Chronic inflammation deteriorates structure and function of collagen fibril in rat temporomandibular joint disc

• Published in: International journal of oral science 2019-02, Vol.11 (1), p.2-2, Article 2
• Main Authors: Cui, Sheng-Jie, Fu, Yu, Liu, Yan, Kou, Xiao-Xing, Zhang, Jie-Ni, Gan, Ye-Hua, Zhou, Yan-Heng, Wang, Xue-Dong
• Format: Article
• Language: English
• Subjects: Animals; Atomic force microscopy; Collagen; Collagen - ultrastructure; Dentistry; Female; Fibrillar Collagens - ultrastructure; Fibrils; Fourier transforms; Freund's Adjuvant - adverse effects; Inflammation; Inflammation - chemically induced; Inflammation - metabolism; Inflammation - pathology; Injections, Intra-Articular; Mechanical properties; Medicine; Microscopy; Oral and Maxillofacial Surgery; Orthopedics; Polarized light; Random Allocation; Rats; Rats, Sprague-Dawley; Structure-function relationships; Surgical Orthopedics; Temporomandibular Joint; Temporomandibular Joint Disc - physiopathology; Temporomandibular Joint Disc - ultrastructure; Temporomandibular Joint Disorders - physiopathology; Transmission electron microscopy; Ultrastructure
• ISSN: 1674-2818; 2049-3169
• DOI: 10.1038/s41368-018-0036-8

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 −1 /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. Jaw pain: Unraveling the causes Chronic inflammation damages the collagen disk that cushions the temporomandibular joint (TMJ) of the jaw, contributing to jaw disorders. Although chronic inflammation is known to harm collagen, its effects on TMJ disks were unclear. Xue-Dong Wang and Yan-Heng Zhou and coworkers at the Peking University School and Hospital of Stomatology in Beijing used advanced imaging technologies to investigate how inflammation affects TMJ collagen in rats. In TMJ disks, collagen is composed of long, intertwined threads called fibrils. Inflammation damaged the collagen’s chemical structure, preventing correct winding, and resulting in oversized and unevenly arranged fibrils. The TMJ disks were overly porous, with poor elasticity. The researchers hypothesize that these changes thicken and deform TMJ disks, leading to disk displacement and jaw disorders. Further studies are needed to