3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Signal transduction pathways controlling the induction of bone formation by macroporous biomimetic matrices(2015-03-27) Klar, Roland ManfredIn spite of vigorous research efforts to date the induction of bone formation by macroporous coral-derived constructs when implanted heterotopically in the rectus abdominis muscle of the non-human primate Chacma baboon Papio ursinus has not yet been resolved and needs to be assigned. More importantly, the apparent redundancy of molecular signals singly initiating the induction of bone formation in primate species and the heterotopic induction of endochondral bone formation by the mammalian recombinant human transforming growth factor –β3 (rhTGF-β3) isoform have not yet been assigned and need to be mechanistically resolved. Using the rectus abdominis muscle of Papio ursinus the study sought to molecularly determine how coral-derived macroporous constructs and doses of the hTGF-β3 isoform initiate the induction of bone formation. To elucidate the function of osteoclastogenesis and Ca2+, biomimetic coral-derived 7% hydroxyapatite/calcium carbonate (7% HA/CC) devices were supplemented either with 240 μg zoledronate bisphosphonate, an osteoclast binding antagonist, or 500 μg of the calcium channel blocker verapamil hydrochloride. Additionally but in separate coralderived bioreactors, 125 μg rhTGF-β3 and/or 125 μg hNoggin were added to answer the question of how TGF-β3 induces bone formation. All devices were then subsequently implanted within heterotopic sites of the rectus abdominis muscle of 6 Papio ursinus and left in vivo for 15, 60 and 90 days. Harvested specimens were subjected to histomorphometrical and quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis. Collagen Type IV expression supported by extensive vascularisation was detected and observed respectively in all implants after 15 days in vivo. Importantly the zoledronate treated specimens possessed delayed tissue patterning and morphogenesis,Item The effects of citral and wortmannin on the morphology and differentiation of the developing mouse tooth(2009-09-16T10:09:46Z) Klar, Roland ManfredOdontogenesis has been extensively studied to ascertain the cellular pathways and biochemical signals that help to regulate this developmental system. Various gene families and growth factors that been identified as important regulators of tooth development. However other molecules such as retinoic acid and PI3K have also been implicated in the regulation of tooth development, especially in the initiation stage of tooth development and cusp morphogenesis. By inhibiting RA synthesis with citral, and PI3K activation using wortmannin, the study sought to investigate how amelogenesis and cusp morphogenesis were affected in murine developing first mandibular molars. Tooth development of the 14.5 and 16.5 day embryonic mouse, in vitro for 12 days, did not progress beyond the early bell stage. This was indicated by the absence of an enamel layer and possible remnant basement membrane in the cultured molars. Furthermore, no deviations in cusp morphology were observed, when inhibitors against either RA or PI3K were applied. However utilizing QRT-PCR, it was noted that the synthesis of amelogenin-mRNA increased in the 14.5 day tooth explants treated with citral, but not in the 16.5 day molar explants subjected to the same treatment. These results could therefore suggest that the degradative pathways or feedback systems controlling amelogenin-mRNA levels are inactive prior to the onset of amelogenesis on day 15-16. On the other hand, PI3K did not appear to regulate amelogenin expression, in either 14.5 or 16.5 day embryonic mouse molar explants that were treated with wortmannin. Statistical analysis revealed no changes in the laminin α5-mRNA levels in either 14.5 or 16.5 day molars treated with either citral or wortmannin, which suggests that PI3K is not the only cellular pathway that controls laminin-mRNA synthesis.