Mitonuclear epistasis involving TP63 and haplogroup Uk: Risk of rapid progression of knee OA in patients from the OAI

OBJECTIVE

To investigate genetic interactions between mitochondrial deoxyribonucleic acid (mtDNA) haplogroups and nuclear single nucleotide polymorphisms (nSNPs) to analyze their impact on the development of the rapid progression of knee osteoarthritis (OA).

DESIGN

A total of 1095 subjects from the Osteoarthritis Initiative, with a follow-up time of at least 48-months, were included. Appropriate statistical approaches were performed, including generalized estimating equations adjusting for age, gender, body mass index, contralateral knee OA, Western Ontario and McMaster Universities Osteoarthritis Index pain, previous injury in target knee and the presence of the mtDNA variant m.16519C. Additional genomic data consisted in the genotyping of Caucasian mtDNA haplogroups and eight nSNPs previously associated with the risk of knee OA in robust genome-wide association studies.

RESULTS

The simultaneous presence of the G allele of rs12107036 at TP63 and the haplogroup Uk significantly increases the risk of a rapid progression of knee OA (odds ratio = 1.670; 95% confidence interval [CI]: 1.031-2.706; adjusted p-value = 0.027). The assessment of the population attributable fraction showed that the highest proportion of rapid progressors was under the simultaneous presence of the G allele of rs12107036 and the haplogroup Uk (23.4%) (95%CI: 7.89-38.9; p-value < 0.05). The area under the curve of the cross-validation model (0.730) was very similar to the obtained for the predictive model (0.735). A nomogram was constructed to help clinicians to perform clinical trials or epidemiologic studies.

CONCLUSIONS

This study demonstrates the existence of a mitonuclear epistasis in OA, providing new mechanisms by which nuclear and mitochondrial variation influence the susceptibility to develop different OA phenotypes.

Metabolic syndrome is not associated with erosive hand osteoarthritis: a cross-sectional study using data from the PROCOAC cohort

To delineate the phenotype of erosive hand osteoarthritis (EHOA) in a Spanish population and assess its correlation with metabolic syndrome. We conducted a cross-sectional study using baseline data from the Prospective Cohort of Osteoarthritis from A Coruña (PROCOAC). Demographic and clinical variables, obtained through questionnaires, clinical examinations, and patient analytics, were compared among individuals with hand OA, with and without EHOA. We performed appropriate univariate and multivariate stepwise regression analyses using SPSS v28. Among 1039 subjects diagnosed with hand OA, 303 exhibited EHOA. Multivariate logistic regression analysis revealed associations with inflamed joints, nodular hand OA, and total AUSCAN. Furthermore, the association with a lower prevalence of knee OA remained significant. The influence of metabolic syndrome (MetS) on EHOA patients was analyzed by including MetS as a covariate in the model. It was observed that MetS does not significantly impact the presence of EHOA, maintaining the effect size of other factors. In conclusion, in the PROCOAC cohort, EHOA is associated with nodular hand OA, inflammatory hand OA, and a higher total AUSCAN. However, EHOA is linked to a lower prevalence of knee OA. Importantly, in our cohort, no relationship was found between EHOA and MetS.

Single nucleotide polymorphism genes and mitochondrial DNA haplogroups as biomarkers for early prediction of knee osteoarthritis structural progressors: use of supervised machine learning classifiers

BACKGROUND

Knee osteoarthritis is the most prevalent chronic musculoskeletal debilitating disease. Current treatments are only symptomatic, and to improve this, we need a robust prediction model to stratify patients at an early stage according to the risk of joint structure disease progression. Some genetic factors, including single nucleotide polymorphism (SNP) genes and mitochondrial (mt)DNA haplogroups/clusters, have been linked to this disease. For the first time, we aim to determine, by using machine learning, whether some SNP genes and mtDNA haplogroups/clusters alone or combined could predict early knee osteoarthritis structural progressors.

METHODS

Participants (901) were first classified for the probability of being structural progressors. Genotyping included SNP genes TP63, FTO, GNL3, DUS4L, GDF5, SUPT3H, MCF2L, and TGFA; mtDNA haplogroups H, J, T, Uk, and others; and clusters HV, TJ, KU, and C-others. They were considered for prediction with major risk factors of osteoarthritis, namely, age and body mass index (BMI). Seven supervised machine learning methodologies were evaluated. The support vector machine was used to generate gender-based models. The best input combination was assessed using sensitivity and synergy analyses. Validation was performed using tenfold cross-validation and an external cohort (TASOAC).

RESULTS

From 277 models, two were defined. Both used age and BMI in addition for the first one of the SNP genes TP63, DUS4L, GDF5, and FTO with an accuracy of 85.0%; the second profits from the association of mtDNA haplogroups and SNP genes FTO and SUPT3H with 82.5% accuracy. The highest impact was associated with the haplogroup H, the presence of CT alleles for rs8044769 at FTO, and the absence of AA for rs10948172 at SUPT3H. Validation accuracy with the cross-validation (about 95%) and the external cohort (90.5%, 85.7%, respectively) was excellent for both models.

CONCLUSIONS

This study introduces a novel source of decision support in precision medicine in which, for the first time, two models were developed consisting of (i) age, BMI, TP63, DUS4L, GDF5, and FTO and (ii) the optimum one as it has one less variable: age, BMI, mtDNA haplogroup, FTO, and SUPT3H. Such a framework is translational and would benefit patients at risk of structural progressive knee osteoarthritis.

mtDNA variability determines spontaneous joint aging damage in a conplastic mouse model

Mitochondria and mtDNA variations contribute to specific aspects of the aging process. Here, we aimed to investigate the influence of mtDNA variation on joint damage in a model of aging using conplastic mice. A conplastic (BL/6^NZB) mouse strain was developed with the C57BL/6JOlaHsd nuclear genome and NZB/OlaHsd mtDNA, for comparison with the original C57BL/6JOlaHsd strain (BL/6^C57). Conplastic (BL/6^NZB) and BL/6^C57 mice were sacrificed at 25, 75, and 90 weeks of age. Hind knee joints were processed for histological analysis and joint pathology graded using the Mankin scoring system. By immunohistochemistry, cartilage expression of markers of autophagy (LC3, Beclin-1, and P62) and markers of senescence (MMP13, beta-Galactosidase, and p16) and proliferation (Ki67) were analyzed. We also measured the expression of 8-oxo-dG and cleaved caspase-3.

