Relationship of gene expression in the injured human meniscus to body mass index: a biologic connection between obesity and osteoarthritis

Causal relationship between obesity and meniscal injuries: Two-sample Mendelian randomization

To investigate the causal relationship between obesity and meniscal injuries using Mendelian randomization (MR). Genetic loci independently associated with obesity and meniscal injuries in people of European origin were selected as instrumental variables using pooled data from genome-wide association studies. Three MR analyses, MR-Egger, weighted median and inverse variance weighting, were used to investigate the causal relationship between obesity and meniscal injuries. The results were tested for robustness by heterogeneity and multiplicity tests, and sensitivity analyses were performed using the "leave-one-out" method. The inverse variance weighting results showed an OR (95% CI) of 1.13 (1.04-1.22), P = .003, indicating a causal relationship between obesity and the occurrence of meniscal injuries. And no heterogeneity and multiplicity were found by the test and sensitivity analysis also showed robust results. In this study, genetic data were analyzed and explored using 2-sample MR analysis, and the results showed that obesity is a risk factor for meniscal injuries.

Older age and the presence of intrameniscal signs are risk factors for nonsurgical treatment failure of symptomatic intact discoid lateral meniscus

PURPOSE

The treatment for symptomatic intact discoid lateral meniscus (DLM) is controversial and the long-term clinical outcome remains unknown. The purpose of this study was to analyze the overall failure rate of nonsurgical treatment for symptomatic intact DLM and identify the risk factors for nonoperative management failure.

METHODS

Consecutive patients who underwent nonsurgical treatment for symptomatic intact DLM at our hospital from 2014 to 2017 were retrospectively reviewed. Patients were divided into Group A (failure group) and Group B (nonfailure group) based on overall failure criteria: conversion to surgery, progression of a tear on MRI re-examination, or severely abnormal International Knee Documentation Committee (IKDC) scores. Statistical analyses between the two groups were performed for demographic and radiographic characteristics. Multivariate regression analysis was used to determine the risk factors associated with worse outcomes.

RESULTS

One-hundred and four knees in 96 patients were included in this study. After a mean follow-up of 76.9 ± 11.1 months, 25 knees (24.0%) met the overall failure criteria. Multivariate regression analysis demonstrated that age and the presence of intrameniscus signals increased the risk of nonoperative management failure. The clinical criterion of age > 37.5 years combined with the imaging criterion of the presence of intrameniscal signals predicted conservative treatment failure of symptomatic intact DLM with a sensitivity of 0.87 and a specificity of 0.91.

CONCLUSION

Twenty-five (24.0%) knees that underwent nonsurgical treatment met the overall failure criteria after a mean follow-up of 76.9 months. With increased age and the presence of intrameniscal signals, the nonoperative results become worse.

LEVEL OF EVIDENCE

III.

Angiopoietin-like 3-derivative LNA043 for cartilage regeneration in osteoarthritis: a randomized phase 1 trial

Osteoarthritis (OA) is a common, debilitating, chronic disease with no disease-modifying drug approved to date. We discovered LNA043-a derivative of angiopoietin-like 3 (ANGPTL3)-as a potent chondrogenesis inducer using a phenotypic screen with human mesenchymal stem cells. We show that LNA043 promotes chondrogenesis and cartilage matrix synthesis in vitro and regenerates hyaline articular cartilage in preclinical OA and cartilage injury models in vivo. LNA043 exerts at least part of these effects through binding to the fibronectin receptor, integrin α5β1 on mesenchymal stem cells and chondrocytes. In a first-in-human (phase 1), randomized, double-blinded, placebo-controlled, single ascending dose, single-center trial ( NCT02491281 ; sponsored by Novartis Pharmaceuticals), 28 patients with knee OA were injected intra-articularly with LNA043 or placebo (3:1 ratio) either 2 h, 7 d or 21 d before total knee replacement. LNA043 met its primary safety endpoint and showed short serum pharmacokinetics, cartilage penetration and a lack of immunogenicity (secondary endpoints). Post-hoc transcriptomics profiling of cartilage revealed that a single LNA043 injection reverses the OA transcriptome signature over at least 21 d, inducing the expression of hyaline cartilage matrix components and anabolic signaling pathways, while suppressing mediators of OA progression. LNA043 is a novel disease-modifying OA drug candidate that is currently in a phase 2b trial ( NCT04864392 ) in patients with knee OA.

Outcomes of Partial Meniscectomy in Obese Patients: A Systematic Review and Meta-Analysis

OBJECTIVE

Arthroscopic partial meniscectomy (APM) is one of the most commonly performed surgical procedures. However, the indications for APM are controversial and obese patients may have worse outcomes. This study's primary purpose was to investigate differences in outcome after APM associated with elevated body mass index (BMI). Secondary objectives included differences in pathophysiology, surgical complications/failures, or osteoarthritis development.

DESIGN

MEDLINE, EMBASE, and OVID databases were systematically searched for eligible studies reporting on APM outcomes at a minimum of 1 year postoperatively. Studies that did not include BMI categorization were excluded. Meta-analysis was conducted with random-effects modeling where data from at least 2 studies was available.

RESULTS

A total of 16 articles were included. Overweight/obese BMI was associated with worse preoperative Lysholm (mean difference, -6.06 [95% CI, -11.70 to -0.42]) and visual analogue scale pain scores (0.43 [0.07 to 0.79]). Worse postoperative normalized knee-specific patient-reported outcome scores were also associated with obese BMI (-4.57 [-5.33 to -3.81]). There were no significant differences in clinical improvement or osteoarthritis progression among BMI groups. Two studies found higher complication/failure rates, 3 articles associated medial meniscus posterior root tears, and 1 article found differences in gene transcript expression with increased BMI.

