and joint function. Finally, we discuss lessons learnt and propose some recommendations for how the evidence from preclinical research might be strengthened with a view to improving success in clinical translation.

Racial differences in biochemical knee cartilage composition between African-American and Caucasian-American women with 3 T MR-based T2 relaxation time measurements--data from the Osteoarthritis Initiative

OBJECTIVE

To determine whether knee cartilage composition differs between African-American and Caucasian-American women at risk for Osteoarthritis (OA) using in vivo 3 T MRI T2 relaxation time measurements.

METHODS

Right knee MRI studies of 200 subjects (100 African-American women, and 100 closely matched Caucasian-American women) were selected from the Osteoarthritis Initiative (OAI). Knee cartilage was segmented in the patellar (PAT), medial and lateral femoral (MF/LF), and medial and lateral tibial compartments (MT/LT)). Mean T2 relaxation time values per compartment and per whole joint cartilage were generated and analyzed spatially via laminar and grey-level co-occurrence matrix (GLCM) texture methods. Presence and severity of cartilage lesions per compartment were graded using a modified WORMS grading. Statistical analysis employed paired t- and McNemar testing.

RESULTS

While African-American women and Caucasian-Americans had similar WORMS cartilage lesion scores (P = 0.970), African-Americans showed significantly lower mean T2 values (∼1 ms difference; ∼0.5SD) than Caucasian-Americans in the whole knee cartilage (P < 0.001), and in the subcompartments (LF: P = 0.001, MF: P < 0.001, LT: P = 0.019, MT: P = 0.001) and particularly in the superficial cartilage layer (whole cartilage: P < 0.001, LF: P < 0.001, MF: P < 0.001, LT: P = 0.003, MT: P < 0.001). T2 texture parameters were also significantly lower in the whole joint cartilage of African-Americans than in Caucasian-Americans (variance: P = 0.001; contrast: P = 0.018). In analyses limited to matched pairs with no cartilage lesions in a given compartment, T2 values remained significantly lower in African-Americans.

CONCLUSION

Using T2 relaxation time as a biomarker for the cartilage collagen network, our findings suggest racial differences in the biochemical knee cartilage composition between African-American and Caucasian-American women.

¹⁸F-FPRGD₂ PET/CT imaging of musculoskeletal disorders

OBJECTIVE

This work reports on musculoskeletal uptake of ¹⁸F-FPRGD₂, targeting the integrin αvβ3, in patients who had undergone ¹⁸F-FPRGD₂ positron emission tomography combined with computed tomography (PET/CT) for oncologic purposes.

METHODS

Whole-body ¹⁸F-FPRGD₂ PET/CT images of 62 cancer patients were retrospectively reviewed to detect foci of musculoskeletal ¹⁸F-FPRGD₂ uptake. For 37 patients, a FDG PET/CT performed in clinical settings was available. In each joint with an abnormal uptake, the maximum standardized uptake value (SUVmax) was estimated.

RESULTS

A total of 260 musculoskeletal foci of ¹⁸F-FPRGD₂ uptake were detected. Most common sites of uptake were joints and discs (n = 160; 61.5%), entheses (osteotendinous and osteoligamentous junctions; n = 55; 21.2%) and recent fractures (n = 18; 6.9%). In addition, 27 (10.4%) miscellaneous foci were detected. Out of the 146 lesions for which a FDG PET was available, 63% showed both ¹⁸F-FPRGD₂ and FDG uptake, 33.6% did not show FDG avidity and 3.4% showed only FDG uptake. The uptake intensity of the 92 lesions positive with ¹⁸F-FPRGD₂ and FDG was similar with both radiopharmaceuticals, but the target-to-background (blood pool or muscle) ratios were significantly higher with ¹⁸F-FPRGD₂ than with FDG (p < 0.0001).

CONCLUSION

The ¹⁸F-FPRGD₂ uptake in joints, spine degenerative diseases and tendons was highly prevalent in our population. Up to one-third of ¹⁸F-FPRGD₂ foci showed no FDG uptake suggesting that ¹⁸F-FPRGD₂ signal may not be related to inflammatory angiogenesis only.

Menisectomized miniature Vietnamese pigs develop articular cartilage pathology resembling osteoarthritis

Animal models have been used to understand the basic biology of osteoarthritis (OA) and have helped to identify new candidate biomarkers for the early diagnosis and treatment of this condition. Small animals cannot sufficiently mimic human diseases; therefore, large animal models are needed. Pigs have been used as models for human diseases because they are similar to humans in terms of their anatomy, physiology and genome. Hence, we analyzed articular cartilage and synovial membrane pathology in miniature Vietnamese pigs after a unilateral partial menisectomy and 20-day exercise regimen to determine if the pigs developed pathological characteristics similar to human OA. Histological and protein expression analysis of articular cartilage from menisectomized pigs revealed the following pathologic changes resembling OA: fibrillation, fissures, chondrocyte cluster formation, decrease in proteoglycan content and upregulation of the OA-associated proteins MMP-3, MMP-13, procaspase-3 and IL-1β. Moreover, histological analysis of synovial membrane revealed mild synovitis, characterized by hyperplasia, cell infiltration and neoangiogenesis. Pathological changes were not observed in the contralateral joints or the joints of sham-operated pigs. Further studies are required to validate such an OA model; however, our results can encourage the use of pigs to study early stages of OA physiopathology. Based on their similarities to humans, pigs may be useful for preclinical studies to identify new candidate biomarkers and novel treatments for OA.

Annual consultation incidence of osteoarthritis estimated from population-based health care data in England

OBJECTIVES

To estimate the consultation incidence of OA using population-based health care data in England and compare OA incidence figures with those derived in other countries.

METHODS

A population-based health care database (Consultations in Primary Care Archive) in England was used to derive the consultation incidence of OA (overall and by joint site) using the maximum available run-in period method. These estimates, and their distribution by age and sex, were compared with those published from population-based health care databases in Canada, the Netherlands and Spain. A novel age-stratified run-in period method was then used to investigate whether the consultation incidence has been increasing over time in younger adults.