Conplastic (BL/6^NZB) mice presented lower Mankin scores at 25, 75, and 90 weeks of age, higher expression of LC3 and Beclin-1 and lower of P62 in cartilage than the original strain. Moreover, the downregulation of MMP13, beta-Galactosidase, and p16 was detected in cartilage from conplastic (BL/6^NZB) mice, whereas higher Ki67 levels were detected in these mice. Finally, control BL/6^C57 mice showed higher cartilage expression of 8-oxo-dG and cleaved caspase-3 than conplastic (BL/6^NZB) mice. This study demonstrates that mtDNA genetic manipulation ameliorates joint aging damage in a conplastic mouse model, suggesting that mtDNA variability is a prognostic factor for aging-related osteoarthritis (OA) and that modulation of mitochondrial oxidative phosphorylation (OXPHOS) could be a novel therapeutic target for treating OA associated with aging.

mtDNA haplogroup A enhances the effect of obesity on the risk of knee OA in a Mexican population

To evaluate the influence of mitochondrial DNA haplogroups on the risk of knee OA in terms of their interaction with obesity, in a population from Mexico. Samples were obtained from (n = 353) knee OA patients (KL grade ≥ I) and (n = 364) healthy controls (KL grade = 0) from Mexico city and Torreon (Mexico). Both Caucasian and Amerindian mtDNA haplogroups were assigned by single base extension assay. A set of clinical and demographic variables, including obesity status, were considered to perform appropriate statistical approaches, including chi-square contingency tables, regression models and interaction analyses. To ensure the robustness of the predictive model, a statistical cross-validation strategy of B = 1000 iterations was used. All the analyses were performed using boot, GmAMisc and epiR package from R software v4.0.2 and SPSS software v24. The frequency distribution of the mtDNA haplogroups between OA patients and healthy controls for obese and non-obese groups showed the haplogroup A as significantly over-represented in knee OA patients within the obese group (OR 2.23; 95% CI 1.22–4.05; p-value = 0.008). The subsequent logistic regression analysis, including as covariate the interaction between obesity and mtDNA haplogroup A, supported the significant association of this interaction (OR 2.57; 95% CI 1.24–5.32; p-value = 0.011). The statistical cross-validation strategy confirmed the robustness of the regression model. The data presented here indicate a link between obesity in knee OA patients and mtDNA haplogroup A.

PROCOAC (PROspective COhort of A Coruña) description: Spanish prospective cohort to study osteoarthritis

INTRODUCTION AND OBJECTIVE

The use of well characterized osteoarthritis (OA) cohorts is mandatory for the study and knowledge of this disease. Currently, there is no prospective cohort in this pathology in Spain. The objective of this work is to describe the first osteoarthritis cohort in Spain, PROCOAC (Cohort PROspectiva de A Coruña).

METHODS

The Unit of Rheumatology of the University Hospital of A Coruña started a prospective follow-up study in 2006. The patient inclusion criteria were: I) Patients older than 55 years who underwent an abdominal x-ray to study both hips II) Patients diagnosed with radiographic hand OA according to ACR criteria III) Patients diagnosed with radiographic knee or hip OA according to ACR criteria. Follow-up was performed every two years collecting clinical, analytical, genetic and radiographic information.

RESULTS

The cohort consists of 937 patients, 873 have radiographic knee OA, 783 hip OA and 679 hand OA. The mean age of the population is 63.9±8.9 years and the average BMI is 29.6±5.1. More than half of the population has high blood pressure and 17% diabetes. The predominant osteoarthritis in the hand is nodular (78.1%), followed by trapeziometacarpal (55.3%) and erosive (18.4%). Twenty-one point four percent and 43.1% are healthy at knee and hip level respectively; observing a grade 1 in 26% and 37%; a grade 2 in 26.7% and 11.5%; a grade 3 in 14.9% and 4%; and a grade 4 in 9.4% and 3.7% respectively. Of the population, 44.1% has only 1 joint affected, 39.9% has 2 and 13.4% has 3 joints affected. Age (OR=1.11; p<.001), BMI (OR=1.11; p=.002) and total WOMAC (OR=1.03; p=.005) are the only risk factors if we compare the involvement of a single location versus three. A discrepancy between pain and radiographic damage at the joint level was also detected in patients with KL≤2 grade, and therefore a significantly higher percentage of patients with knee OA experienced pain (66.1%) compared to patients with OA hip (21.1%) (p<.001).

CONCLUSIONS

The PROCOAC cohort is an instrument that allows studies of incidence and progression in hand, knee and hip OA; as well as determining factors that are associated with the different OA phenotypes.

Genetic biomarkers in osteoarthritis: a quick overview

Osteoarthritis (OA) is a chronic musculoskeletal disease with a polygenic and heterogeneous nature. In addition, when clinical manifestations appear, the evolution of the disease is usually already irreversible. Therefore, the efforts on OA research are focused mainly on the discovery of therapeutic targets and reliable biomarkers that permit the early identification of different OA-related parameters such as diagnosis, prognosis, or phenotype identification. To date, potential candidate protein biomarkers have been associated with different aspects of the disease; however, there is currently no gold standard. In this sense, genomic data could act as complementary biomarkers of diagnosis and prognosis or even help to identify therapeutic targets of the disease. In this review, we will describe the most recent advances in genetic biomarkers in OA over the past three years.

Association of accelerated dynamics of telomere sequence loss in peripheral blood leukocytes with incident knee osteoarthritis in Osteoarthritis Initiative cohort

Osteoarthritis (OA) is a chronic degenerative joint disease, being the main cause of laboral inability. Decreased telomere size in peripheral blood leukocytes (PBL) has been correlated with age-related pathologies, like knee OA. In a dynamic approach, telomere-qPCR was performed to evaluate the relative percentage of PBL telomere loss after a 6-year follow-up, in 281 subjects from the prospective osteoarthritis initiative (OAI) cohort. A radiological Kellgren-Lawrence (KL) grade ≥ 2 was indicative of knee OA. Individuals with knee OA at recruitment (n = 144) showed a higher PBL telomere loss after 6 years than those without knee OA at baseline (n = 137; p = 0.018). Moreover, individuals that developed knee OA during the follow-up (n = 39) exhibited a higher telomere loss compared to those that remained without OA (n = 98; p < 0.001). Logistic regression analysis showed that PBLs telomere loss was not significantly associated with knee OA at recruitment, but behaves as an independent risk factor associated with incidence after follow-up (OR: 1.043; p = 0.041), together with maximum KL grade (OR: 3.627; p = 0.011), body mass index-BMI (OR: 1.252; p < 0.001) and WOMAC-index (OR: 1.247; p = 0.021), at recruitment. The telomere decay in PBLs is faster in individuals with incident knee OA, possibly reflecting a systemic-global accelerated aging that enhances the cartilage degeneration.

A clinical model including protein biomarkers predicts radiographic knee osteoarthritis: a prospective study using data from the Osteoarthritis Initiative

OBJECTIVE

We aimed to provide a model to predict the prospective development of radiographic KOA (rKOA).

METHOD

Baseline sera from 333 non-radiographic KOA subjects belonging to OA Initiative (OAI) who developed or not, rKOA during a follow-up period of 96 months were used in this study. The exploratory cohort included 200 subjects, whereas the replication cohort included 133. The levels of inter-alpha trypsin inhibitor heavy chain 1 (ITIH1), complement C3 (C3) and calcyclin (S100A6), identified in previous large proteomic analysis, were analyzed by using sandwich immunoassays on suspension bead arrays. The association of protein levels and clinical covariates with rKOA incidence was assessed by combining logistic regression analysis, Receiver Operating Characteristic (ROC) analysis, Integrated Discrimination Improvement (IDI) analysis and Kaplan-Meier curves.

