Rabbit Temporomandibular Joint Research Articles

Insulin-like growth factor-1 suspended in hyaluronan improves cartilage and subchondral cancellous bone repair in osteoarthritis of temporomandibular joint

This study sought to evaluate the effects of intra-articular injection of insulin-like growth factor-1 (IGF-1) suspended in hyaluronan (HA) on the cartilage and subchondral cancellous bone repair in osteoarthritis (OA) of the temporomandibular joint (TMJ). Disc perforation was performed bilaterally in rabbit TMJs to induce OA. Four groups of animals (n=12) received OA induction only, and either intra-articular HA injection alone, intra-articular IGF-1 injection alone, or a combination of HA and IGF-1 injection. All therapy was begun 4 weeks after OA induction. The animals were killed 12 or 24 weeks after the first injection, for histology and micro-CT examinations. Two additional animals were used as normal controls. Typical cartilage and subchondral cancellous bone lesions were observed in the OA group. No protective effect on cartilage and subchondral cancellous bone was found in the HA or IGF-1 alone groups. Better histological repair and nearly normal micro-architectural properties of the subchondral cancellous bone were observed in the HA+IGF-1 group compared with the HA or IGF-1 alone groups. HA may be used as an effective carrier for intra-articular injection of IGF-1 and the combination of HA/IGF-1 shows promise as a new rational approach to therapy of TMJ OA.

Temporomandibular joint disc tissue engineering of synovial fibroblast-like cells cultured in the chitosan/collagen I scaffolds

Objective To evaluate the potential of synovial fibroblast-like cells (SFBs) cultured in the chitosan/collagen I ( CS/COL- I ) scaffold for the tissue engineering of temporomandibular joint (TMJ) disc. Methods CS/COL-I copolymers were synthesized by the freeze-drying method. The morphological characteristics were evaluated under the scanning electronic microscopy. Synovium was harvested from rabbit TMJs. The third to fifth passage SFBs were cultured onto the CS/COL- I copolymers. MTT assay was employed to evaluate the proliferation and viability of SFBs cultured on the CS/COL- I at the day 1,3,5,7.After being induced by the cocktail application of recombinant human transforming growth factor β1(rhTGF-Bl, 10 μg/L) and basic fibroblast growth factor (bFGF, 50 μg/L) in vitro, SFBs/CS-COL- I constructs were transplanted into nude mice to evaluate the chondrogenic formation through histo-logical and immulohistochemical staining and reverse transcription polymerase chain reaction (PCR) at the week 4 and 8.Results The synthesized CS/COL-1 scaffold was spongy-like structure with a bulk of pores. MTT results showed that the scaffolds could improve SFBs proliferation (P < 0.05). Immulohisto-chemically and histologically, semi-quantitative analysis of the implants revealed that the contents of GAGs and collagen type Ⅲat the week 8 after transplantation were (6.900 ±0.316) and (0.0952 ±0.0248) IA/μm2 respectively and at the week 4 (3.600 ± 0.699 ) and (0.0411 ±0.0127) IA/μm2 respectively. Conclusion It is suggested that the SFBs/CS-COL- I constructs could be a candidate for TMJ disc tissue engineering. Key words: Chitosan; Synovial cell; Temporomandibular joint disc; Tissue engineering

Role of Wnt‐5A in interleukin‐1β–induced matrix metalloproteinase expression in rabbit temporomandibular joint condylar chondrocytes

