Temporomandibular inflammation regulates the matrix metalloproteinases MMP-2 and MMP-9 in limbic structures.

Temporomandibular disorder (TMD) is characterized by acute or chronic orofacial pain, which can be associated with inflammatory processes in the temporomandibular joint (TMJ) and emotional disorders. Peripheral and central sensitization in painful orofacial processes is common, and it can be triggered by peripheral inflammatory challenge with consequent neuroinflammation phenomena. Such neuroinflammation comes from inflammatory products from supportive cells, blood-brain barrier, and extracellular matrix. Here, we evaluated the possible recruitment of limbic structures for modified matrix metalloproteinases (MMPs) expression and activity during temporomandibular inflammation-induced orofacial persistent pain. The inflammatory process in TMJs of rats was induced by Freund's Complete Adjuvant (CFA) administration. The activity and expression of MMPs-2 and 9 were assessed by in situ zymography and conventional zymography, respectively. A glial colocalization with the MMPs was performed using immunofluorescence. The results evidenced both short- and long-term alterations on MMP-2 and -9 expression in the limbic structures following CFA-induced temporomandibular inflammation. The gelatinolytic activity was increased in the central amygdala, hippocampus, hypothalamus, ventrolateral periaqueductal gray (vlPAG), superior colliculus, and inferior colliculus. Finally, an increase of colocalization of MMP-2/GFAP and MMP-9/GFAP in CFA-induced inflammation groups was observed when compared with saline groups in the central amygdala and vlPAG. It is possible to suggest that glial activation is partly responsible for the production of gelatinases in the persistent orofacial pain, and it is involved in the initiation and maintenance of this process, indicating that inhibition of MMPs might be pursued as a potential new therapeutic target for TMD.

Central Role of Protein Kinase A in Promoting Trigeminal Nociception in an In Vivo Model of Temporomandibular Disorders.

AIMS: To investigate cellular changes in the spinal trigeminal nucleus (STN) and trigeminal ganglion (TG) associated with trigeminal nociception mediated by inflammation in the temporomandibular joint (TMJ). METHODS: Male Sprague-Dawley rats (n = 86) were utilized to investigate cellular and behavioral responses to prolonged TMJ inflammation caused by bilateral injection of Complete Freund's Adjuvant (CFA) in the TMJ capsules. To investigate the cellular effects of protein kinase A (PKA) in the STN, rats were injected intrathecally with the selective PKA inhibitor KT5720 prior to injection of CFA into both TMJ capsules. Levels of calcitonin gene-related peptide (CGRP), active PKA, and ionized calcium-binding adapter molecule 1 (Iba1) in the STN and expression of phosphorylated extracellular regulated kinases (p-ERK) in the TG were determined with immunohistochemistry (n ≥ 3 experiments per test condition). Nocifensive head withdrawal responses to mechanical stimulation of the cutaneous tissue over the TMJ were monitored following CFA injection in the absence or presence of KT5720 (n = 7). Statistical analysis was performed using parametric analysis of variance (ANOVA) tests. RESULTS: Intrathecal injection of KT5720 significantly inhibited the stimulatory effect of CFA on levels of CGRP, PKA, and Iba1 in the STN. In addition, administration of KT5720 decreased the average number of CFA-induced nocifensive withdrawal responses to mechanical stimulation and the CFA-mediated increase in p-ERK expression in the ganglion. CONCLUSION: These findings provide evidence that elevated PKA activity in the STN promotes cellular events temporally associated with trigeminal nociception caused by prolonged TMJ inflammation.

The role of molecular pain biomarkers in temporomandibular joint internal derangement.