RESULTS

Levels of ITIH1, C3 and S100A6 were significantly associated with the prospective development of rKOA, showing an area under the curve (AUC) of 0.713 (0.624-0.802), 0.708 (0.618-0.799) and 0.654 (0.559-0.749), respectively to predict rKOA in the replication cohort. The inclusion of ITIH1 in the clinical model (age, gender, BMI, previous knee injury and WOMAC pain) improved the predictive capacity of the clinical covariates (AUC = 0.754 [0.670-0.838]) producing the model with the highest AUC (0.786 [0.705-0.867]) and the highest IDI index (9%). High levels of ITIH1 were also associated with an earlier onset of the disease.

CONCLUSION

A clinical model including protein biomarkers that predicts incident rKOA has been developed. Among the tested biomarkers, ITIH1 showed potential to improve the capacity to predict rKOA incidence in clinical practice.

Design of a digital-PCR assay to quantify fragmented human mitochondrial DNA

Digital PCR (dPCR) has been adapted to quantify the proportion of mitochondrial DNA (mtDNA) molecules without and with double-strand DNA breaks (DSBs). This is based on a break-apart approach of two differentially labeled target sequences distantly located in the circular DNA molecule. When the two targets amplify in separated reaction partitions, the original mtDNA molecule should be fragmented by two DSBs at least, each in a different segment between targets. When both targets amplify in the same partition, it must correspond to a circular or linear mtDNA molecule. These two possibilities may be distinguished through a restriction endonuclease (RE) induced unique DSB within a DNA segment between the targets. After RE-digestion, separation of both target signals in different partitions must indicate the presence of a previous linear mtDNA molecule. Otherwise, joint amplification in the same partition would correspond to an initial circular mtDNA that has been linearized by the endonuclease. The procedure was validated by assaying different proportions of mtDNA fragmented by in vitro digestion with REs, evidencing a perfect accordance between the expected theoretical values and dPCR quantification. Samples from peripheral blood cells, cellular and extracellular DNA from the U2OS cell line, as well as cells incubated with ethidium bromide to induce mtDNA depletion, were evaluated. The technique may be of interest to complement the studies of mtDNA in relation to aging and human disease, as well as to assess possible adverse effects of certain drugs that could be related to affectation of mtDNA.

Oleate Prevents Palmitate-Induced Mitochondrial Dysfunction in Chondrocytes

The association between obesity and osteoarthritis (OA) in joints not subjected to mechanical overload, together with the relationship between OA and metabolic syndrome, suggests that there are systemic factors related to metabolic disorders that are involved in the metabolic phenotype of OA. The aim of this work is study the effects of palmitate and oleate on cellular metabolism in an "in vitro" model of human chondrocytes. The TC28a2 chondrocyte cell line was used to analyze the effect of palmitate and oleate on mitochondrial and glycolytic function, Adenosine triphosphate (ATP) production and lipid droplets accumulation. Palmitate, but not oleate, produces mitochondrial dysfunction observed with a lower coupling efficiency, maximal respiration and spare respiratory capacity. Glycolytic function showed lower rates both glycolytic capacity and glycolytic reserve when cells were incubated with fatty acids (FAs). The production rate of total and mitochondrial ATP showed lower values in chondrocytes incubated with palmitic acid (PA). The formation of lipid droplets increased in FA conditions, being significantly higher when the cells were incubated with oleic acid (OL). These results may help explain, at least in part, the close relationship of metabolic pathologies with OA, as well as help to elucidate some of the factors that can define a metabolic phenotype in OA.

Mitochondrial DNA impact on joint damaged process in a conplastic mouse model after being surgically induced with osteoarthritis

It has been suggested that mitochondrial dysfunction and mtDNA variations may contribute to osteoarthritis (OA) pathogenesis. However, the causative link to support this claim is lacking. Here, we surgically-induced OA in conplastic mice in order to evaluate the functional consequences of mtDNA haplotypes in their joint degeneration. BL/6NZB strain was developed with C57BL/6JOlaHsd nuclear genome and NZB/OlaHsdmtDNA while BL/6C57, which is the original, was developed with C57BL/6JOlaHsd nuclear genome and C57/OlaHsdmtDNA for comparison. The surgical DMM OA model was induced in both strains. Their knees were processed and examined for histopathological changes. Cartilage expression of markers of autophagy, apoptosis, oxidative stress and senescence were also analyzed by immunohistochemistry. The joints of BL/6NZB mice that were operated presented more cellularity together with a reduced OARSI histopathology score, subchondral bone, menisci score and synovitis compared to those of BL/6C57 mice. This was accompanied with higher autophagy and a lower apoptosis in the cartilage of BL/6NZB mice that were operated. Therefore, the study demonstrates the functional impact of non-pathological variants of mtDNA on OA process using a surgically-induced OA model. Conplastic (BL/6NZB ) mice develop less severe OA compared to the BL/6C57original strain. These findings demonstrate that mitochondria and mtDNA are critical targets for potential novel therapeutic approaches to treat osteoarthritis.

Relationship Between the Dynamics of Telomere Loss in Peripheral Blood Leukocytes From Knee Osteoarthritis Patients and Mitochondrial DNA Haplogroups

OBJECTIVE

To evaluate the evolution of telomere length from peripheral blood leukocytes (PBLs) in subjects from the Osteoarthritis Initiative (OAI) cohort in relation to the incidence of osteoarthritis (OA), and to explore its possible interactive influence with the mitochondrial DNA (mtDNA) haplogroup.

METHODS

Dynamics of telomere sequence loss were quantified in PBLs from initially healthy individuals (without symptoms or radiological signs), 78 carrying the mtDNA cluster HV, and 47 with cluster JT, from the OAI, during a 72-month follow-up period. The incidence of knee OA during this period (n = 39) was radiographically established when Kellgren-Lawrence (KL) score increased from < 2 at recruitment, to ≥ 2 at the end of 72 months of follow-up. Multivariate analysis using binary logistic regression was performed to assess PBL telomere loss and mtDNA haplogroups as associated risk factors of incidence of knee OA.

RESULTS

Carriers of cluster HV showed knee OA incidence twice that of the JT carriers (n = 30 vs 9). The rate of PBL telomere loss was higher in cluster HV carriers and in individuals with incident knee OA. Multivariate analysis showed that the dynamics of PBL telomere shortening can be a consistent risk marker of knee OA incidence. Subjects with nonincident knee OA showed a slower telomere loss than those with incident knee OA; the difference was more significant in carriers of cluster JT than in HV.

CONCLUSION

An increased rate of telomere loss in PBLs may reflect a systemic accelerated senescence phenotype that could be potentiated by the mitochondrial function, increasing the susceptibility of developing knee OA.

PROCOAC (PROspective COhort of A Coruña) description: Spanish prospective cohort to study osteoarthritis

INTRODUCTION AND OBJECTIVE

The use of well characterized osteoarthritis cohorts is mandatory for the study and knowledge of this disease. Currently, there is no prospective cohort in this pathology in Spain. The objective of this work is to describe the first osteoarthritis cohort in Spain, PROCOAC (Cohort PROspectiva de A Coruña).

