[A comparative study of the upper airway changes of idiopathic condylar resorption and anterior open bite patients after bilateral temporomandibular joint prostheses surgery and bimaxillary orthognathic surgery]

Objective: To evaluate the 2-dimension and 3-dimension changes of upper airway of patients who were diagnosed with idiopathic condylar resorption (ICR) and anterior open bite as well as received bilateral temporomandibular joint (TMJ) prostheses replacement or bimaxillary orthognathic surgery. Methods: This study is a retrospective study. Seventeen patients diagnosed as ICR and anterior open bite in Department of Orthognathic and TMJ surgery, West China Hospital of Sichuan University were selected (January 2018 to December 2021) and divided into bilateral TMJ protheses replacement group (group R, n=8) and orthognathic group (group O, n=9), according to which surgery they have performed. In order to compare variation of upper airway before and after surgery in different dimensions and sections within the same group or between groups, Spiral computed tomography data were obtained before (1 month) and after operation (10 to 12 months) to measure the total volume of airway (VT), the maximum sagittal area (MSA), the maximum cross-sectional area (MACA), the minimum cross-sectional area (MICA), the area of the most posterior plane(PPA), the area of soft-palate plane (SPA), the area of the most posterior point of tongue base plane (PTA), the area of the root of epiglottis plane (EA), the oropharyngeal airway volume (VO), the glossopharyngeal airway volume (VG) and the laryngeal airway volume (VL). Wilcoxon signed-rank test were used to complete statistical analyses for VO (T2),SPA (T2),ΔMSA,ΔMACA in group R as well as PTA (T1),EA (T2) in group O. Statistical analyses of other items were performed with student's t test. Results: VT, VO, VG, VL, MSA, MACA, MIC, PPA, PTA and EA of group R (T2) were significantly increased after TMJ prosthesis with Lefort I osteotomy (P<0.05). Meanwhile the VT, VO, VG, MSA, MACA, MICA, PPA and SPA of group O (T2) were significantly increased (P<0.05). There were significant difference in ΔVT and ΔVL between group R [(6 854.80±3 197.82) mm3, (2 252.85±1 527.96) mm3] and group O [(3 367.91±3 124.62) mm3, (413.21±1 244.44) mm3](t=2.27, P=0.038; t=2.74, P=0.015). Conclusions: Bilateral temporomandibular joint (TMJ) prostheses replacement and bimaxillary orthognathic surgery can both enlarge the areas and volumes of upper airway in patients who suffer from ICR and anterior open bite. Compared with bimaxillary orthognathic surgery, bilateral temporomandibular joint prostheses replacement plays a more pronounced role in enlargement and reconstruction of middle-inferior section of upper airway.

[Comprehensive measurement and quantification of bio-mechanical properties of the temporomandibular joint disc]

Objective: To comprehensively investigate the biomechanical properties of the temporomandibular joint (TMJ) disc and to perfect the mechanical testing system of the TMJ disc by conducting tests of compression, tension, cyclic compression, cyclic tension, creep and friction. Methods: Fifteen fresh goat heads (weighing 2.5-3.0 kg) were purchased from the market. They were all ordinary goats (9-12 months old, body weighing 18-21 kg) regardless of gender. Bilateral articular discs (a total of 30) were dissected within 30 minutes after execution. According to the national standard for mechanical testing of viscoelastic materials, fresh TMJ disc specimens of goat were prepared and tests were carried out in physiological conditions. The universal mechanical testing machine was utilized to test biomechanical properties of TMJ discs. Results: The compressive modulus of TMJ discs was (8.41±2.12) MPa and the tensile modulus was (9.54±3.26) MPa. The mechanical characteristics would be irreversibly altered once the load exceeded the physiological range. In addition, it underwent apparent creep relaxation under continuous strain (0.5 MPa or 3.0 MPa) and the surface friction coefficient of the TMJ discs (0.015+0.011) was much lower than that of general viscoelastic materials. Conclusions: The TMJ disc was a bio-viscoelastic structure with excellent tensile and compressive properties and its surface was extremely smooth in wet conditions.

