Scanning electoronmicroscopical analysis of the loose bodies of synovial chondoromatosis in temporomandibular joint.

The aim of this study is to reveal the morphological property about the loose bodies (LBs) of temporomandibular joint (TMJ) by scanning electron microscope (SEM). We obtained specimens from two female cases of released loose body by surgical operation. These specimens were fixed by soaking in a mixture of 5% glutaraldehyde or 4% formaldehyde for one week. They were cut into half pieces. These specimens were observed at an accelerating voltage of 3 kV under a SEM (JSM-5500, JEOL, Tokyo). In the electron microscopic findings, it seems to be separated into two different parts as inside part and outside part. On the inside part, collagen fibers were running very densely in the same direction in an orderly neatly manner. Whereas, we observed waved collagen fibers running irregularly with many spaces on the outside part. Outside part seems to be porous pattern compared with inside part. It might be that the surface and outside part included many active fibroblasts. As results, it seems that the LBs might develop in a multi-layer style, in which fibrous tissues were piled up loosely around the inside part. The proliferating activity of LBs grows from the inside to outside of SC in TMJ.

Angioarchitecture and morphology of temporomandibular joint of Monodelphis domestica.

The opossum Monodelphis domestica presents movement of the temporomandibular joint (TMJ) reflecting adaptation to eating habits similar to movement in humans, but the structure of the TMJ is not yet known. Thus, nine young M. domestica, of both sexes were weighed, anesthetized with xylazine (10 mg kg(-1) ), and ketamine (70 mg kg(-1) ) and processed for: 1. The analyses of the macroscopic angioarchitecture after latex injection, as well as the topography of the TMJ; 2. The analysis of microvascularization after injection of Mercox resin and corrosion of soft tissue with NaOH using scanning electron microscopy and; 3. The histological evaluation of the TMJ with an optical microscope. Macroscopic analysis of the latex injected vessels revealed the distribution of the arteries from the common carotid artery, receiving branches of the superficial temporal and maxillary arteries. The mandibular condyle has the long axis in the lateral-lateral direction, and is convex in the anterior-posterior direction. Its topography was determined in relation to the eye and external acoustic meatus. With scanning electron microscopy, microvascularization consists of arterioles of varying diameter (85-15 µm) of the meandering capillary network in the retrodiscal region, and a network of straight capillaries in the TMJ anterior region. Via light microscopy the TMJ has similar histological features to those of humans. These macroscopic, microscopic and ultrastructural data from TMJ of the M. domestica could be a suitable model for TMJ physiology and pathophysiology studies for then speculate on possible human studies. Microsc. Res. Tech. 79:806-813, 2016. © 2016 Wiley Periodicals, Inc.

Unilateral anterior crossbite induces aberrant mineral deposition in degenerative temporomandibular cartilage in rats.

OBJECTIVE: To investigate whether mechanical stress induces mineral deposits that contribute to matrix degradation at the onset of osteoarthritis (OA) in temporomandibular joint (TMJ) cartilage. DESIGN: Female Spraguee-Dawley rats were subjected to an unilateral anterior crossbite (UAC) procedure. Histology, electron microscopy, and energy dispersive spectrometer (EDS) were used to examine cartilage matrix structures and composition of mineral deposit in the affected TMJ cartilage. Protein and/or RNA expression of phenotypic markers and mineralization modulators and matrix degradation was analyzed by immunohistochemistry and/or real-time PCR. Synthetic basic calcium phosphate (BCP) and calcium pyrophosphate dehydrate (CPPD) crystals were used to stimulate ATDC5 cells for their impact on cell differentiation and gene expression. RESULTS: Fragmented and disorganized collagen fibers, expanded fibrous spaces, and enhancement of matrix vesicle production and mineral deposition were observed in matrices surrounding hypertrophic chondrocytes in cartilage as early as 2-weeks post-UAC and exacerbated with time. The mineral deposits in TMJ cartilage at 12- and 20-weeks post-UAC had Ca/P ratios of 1.42 and 1.44, which are similar to the ratios for BCP. The expression of mineralization inhibitors, NPP1, ANK, CD73, and Matrix gla protein (MGP) was decreased from 2 to 8 weeks post-UAC, so were the chondrogenic markers, Col-2, Col-X and aggrecan. In contrast, the expression of tissue-nonspecific alkaline phosphatase (TNAP) and MMP13 was increased 4-weeks post-UAC. Treating ADTC5 cells with BCP crystals increased MMPs and ADAMTS5 expression, but reduced matrix production in a time-dependent manner. CONCLUSION: UAC induces deposition of BCP-like minerals in osteoarthritic cartilage, which can stimulate matrix degradation by promoting the expression of cartilage-degrading enzymes to facilitate OA progression.