CONCLUSIONS

Obesity is associated with worse knee function after APM, and patients with elevated BMI have worse preoperative knee pain and function. However, there is no difference in amount of improvement between elevated and normal BMI patients. Further prospective research is necessary to determine the comparative effectiveness of APM in patients with elevated BMI.

A Microarray Study of Articular Cartilage in Relation to Obesity and Severity of Knee Osteoarthritis

OBJECTIVE

To query the transcript-level changes in the medial and lateral tibial plateau cartilage in tandem with obesity in patients with end-stage osteoarthritis (OA).

DESIGN

Cartilage was obtained from 23 patients (20 obese [body mass index > 30 kg/m²], 3 overweight [body mass index < 30 kg/m²]) at the time of total knee replacement. Cartilage integrity was assessed using Outerbridge scale, while radiographic changes were scored on preoperative X-rays using Kellgren-Lawrence (K-L) classification. RNA was probed for differentially expressed transcripts between medial and lateral compartments using Affymetrix Gene 2.0 ST Array and validated via real-time polymerase chain reaction. Gene ontology and pathway analyses were also queried.

RESULTS

Scoring of cartilage integrity by the Outerbridge scale indicated that the medial and lateral compartments were similar, while scoring by the K-L classification indicated that the medial compartment was more severely damaged than the lateral compartment. We observed a distinct transcript profile with >50% of transcripts unique between medial and lateral compartments. MMP13 and COL2A1 were more highly expressed in medial versus lateral compartment. Polymerase chain reaction confirmed expression of 4 differentially expressed transcripts. Numerous transcripts, biological processes, and pathways were significantly different between overweight and obese patients with a differential response of obesity on medial and lateral compartments.

CONCLUSIONS

Our findings support molecular differences between medial and lateral compartments reflective of the greater severity of OA in the medial compartment. The K-L system better reflected the molecular results than did the Outerbridge. Moreover, the molecular effect of obesity was different between the medial and lateral compartments of the same knee plausibly reflecting the molecular effects of differential biomechanical loading.

Molecular biology of meniscus pathology: Lessons learned from translational studies and mouse models

Injury to any individual structure in the knee interrupts the overall function of the joint and initiates a cascade of biological and biomechanical changes whose endpoint is often osteoarthritis (OA). The knee meniscus is an integral component of knee biomechanics and may also contribute to the biological homeostasis of the joint. Meniscus injury altering knee function is associated with a high risk of OA progression, and may also be involved in the initiation of OA. As the relationship between meniscus injury and OA is very complex; despite the availability of transcript level data on human meniscus injury and meniscus mediated OA, mechanistic studies are lacking, and available human data are difficult to validate in the absence of patient-matched noninjured control tissues. As similarities exist between human and mouse knee joint structure and function, investigators have begun to use cutting-edge genetic and genomic tools to examine the usefulness of the mouse as a model to study the intricate relationship between meniscus injury and OA. In this review, we use evidence from human meniscus research to identify critical barriers hampering our understanding of meniscus injury induced OA and discuss strategies to overcome these barriers, including those that can be examined in a mouse model of injury-mediated OA.

Gene Expression in Meniscal Tears at the Time of Arthroscopic Partial Meniscectomy Predicts the Progression of Osteoarthritis Within 6 Years of Surgery

Background:

While knees with meniscal tears are associated with a heightened risk of developing osteoarthritis (OA), it is difficult to predict which patients are at the greatest risk for OA. Gene signatures in menisci that are resected during arthroscopic partial meniscectomy (APM) may provide insight into the risk of OA progression.

Hypothesis:

Meniscal gene signatures at the time of APM will predict radiographic OA progression.

Study Design:

Case series; Level of evidence, 4.

Methods:

Meniscal fragments were collected from 38 patients without OA during clinically indicated APM of the medial meniscus. The expression of 28 candidate genes with known roles in cartilage homeostasis, OA, extracellular matrix degradation, and obesity was assessed by quantitative real-time polymerase chain reaction. Weightbearing radiographs obtained before surgery and at final follow-up were graded by a musculoskeletal radiologist using the Kellgren-Lawrence classification of OA. The association of meniscal gene expression at baseline with the progression of radiographic OA was determined.

Results:

Gene expression and baseline and follow-up radiographic data were available from 31 patients (81.6%) at a mean follow-up of 6.2 ± 1.3 years. Patients without OA progression had significantly higher expression of 7 genes: MMP9 (5.1-fold; P = .002), IL8 (2.9-fold; P = .016), CCL3 (3.7-fold; P = .032), CCL3L1 (4.5-fold; P = .008), CXCL6 (6.2-fold; P = .010), LEP (5.2-fold; P = .004), and RETN (46-fold; P = .008).

Conclusion:

Gene expression in the meniscus at the time of APM may be associated with the risk for progression of OA after surgery. Elevated expression of the aforementioned genes may reflect a chondroprotective response. Stratifying the risk for OA progression after APM could facilitate targeted interventions to delay or prevent the development of OA. Further studies in a larger cohort with an extended follow-up, and inclusion of additional genes, are warranted to better characterize this association.

