Thesis defence in the University of Oulu

Doctoral Candidate

Master of Clinical Science of Stomatology Jia Yu

Faculty and research unit

University of Oulu Graduate School, Faculty of Biochemistry and Molecular Medicine, Oral health sciences
Suun terveystieteet

Field of study

Oral Development and Orthodontics

Date and time of the thesis defence

5.6.2020 12:00

Place of the thesis defence

Remote access: https://oulu.zoom.us/j/5154558853

Topic of the dissertation

Effects of loading, estrogen level, and aging on rat mandibular condylar cartilage

Opponent

Docent Janna Waltimo-Sirén, University of Helsinki

Custos

Professor, Ph.D. Pertti Pirttiniemi, University of Oulu

Sufficient loading and physiological estrogen level are beneficial for the temporomandibular joint

The temporomandibular joint (TMJ) enables complex movements and is mechanically loaded during function. The mandibular condylar cartilage (MCC), which plays a crucial role as a stress absorber during function. The MCC is composed of chondrocytes surrounded by extracellular matrix (ECM) that mainly contains collagens and proteoglycans.

TMJ degenerative disease (TMJ-DD) is characterized by degeneration of soft and hard tissues of the TMJ. The etiology of TMJ-DD is multifactorial. Loading, estrogen, and aging have been presented as potential risk factors for TMJ-DD.

The aim of the current study was to investigate the effects of loading, estrogen level, and aging on the histomorphology of rat MCC and on the expression of various biomolecules (HIF-1α, VEGF, MMP-3, MMP-8, type I, II, and X collagens) of the condylar cartilage. Loading and aging were found to be associated with histomorphological changes in the MCC, being the main factors for the thickness changes of the anterior and central parts of the MCC. Aging was also the main factor for these changes in the posterior part of the MCC.

Increased loading upregulated the expression of HIF-1α, VEGF, MMP-3, as well as the expression of type II and X collagens in the condylar cartilage. Estrogen deficiency was associatedwith lower expression of MMP-8, type II and X collagens. Aging increased the expression of type I collagen but decreased the expression of MMP-8.

The results of this study show that sufficient loading and physiological estrogen level are beneficial for the development and remodeling of the MCC, while aging is likely to increase susceptibility to reduced capacity for adaptation of the MCC.

Dissertation

Last updated: 29.5.2020