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dc.contributor.authorAl-Aql, Zainab Sen_US
dc.date.accessioned2020-03-04T16:35:26Z
dc.date.available2020-03-04T16:35:26Z
dc.date.issued2007
dc.date.submitted2007
dc.identifier.other(OCoLC)192016975
dc.identifier.other(OCoLC)192016975
dc.identifier.otherb27605966
dc.identifier.urihttps://hdl.handle.net/2144/39644
dc.descriptionPLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.en_US
dc.descriptionThesis (D.Sc.D.)--Boston University, Goldman School of Dental Medicine, 2007 (Orthodontics).en_US
dc.descriptionIncludes bibliography: leaves 96-103.en_US
dc.description.abstractIntroduction: Osteopontin (OPN) is a phosphoprotein found in the extracellular matrices of mineralized tissues and is believed to play a role in the remodeling of these matrices. OPN is also one of a limited number of genes that respond to mechanical strain. Distraction osteogenesis (DO) represents a unique in vivo surgical method of applied mechanical tension that induces new bone formation and therefore represents an ideal model to assess the multiple functional roles of osteopontin. Materials and Methods: Tibia distraction osteogenesis was carried out using a monolateral fixator on male transgenic mice lacking osteopontin (OPN[-/-] C57B1/6) and their background strain (C57B1/6). MicroCT was used for quantitative assessment of DO regenerate size, microstructure and mineralization at the early and late consolidation phases. Histology and molecular analyses were used to evaluate cellular functions related to ECM formation, remodeling and bone resorption. Results: In the absence of OPN, knock out mice displayed a reduced total volume of the bone regenerate at the early consolidation stage of tissue formation. However, as healing progressed this deficiency was corrected by the end of the period of consolidation. A comparison of the anabolic versus catabolic activities during distraction osteogenes is demonstrated that OPN[-/-] regenerate possessed larger numbers of osteoclasts per area of bone accompanied by an increased expression of their makers. Messenger RNAs encoding matrix metalloproteinases 2 and 9 that are associated with matrix remodeling were also induced by higher levels at the end of latency and early consolidation phases in the OPN deficient mice relative to the control animals. On the anabolic side OPN[-/-] mice displayed compensatory increase in the levels of collagen type 1 expression accompanied by an altered organization of its fibers whereas other ECM proteins displayed normal levels. Interesting, all three metalloproteinase inhibitors showed elevated expression over time and strain in the OPN[-/-] mice. Conclusion: This study showed that OPN deficiency lead to structural alterations during the early periods of bone healing; however, during the later periods healing recovered and normal union was achieved. These studies suggest that the absence of OPN led to higher activity of both osteoclasts and osteoblasts demonstrating that insufficiencies in the expression of this extracellular matrix component effects both the anabolic and catabolic activities of coupled remodeling. Thus, the earlier increases in perhaps less than optimally functional osteoclasts are coupled with the subsequent elevation in osteoblastic activities.en_US
dc.language.isoen_US
dc.publisherBoston Universityen_US
dc.rightsThis work is protected by copyright. Downloading is restricted to the BU community. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.en_US
dc.subjectOsteogenesis, distractionen_US
dc.subjectOsteopontinen_US
dc.titleOsteopontin : its role during distraction osteogenesis healingen_US
dc.typeThesis/Dissertationen_US
etd.degree.nameDoctor of Science in Dentistryen_US
etd.degree.leveldoctoralen_US
etd.degree.disciplineOrthodonticsen_US
etd.degree.grantorBoston Universityen_US


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