Critical Roles of ELVOL4 and IL-33 in the Progression of Obesity-Related Cardiomyopathy via Integrated Bioinformatics Analysis

The molecular mechanisms underlying obesity-related cardiomyopathy (ORCM) progression involve multiple signaling pathways, and the pharmacological treatment for ORCM is still limited. Thus, it is necessary to explore new targets and develop novel therapies. Microarray analysis for gene expression profiles using different bioinformatics tools has been an effective strategy for identifying novel targets for various diseases. In this study, we aimed to explore the potential genes related to ORCM using the integrated bioinformatics analysis. The GSE18897 (whole blood expression profiling of obese diet-sensitive, obese diet-resistant, and lean human subjects) and GSE47022 (regular weight C57BL/6 and diet-induced obese C57BL/6 mice) were used for bioinformatics analysis. Weighted gene co-expression network analysis (WGCNA) of GSE18897 was employed to investigate gene modules that were strongly correlated with clinical phenotypes. Gene Ontology (GO) functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed on the co-expression genes. The expression levels of the hub genes were validated in the clinical samples. Yellow co-expression module of WGCNA in GSE18897 was found to be significantly related to the caloric restriction treatment. In addition, GO functional enrichment analysis and KEGG pathway analysis were performed on the co-expression genes in yellow co-expression module, which showed an association with oxygen transport and the porphyrins pathway. Overlap analysis of yellow co-expression module genes from GSE18897 andGSE47022 revealed six upregulated genes, and further experimental validation results showed that elongation of very-long-chain fatty acids protein 4 (ELOVL4), matrix metalloproteinase-8 (MMP-8), and interleukin-33 (IL-33) were upregulated in the peripheral blood from patients with ORCM compared to that in the controls. The bioinformatics analysis revealed that ELOVL4 expression levels are positively correlated with that of IL-33. Collectively, using WGCNA in combination with integrated bioinformatics analysis, the hub genes of ELVOL4 and IL-33 might serve as potential biomarkers for diagnosis and/or therapeutic targets for ORCM. The detailed roles of ELVOL4 and IL-33 in the pathophysiology of ORCM still require further investigation.

Duration of symptoms prior to partial meniscectomy is not associated with the expression of osteoarthritis genes in the injured meniscus

While there is emerging data on how duration of symptoms prior to surgery relates to outcomes of patients undergoing arthroscopic partial meniscectomy, little is known about how duration of symptoms relates to the biology of the knee in these patients. The purpose of this study was to test the hypothesis that duration of symptoms prior to arthroscopic partial meniscectomy is associated with expression of osteoarthritis (OA)-related genes in the meniscus. We collected resected meniscus from patients (N = 76) undergoing clinically indicated arthroscopic partial meniscectomy from knees without advanced degenerative changes. RNA from 64 patients was analyzed for 28 candidate OA transcripts by real-time polymerase chain reaction (PCR). RNA was also probed for identification of novel genes by RNA microarray in 12 patients followed by validation of selected candidates by real-time PCR. The association of gene expression with duration of symptoms prior to surgery was tested. Additional screening was performed with known OA genetic risk alleles assembled from published literature and with gene transcripts differentially expressed between non-OA and OA cartilage and menisci. Our data revealed that duration of symptoms did not predict expression of OA genes in the meniscus, other than limited association with CXCL3, BMP2, and HLA-DQA1. Microarray identified new genes and pathways with unknown role(s) in meniscus injury and OA and validation of a subset of genes by real-time PCR showed expression pattern highly concordant with the microarray data. While duration of symptoms prior to arthroscopic partial meniscectomy does not significantly alter the expression of OA related genes, the association with novel genes and pathways deserves further investigation.

A Comprehensive Genome-Wide and Phenome-Wide Examination of BMI and Obesity in a Northern Nevadan Cohort

The aggregation of Electronic Health Records (EHR) and personalized genetics leads to powerful discoveries relevant to population health. Here we perform genome-wide association studies (GWAS) and accompanying phenome-wide association studies (PheWAS) to validate phenotype-genotype associations of BMI, and to a greater extent, severe Class 2 obesity, using comprehensive diagnostic and clinical data from the EHR database of our cohort. Three GWASs of 500,000 variants on the Illumina platform of 6,645 Healthy Nevada participants identified several published and novel variants that affect BMI and obesity. Each GWAS was followed with two independent PheWASs to examine associations between extensive phenotypes (incidence of diagnoses, condition, or disease), significant SNPs, BMI, and incidence of extreme obesity. The first GWAS examines associations with BMI in a cohort with no type 2 diabetics, focusing exclusively on BMI. The second GWAS examines associations with BMI in a cohort that includes type 2 diabetics. In the second GWAS, type 2 diabetes is a comorbidity, and thus becomes a covariate in the statistical model. The intersection of significant variants of these two studies is surprising. The third GWAS is a case vs. control study, with cases defined as extremely obese (Class 2 or 3 obesity), and controls defined as participants with BMI between 18.5 and 25. This last GWAS identifies strong associations with extreme obesity, including established variants in the FTO and NEGR1 genes, as well as loci not yet linked to obesity. The PheWASs validate published associations between BMI and extreme obesity and incidence of specific diagnoses and conditions, yet also highlight novel links. This study emphasizes the importance of our extensive longitudinal EHR database to validate known associations and identify putative novel links with BMI and obesity.

Identification of Pivotal Genes and Pathways in Osteoarthritic Degenerative Meniscal Lesions via Bioinformatics Analysis of the GSE52042 Dataset

Background

To better understand the process of osteoarthritic degenerative meniscal lesions (DMLs) formation, this study analyzed the dataset GSE52042 using bioinformatics methods to identify the pivotal genes and pathways related to osteoarthritic DMLs.

Material/Methods

The GSE52042 dataset, comprising diseased meniscus samples and healthier meniscus samples, was downloaded and the differentially-expressed genes (DEGs) were extracted. The reactome pathways assessment and functional analysis were performed using the “ClusterProfiler” package and “ReactomePA” package of Bioconductor. The protein–protein interaction network was constructed, followed by the extraction of hub genes and modules.

