Fascicles and the interfascicular matrix show adaptation for fatigue resistance in energy storing tendons

Tendon is composed of rope-like fascicles, bound together by interfascicular matrix (IFM). Our previous work shows that the IFM is critical for tendon function, facilitating sliding between fascicles to allow tendons to stretch. This function is particularly important in energy storing tendons, which experience extremely high strains during exercise, and therefore require the capacity for considerable inter-fascicular sliding and recoil. This capacity is not required in positional tendons. Whilst we have previously described the quasi-static properties of the IFM, the fatigue resistance of the IFM in functionally distinct tendons remains unknown. We therefore tested the hypothesis that fascicles and IFM in the energy storing equine superficial digital flexor tendon (SDFT) are more fatigue resistant than those in the positional common digital extensor tendon (CDET). Fascicles and IFM from both tendon types were subjected to cyclic fatigue testing until failure, and mechanical properties were calculated. The results demonstrated that both fascicles and IFM from the energy storing SDFT were able to resist a greater number of cycles before failure than those from the positional CDET. Further, SDFT fascicles and IFM exhibited less hysteresis over the course of testing than their counterparts in the CDET. This is the first study to assess the fatigue resistance of the IFM, demonstrating that IFM has a functional role within tendon and contributes significantly to tendon mechanical properties. These data provide important advances into fully characterising tendon structure-function relationships

Effect of fatigue loading on structure and functional behaviour of fascicles from energy-storing tendons

Tendons can broadly be categorized according to their function: those that act purely to position the limb and those that have an additional function as energy stores. Energy-storing tendons undergo many cycles of large deformations during locomotion, and so must be able to extend and recoil efficiently, rapidly and repeatedly. Our previous work has shown rotation in response to applied strain in fascicles from energy-storing tendons, indicating the presence of helical substructures which may provide greater elasticity and recovery. In the current study, we assessed how preconditioning and fatigue loading affect the ability of fascicles from the energy-storing equine superficial digital flexor tendon to extend and recoil. We hypothesized that preconditioned samples would exhibit changes in microstructural strain response, but would retain their ability to recover. We further hypothesized that fatigue loading would result in sample damage, causing further alterations in extension mechanisms and a significant reduction in sample recovery. The results broadly support these hypotheses: preconditioned samples showed some alterations in microstructural strain response, but were able to recover following the removal of load. However, fatigue loaded samples showed visual evidence of damage and exhibited further alterations in extension mechanisms, characterized by decreased rotation in response to applied strain. This was accompanied by increased hysteresis and decreased recovery. These results suggest that fatigue loading results in a compromised helix substructure, reducing the ability of energy-storing tendons to recoil. A decreased ability to recoil may lead to an impaired response to further loading, potentially increasing the likelihood of injury

An exploration of the ability of tepoxalin to ameliorate the degradation of articular cartilage in a canine in vitro model

<p>Abstract</p> <p>Background</p> <p>To study the ability of tepoxalin, a dual inhibitor of cyclooxygenase (COX) and lipoxygenase (LOX) and its active metabolite to reduce the catabolic response of cartilage to cytokine stimulation in an <it>in vitro </it>model of canine osteoarthritis (OA).</p> <p>Grossly normal cartilage was collected post-mortem from seven dogs that had no evidence of joint disease. Cartilage explants were cultured in media containing the recombinant canine interleukin-1<it>β </it>(IL-1<it>β</it>) at 100 ng/ml and recombinant human oncostatin-M (OSM) at 50 ng/ml. The effects of tepoxalin and its metabolite were studied at three concentrations (1 × 10^-5, 1 × 10^-6and 1 × 10^-7M). Total glycosaminoglycan (GAG) and collagen (hydroxyproline) release from cartilage explants were used as outcome measures of proteoglycan and collagen depletion respectively. PGE₂and LTB₄assays were performed to study the effects of the drug on COX and LOX activity.</p> <p>Results</p> <p>Treatment with IL-1<it>β </it>and OSM significantly upregulated both collagen (p = 0.004) and proteoglycan (p = 0.001) release from the explants. Tepoxalin at 10^-5M and 10^-6M caused a decrease in collagen release from the explants (p = 0.047 and p = 0.075). Drug treatment showed no effect on GAG release. PGE₂concentration in culture media at day 7 was significantly increased by IL-1<it>β </it>and OSM and treatment with both tepoxalin and its metabolite showed a trend towards dose-dependent reduction of PGE₂production. LTB₄concentrations were too low to be quantified. Cytotoxicity assays suggested that neither tepoxalin nor its metabolite had a toxic effect on the cartilage chondrocytes at the concentrations and used in this study.</p> <p>Conclusion</p> <p>This study provides evidence that tepoxalin exerts inhibition of COX and can reduce <it>in vitro </it>collagen loss from canine cartilage explants at a concentration of 10^-5M. We can conclude that, in this model, tepoxalin can partially inhibit the development of cartilage degeneration when it is available locally to the tissue.</p

