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Matrix metalloproteinase-3 (MMP3) is a mediator of matrix remodelling and a proposed susceptibility locus in the genetic profile of musculoskeletal soft tissue injuries. Therefore, this study aimed to validate the MMP3 gene as a risk marker for these injuries by conducting a case control genetic association study in two independent samples groups. Three previously investigated MMP3 variants (rs679620, rs591058 and rs650108) in addition to the functional promoter variant (rs3025058) were genotyped in 195 Australian control participants and 79 Australian individuals with chronic Achilles tendinopathy. Similarly, 234 South African individuals with acute anterior cruciate ligament ruptures and 232 matched control participants were also analysed. Based on high linkage with the previously associated MMP3 variant rs679620, rs3025058 was inferred and found to be associated with increased risk for Achilles tendinopathy within the South African group (P = 0.012; OR: 2.88; 95% CI: 1.4 to 6.1). Lastly, the 6A-G-C-G haplotype, constructed from the investigated variants, was significantly associated with reduced risk for Achilles tendinopathy (29% CON vs. 20% TEN, P = 0.037) in the Australian group. In conclusion, a signal surrounding MMP3 is apparent with respect to Achilles tendinopathy. However, whether the investigated variants are contributing to injury susceptibility or whether they are merely linked to the risk conferring variants mapping elsewhere within the MMP gene cluster on chromosome 11, still requires refining.

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The proteins ELN and FBN2 are important in extracellular matrix function. The ELN rs2071307 and FBN2 rs331079 gene variants have been associated with soft tissue pathologies. We aimed to determine whether these variants were predisposing factors for both Achilles tendinopathy (AT) and anterior cruciate ligament (ACL) ruptures. For the AT study, 135 cases (TEN group) and 239 asymptomatic controls were recruited. For the ACL rupture study our cohort consisted of 141 cases (ACL group) and 219 controls. Samples were genotyped for both the ELN rs2071307 and FBN2 rs331079 variants using TaqMan assays. Analysis of variance and chi-squared tests were used to determine whether either variant was associated with AT or ACL rupture with significance set at p<0.05. The GG genotype of the FBN2 variant was significantly over-represented within the TEN group (p=0.035; OR=1.83; 95% CI 1.04-3.25) compared to the CON group. We also found that the frequency of the G allele was significantly different between the TEN (p=0.017; OR=1.90; 95% CI 1.11-3.27) and ACL groups (p=0.047; OR=1.76; 95% CI 1.00-3.10) compared to controls. The ELN rs207137 variant was not associated with either AT or ACL rupture. In conclusion, DNA sequence variation within the FBN2 gene is associated with both AT and ACL rupture.

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INTRODUCTION: Rheumatoid arthritis (RA) patients can be classified based on presence or absence of anticitrullinated peptide antibodies (ACPA) in their serum. This heterogeneity among patients may reflect important biological differences underlying the disease process. To date, the majority of genetic studies have focused on the ACPA-positive group. Therefore, our goal was to analyse the genetic risk factors that contribute to ACPA-negative RA. METHODS: We performed a large-scale genome-wide association study (GWAS) in three Caucasian European cohorts comprising 1148 ACPA-negative RA patients and 6008 controls. All patients were screened using the Illumina Human Cyto-12 chip, and controls were genotyped using different genome-wide platforms. Population-independent analyses were carried out by means of logistic regression. Meta-analysis with previously published data was performed as follow-up for selected signals (reaching a total of 1922 ACPA-negative RA patients and 7087 controls). Imputation of classical HLA alleles, amino acid residues and single nucleotide polymorphisms was undertaken. RESULTS: The combined analysis of the studied cohorts resulted in identification of a peak of association in the HLA-region and several suggestive non-HLA associations. Meta-analysis with previous reports confirmed the association of the HLA region with this subset and an observed association in the CLYBL locus remained suggestive. The imputation and deep interrogation of the HLA region led to identification of a two amino acid model (HLA-B at position 9 and HLA-DRB1 at position 11) that accounted for the observed genome-wide associations in this region. CONCLUSIONS: Our study shed light on the influence of the HLA region in ACPA-negative RA and identified a suggestive risk locus for this condition.