RESULTS

The annual consultation incidence of OA (any joint) was 8.6/1000 persons ≥15 years of age (95% CI 7.9, 9.3) [6.3 (95% CI 5.5, 7.1) in men and 10.8 (95% CI 9.8, 12.0) in women]. Incidence increased sharply between 45 and 64 years of age, peaking at 75-84 years. The joint-specific incidence was 1.4 (95% CI 1.1, 1.7), 3.5 (95% CI 3.1, 3.9) and 1.3 (95% CI 1.1, 1.6) for hip OA, knee OA and hand OA, respectively. The estimates and their distribution by age and sex were broadly consistent with international estimates. Between 2003 and 2010, incidence in those aged 35-44 years increased from 0.3 to 2.0/1000 persons.

CONCLUSION

Newly diagnosed cases of OA in England occur in 9 in 1000 at-risk adults each year, similar to other international estimates. Although lower, the consultation incidence proportion in younger adults appears to have increased in the past decade.

Gene-gene interactions between TGF-β/Smad3 signalling pathway polymorphisms affect susceptibility to knee osteoarthritis

OBJECTIVE

Transforming growth factor/Smad family member 3 (TGF)-β/Smad3 signalling is essential for maintaining articular cartilage. A relationship between the genetic variants of TGF-β itself, TGF-β signalling and binding molecules, and osteoarthritis (OA) has been reported. Although variants of candidate genes have become prime targets for genetic analysis, their detailed interplay has not been documented. Our goal was to establish whether single nucleotide polymorphisms (SNPs) of TGF-β1, TGF-βRI, Smad3 and tissue inhibitor of metalloproteinases 3 (TIMP3), and their interactions, are associated with knee OA.

DESIGN

We performed a case-control association study and genotyped 518 knee patients with OA and 468 healthy controls. All participants were genotyped for TGF-β1 (rs1800469C/T), TGF-βRI (rs1590A/G), Smad3 (rs12901499A/G and rs6494629T/C), and TIMP3 (rs715572G/A and rs1962223G/C) polymorphisms by polymerase chain reaction-restriction fragment length polymorphism analysis. Multifactor dimensionality reduction (MDR) was used to identify gene-gene interactions.

RESULTS

Significant associations were observed for TIMP3 rs715572G/A polymorphisms in knee patients with OA and healthy individuals. The GA heterozygote in TIMP3 (rs715572G/A) was significantly associated with OA (p=0.007). Patient stratification using the Kellgren-Lawrence grading scale showed significant differences in TIMP3 rs715572G/A genotypes between grade 4 knee OA and controls. By MDR analysis, a two-locus model (Smad3 rs6494629T/C and TIMP3 rs715572G/A) of gene-gene interaction was the best for predicting knee OA risk, and its maximum testing accuracy was 57.55% and maximum cross-validation consistency was 10/10.

CONCLUSIONS

TIMP3 rs715572G/A is a candidate protective gene for severe knee OA. Gene-gene interactions between Smad3 rs6494629T/C and TIMP3 rs715572G/A polymorphisms may play more important protective roles in knee OA.

Animal Models of Osteoarthritis: Comparisons and Key Considerations

Osteoarthritis (OA) is unquestionably one of the most important chronic health issues in humans, affecting millions of individuals and costing billions of dollars annually. Despite widespread awareness of this disease and its devastating impact, the pathogenesis of early OA is not completely understood, hampering the development of effective tools for early diagnosis and disease-modifying therapeutics. Most human tissue available for study is obtained at the time of joint replacement, when OA lesions are end stage and little can be concluded about the factors that played a role in disease development. To overcome this limitation, over the past 50 years, numerous induced and spontaneous animal models have been utilized to study disease onset and progression, as well as to test novel therapeutic interventions. Reflecting the heterogeneity of OA itself, no single "gold standard" animal model for OA exists; thus, a challenge for researchers lies in selecting the most appropriate model to answer a particular scientific question of interest. This review provides general considerations for model selection, as well as important features of species such as mouse, rat, guinea pig, sheep, goat, and horse, which researchers should be mindful of when choosing the "best" animal model for their intended purpose. Special consideration is given to key variations in pathology among species as well as recommended guidelines for reporting the histologic features of each model.

Sclerostin and skeletal health

Sclerostin is a cysteine-knot glycoprotein product of the SOST gene, predominately expressed by osteocytes, that is a regulator of osteoblastic bone formation. When sclerostin binds to its low-density lipoprotein receptor-related proteins 5 and 6 on the cell membrane of osteoblasts, it inhibits canonical Wnt/β-catenin signaling and reduces osteoblastic bone formation. Sclerostin was first identified in the study of two rare autosomal recessive disorders, sclerosteosis and van Buchem disease, which are associated with absent or reduced levels of sclerostin. Although homozygote patients with these disorders have serious adverse clinical consequences due to excessive bone growth, heterozygote patients have a normal phenotype, high bone mass, and very low risk of fractures. This has led to the concept that downregulation of sclerostin might be effective in the treatment of osteoporosis. Several humanized monoclonal antibodies to sclerostin, including romosozumab and blosozumab, are now in clinical development. Preliminary data show that these agents result in a transient increase in bone formation markers, a sustained decrease in bone resorption markers, and a robust increase in bone mineral density. If any of these agents are found to reduce fracture risk with a favorable safety profile, it will expand the options for osteoanabolic therapy for patients at high risk for fractures.

Use of Femoral Head and Neck Ostectomy and Physical Therapy to Manage Osteoarthritis in a Rhesus Macaque (Macaca mulatta)

Osteoarthritis is associated with pain and immobility in both humans and animals. However, available resources for osteoarthritis management in captive NHP are limited. This case report describes a novel management strategy for a 10-y-old male macaque with unilateral hindlimb lameness, prominent muscle wasting, and severely limited range of motion. Radiographs of the affected limb showed lytic lesions of the femoral head. To relieve pain and improve mobility, femoral head and neck ostectomy (FHO) was performed, and multiple pharmacotherapies were initiated. The macaque also received a unique method of physical therapy that required no sedation, acted as enrichment, and was implemented by using a conventional caging system. The response to therapy was monitored by measuring thigh circumference in the operated and nonoperated limbs, which demonstrated improvement in both legs. The unique physical therapy in conjunction with surgery and pharmacotherapy benefited the macaque with osteoarthritis by reducing discomfort and improving mobility.

Asporin and osteoarthritis

OBJECTIVE

To provide an overview of the literature describing the role of asporin, a small leucine-rich proteoglycan (SLRP), in osteoarthritis (OA).