Morphological characteristics of the temporomandibular joint in the pouch young of the Tasmanian devil.

We recently reported the absence of the articular disc, which is a constant structure in mammals, in the temporomandibular joint of the adult Tasmanian devil. However, whether the articular disc disappears with growth of the animal was unknown. The aim of this study was to determine whether a pouch young of the Tasmanian devil has the articular disc. The temporomandibular joint of a fresh carcass of the pouch young, whose crown-rump length was 43 mm, was examined microscopically and by microcomputed tomography. The absence of the articular disc in the pouch young temporomandibular joint was histologically confirmed. It is suggested that the articular disc of the Tasmanian devil is naturally absent.

Effects of chronic sleep deprivation on the extracellular signal-regulated kinase pathway in the temporomandibular joint of rats.

OBJECTIVES: To examine the possible involvement and regulatory mechanisms of extracellular signal-regulated kinase (ERK) pathway in the temporomandibular joint (TMJ) of rats subjected to chronic sleep deprivation (CSD). METHODS: Rats were subjected to CSD using the modified multiple platform method (MMPM). The serum levels of corticosterone (CORT) and adrenocorticotropic hormone (ACTH) were tested and histomorphology and ultrastructure of the TMJ were observed. The ERK and phospho-ERK (p-ERK) expression levels were detected by Western blot analysis, and the MMP-1, MMP-3, and MMP-13 expression levels were detected by real-time quantitative polymerase chain reaction (PCR) and Western blotting. RESULTS: The elevated serum CORT and ACTH levels confirmed that the rats were under CSD stress. Hematoxylin and eosin (HE) staining and scanning electron microscopy (SEM) showed pathological alterations in the TMJ following CSD; furthermore, the p-ERK was activated and the mRNA and protein expression levels of MMP-1, MMP-3, and MMP-13 were upregulated after CSD. In the rats administered with the selective ERK inhibitor U0126, decreased tissue destruction was observed. Phospho-ERK activation was visibly blocked and the MMP-1, MMP-3, and MMP-13 mRNA and protein levels were lower than the corresponding levels in the CSD without U0126 group. CONCLUSION: These findings indicate that CSD activates the ERK pathway and upregulates the MMP-1, MMP-3, and MMP-13 mRNA and protein levels in the TMJ of rats. Thus, CSD induces ERK pathway activation and causes pathological alterations in the TMJ. ERK may be associated with TMJ destruction by promoting the expression of MMPs.

Progression of cartilage degradation, bone resorption and pain in rat temporomandibular joint osteoarthritis induced by injection of iodoacetate.

BACKGROUND: Osteoarthritis (OA) is an important subtype of temporomandibular disorders. A simple and reproducible animal model that mimics the histopathologic changes, both in the cartilage and subchondral bone, and clinical symptoms of temporomandibular joint osteoarthritis (TMJOA) would help in our understanding of its process and underlying mechanism. OBJECTIVE: To explore whether injection of monosodium iodoacetate (MIA) into the upper compartment of rat TMJ could induce OA-like lesions. METHODS: Female rats were injected with varied doses of MIA into the upper compartment and observed for up to 12 weeks. Histologic, radiographic, behavioral, and molecular changes in the TMJ were evaluated by light and electron microscopy, MicroCT scanning, head withdrawal threshold test, real-time PCR, immunohistochemistry, and TUNEL assay. RESULTS: The intermediate zone of the disc loosened by 1 day post-MIA injection and thinned thereafter. Injection of an MIA dose of 0.5 mg or higher induced typical OA-like lesions in the TMJ within 4 weeks. Condylar destruction presented in a time-dependent manner, including chondrocyte apoptosis in the early stages, subsequent cartilage matrix disorganization and subchondral bone erosion, fibrosis, subchondral bone sclerosis, and osteophyte formation in the late stages. Nociceptive responses increased in the early stages, corresponding to severe synovitis. Furthermore, chondrocyte apoptosis and an imbalance between anabolism and catabolism of cartilage and subchondral bone might account for the condylar destruction. CONCLUSIONS: Multi-level data demonstrated a reliable and convenient rat model of TMJOA could be induced by MIA injection into the upper compartment. The model might facilitate TMJOA related researches.