Genistein Antagonizes 17β-Estradiol Effects on Glutamate-Evoked Masseter Muscle Hypernociception in Rats

Temporomandibular disorders (TMDs) predominantly affect women of reproductive ages, with pain as the main symptom. The aim of the present study was to examine the effects of 17β-estradiol (E2) on glutamate-evoked hypernociception of masseter muscle and to examine whether genistein could antagonize the effects of E2 in female rats. Injection of glutamate into the masseter muscle dose-dependently decreased head withdrawal thresholds, a parameter for mechanical hypernociception. Head withdrawal thresholds in ovariectomized rats also decreased with increasing doses of E2 replacement, and were further aggravated by injection of glutamate (1M, 40μL) into the masseters. Genistein at doses of 7.5 and 15 mg/kg antagonized E2-induced hypernociception of masseter muscle, and at doses of 7.5, 15, and 30 mg/kg also antagonized E2 potentiation of glutamate-evoked hypernociception of masseter muscle. Genistein produced optimal antagonistic effects of E2 on nociception behavior at a dose of 15 mg/kg. On the molecular level, tyrosine phosphorylation of the NR2B subunit of the N-methyl-D-aspartate receptor (pNR2B) and phosphorylated mitogen-activated protein kinase (pERK1/2) were significantly upregulated in the hippocampus following glutamate injection and were further potentiated by E2 replacement. Genistein at dose of 15 mg/kg partially reversed E2-potentiated glutamate-evoked upregulation of pNR2B and pERK1/2 expression in the hippocampus. These results indicated that moderate doses of genistein could antagonize E2 enhanced glutamate-evoked hypernociception of masseter muscle possibly via N-methyl-D-aspartate receptor and ERK1/2 signaling pathways in the hippocampus.

Change in the posterior airway after mandibular distraction osteogenesis in patients with ankylosis of the temporomandibular joint: a retrospective study

Mandibular distraction osteogenesis (DO) has been shown to lead to considerable improvement in obstruction of the posterior airway space in patients with ankylosis of the temporomandibular joint (TMJ), and our objective was to find out if we could confirm these findings. Seventeen patients had spiral computed tomographic (CT) scans before and after DO. After treatment, the overall posterior airway space was enlarged in all three sections of the airway (oropharyngeal, glossopharyngeal, and laryngeal). We then compared rates of change in the airway among the sections using 2-dimensional and 3-dimensional assessments, and found that the rate of change in 3-dimensional assessment of volume was significantly higher than that in the 2-dimensional (62% compared with 34%). We also found that the higher 3-dimensional rate of change came from changes in the oropharyngeal and glossopharyngeal sections, while there was no significant difference between the 2- and 3-dimensional rates of change in the laryngeal section. Because the laryngeal section had the most robust enlargement after DO in both the overall area of the posterior airway space (increased by 54%) and volume (increased by 73%), we concluded that 3-dimensional assessments were more sensitive to smaller changes in the airway space during the operation. This suggests that 3-dimensional assessments are preferable in the prediction and evaluation of the effects of DO on the posterior airway space.

Glial interleukin-1β upregulates neuronal sodium channel 1.7 in trigeminal ganglion contributing to temporomandibular joint inflammatory hypernociception in rats

Background

The proinflammatory cytokine interleukin-1β (IL-1β) drives pain by inducing the expression of inflammatory mediators; however, its ability to regulate sodium channel 1.7 (Nav1.7), a key driver of temporomandibular joint (TMJ) hypernociception, remains unknown. IL-1β induces cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2). We previously showed that PGE2 upregulated trigeminal ganglionic Nav1.7 expression. Satellite glial cells (SGCs) involve in inflammatory pain through glial cytokines. Therefore, we explored here in the trigeminal ganglion (TG) whether IL-1β upregulated Nav1.7 expression and whether the IL-1β located in the SGCs upregulated Nav1.7 expression in the neurons contributing to TMJ inflammatory hypernociception.