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BACKGROUND: Radiological damage is an important outcome measure in rheumatoid arthritis (RA), both for research and clinical purposes. Depending on the setting, both hands and feet are radiographed, or only a part of these. It is unknown whether radiographing part of the four extremities gives comparable information to radiographing both hands and feet. This study therefore aimed to compare the radiological information obtained both when evaluating single time point radiographs and progression over time, in early and advanced RA. METHODS: 6261 sets of hands and feet x-rays of 2193 RA patients from Leiden, Groningen (both from The Netherlands) and North America were studied. Correlations between joint damage at different regions were compared (unilateral vs bilateral and hands vs feet). Analyses were done at single time points (cross-sectional) and for progression over time (longitudinal), both for continuous severity measures (Sharp/van der Heijde score; SHS) and binomial measures of erosiveness. RESULTS: When studying single time points, the severity of joint damage (SHS) is highly correlated between left and right, but weakly correlated between hands and feet. Correlation coefficients were higher in advanced than early RA. These findings were comparable in the three datasets. When evaluating erosiveness using only unilateral x-rays or hands without feet, 19.3% and 24.0-40.4% are incorrectly classified as non-erosiveness. Similarly, when evaluating disease progression by imaging only unilateral x-rays or only hand x-rays, progression would have been missed in 11.6-16.2% and 21.2-31.0% of patients. CONCLUSION: Performing x-rays of both hands and feet yields additive information compared with imaging only a part of these.

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A recent genetic association study has revealed that a variant (rs143383) within the 5'-untranslated region of the growth differentiation factor 5 gene (GDF5) associates with the risk of Achilles tendon pathology. The aim of this study was to determine whether this variant associates with the risk of ACL rupture. A cohort of 126 Caucasians with ACL rupture (ACL group), including 51 subjects who ruptured their ACL through a non-contact mechanism (NON sub-group), and 214 controls (CON group) were genotyped for the rs143383 variant. We report no significant GDF5 rs143383 genotype (P=0.396) or allele (P=0.810) frequency differences between the ACL (TT genotype, n=37, 29%; CT genotype, n=72, 57%; CC genotype, n=17, 14%) and CON (TT genotype, n=73, 34%; CT genotype, n=106, 50%; CC genotype, n=35, 16%) groups. There were also no significant differences between the NON sub-group and the CON group (allele; P=0.710, genotype; P=0.771). Furthermore, in gender specific analysis we found no association between rs143383 and ACL in either males (allele; P=0.988, genotype; P=0.407) or females (allele; P=0.643, genotype; P=0.885), respectively. Nor were there any gender specific associations between the NON sub-group and either genotype or allele. In conclusion, the rs143383 variant was not found to associate with the risk of ACL rupture.

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Musculoskeletal soft tissue injuries such as Achilles tendinopathy and anterior cruciate ligament ruptures are common among elite athletes, recreational athletes and physically active individuals. The consequences of injury may be devastating and prevent the recreational or competitive athlete from reaching their potential or lead to a premature end to their careers. Although these injuries have been well described at a clinical level, the biological mechanisms causing these injuries are poorly understood. A further understanding of the biological mechanisms underlying the injury will assist the treatment and management of these injuries. In addition, understanding the biology is an important prerequisite in developing models that can be used to effectively identify risk, as well as, implement personalized prevention, treatment and rehabilitation programmes. Both intrinsic, including genetic variants, and extrinsic risk factors have nevertheless been implicated in the aetiology of these injuries. To date, several patents have been filed which involve the use of specific polymorphisms and regions within specific genes to be used in a genetic test for either tendon or ligament injury risk. The objective of this manuscript will be to review the evidence for the genetic predisposition to soft tissue injury, as well as the application of this data in the prevention, treatment and management of musculoskeletal soft tissue injuries.