To determine the possible involvement and regulatory mechanisms of Wnt-5A signaling in interleukin-1beta (IL-1beta)-induced increase in matrix metalloproteinase 1 (MMP-1), MMP-3, MMP-9, and MMP-13 expression in temporomandibular joint (TMJ) condylar chondrocytes. Primary rabbit condylar chondrocytes were treated with IL-1beta, purified Wnt-5A protein, or both and transfected with Wnt-5A expression vector. Expression of Wnt-5A, MMP-1, MMP-3, MMP-9, MMP-13, and type II collagen, as well as cell morphologic changes, were examined. To explore the mechanisms of action of Wnt-5A, the accumulation and nuclear translocation of beta-catenin, the transcription activity of the beta-catenin-Tcf/Lef complex, phosphorylated JNK, phosphorylated ERK, and phosphorylated p38 were analyzed. SP600125, a JNK inhibitor, was used to investigate the role of the JNK pathway in Wnt-5A induction of MMP-1, MMP-3, MMP-9, and MMP-13. Treatment of rabbit condylar chondrocytes with IL-1beta up-regulated Wnt-5A expression. Purified Wnt-5A protein and transfection with Wnt-5A expression vector promoted the expression of MMP-1, MMP-3, MMP-9, and MMP-13. Wnt-5A did not cause accumulation and nuclear translocation of beta-catenin or activation of the beta-catenin-Tcf/Lef transcription complex. Instead, Wnt-5A activated JNK, and an inhibitor of JNK blocked the Wnt-5A-induced up-regulated expression of MMPs. These findings indicate that IL-1beta up-regulates Wnt-5A, and the activation of Wnt-5A signaling induces the expression of MMP-1, MMP-3, MMP-9, and MMP-13 via the JNK signaling pathway in rabbit TMJ condylar chondrocytes. Blockage of JNK signaling impairs the Wnt-5A-induced up-regulation of MMPs. Thus, Wnt-5A may be associated with cartilage destruction by promoting the expression of MMPs.

Morphometric and ultrastructural studies of the effect of infrared laser on rabbit temporo-mandibular joint fibroblasts

The infrared laser beams has been successfully used in joint lesions treatment due to its analgesic anti inflamatory and healing action, and on a cellular level, inducing an accentuated synthesis of ATP, activating cellular proliferation and collagen synthesis. Samples of normal-control and irradiated tissue from temporo-mandibular joint disc of rabbit, were obtained, with daily doses of 2 joules/cm²during 10 consecutive days. They were prepared for transmission electronic microscopy.Transmission electronic micrographs of normal and irradiated fibroblasts were obtained with final increase of 11.500 X for morphometric studies with the purpose of quantifying the volumetric fractions of the cellular components pertaining to the mentioned cellular types. Volumetric fractions of the quoted cell corresponding to nucleus, cytoplasm, rough endoplasmatic reticule, eu and heterochromatin were evaluated. In the same manner, the nucleus - cytoplasmatic relation and the area of each cellular type were quantified. The results derived from the morphometric comparative study between the normal and irradiated fibroblasts indicated that there were significant differences with respect to the volumetric fractions of euchromatin and heterochromatin and fundamentally in the cellular areas of both types. On the other hand, the rest of quantified parameters remained constant. It could be concluded that the cellular function reflected in collagen synthesis and secretion remained constant in both cellular types. However, by means of infrared laser stimulations, this fibroblast facilitated protein synthesis, due to high percentage of transcriptionally active euchromatine.

Intra-articular vs. systemic administration of etanercept in antigen-induced arthritis in the temporomandibular joint. Part II: mandibular growth

BackgroundTemporomandibular joint (TMJ) arthritis in children causes alterations in the craniomandibular growth. Resultant abnormalities include; condylar erosions, a posterior mandibular rotation pattern, micrognathia, malocclusion with an anterior open bite, altered joint and muscular function occasionally associated with pain. These alterations may be prevented by early aggressive anti-inflammatory intervention. Previously, we have shown that intra-articular (IA) corticosteroid reduces TMJ inflammation but causes additional mandibular growth inhibition in young rabbits. Local blockage of TNF-α may be an alternative treatment approach against TMJ involvement in juvenile idiopathic arthritis (JIA). We evaluated the anti-inflammatory effect of IA etanercept compared to subcutaneous etanercept in antigen-induced TMJ-arthritis in young rabbits in terms of mandibular growth. This article (Part II) presents the data and discussion on the effects on facial growth. In Part I the anti-inflammatory effects of systemic and IA etanercept administration are discussed.MethodsArthritis was induced and maintained in the TMJs of 10-week old pre-sensitized rabbits (n = 42) by four repeated IA TMJ injections with ovalbumin, over a 12-week period. One group was treated weekly with systemic etanercept (0.8 mg/kg) (n = 14), another group (n = 14) received IA etanercept (0.1 mg/kg) bilaterally one week after induction of arthritis and one group (n = 14) served as an untreated arthritis group receiving IA TMJ saline injections. Head computerized tomographic scans were done before arthritis was induced and at the end of the study. Three small tantalum implants were inserted into the mandible, serving as stable landmarks for the super-impositions. Nineteen variables were evaluated in a mandibular growth analysis for inter-group differences. All data was evaluated blindedly. ANOVA and T-tests were applied for statistical evaluation using p < 0.05 as significance level.ResultsSignificant larger mandibular growth disturbances were observed in the group receiving IA saline injections compared with the systemic etanercept group. The most pronounced unfavourable posterior mandibular rotation pattern was observed in the group receiving IA saline injections.ConclusionIntervention with systemic etanercept monotherapy equivalent to the recommended human dose allows a mandibular growth towards an original morphology in experimental TMJ arthritis. Systemic administrations of etanercept are superior to IA TMJ administration of etanercept in maintaining mandibular vertical growth.