There is evidence that low-grade inflammation may be responsible for pain and development of degenerative changes in temporomandibular joint internal derangement. This article reviews the current knowledge of the molecular mechanisms behind TMJ internal derangements. A non-systematic search was carried out in PubMed, Embase and the Cochrane library for studies regarding pathophysiological mechanisms behind internal derangements focusing on pain-mediating inflammatory and cartilage-degrading molecules. Recent data suggest that release of cytokines may be the key event for pain and cartilage destruction in TMJ internal derangements. Cytokines promote the release of matrix metalloproteinases (MMPs), and due to hypoxia, vascular endothelial growth factor (VEGF) is released. This activates chondrocytes to produce MMPs and reduce their tissue inhibitors (TIMPs) as well as the recruitment of osteoclasts, ultimately leading to cartilage and bone resorption. Also, proteoglycans have an important role in this process. Several cytokines, MMPs, TIMPs and VEGF have been identified in higher concentrations in the TMJ synovial fluid of patients with painful internal derangements and shown to be associated with the degree of degeneration. Other molecules that show elevated levels include hyaluronic acid synthase, disintegrin and metalloproteinase with thrombospondin motifs (ADAMTs), aggrecan, fibromodulin, biglycan and lumican. Taken together, more or less pronounced inflammation of TMJ structures with release of cytokines, MMPs and other molecular markers that interact in a complex manner may be responsible for tissue degeneration in internal derangements. As internal derangements may be symptom-free, the degree of inflammation, but also other mechanisms, may be important for pain development.

Genetic Polymorphisms of Catechol-O-Methyltransferase: Association with Temporomandibular Disorders and Postoperative Pain.

AIMS: To evaluate the association between catechol-O-methyltransferase (COMT) gene polymorphisms and temporomandibular disorders (TMD), TMD pain, psychosocial impairment related to TMD, and postoperative pain. METHODS: A total of 90 patients with a diagnosis of painful TMD and 92 matched controls were investigated for the presence of TMD, TMD pain, and psychosocial variables by the Research Diagnostic Criteria for TMD. In a prospective cohort study of 40 subjects who underwent extraction of at least one fully impacted mandibular third molar, subjects had 6 months post-surgery follow-up of postoperative pain. DNA extracted from peripheral blood was genotyped for three COMT polymorphisms (rs4680, rs6269, and rs165774) by real-time TaqMan method. The association between COMT polymorphisms and clinical variables was determined by calculating odds ratios (OR) and their 95% confidence intervals (CI). RESULTS: Homozygous AA genotype and heterozygous variant A allele carriers (genotype AG/AA) for rs165774 polymorphism were associated with increased risk of TMD compared to wild type (wt) GG genotype (OR = 9.448, P = .006; OR = 2.088, P = .017, respectively). In addition, AA genotype was associated with increased risk of arthralgia (OR = 4.448, P = .011), myofascial pain (OR = 3.543, P = .035), and chronic TMD pain (OR = 6.173, P = .006), compared to wt genotype. AA genotype for rs6269 polymorphism was related to less postoperative chronic TMD pain (P = .025) and lower postoperative acute pain at the extraction site (P = .030). No associations with depression and somatization were observed. CONCLUSION: AA genotype of rs165774 could be a significant risk factor for the development of TMD and TMD pain, while AA genotype of rs6269 presents less postoperative chronic TMD pain and acute pain at a dental extraction site.

Upregulation of lncRNA HOTAIR contributes to IL-1ß-induced MMP overexpression and chondrocytes apoptosis in temporomandibular joint osteoarthritis.

Temporomandibular joint osteoarthritis (TMJ OA) is a common and heterogeneous disease that causes painful and progressive joint degeneration, which restricts daily activities, including talking and chewing. Long noncoding RNAs (lncRNAs) are an important class of genes involved in various physiological and pathological functions, including osteoarthritis (OA).The present study aimed to identify the lncRNAs that are important in TMJ OA and their potential functions. Here, we found that HOTAIR was significantly upregulated in the synovial fluid of TMJ OA patients compared with that of normal controls. Increased HOTAIR was similarly observed in the synovial fluid of TMJ OA rabbits as compared to control rabbits. Furthermore, in interleukin-1ß (IL-1ß)-induced TMJ OA in vitro model (primary rabbit condylar chondrocytes), the expressions of matrix metalloproteinase (MMP)-1, MMP3, MMP9 and HOTAIR were all dramatically increased. Most importantly, knockdown of HOTAIR in IL-1ß-induced TMJ OA in vitro model could not only reverse the IL-1ß-stimulated expressions of MMP1, MMP3 and MMP9, but also significantly decrease the apoptosis rate induced by IL-1ß in primary rabbit condylar chondrocytes. Our data provides new insight into the mechanisms of chondrocytes destruction in TMJ OA.