METHOD

A literature search was performed and reviewed using the narrative approach.

RESULTS

As a class I SLRP member, asporin, is distinct from other SLRPs. Accumulating evidence demonstrates the involvement of asporin in OA pathogenesis. Many human studies have been conducted to explore the association between the D-repeat polymorphisms and OA susceptibility, but these yield inconsistent results. Possible mechanisms for the involvement of asporin in OA pathology include its influence on TGF-β (transforming growth factor-β) signaling pathways and collagen mineralization. To date, no studies were found to use an asporin-deficient animal model that would help to understand disease mechanisms. Many issues must be addressed to clarify the link between asporin and OA to provide a novel therapeutic strategy for OA, perhaps through controlling and modifying the TGF-β-ECM system.

CONCLUSIONS

Studies examined demonstrate the involvement of asporin in OA pathogenesis, and possible mechanisms by which asporin may be involved in this process have been proposed. However, large-scale interracial studies should be conducted to investigate the association between asporin and OA, and further investigations are needed to obtain a better understanding of the disease mechanism, develop novel therapeutic strategies, and explore new approaches for diagnosis of OA.

Obesity is associated with a lower probability of achieving sustained minimal disease activity state among patients with psoriatic arthritis

AIM

To assess whether overweight and obese patients with psoriatic arthritis (PsA) are less likely to achieve sustained minimal disease activity (MDA) state compared to patients with normal weight.

METHODS

A cohort of patients was assessed at the University of Toronto PsA clinic at 6-12-month intervals according to a standard protocol from 2003 to 2012. Patients were categorised into the following groups according to their body mass index (BMI): normal (<25), overweight (25-30), and obese (>30). Sustained MDA was defined as achieving low disease activity state in five or more of the following domains for at least 1 year: skin, enthesitis, tender and swollen joint counts, pain, patient global assessment and function. Proportional odds discrete time to event analysis was used to investigate the association between BMI category and the achievement of sustained MDA.

RESULTS

Of the 557 patients included in the study, 36.2% were classified as overweight and 35.4% were obese. Overall, 66.1% of the patients achieved sustained MDA during the follow-up period. A dose-response association was found between obesity and the probability of achieving sustained MDA in the multivariate regression analysis. Patients in the higher BMI categories were less likely to achieve sustained MDA compared those in the lowest BMI category (overweight: OR 0.66 p=0.003; obese: OR 0.53 p<0.0001) after adjusting for potential confounding variables.

CONCLUSIONS

Overweight and obese patients with PsA are less likely to achieve sustained MDA compared to those of normal weight.

Early rehabilitation after total knee replacement surgery: a multicenter, noninferiority, randomized clinical trial comparing a home exercise program with usual outpatient care

OBJECTIVE

To determine, at 6 weeks postsurgery, if a monitored home exercise program (HEP) is not inferior to usual care rehabilitation for patients undergoing primary unilateral total knee replacement (TKR) surgery for osteoarthritis.

METHODS

We conducted a multicenter, randomized clinical trial. Patients ages 45-75 years were allocated at the time of hospital discharge to usual care rehabilitation (n = 196) or the HEP (n = 194). Outcomes assessed 6 weeks after surgery included the Western Ontario and McMaster Universities Osteoarthritis Index pain and physical function subscales, knee range of motion, and the 50-foot walk time. The upper bound of the 95% confidence interval (95% CI) mean difference favoring usual care was used to determine noninferiority.

RESULTS

At 6 weeks after surgery there were no significant differences between usual care and HEP, respectively, for pain (7.4 and 7.2; 95% CI mean difference [MD] -0.7, 0.9), physical function (22.5 and 22.4; 95% CI MD -2.5, 2.6), knee flexion (96° and 97°; 95% CI MD -4°, 2°), knee extension (-7° and -6°; 95% CI MD -2°, 1°), or the 50-foot walk time (12.9 and 12.9 seconds; 95% CI MD -0.8, 0.7 seconds). At 6 weeks, 18 patients (9%) allocated to usual care and 11 (6%) to the HEP did not achieve 80° knee flexion. There was no difference between the treatment allocations in the number of hospital readmissions.

CONCLUSION

The HEP was not inferior to usual care as an early rehabilitation protocol after primary TKR.

An optimized transversely isotropic, hyper-poro-viscoelastic finite element model of the meniscus to evaluate mechanical degradation following traumatic loading

Inverse finite element (FE) analysis is an effective method to predict material behavior, evaluate mechanical properties, and study differences in biological tissue function. The meniscus plays a key role in load distribution within the knee joint and meniscal degradation is commonly associated with the onset of osteoarthritis. In the current study, a novel transversely isotropic hyper-poro-viscoelastic constitutive formulation was incorporated in a FE model to evaluate changes in meniscal material properties following tibiofemoral joint impact. A non-linear optimization scheme was used to fit the model output to indentation relaxation experimental data. This study is the first to investigate rate of relaxation in healthy versus impacted menisci. Stiffness was found to be decreased (p=0.003), while the rate of tissue relaxation increased (p=0.010) at twelve weeks post impact. Total amount of relaxation, however, did not change in the impacted tissue (p=0.513).

Factors associated with treatment of osteoarthritis: Analysis of a COPCORD study in Nuevo León, México

INTRODUCTION

Osteoarthritis (OA) is the most prevalent rheumatic disease in Mexico. Treatment involves pharmacological and non-pharmacological strategies.

OBJECTIVE

To describe the factors associated with treatment of osteoarthritis in the urban and rural population of Nuevo León.

METHODS

Analysis of a cross-sectional study of patients with OA from a COPCORD study database. Univariate and multivariate analyses of the variables associated with treatment of OA.