Results

A set of 154 common DEGs, including 64 upregulated DEGs and 90 downregulated DEGs, were obtained. GO analysis suggested that the DEGs primarily participated in positive regulation of the mitotic cell cycle and extracellular matrix organization. Reactome pathway analysis showed that the DEGs were predominantly enriched in TP53, which regulates transcription of genes involved in G2 cell cycle arrest and extracellular matrix organization. The top 10 hub genes were TYMS, AURKA, CENPN, NUSAP1, CENPM, TPX2, CDK1, UBE2C, BIRC5, and CCNB1. The genes in the 2 modules were primarily associated with M Phase and keratan sulfate degradation.

Conclusions

A series of pivotal genes and reactome pathways were identified elucidate the molecular mechanisms involved in the formation of osteoarthritic DMLs and to discover potential therapeutic targets.

A Co-expression Analysis of the Placental Transcriptome in Association With Maternal Pre-pregnancy BMI and Newborn Birth Weight

Maternal body mass index (BMI) before pregnancy is known to affect both fetal growth and later-life health of the newborn, yet the implicated molecular mechanisms remain largely unknown. As the master regulator of the fetal environment, the placenta is a valuable resource for the investigation of processes involved in the developmental programming of metabolic health. We conducted a genome-wide placental transcriptome study aiming at the identification of functional pathways representing the molecular link between maternal BMI and fetal growth. We used RNA microarray (Agilent 8 × 60 K), medical records, and questionnaire data from 183 mother-newborn pairs from the ENVIRONAGE birth cohort study (Flanders, Belgium). Using a weighted gene co-expression network analysis, we identified 17 correlated gene modules. Three of these modules were associated with both maternal pre-pregnancy BMI and newborn birth weight. A gene cluster enriched for genes involved in immune response and myeloid cell differentiation was positively associated with maternal BMI and negatively with low birth weight. Two other gene modules, upregulated in association with maternal BMI as well as birth weight, were involved in processes related to organ and tissue development, with blood vessel morphogenesis and extracellular matrix structure as top Gene Ontology terms. In line with this, erythrocyte-, angiogenesis-, and extracellular matrix-related genes were among the identified hub genes. The association between maternal BMI and newborn weight was significantly mediated by gene expression for 5 of the hub genes (FZD4, COL15A1, GPR124, COL6A1, and COL1A1). As some of the identified hub genes have been linked to obesity in adults, our observation in placental tissue suggests that biological processes may be affected from prenatal life onwards, thereby identifying new molecular processes linking maternal BMI and fetal metabolic programming.

Microarray analysis of the molecular mechanisms associated with age and body mass index in human meniscal injury

The aim of the present study was to identify genes and functional pathways associated with meniscal injuries affected by age or body mass index (BMI) using microarray analysis. The GSE45233 gene expression dataset with 12 injured meniscus samples associated with age and BMI and GSE66635 dataset with 12 injured and 12 normal meniscus samples were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were identified based on age or BMI in GSE45233. DEGs between injured and normal meniscus samples in GSE66635 were also identified. Common DEGs between GSE45233 and GSE66635 were identified as feature genes associated with age or BMI, followed by protein-protein interaction (PPI) network and functional pathway enrichment analyses for the feature genes. Finally, the GSE51588 genome-wide expression profile was then downloaded from the GEO database to validate the results. A total of 1,328 DEGs were identified. Of these, 28 age-associated and 20 BMI-associated meniscal injury genes were obtained. B-cell lymphoma-2 (Bcl-2) and matrix metalloproteinase-14 were identified as hub genes in the PPI networks. Functional pathway enrichment analysis revealed that vascular endothelial growth factor A (VEGFA), transferrin (TF) and Bcl-2 were involved in the hypoxia-inducible factor 1 signaling pathway. TF was involved in the mineral absorption function pathway associated with BMI. Additionally, TF and VEGFA were identified to be overlapping candidate genes of GSE45233 and GSE66635, and DEGs in GSE51588. Therefore, VEGFA, TF, and Bcl-2 may be important genes for human meniscal injuries. Additional evaluations of these results are required.

Nonalcoholic fatty liver disease and gastric bypass surgery regulate serum and hepatic levels of pyruvate kinase isoenzyme M2

Treatment of nonalcoholic fatty liver disease (NAFLD) focuses on the underlying metabolic syndrome, and Roux-en-Y gastric bypass surgery (RYGB) remains one of the most effective options. In rodents and human patients, RYGB induces an increase in the gene and protein expression levels of the M2 isoenzyme of pyruvate kinase (PKM2) in the jejunum. Since PKM2 can be secreted in the circulation, our hypothesis was that the circulating levels of PKM2 increase after RYGB. Our data, however, revealed an unexpected finding and a potential new role of PKM2 for the natural history of metabolic syndrome and NAFLD. Contrary to our initial hypothesis, RYGB-treated patients had decreased PKM2 blood levels compared with a well-matched group of patients with severe obesity before RYGB. Interestingly, PKM2 serum concentration correlated with body mass index before but not after the surgery. This prompted us to evaluate other potential mechanisms and sites of PKM2 regulation by the metabolic syndrome and RYGB. We found that in patients with NAFLD and nonalcoholic steatohepatitis (NASH), the liver had increased PKM2 expression levels, and the enzyme appears to be specifically localized in Kupffer cells. The study of murine models of metabolic syndrome and NASH replicated this pattern of expression, further suggesting a metabolic link between hepatic PKM2 and NAFLD. Therefore, we conclude that PKM2 serum and hepatic levels increase in both metabolic syndrome and NAFLD and decrease after RYGB. Thus, PKM2 may represent a new target for monitoring and treatment of NAFLD.

