Genome-wide analysis identifies differential promoter methylation of Leprel2, Foxf1, Mmp25, Igfbp6, and Peg12 in murine tendinopathy.

We have used a murine Achilles tendinopathy model to investigate whether tissue changes (such as collagen disorganization, chondroid metaplasia, and loss of tensile properties) which are broadly characteristic of human tendinopathies, are accompanied by changes in the expression of chromatin-modifying enzymes and the methylation status of promoter regions of tendon cell DNA. Tendinopathy was induced by two intra-tendinous TGF-ß1 injections followed by cage activity or treadmill running for up to 28 days. Activation of DNA methyltransferases occurred at 3 days after the TGF-ß1 injections and also at 14 days, but only with treadmill activity. Genome-wide Methyl Mini-Seq™ analysis identified 19 genes with differentially methylated promoters, five of which perform functions with an apparent direct relevance to tendinopathy (Leprel2, Foxf1, Mmp25, Igfbp6, and Peg12). The functions of the genes identified included collagen fiber assembly and pericellular interactions, therefore their perturbation could play a role in the characteristic disorganization of fibers in affected tendons. We postulate that a study of the functional genomics of these genes in animal and human tendon could further delineate the pathogenesis of this multi-factorial complex disease. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:947-955, 2017.

Biomechanical Evaluation of Posterior Cruciate Ligament Reconstruction With Quadriceps Versus Achilles Tendon Bone Block Allograft.

BACKGROUND: Long-term studies of posterior cruciate ligament (PCL) reconstruction suggest that normal stability is not restored in the majority of patients. The Achilles tendon allograft is frequently utilized, although recently, the quadriceps tendon has been introduced as an alternative option due to its size and high patellar bone density. PURPOSE/HYPOTHESIS: The purpose of this study was to compare the biomechanical strength of PCL reconstructions using a quadriceps versus an Achilles allograft. The hypothesis was that quadriceps bone block allograft has comparable mechanical properties to those of Achilles bone block allograft. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-nine fresh-frozen cadaveric knees were assigned to 1 of 3 groups: (1) intact PCL, (2) PCL reconstruction with Achilles tendon allograft, or (3) PCL reconstruction with quadriceps tendon allograft. After reconstruction, all supporting capsular and ligamentous tissues were removed. Posterior tibial translation was measured at neutral and 20° external rotation. Each specimen underwent a preload, 2 cyclic loading protocols of 500 cycles, then load to failure. RESULTS: Construct creep deformation was significantly lower in the intact group compared with both Achilles and quadriceps allograft (P = .008). The intact specimens reached the greatest ultimate load compared with both reconstructions (1974 ± 752 N, P = .0001). The difference in ultimate load for quadriceps versus Achilles allograft was significant (P = .048), with the quadriceps group having greater maximum force during failure testing. No significant differences were noted between quadriceps versus Achilles allograft for differences in crosshead excursion during cyclic testing (peak-valley [P-V] extension stretch), creep deformation, or stiffness. Construct stiffness measured during the failure test was greatest in the intact group (117 ± 9 N/mm, P = .0001) compared with the Achilles (43 ± 11 N/mm) and quadriceps (43 ± 7 N/mm) groups. CONCLUSION: While the quadriceps trended to be a stronger construct with a greater maximum load and stiffness required during load to failure, only maximum force in comparison with the Achilles reached statistical significance. Quadriceps and Achilles tendon allografts had similar other biomechanical characteristics when used for a PCL reconstruction, but both were inferior to the native PCL. CLINICAL RELEVANCE: The quadriceps tendon is a viable graft option in PCL reconstruction as it exhibits a greater maximum force and is otherwise comparable to the Achilles allograft. These findings expand allograft availability in PCL reconstruction.

Recent Scientific Advances Towards the Development of Tendon Healing Strategies.

There exists a range of surgical and non-surgical approaches to the treatment of both acute and chronic tendon injuries. Despite surgical advances in the management of acute tears and increasing treatment options for tendinopathies, strategies frequently are unsuccessful, due to impaired mechanical properties of the treated tendon and/or a deficiency in progenitor cell activities. Hence, there is an urgent need for effective therapeutic strategies to augment intrinsic and/or surgical repair. Such approaches can benefit both tendinopathies and tendon tears which, due to their severity, appear to be irreversible or irreparable. Biologic therapies include the utilization of scaffolds as well as gene, growth factor, and cell delivery. These treatment modalities aim to provide mechanical durability or augment the biologic healing potential of the repaired tissue. Here, we review the emerging concepts and scientific evidence which provide a rationale for tissue engineering and regeneration strategies as well as discuss the clinical translation of recent innovations.

Development and implementation of a custom program for post hoc strain tracking in biological specimens using cross-correlation - biomed 2011.

The research presented describes the development of a custom MATLAB® program designed to examine changes in surface strain based on digital image tracking, a technique that employs markerless tracking to access regional displacement in digital images. Strain tracking is accomplished through the analysis of successive images taken during testing using a dedicated black and white camera incorporated into a tensile testing system. In the tracking program a 2-D array of grid points is mapped on the initial image from a test. Each grid point consists of a pixel array (a sub-image corresponding to a “marker”) which is then compared to consecutive images to determine the new grid point placement using cross correlation. By analyzing marker position post hoc, the number of grid points, the size of the sub-pixel array, and the spacing (longitudinal and/or regional) between grid points can be varied to account for differences in observed responses. Digital strain tracking allows for a test to be reanalyzed and eliminates the need to affix markers in specified patterns to a sample prior to testing. The new “markerless” tracking approach has been compared to the classic procedure of applying physical surface markers for tracking strain, to determine the accuracy of this technique. Preliminary testing revealed that adding texture to the specimen may be necessary (especially for low texture samples like tendons and ligaments), through the use of glitter derivatives, to increase visual contrast between multiple grid points.