METHODS

The Unit of Rheumatology of the University Hospital of A Coruña started a prospective follow-up study in 2006. The patient inclusion criteria were: a) patients older than 55 years who underwent an abdominal x-ray to study both hips; b) patients diagnosed with radiographic hand osteoarthritis according to ACR criteria; c) patients diagnosed with radiographic knee or hip osteoarthritis according to ACR criteria. Follow-up was performed every 2years collecting clinical, analytical, genetic and radiographic information.

RESULTS

The cohort consists of 937 patients, 873 have radiographic knee osteoarthritis, 783 hip osteoarthritis and 679 hand osteoarthritis. The mean age of the population is 63.9±8.9 years and the average BMI is 29.6±5.1. More than half of the population has high blood pressure and 17% diabetes. The predominant osteoarthritis in the hand is nodular (78.1%), followed by trapeziometacarpal (55.3%) and erosive (18.4%). Of them, 21.4% and 43.1% are healthy at knee and hip level respectively; observing a grade 1 in 26% and 37%; a grade 2 in 26.7% and 11.5%; a grade 3 in 14.9% and 4%; and a grade 4 in 9.4% and 3.7%, respectively. Of the population, 44.1% has only one joint affected, 39.9% has 2 and 13.4% has 3 joints affected. Age (OR=1.11; P <.001), BMI (OR=1.11; P=.002) and total WOMAC (OR=1.03; P=.005) are the only risk factors if we compare the involvement of a single location versus 3. A discrepancy between pain and radiographic damage at the joint level was also detected in patients with KL ≤ 2 grade, and therefore a significantly higher percentage of patients with knee osteoarthritis experienced pain (66.1%) compared to patients with osteoarthritis hip (21.1%) (P<.001).

CONCLUSIONS

The PROCOAC cohort is an instrument that allows studies of incidence and progression in hand, knee and hip osteoarthritis; as well as determining factors that are associated with the different osteoarthritis phenotypes.

Impaired Metabolic Flexibility in the Osteoarthritis Process: A Study on Transmitochondrial Cybrids

Osteoarthritis (OA) is the most frequent joint disease; however, the etiopathogenesis is still unclear. Chondrocytes rely primarily on glycolysis to meet cellular energy demand, but studies implicate impaired mitochondrial function in OA pathogenesis. The relationship between mitochondrial dysfunction and OA has been established. The aim of the study was to examine the differences in glucose and Fatty Acids (FA) metabolism, especially with regards to metabolic flexibility, in cybrids from healthy (N) or OA donors. Glucose and FA metabolism were studied using D-[¹⁴C(U)]glucose and [1-¹⁴C]oleic acid, respectively. There were no differences in glucose metabolism among the cybrids. Osteoarthritis cybrids had lower acid-soluble metabolites, reflecting incomplete FA β-oxidation but higher incorporation of oleic acid into triacylglycerol. Co-incubation with glucose and oleic acid showed that N but not OA cybrids increased their glucose metabolism. When treating with the mitochondrial inhibitor etomoxir, N cybrids still maintained higher glucose oxidation. Furthermore, OA cybrids had higher oxidative stress response. Combined, this indicated that N cybrids had higher metabolic flexibility than OA cybrids. Healthy donors maintained the glycolytic phenotype, whereas OA donors showed a preference towards oleic acid metabolism. Interestingly, the results indicated that cybrids from OA patients had mitochondrial impairments and reduced metabolic flexibility compared to N cybrids.

Mitochondrial Genetics and Epigenetics in Osteoarthritis

During recent years, the significant influence of mitochondria on osteoarthritis (OA), the most common joint disease, has been consistently demonstrated. Not only mitochondrial dysfunction but also mitochondrial genetic polymorphisms, specifically the mitochondrial DNA haplogroups, have been shown to have an important influence on different OA-related features, including the prevalence, severity, incidence, and progression of the disease. This influence could probably be mediated by the role of mitochondria in the regulation of different processes involved in the pathogenesis of OA, such as energy production, the generation of reactive oxygen and nitrogen species, apoptosis, and inflammation. The regulation of these processes is at least partially controlled by the bi-directional communication between the nucleus and mitochondria, which permits the regulation of adaptation to a wide range of stressors and the maintenance of cellular homeostasis. This bi-directional communication consists of an “anterograde regulation” by which the nucleus regulates mitochondrial biogenesis and activity and a “retrograde regulation” by which both mitochondria and mitochondrial genetic variation exert a regulatory signaling control over the nuclear epigenome, which leads to the modulation of nuclear genes. Throughout this mini review, we will describe the evidence that demonstrates the profound influence of the mitochondrial genetic background in the pathogenesis of OA, as well as its influence on the nuclear DNA methylome of the only cell type present in the articular cartilage, the chondrocyte. This evidence leads to serious consideration of the mitochondrion as an important therapeutic target in OA.

Predictive modeling of therapeutic response to chondroitin sulfate/glucosamine hydrochloride in knee osteoarthritis

Background

In the present study, we explored potential protein biomarkers useful to predict the therapeutic response of knee osteoarthritis (KOA) patients treated with pharmaceutical grade Chondroitin sulfate/Glucosamine hydrochloride (CS+GH; Droglican, Bioiberica), in order to optimize therapeutic outcomes.

Methods

A shotgun proteomic analysis by iTRAQ labelling and liquid chromatography-mass spectrometry (LC-MS/MS) was performed using sera from 40 patients enrolled in the Multicentre Osteoarthritis interVEntion trial with Sysadoa (MOVES). The panel of proteins potentially useful to predict KOA patient's response was clinically validated in the whole MOVES cohort at baseline (n = 506) using commercially available enzyme-linked immunosorbent assays kits. Logistic regression models and receiver-operating-characteristics (ROC) curves were used to analyze the contribution of these proteins to our prediction models of symptomatic drug response in KOA.

Results

In the discovery phase of the study, a panel of six putative predictive biomarkers of response to CS+GH (APOA2, APOA4, APOH, ITIH1, C4BPa and ORM2) were identified by shotgun proteomics. Data are available via ProteomeXchange with identifier PXD012444. In the verification phase, the panel was verified in a larger set of KOA patients (n = 262). Finally, ITIH1 and ORM2 were qualified by a blind test in the whole MOVES cohort at baseline. The combination of these biomarkers with clinical variables predict the patients' response to CS+GH with a specificity of 79.5% and a sensitivity of 77.1%.

Conclusions

Combining clinical and analytical parameters, we identified one biomarker that could accurately predict KOA patients' response to CS+GH treatment. Its use would allow an increase in response rates and safety for the patients suffering KOA.

Differential Association of Mitochondrial DNA Haplogroups J and H With the Methylation Status of Articular Cartilage: Potential Role in Apoptosis and Metabolic and Developmental Processes

OBJECTIVE

To analyze the influence of mitochondrial genome variation on the DNA methylome of articular cartilage.