Transcriptomic analysis of synovial extracellular RNA following knee trauma: A pilot study

Traumatic knee injuries often result in damage to articular cartilage and other joint structures. Such trauma is a strong risk factor for the future development and progression of osteoarthritis (OA). The molecular mechanisms and signaling pathways modulating response to knee joint trauma remain unclear. Moreover, investigations of biomarkers influencing responses have been targeted rather than broad, unbiased discovery studies. Herein, we characterize the complete complement of extracellular RNA (exRNA) in the synovial fluid of 14 subjects following knee injury. Fluid was collected during surgery from the injured knees, and from the contralateral knee in a subset, undergoing surgical repair of the ACL and/or meniscal repair/debridement. Arthroscopic grading of chondral damage in four knee compartments was performed using the Outerbridge classification. exRNA was extracted and subjected to massively parallel total RNA sequencing. Differential abundance of RNA was calculated between the subject cohorts of injured and non-injured knee, average Outerbridge score ≥0.5 and less, and chronic and acute injury duration defined as ≤4 months till surgery or longer. Overall, expression of several thousand genes was identified in the synovial fluid. Furthermore, differential expression analysis suggests a role of exRNA fragments of matrix metalloproteinases and skeletal muscle fiber genes in the response to traumatic injury. Together, these data suggest that high-throughput approaches can indicate exRNA molecular signatures following knee trauma. Future studies are required to more fully characterize the biological roles of these exRNA and the cadence of their respective release that may lead to translational treatment options for post-traumatic OA. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1659-1665, 2018.

Biomarkers for equine joint injury and osteoarthritis

We report the results of a symposium aimed at identifying validated biomarkers that can be used to complement clinical observations for diagnosis and prognosis of joint injury leading to equine osteoarthritis (OA). Biomarkers might also predict pre-fracture change that could lead to catastrophic bone failure in equine athletes. The workshop was attended by leading scientists in the fields of equine and human musculoskeletal biomarkers to enable cross-disciplinary exchange and improve knowledge in both. Detailed proceedings with strategic planning was written, added to, edited and referenced to develop this manuscript. The most recent information from work in equine and human osteoarthritic biomarkers was accumulated, including the use of personalized healthcare to stratify OA phenotypes, transcriptome analysis of anterior cruciate ligament (ACL) and meniscal injuries in the human knee. The spectrum of "wet" biomarker assays that are antibody based that have achieved usefulness in both humans and horses, imaging biomarkers and the role they can play in equine and human OA was discussed. Prediction of musculoskeletal injury in the horse remains a challenge, and the potential usefulness of spectroscopy, metabolomics, proteomics, and development of biobanks to classify biomarkers in different stages of equine and human OA were reviewed. The participants concluded that new information and studies in equine musculoskeletal biomarkers have potential translational value for humans and vice versa. OA is equally important in humans and horses, and the welfare issues associated with catastrophic musculoskeletal injury in horses add further emphasis to the need for good validated biomarkers in the horse. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:823-831, 2018.

Advantages of RNA-seq compared to RNA microarrays for transcriptome profiling of anterior cruciate ligament tears

Microarrays and RNA-seq are at the forefront of high throughput transcriptome analyses. Since these methodologies are based on different principles, there are concerns about the concordance of data between the two techniques. The concordance of RNA-seq and microarrays for genome-wide analysis of differential gene expression has not been rigorously assessed in clinically derived ligament tissues. To demonstrate the concordance between RNA-seq and microarrays and to assess potential benefits of RNA-seq over microarrays, we assessed differences in transcript expression in anterior cruciate ligament (ACL) tissues based on time-from-injury. ACL remnants were collected from patients with an ACL tear at the time of ACL reconstruction. RNA prepared from torn ACL remnants was subjected to Agilent microarrays (N = 24) and RNA-seq (N = 8). The correlation of biological replicates in RNA-seq and microarrays data was similar (0.98 vs. 0.97), demonstrating that each platform has high internal reproducibility. Correlations between the RNA-seq data and the individual microarrays were low, but correlations between the RNA-seq values and the geometric mean of the microarrays values were moderate. The cross-platform concordance for differentially expressed transcripts or enriched pathways was linearly correlated (r = 0.64). RNA-Seq was superior in detecting low abundance transcripts and differentiating biologically critical isoforms. Additional independent validation of transcript expression was undertaken using microfluidic PCR for selected genes. PCR data showed 100% concordance (in expression pattern) with RNA-seq and microarrays data. These findings demonstrate that RNA-seq has advantages over microarrays for transcriptome profiling of ligament tissues when available and affordable. Furthermore, these findings are likely transferable to other musculoskeletal tissues where tissue collection is challenging and cells are in low abundance. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:484-497, 2018.

The Effect of Body Mass Index on Clinical Outcomes in Patients Without Radiographic Evidence of Degenerative Joint Disease After Arthroscopic Partial Meniscectomy

PURPOSE

To examine the effect of obesity on clinical outcomes at 1 year after arthroscopic partial meniscectomy.

METHODS

We conducted a secondary analysis of the ChAMP (Chondral Lesions and Meniscus Procedures) randomized controlled trial (N = 256). The visual analog scale for pain, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS), range of motion, and presence of effusion were assessed preoperatively and at 1 year after arthroscopic partial meniscectomy. Body mass index was categorized as normal weight, 24.99 or less; overweight, 25 to 29.99; or obese, 30 or greater. Analysis of variance or the Cochran-Mantel-Haenszel test was used to examine differences in clinical outcomes between body mass index categories, and mean ± standard deviation or number (percentage) is reported.