Methods

We treated rat TG explants with IL-1β with or without inhibitors, including NS398 for COX-2, PF-04418948 for EP2, and H89 and PKI-(6-22)-amide for protein kinase A (PKA), or with adenylate cyclase agonist forskolin, and used real-time PCR, Western blot, and immunohistofluorescence to determine the expressions or locations of Nav1.7, COX-2, cAMP response element-binding protein (CREB) phosphorylation, and IL-1β. We used chromatin immunoprecipitation to examine CREB binding to the Nav1.7 promoter. Finally, we microinjected IL-1β into the TGs or injected complete Freund’s adjuvant into TMJs with or without previous microinjection of fluorocitrate, an inhibitor of SGCs activation, into the TGs, and evaluated nociception and gene expressions. Differences between groups were examined by one-way analysis of variance (ANOVA) or independent samples t test.

Results

IL-1β upregulated Nav1.7 mRNA and protein expressions in the TG explants, whereas NS398, PF-04418948, H89, or PKI-(6-22)-amide could all block this upregulation, and forskolin could also upregulate Nav1.7 mRNA and protein expressions. IL-1β enhanced CREB binding to the Nav1.7 promoter. Microinjection of IL-1β into the TGs or TMJ inflammation both induced hypernociception of TMJ region and correspondingly upregulated COX-2, phospho-CREB, and Nav1.7 expressions in the TGs. Moreover, microinjection of fluorocitrate into the TGs completely blocked TMJ inflammation-induced activation of SGCs and the upregulation of IL-1β and COX-2 in the SGCs, and phospho-CREB and Nav1.7 in the neurons and alleviated inflammation-induced TMJ hypernociception.

Conclusions

Glial IL-1β upregulated neuronal Nav1.7 expression via the crosstalk between signaling pathways of the glial IL-1β/COX-2/PGE2 and the neuronal EP2/PKA/CREB/Nav1.7 in TG contributing to TMJ inflammatory hypernociception.

Progesterone attenuates temporomandibular joint inflammation through inhibition of NF-κB pathway in ovariectomized rats

Sex hormones may contribute to the symptomatology of female-predominant temporomandibular disorders (TMDs) inflammatory pain. Pregnant women show less symptoms of TMDs than that of non-pregnant women. Whether progesterone (P4), one of the dominant sex hormones that regulates multiple biological functions, is involved in symptoms of TMDs remains to be explored. Freund’s complete adjuvant were used to induce joint inflammation. We evaluated the behavior-related and histologic effects of P4 and the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 in the synovial membrane. Primary TMJ synoviocytes were treated with TNF-α or IL-1β with the combination of P4. Progesterone receptor antagonist RU-486 were further applied. We found that P4 replacement attenuated TMJ inflammation and the nociceptive responses in a dose-dependent manner in the ovariectomized rats. Correspondingly, P4 diminished the DNA-binding activity of NF-κB and the transcription of its target genes in a dose-dependent manner in the synovial membrane of TMJ. Furthermore, P4 treatment showed decreased mRNA expression of proinflammatory cytokines, and partially reversed TNF-α and IL-1β induced transcription of proinflammatory cytokines in the primary synoviocytes. Moreover, progesterone receptor antagonist RU-486 partially reversed the effects of P4 on NF-κB pathway. In conclusion, progesterone ameliorated TMJ inflammation through inhibition of NF-κB pathway.

Estradiol upregulates voltage-gated sodium channel 1.7 in trigeminal ganglion contributing to hyperalgesia of inflamed TMJ

BACKGROUND

Temporomandibular disorders (TMDs) have the highest prevalence in women of reproductive age. The role of estrogen in TMDs and especially in TMDs related pain is not fully elucidated. Voltage-gated sodium channel 1.7 (Nav1.7) plays a prominent role in pain perception and Nav1.7 in trigeminal ganglion (TG) is involved in the hyperalgesia of inflamed Temporomandibular joint (TMJ). Whether estrogen could upregulate trigeminal ganglionic Nav1.7 expression to enhance hyperalgesia of inflamed TMJ remains to be explored.

