UNC School of Dentistry - The University of North Carolina at ...

#9 The Importance of IAP/cd47 in Osteoblast DifferentiationB.E. CAPPS, E.T. EVERETT, D. CLEMMONS, and L. MAILEDepartments of Endocrinology and Pediatric Dentistry, UNC Schools of Medicine and DentistryBone formation is regulated by osteoblast (OB) and osteoclast (OC) cells. The association between theextracellular domains of integrin associated protein (IAP, CD47) and SHPS-1 (MFR) has been reported to regulateOC differentiation. We have demonstrated that this association is regulated by the cleavage of IAP. IAP null micehave reduced OC function yet decreased bone mineral density. We hypothesize that this phenotype indicates IAPmay also function as a regulator of OB differentiation. Objectives: To determine a role for IAP in OBdifferentiation. Methods: The preosteoblast cell lines MC3T3-E4 and MC3T3-E24 (high and low osteogenicpotential respectively) were maintained for 8 days in osteogenic medium containing L-ascorbic acid and Betaglycerophosphate.Cultures were stained for alkaline phosphatase to assess OB differentiation. Parallel cultureswere lysed and IAP was visualized by western immunoblotting using an anti-IAP antibody that discriminatesbetween intact and fragmented IAP. Differentiation was also induced in the presence of factors that protect IAPfrom cleavage (osteopontin [1.4ug/uL], thrombospondin [1ug/mL]) and an anti-IAP antibody that accelerates IAPcleavage (B6H12 [1ug/mL]). Results: Osteogenic medium induced increased detection of intact IAP in the E4 butnot the E24 cells. In the absence of osteogenic medium, both cell lines failed to differentiate and IAP was entirelyfragmented. E24 cells that were incubated with osteopontin or thrombospondin showed a 171% and 243% increaserespectively in the number of alkaline phosphatase positive cells and an increase in the amount of intact IAP. E4cells incubated with B6H12 exhibited a 69% decrease in the number of alkaline phosphatase positive cells and adecrease in the amount of intact IAP. Conclusion: These data support the hypothesis that the modulation of IAPcleavage is important in OB differentiation and suggests the phenotype of the IAP null mice reflects a disruption inOB and OC formation. Supported by NIH# HL56850#10 Incidence of Removal of Titanium Hardware in Post-Operative Orthognathic Proceduresbetween 1999 and 2000C. POWELL and T. TURVEYDepartment of Oral & Maxillofacial Surgery and Dental Research, UNC School of DentistryObjective: The specific aim of this study is to determine the percentage of incidence of removal of Titaniumhardware after patients had undergone Orthognathic surgery over a ten year period time. This study will evaluatepossible associations between patient characteristics, extent and location of problem and incidence of postoperativefixation removal. Previous investigation has been limited to age, gender, length of surgery and bloodloss. This study will focus on all previous investigation s in addition to type and extent of surgery, locations ofproblem, amount of hardware and patient co-morbidities and lifestyle habits. Methods: Patient records and chartsalong with doctor mediated dictation were reviewed. Findings were subjected to Bio-statistical analysis. Results:Initially the studies have shown 655 individuals had surgery with metal fixation from 1999-2000. 327 patientsreported back and filed out post-operative forms for possible removal of revision. Out of the 327 patients 14 ofthose individuals reported fixation removal, this is a 4.3% incidence rate of removal of titanium hardware.Conclusion: Data supports that the incidence rate of fixation removal is low. However, incidence was significantin cases where the patient was Caucasian and in cases where the Mandible was operated on. Study is supported byNIH.13