RESULTS

Preoperatively, obese patients had worse WOMAC pain (56.2 ± 17.2 vs 61.3 ± 17.2, P = .02), WOMAC physical function (55.8 ± 17.1 vs 62.8 ± 17.1, P = .004), pain visual analog scale (4.9 ± 2.1 vs 4.2 ± 1.9, P = .01), KOOS pain (49.5 ± 14.9 vs 54.0 ± 15.1, P = .02), and KOOS quality-of-life (27.9 ± 18.3 vs 36.9 ± 17.0, P = .001) scores, as well as decreased flexion (121.8° ± 22.6° vs 132.3° ± 16.5°, P = .003), compared with normal-weight patients. Overweight patients (n = 51 [51.5%], P = .03) and obese patients (n = 56 [52.8%], P = .002) were more likely to have knee effusion before surgery than normal-weight patients (n = 17 [34%]). At 1 year after surgery, overweight (130.2° ± 7.7°, P = .03) and obese (128.1° ± 7.1°, P = .003) patients had decreased flexion compared with normal-weight patients (134.5° ± 8.3°).

CONCLUSIONS

Obese patients had worse pain, physical functioning, and quality-of-life scores, as well as decreased flexion, compared with normal-weight patients before arthroscopic partial meniscectomy. At 1 year after arthroscopic partial meniscectomy, there were no statistically significant differences in clinical outcomes but obesity was associated with decreased knee flexion.

LEVEL OF EVIDENCE

Level II, prospective comparative trial.

Using mouse models to investigate the pathophysiology, treatment, and prevention of post-traumatic osteoarthritis

Post-traumatic osteoarthritis (PTOA) is defined by its development after joint injury. Factors contributing to the risk of PTOA occurring, the rate of progression, and degree of associated disability in any individual, remain incompletely understood. What constitutes an "OA-inducing injury" is not defined. In line with advances in the traumatic brain injury field, we propose the scope of PTOA-inducing injuries be expanded to include not only those causing immediate structural damage and instability (Type I), but also those without initial instability/damage from moderate (Type II) or minor (Type III) loading severity. A review of the literature revealed this full spectrum of potential PTOA subtypes can be modeled in mice, with 27 Type I, 6 Type II, and 4 Type III models identified. Despite limitations due to cartilage anatomy, joint size, and bio-fluid availability, mice offer advantages as preclinical models to study PTOA, particularly genetically modified strains. Histopathology was the most common disease outcome, cartilage more frequently studied than bone or synovium, and meniscus and ligaments rarely evaluated. Other methods used to examine PTOA included gene expression, protein analysis, and imaging. Despite the major issues reported by patients being pain and biomechanical dysfunction, these were the least commonly measured outcomes in mouse models. Informative correlations of simultaneously measured disease outcomes in individual animals, was rarely done in any mouse PTOA model. This review has identified knowledge gaps that need to be addressed to increase understanding and improve prevention and management of PTOA. Preclinical mouse models play a critical role in these endeavors. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:424-439, 2017.

The biology of meniscal pathology in osteoarthritis and its contribution to joint disease: beyond simple mechanics

The meniscal cartilages in the knee function to improve congruity of the medial and lateral femoro-tibial joints and play critical roles in load distribution and joint stability. Meniscal tears of various configurations are one of the most common conditions of the knee and are associated with an increased risk of developing osteoarthritis (OA). While this risk has been largely attributed to loss of the biomechanical functions of the menisci, there is accumulating evidence suggesting that other aspects of meniscal biology may play a role in determining the long-term consequences of meniscal damage for joint health. In this narrative review, we examine the existing literature and present some new data implicating synthesis and secretion of enzymes and other pro-catabolic mediators by injured and degenerate menisci, contributing to the pathological change in other knee joint tissues in OA.

Traumatic and Degenerative Meniscus Tears Have Different Gene Expression Signatures

BACKGROUND

Meniscus tears are classified as traumatic or degenerative based on the tear pattern. There is little evidence demonstrating biological differences between the 2 tear types.

HYPOTHESIS

Gene expression signatures in the injured meniscus are different between traumatic (vertical) and degenerative (complex, horizontal, or flap) tears.

STUDY DESIGN

Controlled laboratory study.

METHODS

Samples of the torn meniscus from the white-white zone were removed at the time of clinically indicated partial meniscectomy from 48 patients (37 with degenerative tears and 11 with traumatic tears). mRNA expression in the injured menisci was measured by quantitative real-time polymerase chain reaction for selected molecular markers of osteoarthritis, inflammation, and cartilage homeostasis (eg, cytokines/chemokines, aggrecanases/metalloproteinases, transcription factors, cartilage matrix genes, and adipokines). The tear pattern (traumatic or degenerative) and location (medial or lateral) were recorded for each patient. Gene expression differences between degenerative and traumatic tears were computed after adjusting for patients' age, sex, and body mass index and for location of the resected meniscus (medial/lateral).

RESULTS

Gene expression in meniscus tears varied by pattern. Chemokines ( IL8 [ P < .001] and CXCL6 [ P < .001]) and matrix metalloproteinases ( MMP1 [ P = .011] and MMP3 [ P = .016]) were expressed at a significantly higher level in traumatic tears compared with degenerative tears. In contrast, COL1A1 was expressed at a lower level in traumatic tears compared with degenerative tears ( P = .058). None of the genes tested demonstrated significant differences between medial and lateral meniscus tears.