The influence of psychological stress on the rat temporomandibular joint with the application of countermeasures.

OBJECTIVE: This study aimed to provide an experimental theoretical basis for the treatment of temporomandibular disorders by observing the effects of psychological stress and countermeasures on the rat temporomandibular joint (TMJ). METHODS: Rats were exposed to psychological stress via a communication box and the lateral pterygoid muscle and TMJ were observed with transmission electron microscopy and scanning electron microscopy. Furthermore, the expression of interleukin-1 and tumor necrosis factor-α was assessed in control animals and psychological stress (PS) and stress with diazepam (PS+DI) groups. RESULTS: Transmission electron microscopy of the lateral pterygoid muscle fibers in the PS showed vacuolar changes in the mitochondria, loss of cristae, and reduced matrix density to variable degrees after 1, 3, and 5 wk of stress. After 5 wk stress+recovery, the cristae and matrix were normal in the PS and PS+DI groups. Scanning electron microscopy of PS rats showed some synovial membranes were detached from the surface of the articular disc after 1 wk. After 3 wk, collagen fibers appeared to have wider waves and worn strips changing in size on the articular disc; after 5 wk, the distribution of collagen fibers was distorted. In PS+recovery and PS+DI rats, no obvious changes were observed on the surface of the articular disc after 1 to 5 wk stress. In PS rats, interleukin-1 and tumor necrosis factor-α expression increased significantly but was at control levels in the PS+DI and PS+recovery groups. CONCLUSION: Counteracting psychological stress can antagonize its effects on the TMJ and provide a reference for the treatment of stress-related temporomandibular disorders.

Qualitative study of young, adult, and aged Wistar rats temporomandibular synovial membrane employing light, scanning, and transmission electron microscopy.

The aim of this study was to analyze the rat temporomandibular joint (TMJ) synovial membrane at different ages using light, scanning, and transmission electron microscopy. Under light microscopic analysis, the TMJ structures were observed such as condyle, capsule, disk, the synovial membrane collagen type, and cells distribution. In the scanning electron microscopy, the synovial membrane surface exhibited a smooth aspect in young animals and there was an increase with ageing in the number of folds. The transmission electron microscopic analysis showed more synoviocytes in the synovial layer in the young group and still a great number of vesicles and cisterns dilation of rough endoplasmic reticulum in the aged group. In the three groups, a dense layer of collagen fibers in the synovial layer and cytoplasmic extensions were clearly seen. It was possible to conclude that synovial membrane structures in aged group showed alterations contributing to the decrease in joint lubrication and in the sliding between disk and joint surfaces. These characteristic will reflect in biomechanics of chewing, and may cause the TMJ disorders, currently observed in clinical processes.

Psychological stress induces alterations in temporomandibular joint ultrastructure in a rat model of temporomandibular disorder.

OBJECTIVE: The objective of this study was to investigate the effects of psychological stress on temporomandibular disorder (TMD). STUDY DESIGN: A communication box was used to induce psychological stress (PS) in rats. Then, the ultrastructure of temporomandibular was observed using scanning electron microscopy. Interleukin-1 (IL-1) and IL-6 were measured with reverse transcription polymerase chain reaction. RESULTS: The PS group showed evidence of ultrastructural changes in the condyle and articular disk after stimulation, i.e., incomplete gelatinlike material was observed on the condyle after 1 week of PS, wider waves on the articular disk and exposed condylar collagen were observed after 3 weeks of PS, and cracks were apparent on the surface of the condyle. The expression of IL-1 and IL-6 in the condyle cartilage significantly increased after exposure to psychological stress. CONCLUSIONS: These results indicate that psychological stress induces ultrastructure alterations in the temporomandibular joint and plays an important role in TMD.

[Changes of the ultrastructures of temporomandibular joint after removal of emotional stress factors in rats].