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BACKGROUND: Interleukin (IL)-15 levels are increased in serum, synovium and bone marrow of patients with rheumatoid arthritis (RA). IL-15 influences both the innate and the adaptive immune response; its major role is activation and proliferation of T cells. There are also emerging data that IL-15 affects osteoclastogenesis. The authors investigated the association of genetic variants in IL15 with the rate of joint destruction in RA. METHOD: 1418 patients with 4885 x-ray sets of both hands and feet of four independent data sets were studied. First, explorative analyses were performed on 600 patients with early RA enrolled in the Leiden Early Arthritis Clinic. Twenty-five single-nucleotide polymorphisms (SNPs) tagging IL-15 were tested. Second, SNPs with significant associations in the explorative phase were genotyped in data sets from Groningen, Sheffield and Lund. In each data set, the relative increase of the progression rate per year in the presence of a genotype was assessed. Subsequently, data were summarised in an inverse weighting meta-analysis. RESULTS: Five SNPs were significantly associated with rate of joint destruction in phase 1 and typed in the other data sets. Patients homozygous for rs7667746, rs7665842, rs2322182, rs6821171 and rs4371699 had respectively 0.94-, 1.04-, 1.09-, 1.09- and 1.09-fold rate of joint destruction compared to other patients (p=4.0×10(-6), p=3.8×10(-4), p=5.0×10(-3), p=5.0×10(-3) and p=9.4×10(-3)). DISCUSSION: Independent replication was not obtained, possibly due to insufficient power. Meta-analyses of all data sets combined resulted in significant results for four SNPs (rs7667746, p<0.001; rs7665842, p<0.001; rs4371699, p=0.01; rs6821171, p=0.01). These SNPs were also significant after correction for multiple testing. CONCLUSION: Genetic variants in IL-15 are associated with progression of joint destruction in RA.

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As matrix metalloproteinases (MMPs) are critical to ligament homeostasis and integrity, the aim of this study was to investigate whether four functional polymorphisms within four MMP genes, which cluster on chromosome 11q22 associate with risk of ACL ruptures. Three hundred and forty-five [129 with ACL ruptures (ACL group) and 216 asymptomatic controls (CON group)] unrelated Caucasians were recruited for this case-control study. Fifty-four participants reported non-contact mechanisms of ACL rupture (NON subgroup). All participants were genotyped for the MMP10 C/T rs486055, MMP1 1G/2G rs1799750, MMP3 G/A rs679620 and MMP12 A/G rs2276109 variants. After adjusting for sex, age and weight, the AG and GG genotypes of the MMP12 rs2276109 variant were significantly (P=0.030) under-represented among the NON subgroup (14%), when compared with the CON group (26%). No other variants were significantly different between groups. Adjusted for the same confounders, the two four-variant haplotypes T-1G-A-A (CON 14%, ACL 9%, P=0.033) and C-2G-G-G (CON 14%, NON 5%, P=0.021) were significantly different between the CON and the ACL groups, and the CON group and the NON subgroup, respectively. This is the first report that indicates an association between the chromosomal region 11q22 and the risk of ACL rupture.

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Mutations in the type VI collagen gene ( COL6A1) cause myopathy and muscle weakness. In addition, COL6A1 knockout mice were shown to have impaired running performance and reduced muscle strength. The COL6A1 rs35796750 polymorphism (IVS32-29 T/C) has been associated with complex phenotypes. The aim of this study was therefore to determine if this polymorphism is associated with performance during the 226 km Ironman triathlon. Participants (n=661) were recruited during 4 South African Ironman triathlons. Finishing times for the 3.8 km swim, 180 km bike, 42.2 km run, and overall race were provided by the race organisers. All participants were genotyped for the COL6A1 rs35796750 polymorphism. Participants with the COL6A1 TT genotype were significantly faster during the bike (p=0.014) and overall race (p=0.030). When participants were grouped into fast, middle and slow bike finishing time tertiles, there was a significant linear trend for the TT genotype (Fast: TT=35.7%; Middle: TT=29.0%; Slow: TT=23.8%; p=0.008). No significant genotype frequency differences were observed for the swim or run of the triathlon. In conclusion, the COL6A1 gene is therefore a potential marker for endurance cycling performance. These effects may be mediated through changes to the composition of type VI collagen containing tissues, such as muscle and tendon.