CONCLUSION

Traumatic meniscus tears overall exhibited a higher inflammatory/catabolic response as evidenced by higher levels of chemokine and matrix metalloproteinase expression than degenerative tears. These findings suggest that there is a (molecular) biological distinction between traumatic and degenerative tears.

CLINICAL RELEVANCE

The catabolic/inflammatory differences between traumatic and degenerative tears may be relevant to treatment decisions regarding the meniscus as well as advance our understanding of how meniscus tears relate to the development of knee osteoarthritis.

Gene expression in human meniscal tears has limited association with early degenerative changes in knee articular cartilage

Purpose/Aim: Meniscus tears are a common injury to the knee associated with the development of osteoarthritis. Gene expression in the injured meniscus may be associated with early degeneration in the articular cartilage. The purpose of this study was to test the hypothesis that gene expression in meniscus tears is associated with early degenerative changes in the articular cartilage at the time of partial meniscectomy.

MATERIALS AND METHODS

Torn meniscus was removed at the time of partial meniscectomy in 68 patients without radiographic osteoarthritis. Meniscal mRNA expression was measured by quantitative PCR for multiple molecular markers of osteoarthritis and cartilage homeostasis. The presence of early degenerative changes in the knee was recorded by X-ray (N = 63), magnetic resonance imaging (MRI, N = 48), and arthroscopy (N = 63). Gene expression was tested for correlation with the presence/absence of degenerative changes after adjusting for age, sex, and body mass index.

RESULTS

Overall gene expression varied significantly with degenerative changes based on X-ray (P = 0.047) and MRI (P = 0.018). The linear combination of gene variation was also significant. However, only adiponectin (ADIPOQ) (P = 0.015) was expressed at a significantly lower level in patients with chondrosis on MRI, while the expression of ADIPOQ (P = 0.035) and resistin (RETN) (P = 0.017) was higher in patients with early degenerative changes on X-ray. None of the genes varied significantly with presence/absence of chondrosis as measured by arthroscopy.

CONCLUSIONS

There is an overall association of gene expression in meniscal tears to early degenerative changes in the knee, but only a limited number of specific genes demonstrate this relationship. The roles of adiponectin and resistin in knee injury and osteoarthritis deserve further study.

Obesity and Knee Arthroscopy – a Review

Obesity is currently a global epidemic, often referred to as “globesity”, impacting the life of millions worldwide. A risk factor for many diseases, obesity can also be linked to developing intra-articular lesions of the knee, affecting the menisci, ligaments and cartilage. Furthermore, obesity has been shown to influence the outcome of surgical interventions, including those of the musculoskeletal system. Although many studies addressed the relationship of obesity and joint replacement, articles relating to arthroscopy and obesity, and knee arthroscopy in particular, are a bit scarcer. The majority of data suggest that an increase in BMI leads to a similar increase in the rates of intra- and postoperative complications, and most authors agree that a higher body mass index can influence both the procedure itself and its outcomes, including the subjective results reported by the patients. Still, some studies show different results, especially in patients that are overweight or with low-grade obesity, where the outcomes are comparable to those of the non-obese population. Thus, it can be concluded that obesity is an important patient characteristic that needs to be taken into consideration when planning, performing, and assessing the results of knee arthroscopy.

Meniscal biology in health and disease

The knee is a fascinating yet complex joint. Researchers and clinicians agree that the joint is an organ comprised of highly specialized intrinsic and extrinsic tissues contributing to both health and disease. Key to the function and movement of the knee are the menisci, exquisite fibrocartilage structures that are critical structures for maintaining biological and biomechanical integrity of the joint. The biological/physiological functions of the menisci must be understood at the tissue, cellular and even molecular levels in order to determine clinically relevant methods for assessing it and influencing it. By investigating normal and pathological functions at the basic science level, we can begin to translate data to patients. The objective of this article is to provide an overview of this translational pathway so that progression toward improved diagnostic, preventative, and therapeutic strategies can be effectively pursued. We have thoroughly examined the pathobiological, biomarker, and imaging aspects of meniscus research. This translational approach can be effective toward optimal diagnosis, prevention, and treatment for the millions of patients who suffer from meniscal disorders each year.

Changes in Transcriptome-Wide Gene Expression of Anterior Cruciate Ligament Tears Based on Time From Injury

BACKGROUND

Anterior cruciate ligament (ACL) tears are a common injury. The healing potential of the injured ACL is poorly understood and is considered limited. Therefore, most ACL tears that are treated surgically undergo reconstruction rather than repair. However, there has been renewed interest recently in repairing ACL tears despite unanswered questions regarding the healing capacity of the ACL.

HYPOTHESIS

Gene expression in the injured ACL varies with time from injury.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Transcriptome-wide expression profiles of 24 human ACL remnants recovered at the time of surgical reconstruction were analyzed using the Agilent human 8x60K microarray platform. Gene ontology was performed on differentially expressed transcripts based on time from injury (acute, <3 months; intermediate, 3-12 months; chronic, >12 months). A subset of transcripts with large fold changes in expression between any 2 categories was validated via microfluidic digital polymerase chain reaction.

RESULTS

Numerous transcripts representing important biological processes were differentially expressed by time from injury. The most significant changes were noted between the acute and chronic groups. Expression of several extracellular matrix genes- namely, POSTN, COL5A1, COL1A1, and COL12A1-was lower in the chronic tears compared with acute and intermediate tears. In acute tears, processes representing angiogenesis and stem cell differentiation were affected. In intermediate tears, processes representing stem cell proliferation concomitant with cellular component organization/cellular localization were altered. In ACL tears more than 12 months out from injury, processes denoting myosin filament organization, cellular component organization/cell localization, and extracellular matrix organization were affected.