ADAM10 localization in temporomandibular joint disk with internal derangement: an ex vivo immunohistochemical study.

The purpose of this study was to determine the presence of ADAM10 in temporomandibular joint disk with internal derangement. Twenty-five paraffin blocks of displaced temporomandibular joint (TMJ) disk specimens from earlier investigations were retrieved from the archives of the University of Catania. Of these 16 had been removed from females and 9 from males; 11 with anterior disk displacement with reduction (ADDwR) and 14 with anterior disk displacement without reduction (ADDwoR). The sections were dehydrated, embedded in paraffin and cut. Then they were incubated in 0.3% H2O2/methanol and half of sections from each sample were incubated in diluted rabbit polyclonal anti-ADAM10 antibody. Then biotinylated anti-mouse/anti-rabbit IgG was applied to the sections, followed by avidin-biotin-perioxidase complex. The results were analyzed and the results were that ADAM10 was overexpressed in the posterior band of sections from patients with ADDwR compared to the other bands of both ADDwR and ADDwoR sections. Overexpression correlated with severe histopathological degeneration. We believe these results have the potential to provide insights into the pathogenesis of TMJ disk degeneration and to help design new therapeutic approaches targeting the proteolytic events that lead to tissue degeneration. Early therapeutic block of ADAM10 activity could succeed in limiting aggrecan-rich matrix breakdown without affecting normal physiology.

COMT Diplotype Amplifies Effect of Stress on Risk of Temporomandibular Pain.

When measured once, psychological stress predicts development of painful temporomandibular disorder (TMD). However, a single measurement fails to characterize the dynamic nature of stress over time. Moreover, effects of stress on pain likely vary according to biological susceptibility. We hypothesized that temporal escalation in stress exacerbates risk for TMD, and the effect is amplified by allelic variants in a gene, catechol-O-methyltransferase (COMT), regulating catechol neurotransmitter catabolism. We used data from the Orofacial Pain: Prospective Evaluation and Risk Assessment prospective cohort study of 2,707 community-dwelling adults with no lifetime history of TMD on enrollment. At baseline and quarterly periods thereafter, the Perceived Stress Scale (PSS) measured psychological stress. Genotyped DNA from blood samples determined COMT diplotypes. During follow-up of 0.25 to 5.2 y, 248 adults developed examiner-verified incident TMD. PSS scores at baseline were 20% greater (P < 0.001) in adults who developed incident TMD compared with TMD-free controls. Baseline PSS scores increased by 9% (P = 0.003) during follow-up in cases but remained stable in controls. This stress escalation was limited to incident cases with COMT diplotypes coding for low-activity COMT, signifying impaired catabolism of catecholamines. Cox regression models confirmed significant effects on TMD hazard of both baseline PSS (P < 0.001), modeled as a time-constant covariate, and change in PSS (P < 0.001), modeled as a time-varying covariate. Furthermore, a significant (P = 0.04) interaction of COMT diplotype and time-varying stress showed that a postbaseline increase of 1.0 standard deviation in PSS more than doubled risk of TMD incidence in subjects with low-activity COMT diplotypes (hazard ratio = 2.35; 95% confidence limits: 1.66, 3.32), an effect not found in subjects with high-activity COMT diplotypes (hazard ratio = 1.42; 95% confidence limits: 0.96, 2.09). Findings provide novel insights into dynamic effects of psychological stress on TMD pain, highlighting that effects are most pronounced in individuals whose genetic susceptibility increases responsiveness to catecholamine neurotransmitters.

Laser therapy reduces gelatinolytic activity in the rat trigeminal ganglion during temporomandibular joint inflammation.

