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Nineteen fresh frozen adult human flexor digitorum profundus (FDP) tendons in Zone II were studied to compare the differences in material properties between the dorsal (dFDP) and palmar (pFDP) side of each tendon biomechanically, biochemically and histologically. We have found that tissue from the dorsal side of each flexor tendon has (1) greater strength; (2) less collagen crosslinking (hydroxypyridinium); and (3) a larger single bundle cross-sectional area than tissue from the palmar side of the same tendon. These data clearly demonstrate that the dorsal and palmar sides of the adult human (FDP) tendon in Zone II differ materially. These differences suggest that there may be biomechanical advantages in placing core sutures dorsally when repairing flexor tendons, a technique that we have previously described.

Rotator cuff repair (RCR) is a crucial surgical procedure, but has unacceptable mechanical failure rates between 25–60%. Examining supplemental synergistic interventions, such as biological augmentations (ex: growth factors) to improve fibrocartilage formation rather than scar tissue formation, would make tears more amenable to surgical repair. Due to the large number of agents and application methods (and times), improved techniques are needed for assessing RCR in animals. In particular, high-resolution real-time imaging is needed to guide tissue engineering in animal models. Optical coherence tomography (OCT) is well suited for this role, with resolutions 25 × greater than any clinical imaging modality and an ability to identify organized collagen with polarization sensitive techniques. For example, it can determine severe collagen depletion in visually normal tendons. The images here show the first OCT and PS-OCT of the rotator cuff in male Wistar rats. The structure of the supraspinatus tendon, enthesis, and humerus are well defined. For histological comparison, this sample was stained with both Masson's Trichrome, to expose any structural abnormalities, and Picrosirius Red, to determine collagen content using a polarization filter. OCT studies offer the potential of understanding RCR failure mechanisms and potential tissue altering agents, substantially impacting outcomes.

Cartilage can redistribute human body’s daily loads and decrease the friction force in the diarthrodial joints. However, it may be injured due to trauma, sports injury, biomechanical imbalance, and genetic disease. Microfracture (MF), osteochondral autograft transplantation (OAT), and autologous chondrocyte implantation (ACI) are the most common treatment procedures in the hospital. Recently, the concept of tissue engineering involving the combination of cells, scaffolds, and bioactive signals has inspired researchers. Our team of researchers synthesized a tri-copolymer from biological polymer by using gelatin, chondroitin-6-sulfate, and hyaluronic acid through cross-linking reaction. Lacuna formation could be seen in the tri-copolymer surrounding the chondrocytes, and some newly formed glycosaminoglycan was found in the engineered cartilage. Considering the dedifferentiation possibility of chondrocyte, bone marrow mesenchymal stem cells (BMSCs) become an ideal cell source for cartilage tissue regeneration, since they can be easily harvested from adult tissue, and be expanded in vitro. In an in-vivo porcine pilot study, the results showed that the defect site could be regenerated by BMSCs/collagen gel, and is formed with fibro/hyaline mixed cartilage tissue after implantation for six months. Several clinical studies using BMSCs for cartilage defect treatment were also conducted recently; clinical outcomes such as IKDC, Lysholm, and Tegner scores improved when the cartilage defects were repaired by several millions of mesenchymal stem cells, and there is no tumor formation after being treated with BMSCs during the 10-year follow-up. Moreover, recently a commercial BMSCs/collagen gel composite for cartilage repair was developed in Taiwan and clinical trial was conducted in 2008; the results showed that there is an improvement in IKDC and MRI scores during the nine-year follow-up. It seems that using an engineered cartilage made from BMSCs/collagen gel for cartilage defect treatment is a promising method.

The chemical reactions and physical effects involved in the cessation of bone formation with age, the formation of blood and other cells in bone marrow plus the development of osteoporosis and the link of the latter to anaemia and diabetes are reconsidered with respect to the physical and biochemical conditions present in the human body.

The present study was performed to establish whether intact human tendons exhibit time-dependent tensile properties, as they do in the in vitro state. Measurements were taken in seven men and involved ultrasound-based recording of the gastrocnemius tendon elongation during three sets of five repeated isometric plantarflexion contractions elicited by tetanic electrical stimulation. The plantarflexion moment corresponding to the tendon elongation in the fifth contraction presented a pattern dependent on the voltage applied: it was approximately constant when applying 50% of maximal voltage, but it decreased curvilinearly as a function of contraction number when applying 70 and 100% of maximal voltage, reaching in the fifth contraction 84% of the plantarflexion moment corresponding to the elongation examined in the first contraction. These results suggest that, once a threshold tendon elongation is undergone, in vivo tendons may exhibit substantial viscoelasticity. The present findings have implications for muscle and joint function and need to be accounted for by musculoskeletal models.

