Temporomandibular joint (TMJ) disc displacement is one of the most significant subtypes of temporomandibular joint disorders, but its etiology and mechanism are poorly understood. In this study, we elucidated the mechanisms by which destruction of inflamed collagen fibrils induces alterations in the mechanical properties and positioning of the TMJ disc. By constructing a rat model of TMJ arthritis, we observed anteriorly dislocated TMJ discs with aggravated deformity in vivo from five weeks to six months after a local injection of Freund's complete adjuvant. By mimicking inflammatory conditions with interleukin-1 beta in vitro, we observed enhanced expression of collagen-synthesis markers in primary TMJ disc cells cultured in a conventional two-dimensional environment. In contrast, three-dimensional (3D)-cultivated disc cell sheets demonstrated the disordered assembly of inflamed collagen fibrils, inappropriate arrangement, and decreased Young's modulus. Mechanistically, inflammation-related activation of the nuclear factor kappa-B (NF-κB) pathway occurs during the progression of TMJ arthritis. NF-κB inhibition reduced the collagen fibril destruction in the inflamed disc cell sheets in vitro, and early NF-κB blockade alleviated collagen degeneration and dislocation of the TMJ discs in vivo. Therefore, the NF-κB pathway participates in the collagen remodeling in inflamed TMJ discs, offering a potential therapeutic target for disc displacement.
Animals ; NF-kappa B/metabolism* ; Temporomandibular Joint Disorders/pathology* ; Temporomandibular Joint Disc/metabolism* ; Rats ; Rats, Sprague-Dawley ; Disease Models, Animal ; Male ; Collagen/metabolism* ; Cells, Cultured ; Joint Dislocations/pathology* ; Interleukin-1beta ; Arthritis, Experimental

Collagen is the building component of temporomandibular joint (TMJ) discs and is often affected by inflammation in temporomandibular disorders. The macromechanical properties of collagen are deteriorated by chronic inflammation. However, the mechanism by which inflammation influences disc function remains unknown. The relationship between the ultrastructure and nanomechanical properties of collagen in inflamed discs should be clarified. Seven-week-old female Sprague-Dawley rats were randomly divided into two groups. Chronic TMJ inflammation was induced by intra-articular injection of complete Freund's adjuvant, and samples were harvested after 5 weeks. Picrosirius staining revealed multiple colours under polarized light, which represented alternative collagen bundles in inflamed discs. Using atomic force microscopy scanning, the magnitude of Young's modulus was reduced significantly accompanied with disordered collagen fibril arrangement with porous architecture of inflamed discs. Transmission electron microscopy scanning revealed a non-uniform distribution of collagen fibres, and oversized collagen fibrils were observed in inflamed discs. Fourier transform infrared microspectroscopy revealed a decrease in 1 338 cm/amide II area ratio of collagen in different regions. The peak positions of amide I and amide II bands were altered in inflamed discs, indicating collagen unfolding. Our results suggest that sustained inflammation deteriorates collagen structures, resulting in the deterioration of the ultrastructure and nanomechanical properties of rat TMJ discs.
Animals ; Collagen ; ultrastructure ; Female ; Fibrillar Collagens ; ultrastructure ; Freund's Adjuvant ; adverse effects ; Inflammation ; chemically induced ; metabolism ; pathology ; Injections, Intra-Articular ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Temporomandibular Joint ; Temporomandibular Joint Disc ; physiopathology ; ultrastructure ; Temporomandibular Joint Disorders ; physiopathology

The present paper is aimed to observe the effects of basic fibroblast growth factor (bFGF) on bone marrow mesenchymal stem cell (BMSCs) differentiation. The bFGF was used to stimulate BMSCs and histology, immunohistochemistry and enzyme linked immunosorbent assay (ELISA) were used to examine the extracellular matrix produced by induced BMSCs, evaluated the feasibility of BMSCs being the seeding cells of temporomandibular joint (TMJ) disc tissue engineering. The results showed that having been induced with bFGF, the BMSCs could differentiate into fibroblast-like cells, which could synthesize GAG and collagen type I matrix. So it is feasible for BMSCs as seeding cells for engineered TMJ disc.
Animals ; Bone Marrow Cells ; cytology ; Cell Differentiation ; drug effects ; Cells, Cultured ; Collagen Type I ; biosynthesis ; Fibroblast Growth Factor 2 ; pharmacology ; Glycosaminoglycans ; biosynthesis ; Goats ; Mesenchymal Stromal Cells ; cytology ; metabolism ; Temporomandibular Joint Disc ; cytology ; Tissue Engineering

OBJECTIVETo examine the effects of high and low concentrations of transforming growth factor (TGF) β(1) and insulin-like growth factor-I (IGF-I) on the extracelluar matrix synthesis of the self-assembled constructs of temporomandibular joint (TMJ) disc.

