elastin and Temporomandibular-Joint-Disorders

The temporomandibular joint (TMJ) disc is a little understood structure that, unfortunately, exhibits a plethora of pathologic disorders. Tissue engineering approaches may be warranted to address TMJ disc pathophysiology, but first a clear understanding of structure-function relationships needs to be developed, especially as they relate to the regenerative potential of the tissue. In this review, we correlate the biochemical content of the TMJ disc to its mechanical behavior and discuss what this correlation infers for tissue engineering studies of the TMJ disc. The disc of the TMJ exhibits a somewhat biconcave shape, being thicker in the anterior and posterior bands and thinner in the intermediate zone. The disc, which is certainly an anisotropic and nonhomogeneous tissue, consists almost entirely of type I collagen with trace amounts of type II and other types. In general, collagen fibers in the intermediate zone appear to run primarily in an anteroposterior direction and in a ringlike fashion around the periphery. Collagen orientation is reflected in higher tensile stiffness and strength in the center anteroposteriorly than mediolaterally and in the anterior and posterior bands than the intermediate zone mediolaterally. Tensile tests have shown the disc is stiffer and stronger in the direction of the collagen fibers. Elastin fibers in general appear along the collagen fibers and most likely function in restoring and retaining disc form after loading. The 2 primary glycosaminoglycans of the disc by far are chondroitin sulfate and dermatan sulfate, although their distribution is not clear. Compression studies are conflicting, but evidence suggests the disc is compressively stiffest in the center. Only a few tissue engineering studies of the TMJ disc have been performed to date. Tissue engineering studies must take advantage of existing information for experimental design and construct validation, and more research is necessary to characterize the disc to create a clearer picture of our goals in tissue engineering the TMJ disc.

Topics: Compressive Strength; Elasticity; Elastin; Fibrillar Collagens; Glycosaminoglycans; Humans; Proteoglycans; Sex Factors; Structure-Activity Relationship; Temporomandibular Joint Disc; Temporomandibular Joint Disorders; Tensile Strength; Tissue Engineering; Viscosity; Water

The aim of this study was to compare and characterize the structural and ultrastructural organization of the temporomandibular joint (TMJ) between two large animal models for use in the development of tissue engineering strategies.. Whole TMJs from sheep and pigs were evaluated with micro-computed tomography (μCT) for morphology and quantitative analyses of bone parameters. Histological examination was performed on the TMJ disc and its attachments to investigate regional distribution of collagen, elastin, and glycosaminoglycans (GAGs).. μCT analyses demonstrate higher bone mineral density (BMD) in the temporal fossa compared to the mandibular condyle in both species, with this variable being significantly higher in sheep than pig. Quantitative morphometry of the trabecular condyle reveals no statistical differences between the species. Histology demonstrates similar structural organization of collagen and elastin between species. Elastin staining was nearly twofold greater in sheep than in the pig disc. Finally, Safranin-O staining for GAGs in the TMJ disc was localized to the intermediate zone in the sheep but was absent from the porcine disc.. Our findings show some important differences in the pig and sheep TMJ μCT variables and histology and composition of the disc and discal attachment. These disparities likely reflect differences in masticatory and TMJ functional loading patterns between the two species and provide insights into large animal models towards human applications.. As with the established pig model, the sheep is a suitable large animal model for TMJ research such as regenerative strategies, with specific considerations for design parameters appropriate for human-analog applications.

Topics: Animals; Collagen; Disease Models, Animal; Elastin; Glycosaminoglycans; Humans; Mandibular Condyle; Sheep; Swine; Temporomandibular Joint; Temporomandibular Joint Disorders; Tissue Engineering; X-Ray Microtomography

Temporomandibular joint dysfunction (TMD) is a collection of clinical symptoms that involve masticatory muscles and the temporomandibular joint (TMJ). Common symptoms include limited jaw motion and joint sound/pain, along with TMJ disc displacement. TMD is frequently associated with synovitis, a chronic inflammation of the synovium. Fibroblast‑like synovial cells have been identified to produce several inflammatory mediators and may have an important role in the progression of TMJ inflammation. Degradation of the extracellular matrix molecule elastin may lead to the release of bioactive peptides. The present study aimed to explore the role of elastin‑derived peptides (EDPs) in human temporomandibular disorders. Therefore, interleukin‑6 (IL‑6) expression in the synovial fluid obtained from patients with TMD correlated significantly with two clinical parameters, specifically TMJ locking and pain/jaw function on a visual analog scale (VAS). To the best of our knowledge, this is the first study to determine that the concentration of EDPs in synovial fluid from patients with TMD may also be significantly correlated with the duration of TMJ locking, the VAS score and IL‑6 expression. In vitro, EDPs act on human TMJ synovial cells to promote upregulation of IL‑6 and the elastin‑degrading enzyme matrix metalloproteinase‑12 (MMP‑12). The upregulation of IL‑6 and MMP‑12 expression by EDPs may be mediated through elastin‑binding proteins (EBP) and a protein kinase A signalling cascade. These findings suggest a model for inflammation in the TMJ where EDPs are generated by harmful mechanical stimuli, induce both a pro‑inflammatory cascade and increase expression of MMP‑12 through activation of the EBP signalling cascade. This may lead to further increases in EDP levels, establishing a positive feedback loop leading to chronic inflammation in the TMJ. Therefore, significantly elevated levels of EDPs and IL‑6 in the synovial fluid of the TMJ may be indicators of the pathological conditions of the joint.