There have been no previous reports of tendon tissue engineering using mesenchymal stem cells (MSCs) with regard to quantitative evaluation of protein expression levels and observation of derived extracellular matrix (ECM) state. Therefore, we approached tendon tissue engineering from both perspectives. Human bone marrow MSCs (hBMSCs) were subjected to 8% or 10% cyclic stretching at 1 Hz to promote differentiation into tenocytes and ECM production. The type I collagen (Col I) and Tenascin-C (Tnc) protein expression levels were evaluated quantitatively by enzyme-linked immunosorbent assay (ELISA). Confocal fluorescence microscopy was employed to observe the derived ECM state. Col I state derived from 10%-stretched cells as ECM was elongated like actual tendon ECM, although the quantitative protein expression levels were slightly higher in 8%-stretched cells. The results suggested that the optimal uniaxial stretching ratio was different between protein expression levels and derived ECM state. Therefore, it is important to pay attention to both protein expression levels and ECM state in tendon tissue engineering.

Bone is a multiscale combination of collagen molecules merged with mineral crystals. Its high rigidity and stability stem amply from its polymeric organic matrix and secondly from the connections established between interdifferent and intradifferent scale components through cross-links. Several studies have shown that the cross-links inhibition results in a reduction in strength of bone but they do not quantify the degree to which these connections contribute to the bone rigidity and toughness. This report is classified among the few works that measure the cross-links multiscale impact on the ultrastructure bone mechanical behavior.

This work aims firstly to study the effect of cross-links at the molecule scale and secondly to gather from literature studies results handling with cross-links effects on the other bone ultrastructure scales in order to reveal the multiscale effect of cross-links. This study proves that cross-links increasing number improves the mechanical performance of each scale of bone ultrastructure. On the other hand, cross-links have a multiscale contribution that depends on its rank related to existing cross-links connecting the same geometries and it depends on mechanical characteristics of geometries connected.

Pathological analysis as well as biomechanical methods are powerful approaches for collagen assessment, which plays an important role in understanding the wound healing process and choosing a treatment method in clinical situations. Due to the limitations of preparing and evaluating pathological images, this study was designed to establish a machine learning technique to predict the wound collagen content through its biomechanical parameters. For this purpose, the artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) were compared. The wound was created with an incision on the back of 30 male BALB/c mice. On the 7th and 14th days, animals were sacrificed and 60 wound tissue samples were evaluated using histopathological and biomechanical methods to quantify the amount of collagen and wound tensile strength to feed the ANN and ANFIS developed models. Based on the results, both models have appropriate performance to predict the wound collagen content. However, the comparison of coefficient of determination ($R^2$) and root mean square error (RMSE) for testing dataset revealed that ANN ($R^2=0.95$, $\mathrm{\text{RMSE}}=0.29$) had more prediction capability than ANFIS ($R^2=0.84$, $\mathrm{\text{RMSE}}=0.87$). As a decision support system, ANN model could assist in the evaluation of wound healing process with collagen values prediction.

Tissue engineering is an innovative field of research applied to treat intestinal diseases. Engineered smooth muscle requires dense smooth muscle tissue and robust vascularization to support contraction. The purpose of this study was to use heparan sulfate (HS) and collagen coatings to increase the attachment of smooth muscle cells (SMCs) to scaffolds and improve their survival after implantation. SMCs grown on biologically coated scaffolds were evaluated for maturity and cell numbers after 2, 4 and 6 weeks in vitro and both 2 and 6 weeks in vivo. Implants were also assessed for vascularization. Collagen-coated scaffolds increased attachment, growth and maturity of SMCs in culture. HS-coated implants increased angiogenesis after 2 weeks, contributing to an increase in SMC survival and growth compared to HS-coated scaffolds grown in vitro. The angiogenic effects of HS may be useful for engineering intestinal smooth muscle.

Background: Dupuytren disease (DD) is characterised by increased myofibroblast/fibroblast activity and type3/type1 collagen ratios. Hyaluronic acid (HA) is major component of the extracellular matrix and some studies have showed that HA limits myofibroblast activity and decreases type3/type1 collagen ratio. The aim of this study is to determine the effect of the ex-vivo application of HA on cultured fibroblasts obtained from normal and diseased tissue from patients with DD. This is the initial step towards defining the use of HA as a new approach for medical treatment of DD.

