Protocol on induction of TMJ articular disc degeneration in rats by utilization of botulinum toxin

Expression profile of matrix metalloproteinases in the labrum of femoroacetabular impingement

Aims

Femoroacetabular impingement (FAI) is a potential cause of hip osteoarthritis (OA). The purpose of this study was to investigate the expression profile of matrix metalloproteinases (MMPs) in the labral tissue with FAI pathology.

Methods

In this study, labral tissues were collected from four FAI patients arthroscopically and from three normal hips of deceased donors. Proteins extracted from the FAI and normal labrums were separately applied for MMP array to screen the expression of seven MMPs and three tissue inhibitors of metalloproteinases (TIMPs). The expression of individual MMPs and TIMPs was quantified by densitometry and compared between the FAI and normal labral groups. The expression of selected MMPs and TIMPs was validated and localized in the labrum with immunohistochemistry.

Results

On MMP arrays, most of the targeted MMPs and TIMPs were detected in the FAI and normal labral proteins. After data normalization, in comparison with the normal labral proteins, expression of MMP-1 and MMP-2 in the FAI group was increased and expression of TIMP-1 reduced. The histology of the FAI labrum showed disorderly cell distribution and altered composition of thick and thin collagen fibres. The labral cells expressing MMP-1 and MMP-2 were localized and their percentages were increased in the FAI labrum. Immunohistochemistry confirmed that the percentage of TIMP-1 positive cells was reduced in the FAI labrum.

Conclusion

This study established an expression profile of MMPs and TIMPs in the FAI labrum. The increased expression of MMP-1 and MMP-2 and reduced expression of TIMP-1 in the FAI labrum are indicative of a pathogenic role of FAI in hip OA development.

Cite this article:Bone Joint Res. 2020;9(4):173–181.

Low-level laser therapy stimulates tissue repair and reduces the extracellular matrix degradation in rats with induced arthritis in the temporomandibular joint

The objective of this study was to characterize morphological and biochemistry action of low-level laser therapy (LLLT) on induced arthritis in the temporomandibular joint (TMJ) of rats. Twenty-four male Wistar rats were randomly divided into groups with 12 animals each: (AG) group with arthritis induced in the left TMJ and (LG) group with arthritis induced in the left TMJ and treated with LLLT (830 nm, 30 mW, 3 J/cm(2)). Right TMJs in the AG group were used as noninjected control group (CG). Arthritis was induced by intra-articular injection of 50 μl Complete Freund's Adjuvant (CFA) and LLLT began 1 week after arthritis induction. Histopathological analysis was performed using sections stained with hematoxylin-eosin, Toluidine Blue, and picrosirius. Biochemical analysis was determined by the total concentration of sulfated glycosaminoglycans (GAGs) and evaluation of matrix metalloproteinases (MMP-2 and MMP-9). Statistical analysis was performed using paired and unpaired t tests, with p < 0.05. Compared to AG, LG had minor histopathological changes in the TMJ, smaller thickness of the articular disc in the anterior (p < 0.0001), middle (p < 0.0001) and posterior regions (p < 0.0001), high birefringence of collagen fibers in the anterior (p < 0.0001), middle (p < 0.0001) and posterior regions (p < 0.0001) on the articular disc, and statistically lower activity of MMP-2 latent (p < 0.0001), MMP-2 active (P = 0.02), MMP-9 latent (p < 0.0001), and MMP-9 active (p < 0.0001). These results suggest that LLLT can increase the remodeling and enhancing tissue repair in TMJ with induced arthritis.

Effects of high molecular weight hyaluronic acid on induced arthritis of the temporomandibular joint in rats

High molecular weight hyaluronic acid (HMWHA) has been used to treat temporomandibular joint (TMJ) disorders, but controversial results have been described. This study aimed to characterize the morphological and biochemical actions of HMWHA on induced arthritis of the TMJ. Twenty-four male Wistar rats were used, and arthritis of the TMJ was induced through an intra-articular injection of Complete Freund's Adjuvant (CFA) (50 μl). One week after arthritis induction, the animals were treated with HMWHA (once per week for three weeks). Histological analyses were performed using sections stained with hematoxylin-eosin, toluidine blue and Picrosirius. Were also performed histomorphometric analysis and birefringence of collagenous fibers (polarization microscopy). Biochemical analyses of TMJ tissues were carried out through measurements of sulfated glycosaminoglycans and zymography for evaluation of metalloproteinase-2 and -9 (MMP-2 and -9). Data were analyzed using paired t-test and unpaired t-test, with a 5% significance level. HMWHA reduced histologic changes and thickness of the articular disc, led to a greater arrangement of collagenous fibers, lower concentration of sulfated glycosaminoglycans and lower activity in all isoforms of MMP-2 and -9 in TMJs with induced arthritis. These findings suggest that HMWHA may exert a protective effect on the TMJ.

Botulinum toxin in masticatory muscles: short- and long-term effects on muscle, bone, and craniofacial function in adult rabbits

Paralysis of the masticatory muscles using botulinum toxin (BTX) is a common treatment for cosmetic reduction of the masseters as well as for conditions involving muscle spasm and pain. The effects of this treatment on mastication have not been evaluated, and claims that the treatment unloads the jaw joint and mandible have not been validated. If BTX treatment does decrease mandibular loading, osteopenia might ensue as an adverse result. Rabbits received a single dose of BTX or saline into one randomly chosen masseter muscle and were followed for 4 or 12 weeks. Masticatory muscle activity was assessed weekly, and incisor bite force elicited by stimulation of each masseter was measured periodically. At the endpoint, strain gages were installed on the neck of the mandibular condyle and on the molar area of the mandible for in vivo bone strain recording during mastication and muscle stimulation. After termination, muscles were weighed and mandibular segments were scanned with micro CT. BTX paralysis of one masseter did not alter chewing side or rate, in part because of compensation by the medial pterygoid muscle. Masseter-induced bite force was dramatically decreased. Analysis of bone strain data suggested that at 4 weeks, the mandibular condyle of the BTX-injected side was underloaded, as were both sides of the molar area. Bone quantity and quality were severely decreased specifically at these underloaded locations, especially the injection-side condylar head. At 12 weeks, most functional parameters were near their pre-injection levels, but the injected masseter still exhibited atrophy and percent bone area was still low in the condylar head. In conclusion, although the performance of mastication was only minimally harmed by BTX paralysis of the masseter, the resulting underloading was sufficient to cause notable and persistent bone loss, particularly at the temporomandibular joint.

Biochemical and anisotropical properties of tendons

Tendons are formed by dense connective tissue composed of an abundant extracellular matrix (ECM) that is constituted mainly of collagen molecules, which are organized into fibrils, fibers, fiber bundles and fascicles helicoidally arranged along the largest axis of the tendon. The biomechanical properties of tendons are directly related to the organization of the collagen molecules that aggregate to become a super-twisted cord. In addition to collagen, the ECM of tendons is composed of non-fibrillar components, such as proteoglycans and non-collagenous glycoproteins. The capacity of tendons to resist mechanical stress is directly related to the structural organization of the ECM. Collagen is a biopolymer and presents optical anisotropies, such as birefringence and linear dichroism, that are important optical properties in the characterization of the supramolecular organization of the fibers. The objective of this study was to present a review of the composition and organization of the ECM of tendons and to highlight the importance of the anisotropic optical properties in the study of alterations in the ECM.