RESULTS

We included 696 patients with OA with an average age of 58 years (SD 14.1), 484 (69.5%) women. Pain with a visual analog scale (VAS) ≥4 was present in 507 (72.8%) patients. Functional disability was present in 133 (19%) patients and a mean HAQ of 0.37 (IQR 0.75) was found. The most frequent place of OA was knee in 356 (51.1%) patients; 259 (37%) patients already knew their diagnosis. The most employed treatments were non-steroidal anti-inflammatory drugs (289 patients, 58.5%). The variables associated with treatment were age >58 years (OR 1.3, 95% CI 1.0-1.5), female gender (OR 1.17, 95% CI 1.0-1.3), VAS pain ≥4 (OR 1.3, 95% CI 1.1-1.4), functional disability (OR 2.6, 95% CI 1.6-4.1), HAQ >0.375 (OR 1.9, 95% CI 1.5-2.4), and past diagnosis of OA (OR 5.1, 95% CI 3.3-8.0). In the multivariate analysis, VAS pain ≥4 (OR 1.9, 95% CI 1.2-2.8), kneeling disability (OR 3.15, 95% CI 1.3-7.4) and previous diagnosis of OA (OR 7.6, 95% CI 4.5-12.9) had statistical significance.

CONCLUSION

factors associated with treatment of OA are VAS pain ≥4, kneeling disability and previous diagnosis of OA.

Osteoarthritis and bone mineral density: are strong bones bad for joints?

Osteoarthritis (OA) is a common and disabling joint disorder affecting millions of people worldwide. In OA, pathological changes are seen in all of the joint tissues including bone. Although both cross-sectional and longitudinal epidemiological studies have consistently demonstrated an association between higher bone mineral density (BMD) and OA, suggesting that increased BMD is a risk factor for OA, the mechanisms underlying this observation remain unclear. Recently, novel approaches to examining the BMD-OA relationship have included studying the disease in individuals with extreme high bone mass, and analyses searching for genetic variants associated with both BMD variation and OA, suggesting possible pleiotropic effects on bone mass and OA risk. These studies have yielded valuable insights into potentially relevant pathways that might one day be exploited therapeutically. Although animal models have suggested that drugs reducing bone turnover (antiresorptives) may retard OA progression, it remains to be seen whether this approach will prove to be useful in human OA. Identifying individuals with a phenotype of OA predominantly driven by increased bone formation could help improve the overall response to these treatments. This review aims to summarise current knowledge regarding the complex relationship between BMD and OA.

Intermediate and long-term quality of life after total knee replacement: a systematic review and meta-analysis

BACKGROUND

Total knee replacement is a highly successful and frequently performed operation. Technical outcomes of surgery are excellent, with favorable early postoperative health-related quality of life. This study reviews intermediate and long-term quality of life after surgery.

METHODS

A systematic review and meta-analysis of all studies published from January 2000 onward was performed to evaluate health-related quality of life after primary total knee replacement for osteoarthritis in patients with at least three years of follow-up. Key outcomes were postoperative quality of life, function, and satisfaction compared with the preoperative status. Strict inclusion and exclusion criteria were applied. Quality appraisal and data tabulation were performed with use of predefined criteria. Data were synthesized by narrative review and random-effects meta-analysis utilizing standardized mean differences. Heterogeneity was assessed with the tau(2) and I(2) statistics.

RESULTS

Nineteen studies were included in the review. Intermediate and long-term postoperative quality of life was superior to the preoperative level in qualitative and quantitative analyses. The pooled effect in combined WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) and KSS (Knee Society Score) outcomes was a marked improvement from baseline with respect to the total score (2.17; 95% CI [confidence interval], 1.13 to 3.22; p < 0.0001) and the pain (1.72; 95% CI, 0.97 to 2.46; p < 0.00001) and function (1.26; 95% CI, 0.87 to 1.64; p < 0.00001) domains. Most patients were satisfied with the surgery and derived substantial benefits for daily functional activities. Tau(2) (0.20 to 1.10) and I(2) (90% to 98%) values implied significant clinical and statistical heterogeneity.

CONCLUSIONS

Total knee replacement confers significant intermediate and long-term benefits with respect to both disease-specific and generic health-related quality of life, especially pain and function, leading to positive patient satisfaction. Recommendations for necessary future studies are provided.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

An Ongoing Assessment of Osteoarthritis in African Americans and Caucasians in North Carolina: The Johnston County Osteoarthritis Project

Osteoarthritis (OA) is the most common type of arthritis and is frequently associated with significant disability. Its public health impact is increasing due to the aging of the population and the obesity epidemic. The Johnston County Osteoarthritis Project is an ongoing, population-based prospective cohort begun in 1990 to fill knowledge gaps about prevalence, incidence, and progression of OA, and its risk factors, in African American and Caucasian men and women in North Carolina. Critically important phenotypic differences were observed in patterns of multi-joint OA burden, with African Americans much less likely than Caucasians to have hand OA and much more likely to have multiple large joint involvement. Racial differences also exist in systemic bone and joint tissue biomarkers. Novel potentially modifiable risk factors identified in this cohort include selenium and blood lead levels. Selected key findings of this ongoing study will be discussed.

Individuals with primary osteoarthritis have different phenotypes depending on the affected joint - a case control study from southern sweden including 514 participants

Objective:

The aim of this study was to evaluate whether primary osteoarthritis (OA), independent of affected joint, is associated with a phenotype that is different from the phenotype in a normative cohort. Material and

Methods:

We included 274 patients with primary OA, 30 women and 32 men (mean age 66 years, range 42-84) with primary hip OA, 38 women and 74 men (mean age 61 years; range 34-85) with primary knee OA, 42 women and 19 men (men age 64 years, range 42-87) with primary ankle or foot OA and 20 women and 19 men (mean age 66 years, range 47-88) with primary hand or finger OA. Of all patients included with OA, 23% had hip OA, 41% knee OA, 22% ankle or foot OA and 14% hand or finger OA. Serving as references were 122 women and 118 men of the same ages who were population-based, included as a control cohort. We measured total body BMD (g/cm2) and proportion of fat and lean mass (%) with dual energy X-ray absorptiometry. Height, weight and BMI (kg/m2) were also assessed. We then calculated Z-scores (number of standard deviations difference from the mean value of the control cohort) in the OA patients and compared these between the groups.

Results:

Individuals with hand OA and controls had similar phenotype. Individuals with lower extremity OA, irrespective of the affected joint, had similar weight, BMI and BMD, but higher than in individuals with hand OA and controls (all p<0.05). Individuals with lower extremity OA had higher fat and lower lean mass than individuals with hand OA and controls (all p<0.001).

