Human Temporomandibular Joint Discs Research Articles

Composite System of 3D-Printed Polymer and Acellular Matrix Hydrogel to Repair Temporomandibular Joint Disc

Tissue engineering is a promising approach to restore or replace a damaged temporomandibular joint (TMJ) disc. However, constructing a scaffold that can mimic biomechanical and biological properties of the natural TMJ disc remains a challenge. In this study, three-dimensional (3D) printing technology was used to fabricate polycaprolactone (PCL)/polyurethane (PU) scaffolds and PU scaffolds to imitate the region-specific biomechanical properties of the TMJ disc. The scaffolds were coated with polydopamine (PDA) and combined with a decellularized matrix (dECM). Then, rat costal chondrocytes and mouse L929 fibroblasts, respectively, were suspended on the composite scaffolds and the biological functions of the cells were studied. The properties of the scaffolds were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle analysis, and biomechanical testing. To verify the biocompatibility of the scaffolds, the viability, proliferation, and extracellular matrix (ECM) production of the cells seeded on the scaffolds were assessed by LIVE/DEAD staining, Cell Counting Kit-8 assay, biochemical content analysis, immunofluorescence staining, and qRT-PCR. The functionalized hybrid scaffolds were then implanted into the subcutaneous space of nude mice for 6 weeks, and the regenerated tissue was evaluated by histological staining. The biomechanical properties of PCL/PU and PU scaffolds were comparable to that of the central and peripheral zones, respectively, of a native human TMJ disc. The PDA-coated scaffolds displayed superior biomechanical, structural, and functional properties, creating a favorable microenvironment for cell survival, proliferation, ECM production, and tissue regeneration. In conclusion, 3D-printed polymer scaffolds coated with PDA and combined with dECM hydrogel were found to be a promising substitute for TMJ disc tissue engineering.

Articular Disc of a Human Temporomandibular Joint: Evaluation through Light Microscopy, Immunofluorescence and Scanning Electron Microscopy.

The extracellular matrix of the articular disc in a temporomandibular joint (TMJ) is composed mainly of collagen I and elastin. The collagen is important for resisting tensile forces, while the elastin is responsible to maintain the shape after deformation. We studied the orientation of collagen and elastin in a normal human temporomandibular joint disc by light microscopy, immunofluorescence and scanning electron microscopy. Our results demonstrated that collagen and elastin run parallel to each other in the intermediate zone with an anteroposterior orientation. From here, the orientation of two fibers groups changes into a disordered arrangement in the transition zone. Numerous elastic fibers cross with the collagen fibers, defining an interwoven knitted arrangement. The evaluation of the disc–condyle relationship shows that the medial margin of the articular disc is inserted directly at the superficial layer of the mandibular condylar cartilage. Therefore, the tensile properties of the TMJ disc are expressed in the directions corresponding to the orientation of the collagen fibers, and the complex orientation of elastin with the collagen determines the maintaining of the shape after the stresses by the joint movements. Moreover, the direct anatomical relationship between the articular disc and the mandibular condyle makes a decisive contribution to the understanding of TMJ movements.