Methods: Tissue samples were obtained from both healthy forearm (C) and unhealthy palmar (D) fascia of patients undergoing surgery for DD. Tissue samples were cultured and divided into four groups depending on the addition of HA [C(HA−), C(HA+), D(HA−) and D(HA+)]. The tissues were evaluated using Western blot to detect effect of HA on myofibroblast (by measuring alpha smooth muscle actin [α-SMA) and on the ratio of type3/type1 collagen by measuring collagen type1 alpha 1 Chain (COL1A1) and collagen type3 alpha 1 Chain (COL3A1).

Results: The rate of the average α-SMA value in the D(HA+) group was significantly lower compared to that of the D(HA−) group. The average ratio of type3/type1 collagen in the D(HA+) group was significantly lower compared to the D(HA−) group.

Conclusions: The ex-vivo application of HA on cultured fibroblasts obtained from patients with DD resulted in a decrease in myofibroblast/fibroblast activity and type3/type1 collagen ratios. This may pave the way for clinical application of HA in the treatment of DD.

In the treatment of wound, a good understanding of the principles of wound healing is essential. A moist wound healing environment is needed. A range of new generation dressings has emerged in addition to traditional dressings such as gauze and tulle gras. These include low-adhesive dressings, transparent dressings, hydrocolloids, hydrogels, alginates, foams, hydrofibres, anti-microbial dressings, de-odouriser dressings and collagen dressings. The choice of dressing depends on a proper assessment of the wound (presence of ischaemia, infection, etc.) and matching the properties of the various dressings available to best meet the individual needs of that particular wound.

The intervertebral disc is organized with a concentrated proteoglycan solution, the central nucleus pulposus, held within the strong collagen network of the outer annulus fibrosus. The disc exhibits a viscoelastic response when subjected to loads and deformations. Disc degeneration, and/or spondylotic changes that are generally considered to be associated with aging, result in a spinal segment with decreased stiffness. However, in the cervical spine of cerebral palsy patients suffering from athetotic movements of the neck, there is a very early onset of disc degeneration and spondylotic change. Acceleration of disc degeneration has been shown to take place in the spines of animals subjected to excessive extension-flexion of the head and neck. Repetitive torsion of the disc has led to structural regression in in vitro studies using animal spines. Delaminated lamellae and/or disruption of the annulus fibrosus are always recognized in the early stages of the destructive process of the intervertebral disc structure. Disruption of the collagen network may be a result of fatigue failure by repetitive loading, which in turn causes the high tensile stresses in the annulus fibrosus from the development of large hydrostatic pressures within the nucleus pulposus. Loosening of the collagen network may be a key factor leading to the loss of proteoglycans and water, finally inducing the development of disc degeneration. A “degenerated disc” can be induced through pure mechanical fatigue failure of the tissue, as an age-independent degradation of the cartilaginous tissue.

The etiology of most of the degenerative changes in the spine continues to remain obscure. However, several lines of evidence suggest that genetic factors may play an important role in the onset of degenerative changes, in addition to various environmental factors. We have generated transgenic mice expressing mutant αl(IX) collagen in the cartilage matrix. They developed progressive intervertebral disc degeneration with age as well as joint degeneration. Both radiologic and histologic studies indicated that cervical and lumbar disc degeneration was more advanced in the transgenic mice than in control littermates. The initial degenerative changes included shrinkage and replacement of the nucleus pulposus with consolidated fibrous tissue, that resulted in a loss of nuclear-anular demarcation. Partial disruption in the lamellar structure of the anulus fibrosus also occurred at this stage. With age, the disc degeneration progressively advanced and sometimes caused herniation of disc material and mild osteophyte formation. These findings imply that genetic abnormalities of cartilage matrix components, such as type IX collagen, may be responsible for certain degenerative diseases in the spine.

Self-organized nanocomposites of hydroxyapatite (HAp) and collagen were prepared by controlling temperature and pH on the basis of a biomimetic process. Transmission electron microscopic observations indicated that the composites prepared at pH 8-9 and 40°C had the bone-like structure in which the c-axes of HAp nanocrystals aligned along collagen fibers forming bundles of about 20μm in length and 1μm in diameter. The mechanical strength of the composites obtained was dependent on the degree of self-organization: the maximum 3-point bending strength was 39.5±0.88MPa and Young’s modulus 2.50±0.38GPa. When implanted in Wister rats’ craniums and beagles’ bilateral radii, osteoblasts and osteoclasts were induced near the composites after two weeks, and the composites were covered with a newly formed bone after 12 weeks.