Conclusion:

Individuals with primary OA in the lower extremity have a phenotype with higher BMD, higher BMI, proportionally higher fat content and lower lean body mass content. The different skeletal phenotypes in our patients with OA in the lower extremity and patients with hand OA indicate that separate pathophysiologic pathways may be responsible for primary OA in different joints

Elevated VEGF levels contribute to the pathogenesis of osteoarthritis

Background

The aim of our meta-analysis is to understand the relationship between the pathogenesis of osteoarthritis and the expression levels of vascular endothelial growth factor (VEGF) in multiple disease tissues in osteoarthritis patients.

Methods

The following electronic databases were searched, without language restrictions, to retrieve published studies relevant to VEGF and osteoarthritis: MEDLINE (1966 ~ 2013), the Cochrane Library Database (Issue 12, 2013), EMBASE (1980 ~ 2013), CINAHL (1982 ~ 2013), Web of Science (1945 ~ 2013) and the Chinese Biomedical Database (CBM) (1982 ~ 2013). Meta-analysis of the extracted data was performed using the STATA statistical software. Standardized mean difference (SMD) with its corresponding 95% confidence interval (95% CI) was calculated.

Results

A total of 11 case–control studies, containing 302 osteoarthritis patients and 195 healthy controls, met our selection criteria for this meta-analysis. Our analyses of the data available from multiple disease tissues demonstrate that VEGF expression levels in osteoarthritis patients are significantly higher than healthy controls (SMD = 1.18, 95% CI: 4.91 ~ 9.11, P < 0.001). A subgroup analysis based on ethnicity revealed that both Asian and Caucasian osteoarthritis patients had higher levels of VEGF expression compared to their respective healthy counterparts (Asians: SMD = 5.49, 95% CI: 3.44 ~ 7.54, P < 0.001; Caucasians: SMD = 15.17, 95% CI: 5.21 ~ 25.13, P = 0.003; respectively). We also performed other subgroup analyses based on country, language and sample source, and the results showed that, in all these subgroups, osteoarthritis patients had higher levels of VEGF expression than healthy controls (all P > 0.05).

Conclusion

Our meta-analysis provides evidence that higher VEGF expression levels strongly correlate with the pathogenesis of osteoarthritis.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-437) contains supplementary material, which is available to authorized users.

Clinic variation in recruitment metrics, patient characteristics and treatment use in a randomized clinical trial of osteoarthritis management

Background

The Patient and PRovider Interventions for Managing Osteoarthritis (OA) in Primary Care (PRIMO) study is one of the first health services trials targeting OA in a multi-site, primary care network. This multi-site approach is important for assessing generalizability of the interventions. These analyses describe heterogeneity in clinic and patient characteristics, as well as recruitment metrics, across PRIMO study clinics.

Methods

Baseline data were obtained from the PRIMO study, which enrolled n = 537 patients from ten Duke Primary Care practices. The following items were examined across clinics with descriptive statistics: (1) Practice Characteristics, including primary care specialty, numbers and specialties of providers, numbers of patients age 55+, urban/rural location and county poverty level; (2) Recruitment Metrics, including rates of eligibility, refusal and randomization; (3) Participants’ Characteristics, including demographic and clinical data (general and OA-related); and (4) Participants’ Self-Reported OA Treatment Use, including pharmacological and non-pharmacological therapies. Intraclass correlation coefficients (ICCs) were computed for participant characteristics and OA treatment use to describe between-clinic variation.

Results

Study clinics varied considerably across all measures, with notable differences in numbers of patients age 55+ (1,507-5,400), urban/rural location (ranging from “rural” to “small city”), and proportion of county households below poverty level (12%-26%). Among all medical records reviewed, 19% of patients were initially eligible (10%-31% across clinics), and among these, 17% were randomized into the study (13%-21% across clinics). There was considerable between-clinic variation, as measured by the ICC (>0.01), for the following patient characteristics and OA treatment use variables: age (means: 60.4-66.1 years), gender (66%-88% female), race (16%-61% non-white), low income status (5%-27%), presence of hip OA (26%-68%), presence both knee and hip OA (23%-61%), physical therapy for knee OA (24%-61%) and hip OA (0%-71%), and use of knee brace with metal supports (0%-18%).

Conclusions

Although PRIMO study sites were part of one primary care practice network in one health care system, clinic and patient characteristics varied considerably, as did OA treatment use. This heterogeneity illustrates the importance of including multiple, diverse sites in trials for knee and hip OA, to enhance the generalizability and evaluate potential for real-world implementation.

Trial registration

Clinical Trial Registration Number: NCT 01435109

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-413) contains supplementary material, which is available to authorized users.

Socio-economic costs of osteoarthritis: a systematic review of cost-of-illness studies

OBJECTIVE

The burden of illness that can be attributed to osteoarthritis is considerable and ever increasing. The aim of this systematic review is to analyze currently available data derived from cost-of-illness studies on the healthcare and non-healthcare costs of osteoarthritis.

METHODS

PubMed, Index Medicus Español (IME), and the Spanish Database of Health Sciences [Índice Bibliográfico Español en Ciencias de la Salud (IBECS)] were searched up to the end of April 2013. This study adhered to the PRISMA guidelines. Articles were reviewed and the study quality assessed by two independent investigators with consensus resolution of discrepancies.

RESULTS

We identified 39 studies that investigated the socio-economic cost of osteoarthritis. Only nine studies took a social perspective. Rather than estimating the incremental cost of osteoarthritis, nine studies estimated the total cost of treating patients with osteoarthritis without a control for comorbidity. The other 30 studies determined the incremental cost with or without a control group. Only nine studies assessed a comprehensive list of healthcare resources. The annual incremental healthcare costs of generalized osteoarthritis ranged from €705 to €19,715. The annual incremental non-healthcare-related costs of generalized osteoarthritis ranged from €432 to €11,956.

CONCLUSIONS

The study concludes that the social cost of osteoarthritis could be between 0.25% and 0.50% of a country׳s GDP. This should be considered in order to foster studies that take into account both healthcare and non-healthcare costs.