Effect of Sustained Joint Loading on TMJ Disc Nutrient Environment

The temporomandibular joint (TMJ) disc nutrient environment profoundly affects cell energy metabolism, proliferation, and biosynthesis. Due to technical challenges of in vivo measurements, the human TMJ disc extracellular nutrient environment under load, which depends on metabolic rates, solute diffusion, and disc morphometry, remains unknown. Therefore, the study objective was to predict the TMJ disc nutrient environment under loading conditions using combined experimental and computational modeling approaches. Specifically, glucose consumption and lactate production rates of porcine TMJ discs were measured under varying tissue culture conditions (n = 40 discs), and mechanical strain-dependent glucose and lactate diffusivities were measured using a custom diffusion chamber (n = 6 discs). TMJ anatomy and loading area were obtained from magnetic resonance imaging of healthy human volunteers (n = 11, male, 30 ± 9 y). Using experimentally determined nutrient metabolic rates, solute diffusivities, TMJ anatomy, and loading areas, subject-specific finite element (FE) models were developed to predict the 3-dimensional nutrient profiles in unloaded and loaded TMJ discs (unloaded, 0% strain, 20% strain). From the FE models, glucose, lactate, and oxygen concentration ranges for unloaded healthy human TMJ discs were 0.6 to 4.0 mM, 0.9 to 5.0 mM, and 0% to 6%, respectively, with steep gradients in the anterior and posterior bands. Sustained mechanical loading significantly reduced nutrient levels (P < 0.001), with a critical zone in which cells may die representing approximately 13.5% of the total disc volume. In conclusion, this study experimentally determined TMJ disc metabolic rates, solute diffusivities, and disc morphometry, and through subject-specific FE modeling, revealed critical interactions between mechanical loading and nutrient supply and metabolism for the in vivo human TMJ disc. The results suggest that TMJ disc homeostasis may be vulnerable to pathological loading (e.g., clenching, bruxism), which impedes nutrient supply. Given difficulties associated with direct in vivo measurements, this study provides a new approach to systematically investigate homeostatic and degenerative mechanisms associated with the TMJ disc.

Regional Collagen Fiber Network in the Articular Disc of the Human Temporomandibular Joint: Biochemical 3-Tesla Quantitative Magnetic Resonance Imaging Compared to Quantitative Histologic Analysis of Fiber Arrangement.

To evaluate the regional collagen fiber network in the human temporomandibular joint (TMJ) disc by using biochemical magnetic resonance imaging (MRI) and quantitative histology. MRI of 5 heads (10 TMJ discs) obtained from partially dentate or edentulous cadavers was performed at 3-Tesla MRI by using a flexible, 8-channel transmit-receive coil. After MRI, all 10 discs were processed histologically. Percentages of coronal, sagittal, and transverse collagen fibers were assessed stereologically for the anterior, central, and posterior parts of the disc. An anisotropy index was calculated for collagen fiber arrangement in all three regions of interest. In the central part of the TMJ disc, collagen fibers were arranged anisotropically with a preferentially sagittal direction. In the anterior and posterior parts, evidence for fibers being arranged isotropically (randomly) without preferred direction was found. Mean MRI T2 values appeared to be correlated with the anisotropy index of collagen fibers (r = -0.45; P < .05). When tested individually, T2 values of the isotropic anterior and posterior disc regions showed a partial but significant correlation with the anisotropy index of collagen fibers (r = -0.54; P < .05), whereas the anisotropic central part did not (P > .05). This study has provided the first systematic comparison of quantitative data on collagen fiber isotropy and anisotropy assessed in histologic sections with biochemical quantitative MRI for human TMJ fibrous cartilage.

Expression of MMP-13 in human temporomandibular joint disc derangement and osteoarthritis

Objective: MMP-13 performs digestion of collagen, which is a primary component of the temporomandibular joint (TMJ) articular disc. This study evaluated the expression of MMP-13 in patients with anterior disc displacement with (ADDwR) and without reduction (ADDwoR), and in the presence of TMJ osteoarthrosis.Methods: Thirty-nine human temporomandibular joint disc samples were collected and divided in two ways: ADDwR (21 samples), ADDwoR (10 samples), and a control group (8 samples); and with osteoarthrosis (10 samples) and without osteoarthrosis (29 samples). Immunostaining of the TMJ discs was statistically compared between the groups.Results: There was no statistically significant difference for the area of MMP-13 immunostaining between the control group, ADDwR, and ADDwoR, nor between groups with and without osteoarthrosis.Conclusion: This study suggests MMP-13 is not significantly involved in collagen degradation in human TMJ disc displacement or osteoarthrosis.