METHODS

DNA methylation profiling was performed using data deposited in the NCBI Gene Expression Omnibus database (accession no. GSE43269). Data were obtained for 14 cartilage samples from subjects with haplogroup J and 20 cartilage samples from subjects with haplogroup H. Subsequent validation was performed in an independent subset of 7 subjects with haplogroup J and 9 with haplogroup H by RNA-seq. Correlated genes were validated by real-time polymerase chain reaction in an independent cohort of 12 subjects with haplogroup J and 12 with haplogroup H. Appropriate analyses were performed using R Bioconductor and qBasePlus software, and gene ontology analysis was conducted using DAVID version 6.8.

RESULTS

DNA methylation profiling revealed 538 differentially methylated loci, while whole-transcriptome profiling identified 2,384 differentially expressed genes, between cartilage samples from subjects with haplogroup H and those with haplogroup J. Seventeen genes showed an inverse correlation between methylation and expression. In terms of gene ontology, differences in correlations between methylation and expression were also detected between cartilage from subjects with haplogroup H and those with haplogroup J, highlighting a significantly enhanced apoptotic process in cartilage from subjects with haplogroup H (P = 0.007 for methylation and P = 0.019 for expression) and repressed apoptotic process in cartilage from subjects with haplogroup J (P = 0.021 for methylation), as well as a significant enrichment of genes related to metabolic processes (P = 1.93 × 10^-4 for methylation and P = 6.79 x 10^-4 for expression) and regulation of gene expression (P = 0.012 for methylation) in cartilage from subjects with haplogroup H, and to developmental processes (P = 0.015 for methylation and P = 8.25 x 10^-12 for expression) in cartilage from subjects with haplogroup J.

CONCLUSION

Mitochondrial DNA variation differentially associates with the methylation status of articular cartilage by acting on key mechanisms involved in osteoarthritis, such as apoptosis and metabolic and developmental processes.

Leukocyte Telomere Length in Patients with Radiographic Knee Osteoarthritis

Relative mean telomere sequence amount was determined by quantitative PCR (qPCR) of peripheral blood leukocyte (PBL) samples obtained at recruitment (n = 310) from individuals from the Osteoarthritis (OA) Initiative consortium. Knees were radiologically evaluated according to the Kellgren-Lawrence (KL) score, ranging from 0 to 4, considering a KL grade ≥ 2 as radiographic evidence of OA (n = 124). Telomere size decreased as baseline KL score increased, being significantly shorter in subjects with KL ≥2 (Mann-Whitney U-test, P < 0.0001). PBL telomere size was also associated with age, hypertension, body mass index (BMI) and waist circumference. Nevertheless, logistic regression analysis showed that PBL telomere size was a consistent risk factor for concurrent knee OA, independent of these health parameters. Shorter PBL telomeres may indicate a premature aging status which enhances chondrocyte senescence and degenerative joint disease. Environ. Mol. Mutagen. 60:298-301, 2019. © 2018 Wiley Periodicals, Inc.

Mitochondrial DNA haplogroups associated with MRI-detected structural damage in early knee osteoarthritis

OBJECTIVE

Magnetic resonance imaging (MRI)-detected structural features are associated with increased risk of radiographic osteoarthritis (ROA). Specific mitochondrial DNA (mtDNA) haplogroups have been associated with incident ROA. Our objective was to compare the presence of MRI-detected structural features across mtDNA haplogroups among knees that developed incident ROA.

DESIGN

Knees from the Osteoarthritis Initiative (OAI) that developed incident ROA during 48 months follow-up were identified from Caucasian participants. mtDNA haplogroups were assigned based on a single base extension assay. MRIs were obtained annually between baseline and 4-year follow-up and scored using the MRI Osteoarthritis Knee Score (MOAKS). The association between mtDNA haplogroups and MRI-detected structural features was estimated using log-binomial regression. Participants who carried haplogroup H served as the reference group.

RESULTS

The sample included 255 participants contributing 277 knees that developed ROA. Haplogroups included H (116, 45%), J (17, 7%), T (26, 10%), Uk (61, 24%), and the remaining less common haplogroups ("others") (35, 14%). Knees of participants with haplogroup J had significantly lower risk of medium/large bone marrow lesions (BMLs) in the medial compartment [3.2%, relative risks (RR) = 0.17; 95%CI: 0.05, 0.64; P = 0.009] compared to knees of participants who carried haplogroup H [16.3%], as did knees from participants within the "others" group [2.8%, RR = 0.20; 95%CI: 0.08, 0.55; P = 0.002], over the 4 year follow-up period.

CONCLUSIONS

mtDNA haplogroup J was associated with lower risk of BMLs in the medial compartment among knees that developed ROA. Our results offer a potential hypothesis to explain the mechanism underlying the previously reported protective association between haplogroup J and ROA.

Plasma mitochondrial DNA levels are inversely associated with HIV-RNA levels and directly with CD4 counts: potential role as a biomarker of HIV replication

Objectives

To evaluate plasma mitochondrial DNA (mtDNA) levels among HIV-infected patients and its potential role as a biomarker of residual viral replication.

Methods

HIV-infected patients on follow-up at a reference hospital in north-west Spain were selected. DNA was isolated from plasma samples and mtDNA levels were assessed using a quantitative real-time PCR assay. HIV-RNA levels and CD4+ cell counts were evaluated in the same blood samples used for plasma mtDNA quantification. Epidemiological and clinical variables were included for the analysis.

Results

A total of 235 HIV-infected patients were included. Mean plasma mtDNA levels were 217 ± 656 copies/μL for naive (31.9%) and 364 ± 939 copies/μL for HIV-infected patients receiving ART and with suppressed viraemia (P = 0.043). Among the latter, mean plasma mtDNA levels were 149 ± 440 copies/μL for those with low-level viraemia (LLV; HIV-RNA 20-200 copies/mL), 265 ± 723 copies/μL for those with detected-not-quantified (DNQ) viraemia (HIV-RNA <20 copies/mL) and 644 ± 1310 copies/μL for those with not-detected (ND) viraemia. Of note, a linear trend (P = 0.006) was observed among virologically suppressed (LLV, DNQ and ND) patients. ND patients had higher mtDNA levels compared with LLV patients (P = 0.057). Moreover, mtDNA levels were inversely associated with HIV-RNA levels (Spearman's rho -0.191, P = 0.003) and directly associated with CD4+ counts (Spearman's rho 0.131, P = 0.046).

Conclusions

Increased plasma mtDNA levels are associated with lower HIV-RNA levels and higher CD4+ cell counts. Among ART-suppressed patients, mtDNA levels were significantly higher in those with complete virological suppression (ND) than in those with LLV. These data suggest that plasma mtDNA levels might serve as a biomarker of residual HIV replication.

Mitochondrial DNA haplogroups influence the risk of incident knee osteoarthritis in OAI and CHECK cohorts. A meta-analysis and functional study

Objective

To evaluate the influence of the mitochondrial DNA (mtDNA) haplogroups in the risk of incident knee osteoarthritis (OA) and to explain the functional consequences of this association to identify potential diagnostic biomarkers and therapeutic targets.