Adverse events among seniors receiving spinal manipulation and exercise in a randomized clinical trial

Spinal manipulative therapy (SMT) and exercise have demonstrated effectiveness for neck pain (NP). Adverse events (AE) reporting in trials, particularly among elderly participants, is inconsistent and challenges informed clinical decision making. This paper provides a detailed report of AE experienced by elderly participants in a randomized comparative effectiveness trial of SMT and exercise for chronic NP. AE data, consistent with CONSORT recommendations, were collected on elderly participants who received 12 weeks of SMT with home exercise, supervised plus home exercise, or home exercise alone. Standardized questions were asked at each treatment; participants were additionally encouraged to report AE as they occurred. Qualitative interviews documented participants' experiences with AE. Descriptive statistics and content analysis were used to categorize and report these data. Compliance was high among the 241 randomized participants. Non-serious AE were reported by 130/194 participants. AE were reported by three times as many participants in supervised plus home exercise, and nearly twice as many as in SMT with home exercise, as in home exercise alone. The majority of AE were musculoskeletal in nature; several participants associated AE with specific exercises. One incapacitating AE occurred when a participant fell during supervised exercise session and fractured their arm. One serious adverse event of unknown relationship occurred to an individual who died from an aneurysm while at home. Eight serious, non-related AE also occurred. Musculoskeletal AE were common among elderly participants receiving SMT and exercise interventions for NP. As such, they should be expected and discussed when developing care plans.

Health issues for menopausal women: the top 11 conditions have common solutions

Multiple health issues affect women throughout the life course differently from men, or do not affect men at all. Although attention to women's health is important in all stages in life, health among middle-aged and elderly women has not received sufficient attention by scientists and policy-makers. Related to the menopausal transition and the experiences accumulated until that age, many diseases occur or further develop in middle-aged and elderly women. To improve women's quality of life and guarantee a long-lasting and active role for middle-aged and elderly women in society, prevention of chronic diseases and disability is a key aspect. In this manuscript we give an overview of the major health issues for peri- and post-menopausal women, we summarize risk factors and interventions to improve menopausal health. Based on the available scientific literature and the global burden of disease endeavor, we have selected and herein describe the following top 11 key health issues, selected in terms of burden exerted in women's mortality, morbidity, disability and quality of life: cardiovascular disease, musculoskeletal disorders, cancer, cognitive decline and dementia, chronic obstructive pulmonary disease, diabetes mellitus, metabolic syndrome, depression, vasomotor symptoms, sleep disturbances and migraine.

Development of the Knee OA Pre-Screening Questionnaire

AIM

Self-report questionnaires are still considered to be a useful instrument for disease screening and for epidemiological studies. Few questionnaires have been developed for the purpose of screening for knee osteoarthritis (KOA). The aim of this study was to develop a KOA screening tool that is useful for health and exercise professionals who do not have access to advanced and costly diagnostic instruments.

METHODS

This study comprised five steps: content validity, reliability, criterion validity, construct validity and responsiveness. Internal consistency was verified using Cronbach's alpha and the intraclass correlation coefficient (ICC). Reproducibility was analyzed using the ICC (1 week). Criterion validity was assessed by comparing the Knee OA Pre-Screening Questionnaire (KOPS) score with the Short Form (SF)-12, the Knee Injury and Osteoarthritis Outcome Scores questionnaire and the 6 min walk test. Construct validity was verified using the receiver operating characteristic (ROC) curve (American College of Rheumatology clinical criteria and X-ray). Responsiveness was analyzed over 3 months of an aquatic exercise program using the pooled effect size.

RESULTS

The overall KOPS score yielded a Cronbach's alpha of 0.747 and an ICC of 0.646. KOPS was considered reproducible (ICC: 0.895-0.992; Cronbach's alpha: 0.894-0.979). The ROC curve revealed a sensitivity of 86.96 and a specificity of 75.82. The KOPS demonstrated medium responsiveness in terms of the total score and the pain and symptoms components.

CONCLUSION

The KOPS questionnaire is valid for the purposes for which it was created, and its translation into English should be considered.

In vitro toxicity in long-term cell culture of MR contrast agents targeted to cartilage evaluation

OBJECTIVE

Contrast-enhanced magnetic resonance (MR) imaging methods have been proposed for non-invasive evaluation of osteoarthritis (OA). We measured cell toxicities of cartilage-targeted low-generation dendrimer-linked nitroxide MR contrast agents and gadopentetate dimeglumine (Gd-DTPA) on cultured chondrocytes.

DESIGN

A long-term Swarm rat chondrosarcoma chondrocyte-like cell line was exposed for 48-h to different salts (citrate, maleate, tartrate) and concentrations of generation one or two diaminobutyl-linked nitroxides (DAB4-DLN or DAB8-DLN), Gd-DTPA, or staurosporine (positive control). Impact on microscopic cell appearance, MTT spectrophotometric assays of metabolic activity, and quantitative PicoGreen assays of DNA content (cell proliferation) were measured and compared to untreated cultures.

RESULTS

Chondrocyte cultures treated with up to 7.5 mM Gd-DTPA for 48-h had no statistical differences in DNA content or MTT reaction compared to untreated cultures. At all doses, DAB4-DLN citrate treated cultures had results similar to untreated and Gd-DTPA-treated cultures. At doses >1 mM, DAB4-DLN citrate treated cultures showed statistically greater DNA and MTT reaction than maleate and tartrate DAB4-DLN salts. Cultures exposed to 5 mM or 7.5 mM DAB8-DLN citrate exhibited rounded cells, poor cell proliferation, and barely detectable MTT reaction. Treatment with 0.1 μM staurosporine caused chondrocyte death.

CONCLUSION

Long-term exposure, greater than clinically expected, to either DAB4-DLN citrate or Gd-DTPA had no detectable toxicity with results equivalent to untreated cultures. DAB4-DLN citrate was more biocompatible than either the maleate or tartrate salts. Cells exposed for 48-h to 5 mM or 7.5 mM DAB8-DLN salts demonstrated significant cell toxicity. Further evaluation of DAB8-DLN with clinically appropriate exposure times is required to determine the maximum useful concentration.

Update on biological therapies for knee injuries: osteoarthritis

Osteoarthritis (OA) is a progressive disease that causes functional impairment of the joints. Chronic forms of knee OA have been increasing worldwide, limiting patients' quality of life. Recent studies have sought to increase effectiveness and quality in the development of new therapies, such as platelet-rich plasma, hyaluronic acid, stem cells, and nuclear factor κB, aimed principally at reducing proinflammatory activity, pain, and degeneration of the knee joints. The goal of this review is to present an update on biological therapies for knee OA and to provide guidance for future OA studies.