P53 and VEGF expression in human temporomandibular joint discs with internal derangement correlate with degeneration

Aim: Temporomandibular joint (TMJ) disorders are one of the most relevant causes of chronic facial pain and disability. During histopathological conditions biomolecular mechanisms occur inducing histologic changes of the tissue itself. Human Tumor Protein p53 and Vascular Endothelial Growth Factor are related with cell-cycle control, angiogenesis and both play a central role during inflammation. The purpose of the present research was to investigate the immunoexpression and immunolocalization of Human Tumor Protein p53 and Vascular Endothelial Growth Factor in temporomandibular joint discs of individuals with internal derangement with anterior disc displacement in order to gain insights into the apoptotic and angiogenetic processes in the three bands of articular discs with or without reduction and compare them to the histological degeneration score. Methods: Paraffin samples of eighteen displaced temporomandibular joint and four control discs were analyzed by immunohistochemistry for the above evaluations. Results: Data showed a strong Human Tumor Protein p53 and Vascular Endothelial Growth Factor immunoexpression in the anterior and intermediate disc areas and a weak immunoexpression in posterior area of anterior disc displacement with reduction patients while anterior disc displacement without reduction patients demonstrated a weak Human Tumor Protein p53 and Vascular Endothelial Growth Factor immunolabelling in the anterior and intermediate areas and a strong immunoexpression in posterior band. These immunoexpressions correlated with histological degeneration score. Conclusions: According to our results it can be assumed in that when the more histopathological changes in the disc are releaved, major levels of p53 and VEGF are produced.

Tensile biomechanical properties of human temporomandibular joint disc: Effects of direction, region and sex

Approximately 30% of temporomandibular joint (TMJ) disorders include degenerative changes to the articular disc, with sex-specific differences in prevalence and severity. Limited tensile biomechanical properties of human TMJ discs have been reported. Stress relaxation tests were conducted on TMJ disc specimens harvested bilaterally from six males and six females (68.9±7.9 years), with step-strain increments of 5%, 10%, 15%, 20% and 30%, at 1% strain-per-second. Stress versus strain plots were constructed, and Young׳s Modulus, Instantaneous Modulus and Relaxed Modulus were determined. The effects of direction, region, and sex were examined. Regional effects were significant (p<0.01) for Young׳s Modulus and Instantaneous Modulus. Anteroposteriorly, the central region was significantly stiffer than medial and lateral regions. Mediolaterally, the posterior region was significantly stiffer than central and anterior regions. In the central region, anteroposteriorly directed specimens were significantly stiffer compared to mediolateral specimens (p<0.04). TMJ disc stiffness, indicated by Young׳s Modulus and Instantaneous Modulus, was higher in directions corresponding to high fiber alignment. Additionally, human TMJ discs were stiffer for females compared to males, with higher Young׳s Modulus and Instantaneous Modulus, and female TMJ discs relaxed less. However, sex effects were not statistically significant. Using second-harmonic generation microscopy, regional collagen fiber organization was identified as a potentially significant factor in determining the biomechanical properties for any combination of direction and region. These findings establish structure–function relationships between collagen fiber direction and organization with biomechanical response to tensile loading, and may provide insights into the prevalence of TMJ disorders among women.

Immunohistochemical analysis of IL-1 beta in the discs of patients with temporomandibular joint dysfunction

Purpose: Interleukin-1 beta (IL-1β) is a cytokine that participates in the regulation of immune responses and inflammatory reactions. It is hypothesized that IL-1 levels may be elevated in patients suffering from temporomandibular joint dysfunction. The purpose of this study was to determine the association of IL-1β expression with TMD using an immunohistochemical approach to evaluate the joint disc.Materials and methods: A total of 39 human temporomandibular joint disc samples were collected, with 31 samples in the test group. Nineteen of the test group samples were from discs of patients with anterior disc displacement with reduction, and 12 of the samples were from patients with anterior disc displacement without reduction. Eight control samples were used in the control group. The samples were immunostained and evaluated on both quantity and intensity of staining.Results: There was a statistically significant difference (p < 0.05) between the control and test groups for both quantity and intensity of staining.Conclusion: IL-1β plays a role in the inflammatory process and degradation of TMJ discs in patients with TMJ dysfunctions.