Post-transcriptional gene regulation in chondrocytes

Abstract The control of gene expression in articular chondrocytes is an essential factor in maintaining the homoeostasis of extracellular matrix synthesis and turnover necessary in healthy articular cartilage. Although much is known of how steady-state levels of gene expression and rates of transcription are altered, there has been a poorer understanding of gene control at the post-transcriptional level and its relevance to cartilage health and disease. Now, an emerging picture is developing of the importance of this tier of gene regulation, driven by in vitro studies and mouse genetic models. This level of cellular regulation represents an as yet unexplored area of potential intervention for the treatment of degenerative cartilage disorders such as osteoarthritis

Donor age affects proteome composition of tenocyte-derived engineered tendon

All proteins identified by PEAKS in young and old tendon-derived TEC with correpsonding cellular sublocations defined by IPA and Matrisome Project. (XLSX 57 kb

Antimicrobial resistance in equine faecal Escherichia coli isolates from North West England

<p>Abstract</p> <p>Background</p> <p><it>Escherichia coli </it>isolates of equine faecal origin were investigated for antibiotic resistance, resistance genes and their ability to perform horizontal transfer.</p> <p>Methods</p> <p>In total, 264 faecal samples were collected from 138 horses in hospital and community livery premises in northwest England, yielding 296 resistant <it>E. coli </it>isolates. Isolates were tested for susceptibility to antimicrobial drugs by disc diffusion and agar dilution methods in order to determine minimum inhibitory concentrations (MIC). PCR amplification was used to detect genes conferring resistance to: ampicillin (TEM and SHV beta-lactamase), chloramphenicol (<it>catI, catII, catIII </it>and <it>cml</it>), tetracycline <it>(tetA, tetB, tetC, tetD, tet E </it>and <it>tetG</it>), and trimethoprim (<it>dfrA1, dfrA9, dfrA12, dfrA13, dfr7</it>, and <it>dfr17</it>).</p> <p>Results</p> <p>The proportion of antibiotic resistant isolates, and multidrug resistant isolates (MDR) was significantly higher in hospital samples compared to livery samples (MDR: 48% of hospital isolates; 12% of livery isolates, p < 0.001). Resistance to ciprofloxacin and florfenicol were identified mostly within the MDR phenotypes. Resistance genes included <it>dfr</it>, TEM beta-lactamase, <it>tet </it>and <it>cat</it>, conferring resistance to trimethoprim, ampicillin, tetracycline and chloramphenicol, respectively. Within each antimicrobial resistance group, these genes occurred at frequencies of 93% (260/279), 91%, 86.8% and 73.5%, respectively; with 115/296 (38.8%) found to be MDR isolates. Conjugation experiments were performed on selected isolates and MDR phenotypes were readily transferred.</p> <p>Conclusions</p> <p>Our findings demonstrate that <it>E. coli </it>of equine faecal origin are commonly resistant to antibiotics used in human and veterinary medicine. Furthermore, our results suggest that most antibiotic resistance observed in equine <it>E. coli </it>is encoded by well-known and well-characterized resistant genes common to <it>E. coli </it>from man and domestic animals. These data support the ongoing concern about antimicrobial resistance, MDR, antimicrobial use in veterinary medicine and the zoonotic risk that horses could potentially pose to public health.</p

SOX9 transduction of a human chondrocytic cell line identifies novel genes regulated in primary human chondrocytes and in osteoarthritis

The transcription factor SOX9 is important in maintaining the chondrocyte phenotype. To identify novel genes regulated by SOX9 we investigated changes in gene expression by microarray analysis following retroviral transduction with SOX9 of a human chondrocytic cell line (SW1353). From the results the expression of a group of genes (SRPX, S100A1, APOD, RGC32, CRTL1, MYBPH, CRLF1 and SPINT1) was evaluated further in human articular chondrocytes (HACs). First, the same genes were investigated in primary cultures of HACs following SOX9 transduction, and four were found to be similarly regulated (SRPX, APOD, CRTL1 and S100A1). Second, during dedifferentiation of HACs by passage in monolayer cell culture, during which the expression of SOX9 progressively decreased, four of the genes (S100A1, RGC32, CRTL1 and SPINT1) also decreased in their expression. Third, in samples of osteoarthritic (OA) cartilage, which had decreased SOX9 expression compared with age-matched controls, there was decreased expression of SRPX, APOD, RGC32, CRTL1 and SPINT1. The results showed that a group of genes identified as being upregulated by SOX9 in the initial SW1353 screen were also regulated in expression in healthy and OA cartilage. Other genes initially identified were differently expressed in isolated OA chondrocytes and their expression was unrelated to changes in SOX9. The results thus identified some genes whose expression appeared to be linked to SOX9 expression in isolated chondrocytes and were also altered during cartilage degeneration in osteoarthritis