Methods

Two prospective cohorts contributed participants. The osteoarthritis initiative (OAI) included 2579 subjects of the incidence subcohort, and the cohort hip and cohort knee (CHECK) included 635, both with 8-year follow-up. The analysis included the association of mtDNA haplogroups with the rate of incident knee OA in subjects from both cohorts followed by a subsequent meta-analysis. Transmitochondrial cybrids harbouring haplogroup J or H were constructed to detect differences between them in relation to physiological features including specific mitochondrial metabolic parameters, reactive oxygen species production, oxidative stress and apoptosis.

Results

Compared with H, the haplogroup J associates with decreased risk of incident knee OA in subjects from OAI (HR=0.680; 95% CI 0.470 to 0.968; p<0.05) and CHECK (HR=0.728; 95% CI 0.469 to 0.998; p<0.05). The subsequent meta-analysis including 3214 cases showed that the haplogroup J associates with a lower risk of incident knee OA (HR=0.702; 95% CI 0.541 to 0.912; p=0.008). J cybrids show a lower free radical production, higher cell survival under oxidative stress conditions, lower grade of apoptosis as well as lower expression of the mitochondrially related pro-apoptotic gene BCL2 binding component 3 (BBC3). In addition, J cybrids also show a lower mitochondrial respiration and glycolysis leading to decreased ATP production.

Conclusions

The physiological effects of the haplogroup J are beneficial to have a lower rate of incident knee OA over time. Potential drugs to treat OA could focus on emulating the mitochondrial behaviour of this haplogroup.

A replication study and meta-analysis of mitochondrial DNA variants in the radiographic progression of knee osteoarthritis

OBJECTIVE

To conduct a replication study and meta-analysis involving the study of mtDNA variants in the radiographic progression of OA in different cohorts worldwide, including Cohort Hip and Cohort Knee (CHECK), the OA Initiative and a cohort from Spain.

METHODS

The influence of the haplogroups in the rate of radiographic progression at 96 months in 431 subjects from CHECK was assessed in terms of Kellgren and Lawrence (KL) grade. Progression was defined as a change from KL ⩾ 1 at baseline to any higher grade during the follow-up. Extended Cox proportional hazard models were used to analyse the influence of mtDNA variants in the rate of radiographic knee OA progression. A subsequent meta-analysis of 1603 subjects following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was conducted to combine the data of individual studies. A sensitivity analysis was performed to validate the stability of the results.

RESULTS

CHECK subjects carrying the haplogroup T showed the lowest rate of radiographic knee OA progression [hazard ratio (HR) 0.645 (95% CI 0.419, 0.978); P < 0.05]. When pooled, subjects within the superhaplogroup JT showed the same trend [HR 0.707 (95% CI 0.501, 0.965); P < 0.05]. BMI [HR 1.046 (95% CI 1.018, 1.073); P < 0.05] and bilateral OA [HR 2.266 (95% CI 1.733, 2.954); P < 0.05] at baseline are risk factors for radiographic knee OA progression as well. In the meta-analysis there was a reduced rate of radiographic progression in subjects with haplogroup T [HR 0.612 (95% CI 0.454, 0.824); P = 0.001] or in the superhaplogroup JT [HR 0.765 (95% CI 0.624, 0.938); P = 0.009]. Sensitivity analysis revealed that the results were robust.

CONCLUSION

The mtDNA variants in the superhaplogroup JT associate with a reduced rate of radiographic OA progression. The mtDNA polymorphisms in the superhaplogroup JT emerge as potential complementary genetic biomarkers for disease progression.

Mitochondrial DNA (mtDNA) haplogroups influence the progression of knee osteoarthritis. Data from the Osteoarthritis Initiative (OAI)

OBJECTIVE

To evaluate the influence of the mtDNA haplogroups on knee osteoarthritis progression in Osteoarthritis Initiative (OAI) participants through longitudinal data from radiographs and magnetic resonance imaging (MRI).

METHODS

Four-year knee osteoarthritis progression was analyzed as increase in Kellgren and Lawrence (KL) grade, in addition to increase in OARSI atlas grade for joint space narrowing (JSN), osteophytes and subchondral sclerosis in the tibia medial compartment of 891 Caucasian individuals from the progression subcohort. The influence of the haplogroups on the rate of structural progression was also assessed as the four-year change in minimum joint space width (mJSW in millimetres) in both knees of (n = 216) patients with baseline unilateral medial-tibiofemoral JSN. Quantitative cartilage measures from longitudinal MRI data were those related to cartilage thickness and volume with a 24 month follow-up period (n = 381).

RESULTS

During the four-year follow-up period, knee OA patients with the haplogroup T showed the lowest increase in KL grade (Hazard Risk [HR] = 0.499; 95% Confidence Interval [CI]: 0.261-0.819; p<0.05) as well as the lowest cumulative probability of progression for JSN (HR = 0.547; 95% CI: 0.280-0.900; p<0.05), osteophytes (HR = 0.573; 95% CI: 0.304-0.893; p<0.05) and subchondral sclerosis (HR = 0.549; 95% CI: 0.295-0.884; p<0.05). They also showed the lowest decline in mJSW (standardized response means (SRM) = -0.39; p = 0.037) in those knees without baseline medial JSN (no-JSN knees). Normalized cartilage volume loss was significantly lower in patients carrying the haplogroup T at medial tibia femoral (SRM = -0.33; p = 0.023) and central medial femoral (SRM = -0.27; p = 0.031) compartments. Cartilage thickness loss was significantly lower in carriers of haplogroup T at central medial tibia-femoral (SRM = -0.42; p = 0.011), medial tibia femoral (SRM = -0.32; p = 0.018), medial tibia anterior (SRM = +0.31; p = 0.013) and central medial femoral (SRM = -0.19; p = 0.013) compartments.

CONCLUSIONS

Mitochondrial genome seems to play a role in the progression of knee osteoarthritis. mtDNA variation could improve identification of patients predisposed to faster or severe progression of the disease.

Mitochondrial respiratory chain dysfunction modulates metalloproteases -1, -3 and -13 in human normal chondrocytes in culture

BACKGROUND

Mitochondrion has an important role in the osteoarthritis (OA) pathology. We have previously demonstrated that the alteration of the mitochondrial respiratory chain (MRC) contributes to the inflammatory response of the chondrocyte. However its implication in the process of cartilage destruction is not well understood yet. In this study we have investigated the relationship between the MRC dysfunction and the regulation of metalloproteases (MMPs) in human normal chondrocytes in culture.

METHODS

Human normal chondrocytes were isolated from human knees obtained form autopsies of donors without previous history of rheumatic disease. Rotenone, 3-Nitropropionic acid (NPA), Antimycin A (AA), Sodium azide and Oligomycin were used to inhibit the activity of the mitochondrial complexes I, II, III, IV and V respectively. The mRNA expression of MMPs -1, -3 and -13 was studied by real time PCR. The intracellular presence of MMP proteins was evaluated by western blot. The liberation of these proteins to the extracellular media was evaluated by ELISA. The presence of proteoglycans in tissue was performed with tolouidin blue and safranin/fast green. Immunohistochemistry was used for evaluating MMPs on tissue.