OBJECTIVES: To investigate whether low-level laser therapy (LLLT) alters the expression and activity of MMP-2 and MMP-9 in the trigeminal ganglion (TG) during different stages of temporomandibular joint (TMJ) inflammation in rats. It also evaluated whether LLLT modifies mechanical allodynia and orofacial hyperalgesia. MATERIALS AND METHODS: Wistar rats (±250 g) were divided into groups that received saline (SAL) or complete Freund's adjuvant (CFA, 50 µl) in the TMJ, and that later underwent LLLT (20 J cm(-2) ) at their TMJ or not (groups SAL, SAL + LLLT, CFA, and CFA + LLLT). LLLT was applied on days 3, 5, 7, and 9 after SAL or CFA. Mechanical allodynia was evaluated on days 1, 3, 5, 7, and 10; orofacial hyperalgesia was assessed on day 10. Gelatin zymography and in situ zymography aided quantification of MMPs in the TG. RESULTS: Low-level laser therapy abolished the reduction in the mechanical orofacial threshold and the increase in orofacial rubbing during the orofacial formalin test induced by CFA. LLLT also decreased the CFA-induced rise in the levels of MMP-9 and MMP-2 as well as the gelatinolytic activity in the TG. CONCLUSION: Low-level laser therapy could constitute an adjuvant therapy to treat temporomandibular disorders and prevent inflammation-induced alterations in the levels of MMP-2 and MMP-9 and in the gelatinolytic activity in TGs.

Immunohistochemical expression of matrix metalloprotease-2 and matrix metalloprotease-9 in the disks of patients with temporomandibular joint dysfunction.

PURPOSE: Matrix metalloproteases (MMPs) are tissue-remodeling enzymes that function during the remodeling process, such as in immune-inflammatory diseases. Metalloprotease-2 (MMP-2) and metalloprotease-9 (MMP-9) are gelatinases that degrade several types of extracellular matrix collagen. It is hypothesized that in temporomandibular joint (TMJ) dysfunction, MMP-2 and MMP-9 expression levels may be elevated. Therefore, the objective of this study is to determine the association of MMP-2 and MMP-9 expression with temporomandibular joint dysfunction using an immunohistochemical approach to evaluate the joint disk. MATERIAL AND METHODS: A total of 45 human temporomandibular joint samples were collected, with 36 samples in the test group (patients with anterior disk displacement with reduction (n = 29) and without reduction (n = 7)) and nine samples in the control group. The immunostaining of the TMJ disks was statistically compared between the groups (P < 0.05). RESULTS: There was a statistically significant difference for the area of MMP-2 immunostaining between the control group and the displacement disks with reduction group (ADDwR) (P = 0.048) and between the groups with disk displacement and without reduction (ADDwoR) (P = 0.029). The expression of MMP-2 was significantly elevated in the ADDwoR group. CONCLUSION: No statistically significant difference was found between the variable area of MMP-9 expression in the disk with and without disk displacement, as determined by immunohistochemical analysis. However, there was an elevation of MMP-2 expression in the disks of patients with displacement and without reduction (more severe alteration).

ADAMTS-4 and ADAMTS-5 expression in human temporomandibular joint discs with internal derangement, correlates with degeneration.

Temporomandibular joint (TMJ) internal derangement (ID) is one of the most common form of temporomandibular disorders. There is evidence showing the increased expression of matrix metalloproteinases (MMPs) in the cells from degenerated TMJ disc. ADAMTS are a large family of metalloproteases which are responsible for proteoglycans degradation. The present study aimed to evaluate ADAMTS-4 and ADAMTS-5 immunohistochemical expression in human TMJ discs from patients affected by ID, and to find out if there is any correlation with the degree of histopathological changes. Eighteen temporomandibular displaced disc specimens and sixteen TMJ disc control were used for the present study. Specimens were immunohistochemically processed and ADAMTS-4 and ADAMTS-5 expression were obtained respectively for the anterior (AB), intermediate (IB) and posterior (PB) bands and compared to the histopathological degeneration score (HDS). Immunoreactivity for ADAMTS-4 and -5, was observed in both not degenerated and degenerated human TMJ discs. Both the percentage of ADAMTS-4 and -5 immunostained cells (ES) and the intensity of staining (IS) were significantly greater in affected specimens compared with those in control discs. The ADAMTS-5 ES and IS of the 3 bands of the disc correlated to the TMJ disc HDS (0.001 < P < 0.05), on the other hand only AB and IB, ADAMTS-4 immunostaining scores correlated to HDS. According to these findings it can be assumed in that the more histopathological changes in the disc are detected, the higher levels of ADAMTS are produced. This in turn can lead to ECM breakdown and in turn to a more advanced disc displacement.