Regeneration of articular cartilage defects in the temporomandibular joint of rabbits by fibroblast growth factor-2: a pilot study

The purpose of this study was to investigate the therapeutic usefulness of fibroblast growth factor-2 (FGF-2) in rabbit temporomandibular joints (TMJ) with osteoarthritis. A 10-mm 3 defect was bored in the surface of the mandibular condyle head. The animals were divided into four groups: two test groups in which the defect was filled with lyophilized collagen containing 0.1 or 1.0 μg of FGF-2, and two control groups, in which the defects were filled with lyophilized collagen without FGF-2 or left empty. The defective sites were examined under a light microscope 3 weeks after surgery. Initiation of cartilage formation was observed in the defects filled with 0.1 μg of FGF-2, but only a small amount of cartilage was found in the defects of the 1.0-μg FGF-2- treated group. In the control groups, soft-tissue repair only or no tissue repair was found. In vivo, a dose of 0.1 μg of FGF-2 can stimulate articular cartilage restoration in defects of the TMJ in rabbits, although determining the effective concentration range of FGF-2 may be difficult. The present results suggest that an optimum concentration of FGF-2 could restore defects of TMJ articular cartilage clinically.

Poster 243: Histopathological Influence of Anti-TNF-Alpha Therapy on Antigen-Induced Arthritis Model of the Rabbit Temporomandibular Joint

Tumor necrosis factor-alpha (TNF-alpha) is closely associated with inflammatory changes and modulates apoptosis in condylar cartilage of temporomandibular joint (TMJ) arthritis. The aims are to investigate the effect of intra-articular injection of anti-TNF-alpha antibody on antigen-induced arthritis model of the rabbit temporomandibular joint histopathologically. Bilateral TMJ arthritis were induced in 9 adult New Zealand White rabbits. Ten Mol/kg anti-TNF-alpha antibody in 0.2ml saline was injected in the unilateral TMJ at day 0 after induction of arthritis, and in contralateral sham side the same volume of normal saline was injected. On each 3 animals, experimental and sham side of TMJ sections were sampled on 3, 7 and 21 days after injection. Each sections were stained with hematoxylin-eosin (H-E), toluidine blue and TUNEL for histopathological analysis. The TMJ arthritic process was assessed using semi-quantitative histopathological grading scores. Statistical significance in comparison between experimental and sham side of TMJ arthiritis was evaluated with Mann-Whitney U-test. In comparison to sham side, significantly reduced joint inflammation and cartilage destruction in the experimental side was observed at day 7 and 21 by H-E and toluidine blue staining, and TUNEL positive chondrocytes decreased from day 3 to 21 after induction. This study suggested that intrarticular injection of the anti-TNF-alpha antibody might protect joint inflammation and cartilage destruction in antigen-induced arthritis model of the rabbit TMJ.