METHODSThe experimental groups of self-assembled constructs were exposed to IGF-I (10, 100 µg/L) and TGF-β(1) (5, 50 µg/L), the control groups were not added with any growth factors. All groups were examined at 3 and 6 weeks for gross morphological, histological, and biochemical changes. Safranin-O/fast green staining was used to examine glycosaminoglycan (GAG) distribution, picrosirius red and immunohistochemical staining to observe type I collagen distribution. Type I collagen contents were tested by ELISA assay kit, GAG contents were measured by Blyscan GAG assay kit, and the cell numbers were quantified with a Picogreen reagent kit.

RESULTSThe growth factor groups all upregulated the matrix synthesis of the self-assembled constructs compared with control groups. TGF-β(1) (5 µg/L) and IGF-I (10 µg/L) were the two most potent concentration in increasing type I collagen and GAG synthesis and cells proliferation. IGF-I group (10 µg/L) produced nearly 2 times (109.16 ± 5.12 µg) as much type I collagen as the control group (69.13 ± 5.94 µg) at 3 weeks. The matrix contents and the number of the proliferated cells in control group and all GF groups at 6 weeks were more than those at 3 weeks.

CONCLUSIONSIGF-I (10 µg/L) is the most beneficial growth factor and can be applied in tissue-engineering stratigies of the temporomandibular joint disc. At the same time, the exposure time of growth factors is another key factor that affects matrix synthesis of TMJ disc constructs.

Animals ; Cell Proliferation ; drug effects ; Cells, Cultured ; Collagen Type I ; biosynthesis ; Extracellular Matrix ; metabolism ; Glycosaminoglycans ; biosynthesis ; Goats ; Insulin-Like Growth Factor I ; pharmacology ; Temporomandibular Joint Disc ; cytology ; metabolism ; Tissue Engineering ; methods ; Transforming Growth Factor beta1 ; pharmacology

BACKGROUNDThe urokinase plasminogen activator system is believed to play an important role in degradation of the extracellular matrix associated with cartilage and bone destruction; however its precise roles in temporomandibular disorders have not yet been clarified. The aims of this study were to investigate the gene expression of fibrinolytic factors urokinase plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) in the articular cartilage of rabbit temporomandibular joint (TMJ) with disc displacement (DD) and to probe the relationship between fibrinolytic activity and cartilage remodeling.

METHODSDisc displacement of right joints was performed in 36 of 78 rabbits under investigation. The animals were sacrificed at 4 days and 1, 2, 4, 8 and 12 weeks after surgery, respectively. The right joints of these animals were harvested and processed for the examination of mRNA expression of uPA and PAI-1 in articular cartilage using in situ hybridization techniques.

RESULTSThe expression of uPA and PAI-1 was co-expressed weakly in the chondrocytes from transitive zone to hypertrophic zone and mineralized zone, while no hybridizing signals were shown in proliferative zone and superficial zone in control rabbits. The most striking was the up-regulation of uPA and PAI-1 mRNA in 4-day rabbits postoperatively at the onset of cartilage degeneration. The strongest hybridizing signals for uPA and PAI-1 were seen in 2-week rabbits postoperatively. After 2 weeks, the expression of uPA and PAI-1 began to decrease and reached nearly normal level at 12 weeks.

CONCLUSIONSThe expression of the uPA/PAI-1 system coincides with the pathological changes in condylar cartilage after DD. The uPA/PAI-1 system may be one of the essential mediators in articular cartilage remodeling.

Animals ; Cartilage, Articular ; metabolism ; Female ; Joint Dislocations ; metabolism ; pathology ; Male ; Mandibular Condyle ; metabolism ; pathology ; Plasminogen Activator Inhibitor 1 ; genetics ; RNA, Messenger ; analysis ; Rabbits ; Temporomandibular Joint ; metabolism ; Temporomandibular Joint Disc ; Urokinase-Type Plasminogen Activator ; genetics

OBJECTIVETo study the characteristics of cellular metabolism of mandibular condylar chondrocytes in repairing state of osteoarthrosis and investigate its role in the pathogenesis of the disease.