METHODS

Estrous cycle and plasma levels of 17β-estradiol in female rats were evaluated with vaginal smear and enzyme linked immunosorbent assay, respectively. Female rats were ovariectomized and treated with 17β-estradiol at 0 μg, 20 μg and 80 μg, respectively, for 10 days. TMJ inflammation was induced using complete Freund's adjuvant. Head withdrawal thresholds and food intake were measured to evaluate the TMJ nociceptive responses. The expression of Nav1.7 in TG was examined using real-time PCR and western blot. The activity of Nav1.7 promoter was examined using luciferase reporter assay. The locations of estrogen receptors (ERα and ERβ), the G protein coupled estrogen receptor (GPR30), and Nav1.7 in TG were examined using immunohistofluorescence.

RESULTS

Upregulation of Nav1.7 in TG and decrease in head withdrawal threshold were observed with the highest plasma 17β-estradiol in the proestrus of female rats. Ovariectomized rats treated with 80 μg 17β-estradiol showed upregulation of Nav1.7 in TG and decrease in head withdrawal threshold as compared with that of the control or ovariectomized rats treated with 0 μg or 20 μg. Moreover, 17β-estradiol dose-dependently potentiated TMJ inflammation-induced upregulation of Nav1.7 in TG and also enhanced TMJ inflammation-induced decrease of head withdrawal threshold in ovariectomized rats. In addition, the estrogen receptor antagonist, ICI 182,780, partially blocked the 17β-estradiol effect on Nav1.7 expression and head withdrawal threshold in ovariectomized rats. ERα and ERβ, but not GPR30, were mostly co-localized with Nav1.7 in neurons in TG. In the nerve growth factor-induced and ERα-transfected PC12 cells, 17β-estradiol dose-dependently enhanced Nav1.7 promoter activity, whereas mutations of the estrogen response element at -1269/-1282 and -1214/-1227 in the promoter completely abolished its effect on the promoter activity.

CONCLUSION

Estradiol could upregulate trigeminal ganglionic Nav1.7 expression to contribute to hyperalgesia of inflamed TMJ.

A new hypothesis of sex-differences in temporomandibular disorders: estrogen enhances hyperalgesia of inflamed TMJ through modulating voltage-gated sodium channel 1.7 in trigeminal ganglion?

OBJECTIVE

Temporomandibular disorders (TMD) are an assorted set of clinical conditions characterized mainly by pain in the temporomandibular joint (TMJ). TMJ inflammation or synovitis is frequently observed in TMD patients and is the major reason for TMD pain. TMD is prevalent in women of childbearing age, at least twice than in men, implying that estrogen may be involved in TMD pain processing. Estrogen affects a cell mainly through the estrogen receptors (ER). The estrogen-ER complex binds to estrogen response element sequences (ERE) in the promoter region of specific genes and then exerts its regulatory potential. The voltage-gated sodium channel 1.7 (Nav1.7), whose single disruption leads to a complete loss of pain, amplifies weak stimuli in the neurons and acts as the threshold channel for firing action potentials and plays a prominent role in pain perception, including inflammatory pain. Furthermore, our previous study showed that trigeminal ganglionic Nav1.7 was involved in the hyperalgesia of the inflamed TMJ. We propose that estrogen may enhance hyperalgesia of inflamed TMJ through decrease nociceptive threshold of TMJ or inflamed TMJ by modulating both expression and channel threshold of Nav1.7 in trigeminal ganglion.

Estradiol-potentiated cadherin-11 in synovial membrane involves in temporomandibular joint inflammation in rats