Influence of altered occlusal plane on rabbit temporomandibular joint cartilage

There is limited knowledge relating to the influence of mechanical stress on the temporomandibular joint (TMJ) and the degree of damage this stress can induce in the case of an altered occlusal plane on the extracellular matrix cartilage and chondrocytes. The aim of this study was to examine the histopathological influence of an altered occlusal plane on rabbit TMJ cartilage. Fifteen male Japanese white rabbits were used in this study. In 12 cases, the upper right and lower left teeth were ground to their cervical level so that the occlusal plane was tilted right side up. Their temporomandibular joints (TMJs) harvested at 3 days, 1, 2 and 4 weeks were analyzed immunocytochemically and immunohistochemically. The terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate biotin nick endlabeling (TUNEL) method was used for immunocytochemical study to detect DNA fragmentation in chondrocytes. An immunohistochemical study was also performed to evaluate the metabolism of type 2 collagen in the extracellular matrix in the TMJ cartilage. The number of apoptotic cells increased in all experimental animals. More apoptotic cells were observed in the articular eminences than in the condyles. The type 2 collagen-positive area in the condyles was reduced at the beginning but recovered within 4 weeks, and remained small throughout this experimental period in the articular eminences. These findings suggest that histopathological changes occurred in response to alteration of the occlusal plane. The influence decreased as the occlusal plane recovered in the condyles, but the immunocytochemical and immunohistochemical influence continued in the articular eminences.

Pushing the limit: masticatory stress and adaptive plasticity in mammalian craniomandibular joints

Excessive, repetitive and altered loading have been implicated in the initiation of a series of soft- and hard-tissue responses or ;functional adaptations' of masticatory and locomotor elements. Such adaptive plasticity in tissue types appears designed to maintain a sufficient safety factor, and thus the integrity of given element or system, for a predominant loading environment(s). Employing a mammalian species for which considerable in vivo data on masticatory behaviors are available, genetically similar domestic white rabbits were raised on diets of different mechanical properties so as to develop an experimental model of joint function in a normal range of physiological loads. These integrative experiments are used to unravel the dynamic inter-relationships among mechanical loading, tissue adaptive plasticity, norms of reaction and performance in two cranial joint systems: the mandibular symphysis and temporomandibular joint (TMJ). Here, we argue that a critical component of current and future research on adaptive plasticity in the skull, and especially cranial joints, should employ a multifaceted characterization of a functional system, one that incorporates data on myriad tissues so as to evaluate the role of altered load versus differential tissue response on the anatomical, cellular and molecular processes that contribute to the strength of such composite structures. Our study also suggests that the short-term duration of earlier analyses of cranial joint tissues may offer a limited notion of the complex process of developmental plasticity, especially as it relates to the effects of long-term variation in mechanical loads, when a joint is increasingly characterized by adaptive and degradative changes in tissue structure and composition. Indeed, it is likely that a component of the adaptive increases in rabbit TMJ and symphyseal proportions and biomineralization represent a compensatory mechanism to cartilage degradation that serves to maintain the overall functional integrity of each joint system. Therefore, while variation in cranial joint anatomy and performance among sister taxa is, in part, an epiphenomenon of interspecific differences in diet-induced masticatory stresses characterizing the individual ontogenies of the members of a species, this behavioral signal may be increasingly mitigated in over-loaded and perhaps older organisms by the interplay between adaptive and degradative tissue responses.

Relationship between TNF‐α and TUNEL‐positive chondrocytes in antigen‐induced arthritis of the rabbit temporomandibular joint

Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate biotin nick end-labeling (TUNEL) staining is a widely accepted method for the detection of DNA fragmentation in nuclei of apoptotic cells. Tumor necrosis factor (TNF)-alpha is closely associated with changes in condylar cartilage and modulates apoptosis in various tissues including cartilage. The aim of this study was to investigate the relationship between apoptotic chondrocytes and TNF-alpha in a rabbit model of arthritis. Unilateral temporomandibular joint (TMJ) arthritis was induced in 20 adult New Zealand White rabbits. From 1 day to 6 weeks after the induction of arthritis, immunohistochemical analysis for TNF-alpha and TUNEL was performed. In condylar cartilage, TNF-alpha-positive cells and TUNEL-positive cells were localized together. TNF-alpha-positive chondrocytes seemed to precede TUNEL-positive cells. The results of the present study suggest that TNF-alpha may be involved in apoptosis and/or apoptotic necrosis of chondrocytes as TMJ arthritis progresses from the acute to chronic stage.