METHODSTemporomandibular joint osteoarthrosis model of rabbits was created by the partial resection of joint disc and confirmed with histological diagnosis. The chondrocytes were harvested from osteoarthritic condylar cartilage in the repairing state and cultured in vitro under the monolayer culture condition. The cellular expression of cartilaginous matrix protein, collagenase and growth factors between the osteoarthritic chondrocytes and the normal controls were measured with RT-PCR technique to outline the basic feature of the osteoarthritic cells.

RESULTSThe cultured cells were confirmed as chondrocytes with their ability of expression of collagen type II and Aggrecan. In the reactive repairing state of osteoarthrosis, the chondrocytes showed the imbalance of expression of ECM proteins, and increased expression of collagenase and endogenous growth factors such as IGF-1 and TGF-beta1.

CONCLUSIONSThis study found the active anabolism of the chondrocytes within the osteoarthritic condylar cartilage and the imbalance synthesis of cartilage matrix. These repairing attempts by the osteoarthritic chondrocytes may be impossible to restore the primary homeostasis within the condylar cartilage.

Animals ; Cartilage, Articular ; metabolism ; pathology ; Cells, Cultured ; Chondrocytes ; metabolism ; Extracellular Matrix ; genetics ; metabolism ; Male ; Mandibular Condyle ; metabolism ; pathology ; Osteoarthritis ; metabolism ; pathology ; RNA, Messenger ; genetics ; metabolism ; Rabbits ; Temporomandibular Joint Disc ; pathology ; Temporomandibular Joint Disorders ; metabolism ; pathology

OBJECTIVETo study the gene expression changes in extracellular matrix of condylar cartilage following disc anterior displacement of rabbit TMJ.

METHODSThe right sides of 28 joints in 40 rabbits were subjected to surgical operation of disc displacement. The condylar Collagen II and Aggrecan mRNA expression were detected by in situ hybridization.

RESULTSCollagen II and Aggrecan mRNA mainly expressed in the lower zone of condylar chondrocyte. Aggrecan mRNA decreased faster than collagen II following disc displacement, and adjusted to normal later.

CONCLUSIONAnterior disc displacement leads to alteration of extracellurar matrix gene expression in the condylar chondrocyte, which means the start of remodeling.

Aggrecans ; Animals ; Bone Remodeling ; Cartilage, Articular ; cytology ; Chondrocytes ; metabolism ; Collagen Type II ; biosynthesis ; genetics ; Extracellular Matrix ; metabolism ; Extracellular Matrix Proteins ; biosynthesis ; genetics ; Female ; In Situ Hybridization ; Lectins, C-Type ; Male ; Mandibular Condyle ; cytology ; metabolism ; Proteoglycans ; biosynthesis ; genetics ; RNA, Messenger ; biosynthesis ; genetics ; Rabbits ; Temporomandibular Joint ; cytology ; metabolism ; Temporomandibular Joint Disc ; surgery ; Temporomandibular Joint Disorders ; etiology ; genetics ; metabolism

OBJECTIVETo study the adaptive alteration in bilaminar zone of rabbits' temporomandibular joint following disc displacement.

METHODSTwenty-six Japanese white rabbits were used in this study. Among these rabbits,6 were used as controls. The right discs of other 20 rabbits were displaced anteriorly by operation. Four of these rabbits were killedatn 1, 2, 4, 6 and 8 weeks respectively after surgery. The TMJS were studied by HE staining, Alcin bluen staining and in situ detection of type II collagen mRNA expression.

RESULTSThere appeared cartilage metaplasia after one week following disc displacement. Typical chondrocytes could be found in the bilaminar zone. The new chondrocytes expressed type II collagen.

CONCLUSIONSThe bilaminar zone of TMJ will be remodeled following disc displacement and become a disc-like tissue to function as a disc.

Animals ; Collagen Type II ; biosynthesis ; genetics ; Female ; Joint Dislocations ; metabolism ; Male ; RNA, Messenger ; biosynthesis ; Rabbits ; Temporomandibular Joint Disc ; metabolism ; pathology ; Temporomandibular Joint Disorders ; metabolism ; pathology