Neocartilage integration in temporomandibular joint discs: physical and enzymatic methods.

Integration of engineered musculoskeletal tissues with adjacent native tissues presents a significant challenge to the field. Specifically, the avascularity and low cellularity of cartilage elicit the need for additional efforts in improving integration of neocartilage within native cartilage. Self-assembled neocartilage holds significant potential in replacing degenerated cartilage, though its stabilization and integration in native cartilage require further efforts. Physical and enzymatic stabilization methods were investigated in an in vitro model for temporomandibular joint (TMJ) disc degeneration. First, in phase 1, suture, glue and press-fit constructs were compared in TMJ disc intermediate zone defects. In phase 1, suturing enhanced interfacial shear stiffness and strength immediately; after four weeks, a 15-fold increase in stiffness and a ninefold increase in strength persisted over press-fit. Neither suture nor glue significantly altered neocartilage properties. In phase 2, the effects of the enzymatic stabilization regimen composed of lysyl oxidase, CuSO4 and hydroxylysine were investigated. A full factorial design was employed, carrying forward the best physical method from phase 1, suturing. Enzymatic stabilization significantly increased interfacial shear stiffness after eight weeks. Combined enzymatic stabilization and suturing led to a fourfold increase in shear stiffness and threefold increase in strength over press-fit. Histological analysis confirmed the presence of a collagen-rich interface. Enzymatic treatment additionally enhanced neocartilage mechanical properties, yielding a tensile modulus over 6 MPa and compressive instantaneous modulus over 1200 kPa at eight weeks. Suturing enhances stabilization of neocartilage, and enzymatic treatment enhances functional properties and integration of neocartilage in the TMJ disc. Methods developed here are applicable to other orthopaedic soft tissues, including knee meniscus and hyaline articular cartilage.

An ex vivo study on immunohistochemical localization of MMP-7 and MMP-9 in temporomandibular joint discs with internal derangement.

Internal derangement (ID) is among the most common disorders of the temporomandibular joint (TMJ). Previous research by our group highlighted a correlation between apoptosis and TMJ ID. Metalloproteinases (MMP)-7 and -9 have been shown to play an important role in extracellular matrix ECM) homeostasis and, through it, in joint disc remodelling. The immunohistochemical expression of MMP-7 and -9 was investigated in discs from patients with TMJ ID and from healthy donors and compared with the degree of histological tissue degeneration. The collagen fibre arrangement in pathological discs exhibited varying degrees of disruption. New vessels were consistently detected; endothelial cells from these vessels were immunolabelled with both MMP-7 and MMP-9. More or less intense MMP-7 and MMP-9 immunolabelling was detected in the cytoplasm of disc cells from all patients. MMP-7 and MMP-9 immunostaining was significantly different between pathological and normal discs and correlated with the extent of histopathological degeneration. MMP-7 and MMP-9 upregulation in discs from patients with TMJ ID demonstrates their involvement in disc damage in this disorder. A greater understanding of these processes could help identify ways to curb MMP overproduction without affecting their tissue remodelling action. The design of specific inhibitors for these MMPs would not only help to gain insights into the biological roles of MMPs, but would also aid in developing therapeutic interventions for diseases associated with abnormal ECM degradation.

Apoptosis in temporomandibular joint disc with internal derangement involves mitochondrial-dependent pathways. An in vivo study.