OBJECTIVE: To examine the changes of the ultrastructures of temporomandibular joint after removal of the emotional stress factors in rats. METHODS: Thirty-two 12-week-old male Wistar rats were divided into two groups randomly, experimental group and control group. Each group was divided into two subgroups according to execution time, 9-week subgroup and 12-week subgroup with eight rats in each subgroup. Chronic unpredictable stress animal model were firstly established in experimental group in the first 6 weeks, then all the stimulation factors removed and breed normally. After 9 weeks, rats in 9-week subgroup were killed. After 12 weeks, rats in 12-week subgroup were killed. All condyles and articular discs were dissected and observed by scanning electron microscope. RESULTS: There was some recovery in condyles and articular discs in experimental group under scanning electron microscope. The gelatum on the surface of condyles increased, collagen fibrils became regular and deep layer collagen fibrils less exposed. There were no such obvious changes on the surface of condyles and articular discs in control group. CONCLUSIONS: The ultrastructure injures of temporomandibular joint in rats induced by emotional stress could be reversed if the stress factors were removed.

Morphological changes in the mandible of male mice associated with aging and biomechanical stimulus.

Degenerative changes in the temporomandibular joint (TMJ) associated with aging can affect mandibular shape and reduce growth potential when stimulated by functional appliance therapy. This study was designed to evaluate the morphological changes in the mandibles of male mice associated with aging and biomechanical stimulus. Every 3 days over the course of 1 month, the lower incisors were trimmed by 1 mm to induce mandibular advancement (MA) when the animal was feeding. The left mandibles of the 23 experimental and 27 control animals were subsequently dissected, and digital images were obtained to analyze nine linear/angular measurements. Because mandibular morphology depends on the maintenance of condylar cartilage, the surfaces of the condylar cartilage and the ascending ramus of the mandible were also analyzed by scanning electron microscopy (SEM). The linear measurements of the mandible showed changes according to age in the control group and a growth response in the mandibular condyle in 7- and 15-month-old mice after MA. Moreover, SEM analysis revealed depressions in the anterior region of the condylar cartilage and inclined vascular grooves in the ascending ramus in the 7- and 15-month-old experimental mice. Although the growth potential is reduced in mice after 6 months of age, the results showed that continuous growth of the mandible occurs after maturation, except in the condyle, and that biomechanical stimulus of the TMJ of male mice leads to condylar growth. These results suggest that mature and old individuals can favorably respond to maxillary functional orthopedic therapy.

Masseter muscle inserted in the temporomandibular joint discocapsular complex, a case report

The presence of muscle insertions in the temporomandibular joint disc have a great importance in the dynamic joint. This article presents a case of bilateral insertion of deep fascicle of the masseter muscle in the temporomandibular joint capsule and disc in a spain corpse, describes the microscopic and macroscopic appearance of variation and a brief review of the functional implications.

La presencia de inserciones musculares en el disco de la articulación temporomandibular tiene gran importancia en la dinámica de la articulación. En este artículo se presenta un caso de la inserción bilateral del fascículo profundo del músculo masétero en la cápsula y disco de la articulación temporomandibular en un cadáver español, se describe el aspecto macroscópico y microscópico de la variación y se realiza una breve revisión de las implicancias funcionales.

[Influence of chronic unpredictable emotional stress on the ultrastructures of temporomandibular joint in rats].

OBJECTIVE: To study the influence of emotional stress on the ultrastructures of temporomandibular joint in rats. METHODS: Sixteen male Wistar rats, aged 12 weeks, were divided into 2 groups randomly, experimental group and control group. Animal model of chronic unpredictable stress was established in the experimental group. After 6 weeks, all rats in both groups were killed and their condyles and articular discs were dissected, taken out and observed by scanning electron microscope. RESULTS: Under scanning electron microscope, the surface gelatum of the condyles in experimental group were cracked, and collagen fibrils in disorder and broke, and deep layer collagen fibrils were exposed. The articular discs' surface gelatum were still integrated, but the gyri dispose were irregular. In control group, there were no such changes in condyles and articular discs. CONCLUSIONS: The long-term emotional chronic unpredictable stress could induce the injuries of temporomandibular joint in rats in ultrastructure level.

Biomechanical properties of the condyle created by osteodistraction.