Estrogen is involved in inflammation/pain of temporomandibular joint (TMJ), but the underlying mechanisms are largely unknown. Cadherin-11 plays an essential role in synovial inflammation. This study examined whether estrogen could potentiate cadherin-11 in synoviocytes and contribute to TMJ inflammatory pain. Female rats were ovariectomized, treated with increasing doses of 17β-estradiol for 10 days, and injected intra-articularly with complete Freund's adjuvant to induce TMJ inflammation. The expression of cadherin-11 in synovial membrane was evaluated. TMJ pain was blocked with intra-articular injection of anti-cadherin-11 antibody and evaluated by head withdrawal threshold. Primary TMJ synoviocytes were treated with estradiol and tumor necrosis factor (TNF)-α or blocked with anti-cadherin-11 antibody to assess the expression of cadherin-11, interleukin (IL)-6, cyclooxygenase 2 (COX-2), and inducible nitric oxide synthase (iNOS). We observed that estradiol potentiated the inflammation-induced expression of cadherin-11 in the synoviocytes of synovial membrane from inflamed TMJ. Estradiol induced cadherin-11 expression in a dose- and time-dependent manner in primary synoviocytes and further potentiated the induction of cadherin-11 by TNF-α in synoviocytes. Furthermore, an estrogen receptor antagonist or a NF-κB inhibitor partially blocked the effects of estradiol on cadherin-11 induction in the synovial membrane. Blocking cadherin-11 partially reversed the TMJ inflammatory pain and estradiol-potentiated proliferation of synovial lining cells accompanied with iNOS expression. In addition, blocking cadherin-11 reversed TNF-α-induced and estradiol-potentiated transcription of IL-6, COX-2, and iNOS in primary synoviocytes. These results suggest that estrogen aggravated TMJ inflammatory pain partially through cadherin-11-mediated release of proinflammatory cytokines and enzymes in the synoviocytes.

Estrogen aggravates iodoacetate-induced temporomandibular joint osteoarthritis

Temporomandibular joint osteoarthritis (TMJOA) is clinically characterized by female preponderance, with a female-to-male ratio of more than 2:1; however, the underlying mechanism remains obscure. We examined the effects of estrogen on TMJOA induced by monosodium iodoacetate. Female rats were randomly and equally divided into 5 groups: control, sham-ovariectomized, and ovariectomized rats treated, respectively, with 17β-estradiol (E2) at doses of 0 µg, 20 µg, and 80 µg/day until the end of the experiment. After induction of TMJOA, TMJs were evaluated by histopathology and microCT, and the expression of Fas, FasL, caspase 3, and caspase 8 was evaluated by real-time polymerase chain-reaction or immunohistochemistry. Another 5 groups of female rats were used to evaluate the effect of estrogen receptor antagonist ICI 182780 on E2 effects on TMJOA, when injected intraperitoneally into the control, sham-ovariectomized, and 80-µg-E2-treated groups. We found that E2 potentiated cartilage degradation and subchondral bone erosion in iodoacetate-induced TMJOA. E2 also potentiated mRNA expression of Fas, FasL, caspase 3, and caspase 8 in the condylar cartilage. Moreover, the estrogen receptor antagonist partially blocked E2 effects on TMJOA. These findings suggest that E2 could aggravate TMJOA, which may be an important mechanism underlying the sexual dimorphism of TMJOA.

Hippocampal nerve growth factor potentiated by 17β-estradiol and involved in allodynia of inflamed TMJ in rat

The hippocampus is believed to play an important role in sex-based differences of pain perception. Whether estrogen potentiates allodynia in the inflamed temporomandibular joint (TMJ) through affecting the expressions of pain-related genes in the hippocampus remains largely unknown. Because the nerve growth factor (NGF) is an important gene related to inflammatory pain, we tested whether hippocampal NGF may be involved in TMJ inflammatory pain. Here we showed that the rat hippocampal NGF was upregulated by TMJ inflammation induced by complete Freund adjuvant. NGF upregulation was further potentiated by estradiol in a dose-dependent manner. In contrast, NGF transcription in the amygdala, prefrontal cortex, and thalamus was not affected by TMJ inflammation and estradiol. An intrahippocampal injection of NGF antibody or NGF receptor inhibitor K252a (inhibitor for tropomyosin receptor kinase A, TrkA) reduced the allodynia of inflamed TMJ in proestrous rats. Our data suggest that the hippocampal NGF is involved in estradiol-sensitized allodynia of inflammatory TMJ pain.

PERSPECTIVE

We report that complete Freund adjuvant-induced temporomandibular joint (TMJ) inflammation upregulated hippocampal nerve growth factor (NGF) expression, and estradiol replacement potentiated this upregulation. These results propose that estradiol could modulate TMJ pain through the NGF signaling pathway in the hippocampus to exacerbate TMJ pain and offer a possible mechanism of sexual dimorphism of temporomandibular disorder pain.