1. ウサギ抗原誘発顎関節炎の下顎頭軟骨細胞におけるTNF-αおよびTUNEL陽性細胞の検討(12月例会講演抄録)

1. ウサギ抗原誘発顎関節炎の下顎頭軟骨細胞におけるTNF-αおよびTUNEL陽性細胞の検討(12月例会講演抄録)

Relaxin and β-estradiol modulate targeted matrix degradation in specific synovial joint fibrocartilages: progesterone prevents matrix loss

Relaxin, a 6-kDa polypeptide hormone, is a potent mediator of matrix turnover and contributes to the loss of collagen and glycosaminoglycans (GAGs) from reproductive tissues, including the fibrocartilaginous pubic symphysis of several species. This effect is often potentiated by β-estradiol. We postulated that relaxin and β-estradiol might similarly contribute to the enhanced degradation of matrices in fibrocartilaginous tissues from synovial joints, which may help explain the preponderance of diseases of specific fibrocartilaginous joints in women of reproductive age. The objective of this study was to compare the in vivo effects of relaxin, β-estradiol, and progesterone alone or in various combinations on GAG and collagen content of the rabbit temporomandibular joint (TMJ) disc fibrocartilage, knee meniscus fibrocartilage, knee articular cartilage, and the pubic symphysis. Sham-operated or ovariectomized female rabbits were administered β-estradiol (20 ng/kg body weight), progesterone (5 mg/kg), or saline intramuscularly. This was repeated 2 days later and followed by subcutaneous implantation of osmotic pumps containing relaxin (23.3 μg/kg) or saline. Tissues were retrieved 4 days later and analyzed for GAG and collagen. Serum relaxin levels were assayed using enzyme-linked immunosorbent assay. Relaxin administration resulted in a 30-fold significant (p < 0.0001) increase in median levels (range, approximately 38 to 58 pg/ml) of systemic relaxin. β-estradiol, relaxin, or β-estradiol + relaxin caused a significant loss of GAGs and collagen from the pubic symphysis and TMJ disc and of collagen from articular cartilage but not from the knee meniscus. Progesterone prevented relaxin- or β-estradiol-mediated loss of these molecules. The loss of GAGs and collagen caused by β-estradiol, relaxin, or β-estradiol + relaxin varied between tissues and was most prominent in pubic symphysis and TMJ disc fibrocartilages. The findings suggest that this targeted modulation of matrix loss by hormones may contribute selectively to degeneration of specific synovial joints.

Relationship between TNF-α and TUNEL-positive chondrocytes in antigen-induced arthritis of the rabbit temporomandibular joint

Relationship between TNF-α and TUNEL-positive chondrocytes in antigen-induced arthritis of the rabbit temporomandibular joint

Evaluation of the anti‐inflammatory effect of erythromycin on aseptic inflammation of temporomandibular joint in rabbit: a scintigraphic and histopathologic study

This article investigates the anti-inflammatory effects of erythromycin (EM) on aseptic inflammation of temporomandibular joint (TMJ) space using by Tc-99 m HIG scintigraphy and histopathology. In this experimental study, 33 adult male New Zealand White rabbits were divided into three groups. The animals in the first group were treated with EM 25 mg kg(-1); the animals in the second group were treated with methylprednisolone (MP) 2 mg kg(-1) and the animals in the third group were given saline solution (control group). Each drug was given by intraperitoneal injection twice a day for 7 days. Two hours after the last injection, carrageenan was injected into right TMJ of rabbits for aseptic inflammation. After carrageenan injection, each rabbit was given an intravenous injection of 111 Mbq (3 mCi) Tc-99 m human HIG, and scanning was performed 4 h later. Later, all animals were killed and TMJ and periarticular tissues were resected. Histopathologically, the distance between synovial surface epithelium (SSE) and muscle layer (ML) in each section was measured by using SAMBA 200 Cell image processor with software. Scintigraphically, when lesion activity/adjacent region activity (L/N) was evaluated there was a significant difference between the control group and the other two groups (P < 0.05 for EM and MP). However, no significant difference was found between the EM and MP groups. Histopathologically, the mean distance between SSE and ML in the sections was found longer in the control group (78.6 +/- 10.7 microm) than in the EM (44.38 +/- 18.26 microm) and MP (44.05. +/- 18.25 microm) groups. We think that administration of EM, which is a well-known macrolid antibiotic, might be very effective in the treatment of aseptic inflammation of TMJ space. Because corticosteroid administration has many side effects, EM may be a preferable drug in the treatment of inflammation of TMJ.