Engineering Human TMJ Discs with Protein-Releasing 3D-Printed Scaffolds

The temporomandibular joint (TMJ) disc is a heterogeneous fibrocartilaginous tissue positioned between the mandibular condyle and glenoid fossa of the temporal bone, with important roles in TMJ functions. Tissue engineering TMJ discs has emerged as an alternative approach to overcoming limitations of current treatments for TMJ disorders. However, the anisotropic collagen orientation and inhomogeneous fibrocartilaginous matrix distribution present challenges in the tissue engineering of functional TMJ discs. Here, we developed 3-dimensional (3D)–printed anatomically correct scaffolds with region-variant microstrand alignment, mimicking anisotropic collagen alignment in the TMJ disc and corresponding mechanical properties. Connective tissue growth factor (CTGF) and transforming growth factor beta 3 (TGFβ3) were then delivered in the scaffolds by spatially embedding CTGF- or TGFβ3-encapsulated microspheres (µS) to reconstruct the regionally variant fibrocartilaginous matrix in the native TMJ disc. When cultured with human mesenchymal stem/progenitor cells (MSCs) for 6 wk, 3D-printed scaffolds with CTGF/TGFβ3-µS resulted in a heterogeneous fibrocartilaginous matrix with overall distribution of collagen-rich fibrous structure in the anterior/posterior (AP) bands and fibrocartilaginous matrix in the intermediate zone, reminiscent of the native TMJ disc. High dose of CTGF/TGFβ3-µS (100 mg µS/g of scaffold) showed significantly more collagen II and aggrecan in the intermediate zone than a low dose (50 mg µS/g of scaffold). Similarly, a high dose of CTGF/TGFβ3-µS yielded significantly higher collagen I expression in the AP bands compared with the low-dose and empty µS. From stress relaxation tests, the ratio of relaxation modulus to instantaneous modulus was significantly smaller with CTGF/TGFβ3-µS than empty µS. Similarly, a significantly higher coefficient of viscosity was achieved with the high dose of CTGF/TGFβ3-µS compared with the low-dose and empty µS, suggesting the dose effect of CTGF and TGFβ3 on fibrocartilage formation. Together, our findings may represent an efficient approach to engineering the TMJ disc graft with anisotropic scaffold microstructure, heterogeneous fibrocartilaginous matrix, and region-dependent viscoelastic properties.

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.

Expression of β-defensin 4 on temporomandibular joint discs with anterior displacement without reduction

Objectivesβ-defensin-4 is a member of antimicrobial peptides (APs) of the immunity system. This molecule has antimicrobial activity but it seems to be involved in articular inflammatory processes too, as it happens during osteoarthritic disease (OA). Considering the possible relation existing between (OA) and temporomandibular disorders (TMD), the aim of our study was to evaluate immunohistochemically the presence of β- defensin-4 in pathological temporomandibular joint (TMJ) discs affected by internal derangement without reduction (ADDwoR). DesignEighteen TMJ-displaced disc specimens were considered in this study and were analysed by immunohistochemical evaluation. They were compared with a control sample of sixteen healthy discs and two scores, intensity of staining (IS) and extent score (ES) were estimated. ResultsFindings of our analysis showed a significant difference between control and study sample (P < 0.001). IS and ES of control sample and pathological sample were 1 and 4 respectively. ConclusionOur results confirmed the presence of β-defensin-4 in human TMJ discs affected by ADDwoR, hypothesing a possible role of this molecule in articular bone disruption.