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BACKGROUND: Anterior cruciate ligament (ACL) ruptures are considered the most severe injury sustained in sports. Although various intrinsic and extrinsic risk factors have been identified, the exact aetiology of the injury is not yet fully understood. Recently, the gene encoding for the alpha1 chain of type I collagen (COL1A1) has been shown to be associated with cruciate ligament ruptures and shoulder dislocations. OBJECTIVE: To determine whether the functional Sp1 binding site polymorphism within intron 1 of the COL1A1 gene is associated specifically with ACL ruptures in an independent population. METHODS: 117 Caucasian participants with surgically diagnosed ACL ruptures, and 130 Caucasian physically active controls without any history of previous ligament or tendon injuries were recruited for this case-control genetic association study. All participants were genotyped for the COL1A1 Sp1 binding site polymorphism (G/T; rs1800012). RESULTS: The rare TT genotype was significantly (p = 0.031, OR = 0.08, 95% CI <0.01 to 1.46) under-represented in the ACL group (0 out of 117, 0%), compared with the controls (6 out of 130, 4.6%). CONCLUSION: The TT genotype of the COL1A1 Sp1 binding site polymorphism was significantly under-represented in South African participants with ACL ruptures. We propose that this sequence variant be the first specific genetic element to be included in multifactorial models developed to understand the aetiology and risk factors for ACL rupture.

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OBJECTIVES: Despite the important role of the transcription factor HIF-1alpha in angiogenesis and inflammation, only a few studies on HIF-1alpha expression have been performed in RA patients. The aim of the present study was to identify the layer in synovial tissue of RA patients where HIF1a is expressed and to find out whether HIF-1alpha expression is related to both angiogenesis and inflammation in synovium from RA patients. METHODS: A reproducible staining method for HIF-1alpha was developed. HIF-1alpha -positive cells were quantified in synovial tissue from patients with RA. As control we used synovial tissue from patients with osteoarthritis (OA). The number of HIF-1alpha-positive cells was compared with the number of blood vessels present and was correlated with the amount of inflammation. The amount of inflammation was determined by counting inflammatory cells, by estimating the proliferation marker Ki67 in inflamed tissue, and by using a recently published synovitis score which gives an accurate estimate of the amount of inflammation present. RESULTS: HIF-1alpha was expressed weakly in the lining layer and strongly in the sublining layer in RA synovial tissue. In contrast, HIF-1alpha was only weakly expressed in OA synovial tissue. The number of HIF-1alpha -positive cells correlated strongly with the number of blood vessels in RA synovial tissue and with inflammatory endothelial cell infiltration (blood vessels), cell proliferation (Ki67) and the synovitis score. CONCLUSIONS: HIF-1alpha expression is strongest in the sub-lining layer of RA synovium and is related to both angiogenesis and inflammation in synovium from RA patients. These results thus suggest that HIF-1alpha could serve as an important new therapeutic target in RA, targeting both angiogenesis and inflammation.

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Genes encoding for tenascin C and a subunit of type V collagen have previously been reported to be associated with Achilles tendon injuries. Types XII and XIV collagen may be involved in similar biological processes as these proteins in tendons. The aim of this study was therefore to test the association between polymorphisms within COL12A1 and COL14A1 and Achilles tendon injuries. Restriction fragment length polymorphism (RFLP) analysis was used to identify the relative frequencies of two polymorphisms within each of the COL12A1 and COL14A1 genes within 137 subjects with clinical symptoms of Achilles tendon injuries, consisting of 93 with Achilles tendinopathy and 44 with Achilles tendon rupture, and 131 asymptomatic control subjects. No statistically significant differences were identified in the genotype, allele or haplotype distributions between the affected and control subjects. The findings from this study suggest that although COL12A1 and COL14A1 are involved in similar biological processes as TNC and COL5A1, the polymorphisms tested are not associated with clinical symptoms of Achilles tendon injury within the investigated population.