The epidemiology of osteoarthritis

Osteoarthritis (OA) is a leading cause of disability and its incidence is rising due to increasing obesity and an ageing population. Risk factors can be divided into person-level factors, such as age, sex, obesity, genetics, race/ethnicity and diet, and joint-level factors including injury, malalignment and abnormal loading of the joints. The interaction of these risk factors is complex and provides a challenge to the managing physician. The purpose of this review is to illustrate how each of these factors interact together to instigate incident OA as well as to outline the need for ongoing epidemiologic studies for the future prevention of both incident and progressive OA. It is only by understanding the impact of this disease and the modifiable risk factors that we will be able to truly target public health prevention interventions appropriately.

An intron polymorphism of the fibronectin gene is associated with end-stage knee osteoarthritis in a Han Chinese population: two independent case-control studies

Background

Knee osteoarthritis (OA) is a complex disease involving both biomechanical and metabolic factors that alter the tissue homeostasis of articular cartilage and subchondral bone. The catabolic activities of extracellular matrix degradation products, especially fibronectin (FN), have been implicated in mediating cartilage degradation. Chondrocytes express several members of the integrin family which can serve as receptors for FN including integrins α5β1, αvβ3, and αvβ5. The purpose of this study was to determine whether polymorphisms in the FN (FN-1) and integrin genes are markers of susceptibility to, or severity of, knee OA in a Han Chinese population.

Methods

Two independent case–control studies were conducted on 928 patients with knee OA and 693 healthy controls. Ten single nucleotide polymorphisms (SNPs) of FN-1 and the integrin αV gene (ITGAV) were detected using the ABI 7500 real-time PCR system.

Results

The AT heterozygote in FN-1 (rs940739A/T) was found to be significantly associated with knee OA (adjusted OR = 1.44; 95% CI = 1.16–1.80) in both stages of the study. FN-1 rs6725958C/A and ITGAV rs10174098A/G SNPs were only associated with knee OA when both study groups were combined. Stratifying the participants by Kellgren-Lawrence (KL) score identified significant differences in the FN-1 rs6725958C/A and rs940739 A/T genotypes between patients with grade 4 OA and controls. Haplotype analyses revealed that TGA and TAA were associated with a higher risk of OA, and that TAG conferred a lower risk of knee OA in the combined population.

Conclusions

Our study suggests that the FN-1 rs940739A/T polymorphism may be an important risk factor of genetic susceptibility to knee OA in the Han Chinese population.

In vivo effect of two different pulsed electromagnetic field frequencies on osteoarthritis

Osteoarthritis (OA) is a joint pathology characterized by fibrillation, reduced cartilage thickness and subchondral bone sclerosis. There is evidence that pulsed electromagnetic fields (PEMFs) counteract OA progression, but the effect of two different PEMF frequencies has not yet been shown. The aim of this study was to test the effectiveness of PEMFs at two different frequencies (37 and 75 Hz) in a late OA stage in 21-month-old Guinea pigs. After 3 months of 6 h/day PEMF stimulation, histological and histomorphometric analyses of the knees were performed. At both frequencies, PEMFs significantly reduced histological cartilage score, fibrillation index (FI), subchondral bone thickness (SBT) and trabecular number (Tb.N) and increased trabecular thickness (Tb.Th) and separation (Tb.Sp) in comparison to the not treated SHAM group. However, PEMFs at 75 Hz produced significantly more beneficial effects on the histological score and FI than 37 Hz PEMFs. At 75 Hz, PEMFs counteracted cartilage thinning as demonstrated by a significantly higher cartilage thickness values than either those of the SHAM or 37 Hz PEMF-treated groups. Although in severe OA both PEMF frequencies were able to limit its progression, 75 Hz PEMF stimulation achieved the better results.

Role of sclerostin in bone and cartilage and its potential as a therapeutic target in bone diseases

Sclerostin is a small protein expressed by the SOST gene in osteocytes, bone cells that respond to mechanical stress applied to the skeleton and appear to play an important role in the regulation of bone remodeling. When sclerostin binds to its receptors on the cell surface of osteoblasts, a downstream cascade of intracellular signaling is initiated, with the ultimate effect of inhibiting osteoblastic bone formation. Recent studies have shown that the SOST gene is also expressed by articular chondrocytes and that modulation of its activity may have effects on articular cartilage and subchondral bone. The role of sclerostin in the pathogenesis of osteoarthritis in humans has not yet been defined, and the potential utility of treating osteoarthritis with interventions that alter sclerostin is not known. Rare genetic skeletal disorders in humans with low sclerostin levels, such as sclerosteosis and van Buchem disease, have been associated with a high bone mineral density (BMD) phenotype and low risk of fractures. This has led to the concept that antisclerostin interventions might be useful in the treatment of patients with osteoporosis and skeletal disorders associated with low bone mass. Compounds that inhibit sclerostin have been shown to stimulate bone formation and reduce bone resorption, with a robust increase in BMD. Investigational monoclonal antibodies to sclerostin, including romosozumab, blosozumab, and BPS804, have advanced to phase II clinical trials or beyond. If antisclerostin therapy is found to have beneficial effects on clinical endpoints, such as reduction of fracture risk or improvement in quality of life in patients with osteoarthritis, with a favorable balance of benefit and risk, then this class of compounds may become a prominent addition to the options for therapy of osteoporosis and other skeletal disorders.

Older Adults without Radiographic Knee Osteoarthritis: Knee Alignment and Knee Range of Motion

This study describes knee alignment and active knee range of motion (ROM) in a community-based group of 78-year old adults (n = 143) who did not have radiographic evidence of knee osteoarthritis in either knee (KL < 2). Although knee malalignment is a risk factor for knee osteoarthritis, most women and men had either valgus or varus alignments. Notably, no men were valgus in both knees. Women with both knees valgus had significantly greater body mass index (P > 0.001) than women with varus or straight knees. Men and women with valgus or varus knee alignments had generally lower ROM than individuals with both knees straight. In summary, this study highlights the complex relationships among knee alignment, ROM, body mass index, and gender in elderly adults without radiographic knee osteoarthritis.

Changes in MR relaxation times of the meniscus with acute loading: an in vivo pilot study in knee osteoarthritis

PURPOSE

To prospectively evaluate changes in T1ρ and T2 relaxation times in the meniscal body with acute loading using MRI in osteoarthritic knees and to compare these findings with those of age-matched healthy controls.