Topics: Adolescent; Adult; Aged; Cytokines; Elastin; Female; Fibroblasts; Humans; Inflammation; Male; Matrix Metalloproteinases; Middle Aged; Pain Measurement; Receptors, Cell Surface; Synovial Fluid; Synovial Membrane; Temporomandibular Joint Disorders; Young Adult

This study investigated histochemically the elastic fibers in human temporomandibular joint (TMJ) discs with varying degrees of tissue degeneration/regeneration to determine whether there are differences that correlate with the histologic findings.. Ten diseased human TMJ discs and 2 control specimens were studied histochemically by staining with Weigert's resorcin-fuchsin after oxidation with peracetic acid. This technique selectively stains elastic, elaunin, (pre-elastic), and oxytalan fibers.. In TMJ discs with an abnormal collagen fiber arrangement, an increased number of oxytalan fibers could be observed, contrary to discs with scar-like tissue transformation in which oxytalan fibers were decreased in number. In discs showing tears and clefts, the oxytalan fibers run perpendicular to the defects, whereas elaunin and elastic fibers were mainly circumferentially arranged. In discs with chondroid metaplasia, elastic, elaunin, and oxytalan fibers were extensively detected.. It is hypothesized that the elastic, elaunin, and oxytalan fibers found in severely damaged discs appear to ensure biomechanical compliance by reinforcing regions devoid of collagen bundles and thus function as shock absorbers of stretch and compression.

Topics: Adult; Collagen; Contractile Proteins; Elastic Tissue; Elastin; Extracellular Matrix Proteins; Female; Histocytochemistry; Humans; Male; Microfibrils; Middle Aged; Muscle Fibers, Skeletal; Temporomandibular Joint Disc; Temporomandibular Joint Disorders

Specialized roles for the different components of the retrodiscal tissues have been previously postulated. This study compared the histologic features of the retrodiscal tissues of temporomandibular joints, taken from human cadavers, in the open and closed position; it was concluded that the primary role of these components was to provide a volumetric compensatory mechanism for pressure equilibration. This mechanism was still active in joints that demonstrated disc displacement and degenerative changes. Elastin was found in the upper and lower strata of the retrodiscal tissues, as well as in the central zone. The concept of an elastic upper stratum that has a recoil mechanism to control disc movement was not supported by this study, as the upper stratum was folded on itself in the closed position and only became stretched near maximal opening.

Topics: Aged; Aged, 80 and over; Cartilage, Articular; Elastic Tissue; Elastin; Humans; Joint Capsule; Joint Dislocations; Mandibular Condyle; Middle Aged; Osteoarthritis; Temporomandibular Joint; Temporomandibular Joint Disorders

Joint pain has been associated with fatty infiltration of the knee articulation. The purpose of this study is to report on the histopathological findings, especially fatty changes, that are seen in surgical specimens from the temporomandibular joints (TMJ) of patients that had persistent pain after non-surgical therapy. Forty plicated TMJ retrodiscal samples from 25 patients were used in this study. The patients were previously treated with splints for variable periods but not less than 2 months. The specimens were obtained by 2 surgeons using standard TMJ plication techniques. Control disc specimens were obtained from normal appearing cadaveric TM joints. Samples were immediately immersed in glutaraldehyde and processed for light and electron microscopic examination. The specimens were composed mainly of moderately dense tissue with cells that appeared fibroblastic and intermittent chondrocytic type cells. Fatty change, exclusively in association with the perivascular areas, was observed in 27 of 40 specimens. Electron microscopy showed fibroblasts, as well as large fat inclusions adjacent to elastin macroglobules. Fatty infiltration of the TMJ has been interpreted as a degenerative change. It is postulated that kinins and prostaglandins generated in the fat pads can pass freely in tissue fluid to adjacent, highly innervated structures thus leading to joint pain. It is further postulated that the finding of associated elastin with fatty deposition is similar to the atherosclerotic changes encountered in large blood vessels and the aorta.

Topics: Adipose Tissue; Adolescent; Adult; Collagen; Elastin; Female; Fibroblasts; Humans; Joint Dislocations; Male; Microscopy, Electron; Synovial Membrane; Temporomandibular Joint Disorders