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Differences in allelochemistry of plants may influence their ability to attract parasitoids. We studied responses of Diadegma semiclausum (Hellén), a parasitoid of the diamondback moth (Plutella xylostella L.), to inter- and intraspecific variation in odor blends of crucifers and a non-crucifer species. Uninfested Brussels sprout (Brassica oleracea L. gemmifera), white mustard (Sinapis alba L.), a feral Brassica oleracea, and malting barley (Hordeum vulgare L.) were compared for their attractivity to D. semiclausum in a Y-tube bioassay. Odors from all plants were more attractive to the parasitoid than clean air. However, tested against each other, parasitoids preferred the volatile blend from the three cruciferous species over that of malting barley. Wasps also discriminated between uninfested crucifers: mustard was as attractive as feral B. oleracea, and both were more attractive than Brussels sprout. Attractivity of uninfested plants was compared with that of plants infested by larvae of the host P. xylostella. Host-infested mustard and Brussels sprout were more attractive than uninfested conspecifics. Interestingly, the volatile blends of uninfested white mustard and infested Brussels sprout were equally attractive. We also compared the volatile composition of different plant sources by collecting headspace samples and analysing them with GC-MS. Similarities of volatile profiles were determined by hierarchic clustering and non-metric scaling based on the Horn-index. Due to the absence of several compounds in its blend, the volatile profile of barley showed dissimilarities from blends of crucifers. The odor profile of white mustard was distinctly different from the two Brassicaceae. Feral Brassica oleracea odor profile was different from infested Brussels sprout, but showed overlap with uninfested Brussels sprout. Odor blends from infested and uninfested Brussels sprout were similar, and mainly quantitative differences were found. D. semiclausum appears to discriminate based on subtle differences in volatile composition of odor blends from infested and uninfested plants.

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An important group of antimalarial drugs consists of the endoperoxide sesquiterpene lactone artemisinin and its derivatives. Only little is known about the biosynthesis of artemisinin in Artemisia annua L., particularly about the early enzymatic steps between amorpha-4,11-diene and dihydroartemisinic acid. Analyses of the terpenoids from A. annua leaves and gland secretory cells revealed the presence of the oxygenated amorpha-4,11-diene derivatives artemisinic alcohol, dihydroartemisinic alcohol, artemisinic aldehyde, dihydroartemisinic aldehyde and dihydroartemisinic acid. We also demonstrated the presence of a number of biosynthetic enzymes such as the amorpha-4,11-diene synthase and the--so far unknown--amorpha-4,11-diene hydroxylase as well as artemisinic alcohol and dihydroartemisinic aldehyde dehydrogenase activities in both leaves and glandular trichomes. From these results, we hypothesise that the early steps in artemisinin biosynthesis involve amorpha-4,11-diene hydroxylation to artemisinic alcohol, followed by oxidation to artemisinic aldehyde, reduction of the C11-C13 double bond to dihydroartemisinic aldehyde and oxidation to dihydroartemisinic acid.