Hypoxia increases expression of matrix metalloproteinase-3 in temporomandibular joint disc cells

Objectives. The aim of this study was to test the hypothesis that hypoxia plays a substantial role in the expression of matrix metalloproteinase-3 (MMP-3) in temporomandibular joint (TMJ) disc cells and may have a role in the pathogenesis of temporomandibular disorders (TMD).Study design. (1) Immunohistochemical study of human TMJ discs: The expressions of MMP-3 and hypoxia inducible factor 1-alpha (HIF-1α) in human TMJ discs were examined by immunohistochemical method using anti-MMP-3 and anti-HIF-1α antibodies. Twelve human TMJ discs (10 samples with internal derangement of the TMJ and 2 control samples) were used. (2) In vitro study of rabbit TMJ disc cell: The TMJ disc cells were isolated from rabbit TMJ and cultured in Dulbecco's modified Eagle's medium. The experiment was performed in hypoxic (2% O2) and IL-1β–stimulated conditions. To examine the effect of hypoxia on gene expression of MMP-3, reverse-transcription polymerase chain reaction (RT-PCR) and real-time RT-PCR were performed. To examine the effect of hypoxia on protein synthesis and activity of MMP-3, immunofluorescent staining, western blot analysis, and casein zymography were performed.Results. (1) The positive expressions of MMP-3 and HIF-1α were observed in the internal derangement of the TMJ, whereas no or weak positive expressions were observed in the control samples. (2) Hypoxia caused a significant increase of gene expression (P < 0.05) and protein synthesis of MMP-3.Conclusions. These findings suggest that hypoxia may contribute to the degradation or remodeling of the extracellular matrix of the TMJ disc and may have a role in the pathogenesis of TMD. Objectives. The aim of this study was to test the hypothesis that hypoxia plays a substantial role in the expression of matrix metalloproteinase-3 (MMP-3) in temporomandibular joint (TMJ) disc cells and may have a role in the pathogenesis of temporomandibular disorders (TMD). Study design. (1) Immunohistochemical study of human TMJ discs: The expressions of MMP-3 and hypoxia inducible factor 1-alpha (HIF-1α) in human TMJ discs were examined by immunohistochemical method using anti-MMP-3 and anti-HIF-1α antibodies. Twelve human TMJ discs (10 samples with internal derangement of the TMJ and 2 control samples) were used. (2) In vitro study of rabbit TMJ disc cell: The TMJ disc cells were isolated from rabbit TMJ and cultured in Dulbecco's modified Eagle's medium. The experiment was performed in hypoxic (2% O2) and IL-1β–stimulated conditions. To examine the effect of hypoxia on gene expression of MMP-3, reverse-transcription polymerase chain reaction (RT-PCR) and real-time RT-PCR were performed. To examine the effect of hypoxia on protein synthesis and activity of MMP-3, immunofluorescent staining, western blot analysis, and casein zymography were performed. Results. (1) The positive expressions of MMP-3 and HIF-1α were observed in the internal derangement of the TMJ, whereas no or weak positive expressions were observed in the control samples. (2) Hypoxia caused a significant increase of gene expression (P < 0.05) and protein synthesis of MMP-3. Conclusions. These findings suggest that hypoxia may contribute to the degradation or remodeling of the extracellular matrix of the TMJ disc and may have a role in the pathogenesis of TMD.

Histological changes in the temporomandibular joint in rabbits depending on the extent of mandibular lengthening by osteodistraction

Histological changes in the temporomandibular joint in rabbits depending on the extent of mandibular lengthening by osteodistraction

Histological changes in the temporomandibular joint in rabbits depending on the extent of mandibular lengthening by osteodistraction

We studied the histological changes in the temporomandibular joint (TMJ) after unilateral mandibular distraction osteogenesis in rabbits. Eight rabbits were used, two of which served as controls and the other six had distraction of the left mandibular body after a latency period of 7 days at a rate of 0.5mm a day for a total of 2mm (n = 2), 3.5mm (n = 2), and 5mm (n = 2) of distraction. After a 14-day consolidation period, TMJs from both sides were harvested and prepared for histological examination under an optical microscope using haematoxylin and eosin stain. We found no degenerative or inflammatory changes in either TMJ in any of the groups. Endochondral ossification in the condyle was greater on the opposite side in the experimental group than in the condyles of the control group. Endochondral ossification was active in the 3.5-mm group.