Apoptosis in TMJ Disc Diseases

The apoptosis is the programmed cell death, a distinct process compared to cellular necrosis, which plays an important role in both human embryonic development and adult tissue homeostasis. Apoptosis represents a physiological form of cell death. The role of apoptosis is to remove harmful, damaged or unwanted cells without inducing inflammatory response by the release of cell contents [1]. Apoptosis is activated through two principal signaling pathways: intrinsic and extrinsic, both of which are potential anticancer therapeutic targets. In contrast to necrosis, which is a form of cell death resulting from an acute cellular stress or trauma, apoptosis is a death orderly and regular, does not induce inflammation, requires energy (ATP) and generally lead to an advantage during the body life. Besides its importance as a biological phenomenon, it has acquired a huge medical value, since imperfect process of apoptosis covers many diseases. Excessive activity can cause trouble by apoptotic cell loss (see, for example neurodegenerative diseases such as Parkinson’s disease), while a weak apoptosis may involve uncontrolled cell growth in malignancy mechanism [2]. Apoptosis is the most common mechanism by which the body eliminates damaged or unneeded cells, without local inflammation from leakage of cell contents. Cells that are undergoing apoptosis exhibit a characteristic pattern of morphologic changes, including cell shrinkage, condensation, fragmentation of the nucleus and bubbling of the plasma membrane, known as “blebbing,” and chromatin condensation and nucleosomal fragmentation [1,3]. Apoptosis functions through two main, alternative pathways: death receptor-mediated (or extrinsic) and mitochondria-dependent (or intrinsic). The former pathway is initiated by ligation of specific death receptors by their ligands. The main death receptors—Fas and tumour necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) receptors R1 and R2—induce cell death following ligation with Fas ligand (FasL) or TRAIL, respectively [4-7]. Ligation of TRAIL R1 by TNFα also induces apoptosis after inhibition of nuclear factor kappa-B (NF-kB). Fas ligation by FasL is followed by recruitment of FADD (Fas-associated via death domain) and subsequently of caspase 8. This process gives rise to caspase 8 activation, which can be inhibited by the anti-apoptotic molecule FLICE inhibitory protein (Flip). Caspase 8 induces apoptosis by directly activating caspase 3 or by cleaving bid (BH3 interacting domain death agonist), resulting in mitochondrial dysfunction and subsequent release of cytochrome c and activation of caspases 9 and 3. Caspase 3 promotes the typical apoptosis features, including DNA fragmentation and cell death in several tissues [8,9]. It is unclear whether repetitive loading and apoptosis are quantitatively related in any type of cartilage. Several studies have demonstrated the crucial function of apoptotic mechanisms in intervertebral disc degeneration, and the involvement of apoptosis in various conditions associated with intervertebral disc degeneration has been thoroughly explored [10]. However, apoptosis has been documented to have a central role not only in intervertebral disc degeneration [10]. Although a number of features of temporomandibular joint (TMJ) disc degeneration have been thoroughly studied, data on the involvement of apoptotic mechanisms and their mediators are few and quite recent; indeed most of the research conducted on disc apoptosis has focused on the intervertebral disc. TMJ disc degeneration is believed to be a consequence of mechanical and biological events affecting the equilibrium between matrix synthesis and degradation. According to this hypothesis loss of cellularity, collagen fibre fragmentation and TMJ disc tears and clefts would all depend on excessive apoptosis, a situation where collagen fibre degradation is not offset by synthesis of new fibres because of apoptosis-induced cell loss. The findings correlating TMJ disc internal derangement and apoptosis largely come from animal models [11]. However, our group has extensively analyzed programmed cell death in human TMJ discs with and without internal derangement [12,13]. We have advanced Corresponding author.

Aquaporin 1 expression in human temporomandibular disc

Aquaporins (AQPs) are a family of hydrophobic membrane channel proteins. The expression of several AQP isoforms has been investigated in different human tissues, including the orofacial region. However, information on the role and localization of AQP1 in joints is limited, and no data are available on aquaporins in the normal temporomandibular joint (TMJ) disc. Sixteen human TMJ discs without degenerative changes were taken from fresh cadavers to investigate the presence and distribution of AQP1 by immunohistochemistry. The aim of the study was to gain additional insights into the biomolecular composition of aquaporins and their role in homeostasis of the TMJ. Porcine TMJ discs were also studied by Western blotting for comparison. Scattered AQP1 immunoexpression was detected in human disc cells, documenting its constitutive expression, but differences amongst the three disc regions were not significant. AQP1 expression was demonstrated in porcine TMJ disc by Western blotting. Our findings suggest that AQP1 is normally expressed in the TMJ disc and confirm a role for it in the maintenance of TMJ homeostasis. Further studies are needed to elucidate expression patterns of aquaporins in diseased TMJ discs.