CONCLUSION

These findings are consistent with initial repair activity in the injured ACL, which declines with time from injury. Individual genes identified in this study, such as periostin, deserve further investigation into their role in tissue repair.

CLINICAL RELEVANCE

The decreased healing capacity of ACL tears over time is relevant to the development of effective techniques for repairing ACL tears and may have some significance for ACL reconstruction techniques as well. The potential for healing appears to be greatest in acute ACL tears, suggesting this window should be the focus of research for ACL repair.

Meniscal Allograft Transplantation Does Not Prevent or Delay Progression of Knee Osteoarthritis

Background

Meniscal tears are common knee injuries. Meniscal allograft transplantation (MAT) has been advocated to alleviate symptoms and delay osteoarthritis (OA) after meniscectomy. We investigated (1) the long-term outcome of MAT as a treatment of symptomatic meniscectomy, (2) most important factors affecting survivorship and (3) OA progression.

Methods

From 1989 till 2013, 329 MAT were performed in 313 patients. Clinical and radiographic results and MAT survival were evaluated retrospectively. Failure was defined as conversion to knee arthroplasty (KA) or total removal of the MAT.

Results

Mean age at surgery was 33 years (15–57); 60% were males. No-to-mild cartilage damage was found in 156 cases, moderate-to-severe damage in 130. Simultaneous procedures in 118 patients included cartilage procedures, osteotomy or ACL-reconstruction. At a mean follow-up of 6.8 years (0.2–24.3years), 5 patients were deceased and 48 lost (14.6%), 186 MAT were in situ (56.5%) whilst 90 (27.4%) had been removed, including 63 converted to a KA (19.2%). Cumulative allograft survivorship was 15.1% (95% CI:13.9–16.3) at 24.0 years. In patients <35 years at surgery, survival was significantly better (24.1%) compared to ≥35 years (8.0%) (p = 0.017). In knees with no-to-mild cartilage damage more allografts survived (43.0%) compared to moderate-to-severe damage (6.6%) (p = 0.003). Simultaneous osteotomy significantly deteriorated survival (0% at 24.0 years) (p = 0.010). 61% of patients underwent at least one additional surgery (1–11) for clinical symptoms after MAT. Consecutive radiographs showed significant OA progression at a mean of 3.8 years (p<0.0001). Incremental Kellgren-Lawrence grade was +1,1 grade per 1000 days (2,7yrs).

Conclusions

MAT did not delay or prevent tibiofemoral OA progression. 19.2% were converted to a knee prosthesis at a mean of 10.3 years. Patients younger than 35 with no-to-mild cartilage damage may benefit from MAT for relief of symptoms (survivorship 51.9% at 20.2 years), but patients and healthcare payers and providers should be aware of the high number of surgical re-interventions.

Free fatty acid palmitate activates unfolded protein response pathway and promotes apoptosis in meniscus cells

INTRODUCTION

Obesity is the major risk factor for the development of osteoarthritis (OA); however, the mechanisms involved are not clearly understood. Obesity is associated with increased production of adipokine and elevated levels of circulating free fatty acids (FFA). A recent study has shown that saturated fatty acid palmitate induced pro-inflammatory and pro-apoptotic pathways in chondrocytes. Meniscus has been shown to be more susceptible than articular cartilage to catabolic stimuli. Thus, the aim of this study was to determine the effect of FFA (specifically, palmitate) on meniscus cells.

METHODS

Cultured primary porcine meniscus cells were stimulated with 500 μM FFA (palmitate and oleate) for 24 h to induce endoplasmic reticulum (ER) stress. After treatment, cell lysates were prepared and immunoblotted for C/EBP homologous protein (CHOP). To determine the activation of unfolded protein response (UPR) signaling, cell lysates were probed for cJun n-terminal kinase (JNK), cleaved caspase -3 and Xbp-1s, an alternative mRNA splicing product generated due to Ire1α activation.

RESULTS

Treatment of isolated primary meniscus cells with palmitate but not oleate induced expression of CHOP and Xbp-1s. Palmitate treatment of meniscus cells also activated JNK and increased expression of caspase-3, thus promoting apoptosis in meniscus cells.

CONCLUSIONS

Palmitate induces ER stress and promotes apoptotic pathways in meniscus cells. This is the first study to establish ER stress as a key metabolic mechanistic link between obesity and OA, in addition to (or operating with) biomechanical factors.

A phylogenomic analysis of the role and timing of molecular adaptation in the aquatic transition of cetartiodactyl mammals

Recent studies have reported multiple cases of molecular adaptation in cetaceans related to their aquatic abilities. However, none of these has included the hippopotamus, precluding an understanding of whether molecular adaptations in cetaceans occurred before or after they split from their semi-aquatic sister taxa. Here, we obtained new transcriptomes from the hippopotamus and humpback whale, and analysed these together with available data from eight other cetaceans. We identified more than 11 000 orthologous genes and compiled a genome-wide dataset of 6845 coding DNA sequences among 23 mammals, to our knowledge the largest phylogenomic dataset to date for cetaceans. We found positive selection in nine genes on the branch leading to the common ancestor of hippopotamus and whales, and 461 genes in cetaceans compared to 64 in hippopotamus. Functional annotation revealed adaptations in diverse processes, including lipid metabolism, hypoxia, muscle and brain function. By combining these findings with data on protein-protein interactions, we found evidence suggesting clustering among gene products relating to nervous and muscular systems in cetaceans. We found little support for shared ancestral adaptations in the two taxa; most molecular adaptations in extant cetaceans occurred after their split with hippopotamids.