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Browsing by Author "Nanda, Ravindra"
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Item Cell and matrix response of temporomandibular cartilage to mechanical loading(Elsevier, 2016-02) Utreja, Achint; Dyment, Nathaniel A.; Yadav, Sumit; Villa, Max M.; Li, Yingcui; Jiang, Xi; Nanda, Ravindra; Rowe, David W.; Department of Orthodontics and Oral Facial Genetics, School of DentistryOBJECTIVES: The generation of transgenic mice expressing green fluorescent proteins (GFPs) has greatly aided our understanding of the development of connective tissues such as bone and cartilage. Perturbation of a biological system such as the temporomandibular joint (TMJ) within its adaptive remodeling capacity is particularly useful in analyzing cellular lineage progression. The objectives of this study were to determine: (i) if GFP reporters expressed in the TMJ indicate the different stages of cell maturation in fibrocartilage and (ii) how mechanical loading affects cellular response in different regions of the cartilage. DESIGN/METHODS: Four-week-old transgenic mice harboring combinations of fluorescent reporters (Dkk3-eGFP, Col1a1(3.6 kb)-GFPcyan, Col1a1(3.6 kb)-GFPtpz, Col2a1-GFPcyan, and Col10a1-RFPcherry) were used to analyze the expression pattern of transgenes in the mandibular condylar cartilage (MCC). To study the effect of TMJ loading, animals were subjected to forced mouth opening with custom springs exerting 50 g force for 1 h/day for 5 days. Dynamic mineralization and cellular proliferation (EdU-labeling) were assessed in loaded vs control mice. RESULTS: Dkk3 expression was seen in the superficial zone of the MCC, followed by Col1 in the cartilage zone, Col2 in the prehypertrophic zone, and Col10 in the hypertrophic zone at and below the tidemark. TMJ loading increased expression of the GFP reporters and EdU-labeling of cells in the cartilage, resulting in a thickness increase of all layers of the cartilage. In addition, mineral apposition increased resulting in Col10 expression by unmineralized cells above the tidemark. CONCLUSION: The TMJ responded to static loading by forming thicker cartilage through adaptive remodeling.Item The effect of corticision on root resorption with heavy and light forces(2016-01) Murphy, Christopher; Zalajzic, Zana; Chandhoke, Taranpreet; Utreja, Achint; Nanda, Ravindra; Uribe, Flavio; Department of Orthodontics and Oral Facial Genetics, School of DentistryObjective: To investigate the association between corticision and different force magnitudes with the amount of root resorption. Methods: Forty-four male Wistar rats (7 week old) were evaluated after an orthodontic spring delivering either 10 or 100 g was placed on the left maxillary first molars to move molars mesially. Experimental rats were divided into four groups, with 11 animals in each group: (1) LF, no corticision and 10 g of orthodontic force; (2) LFC, corticision and 10 g of force; (3) HF, no corticision and 100 g of force; and (4) HFC, corticision and 100 g of force. Contralateral sides were used as unloaded controls. The total duration of the experimental period was 14 days. Two-dimensional (histomorphometric) and three-dimensional (volumetric, micro-focus X-ray computed tomography [microCT]) analysis of root craters were performed on maxillary first molars. Results: Histomorphometric and microCT analysis revealed a significant amount of resorptive areas in the experimental groups when compared to unloaded controls. However, no significant difference was detected in the amount of resorption among the four experimental groups. Conclusions: At day 14, neither the amount of force nor the cortical incision caused significant effect on root resorption that was registered by histomorphometric or microCT analysis.