RESULTS

Firstly, cells were treated with the inhibitors of the MRC for 24 hours and mRNA expression was evaluated. An up regulation of MMP-1 and -3 mRNA levels was observed after the treatment with Oligomycin 5 and 100 μg/ml (inhibitor of the complex V) for 24 hours. MMP-13 mRNA expression was reduced after the incubation with AA 20 and 60 μg/ml (inhibitor of complex III) and Oligomycin. Results were validated at protein level observing an increase in the intracellular levels of MMP-1 and -3 after Oligomycin 25 μg/ml stimulation [(15.20±8.46 and 4.59±1.83 vs. basal=1, respectively (n=4; *P<0.05)]. However, AA and Oligomycin reduced the intracellular levels of the MMP-13 protein (0.70±0.16 and 0.3±0.24, respectively vs. basal=1). In order to know whether the MRC dysfunction had an effect on the liberation of MMPs, their levels were evaluated in the supernatants. After 36 hours of stimulation, values were: MMP-1=18.06±10.35 with Oligomycin 25 μg/ml vs. basal=1, and MMP-3=8.49±4.32 with Oligomycin 5 μg/ml vs. basal=1 (n=5; *P<0.05). MMP-13 levels in the supernatants were reduced after AA 60 μg/ml treatment (0.50±0.13 vs. basal=1) and Oligomycin 25 μg/ml (0.41±0.14 vs. basal=1); (n=5; *P<0.05). The treatment of explants with Oligomycin, showed an increase in the positivity of MMP-1 and -3. Explants stimulated with AA or Oligomycin revealed a decrease in MMP-13 expression. Proteoglycan staining demonstrated a reduction of proteoglycan levels in the tissues treated with Oligomycin.

CONCLUSIONS

These results reveal that MRC dysfunction modulates the MMPs expression in human normal chondrocytes demonstrating its role in the regulation of the cartilage destruction.

Genome-wide DNA methylation analysis of articular chondrocytes reveals a cluster of osteoarthritic patients

OBJECTIVE

Alterations in DNA methylation patterns have been found to correlate with several diseases including osteoarthritis (OA). The aim of this study was to identify, for the first time, the genome-wide DNA methylation profiles of human articular chondrocytes from OA cartilage and healthy control cartilage samples.

METHODS

DNA methylation profiling was performed using Illumina Infinium HumanMethylation27 in 25 patients with OA and 20 healthy controls. Subsequent validation was performed by genome-wide expression analysis using the Affymetrix Human Gene 1.1 ST array in an independent cohort of 24 patients with OA. Finally, the most consistent genes in both assays were amplified by quantitative reverse transcriptase PCR in a validation cohort of 48 patients using microfluidic real-time quantitative PCR. Appropriate bioinformatics analyses were carried out using R bioconductor software packages and qBase plus software from Biogazelle.

RESULTS

We found 91 differentially methylated (DM) probes, which permitted us to separate patients with OA from healthy controls. Among the patients with OA, we detected 1357 DM probes that identified a tight cluster of seven patients who were different from the rest. This cluster was also identified by genome-wide expression in which 450 genes were differentially expressed. Further validation of the most consistent genes in an independent cohort of patients with OA permitted us to identify this cluster, which was characterised by increased inflammatory processes.

CONCLUSIONS

We were able to identify a tight subgroup of patients with OA, characterised by an increased inflammatory response that could be regulated by epigenetics. The identification and isolation of this subgroup may be critical for the development of effective treatment and disease prevention.

Mitochondrial haplogroups H and J: risk and protective factors for ischemic cardiomyopathy

Background

Since mitochondria are the principal source of reactive oxygen species (ROS), these organelles may play an important role in ischemic cardiomyopathy (IC) development. The mitochondrial genome may influence this disease. The aim of the present study was to test the relationship between IC development and the impact of single nucleotide polymorphisms (SNPs) in mitochondrial DNA (mtDNA) defining the mitochondrial haplogroups in a population study.

Methodology and principal findings

Ten major European haplogroups were identified by using the single base extension technique and by polymerase chain reaction-restriction fragment length polymorphism. Frequencies and Odds Ratios for the association between IC patients (n = 358) and healthy controls (n = 423) were calculated. No convincing associations between classical risk factors for ischemic cardiomyopathy development and haplogroups were found. However, compared to healthy controls, the prevalence of haplogroup H was significantly higher in IC patients (40.0% vs 50.0%, p-value  = 0.039) while the frequency of haplogroup J was significantly lower (11.1% vs 5.6%, p-value  = 0.048). The analysis of the SNPs characterizing the European mtDNA haplogroups showed that the m.7028C allele (40.0% vs 50.0%, p-value  = 0.005) and m.14766C allele (43.0% vs 54.2%, p-value  = 0.002) were overrepresented in IC patients, meanwhile the m.10398G allele (19.8% vs 13.1%, p-value  = 0.015) and m.4216C allele (22.2% vs 16.5%, p-value  = 0.044) were found as protective factors against IC.

Conclusions and significance

Our results showed that the haplogroups H and J were found as a risk and protective factors for ischemic cardiomyopathy development, respectively.

Mitochondrial haplogroups define two phenotypes of osteoarthritis

Objective: To assess a mitochondrion-related phenotype in patients with osteoarthritis (OA). Methods: Serum levels of the following OA-related biomarkers: matrix metalloproteinase-1 (MMP-1); MMP-3; MMP-13; myeloperoxidase (MPO); a peptide of the alpha-helical region of type II collagen, Coll2-1, and its nitrated form Coll2-1NO₂; a C-terminal neoepitope generated by the collagenase-mediated cleavage of collagen type II triple helix, C2C; the C-propeptide of collagen type II, CPII; hyaluronic acid (HA); human cartilage glycoprotein 39, YKL-40; cartilage oligomeric matrix protein; and cathepsin K were analyzed in 48 OA patients and 52 healthy controls carrying the haplogroups H and J. Logistic regression models and receiver operating characteristic (ROC) curves were performed to predict the onset of OA. Results: MMP-13 was the only biomarker significantly increased in OA patients compared to healthy controls in both haplogroups H and J. The collagen type II biomarkers, Coll2-1, Coll2-1NO₂, the Coll2-1NO₂/Coll2-1 ratio, C2C, CPII, and the C2C:CPII ratio were significantly increased in OA patients carrying haplogroup H compared to OA carriers of the haplogroup J. Two logistic regression models for diagnosis were constructed and adjusted for age, gender, and body mass index. For haplogroup H, the biomarkers significantly associated with OA were MMP-13 and Coll2-1; the area under the curve (AUC) of the ROC curve for this model was 0.952 (95% CI = 0.892–1.012). For haplogroup J, the only biomarker significantly associated with OA was MMP-13; the AUC for this model was 0.895 (95% CI = 0.801–0.989). Conclusion: The mitochondrial DNA haplogroups are potential complementary candidates for biomarkers of OA; their genotyping in conjunction with the assessment of classical protein molecular markers is recommended.

mtDNA haplogroup J modulates telomere length and nitric oxide production

Background

Oxidative stress due to the overproduction of nitric oxide (NO) and other oxygen reactive species (ROS), play a main role in the initiation and progression of the OA disease and leads to the degeneration of mitochondria. Therefore, the goal of this work is to describe the difference in telomere length of peripheral blood leukocytes (PBLs) and Nitric Oxide (NO) production between mitochondrial DNA (mtDNA) haplogroup J and non-J carriers, as indirect approaches of oxidative stress.