Role of hypoxia and interleukin-1β in gene expressions of matrix metalloproteinases in temporomandibular joint disc cells

The aim of this study was to test the hypothesis that hypoxia and interleukin-1 (IL-1)β played a substantial role in gene expressions of matrix metalloproteinases (MMPs) in temporomandibular joint (TMJ) disc cells. The TMJ disc cells were isolated from rabbit TMJ, and cultured in Dulbecco’s modified Eagle’s medium (DMEM). The experiment was performed for 24 h in hypoxic (2% O 2) and IL-1β stimulated conditions. To examine the effect of hypoxia and IL-1β on gene expression of MMPs and tissue inhibitors of metalloproteinase (TIMPs), we performed reverse transcription–polymerase chain reaction (RT–PCR) and real-time RT-RCR. The results showed that the combination of hypoxia and IL-1β caused a significant increase of MMP-1, MMP-3, MMP-9 and MMP-13 mRNA ( P < 0.05). Hypoxia caused a significant increase of MMP-2 mRNA ( P < 0.05). The combination of hypoxia and IL-1β caused a significant decrease of TIMP-3 compared to hypoxia ( P < 0.05). These findings suggest that hypoxia and IL-1β may contribute to the degradation or remodelling of the extracellular matrix (ECM) of the disc and may have a role in the pathogenesis of TMJ disorders.

MRI and histology of collagen template disc implantation and regeneration in rabbit temporomandibular joint: preliminary report

Introduction We aimed to evaluate regeneration of injured temporomandibular joint (TMJ) discs following reconstituted collagen template implantation in rabbits using contrast-enhanced magnetic resonance imaging (MRI) and to correlate these findings with histology. Methods Twenty-four adult rabbits were divided into five groups: group A, partial discectomy without implantation ( n = 6); group B, partial discectomy with collagen template implantation ( n = 6); group C, partial discectomy with subdermal graft implantation ( n = 6); group D, sham operation ( n = 4); and group E, control ( n = 2). All rabbits received baseline MRI scans before surgery and follow-up MRI studies at 3 months after surgery. All rabbits were sacrificed for histologic analysis after the follow-up MRI. Results In group A, follow-up MRI showed marked joint effusion in all six injured TMJs, which was accompanied by bony erosion at the tympanic fossa and mandibular condyle. In group B, MRI showed a homogenous low signal intensity in five of six discs, suggestive of regeneration. One disc showed higher signal intensity at its lateral portion than that of the original disc, indicating partial regeneration. MRI of group C depicted a low signal intensity, bandlike regenerative structure in four of the six discs. One disc with partial regeneration demonstrated relatively high signal intensity. The disc in the sixth animal of this group showed no evidence of regeneration. All of the MRI findings were in agreement with the histologic findings. Conclusion TMJ discs can regenerate following implantation of a reconstituted collagen template in discectomied rabbits. Contrast-enhanced MRI can be used to monitor and determine the degree of disc regeneration.

Involvement of tumor necrosis factor-alpha and interleukin-8 in antigen-induced arthritis of the rabbit temporomandibular joint.

In temporomandibular joint (TMJ) arthritis, knowledge is limited about the source of the inflammatory mediators. The aim of this study was to investigate the immunohistochemical role of tumor necrosis factor-alpha (TNF-alpha) and interleukin-8 (IL-8) in the development of the antigen-induced arthritis of the rabbit TMJ. Unilateral TMJ arthritis was induced in 28 adult rabbits. From 6 h to 6 weeks after induction of arthritis, the topology of TNF-alpha and IL-8 was observed. Positive reaction for TNF-alpha of synovial cells was observed within 3 days after induction and at 3 weeks after induction. TNF-alpha positive vascular endothelial cells and chondrocytes were identified throughout the observation period. IL-8 was detected only during the acute stage. The cytokines TNF-alpha and IL-8 were observed in specific cells depending on the stage. TNF-alpha was particularly related with angiogenesis and cartilage destruction and IL-8 was involved in the acute stage of inflammation.