A new condyle can be reconstructed by osteodistraction, but the biomechanical properties of the neocondyle remain unknown. This study examined the hypothesis that the biomechanical properties of neocondylar cancellous bone could reach control levels 24 weeks after its creation by osteodistraction. The right mandibular condyles were removed and reconstructed by osteo-distraction in 16 adult goats. Their contralateral condyles served as controls. Microstructural and mechanical properties were examined by microcomputed tomography and mechanical testing. At 24 weeks after distraction, the neocondyle grew larger in size, but the shape and histological features were similar to those of the controls. The cancellous bone of the neocondyle even appeared to be more dense and stiffer in comparison with the control condyle. The results of this study suggest that the neocondyle created by osteodistraction develops nearly normal biomechanical properties for functional loading by 24 weeks after creation.

Immunocytochemical localization of caveolin-3 in the synoviocytes of the rat temporomandibular joint during development.

Caveolins -- caveolin-1, -2, -3 (Cav1, 2, 3) -- are major components of caveolae, which have diverse functions. Our recent study on the temporomandibular joint (TMJ) revealed expressions of Cav1 and muscle-specific Cav3 in some synovial fibroblast-like type B cells with well-developed caveolae. However, the involvement of Cav3 expression in the differentiation and maturation of type B cells remains unclear. The present study therefore examined the chronological alterations in the localization of Cav3 in the synovial lining cells of the rat TMJ during postnatal development by immunocytochemical techniques. Observations showed immature type B cells possessed a few caveolae with Cav1 but lacked Cav3 protein at postnatal day 5 (P5). At P14, Cav3-immunopositive type B cells first appeared in the synovial lining layer. They increased in number and immunointensity from P14 to P21 as occlusion became active. In immunoelectron microscopy and double immunolabeling with heat shock protein 25 (Hsp25) and Cav3, coexpressed type B cells developed rough endoplasmic reticulum and numerous caveolae, while the Cav3-immunonegative type B cell with Hsp25 immunoreaction possessed few of these. Results suggest that Cav3 expression, which is closely related to added functional stimuli, reflects the differentiation of the type B synoviocytes.

Matrix metalloproteinase and its inhibitor in temporomandibular joint osteoarthrosis after indirect trauma in young goats.

Our aim was to examine the change in expression of matrix metalloproteinases (MMP-13), matrix metalloproteinases-3 (MMP-3), and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in the articular cartilage of goats with experimentally-induced osteoarthrosis of the temporomandibular joint (TMJ) at various times. Osteoarthrosis was induced in 20 goats in the bilateral TMJ and 5 goats acted as controls. There were 5 goats in each group, and a group was killed at 7 days, and 1, 3, and 6 months postoperatively. The samples were collected, and the joints evaluated histologically. Immunofluorescence was used to detect the presence of MMPs and TIMP-1 in the articular disc and condylar cartilage. The ultrastructure of the articular disc and condylar surface at 1 month was examined with scanning electron microscopy (SEM). Osteoarthrosis of the TMJ progressed gradually over time. MMP-13, MMP-3, and TIMP-1 were expressed strongly in the TMJ soon after injury; MMP-13 became gradually weakened, and MMP-3 strengthened later. None of these were expressed in the normal condyle. After a month the surface of the arthrotic condyle was uneven, and the underlying collagen fibrils were exposed in irregular fissures on the surface. The secretion of TIMP-1 was related closely to the changes of MMPs during osteoarthrosis of the TMJ. The unbalanced ratio between them caused degradation of the matrix of the cartilage and might be the cause of osteoarthrosis of the TMJ.

Age-related changes in the microarchitecture of collagen fibrils in the articular disc of the rat temporomandibular joint.

The microarchitecture of collagen fibrils in the articular disc of the temporomandibular joint (TMJ) plays an important role in dissipating the mechanical load during jaw movement. However, little information is available on its adaptations to the biomechanical environment during development. To address this issue, we analyzed the diameter of collagen fibrils of the articular disc of the rat TMJ with quantitative ultrastructural analysis during postnatal development. The mean diameter of the collagen fibrils significantly increased and the arrangement of the collagen fiber networks became compact during development. Articular discs of suckling rat pups were composed of thin, uniformly sized collagen fibrils (range: 30-60 nm, peak: 40-50 nm). At the age of 4 weeks, thicker collagen fibrils began to appear in articular discs, shortly after weaning (range: 20-70 nm, peak: 40-50 nm). In articular discs of adult rats, collagen fibrils varied widely in diameter, with thick fibrils predominating (range: 10-120 nm, peak: 40-70 nm). These age-related changes in the microarchitecture of collagen fibrils in articular discs may reflect changes in their biomechanical environment during development.