Methods

The telomere length of PBL was analyzed in DNA samples from 166 healthy controls (114 J and 52 non-J) and 79 OA patients (41 J and 38 non-J) by means of a validated qPCR method. The NO production was assessed in 7 carriers of the haplogroup J and 27 non-J carriers, by means of the colorimetric reaction of the Griess reagent in supernatants of cultured chondrocytes. Inducible nitric oxide synthase (iNOS) mRNA from these samples was analyzed by qPCR. Appropiated statistical analyses were performed

Results

Carriers of the haplogroup J showed a significantly longer telomere length of PBLs than non-J carriers, regardless of age, gender and diagnosis (p = 0.025). Cultured chondrocytes carrying the mtDNA haplogroup J also showed a lower NO production than non-J carriers (p = 0.043). No significant correlations between age and telomore length of PBLs were detected neither for carriers of the haplogroup J nor for non-J carriers. A strong positive correlation between NO production and iNOS expression was also observed (correlation coefficient = 0.791, p < 0.001).

Conclusion

The protective effect of the mtDNA haplogroup J in the OA disease arise from a lower oxidative stress in carriers of this haplogroup, since this haplogroup is related to lower NO production and hence longer telomere length of PBLs too.

Gene polymorphisms and pharmacogenetics in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic, chronic and inflammatory disease of unknown etiology with genetic predisposition. The advent of new biological agents, as well as the more traditional disease-modifying antirheumatic drugs, has resulted in highly efficient therapies for reducing the symptoms and signs of RA; however, not all patients show the same level of response in disease progression to these therapies. These variations suggest that RA patients may have different genetic regulatory mechanisms. The extensive polymorphisms revealed in non-coding gene-regulatory regions in the immune system, as well as genetic variations in drug-metabolizing enzymes, suggest that this type of variation is of functional and evolutionary importance and may provide clues for developing new therapeutic strategies. Pharmacogenetics is a rapidly advancing area of research that holds the promise that therapies will soon be tailored to an individual patient’s genetic profile.

Mitochondrial DNA haplogroups and serum levels of proteolytic enzymes in patients with osteoarthritis

OBJECTIVE

To analyse the influence of mitochondrial DNA haplogroups, as well as the radiographic grade, on serum levels of proteolytic enzymes in patients with osteoarthritis (OA).

METHODS

Serum levels of metalloproteinase-1 (MMP-1), MMP-3, MMP-13, myeloperoxidase and cathepsin K were analysed in 73 patients with OA and 77 healthy controls carrying the haplogroups J, U and H, by ELISA. Knee and hip radiographs were classified according to Kellgren and Lawrence (K/L) scoring from grade 0 to grade IV. Non-parametric and multiple regression analyses were performed to test the effects of clinical variables, including gender, age, smoking status, diagnosis, haplogroups and radiological K/L grade on serum levels of these enzymes.

RESULTS

A significant influence of the haplogroups on the serum levels of MMP-3 and MMP-13 was detected (p=0.027 and p=0.035, respectively). Patients with OA with haplogroup H showed higher serum levels of MMP-3 than healthy controls. Serum levels of MMP-13 were significantly higher in patients with OA (p<0.001), and carriers of the haplogroup J showed lower levels than H carriers. Besides, levels of MMP-13 were proportionally higher in radiological groups B (K/L grade II and III) and C (K/L grade IV) than in group A (K/L grade 0 and I) (p=0.005).

CONCLUSIONS

This study shows that haplogroups have a significant influence on serum levels of MMP-3 and MMP-13. The influence of the haplogroups on serum levels of MMP-3 is clearly dependent on the diagnosis, whereas the influence of the haplogroups on serum levels of MMP-13 is independent of diagnosis.

Mitochondrial DNA haplogroups modulate the serum levels of biomarkers in patients with osteoarthritis

OBJECTIVE

To analyse the influence of mitochondrial DNA (mtDNA) haplogroups on serum levels of molecular biomarkers in patients with osteoarthritis (OA).

METHODS

Serum levels of molecular biomarkers of cartilage metabolism (collagen type II markers: C-terminal neoepitope generated by the collagenase-mediated cleavage of collagen type II triple helix (C2C), collagen type II (Coll2-1, and its nitrated form, Coll2-1NO(2)), procollagen type II (CPII)), synovial metabolism (hyaluronic acid (HA)) and cartilage and synovial turnover (cartilage glycoprotein 39 (YKL-40)) were analysed in 73 patients with OA and 77 healthy controls using ELISAs. All participants had been previously genotyped for the mtDNA haplogroups J, U and H. Non-parametric and multivariate analysis were performed to test the effects of the clinical variables, including gender, age, smoking status, diagnosis, mtDNA haplogroups and radiological Kellgren and Lawrence (K/L) grade on the serum levels of the molecular markers.

RESULTS

Non-parametric analysis found increased serum levels of HA in patients with OA, while the values for C2C and the C2C/CPII ratio were significantly higher in the healthy controls. A multiple regression analysis showed a relationship between the mtDNA haplogroups and serum levels of the typical collagen type II markers. Carriers of the mtDNA haplogroup H had higher levels while carriers of the mtDNA haplogroup J showed lower levels. Statistically significant interactions between mtDNA haplogroups and diagnosis and between mtDNA haplogroups and radiological K/L grade in the serum levels of molecular markers were also found.

CONCLUSION

A new role for mtDNA haplogroups emerges from this work. The results suggest that the mtDNA haplogroups interact significantly with the serum levels of OA-related molecular markers, suggesting the possibility of their use as a complementary assay with these molecular markers.

[Gene polymorphisms and pharmacogenetics in Rheumatoid Arthritis]

Rheumatoid arthritis (RA) is a systemic, chronic and inflammatory disease of unknown aetiology with a genetic predisposition. The advent of new biological agents, as well as the more traditional disease-modifying anti rheumatic drugs, has resulted in highly efficient therapies for reducing the symptoms and signs of RA; however, not all patients show the same level of response regarding disease progression to these therapies. These variations suggest that RA patients may have different genetic regulatory mechanisms. The extensive polymorphisms revealed in non-coding gene-regulatory regions in the immune system, as well as genetic variations in drug-metabolizing enzymes, suggest that this type of variation is of functional and evolutionary importance and may provide clues for developing new therapeutic strategies. Pharmacogenetics is a rapidly advancing area of research that holds the promise that therapies will soon be tailored to an individual patient's genetic profile.