OBJECTIVE: Two main apoptosis pathways have been identified: an extrinsic (or death receptor-mediated) and an intrinsic (or mitochondrial) pathway. Apoptotic cell death through the extrinsic pathway has just been described in temporomandibular joint disc (TMJ) with internal derangement (ID); in contrast, no data are available on the involvement of the intrinsic pathway in this tissue. The aim of this work was to investigate whether the intrinsic pathway participates in apoptosis activation in patients with TMJ ID and anterior disc displacement without reduction. MATERIALS AND METHODS: Apoptosis activation was studied in TMJ discs from 15 patients with ID and in six unaffected discs using bcl-2-associated X protein (bax), B-cell lymphoma 2 (bcl-2), cytochrome c and caspase 9 immunohistochemistry. A correlation was sought between immunohistochemical findings and degree of disc damage. RESULTS: None of the pathological TMJ disc sections were immunopositive for bcl-2; negative bcl-2 immunostaining was detected in affected discs; cytochrome c and caspase 9 immunoreactivity was greater in pathological compared to unaffected discs; the difference was significant and correlated with histopathological degeneration score data (Spearman's rho = 0.617). CONCLUSION: The present findings suggest that in-human TMJ with ID and anterior disc displacement without reduction of cell apoptosis occurs, at least partly, via the mitochondrial pathway, which contributes to the subsequent disc degeneration. These data may have clinical implications and could help devise improved treatment strategies.

Participation of microglial p38 MAPK in formalin-induced temporomandibular joint nociception in rats.

AIMS: To investigate nociceptive behavior and the immunoreactivity of microglia and phosphorylated-p38 (p-p38) mitogen-activated protein kinase (MAPK) following intracisternal administration of SB203580, a p38 MAPK inhibitor, or minocycline, a microglia inhibitor, in rats with temporomandibular joint (TMJ) inflammation. METHODS: The number of nociceptive behavioral responses was recorded for nine successive 5-minute intervals following formalin injections into the left TMJ. SB203580 or minocycline was administered intracisternally 2 hours prior to the formalin injection. Statistical analysis used one-way analysis of variance followed by least significant difference post-hoc analysis. RESULTS: The intra-articular injection of formalin increased the expression of p-p38 MAPK in the ipsilateral medullary dorsal horn. Most of the p-p38 MAPK co-localized with OX42, a microglial marker, but not with GFAP, an astrocyte marker. Intracisternal injections of SB203580 (0.5, 1, or 5 Μg) attenuated the number of nociceptive behavioral responses and the expression of p-p38 MAPK in the medullary dorsal horn. Intracisternal injections of minocycline (25 or 50 Μg) also attenuated the responses and the expression of OX42 and p-p38 MAPK in the medullary dorsal horn. CONCLUSION: These findings suggest that p38 MAPK in microglia plays an important role in the central processing of inflammatory TMJ nociception in rats. The data further indicate that a targeted blockade of the microglial p38 MAPK pathway is a potentially important new treatment strategy for inflammatory TMJ nociception.

Association of matrix metalloproteinase gene polymorphism with temporomandibular joint degeneration.

Temporomandibular joint (TMJ) degeneration is a frequent cause of orofacial pain. Matrix metalloproteinases (MMPs) degrade extracellular matrix components and play an important role in TMJ degeneration. We investigated the frequency of the MMP1 1G/2G polymorphism (rs1799750), the MMP3 5A/6A polymorphism (rs3025058), and the MMP9 C/T polymorphism (rs3918242) in individuals with TMJ degeneration, in order to analyze the association of polymorphisms in these genes with TMJ degeneration. The population studied comprised 117 healthy controls and 115 individuals diagnosed with TMJ degeneration upon examination of magnetic resonance imaging (MRI) and computed tomography (CT) images. Genotypes were determined using PCR restriction fragment length polymorphism (RFLP). Logistic regression analyses revealed an association between the MMP1 2G/2G genotype and degeneration; in contrast, there was no association between either the MMP3 or the MMP9 genotype and degeneration. Our results may indicate a role for the MMP1 polymorphism in TMJ degeneration.

Effect of catechol-O-methyltransferase polymorphism on response to propranolol therapy in chronic musculoskeletal pain: a randomized, double-blind, placebo-controlled, crossover pilot study.

