Jia Yu1, Eerika Mursu1, Matleena Typpö1, Sakari Laaksonen2, Hanna-Marja Voipio2, Paula Pesonen3, Aune Raustia4, Pertti Pirttiniemi4. 1. Research Unit of Oral Health Sciences, University of Oulu, Oulu, Finland. 2. Laboratory Animal Centre, University of Oulu, Oulu, Finland. 3. Northern Finland Birth Cohort Studies, University of Oulu, Oulu, Finland. 4. Research Unit of Oral Health Sciences, University of Oulu, Oulu, Finland; Medical Research Center, Oulu University Hospital, Oulu, Finland.
Abstract
OBJECTIVES: The structure of the mandibular condylar cartilage (MCC) is regulated by dynamic and multifactorial processes. The aim of this study was to examine the effects of altered dietary loading, estrogen level, and aging on the structure of the condylar cartilage and the expressions of matrix metalloproteinase (MMP) -3 and MMP-8 of rat MCC. METHODS: In this study, Crl:CD (SD) female rats were randomly divided into 3 groups according to dietary hardness: hard diet (diet board), normal diet (pellet), and soft diet (powder). In each group, the rats were further divided into 2 subgroups by ovariectomy at the age of 7 weeks. The rats were sacrificed at 5- and 14-month-old. Histomorphometric analysis of the MCC thickness was performed after toluidine blue staining. Immunochemical staining was done for MMP-3 and MMP-8. A linear mixed model was used to assess the effects of dietary loading, estrogen level, and aging. RESULTS: Increased dietary loading was the main factor to increase the MMP-3 expression and the anterior and central thickness of the MCC. Lack of estrogen was the main factor associated with decreased MMP-8. Aging was associated with the thickness changes of the whole condylar cartilage and the reduced expression of MMP-8. CONCLUSION: The condylar cartilage structure and metabolism of the female rats are sensitive to dietary loading changes, estrogen level as well as aging. The proper balance of these factors seems to be essential for the maintenance of the condylar cartilage.
OBJECTIVES: The structure of the mandibular condylar cartilage (MCC) is regulated by dynamic and multifactorial processes. The aim of this study was to examine the effects of altered dietary loading, estrogen level, and aging on the structure of the condylar cartilage and the expressions of matrix metalloproteinase (MMP) -3 and MMP-8 of rat MCC. METHODS: In this study, Crl:CD (SD) female rats were randomly divided into 3 groups according to dietary hardness: hard diet (diet board), normal diet (pellet), and soft diet (powder). In each group, the rats were further divided into 2 subgroups by ovariectomy at the age of 7 weeks. The rats were sacrificed at 5- and 14-month-old. Histomorphometric analysis of the MCC thickness was performed after toluidine blue staining. Immunochemical staining was done for MMP-3 and MMP-8. A linear mixed model was used to assess the effects of dietary loading, estrogen level, and aging. RESULTS: Increased dietary loading was the main factor to increase the MMP-3 expression and the anterior and central thickness of the MCC. Lack of estrogen was the main factor associated with decreased MMP-8. Aging was associated with the thickness changes of the whole condylar cartilage and the reduced expression of MMP-8. CONCLUSION: The condylar cartilage structure and metabolism of the female rats are sensitive to dietary loading changes, estrogen level as well as aging. The proper balance of these factors seems to be essential for the maintenance of the condylar cartilage.