Lubricin in human temporomandibular joint disc: An immunohistochemical study

AimsTo evaluate, immunohistochemically, the presence and distribution of lubricin in human temporomandibular joint (TMJ) discs without any degenerative changes, obtained from autopsies, in order to elucidate the TMJ lubrication system and disc tribology. MethodsImmunohistochemistry for lubricin detection was carried out on 34 TMJ discs. Any disc had signs of degenerative or inflammatory joint disease nor disc were displaced. Sections were incubated with diluted rabbit polyclonal anti-lubricin antibody and scored according to the percentage of lubricin immunopositive cells. Three different TMJ disc tissue compartments taken from the intermediate zone were analysed, namely: the central region as well as the temporal (superior) and condylar (inferior) disc surfaces. The Friedman test, was used to compare lubricin at a protein level expression, amongst the regions of disc specimens. ResultsStaining was noted within the TMJ disc cell populations in every disc tissue sample, however, the number of disc cells immunolabelled varied according to disc tissue regions. The percentage of immunostained cells, was statistically significant lower in the central region than in each disc surface (p<0.0001), whilst any statistically significant difference was found when comparing the two surfaces one another. ConclusionsLubricin is present in several location of TMJ disc being significantly more expressed at disc surfaces than in the central part.

Immunolocalization and expression of lubricin in the bilaminar zone of the human temporomandibular joint disc

Lubricin, which is a boundary joint lubricant, was investigated immunohistochemically in the bilaminar zone (BZ) of the human temporomandibular joint (TMJ), without any degenerative changes. Immunohistochemistry for lubricin detection was carried out on 33 TMJ discs obtained from 17 cadavers. Sections were incubated with diluted rabbit polyclonal anti-lubricin antibody and scored according to the percentage of lubricin immunopositive cells. Three different TMJ disc tissue compartments were analyzed, namely: the upper lamina, the inferior lamina and the loose connective tissue in the space between the laminae. The Mann–Whitney U test was used to compare protein expression (lubricin) among disc specimens’ regions. Staining was noted within the TMJ disc cell populations in every disc tissue sample, with almost every cell immunolabeled by the lubricin antibody. The number of disc cells immunolabeled was almost the same in the 3 bilaminar zone regions. Positive extracellular matrix staining was also seen. The results of the present study suggest that lubricin is expressed in the TMJ disc bilaminar zone. Lubricin may have a role in normal disc posterior attachment physiology through the prevention of cellular adhesion as well as providing lubrication during normal bilaminar zone function.

Percentage of Lateral Pterygoid Muscle Inserted in the Disc of Human Temporomandibular Joint

La actividad de la insercion de la cabeza superior del pterigoideo lateral (CSPL) en el disco de la articulacion temporomandibular (ATM) ha sido vinculada al desplazamiento anterior del disco y disfuncion temporomandibular. El proposito de este estudio fue determinar el porcentaje de fibras musculares de la cabeza superior del musculo pterigoideo lateral que se insertan en el disco articular, en humanos adultos. Se diseno una revision sistematica de la literatura a partir de articulos primarios publicados en las bases de datos Medline, Lilacs y Scielo entre los anos 1990 y 2010. Se utilizaron las palabras clave Musculo Pterigoideo y Muscle, el Termino MeSH: con los boleanos OR Lateral Pterygoid AND Insertion y los Terminos Libres: Muscle Disc Articular y lateral Muscle Meniscus. Se obtuvieron 156 articulos, los cuales fueron analizados y se seleccionaron 18 que cumplieron con los criterios de elegibilidad. En base a estos articulos se evaluo el porcentaje de insercion de la CSPL en el disco de la ATM, posteriormente a cada uno se les otorgo un nivel de evidencia de acuerdo a la clasificacion de Oxford Centre Evidence Based Medicine (OCEBM). Solo 4 articulos respondieron a la pregunta de investigacion, 3 estudios fueron histologicos y 1 imagenologico, todos con disenos de cortes transversales con buen nivel de evidencia (1b). Sin embargo los resultados fueron disimiles, reportandose porcentajes de insercion del 2 al 69,8% de la cabeza superior del pterigoideo lateral en el disco articular.