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BACKGROUND: Azathioprine is widely used in Crohn's disease. A major drawback is the occurrence of side-effects, especially acute pancreatitis. Acute pancreatitis is rarely seen when azathioprine is used for other diseases than Crohn's disease. AIM: To survey side-effects of azathioprine after liver or renal transplantation, for systemic lupus erythematosis, Wegener's granulomatosis, autoimmune hepatitis, rheumatoid arthritis, ulcerative colitis or Crohn's disease. METHODS: A computerized search using the term 'azathioprine' or 'imuran' was performed on the Hospital Information System of the university hospital Groningen, resulting in 1564 patients matching our criteria. RESULTS: Eleven of 224 patients with Crohn's disease experienced acute pancreatitis (4.9%) compared with two of 129 (1.5%) with autoimmune hepatitis, two of 388 (0.5%) after renal transplantation, one of 254 (0.4%) after liver transplantation. Acute pancreatitis was more prevalent in Crohn's disease compared with any other disease. Azathioprine-toxicity necessitating withdrawal occurred significantly (P < 0,05) more in rheumatoid arthritis (78 of 317), ulcerative colitis (20 of 94) and Crohn's disease (52 of 224) compared with systemic lupus erythematosis (five of 73), Wegener's granulomatosis (six of 85), autoimmune hepatitis (eight of 129), after liver transplantation (17 of 254) and after renal transplantation (22 of 388). CONCLUSIONS: Acute pancreatitis is strongly associated with Crohn's disease and rarely occurs with other underlying conditions. Overall azathioprine-induced toxicity and the necessity of withdrawal is more common in inflammatory bowel disease and rheumatoid arthritis compared with other diseases.

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OBJECTIVE: To evaluate serum matrix metalloproteinase 3 (MMP-3) levels in comparison to C-reactive protein (CRP) in periods with and without progression of radiological damage in patients with early rheumatoid arthritis (RA). METHODS: Thirty-two patients with RA and radiological progression (> or = 5 points according to the Sharp/van der Heijde method) during 6 months followed by a 6-month period without radiological progression (< or = 1 point) were selected from a prospective follow-up study of early RA patients. Serum MMP-3 levels, CRP, the erythrocyte sedimentation rate (ESR), disease activity index (DAS), swollen joint count (SJC), tender joint count (TJC), and Ritchie articular index (RAI) were measured monthly and results were transformed into mean values for the 6-month periods. RESULTS: During the period with radiological progression the mean serum MMP-3 correlated significantly with the mean CRP (r = 0.68, p < 0.001), ESR (r = 0.54, p = 0.001) and swollen joint count (r = 0.48, p = 0.006). In the period without radiological progression the mean serum MMP-3 only correlated with the mean CRP (r = 0.44, p = 0.012). Individual changes--expressed in percentages (%)--between the two periods showed a decrease in both the mean serum MMP-3 and CRP in 19 and an increase in 3 patients, in parallel with other markers of disease activity in these patients (69% of cases). The individual change (%) in mean serum MMP-3 or CRP did not correlate with the difference in radiological progression between the two periods. CONCLUSIONS: Serum MMP-3 and CRP are closely related and there seems to be no difference between serum MMP-3 and CRP with regard to the monitoring of the progression of radiological damage.

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Many plant species defend themselves against herbivorous insects indirectly by producing volatiles in response to herbivory. These volatiles attract carnivorous enemies of the herbivores. Research on the model plant Arabidopsis thaliana (L.) Heynh. has contributed considerably to the unraveling of signal transduction pathways involved in direct plant defense mechanisms against pathogens. Here, we demonstrate that Arabidopsis is also a good candidate for studying signal transduction pathways involved in indirect defense mechanisms by showing that: (1) Adult females of Cotesia rubecula, a specialist parasitic wasp of Pieris rapae caterpillars, are attracted to P. rapae-infested Arabidopsis plants. (2) Arabidopsis infested by P. rapae emits volatiles from several major biosynthetic pathways, including terpenoids and green leaf volatiles. The blends from herbivore-infested and artificially damaged plants are similar. However, differences can be found with respect to a few components of the blend, such as two nitriles and the monoterpene myrcene, that were produced exclusively by caterpillar-infested plants, and methyl salicylate, that was produced in larger amounts by caterpillar-infested plants. (3) Genes from major biosynthetic pathways involved in volatile production are induced by caterpillar feeding. These include AtTPS10, encoding a terpene synthase involved in myrcene production, AtPAL1, encoding phenylalanine ammonia-lyase involved in methyl salicylate production, and AtLOX2 and AtHPL, encoding lipoxygenase and hydroperoxide lyase, respectively, both involved in the production of green leaf volatiles. AtAOS, encoding allene oxide synthase, involved in the production of jasmonic acid, also was induced by herbivory.

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