INTRODUCTION: Three common haplotypes in the gene encoding catechol-O-methyltransferase (COMT) have been associated with pain modulation and the risk of developing chronic musculoskeletal pain, namely temporomandibular disorder (TMD). Haplotypes coding for higher enzymatic activity were correlated with lower pain perception. Rodent studies showed that COMT inhibition increases pain sensitivity through beta2/3-adrenergic receptors. We hypothesized that the nonselective beta-adrenergic antagonist propranolol will reduce clinical and experimental pain in TMD patients in a manner dependent on the individuals' COMT diplotype. METHODS: Forty Caucasian female participants meeting the Research Diagnostic Criteria for TMD were genotyped for COMT polymorphisms and completed a randomized, double-blind, placebo-controlled, two-period crossover pilot study. Each period consisted of a baseline assessment week followed by an intervention week (propranolol or placebo). Changes in clinical pain ratings, psychological status, and responses to heat and pressure stimuli between baseline and intervention weeks were compared across periods. RESULTS: The number of patients reporting a reduction in pain intensity rating was greater during propranolol treatment (P=0.014) compared with placebo. Propranolol significantly reduced a composite pain index (P=0.02) but did not decrease other clinical and experimental pain ratings. When stratified by the COMT high activity haplotype, a beneficial effect of propranolol on pain perception was noted in patients not carrying this haplotype, a diminished benefit was observed in the heterozygotes, and no benefit was noted in the homozygotes. CONCLUSION: COMT haplotypes may serve as genetic predictors of propranolol treatment outcome, identifying a subgroup of TMD patients who will benefit from propranolol therapy.

Expression of hyaluronan synthase 3 in deformed human temporomandibular joint discs: in vivo and in vitro studies.

The present study aimed at investigating the expression of a hyaluronan synthase (HAS) 3 in tissue samples of deformed human temporomandibular joint (TMJ) discs and cells obtained from the discs. Fifteen adult human TMJ discs (twelve diseased discs and three normal discs) were used in this study. The twelve diseased discs were obtained from twelve patients with internal derangement (ID) of TMJ. These patients all had anteriorly displaced discs and deformed discs. The tissues were immunohistochemically stained using HAS3 antibodies. In addition, the subcultured TMJ disc cells under both normal and hypoxic conditions (O2: 2%) were incubated for 3, 6, 12, and 24 h after addition of interleukin-1ß (IL-1ß) (1 ng/mL). Subsequently, the expression of HAS3 was examined using real-time reverse transcription-polymerase chain reaction (RT-PCR). The control group showed from negative to weak positive reactions for HAS3 on immunohistochemical staining. The discs extracted from twelve cases with ID presented from moderate to strong positive reactions for HAS3. The quantity of HAS3 mRNA was compared with a control group, and showed a 204-fold increase at 3 h, a 26-fold increase at 6 h, a 2.5-fold increase at 12 h and a 32-fold increase at 24 h under hypoxia with the addition of IL-1ß. The expression of HAS3 mRNA was significantly enhanced at 3 h and 24 h. The results obtained suggest that HAS3 is related to the pathological changes of human TMJ discs affected by ID.

MMP-3 activation is a hallmark indicating an early change in TMJ disorders, and is related to nitration.

Recent studies on temporomandibular joint (TMJ) disorders have suggested that matrix metalloproteinases (MMPs) are closely involved in the pathophysiological progression of the internal derangement (ID) of TMJ. The aim of this study was to investigate MMPs in synovial fluid (SF) at different stages of ID. To examine the relationship between MMP activation and ID progression, 54 SF samples from ID patients were classified based on the criteria of Wilkes and were assayed for MMP activity. It was found that MMP-3 activity was transiently increased in the intermediate stage. This increase in the active form of MMP-3 was also confirmed by Western blotting. When the 54 samples were classified into two groups based on the presence or absence of inflammatory findings, the intensity of MMP-3 activity correlated with the inflammatory symptoms. These findings suggest that MMP-3 activation is a hallmark of early degenerative changes in ID. The tylosin nitration by the peroxynitrite can regulate the enzyme activity. To elucidate the activating pathway of MMPs in vivo, nitrated proteins in SF were analysed by immunoprecipitation. Some nitrated proteins in SF were identified as MMP-2 and -3, and the nitration of MMP-3 rendered them active in vitro.

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.