Expression of lumican and fibromodulin following interleukin-1 beta stimulation of disc cells of the human temporomandibular joint

Small leucine-rich repeat proteoglycans (SLRP) are present in the extracellular matrix of the temporomandibular joint (TMJ) disc. Lumican and fibromodulin, classified as class 2 SLRPs, play important roles in TMJ assembly, proliferation and inflammation. Degenerative change in the TMJ disc gives rise to the process of internal derangement (ID). In this study, we immunohistochemically examined the expression of lumican and fibromodulin in nine human TMJ specimens and examined the gene expression of both proteoglycans in cultured human TMJ disc cells under interleukin-1 beta (IL-1 β)-stimulated conditions. An articular disc cell line was established by collagenase treatment of a TMJ disc. The subcultured cells were then incubated for 1, 3, 6, 12, 24 or 48 h under both normal and IL-1 β (1 ng/mL) conditions. The gene expression of lumican and fibromodulin was examined using the reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR. We demonstrated that the expression of lumican significantly differs from that of fibromodulin in the deformed disc and that IL-1 β induces a significant increase in lumican mRNA, but not in fibromodulin mRNA, after 24∼48 h culture compared to cells cultured in the absence of IL-1 β (P<0.05). These results indicate that lumican and fibromodulin display different behaviors and that lumican may promote regeneration of the TMJ after degeneration and deformation induced by IL-1 β.

Lubricin immunohistochemical expression in human temporomandibular joint disc with internal derangement

Lubricin is a chondroprotective, mucinous glycoprotein which contribute to joint lubrication, especially to boundary lubrication and maintains joint integrity. The present investigation aimed to study the immunolocalization of lubricin in TMJ discs from patients affected by anterior disc displacement with reduction (ADDwR) ADDwoR. Eighteen TMJ displaced disc affected by ADDwoR were processed immunohistochemically, with a polyclonal anti-lubricin antibody, used at 1:50 working dilution. The percentage of lubricin immunopositive cells (extent score = ES) and the extent of lubricin staining of the disc extracellular matrix (ECM), were evaluated. Each sample was scored for histopathological changes. Percentage of immunostained surface disc cells was the same (ES = 4) in both control and ADDwOR cells, being this data not statistically significant (P < 0.05). In pathological specimens the percentages of lubricin-stained cells was very high with an ES of 4 respect to control specimen, and this difference was statistically significant different (P > 0.05). The extracellular matrix (ECM) of discs at the disc surfaces of both pathological and normal specimens was very heavily stained (++++). Both the ES and ECM staining were not statistically correlated to the TMJ degeneration score according to the Spearman's rank correlation coefficient. According to our findings, a longstanding TMJ disc injury, affects lubricin expression in the TMJ disc tissue and not its surfaces, moreover, lubricin immunostaining is not correlated to TMJ disc histopathological changes.

Aquaporin 1 expression in human normal temporomandibular disc

The aquaporins (AQPs) are a family of hydrophobic membrane channel proteins that are expressed in many epithelial, endothelial and other tissues and that participate in many physiological and pathological processes. In particular aquaporin-1 (AQP1), a member of this family proteins, is expressed by the masseter and infrahyoid muscles, meckel’s cartilage and submandibular gland. Literature data on the role and the localization of AQP1 in articular joints are very poor, and none providing data on the normal temporomandibular joint (TMJ) disc. Accordantly, the present paper prompted this immunohistochemical and western blotting investigation, on the presence and distribution of AQP1 in human TMJ discs without any degenerative changes, in order to elucidate further aspects of the TMJ homeostasis system and disc tribology. Twelve TMJ discs, were obtained bilaterally from six cadavers and they were processed for immunohistochemical and Western Blot analysis. The results showed an AQP1 immunoexpression in few fibroblasts-like cells and fibrochondrocytes of normal human TMJ discs demonstrating a constitutive expression of this protein. No difference between the disc regions was seen in normal specimens. Western blot analysis of disc samples confirm the physiological AQP1 expression. In this view it appears reasonable a physiological expression of AQP1 by TMJ fibrocartilage cells and interpretable as a physiological mechanism of tissue homeostasis. Further future interesting studies could be conducted to elucidate the full AQPs profile in TMJ pathological disc investigating their change of the expression patterns during TMJ disc diseases.

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-1β (IL-1β) (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-1β. 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.