Ultrastructural study of the temporomandibular joint after unilateral meniscectomy in Wistar rats.

Meniscectomy of the temporomandibular joint (TMJ) was frequently performed until a few years ago but now is seldom employed. This procedure induces important articular modifications but the complete extent of ultrastructural changes is still unknown. Twenty-one Wistar rats were submitted to unilateral meniscectomy. Animals were randomly divided into three groups and followed for 15, 35 or 60 days. After killing both meniscectomized and contralateral TMJ specimens were sectioned sagittally and prepared for light and scanning electron microscopy studies. Normal TMJs are characterized by glenoid fossa and condylar process with distinct conjunctive layers in which regularly arranged type 1 collagen fibres predominate. Meniscectomized animals initially exhibit a different tissue covering the eroded articular surface of the condyle with the prevalence of type 3 collagen fibres but type 1 fibres predominate in the late postoperative period. Subchondral cysts are clearly visible. A complex remodelling process of the TMJ after meniscectomy is evident with important ultrastructural modifications that may correlate to unsatisfactory clinical results. The dynamic nature of this process is also observed when specimens from different postoperative periods are compared. Surgeons should always bear in mind these alterations when indicating this procedure.

[The post-injury regenerating ability of temporomandibular joint of rats exposed to the repeated + Gz forces].

OBJECTIVE: To observe the post-injury regenerating ability of temporomandibular joint of rats exposed to the repeated + Gz forces. METHODS: One hundred and eight male rats were randomly assigned to 9 groups, with 12 rats in each group. Group A was normally fed serving as the blank control group. Group B was only fixed with rat-kept devices for 5 minutes as the fixed control group. Group C was borne +1 Gz for 5 minutes. In the same position as group C, group D, E, F, G, H and I were repeatedly exposed to +10 Gz for 30 seconds each time with 5 times a day and +1 Gz for 1 minutes as a interval. The 6 groups were treated in the condition above for 4 days a week and 4 weeks in total. The rats in group A, B, C and D were killed on the next day after the centrifuge. The rats in group E, F, G, H and I were killed at 1, 2, 4, 8 and 12 weeks after the centrifuge, respectively. After the rats were killed, temporomandibular joint were taken for observation under optical microscope, scanning electron-microscope (SEM) and transmission electron-microscope (TEM). RESULTS: There was no significant difference observed in group A, B and C. But in group D, E, F, G, H and I pathologic injuries and self-regeneration were seen in TMJ in different degrees. CONCLUSIONS: The injury of TMJ could regenerate gradually with time.

Avaliação ultra-sonográfica dos distúrbios intra-capsulares têmporo-mandibulares / Ultrasonography evaluation of the temporomandibular joint internal derangements

Com o intuito de avaliar a sensibilidade e a especificidade do exame ultra-sonográfico para a avaliação dos distúrbios da articulação têmporo-mandibular (ATM) estudamos um grupo controle de 10 pacientes hígidos e 38 pacientes com queixas articulares e comparamos os resultados obtidos com a ressonância magnética, padrão ouro para o estudo da ATM. O trabalho evidenciou alta sensibilidade e especificidade para a localização do disco articular com o paciente em repouso, não apresentando bons resultados para a análise de alterações morfológicas condilares e do disco articular, e embora o método ainda apresente limitações, a sua utilização pode vir a ser uma opção útil ao exame de RM / Aiming at evaluating the sensibility and specificity of the ultrasound examination for the study of the disturbances of the temporomandibular joint (TMJ) we have studied a control group of 10 healthy patients and 38 other patients with articular complaints and we have compared the results obtained with the magnetic resonance, gold standard for the study of the TMJ. The work has shown high sensibility and specificity for the location of the articular disk with the patient at rest, not presenting good results for the analysis ofarticular disk and condyle morphologic alterations and, although it still presents some limitation, the method may turn out to be a helpful option to the MR exam...