MATERIALS AND METHODS

Female subjects above 40 years of age with (N1  = 20) and without osteoarthritis (OA) (N2  = 10) were imaged on a 3 Tesla MR scanner using a custom made loading device. MR images were acquired, with the knee flexed at 20°, with and without a compressive load of 50% of the subject's bodyweight. The subjects were categorized based on the radiographic evidence of OA. Three different zones (outer, middle, and inner) of meniscus body were defined (each occupying 1/3rd the width). After adjusting for age and body mass index in the general linear regression model, repeated measures analysis of variance was used to detect significant differences in T1ρ and T2 with and without loading.

RESULTS

In the unloaded condition, the average T1ρ and T2 times were elevated in the outer and middle zones of the medial meniscus in OA subjects compared with the controls. In the loaded condition, T1ρ and T2 times of the outer zone of the medial meniscus was significantly elevated in OA subjects compared with controls. Finally the change (from unloaded to loaded) was significantly higher in controls than OA subjects (15.1% versus 8.3%; P = 0.039 for ΔT1ρ , and 11.5% versus 6.9%, P = 0.049 for ΔT2 ).

CONCLUSION

These findings suggest that while the OA process appears to affect the relaxation times of all regions within the meniscus, it may affect some regions sooner or to a greater degree. Furthermore, the differences in the change in relaxation times between unloaded and loaded conditions may reveal evidence about load transmission failure of the outer zone of the medial meniscus in subjects with knee OA. It is possible that these metrics (ΔT1ρ and ΔT2 ) may be valuable as an early biomechanical biomarker, which could be used to predict load transmission to the underlying articular cartilage.

Association between severity of knee osteoarthritis and serum and synovial fluid interleukin 17 concentrations

OBJECTIVE

To determine interleukin (IL)-17 concentrations in serum and synovial fluid from patients with knee osteoarthritis, and evaluate their correlation with disease severity.

METHODS

Serum and synovial fluid were collected from patients with primary knee osteoarthritis; age- and sex-matched healthy control subjects provided serum samples. This study was conducted retrospectively. IL-17 was quantified by enzyme-linked immunosorbent assay. Osteoarthritis severity and grade were assessed using the Lequesne index and Kellgren and Lawrence (KL) grading system, respectively.

RESULTS

Serum IL-17 concentrations were significantly higher in patients (n = 98) than in controls (n = 50). In the patient group, the synovial fluid IL-17 concentration increased significantly with KL grade and was significantly positively correlated with Lequesne index (r = 0.6232).

CONCLUSIONS

The synovial fluid IL-17 concentration could represent a useful biochemical marker to reflect knee osteoarthritis severity and progression.

Polypharmacy of osteoarthritis: the perfect intestinal storm

Osteoarthritis is an increasingly prevalent disorder with an incidence rate that rises sharply with age. Unfortunately, the most commonly used medications for providing symptomatic relief, nonsteroidal anti-inflammatory drugs (NSAIDs), can cause significant gastrointestinal (GI) ulceration. There is recent evidence that agents commonly employed to protect the upper GI tract actually increase the incidence and severity of ulceration and bleeding in the lower intestine. Intestinal injury is more difficult to diagnose and treat than upper GI damage, and symptoms correlate poorly with the severity of tissue injury. Moreover, use of low-dose aspirin for cardioprotection (a common co-treatment with the selective cyclooxygenase-2 inhibitors) further augments intestinal damage, particularly when enteric-coated aspirin is used. Thus, by focusing entirely on prevention of NSAID-induced damage to the upper GI tract, physicians may be inadvertently placing their patients at risk of serious, difficult-to-diagnose injury for which there are no proven-effective therapies and are associated with significantly higher rates of morbidity and mortality.

Adipose-derived mesenchymal stem cells for cartilage tissue engineering: state-of-the-art in in vivo studies

Several therapeutic approaches have been developed to address hyaline cartilage regeneration, but to date, there is no universal procedure to promote the restoration of mechanical and functional properties of native cartilage, which is one of the most important challenges in orthopedic surgery. For cartilage tissue engineering, adult mesenchymal stem cells (MSCs) are considered as an alternative cell source to chondrocytes. Since little is known about adipose-derived mesenchymal stem cell (ADSC) cartilage regeneration potential, the aim of this review was to give an overview of in vivo studies about the chondrogenic potential and regeneration ability of culture-expanded ADSCs when implanted in heterotopic sites or in osteoarthritic and osteochondral defects. The review compares the different studies in terms of number of implanted cells and animals, cell harvesting sites, in vitro expansion and chondrogenic induction conditions, length of experimental time, defect dimensions, used scaffolds and post-explant analyses of the cartilage regeneration. Despite variability of the in vivo protocols, it seems that good cartilage formation and regeneration were obtained with chondrogenically predifferentiated ADSCs (1 × 10(7) cells for heterotopic cartilage formation and 1 × 10(6) cells/scaffold for cartilage defect regeneration) and polymeric scaffolds, even if many other aspects need to be clarified in future studies.

The age-related changes in cartilage and osteoarthritis

Osteoarthritis (OA) is closely associated with aging, but its underlying mechanism is unclear. Recent publications were reviewed to elucidate the connection between aging and OA. With increasing OA incidence, more senior people are facing heavy financial and social burdens. Age-related OA pathogenesis is not well understood. Recently, it has been realized that age-related changes in other tissues besides articular cartilage may also contribute to OA development. Many factors including senescence-related secretory phenotypes, chondrocytes' low reactivity to growth factors, mitochondrial dysfunction and oxidative stress, and abnormal accumulation of advanced glycation end products (AGEs) may all play key roles in the pathogenesis of age-related OA. Lately, epigenetic regulation of gene expression was recognized for its impact on age-related OA pathogenesis. Up to now, few studies have been reported about the role of miRNA and long-noncoding RNA (lncRNA) in age-related OA. Research focusing on this area may provide valuable insights into OA pathogenesis. OA-induced financial and social burdens have become an increasingly severe threat to older population. Age-related changes in noncartilage tissue should be incorporated in the understanding of OA development. Growing attention on oxidative stress and epigenetics will provide more important clues for the better understanding of the age-related OA.